Feeding Strategies in robotic dairies

Robotic milking

Milking is a predictable physical task that can be automatized easily. The milking center is the heart and center of a dairy, and yet labor intensive normally working almost 24-7 year-round. This, coupled with a challenged workforce, makes the milking center one of the most difficult areas to manage in larger dairy farms. In addition, potential communication and cultural barriers can complicate the relationship between dairy owners, managers and employees. For these reasons, robotic milking is becoming popular in dairy farms. It has been reported there are over 35,000 robotic units on farms worldwide.

The University of Minnesota Extension team reported that the top 3 reasons for installing a milking robot were improved lifestyle, reduced hired labor, and the ability to grow without additional hired labor. Along with feeding the cows, cleaning the facilities, and taking care of cow’s health and reproduction, fetching cows is one of the main task in robotic dairies. It has been reported that, on average, 8% of the cows must be fetched to the robots, and dairy workers spent 51 min/day/robot fetching cows.

Performance efficiency in robotic dairies

Three recent studies published in the Journal of Dairy Science evaluated the performance efficiency of automatic milking systems in North American dairy farms. In the first study, researchers from the School of Veterinary Medicine at the University of Wisconsin-Madison surveyed 635 dairy farms with robotic milking located mainly in the Midwest United States (Minnesota and Wisconsin), southern Ontario (between Detroit and Toronto), and lower Quebec (between Ottawa and Quebec City). The researchers (Tremblay et al., 2016) analyzed a data set including 54,065 observations collected from weekly observations over a 4-year period (2011–2014). In summary, average performance was:

• Milk production per cow: 32.7 kg/day
• Cows per robot: 50.5
• Milk production per robot: 1,666 kg/day
• Concentrate consumed in the robot: 5.18 kg/day
• Concentrate refused in the robot: 7.7%
• Milkings per cow: 2.9/day
• Minutes in the robot: 6.8/milking

Similarly, in the second study, Canadian researchers (King et al., 2016) analyzed a data set collected from 41 commercial dairy farms with robotic milking systems (26 Ontario/15 Alberta) from October 2014 to June 2015. These were the average robot and cow performance:

• Milk production per cow: 34.5 kg/day
• Cows per robot: 49.4
• Milk production per robot: 1,685 kg/day
• Milkings per cow: 3.0/day
• Involuntary milkings: 10.4%
• Fetched cows: 8.1%

In the third work conducted by University of Minnesota researchers (Siewert et al., 2018) included 33 dairies located in Minnesota and Wisconsin. These were the production data:

• Milk production per cow: 33.2 kg/day
• Cows per robot: 55.8
• Milk production per robot: 1,861 kg/day
• Concentrate consumed in the robot: 5.01 kg/day
• Concentrate refused in the robot: 0.27 kg/day
• Milkings per cow: 2.8/day
• Minutes in the robot: 7.5/milking

In addition, the authors in this study found that the amount of offered concentrate in the robot was positively associated with daily milk production. They stated that dairies feeding more concentrate generally were obtaining more milk per cow. Considering the results from these three experiments, we can indicate, that, on average, cows in robotic dairies are being milked 2.9 times per day and they are consuming 5.1 kg of concentrate (1.76 kg/visit). Since average milking time in the robot is 7.17 minutes per milking, concentrate eating rate is 0.26 kg/min.

Since cows are fed via a pelleted feed offered in the robot during milking, feeding cows in box robotic dairies is significantly more expensive than feeding a total mix ration (TMR) in conventional farms.

Concentrate supply

A recent survey conducted by University of Minnesota researchers evaluated management factors associated with cow performance in robotic dairies. The survey included 33 dairies located in Minnesota and Wisconsin, and the amount of concentrate offered in the robots averaged 5.01 ± 0.84 kg/cow. The authors (Siewert et al., 2018) found that the amount of concentrate offered in the robot was positively associated with daily milk yield, with farms offering more concentrate generally obtaining more milk production.

It has been suggested that providing a greater quantity of concentrate within the robot increases milking frequency. Three studies conducted in the Rayner Dairy Research and Teaching Facility at the University of Saskatchewan (Saskatoon, SK, Canada) evaluated the effects of the amount of concentrate offered on cow performance, intake and milking activity:

• In the first study, the authors (Hare et al., 2018) fed 2 diets: a high-energy TMR with 0.5 kg of concentrate in a dry matter (DM) basis provided in the robot or a low-energy TMR with 5.0 kg of concentrate consumed in the robot. Total DM intake was 2.7 kg greater for cows fed the high-energy TMR (26.3 kg; 0.5 kg concentrate + 25.7 kg TMR) than the low-energy TMR (23.6 kg; 5.0 kg concentrate + 18.6 kg TMR). Milking frequency was not affected by treatment with cows attending to the robot 3.0 times per day. Although milk production and milk composition were similar, cows receiving less concentrate in the robot gained more weight.
• In the second study, Menajovsky et al. (2018) evaluated the effects of the quantity of concentrate offered (2 vs. 6 kg) in both low- (54% forage) and high-forage diets (64% forage). Cows receiving more concentrate in the robot (6.1 vs. 2.0 kg/day) consumed less TMR in the feedbunk (21.4 vs. 24.9 kg/d); however, in this study total DM intake and milking frequency were not affected by treatment, averaging 27.3 kg/d and 3.6 times/d, respectively. Moreover, milk yield was similar (38.6 kg) regardless of concentrate supply in the robot or forage content in the diet.
• Finally, in the third study the researchers (Paddick et al., 2019) tested 4 concentrate amounts offered in the robot (0.50, 2.00, 3.49, and 4.93 kg of DM/day). Although intake of the TMR decreased linearly as the quantity of concentrate in the robot increased, total DMI intake was not affected by the amount of concentrated allocated in the robot, averaging 25.3 kg/d. Milking frequency (3.2 visits/d), milk yield (37.4 kg/d), milk fat (1.43 kg/d), and milk protein (1.22 kg/d) were not different among treatments.

The results of these works indicate that limiting the allocation of concentrate in the robot box does not affect cow intake, milk yield and milk components production, and voluntary attendance to the robot.

Applications

In conclusion, in robotic dairies, the concentrate should meet the following requirements: 1) be palatable so cows are motivated to enter the robot box; 2) have adequate presentation form (pellet or texturize) to maximize eating rate and reduce refusals, and 3) in combination with the feedbunk ration, it must supply nutrients to guarantee high production of milk and milk components.

by Fernando Diaz

β-galactomannans the multi-target solution against Salmonella

             

Salmonella infection is one of the most common food-borne illnesses in the world. Most human infections are food-borne and are caused by Salmonella Enteritidis and Salmonella Typhimurium.

Mannose- mode of action

Mannose is a monosaccharide with high binding specificity for Fim H adhesins of type I fimbriae on the surface of many Enterobacteria. Fimbriae are used by Enterobacteria to recognise mannose residues on glycoproteins of the intestinal epithelial cell surface. this is how these pathogens adhere to the intestinal wall as a previous and key step to penetrating enterocytes and invading the lymphoid tissue.

        Therefore, the use of mannose rich compounds prevents the bacterial ability to invade by blocking their fimbriae. However, it is not just the contents of mannose, but also the structure of the molecule, what determines the efficacy of these carbohydrates. For this reason, simple mannose monomers have low blocking capacity on bacterial fimbriae, and the resulting levels of intestinal tissue damage are similar to those of untreated animals. On the contrary, oligomannans (small to medium sized carbohydrates containing mannose) have been shown to be very efficient and have prebiotic proroperties which promote the gut flora and the competitive exclusion of pathogens.

