How to control necrotic enteritis through gut health optimization

Antibiotic growth promoters (AGPs) have routinely been used in intensive poultry production for improving birds’ performance. However, in recent years, reducing the use of antibiotics in animal production has become a top priority, due to concerns about the development of antibiotic-resistant bacteria and mounting consumer pressure. Multiple countries have introduced bans or severe restrictions on the non-therapeutic use of antibiotics, including in the US, where the Food and Drug Administration has implemented measures to curb the use of antibiotics since 2017.

However, the removal of AGPs poses challenges for poultry performance, including reduced feed efficiency, decreased daily weight gain, as well as higher mortality. Moreover, the withdrawal of AGPs in feed is widely recognized as one of the predisposing factors for necrotic enteritis (NE). NE is one of the most common and economically important poultry diseases, with an estimated global impact of US$ 5 to 6 billion per year. As a result of withdrawing AGPs, the usage of therapeutic antibiotics to treat NE has increased. To break out of this vicious cycle and to secure the efficiency of poultry production, alternatives are needed that combat NE where it starts: in the gut.

Necrotic enteritis: a complex disease

NE is caused by pathogenic strains of Clostridium perfringens (CP): ubiquitous, gram-positive, spore-forming anaerobic bacteria. The spores of CP can be found in poultry litter, feces, soil, dust, and contaminated feed. Low levels of different CP strains are naturally present in the intestines of healthy birds, kept in check by a balanced microbiome. However, when gut health is compromised, pathogenic strains can proliferate at the expense of unproblematic strains, resulting in clinical or sub-clinical NE.

Animals suffering from the clinical form show symptoms such as general depression, reluctance to move, and diarrhea, with mortality rates of up to 50%. Infected birds suffer from degenerated mucosa lesions in the small intestines. Even in its “mild”, subclinical form, which often goes unnoticed, the damage to the animals’ intestinal mucosa can result in permanently reduced performance and consequent economic losses for the producer.

Certain predisposing factors have been found to enable the proliferation of pathogenic strains in the gastrointestinal tract. Diet is a key example: the composition of the gut flora is directly linked to feed composition. High inclusion rates of cereals (barley, rye, oats, and wheat) that contain high levels of non-starch polysaccharides (NSPs), high levels of indigestible protein, and inclusion of proteins of animal origin (e.g. fishmeal) have been shown to predispose birds to NE.

A range of diseases (e.g. chicken infectious anemia, Gumboro, and Marek’s disease), but also other factors that have immunosuppressive effects, such as heat or cold stress, mycotoxins, feed changes, or high stocking density, render birds more susceptible to intestinal infections. The single most prominent predisposing factor for the occurrence of NE is the mucosal damage caused by coccidiosis.

Gut health is key to combating necrotic enteritis

To control NE, a holistic approach to optimizing the intestinal health of poultry is needed. It should take into account not only parameters such as diet, hygiene, and stress, but should also make use of innovative tools.

Phytomolecules, also known as secondary plant compounds, are essentially plants’ defense mechanisms against pathogens such as moulds, yeasts, and bacteria. Studies have demonstrated the antimicrobial effects of certain phytomolecules, including against antibiotic-resistant pathogens. Phytomolecules have also been found to boost the production of digestive enzymes, to suppress pro-inflammatory prostaglandins and have antioxidant properties. These features make them a potent tool for optimizing gut health, potentially to the point of replacing AGPs.

Can phytomolecules mitigate the impact of necrotic enteritis?

To study the impact of phytomolecules on the performance of broilers challenged with a NE-causing CP strain, a trial was conducted at a US-based research facility. In this 42-day study, 1050 male day-old Cobb 500 broiler chicks were divided into 3 groups, with 7 replicates of 50 chicks each.

On the first day, all animals were vaccinated against coccidiosis through a live oocyst spray vaccination. The experimental diets met or exceeded the National Research Council requirements, and were fed as crumbles/pellets. On days 19, 20, and 21, all pens, except the negative control group, were challenged with a broth culture of C. perfringens. A field isolate of CP known to cause NE (originating from a commercial broiler operation) was utilized as the challenge organism. On day 21, three birds from each pen were selected, sacrificed, group weighed, and examined for the degree of present NE lesions.

The positive control group received no supplements. The trial group received a synergistic combination of two phytogenic products containing standardized amounts of selected, microencapsulated phytomolecules: an in-feed phytogenic premix (Activo®, EW Nutrition GmbH) and a liquid complementary feed supplied via the drinking water (Activo® Liquid, EW Nutrition GmbH). The products were given at inclusion rates corresponding to the manufacturer’s baseline antibiotic reduction program recommendations (Figure 1):

Figure 1: Trial design

The trial results indicate that the addition of phytomolecules helps to mitigate the impact of NE on broilers’ performance. The group receiving Activo® and Activo® Liquid showed a better feed conversion (Figure 2) compared to the positive control group (NE challenge, no supplement). Also, better lesion scores were noted for animals receiving phytomolecules (0.7 and 1) than for the positive control group (1.6).

The most significant effect was observed concerning mortality: the group receiving Activo® and Activo® Liquid showed a 50% lower mortality rate than the positive control group (Figure 3). These results clearly indicate that phytomolecules can play an important role in mitigating losses due to NE.

Figure 1: Adjusted FCR

Figure 2: Lesion scores and mortality

Tackling necrotic enteritis in a sustainable way

In an age of AGP-free poultry production, a concerted focus on fostering animals’ gut health is key to achieving optimal performance. This study strongly demonstrates that, thanks to their antimicrobial, digestive, anti-inflammatory and antioxidant properties, phytomolecules effectively support birds’ intestinal health when challenged with NE. The inclusion of Activo® and Activo® Liquid, two phytogenic products designed to synergistically support birds during critical periods, resulted in improved feed conversion, better lesion scores, and 50% lower mortality.

In combination with good dietary, hygiene, and management practices, phytomolecules are therefore a potent tool for reducing the use of antibiotics: including Activo® and Activo® Liquid in their animals’ diets allows poultry producers to reduce the incidence of NE, to mitigate its economic impact in case of outbreaks, and therefore to control NE in a sustainable way.

By A. Bhoyar, T. van Gerwe and S. Regragui Mazili

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.”