Estrus, its detection and artificial insemination

The Estrus cycle can be divided into 4 stages:

 

Proestrus Phase:

     About 16 to 18 days after a heat period under the influence of GnRH the pituitary produce FSH this is released into the blood stream. FSH causes development of follicle of ovary. The follicle in turn over a 3 to 5 days period produces estrogen as it grows in size. Estrogen level peaks at 19 to 20 days. Estrogen causes following changes in cow.

 

Physical:        

•  Increase of blood lining of the uterus
• Thickening of wall of vagina
• Increase growth of cell and cilia in oviduct
• Relaxation of cervix
• Mucus production by cells of cervix
• Mucus is usually thick and milky in color
• Decline of previous CL on ovary

Behavioral:   

• Late in this period, the female animal usually exhibits interest in the male

 

Hormonal:

• High estrogen level cause production of LH about day 20.

 

Estrus Phase:

     FSH and LH affect the ovary to stimulate follicle rupture and release of the egg contained within. Physically this period is characterized by sexual desire and acceptance of male. Estrogen continues to dominate the reproductive tract and produce the following changes.

 

Physical:

•  Engorgement of the uterus wall
•  Contraction of oviduct
•  Relaxation of cervix
•  Mucus secretion is clear, transparent and stringy
• Vulva is swollen and relaxed
• Ovulation occurs after 12 hours after the end of this period

Behavioral:

• Effects of estrogen of CNS produce the characteristic behavioral pattern of reception of male

 

Met estrus phase:

         This stage last for 3 to 4 days, the same length of time it takes the ova to reach the uterus. The egg is picked up by the oviduct, and the follicle collapses. LH causes the production of a new cell type, the luteal cell in the ruptured cell, in the ruptured follicle. This gives rise 1^st to the Corpus hemorrhagicum where the blood invades the follicular space and then the Corpus luteum which produces progesterone which changes the state of reproductive tract.

Progesterone prevents the FSH secretion and therefore prevents the further development of follicles.

Physical Change:

• Blood discharge occurs about 2 days after estrous in 50 to 80% of all cows. This blood does not indicate ovulation or success or failure of the breeding; but, it indicates some hemorrhage of the uterus lining
•  Mucus secretions decrease
• The uterus becomes soft, pliable and relaxed
• Uterus wall grows thicker in preparation for pregnancy
•  Cervix begins to close

 Diestrus Phase:

     This is the longest period in the estrus cycle, generally lasting from day 4 to 18

The Corpus luteum matures and produces progesterone with the influence of reproductive tract.

Physical Change:

• Thickening of uterine lining
• Cervix closes
• Vaginal mucus is scant and sticky
•  Uterus muscles are relaxed

        If the egg is not fertilized in the oviduct, the CL grows for 10 to 12 days. If no embryo is present, high progesterone level causes production of PGF 2a. Prostaglandin influences the ovary and causes degeneration of CL and therefore, a decrease in progesterone. This leads to FSH production and re entry into the proestrus phase with the development of a new follicle. This normal cyclic activity repeats itself

        If the egg is fertilized, the CL body continues to produce progesterone. The recognition of an embryo by the dam blocks the release of PGF2a. Progesterone relaxes the uterine muscle and encourages growth of uterine lining to nourish the fertilized egg. Progesterone production by the CL is important for maintainace of pregnancy during the 1^st 2/3 of gestation. After that progesterone is produced by the cells of the placenta and adrenal glands.

  

STAGES LEADING TO FERTILIZATION:

1.  Ovulation and insemination
2. Transport of ova and sperm
3. Capacitation of sperm
4. Activation of egg
5. Formation of zygote

1: Ovulation and Insemination:

       Towards the end of the estrus period, the cow becomes receptive to the male. The follicle ruptures and the ova or egg travels into the oviduct or fallopian tube. In natural services sperm is deposited in the anterior vagina next to the cervix. In artificial insemination, the sperm is deposited within the cervix or just inside the uterus.

 

2: Transport of Ova and Sperm:

    The hormonal changes of the estrus cycle are very important in changing of the reproductive environment to facilitate ova and sperm transport. The oviduct experience contractions. Hair like cilia on the inside the oviduct creates waves in the oviduct fluid and assist in ova transport.