            Salmosan is a source of vegetal β-galactomannans obtained after a technological process in which mannose long chains are fragmented by depolymerisation, neutralising thickening properties and maximising it Salmonella-blocking effect.

In Vitro Trials

               The efficacy of β-galactomannans against Salmonella was studied in vitro in different studies with intestinal cell cultures. These studies showed that, in the presence of β-galactomannans at 0.5 μg/mL, the invasion of intestinal cell by Salmonella Typhimurium added to the cell culture (4*10⁶CFU) was inhibited significantly about 60% versus the positive control (Figure 1).  In the presence of β-galactomannan levels of 10 μg/mL, the reduction was above 70%. 

        
      Salmonella remains blocked and is agglutinated by the hydrolysed β-galactomannans (Figure 2). The rugged, spherical structure of the β-galactomannans is seen clearly in this image; this struture facilitates the binding of bacteria to the molecules of mannose. The bacteria blocked by β-galactomannans are excreted in the faeces and have no infective capacity.

                                Figure 2: Electron microscope image of β-galactomannans
                                agglutinating Salmonella in chicken gut tissue.

In vivo Trials

Layers   

     Regarding in vivo efficacy, in a trial with 225 HyLine laying hens, animals were divided into two groups, a group fed with 500 g/ton β-galactomannans, and a control group. Twenty seven days after starting the treatment, animals were challenged with 10⁹ CFU of Salmonella enterica enterica Enteritidis (oral inoculation; 1 mL of suspension). Microbiological examination of caecum in the treated group showed that susceptibility to infection was lower than control baseline (6.3% vs. 25%). In addition, at four months post-inoculation, infected animals in the treated group no longer excreted the pathogens (Figure 3) and their tissues did not appear to be infected. This indicates that β-galactomannans at 500 g/ton are effective for the control of Salmonella in laying hens, reducing the percentage of positive animals.

Broilers
      In an experiment performed with broilers, 800 1-day males were divided into five experimental groups depending on the inclusion level of β-galactomannans in feed (0%, 0.05%, 0.1%, 0.15%, 0.2%), with 16 replicates/group. All of them were doubly inoculated (two consecutive days) with 1 x 10⁶ - 1.5 x 10⁶ CFU of Salmonella enterica enterica Enteritidis.
 
        It was observed that β-galactomannans reduced the isolation of Salmonella Enteritidis from caecum in a dose-dependent manner. With the higher inclusion level, the decrease in bacterial count was nearly three logarithmic units versus infected control (3.49 vs. 6.26) even just 14 days after inoculation (figure 4).

Conclusions:
    β-galactomannans block Enterobacteria such as Salmonella joining to their fimbriae, preventing them from invading the intestinal mucosa.
      β-galactomannans, at 500g/tonne, are effective for the control of Salmonella in laying hens, reducing the percentage of positive animals. In addition, at four months post-inoculation, infected animals in the treated group no longer excreted the pathogen and their tissues did not appear to be infected.
        In broilers, β-galactomannans (2 kg/ton) reduced bacterial counts nearly three logarithmic units versus infected control (3.49 vs. 6.26) even just 14 days after inoculation.
       

Early Breeding of Heifers May be Weighing You Down

                                 Yearling heifers. 

By Maureen Hanson

As an industry, we may need to rethink our strategy in pinpointing the ideal time to breed dairy heifers – again.

It wasn’t long ago that a new approach in breeding dairy heifers was popular. That strategy was to get heifers into the milking string absolutely as soon as possible, so they could stop costing money and start making money.

While well-intentioned and theoretically sound, veterinarian Gavin Staley believes it may have gone too far. Staley is a dairy reproduction specialist for Diamond V, and shared his thoughts on heifer breeding with the audience of the Dairy Calf and Heifer Association’s Annual Conference.

“Yes, it’s possible to get heifers pregnant to calve at 21 months,” said Staley. “But at this age, they would need to have had an average daily gain (ADG) of 2.05 pounds per day from birth to calving, to achieve the physical maturity necessary for optimal pregnancy and lactation.”

What’s really happening, said Staley, is that many herds are bringing heifers into the milking string at 21-22 months, even though they have grown at slower rates. He said heifers with an ADG of 1.81 pounds per day up to calving will not be optimally ready to hit lactation until 24 months of age, and those with ADGs of 1.75 pounds per day should not be calved until 25 months. “We are managing heifers to calve at 21 months and growing them to calve at 24 months,” said Staley. “That’s a serious disconnect.”

When first-lactation heifers calve too young for their physical maturity, they have a higher incidence of calving and transition problems, and need to continue channeling nutritional and metabolic resources to growth versus milk production. One pound of gain per day post-calving comes at a commensurate cost of about 7 pounds of milk per day. Staley said it’s a deficit they never overcome, even in their second and third lactations. “It’s the gift that keeps on giving,” he noted.

The veterinarian has observed evidence of this by examining data from hundreds of herds. In one analysis, he found that later-bred heifers (even just one month) gained 60 pounds more per head before becoming pregnant, and subsequently out-produced their earlier-bred herd mates by 3 to 4 pounds of milk per day in their first lactations.

“Over time, immature heifers become a ball and chain on the entire herd,” he stated. “Older cows are culled because they are pushed out by heifers entering the milking string, and pretty soon you’ve got a whole herd of lifetime underperformers. There is a single number that can be highly predictive of a herd’s average annual milk production, and that’s the 10-week milk production of lactation-1 heifers.”

Ironically, Staley said this phenomenon ultimately punishes the herds that do an excellent job of getting their heifers pregnant. “Good reproductive efficiency and immature animals are a toxic combination,” he declared.

The issue is further compounded by the use of sexed semen, which creates even more young replacements. In some cases, first-lactation heifers make up half or more of a herd’s total population. “It’s like having a bunch of college kids who never graduate,” said Staley. “You just keep paying the tuition, but they never get a salary.”

Staley shared data from one, 3,200-cow herd that delayed its age at first breeding by 40 days, ultimately pushing their first-calving age to about 24 months, instead of 22.5. The results: 7 more pounds of milk per head per day in their first lactations, and a 20% improvement in heifer conception rate. “In addition to achieving higher milk production, they were able to switch to sexed semen as a result of their improved reproductive success,” noted Staley. 

His advice for hitting the “sweet spot” in heifer-breeding maturity includes:

        1. Every dairy needs a scale. Heifers need to be weighed for both breeding readiness, and at freshening. The ultimate target is to freshen heifers at 85% of their mature weight (soon after/at freshening), or 95% of their mature weight at springing (DCC>260), to accommodate the additional weight of the calf and placenta.

        2. Base breeding decisions on weight and frame size, not age. Weight is the easiest factor to measure. The caveat is that heifers must not be overconditioned, as Staley noted it’s easy to make “butterballs.” Frame size – and not just height – is more challenging to evaluate, although new technologies are making it more practical to assess. Age can be used to breed heifers, BUT the dairy must be sure the heifer-raising process is delivering a mature heifer at that age. 

       3. Focus on heifer growth. Know your average daily gain, and use it to determine your ideal age at first breeding. Efforts to save costs in heifer-raising may impede growth and require later breeding ages. 

