Feeding Management to Improve Reproductive Performance in Bovines
Feeding management plays an important role in successful reproduction. Deficiency of various trace minerals, inadequate vitamin intakes, energy protein imbalances and excessive protein intakes are reported as contributors to infertility and poor reproductive performance and leading to economic losses to dairy farmers. Animals with superior genetic merit contribute to more milk production. The dairy cow has changed significantly over the last decades with a remarkable growth in milk production. Nutritional management of cow, especially during periods of high levels of stress is an important and challenging target to maintain and improve animal health and reproduction. Energy requirement and reproduction: Energy intake is most important nutritional factor affecting reproduction on most dairy farms. It affects reproductive performance in early lactating cows and heifers if insufficient energy is taken. The nutritional requirements of a dairy cow significantly support foetal growth, mammogenesisand lactogenesis during late pregnancy and early postpartum. The negative effect of NEB affects on animal health and reproduction. When cows having a period of NEB, blood levels of non-esterified fatty acid (NEEFA) increase as a consequence of body energy reserve mobilization (adipose tissue), at the same time insulinlike growth factor-I (IGF), glucose and insulin are low. Cows that are over energy when they calve have a higher incidence of retained placenta more uterine infections and more cystic ovaries. All of these problems can result in poor reproductive performance. Achieving a body condition score of 3.5 at calving (0-5 scale) should be the target. Adequate dry matter intake about 2.8-3.5% (as per feeding standards) of total mixed ration (TMR) having crude protein 14-16%, fat 5-6%, NDF about 34%, TDN around 70.00% (about 1.63 NE lactation Mcal/kg). An adequate macro and micro nutrients helps in maintaining the optimum fertility in dairy cows.
Protein requirement and reproduction:
Over last some years more importance has been put on rumen, soluble, degradable protein and its role in reproduction. These proteins are degraded by the rumen microbes (bacteria) into ammonia.In case when large amount of ammonia is produced, the excess amount of it gets absorbed into the blood stream and is converted to urea by the liver. High blood urea will result in increased risk of early embryonic mortality, impaired sperm viability and decrease progesterone concentrations. Reproductive performance reduces due to inadequate protein intake from long times. Excess of dietary protein has been suggested as detrimental to fertility. The protein level of greater than17-20% may reduce conception rate and increases number of services per conception and also days open. The excess ammonia and urea in the blood stream may decrease fertility at the same time energy is diverted away from milk production and reproduction. Some studies have indicated that blood urea nitrogen (BUN) above 20 mg/100 ml may decrease the chances of pregnancy.
FAT REQUIREMENT AND REPRODUCTION
In bovines certain fatty acids may play an important role in reproduction. Linoleic and linolenic have a beneficial impact on reproduction. There are a couple of potential mechanisms as to how these fatty acids can improve reproduction, including: 1. Increased progesterone concentration: Higher concentration of progesterone will lead to better pregnancy rates. Progesterone has main function is toprepare uterus for pregnancy by reducing uterine contractions. 2. Decrease prostaglandin secretion: Prostaglandins act in opposite manner of progesterone. They induce uterine contractions and eliminate the CL and consequently progesterone production thus potentially reducing pregnancy rates when an egg is fertilized. Supplementation of moderate amounts of fat to the diet improve energy intake, modulate PGF2α secretion by the uterus, affects ovarian dynamics, enhances luteal function and embryo quality and has moderate positive effects on fertility.
NUTRIENTS AND REPRODUCTION
Right level of minerals and vitamins also very important for successful reproduction. Deficiency of some minerals and vitamins will have a more effect on reproduction. These trace minerals bound to small protein fractions (amino acids) and are more bio-available than inorganic forms. Minerals: Mineral deficiencies and imbalance often causes of poor reproduction.
Phosphorus: Phosphorus is one of the important elements for normal sexual behaviour in dairy cows. P deficiency leads to delayed onset of puberty and silent or irregular oestrus in heifers, failure of oestrus and long inter calving period in cows, still born or weakly expelled calves or even embryonic death due to lack of uterine muscle tone, decreased ovarian activity, delayed sexual maturity and moderate deficiency may lead to repeat breeding condition and poor conception rate. The excess of P in diet renders the endometrium susceptiblefor infection. Phosphorus deficiency during dry period has been incremented for vaginal or uterine prolapse. Concentration of P in the seminal plasma of active bulls was positively correlated with quantity and quality parameters of bull semen. Only in extreme deficiencies (0.2 -0.25% of the diet) dose phosphorus reduce reproductive performance.
Calcium: Calcium is required for many physiological processes as a regular in all living cells including sperm cells. Deficiency disorders of calcium are very common during parturition or within few days following parturition. Altered of Ca:P ratio, affects ovarian function through its blocking action on pituitary gland which results in prolongation of first oestrus, ovulation, prolonged uterine involution, increased incidence of dystocia, retention of placenta and uterine prolapsed potentially leading to impaired fertility. Moreover, excess of Ca can also affect reproductive status of animal by impairing of P, Mn, Zn, Cu and other element from gastro intestinal tract. Ca: P ratio of under 1.5:1 or > 3:1 could potentially lead to reproductive problems.Ca should be balanced for 0.9- 1.0% of the diet.
Sodium and Potassium: Sodium and Potassium are the principal cations in extracellular and intracellular fluids, respectively. Sodium and potassium are responsible for maintenance of osmolarity and activity of spermatozoa. It also regulates sperm motility and the acrosome reaction. Deficiency of Na causes general infertility and embryonic mortality in several farm animals. Feeding of high level of K may delay the onset of puberty, delay ovulation, impair corpus luteum development and increaseincidence of anoestrus in heifers. Too more K: Na leads to lower fertility in cows.