The sperm moves rapidly through the uterus to the upper 1/3 of the oviduct where fertilization occurs

The egg is fertile for approximately 10 to 12 hours. If fertilization occurs after this time, an abnormal embryo results. This may lead to and early embryonic death or early abortion

 3: Capacitation of Sperm:

For fertilization to occur, a process known as capacitation must 1^st occurs. Cpacitation refers to the functional change in the head of the sperm which then allows it to penetrate the cells of the ova

4: Activation of Egg:

Once the sperm has penetrated the egg, a reaction occurs preventing penetration of further sperm. Male and female pro nuclei form, a mixing of the chromosomes occurs and the union forms the zygote

5: Fertilization:

Once the fertilized ova has formed the cells within divide. The ova goes through 2/4/8/16/32 cell stages. Fertilized ova usually enter the uterus from the oviduct, about 4 days after estrus.

 Important times to remember:

• Fertile life of egg is 10 to 12 hour after ovulation
• Time required for capacitation of sperm is 4 to 6 hours
• Life time of sperm is 24 hours
• Transit of fertilized ova from oviduct to uterus is day 4
• If insemination occurs too early, the sperm may have died prior to ovulation
• If insemination occurs too late the ova has passed its fertile life period before the sperm gains the ability to fertile the egg
• In general cows noticed in heat in the morning should be bred later the same day. Cows noticed in heat in the after noon should be bred next morning

 

 Physiology of female reproductive Organs:

 

1: Reproduction, Sexual maturity and breed maturity:

    Puberty is the period of a cow’s life when it is able to release ova and to manifest complete sexual behavior sequence. Puberty is basically the result of a gradual adjustment between increasing sexual hormonal activities from the pituitary and the ovaries.

    At puberty in heifers there is an increase in ovarian size due the presence of follicle. This is associated with the ability of follicles to ovulate as a consequence of LH peak, a hormone secreted by pituitary for ovulation. The time of onset of this activity appears to be a function more of the weight than age of the animal. Restricted nutrition delays puberty in cattle.

    Dairy cattle reach puberty when its body weight is 30 to 40% that of their adult weight whereas in beef cattle this percentage is higher. Generally speaking in normal conditions, puberty occurs between 300 to 360 days of age in dairy cattle and between 320-460 days of age for beef breeds.

2: Sexual or Heat cycle:

The estrus cycle is divided into four arbitrary stages:

• Proestrus
• Estrus
• Metestrus
• Diestrus

Each stage is controlled by reproductive hormones produced by the nervous system and by ovaries and uterus.

3: Cycles of Ovary

    Oogenesis is defined as formation of primordial follicle. The ovary of a newborn calf contains several hundred and thousands oocytes. Only a small percentage is ovulated during the life. The primordial follicle forms preovulatory Graffialn follicle. The mature follicle extends through thickness and protrudes above the ovarian surface like a blister.

The active follicle produces the hormones called estrogen mainly responsible for estrus signs

    Ovulation is the rupture of the Graffian follicle and release of mature oocyst. The oocyst is then called ovum. Present evidence shows that high level of LH stimulates the plasminogin and collaginase in the follicular wall that will participate in the digestion of intercellular connective tissue. This will result in release of the ovum.

After ovulation the follicular cavity fills with blood forming a corpus hemorrhagicum. The granuloseand thical cells enlarge to fill the follicular cavity. The corpus luteum is highly vascularized. This process is called lutinization. CL produces progesterone that inhibits estrus behavior.

4: Cycles of the Uterus:

During the follicular phase of estrus cycle, the vascularity of the uterus is increased due to estrogenic stimulation. The uterus becomes engorged with blood, especially in the carouncular area. It is firm and turgid

At this stage the mucus cells of the cervix are stimulated and thin watery mucus is discharged from the cervix and expelled from the vagina. The glands in the vagina are also stimulated to secrete mucus. The increase in blood circulation in vaginal wall will induce slight edema.

 5: The Oestrual Cycle:

In cows the estrus cycle lasts 20 to 21 days. An open cow will continue to start a new reproductive cycle until it is bred and become pregnant. Cycle can range in length from 18 to 24 days. The cycle can be divided into 2 phases

• Follicular
• Luteal

The 1^st day a cow is in heat is called day zero of the cycle. The follicular phase is ended by the ovulation of a mature oocyst. After ovulation follicular cell are transformed into the CL. This is the beginning of the luteal phase. The end of the luteal phase begins with luteolysis, the destruction of CL to allow rapid growth of the new ovulatory follicle

 6: Hormones of Reproduction:

    Hormones are chemical agent synthesized and secreted by specialized glands and carried by the blood to other parts of the body where they act on specific tissues or organs

In cow reproduction we are primarily concerned with three different types of hormones.