“Your ultimate goal should be to calve mature animals as early as you can,” advised Staley. “But it’s the lesser of the two evils to delay breeding.”

Efficient feed processing for profitable and safe feed with Kemin’s millSMART programme

By Carmen Coetzee, Product Manager, Kemin Animal Nutrition and Health 

Feed  processing  is  a  complex  operation,  and feed  manufacturers  are  continuously  seeking ways to  improve  efficacy  and  profitability  while ensuring  feed  safety.  This  drives  the  need for  innovation  in  feed  processing  to  meet the  increasing  demands  for  food  of  animal origin,  including  fish,  meat,  milk  and  eggs. The  options  to  improve  feed  manufacturing  are  countless,  and  it  is noted  that  advancements  made  in  feed  processing  are  impacting productivity,  pellet  quality,  feed  safety  and  profitability.  Incorporating sustainable  practices  to  mitigate  the  impact  on  the  environment  has gained  more  focus  over  the  years. Kemin’s  feed  processing  and  feed  safety  programme  with process  optimisation  practices  such  as  millSMART  has  been adopted  in  the  feed  industry  has  gained  attention  due  to  its  beneficial effects  seen  in  productivity,  feed  quality  and  safety.  The  variability of  moisture  in  feed  raw  materials,  in  processing  feed  has  seen to  increase  cost  by  up  to  50%.  Practices  implemented  to  monitor process  fluctuations,  and  reduce  their  variability  brings  benefits  for the  feed  mill  manager  to  ensure  a  uniform  product,  and  quality  of feed is produced, while ensuring safety. Moisture  targets  for  feed  materials  in  the  mixer  are  reached with  the  millSMART  programme.  The  pre-conditioning  solution,  is  a solution  with  a  reduced  surface  tension,  known  as  Opti  CURB  which contains  either  Sal  CURB,  Myco  CURB  or  KEM  WET  products.  The science  behind  the  surfactants  responsible  for  improving  the  preconditioning  solutions  capillarity,  and  therefore  its  movability  within the  feed  matrix,  ensures  uniform  penetration  and  dispersion  of  the solution  throughout  the  batch  of  feed  treated.  Moreover,  feed  safety  is ensured,  as  the  surface-active  solution  contains  either  anti-microbial and  mould  inhibitor  compounds  and  controlling  moulds  and  pathogens is  achieved  by  covering  the  full  surface  area  of  the  feed.  The  Opti CURB  solution  is  added  with  engineering  application  technology  to ensure  maximum  efficacy  in  feed  processing  improvements.  This pre-conditioning  step  ensures  the  feed  particles  are  saturated  and ready  for  steam  conditioning  and  compaction. Pre-conditioning  of  the  mash  feed  in  the  mixer  followed  by  steam conditioning,  has  therefore  formed  a  synergy,  which  ensures  the current  objectives  and  benefits  of  conditioning  are  further  maximised. Saturated  steam  is  applied  to  the  feed  matrix,  with  the  assumption that  the  steam  is  absorbed  fully  and  uniformly.  Technically  this  is  seen in  both  the  transfer  of  moisture  and  heat  into  the  feed  particles  in  the conditioner.  The  speed  at  which  heat,  and  moisture  are  transferred is  different,  this  is  due  to  the  different  behaviours  of  both  and  to the  limited  retention  time  of  the  feed  particles  in  the  conditioner,  as they  pass  through.  Conditioning  is  one  of  the  most  important  steps in  feed  processing.  The  advantages  of  steam  conditioning  are  not only  preparing  feed  for  compaction,  but  ensuring  pathogen  kill-off with  other  effects  seen  on  nutrient  digestibility  improved  due  to starch  gelatinisation,  plasticised  proteins  and  overall  feed  quality. The  cooking  of  these  nutrients  creates  a  type  of  natural  adhesive with  positive  effects  seen  on  the  PDI,  which  is  an  indicator  of  pellet quality  and  how  effectively  that  pellet  will  endure  transport  and handling before final consumption. The  quality  of  steam  is  often  overlooked  or  not  fully  understood in  its  effects  on  compaction  and  the  final  pellet  quality.  Saturated steam  or  dry  steam  versus  wet  steam  and  super-heated  steam  is  the desired  quality  of  steam  required  for  optimum  conditioning  practices. Heat  transfer  for  saturated  steam  is  more  efficient  compared  to  wet steam. During  pelleting,  the  feed  material  is  compacted  to  form  good quality  pellets.  It  is  essential  that  frictional  heat  is  minimised  as  the mash  is  rolled  and  the  newly  formed  pellets  moves  through  the  die holes.  Feed  throughput  and  energy  consumption  are  important  key performance  indicators.  In  the  millSMART  programme,  the  mash feed  matrix  is  well  conditioned,  ensuring  smooth  transfer  through the  pellet  die,  as  feed  particles  are  well  lubricated.  This  reduces  the frictional  heat  generated,  feed  throughput  is  improved,  and  energy consumption is reduced. It  is  essential  as  part  of  feed  hygiene  that  conditioning  and pelleting  temperatures  required  to  kill  pathogenic  moulds  and  bacteria such  as  Salmonella  are  reached.  Depending  on  the  diet  type,  the temperatures  may  exceed  85°C,  or  be  as  low  as  60°C.  Excessive temperatures  may  have  detrimental  effects  on  essential  nutrients or  bioactive  compounds.  Temperatures  which  are  too  high  give  rise to  a  higher  risk  of  condensation  thereafter  and  therefore  a  risk  ofmicrobial  contamination  impacting  feed  safety.  Temperatures  which and  accurately  measuring  all  these  variables  is  the  first  step  to are  too  low  reduce  the  microbial  log  reductions,  and  feed  safety  is at  risk.  Feed  safety  is  a  core  value  in  the  millSMART  programme, ensuring  either  the  antimicrobial  Sal  CURB  or  the  mould  inhibitor Myco  CURB  in  the  Opti  CURB  dispersing  solution  is  added  which kills  upon  contact,  additionally  works  in  synergy  with  heat  treatment to  reach  microbial  kill-off. The  pellets  enter  the  cooler,  with  the  objective  to  effectively cool  the  pellet.  Heat  in  the  pellets  is  lost  due  to  both  evaporation and  convection,  through  the  manipulation  of  both  the  air  fan  speed and  pellet  cooler  retention  time.  If  cooling  is  done  too  quickly  or ineffectively,  an  unstable  poor-quality  pellet  remains,  with  the  risk  of condensation  and  microbial  re-contamination.  If  pellets  are  left  too long  in  the  cooler,  over  cooling  results  in  over  drying  which  is  costly when considering  feed  inventories  and  feed  yield  output.  millSMART is  a  tool  to  effectively  manage  cooling  practices  to  ensure  a  cool pellet with a targeted moisture content achieved. Standardising  feed  processing  is  a  challenge,  due  to  the  impact of  many  variables  affecting  the  productivity  and  quality  of  feed produced.  To  fully  understand  the  effects,  it  is  important  to  trace a  produced  batch  of  feed,  from  the  initial  reception  of  all  the  raw materials  used  to  produce  that  batch  of  feed  through  to  final  loading and  storage  of  the  finished  pelleted  feed.  Variables  impacting  feed processing  are  specific  to  the  location  in  feed  processing.  Identifying understand  their  impact  on  feed  processing  for  what  millSMART  is a useful support. Process  targets  and  key  performance  indicators  are  set  with millSMART  to  ensure  feed  quality  is  reached  during  processing.  The quality  is  essentially  how  much  variation  there  is  around  that  target  or specification.  In  other  words,  reducing  process  variation  is  a  measure of  quality  in  a  feed  operation.  This  can  be  evaluated  starting  at  raw materials  intake,  however  interventions  applied  at  other  steps  such as  in  the  mixer  are  more  commonly  seen.  In  principle,  the  sooner efforts  are  made  to  reduce  variation  in  the  process,  the  more  the optimised  effect  will  be  carried  through  during  subsequent  steps  in feed  processing.  Process  variation  is  minimised  within  a  batch  of feed.  The  variation  between  subsequent  batches  of  feed  produced is  managed  with  process  automation  technologies  such  as  seen  in the  millSMART  online  programme,.  Large  process  fluctuations  are eliminated,  reducing  variability  and  improving  quality  of  process operations and pellets.

        millSMART  online  provides  key benefits  and  insights  for  effective  feed processing,  contributing  to  the  sustainable development  of  feed  operations  and environmental  protection  for  a  happier, more prosperous and healthier world.

MillSMART^TM  improves Feed Mill Efficiency by measuring, analysing and controlling the Efficiency Critical Control Points hence reducing the cost of production of feed while enhancing the pellet quality. During the last two decades of working and partnering with feed mills, we at Kemin have identified eighteen (18) such efficiency critical control points. All these ECCP’s are to be maintained within the standard range to achieve maximum efficiency in feed milling.

        

MillSMART^TM – Three phases for improving feed milling efficiency

1. MillSCAN - In this phase a certified feed mill engineer visits the targeted feed mill and measures various Efficiency Critical Control Points. In this process engineers utilise Kemin’s Customer Laboratory Services to accurately measure the Efficiency Critical Control Points.
2. MillSCORE - Our engineering team utilises various sophisticated tools such as the MillSCORE app to ascertain the current score of the feed mill in terms of its efficiency. Kemin engineering team will make and submit a MillSCORE report comparing all 18 ECCPs against their standard value.
3. MillCONTROL - In this phase, we’ll suggest corrective actions to bring all ECCPs within the standard range. We achieve MillCONTROL by using PPP model: where our People & Product improve the Processes

Improving Starch Gelatinization in Animal Feed

               

What is Starch Gelatinization? 

Starch gelatinization is a process of breaking down the intermolecular bonds of starch molecules in the presence of moisture and heat; both of these conditions are present in conditioner.

What Factors Affect Starch Gelatinization? 

The type of starch can influence its properties for gelatinization. Temperature and moisture are two important pre-requisites for gelatinization of starch. Retention time also plays an important role.

How Can Starch Gelatinization Be Measured? 

There are many methods ranging from turbidity and solubility to magnetic resonance spectroscopy and differential scanning calorimetry.

What is the Benefit of Starch Gelatinization? 

Starch gelatinization has a direct relationship with pellet durability index (PDI) and starch digestibility. The degree of starch gelatinization also influences specific energy and throughput of a pellet mill.

What is the Ideal Starch Gelatinization Value? 

In our internal research, we have found a huge variation in the degree of gelatinization across the Indian sub-continent. It ranges from 10 to 25 percent, which can be attributed to variable processing conditions.

How Can Starch Gelatinization be Improved? 

The degree of starch gelatinization can be enhanced by improving steam quality. Cold mash conditioning using surfactant-based products also helps improve starch gelatinization.

Where Can I Get Starch Gelatinization Analyzed? 

Kemin has developed a method to estimate the degree of starch gelatinization in animal feed. Our method is one of the most accurate methods, as it is based on the enzymatic assay. We are the first one to do so in animal feed sector in India.

Exploring ways to reduce salmonella in poultry

Researchers from 2 US universities have joined forces with the US Department of Agriculture (USDA) to explore alternatives to antibiotics for reducing salmonella in poultry.

Scientists from the University of Georgia and Colorado State University are working with staff at USDA to develop novel techniques , focusing on preventing infection and predicting risk in antibiotic-free production. Each year, Salmonella infects around 1.2 million people and results in economic loses of between $ 2.3 billion and $ 11.3 billion in the United States and its prevalence has remained unchanged for many years.

The research, led by USDA’s Dr Adelumola Oladeinde is concentrating on Salmonella Heidelberg – one of the main strains that causes food-borne outbreaks. The strain is particularly hard to get rid of after colonising broiler farms. “Infections caused by Salmonella Heidelberg are also more invasive than other strains, and Salmonella Heidelberg associated with poultry tends to carry antibiotics resistance and virulence genes. Therefore, it represents a model organism for testing the mechanisms that we have been developing,” he said. The team is focusing its efforts in 2 key areas – examining how the type of poultry litter in broiler houses can prevent infection and development of antibiotic resistance, and devising a flock health monitoring system that can help us to predict infection risk sooner.

Poultry litter: fresh vs recycled

It is fairly common practice in the US for producers to recycle poultry litter over multiple flocks for a year or longer. Dr Oladeinde and his team studied the impact of using fresh or recycled bedding material on the incidence of Salmonella within the flock and its impact on the development of antibiotics resistance – even in the absence of antibiotic use. The team inoculated fresh and reused broiler litter in the lab with different strains of Salmonella and monitored it for 14-21 days. They also carried out experiments with live birds – rearing chickens carrying Salmonella Heidelberg on either fresh or recycled litter. They found that the microbiome present in the reused litter negatively correlated with the populations of antibiotic-resistant Salmonella Heidelberg in the chickens’ guts, compared with broilers raised on fresh litter: “This suggests that reused litter promotes an unfavorable microbiome for Salmonella carrying antibiotic resistance,” he said.

Predicting Salmonella infection in poultry

The team has also been investigating new ways to predict the Salmonella risk within a flock. Wider studies have shown that some beneficial bacteria identified by the team in the microbiomes of birds raised on reused litter, including Bifidobacterium, can alleviate anxiety and depressive-like symptoms in mice and humans, indicating that the gut microbiome can have a positive impact on the brain. It has led them to embark on the development of an automated vision-based Salmonella Predictor, which they hope should be able to identify and locate individual birds with Salmonella infections within the first 2 weeks of life.

Social cues of Salmonella-free broiler chickens

The Predictor will use advanced imaging techniques to collect information on poultry health and social cues associated with Salmonella infection, including behavior traits, bird weight and body temperature. Microbiology and molecular genetics will also be used to determine Salmonella prevalence, virulence and antimicrobial resistance status. Currently in early stage of development, the team are trying to train the system to identify social cues of Salmonella-free broiler chickens raised without antibiotics. Subsequent stages will include testing the Predictor on images of broiler chicks that have been inoculated with Salmonella Heidelberg strains and optimizing the Predictor for a verification test in a commercial broiler house. “If our proposed early prediction tool is successfully developed and adopted by just 5% of US chicken producers, it could reduce the number of Salmonella-carrying chickens at slaughter by 90 million annually. This will significantly improve food safety and reduce the need to recall chickens because of Salmonella contamination,” he added.

Is it safe to Eat Eggs with Blood Spots, Double Yolks or Other Defects?