• Releasing hormones
• Gonadotropic hormones
• Sex steroid hormones

     Releasing hormones originate from the hypothalamus and control the synthesis and release of hormone from the anterior portion of the pituitary gland. The hypothalamus is part of the brain.

    The gonadotropic hormones produced in the pituitary are directly involved in maturation and release of ova. They also stimulate the secretion of sex steroids hormones from the ovary. The pituitary gland is located in a pocket beneath the brain to which it is connected by the pedicle of nervous and blood vessels.

    The sex steroid hormones are involved in the behavioral aspects of reproduction, in development and maintainace of secondary sex characteristics in maintainace of reproductive organs and in regulation of reproductive cycle and pregnancy.

HORMONE	ORIGIN	FUNCTION
GnRH	Hypothalamus	Stimulation and release of FSH and LH
FSH	Pituitary gland	Follicular growth and production
LH	Pituitary gland	Final maturation of follicle, ovulation, CL formation
Estrogen	Ovary (Follicle)	Growth of uterus , estrus behavior, cervical mucus secretion, release of LH for ovulation
Progesterone	Ovary (CL)	Maintains pregnancy, keeps cow from cycling
Oxytocin	Ovary (CL), Pituitary	Milk excretion and prostaglandin synthesis
PGF2A	Uterus	Lysis of CL

 

7: Control of Sexual Cycle:

     GnRH from hypothalamus cuase release of FSH from the pituitary gland. The FSH reaches the ovaries by blood circulation and stimulates the development of follicles.

    The follicles in the ovaries produce esterdiol which brings the cow in estrus. One follicle produces more esterdiol than the others on the ovaries and grows more rapidly.

T    he level of esterdiol in the blood rises causing a greater discharge of GnRH by the hypothalamus. The pituitary then release less FSH. The level of esterdiol causes the pituitary gland to secrete a massive discharge of LH in response to frequent stimulation by GnRH. This provokes around 36 hours after the LH spike, the final maturation of the follicle which ruptures to expel the ova. Under the stimulates of LH the follicle cell transform into luteal cells to form CL. The CL progressively produces progesterone. CL reaches at its maximum size at day 11-13.

If pregnancy does not occur at day 16-17 CL begins to regress due to production of oxytocin produced by the CL cells and the luteolytic PGF2a secreted by the uterus.

If pregnancy occurs the CL remains and continues to produce progesterone until the birth of the calf.

 

PRIMARY EXAMINATIONS

1: Pre-Insemination checks:

• Restrain the cow or heifer but do not tie down or over excite
• Identify the cow to be inseminated.
• Approach the cow slowly, talk to her, do not rush, do nothing to excite her

Check for previous services and in case of repeats, note observations such as late repeats over 23 days, early and quick repeats less than 17 days and watch for possible pregnancy

 

 2: Heat Signs:

	Coming into heat	Standing heat	Going out of heat
Appetite	Noticeable decrease	Sharp decrease	Slowly returning
Nervous behavior	Very noticeable	Very noticeable	Noticeable
Fence walking	Very noticeable	Very noticeable	Noticeable
Bawling	Frequent	Less frequent	Frequent
Persistent trailing of other animal	Yes	Yes	Very little
Temperament towards other animal	Very antagonistic	Less antagonistic	Back to normal
Head butting	Quite frequent	less frequent	Frequent
Licking other animal	Yes	Yes	Yes
Mounting behavior	Will jump others but will not stand to be ridden	Will jump on others and will stand to be ridden	May jump others but not stand to be ridden
Response to observe	Cautions	Interested	Shy, avoid
Mucus present	Occasionally	May occur frequent	More frequent
Mucus consistency	Watery	Cohesive strand	Cohesive strands
Vulva	Red and puffy	Red and puffy	Less swollen
Bloody discharge	Not usual	Not usual	May present

 

3: General conditions of the Animal:

• Cow should be in good physical condition. Cows gaining body weight conceive better than cows in a weight loss condition
• Observe for abnormal discharge from vulva. They are signs of infections and need to be treated before breeding
• Observe for bloody discharge. It may be to late to bred       

 

4: Insemination Procedure:

All insemination equipments and supplies must be clean and sanitary. Use disposable equipments only once. Be extremely careful when handling the insemination gun, sheath and straw of semen to keep them clean and free from contamination

Summary in points form describing the step by step procedure eh inseminating the cow:

1. Have a thawing thermos prepared with the proper temperature of water, 37C
2. Place insemination kit close to liquid nitrogen semen tanks.
3. In case of repeats, note if the animal in question is a late repeat or is she early or quick repeat. Watch for possible signs of pregnancy when examining the cow prior to insemination.
4. Remove the lid and place it in a clean area
5. Prior to lifting any conister from your liquid nitrogen tank, assure yourself of the semen location
6. Lift conister high enough to reach the cane containing the dose of semen. Be assure not to lift the consiter above the frost line in the neck of your tank
7. Identify and remove dose as quickly as possible from the tank. The recommended time is between 15 to 1 minutes
8. In order to reduce the chance of straw exploding after they were removed from the nitrogen tank, immediately and without hesitation shake the straw in a short swing movement similar to that of nurse shaking thermometer. This will remove small drops of nitrogen which may be trapped at one end of the straw. The plug is needed to expel the semen form the straw
9. After this now load the gun properly
10. Approach the cow slowly and gently and talk to her
11. Lubricate your gloved hand with mineral oil; rub gently the anal area of the cow. This will relax the animal and make the entry of your hand into the rectum easier
12. With your four finger and thumb, a wedge is formed which in turn slowly and firmly pushed into the rectum of the cow
13. Gently massage the rectum and examine the reproductive organ. Note the abnormalities
14. Pull your hand back towards vulva. Now you are in position to clean the vulva with the clean, dry paper towel. Do this 2 to 3 times if necessary. Use a new towel each time. Remove as much manure as you can.
15. Now gently aside the vulvular lips for clean entry. The inseminator should not touch the outer lips of vulva while he is carefully inserting the insemination device into the vagina
16. Be sure to insert the insemination device into the vagina at a 45 angle to avoid entry into urethral opening
17. After the insemination device has been manipulated into the body of uterus the semen may now expelled from the insemination device. Push the plunger very slowly. It is advisable to count backwards from 10 to zero.
18. In order to prevent injury to the reproductive tract remove the insemination instrument very slowly
19. Remove arm form rectum slowly
20. Dispose the dirty glove and sheath
21. Before going to next case make sure your equipment is clean and free from manure
22. It is a good practice to remove all of your equipments from your kit and clean it thoroughly once a week

Thawing Frozen Semen:

Since the discovery of frozen semen technique by Dr. Chris Polge in 1949, thawing procedure for frozen semen has changed dramatically since that time.

The volume of semen dose for each insemination has also been changed from origin 1 ml ampoule to the present 0.5 and 0.25 ml straws. The volume and surface relationship of each packaging system influences the thawing rate of spermatozoa.

Following are the most commonly used semen packages system throughout the world.

1. 1 ml ampoule
2. 0.5 ml
3. 0.25 ml ampoule

Insemination Technique:

• One should pay special attention that 1/3 of the insemination device which is entering the animal be clean.
• Injuring the animal with the insemination pipette can cause failure of conception
• An injury to mucus membrane can cause bleeding. This blood is harmful to semen, and fertilization may not occur, because the sperm cells agglutinate. Even if the fertilization has taken place the fertilized embryo may be unable to implant in the lining of uterus causing an early embryonic death.
• In order to prevent the injury to the rectum of the animal the inseminator should have great care to always trim the nail.

 

Most common error during insemination

Fundamentals when using semen stored in the liquid nitrogen. The development and use of frozen semen stored in the liquid nitrogen and especially the reduction of semen packages to 0.5 to 0.25 ml respectively requires special training and careful handling of these packages

The operator must e precise and gentle as well as technically competent to introduce the semen into the animal. The insemination equipments for the straw should be thin and rigid. The insemination should not be performed roughly.

Errors when animal are not restrained:

A high degree of injury to the rectum of the reproductive tract can occur

And exact, careful and smooth introduction of the insemination equipments is difficult

Inseminator is at great risk of injury

Deficient Hygiene:

 

1: Rough and Uncontrolled Insemination technique:

Injuring the animal with the insemination pipette can cause failure of conception

An injury to mucus membrane can cause bleeding. This blood is harmful to semen, and fertilization may not occur, because the sperm cells agglutinate. Even if the fertilization has taken place the fertilized embryo may be unable to implant in the lining of uterus causing an early embryonic death.

2: Intra cervical insemination:

This method should be used only when a cow is not showing clear and distant signs of estrus.  It is also advisable to use intracervical semen deposition if a chance of pregnancy exists. If the tip of the insemination rod is passed through the cervix into the uterus the animal may abort.