From the Shell to the appearance of the yolk, here's what those oddities mean and what to do if you find something strange in your next dozen
By Julie Kendrick

Even if you’ve cracked billions of eggs in your life, every once in a while, what emerges from the shell is not like anything you’ve seen before. If you’ve ever noticed a red spot in your egg, you know what we’re talking about. But there’s no need to freak out. It’s probably fine and entirely edible.

Just to reassure you, we talked to a professor emeritus of poultry science and a farmer who wrote the book (well, one of them, anyway) on chicken farming. They explained the mysteries of what exactly is in your egg.

Blood spots

USDA POULTRY PROGRAMS EGG GRADING MANUAL

If you notice a tiny red blood spot on the yolk, you might think you’ve gotten a fertilized egg, but you’d be wrong.

“Blood spots are caused by a tiny tear when the egg yolk releases from a chicken’s ovary,” Michael Darre, professor emeritus of poultry science at the University of Connecticut, told HuffPost.

There’s a good chance you’ve never actually encountered one of these, thanks to improvements in candling, a process that uses a bright light source to show what’s inside the shell. “With highly efficient candling machines, which can process 450 cases of eggs an hour, defects like blood spots rarely get through these days,” Darre said.

Are those red specks safe to eat? The consensus is yes, but feel free to scrape them away with the tip of a knife before you cook them.

Meat spots

 USDA POULTRY PROGRAMS EGG GRADING MANUAL

If you’ve picked up farm-fresh eggs from a local producer, you might notice a brownish or reddish spot floating in the egg. This is a little bit of tissue torn from the chicken as the egg moved through her body.

“It’s considered a ‘flaw’ of the bird, which seems a little unfair, since it was going through her reproductive system,” Lucie Amundsen, co-owner and “marketing chick” at Locally Laid Egg Company and author of a memoir on the egg business, told HuffPost. “They’re fairly rare.”

Like blood spots, they’re safe to eat, or you can nudge them away with a knife and discard them.

Double yolks

Congrats, you won the protein lottery today. A double yolker is a pretty rare occurrence, not only because of modern candling methods, but because they’re typically only produced by chickens in a couple of specific age groups. “You’ll find more double yolks from young pullets or older hens,” Darre said.

If you want to up your odds of getting nature’s version of a prize in the Cracker Jack box, select jumbo eggs, which tend to come from these two chicken age demographics.

   

     USDA POULTRY PROGRAMS EGG GRADING MANUAL

Dark yolk color

It’s a good thing! According to the Egg Nutrition Center, yolk color is dependent on how much carotenoids content is in a hen's diet. Amundsen says that her own experience at Locally Laid confirms that. “In the summer, when our chickens are eating clover in the pasture and lots of juicy bugs, their yolks tend to get very bright,” she said.

She said research has shown that those darker-yolked, pasture-raised eggs are more nutritionally dense than conventional eggs, with less cholesterol and more omega‑3s and beta carotenes.

Shell weirdness

                       

   USDA POULTRY PROGRAMS EGG GRADING MANUAL

Shell color depends on the breed of hen  that laid the egg, and it’s not an indicator of nutritional value. Eggshells can occasionally vary in shape and texture. You probably never see these odd-shaped eggs, Darre said, because they are sent to what’s called “breakers,” which are companies that make liquid pasteurized, freeze-dried or powdered eggs.

"If you have home chickens or you shop at a farm stand, you might see the occasional oddball shape, but they aren’t harmful. And if you notice a sandpapery texture to your egg, those are just calcium deposits that weren’t smoothed away during the laying process".

Maximise use of grazed grass for cost effective milk production

Dairy farmers now, more than ever, must ensure they maximise the use of every square inch of grazed grass to help produce milk at a lower cost.

With excellent summer grass growing conditions being experienced on dairy farms, the forage yields are high, but the utilisation of grazed grass is not as good as it could be.

Results from trials conducted on farm in Northern Ireland by AFBI (Agri-Food and Biosciences Institute) shows that 12.2 tonnes of grass dry matter (DM) per hectare can be grown on average but only 7.5 tonnes is utilised. In order to help farmers maximise the use of grazed grass AFBI has issued some guidelines to try and reduce the cost of milk production.

With excellent summer grass growing conditions, the forage yields are high, but the utilisation of grazed grass is not as good as it could be. Photo: Chris McCullough

Assess grass growth and cover

The ideal pre-grazing grass cover for dairy cows in a rotational grazing system (paddocks or strip-grazing) is 3,000 kg DM/hectare. This is equivalent to a grass height of 8-10cm and can sustain a high level of milk production with good compositional quality. The sward recovery is also quicker than when heavier grass covers are grazed. Paddocks should be grazed down to around 1,600 kg DM/hectare or 4cm.

With grass growth and weather conditions changeable, it is essential farmers walk the grazing platform at least once a week, either by eyeballing or using a plate meter. This is the only sure way to assess the quality and quantity of grass in front of the herd.

Surplus grass can be removed as silage and it is important that this is cut at an early stage even though it is a light crop. This will ensure a leafy regrowth is available for grazing as soon as possible. During periods of grass shortage, cows may be fed additional concentrates or buffer fed silage, until grass is in sufficient supply.

Consider batching cows

In a spread calving pattern herd AFBI urges farmers to consider batching cows using their milk yield as a parameter.

Groups could be:

• Grazing full time - Moderate yielding cows confirmed in calf and late lactation cows.

• Grazing by day and housed at night - Mid lactation cows and those producing up to 30 litres.

• Housed full time, if practised by your particular system - Freshly calved and highest yielding cows.

For block calving cows, in either spring or autumn, the herd can be managed as one block for ease of management either for fulltime grazing or grazed by day and housed at night.

Milk from grassG

Grass is a quarter of the cost of concentrates per kilogram of dry matter (kgDM) therefore it makes sense to increase intake of grazed grass for the dairy herd. High quality Spring grazed grass, if managed correctly, is capable of supporting maintenance plus 20 litres of milk.

To calculate the amount of milk produced from grazed grass for a dairy cow, establish the concentrates fed in kg, divide by 0.45, to give the milk produced from concentrates and then subtract from the total daily milk yield.

For example, a cow producing 35 litres and fed 10kg of concentrates is 10 divided by 0.45 giving 22 litres from concentrates, consequently 35 litres minus 22 litres gives 13 litres from grazed grass. This highlights that this cow is not producing enough from grazed grass and has a higher cost of milk production.

Energy and protein content of diet

Energy, not protein or minerals, is the most limiting nutrient in the dairy cow. If cows are not milking as well as expected, or milk protein is low, or cows are losing excessive condition, energy is the first nutrient to check.

Farmers should check the total dry matter intake of the animal as well as the quality (i.e. energy content) of the concentrates used.

Spring grass has a higher protein content at 20% than average quality silage at 12%, consequently cows should be fed a lower protein concentrate at grass, 15% to 18% protein on a fresh weight basis.

High protein in the diet can result in excessive body weight loss as the cow metabolises the extra protein. Avoid feeding high protein diets during the breeding season to reduce the risk of embryonic loss and poor fertility performance. Dietary protein levels can be monitored through milk urea testing and the optimal is between 20 and 35 mg/100ml.

Lower milk butterfat

In early season, grass is leafy and has a low fibre content and milk butterfat may fall. Cows should be fed a fibre based (sugar beet, soya hulls, citrus pulp) concentrate. This is to reduce the risk of digestive upsets and will help to maintain milk butterfat percentage.