3: Deep intrauterine Deposit:

This type of insemination is to be avoided. This can cause injury to delicate uterine membrane with instruments. It is seen that deposition in the uterine body is considerably superior that other depositions

 

 

UVAS one of the Best University in the World

 

About University

With a marvelous history of 137years of excellence, the University of Veterinary & Animal Sciences (UVAS), Lahore is now positioned among top ten Universities of Pakistan. Originally established as a school in 1882, it was later transformed into a College within next two decades, i.e. end of nineteenth century. Realizing the importance of livestock and poultry sectors in the economy of the county and growing need of human resource and research work in veterinary & animal sciences and allied fields in the country, this historic institution was upgraded as University in 2002. Presently, UVAS comprises of 23 departments in five faculties, four institutes, two constituent colleges along with seven affiliated institutes at Attock, Rawalpindi, Shiekhupura, Okara, Lahore, Narowal and Sahiwal. The UVAS reflects a unique blend of glorious history and ongoing professional advancement of the modern era. The main building of the institution, that was built 100 years ago, is still considered as the symbol of historical glory while the University has now expanded to six campuses, including its City Campus Lahore, Ravi Campus Pattoki, Avian Research & Training Center at Ferozepur Road, College of Veterinary & Animal Sciences Jhang, KBCMA College of Veterinary and Animal Sciences Narowal and the Para Veterinary Institute in Karor Lal Easin, District Layyah.

With a motto "Provoking Potentials, Producing Professionals", UVAS has fast moved towards multi-level education and skills development institution by utilizing its knowledge, resources and skills for human resource development. In the recent years, UVAS has emerged as a hub of professional advancement in wide ranging areas including veterinary & animal sciences, animal production & technology, biotechnology, microbiology, pharmaceutical sciences, food sciences, environmental sciences, zoological sciences, economics & business management, etc. With over 332 faculty members including 186 Ph.D., UVAS offers 26 undergraduate, 30 M.Phil. and 23 Ph.D. degree programs in aforementioned areas along with 3 diploma courses and a number of need based short trainings and certificate courses for capacity building of the human resource in these fields. Presently, about 8,000 students are studying in various disciplines in the University.

Equipped with state of the art teaching, training, research, clinical and diagnostic facilities, UVAS demonstrates professional excellence in multidimensional focus areas of academics, research and services. Through its partnership with various foreign and local academic & research institutions and private sector, the University plays a pivotal role in economic development through applied research. Presently UVAS scientists are managing 144 research projects of economic significance worth Rs. 1545.81 Million in various fields. UVAS offers wide ranging services, to farmers, pet owners, community members and industry stakeholders, including diagnostics facilities, clinical & extension services, vaccine production, consultancy & advisory services, regulations & policy framework etc.

Sheep Breeds of Pakistan

 

There is local 30 breeds of sheep in Pakistan. The most famous breeds of sheep province wise are “Buchi, Lohi, Thalli and Salt range in Punjab; Bumbi, Kachhi and Kooka in Sindh; Balkhi, Damani and Kaghani in KPK; Balochi, Bibrik, Harnai and Rakhshani in Baluchistan; Baltistani, Gojal, Kail, Kali, Koh-i-Ghizer, Pahari and poonchi in Gilgit, FATA and AJK.”

Balochistan breeds:

Balochi Breed:

It is the member of fat tailed family. It is also known as Balochi Dumda, Taraki, Mengali, Shinwari, Araghi, kirmani Neini normally present in the area of Quetta and Sibi. It is raised for meat and wool purpose. Its average weight is 38kg in male and 32kg in female. Its average fleece weight per year is 2.25kg.

 

 

Bibrik Breed:

            Fat tailed family breed mainly raised for meat purpose. It is normally present in the district of Sibi and Loralai. It has horns and white color in body and black/brown head. Its average weight is 37kg in ram and 32 in ewe. Its average fleece weight per year is 1.55kg.

 

 

Harnai Breed:

            Harnai is fat tailed, meat/wool type breed. It is found in districts of Sibi, Loralai, Zhob and Quetta. The average weigh of Harnai is 34kg of ram and 33kg of ewe with average wool production per year is 2.6kg. It is white in color with dark tan spotted head and ears.

 

 

Gilgit, FATA &AJK Breeds:

Data not available: (if anyone have the details of these breed).

 

 

KPK Breeds:

Balkhi:

Balkhi is fat tail, meat type sheep of tribal areas of KPK. The average weight of ram is 70kg and 54kg of ewe. Its color is black, tan or grey, both sexes have horn.