In certain situations it may be necessary to include an acid-buff in the diet to reduce the risk of rumen upsets. As the grazing season progresses, grass quality deteriorates and feeding a cereal based concentrate may be more beneficial.

A minigrazer to help maximise grass utilisation. Photo: Chris McCullough

Managing high grass cover

Even the best grassland managers can have grazing swards which become too long for quality grazing, over 3,000kg DM/ha, therefore farmers need to consider improving grass utilisation.

These options can be used:

• Pre-mowing – weather permitting, cut the grass a day prior to grazing and let the cows pick up the wilted forage from the swathe. Best results are achieved when the grass is cut by a disc mower without a conditioner. This will ensure better grass utilisation and also a high quality regrowth.

• Leader/Follower – this enables higher yielding cows to achieve higher grass intakes and milk yields by allowing the cows to eat the leafy portion of the sward. The stem residue can then be grazed down quickly with other stock, e.g. heifers or dry cows.

• Topping - After the second grazing rotation, paddocks should be topped if there is an accumulation of stemmy material and poor quality grass around dung pats. This will improve the quality of the regrowth and subsequent grazings. Set the topper to cut grass at 5-6cm height. Topping should be carried out immediately after cows are removed from a grazing area as a later topping will check the regrowth. Research has shown that topped swards will improve yield by 1.2 litres/ cow per day in mid to late season, compared to swards that were not topped.

• Alternate grazing & cutting - Cutting all grazing paddocks at least once during the season leaves a clean sward with an even regrowth and may improve grass utilisation and cow performance later in the season.

Flexible grazing management

During periods of wet weather adopt a flexible approach. This may involve on/ off grazing, allowing cows to graze for a few hours after milking and fed silage when housed. The aim being to keep up grass intake, manage swards and avoid damage to grassland.

ANTIBIOTIC RESISTANCE IN FISH FARMING ENVIRONMENTS: A GLOBAL CONCERN

ANTIBIOTIC RESISTANCE IN FISH FARMING: A GLOBAL CONCERN

Antibiotic Resistance in Fish Farming

The occurrence and distribution of antibiotic resistance (AR) phenomena in areas designed for fish Farming has exponentially increased in the last decades. AR bacteria have become a global concern due to the massive use or misuse of antibiotics to prevent possible diseases and overcome major production problems, as confirmed by several research reports. As a consequence of the selective pressure exerted by antibiotics, ARB has been developed and multi-drug resistant bacteria (MDR) have become difficult to be controlled and eradicated. Their spread is expected to increase and is recognized to represent one of the most serious threats to public health in this century. Compared to the past, in salmonid farming in Europe and America, an effective range of vaccines has been developed, which have allowed decreasing the use of antimicrobial agents for most of the bacterial diseases . In addition, the husbandry methods and diagnostic techniques have been improved and this has resulted in a more effective control of bacterial pathogens and reduced impacts of fish diseases. However, for some bacterial diseases, no vaccines are available yet and antimicrobials are still used as a prophylactic measure.

This short note aims at drawing a synthesis of the AR occurrence in aquaculture field and of the possible causes for its spread, suggesting the related legislative measures and the possible solutions to this emerging problem, which has been recognized as a research priority issue by the European Community.

Since the first case studies, several reports have documented the occurrence and spread of ARB in both marine and freshwater fish farms . Most frequently, AR has been reported against oxytetracycline , tetracycline , ampicillin  florfenicol. On the contrary, bacteria resistant to gentamicin, kanamycin, flumequine and enrofloxacin have been reported to account for a low percentage of the total of the isolates.

Fish feed have been claimed to be a source of antimicrobialresistant bacteria. Concerning the mechanisms of AR, two main pathways have been suggested : a) inherent or intrinsic resistance, which occurs when a bacterial species is not normally susceptible to an antibacterial agent, due to the inability of this agent to reach its target site inside the cell, or a lack of affinity between the antibacterial and its target site, or b) acquired resistance, when the bacterial species is normally susceptible to a particular drug, but some strains are resistant and proliferate under the selective pressure induced by the use of that agent. AR genes can be transferred between bacteria by transformation; transduction or conjugation processes that involve lateral DNA transfer. Therefore, bacterial AR is a natural defence mechanism realized through genetic modifications triggered to survive to the drug action and in many conditions, mechanisms of horizontal gene transfer have been reported to be responsible for the spread and dissemination of the genetic material bearing AR among different bacterial species. Even in some aquaculture systems of Pakistan and Tanzania where antibiotics were not previously used ; explained the occurrence of AR against various antimicrobials hypothesizing that a pool of resistance genes derived from integrated fish farming practices based on the use of domestic farm and poultry waste along with antibiotic residues from animal husbandry.

The public health hazards related to antimicrobial use in fish farming include, on one hand, the development and spread of AR bacteria and resistance genes, and on the other, the presence of antimicrobial residues both in the environment and in aquaculture products. Since animals and animal waste are a potential reservoir of multi resistance genes that can be transmitted directly or indirectly to humans through contact and food consumption, this can represent a risk to public health. However, the opinions on the possible risks of transfer of such resistances to human consumers are controversial. Antibiotic-resistant bacteria that persist in sediments and farm environments can act as sources of antibiotic-resistance genes for fish pathogens in the vicinity of the farms.

With respect to the legislative issues of the AR in fish farming, this issue has been recognized as a global concern by the Council and the European Parliament, as well as by the EU Commission. The Regulation (EC) No 470/2009 established the antibiotic maximum residue limits (MRL) in foodstuff of animal origin, taking into account the toxicological risks and the pharmacological effects of residues. The recently launched research programme Horizon 2020, in the framework of the Societal Challenge 3.2 (Food Security, Sustainable Agriculture and Forestry, Marine, Maritime and Inland Water Research and the Bioeconomy), promotes the reduction of antibiotics in animal farming and the setup of measures to prevent their spread, to increase agriculture environmental sustainability. This underlines the relevance of AR in fish farming as a problem with significant scientific, social and economic impacts.

In 2011, a 5-year Action Plan was launched to address the growing risks posed by AR based on a holistic approach; a prudent use of antimicrobial in veterinary medicine was recommended. To comply with this Action, in 2015 specific guidelines have been issued (2015/C 299/04, Commission Notice-Guidelines for the prudent use of antimicrobials in veterinary medicine), with the aim of limiting AR bacteria originated from livestock animals. Among the actions recommended to prevent and reduce the use of antimicrobials in aquaculture, it has been underlined to encourage the use of vaccines, when possible; to implement specific biosecurity measures and to develop specific disease surveillance programmes to prevent or reduce possible disease outbreaks; to develop production systems optimal with respect to water quality, oxygen levels and able to warrant the welfare of the reared animals.