 

 

Damani:

Damani is thin tail, meat and wool type breed of Banu and Dear Ismail Khan districts. The mature ram has average weight of 32kg and ewe has 27kg. The average wool production per year is 1.5kg. It is white in color with black or tan head and camel colored legs.

 

 

Kaghani:

Kaghani is a meat type breed found in Hazara division and surrounding areas of KPK. Its color is white, gray, black or brown body coat.

 

Punjab Breeds:

Buchi:

Buchi is meat and wool type breed found in the areas of Cholistan, Bahwalpur, Bahwalnagr, Rahim Yar Khan and Muzaffargarh. It has prominent eyes and “small and stubby ears due which it is known as Buchi.” Buchi sheep has compact body with white color coat, some sheep have black spots on the body and some have complete black color. Its average body weight for ram is 35kg and ewe 30kg. Its average wool production per year is 4kg.

 

Lohi:

Lohi is meat and wool type sheep also known as Parkanni and Lamochar. It is normally found in the area of Lahore, Faisalabad, Sheikhopura, Gujranwala, Toba Tek Sing, Sahiwal and jahng. It has Roman noses, long ears, pendulous with an appendage on external side known as “Perkann.” Its average weigh in Ram is 65kg and 50kg in ewe. Its average wool production per year is 3kg.

 

 

Kajli:

Kajli sheep is meat and wool type breed of Punjab. The home tract of kali sheep is Sargodha, Khushab, Mianwali and Gujrat area. It has white color body with black color upper lip, 1/3 part of ear and circles around eyes. Due this black color circle around eyes is known as Kajli. The average weight of ram is 55kg and 45kg in ewe. Average wool production per year is 3kg.

 

 

Lati (Salt Range):

Lati is meat and wool type breed of Punjab. The origin of Lati sheep is from area of Salt range districtof Rawalpindi, Jehlum, Mianwali, Sargodha and Attock. This is the only fat tail breed of Punjab. It has white color body, tan brown small head. Forehead is broad and muzzle are tapering. Average weight of ram is 36kg and 28kg of ewe. Average wool production per year is 1.5kg.

 

 

Sindhi Breeds:

Bumbi:

Bumbi is the meat type breed of Sind. The origin of Bumbi/Dumbi is Dadu, Shahdad kot and Jacobabad area. Its average body weight is 40kg of ram and 30kg of ewe. Its average wool production per year is 1.3kg.

 

 

Kachi:

Kachi is meat, milk and wool type breed of Sindh. The home tract of Kachi is Dadu, Shahdad Kot, Jacobabad, Hyderabad, Larkana and Nawabshah. Its average body weight is 40kg of ram and 30 kg of ewe. Average milk and wool production is 1.09 liter/day and 2.08kg per year.

 

 

 

Kooka:

Kooka is meat and wool type breed of Sindh. It is normally found in the district of Tharparkar and other desert areas of Sindh. It has white color coat and black color of head and legs. Its average body weight is 30kg of ram and 26kg of ewe. Average fleece production per year is 2.13 kg.

Adjustment of enzyme level in feed to provide the adequate nutrition in starter diet of chicken

by Dr. N.E. Ward, M. de Beer

At hatch, the chick is not adequately prepared to efficiently digest feed. This, plus the changing levels and composition of NSPs over the production period, necessitates an adjustment in enzyme supplementation.

Poultry nutritionists are challenged with providing proper nutrition to the immature intestinal system of the chick during the starter phase. In the days following hatch, the young bird is physiologically limited in the amount of energy, amino acids and other nutritional attributes it can obtain from high-quality feeds (Batal and Parsons, 2002).

Non-starch polysaccharides (NSPs) complicate this process by encumbering nutrients and interfering with digestibility. This is more problematic at an early age, in part because the effects imposed by NSPs are more pronounced in younger chicks.

Still, suboptimal digestibility can be the consequence beyond intestinal immaturity or the presence of NSPs. Poor quality ingredients, disease conditions, starch overloading and other factors can tax feed costs.

Of course, early growth is vital for subsequent performance and meat yield (Ross, 2009). Satellite cells — remarkably dependent on early nutrition — set the stage for muscle development in the mature bird (Halevy et al., 2003).

Cell formation is rapid and transient in the first days of life, and suboptimal nutrition at this age can pervert lifetime performance and limit meat yield (Noy and Sklan, 1999; Halevy et al., 2001).