Compared to the studies available until now on the antibiotic use in aquaculture or other farm environments and the presence of AR, relatively few studies focused on the possible solutions to this problem. To implement the appropriate control strategies, a clear evidence of the link between abuse of antibiotics in aquaculture, antibiotic resistance in bacterial pathogens and antibiotic residues is needed. In order to contain and manage the emergence of AR, several solutions can be suggested, that aim at the development of sustainable aquaculture practices, such as those including the use of probiotics, essential oils to increase fish immune status of fish, as well as the adoption of measures able to warrant the fast abatement of antimicrobial residues in animal wastes (The Review on Antimicrobial resistance 2015). Particularly, the use of probiotics to promote health maintenance and disease prevention has recently gained an increasing interest as an alternative to antibiotics. Supplementation with pro- and prebiotics in fish nutrition is increasing in parallel with increasing demand by consumers and with the need for environmentally friendly aquaculture practices. The beneficial effects of probiotics in fish and shellfish culture – improved growth performance, activity of gastrointestinal microbiota and feed utilization, enhanced immunity and disease resistance – have recently been reviewed. Most probiotics proposed as biological control agents in aquaculture belong to the lactic-acid bacteria (LAB), the genus Bacillus, or the genera Pseudomonas and Burkholderia.

Another possible solution to chemotherapies in aquaculture is related to the use of vegetable extracts. Herbal extracts from plants or algae are known to contain natural compounds, such as phenolic compounds, polysaccharides, proteoglycans and flavonoids which are able to stimulate the fish immune system and therefore may play a major role in the prevention or control of infectious microbes.These are recognized as eco-friendly alternatives for therapeutic and prophylactic purposes in health management of aquatic animals, which combine sustainable production systems with high quality of seafood products; nevertheless, further studies are needed to assess any potential impact of these substances on the host microbiota and on the environment.

About the treatment of aquaculture effluents, antibiotic residues should be removed before being released to the environment. Physical, chemical, and biological methods including adsorption, biodegradation, disinfection, membrane separation, hydrolysis, photolysis, and volatilization have been applied in aquaculture systems to remove antibiotics. Tetracyclines are removed mainly by adsorption onto the biomass flocs; beta-lactams by hydrolysis reactions driven by bacteria or physical chemical processes, while removal of erythromycin and ciprofloxacin by biodegradation is difficult. Advanced oxidation processes have been found to be cost-effective mechanisms for the abatement and removal of flumequine from aqueous systems, as conventional processes in wastewater treatment plants fail to remove this antibiotic.

In synthesis, on the basis of the experimental evidences proving the spread of AR, the best way to solve this problem is to avoid abuse antibiotic use in aquaculture. A holistic approach to the use of antibiotics in fish farming is suggested, which relies on reducing the need for antibiotics through prevention (i.e. vaccines), nutrition, and better management of rearing sites.

Source: http://www.fisheriessciences.com/fisheries-aqua/antibiotic-resistance-in-fish-farming-environments-a-globalconcern.php?aid=11240

Heat stress in poultry

                 

What oxidative stress has to do with it, why it affects gut health, and how phytomolecules support mitigation strategies

Stress in animals can be defined as any factor causing disruptions to their homeostasis, their stable internal balance. Stress engenders a biological response to regain equilibrium (1). We can distinguish four major types of stress in the poultry industry: technological or management-related stress; environmental stress; nutritional stress, including due to heavy metals, mycotoxins, and low-quality ingredients; and internal stress, which is related to health status and health challenges. (2). All types of stress lead to molecular and cellular changes that decrease health and productivity.

Climate change, thermoregulation, and stress

High environmental temperatures are among the most important environmental stressors for poultry production, causing significant economic losses in the industry (3). Climate change has increased the prevalence and intensity of heat stress conditions in most poultry production areas all over the world (4, 5).

The optimum temperature for poultry animals’ well-being and performance – the so-called thermoneutral zone – is between 18 and 22°C. When birds are kept within this temperature range, they do not have to spend energy on maintaining constant body temperature (6).

Heat stress is the result of unsuccessful thermoregulation in the animals, as they absorb or produce a higher quantity of heat than they can lose. It means that there is a negative balance between the net amount of energy flowing from the animal to the environment and the energy it produces (7).

HEAT STRESS – CONTRIBUTING FACTORS

This energy imbalance is influenced by environmental factors such as sunlight, thermal irradiation, air temperature, humidity, and stocking density, but also by animal-related factors such as body weight, feather coverage and distribution, dehydration status, metabolic rate, and thermoregulatory mechanisms (7, 8). When the environmental temperature is above the thermoneutral zone, the animals activate thermoregulation mechanisms to lose heat through behavioral, biochemical, and physiological changes and responses (9-12).

Heat stress can be classified into two main categories, acute and chronic. Acute heat stress refers to a short and fast increase in environmental temperature (a few hours), whereas under chronic heat stress the high temperatures persist for more extended periods (several days).  Some studies suggest that, in some circumstances, poultry animals show a degree of resilience to acute heat stress (7, 9, 10). However, in the long run, their compensatory mechanisms are not sufficient to maintain tissue integrity and thus health and performance (11).

The animal’s response to heat stress

The exposure of poultry to heat stress changes the gene expression of cytokines, upregulates heat shock proteins (HSP), and reduces the concentration of thyroid hormones (10, 12). When heat stress persists, these cascades of cellular reactions result in tissue damage and malfunction. The animals exposed to heat stress suffer adverse effects in terms of performance, which are widely known and include high mortality, lower growth and production (Figure 1), and a decline in meat and egg quality (13, 14).

Figure 1 - Body weight gain in heat stressed broilers 

Figure 1: Body weight gain of broilers exposed to chronic heat stress (35°C continuously from day 21). A marker for tight junction permeability was added to feed (FITC-d – fluorescein isothiocyanate dextran); its fluorescence (in serum) increased with heat stress exposure time, showing higher intestinal permeability. (Adapted from Ruff et al., 2020)

OXIDATIVE STRESS – A CONSEQUENCE OF HEAT STRESS

Oxidative stress, simply put, occurs when the amount of reactive oxygen species (ROS – such as superoxide anions, hydrogen peroxide, and hydroxyl radicals) exceeds the antioxidant capacity of the cells (6, 14, 15). Oxidative stress is regarded as one of the most critical stressors in poultry production as it is a response to diverse challenges affecting the animals (2, 17).

At a cellular level, the metabolism of the animal – its energy production – generates ROS and reactive nitrogen species (RNS), such as hydroxyl radicals, superoxide anions, hydrogen peroxide, and nitric oxide. These usually are further processed by antioxidant enzymes produced by the cell (2, 15), including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Nutrients such as selenium and vitamins E, C, and A also participate in antioxidant processes (2, 5). When the generation of ROS exceeds the capacity of the antioxidant system, oxidative stress ensues (2, 16).

Heat stress leads to higher cellular energy demand, promoting the generation of ROS in the mitochondria (13), which exceeds the antioxidant capacity of the organism. Consequently, oxidative stress occurs in several tissues, leading to cell apoptosis or necrosis (11). Among these tissues, the gastrointestinal tract can be highly affected.

Oxidative stress damages cell proteins, lipids, and DNA, and reduces energy generation efficacy (6). Moreover, oxidized molecules can take electrons from other molecules, resulting in a chain reaction. If not controlled, this reaction can cause extensive tissue damage (16).

In response to oxidative stress, all antioxidants in the organism work together to re-establish homeostasis. Several steps in the oxidative stress response have been identified. Whether they take place depends on the intensity of the stressor, with ROS and RNS acting as signaling molecules. These steps include the internal synthesis of antioxidants, the activation of transcription factors or vitagenes, and the production of protective molecules (Figure 2).

Figure 2 - Summary of the antioxidant response

Figure 2: Summary of the antioxidant response

First, decrease free radical production by decreasing oxygen availability and reducing the activities of enzymes responsible for ROS production (NADPH oxidase). Second, scavenge and decompose free radicals through natural antioxidants (vitamins E & C, GSH, SOD, GPx, and CAT). Third, activate Nrf2 and vitagenes to further stimulate the synthesis of antioxidants. Fourth, activate enzymatic systems responsible for damaged molecule repair (HSP, Msr, DNA-repair enzymes) and removal (PH–GPx). Fifth, induce apoptosis and other processes to deal with terminally damaged cells.

(Adapted from Surai et al., 2019)

Oxidative stress’ effects on the gut

In the gastrointestinal tract, oxidative stress and the consequent tissue damage lead to increased intestinal permeability. This facilitates the translocation of toxins and pathogens from the intestinal tract into the bloodstream (Figure 3).

Under oxidative stress conditions in the gut, there is a demand for antioxidants to counteract the excess of ROS; hence, dietary antioxidants can help reduce ROS and improve animal performance (15). Research shows that certain phytomolecules have antioxidant properties and improve performance under conditions of oxidative stress (14, 18-20).

Figure 3

 

Thermoregulation: changes in blood flow

The gastrointestinal tract is profoundly affected by heat stress: to help with heat dissipation, the thermoregulatory mechanism of the animal shifts visceral blood flow towards peripheral circulation. Organ ischemia and hypoxia follow, limiting gut motility, nutrient utilization, and feed intake (5, 14). Enterocytes are particularly sensitive to hypoxia and nutrient restriction, which leads to oxidative stress (2, 12).

Changes in intestinal barrier’s tight junctions

Several studies indicate that both acute and chronic heat stress increase gut permeability, partly by increasing oxidative stress and by disrupting the expression of tight junction proteins (5, 21). Heat and oxidative stress in the gut result in intestinal cell injury and apoptosis. When the tight junction barrier is compromised, luminal substances leak into the bloodstream, which constitutes the condition described as “leaky gut” (4, 21).

Changes in intestinal morphology

Heat stress affects intestinal weight, length, barrier function, and microbiota, resulting in animals that have lower total and relative weight of the small intestine, with shorter jejunum and duodenum, shorter villi (Figure 4), and reduced absorption areas, in comparison to non-stressed animals (11, 12, 23-26).

Figure 4 - Dudenum morphology (villous height and width as % of the control group) in heat-stressed broilers

Figure 4: Villous height and width of broilers exposed to heat stress in relation to the control group (100%). Villous height is always shorter than the control group, but the width can increase when the organism shows resilience to the stressful situations and aims to recover the intestinal surface. (Adapted from Jahejo et al., 2016; Santos et al., 2019; Wu et al., 2018; Abdelqader et al., 2016; Santos et al., 2015 and Awad et al., 2018 – by order of appearance in the graph, from left to right)

Changes in the intestinal microbiome

Due to reduced feed intake and impaired intestinal function, the presence and activity of the commensal microbiota can also be modified. Heat stress can lead to reduced populations of beneficial microbes. At the same time, it can boost the growth of potential pathogens and lead to dysbiosis, increased gut permeability, as well as immune and metabolic dysfunction (27). Burkholder et al. (2008) and Rostagno (2020) point out that pathogens such as Clostridia, Salmonella, and coliform bacteria increase in poultry exposed to heat stress, while the populations of beneficial bacteria such as Lactobacilli and Bifidobacteria decrease.

Necrotic enteritis

Heat stress causes damage in the gut microbiota, intestinal integrity, and villus morphology, as well as immunosuppression. Consequently, feed digestion and absorption decline (11, 12, 28, 29). These factors increase the risk of necrotic enteritis outbreaks (5, 28, 30, 31), one of the most problematic bacterial diseases in modern poultry production.

In a study by Tsiouris et al. (2018), cyclical acute heat stress was found to increase the incidence and severity of necrotic enteritis in broilers challenged with C. perfringens and to produce the disease in animals that were not exposed to the bacteria. Other signs, such as growth retardation and a reduced pH of the intestinal digesta, were also observed in the heat-stressed birds.

By lowering feed digestibility, increasing gut permeability, and compromising immunity, heat stress leaves animals more susceptible to gut-health related issues such as dysbacteriosis and necrotic enteritis – and thus increases the need to use antibiotics.

Mitigation strategies

Most intervention strategies deal with heat stress through a wide range of measures, including environmental management, housing design, ventilation, sprinkling, and shading, amongst others (8). Understanding and controlling environmental conditions is always a part of heat stress management: it is crucial for ensuring animal welfare and achieving successful poultry production.

Feed management and nutrition interventions are also recommended, together with environmental management, to reduce the effects of heat stress. They include feeding pelletized diets with increased energy, higher fat inclusions, reduction of total protein, supplemental amino acids, higher levels of vitamins and minerals, and adjusting the dietary electrolyte balance (1, 12, 18). Nutrition is crucial, and the use of the right diet aids in attenuating heat stress in birds.

Phytomolecules: powerful antioxidants

It is practically impossible to avoid stress in commercial poultry production; hence it is common for animals to experience oxidative stress at times. Phytomolecules are natural antioxidants with anti-inflammatory and digestive properties (8, 14), which have been shown to improve poultry performance, including during challenging periods. The antioxidant capacity of phytomolecules manifests itself in free radical scavenging, increased production of natural antioxidants, and the activation of transcription factors (2, 32, 33).

As compounds that have low bioavailability, they can remain at high concentrations within the intestine, when provided at the appropriate dosage and through encapsulation technology. Research has found that phytomolecules can effectively reduce intestinal ROS and thus alleviate heat stress in poultry (15, 18-20), specifically mitigating oxidative stress in the intestine.

One heat stress study, for example, found that carvacrol elevates serum GSH-PX activity, compared to non-supplemented broilers (19). Other studies demonstrate that cinnamaldehyde also increases the activities of natural antioxidants in heat-stressed broilers (32, 35). A study by Prieto and Campo (2016) showed that dietary supplementation of capsaicin effectively alleviated heat stress, as indicated by a lower H/L ratio in supplemented animals.

Silibinin, a flavonolignan present in silymarin (milk thistle extract), is another powerful antioxidant. In the gastrointestinal tract, it can come into direct contact with cells, activating transcription factors such as Nrf2, and thus helping to upregulate the antioxidant protection (34). Other phytomolecules, such as menthol and cineol, also aid animals under heat stress by simulating the sensory cold receptors of the oral mucosa. This gives them a cooling sensation and reduces heat stress behavior (18).

Summary

Heat stress is a common reality in poultry production, its effects are quite complex and harmful and depend on the intensity and duration of the exposure to high temperatures.

The gut is affected by heat stress through several pathways, including organ ischemia and hypoxia, as well as oxidative stress.

In heat stress challenges, the intestinal barrier is compromised because of lower tight junction protein expression, enterocyte damage, and microbiome unbalance, leading to gut health issues such as dysbiosis and necrotic enteritis.

At the gut level, phytomolecules such as carvacrol, cinnamaldehyde, capsaicin, silymarin, cineol, and menthol, among others, have been found to alleviate heat stress through their antioxidant capacities, leading to improved animal health and performance.

By Marisabel Caballero (Global Technical Manager Poultry – EW Nutrition) & Guillermo Gaona (Regional Technical Manager LATAM – EW Nutrition)