Substrate accessibility

Carbohydrases, proteases and phytases can potentially resolve some digestibility issues and improve substrate utilization (Adeola and Cowieson, 2011). Many nutritionists use multiple enzymes but often are unsure of the proper combination and how to best account for their value when using least-cost formulation software.
Carbohydrases for NSPs are important because of their contribution to metabolizable energy (ME) — the primary driver for feed costs.

The soluble NSPs associated with wet litter, pasty vents and other performance issues in wheat- and barley-based diets are visibly responsive to xylanases and glucanases. Compared to these grains, however, corn/soybean meal-based diets are far more reticent to carbohydrases (Cowieson, 2010; Slominski, 2011). Corn contains similar amounts of NSPs as wheat, yet nutritional inefficiencies are vague because performance constraints are less conspicuous with corn.

The effectiveness of carbohydrases is greatly affected by NSP accessibility, or the physical proximity of the enzyme to NSP. By sequentially fractionating cell walls in soybean meal to expose NSP components, Ouhida et al. (2001) and others have reported significant increases in enzymatic NSP degradation relative to the intact cell wall.

Reviewed earlier (Feedstuffs, Jan. 27), the NSP in any grain is a complicated composite of different chemical structures and bonds that overlap and intertwine. The sheer density of the cell wall matrix can hinder enzyme penetration to the inner core; thus, systematic degradation by several enzymes is a prudent strategy. Pure cloned enzymes with one major activity may not effectively degrade NSPs in soybean meal or cereals, and the exposure of NSP components simply favors degradation (Huisman et al., 1999).

Broad enzyme selection

Grinding, conditioning and pelleting improves NSP exposure to enzymes, as does gizzard action. Solubility of NSPs, the presence of side chains and the complexity of various types of NSP fiber from different ingredients make the selection of the enzyme mix critical.

In poultry trials with xylanase or glucanase or a combination of protease, amylase and xylanase, Slominski (2011) noted that the lack of response of birds on corn/soybean meal diets indicates that a more diversified group of NSP enzymes seems necessary.

University of Manitoba research found that the complexity of the enzyme mix was highly correlated with improved ileal protein digestibility and feed:gain (Meng et al., 2005). Two simple but important factors were identified: (1) an appropriate group of enzymes is essential and (2) enzyme combinations must target specific NSPs.

Hence, enzymes that are not appropriately paired with NSP substrates exert no benefit. Predictably, an enzyme combination that worked best for soybean meal, canola and peas was not the most optimal for wheat because leguminous NSPs differ significantly from cereal NSPs (Meng et al., 2005).

Xylanase, for example, will serve little purpose with NSPs in soybean and canola meals since the substrate for this enzyme is low in legumes.

Other work concurs that ingredients require carbohydrases specific to the NSP (Malathi and Devegowda, 2001). For corn/soybean meal, pectinase combinations with hemicellulase or with hemicellulase plus cellulase generally showed improved digestibility for protein and organic matter, as well as apparent ME, over the non-enzyme control (Tahir et al., 2006).
In vitro digestibility of corn/soybean meal was improved by a mix of seven enzymes, but individually, only cellulase had the same effect (Saleh et al., 2004).

Certainly, enzymes with debranching side activities should not be overlooked (Huisman et al., 1999). The highly branched nature of corn arabinoxylans, as well as pectins in soybean meal, indicates a need for this type of enzyme. Removing the branches improves exposure of the arabinoxylans to xylanase and the pectins to pectinase.

The primary contribution from feed proteases is improved amino acid digestibility and live performance (Dozier et al., 2010; Angel et al., 2011; Freitas et al., 2011).

A combination of protease and several carbohydrases more effectively solubilized protein and cell wall components in soybean meal than either one did alone at higher concentrations (Marsman et al., 1997). Little work has focused on proteases plus pectinases or galactosidases for corn/soybean meal diets, possibly because pectinases are not widely available.

Some NSPs can chelate phytate (Kim et al., 2005), which is highly associated with protein vacuoles (Bohn et al., 2007). Ileal phosphorus digestibility was more effectively improved with a mix of NSP enzymes plus phytase, as opposed to phytase alone (Woyengo et al., 2010). The appropriate mix of carbohydrases along with protease might permit a greater phytic acid degradation in the presence of phytase.

Dynamic supplementation

The Figure denotes the dynamics taking place over a typical growout period. During this time, the ingredient mix naturally changes to meet nutrient requirements with a least-cost formulation. These modifications are accompanied by changes in dietary NSP composition and level, which can be 10-15% of the feed.

At the same time, the neonate’s gut is rapidly developing. Amino acid digestibility is poor in early versus older ages, leaving a significant amount of dietary protein undigested. Once the digestive system matures, amino acid digestibility increases, leaving less opportunity for exogenous proteases to improve digestion.

From starter to finisher, NSP levels can change 30% or more. In a corn/soybean meal-based diet, for example, NSPs such as pectins and oligosaccharides from soybean meal are a bigger concern during the starter phase. As the growout ensues, inclusion of soybean meal declines while the inclusion levels of corn and dried distillers grains plus solubles (DDGS) increase, meaning arabinoxylans become more prevalent.

As the NSP substrates change, it stands to reason that primary NSP enzymes should change. The same goes for other substrates such as protein, for example, where a protease could make greater contributions early in the feeding period, when protein content is highest.

Enzyme studies

We conducted a series of studies to supplement an enzyme mix to address intestinal tract maturity while simultaneously addressing the substrate levels and types over the life span of the growing broiler. The enzymes target pectins and oligosaccharides, as well as cereal NSPs, protein, starch and phytate.

Previous experimental work helped establish the basis behind enzyme levels to address physiological age and feed substrate levels. These include pectinase, xylanase, amylase, glucanase, debranching enzymes, protease and phytase.

Respiratory chamber research
Indirect calorimetry measures oxygen consumption and carbon dioxide production to quantify nutrient utilization (McLean and Tobin, 1987). Closed respiratory chamber systems with a living animal can assess energy expenditures and can quantify energy losses due to challenges such as coccidiosis (Teeter, 2010). Indirect calorimetry also can provide insight on the efficacy of enzymes for improved ME (Caldas et al., 2014).

In a trial using respiration chambers, Cobb broilers were fed a commercial diet with and without the enzyme product. This enzyme product lowered (P < 0.0006) metabolic oxygen uptake and lowered (P < 0.001) carbon dioxide production (Table 1), indicating a more efficient use of the feed. Ultimately, this translated into improved ME by 51 kcal/kg of final feed.

Previously, researchers at Oklahoma State University found a similar enzyme composition to improve (P < 0.05) the “effective caloric value” (ECV) in feed for broilers (Teeter et al., 2012) when using respiration chambers. The elevated ECV corresponded with improved (P < 0.05) bodyweights and feed:gain in the same study, indicating a good agreement between the chamber research and live performance of floor pen birds.

Chick battery studies
Early research was expanded to include battery studies to test the ability of this enzyme product to improve bodyweight and feed conversion. In one experiment, day old Ross 708 male broiler chicks were randomly allocated across base dietary treatments of corn/soybean meal with 3% corn DDGS.

The enzyme product was added to the negative control diet, which was formulated to be lower in ME, phosphorus and protein compared to the positive control.

The enzyme product increased bodyweight by 6.7% and 5.5% and improved feed:gain by 6.2% and 3.9% on days 10 and 17, respectively, in broiler chicks (Table 2).

The positive control group was fed starter diet similar to typical commercial diets, yet the performance of the negative control plus enzyme group outperformed the control group. This suggests that the enzyme composite eliminated some antinutritional components in the normal starter diet in this trial.

Early life performance is indicative of lifetime performance, and here, 17-day performance was improved over both control groups.

Floor pen research
The final phase in development focused on fl oor pen research in broilers to test the product under conditions similar to those in commercial practice. In one experiment, day-old Cobb x Cobb 500 chicks were randomly allocated at the rate of 45 birds per pen, with 12 replications per treatment.

Diets were consistent with commercial formulations. Deficits in ME, amino acids, phosphorus and calcium were present in the negative control diets. Throughout the life of the bird, the nutritional deficit was recouped by the enzyme mixture without performance loss for either bodyweight,or feed conversion ratio (Table 3).

Each phase was provided a different enzyme composite to account for both physiological development and available substrates. This avoids a conventional static approach with one enzyme or group of enzymes across all feeds, which does not account for intestinal and substrate changes.

Summary

At hatch, the chick is not adequately prepared to efficiently digest feed. This, along with the changing levels and composition of NSPs over the production period, necessitates an adjustment in enzyme supplementation. Appropriate enzyme selection is crucial to account for the range in NSP components in feed ingredients and the levels of physiological maturity. Not all enzyme synergies are understood, but certainly, sufficient information is available to develop multi-component enzymes for corn/soybean meal diets to improve the efficiency of meat production.

References

References are available online to subscribers at www.Feedstuffs.com or by request from tlundeen@feedstuffs.com