Magnesium: Magnesium has an important effect on reproduction and is also required during gestation and lactation. During pregnancy, a positive correlation was observed between plasma concentrations of progesterone. During high energy requirement, Mg requirement increased manifold. Mg is an active component of several enzyme systems in which thymine pyrophosphate is a cofactor .
Selenium: Selenium plays a very important role in maintaining high fertility. Selenium is a component of glutathione peroxidase, which protects cells from per-oxidative damage. In female, Se deficiency leads to silent heat periods, poor fertilization, delayed conception, cystic ovaries, reduced sperm motility, reduced uterine motility, metritis, mastitis and retained foetal membrane. In males, Se deficiency reduces sperm viability. Selenium deficient herds received supplement selenium (50 mg) and vitamin-E (680 IU) injections at 20 days prior to calving or were fed 1 mg of selenium per day.
Iodine: Reproduction is influenced through iodine’s action on the thyroid gland. Iodine supplementation has been recommended when necessary to insure that cows consume 15-20 mg of iodine each day. More doses of iodine reduce resistance to infection, disease and abortion. Iodine deficiencies may indirectly cause early embryonic death, abortion, still births prolonged gestation and an increase in the incidence of retained placenta.
Zinc: Zinc is involved in several enzymatic reactions associated withcarbohydrate metabolism, protein synthesis, nucleic acids metabolism and steroidogenesis. Zinc has got a vital role in sexual maturity, onset of estrus and maintenance of the endometrial lining after parturition. The foetus requires Zn for normal growth and development. Zn deficiency results in foetal teratogenesis, abortion, foetal mummication, prolonged gestation, difficult labour, low birth weight and weak offspring. Zn deficiency in male causes atrophy of semniferous tubule and in efficient testicular development in young ones, leading to reduced testicular size, lack of libido and can adversely affect spermatogenesis. Zn supplement fed bulls led to sperm concentration, percentages of live sperm, motility, high semen volume. Zinc should be added at 75 mg/ kg of the diet.
Manganese: Manganese is required for activation of many enzymes systems, activity of certain endocrine organs, normal parturition and also involved in luteal tissue metabolism. Deficiency of Mn causes silent estrus and anoestrus or irreregular oestrus, cystic ovary, poor follicular developments with delayed ovulation, decreased conception rate, birth of deformed calves, abortion and absence of libido, decrease motility of spermatozoa and oligozoospermia in ejaculate and failure of spermatogenesis. Heifers fed inadequate Mn in the diet showed late sign of estrus than supplemented with Mn and also exhibited lower conception rates. Manganese is generally added @50 mg/kg of the diet.
Cobalt: Cobalt is an important component of vitamin-B12. Depletion of Cobalt at parturition results to a decline in milk production. Clinical signs of cobalt deficiency in female include delayedpuberty, anaemia, delayed involution of uterus and reduced conception rate, anestrus and abortion. In males, Cobalt deficiency is decreases libido, reduces spermatogenesis and sterility in males. Cobalt should be added at 0.5 mg/kg of the diet.
Molybdenum: Molybdenum work as protein synthesis, metabolization and utilization of iron store in the body, with subsequent direct effects on biological process controlling growth and reproductive performance. Molybdenum deficiency in female causes delayed puberty, reduced conception rate, anestrus and in male decreased libido, reduced spermatogenesis, causes sterility.
Copper: It is an enzyme component and catalyst, Copper deficiency is associated with early embryonic death, reduced ovarian activity, decreased conception rate, increased incidence of retained placenta and increased difficulty in calving. The recommended is to feed 20 mg/kg of added copper to diet.
Iron: Iron is necessary component of haemoglobin and myoglobin for oxygen transport and cellular use. Deficiency of iron, affects response of ovarian receptor to estrogens hormones, become repeat breeders and occasionally may abort in female. Iron content within the seminal plasma is important for the preservation of sperm motility and viability after ejaculation and its presence helps spermatozoa to maintain their functions.
Chromium: Chromium is crucial for carbohydrate and lipid metabolism. It is present in high concentration in nuclear proteins thus it is necessary for gametogenesis and healthy foetal growth. Cattle placed on chromium supplementation had an increasedpregnancy rate and interval from calving to first estrus. Vitamin: Good amount of vitamins and minerals balance in dry cow ration is drawing more attention especially when feed intake is restricted and low quality forage is fed to control or reduced body condition. Providing optimum amount of vitamins A and E may improve the immune status of the periparturient cows thus decreasing the incidence of retained foetal membranes, mastitis and improve pregnancy rate.
Vitamin A: Beta-carotene is a substance found in many plants and bovine changes this into vitamin A. Vitamin A is important in maintaining the health and integrity of the epithelial tissue. The vitamin is required for steroidogenesis. Deficiency causes delayed puberty, delayed first oestrus after calving, low conception rate, high embryonic mortality, reduced libido in deficient cattle, abortion, delayed sexual maturity, the birth of dead or weak calves, metritis, retained foetal membrane, reduced gestation period and increase incidence of cystic ovaries have been reported. The daily supplementation of vitamin A to dairy cows is about 30,000-50,000 units. The current feeding recommendation (dairy NRC, 2001) for vitamin A (110 IU/kg body weight) revealed optimum amount.
Vitamin D: It is needed for normal metabolism of calcium and phosphorus. Vitamin D may be indirectly needed for reproduction. Cows receiving a normal amount of natural light manufacture their own vitamin D. Most commercial concentrates contains vitamin D in amounts sufficient to meet the cows requirements of 10,000 IU per day. The dietary supplementation of Vitamin Dshould be 1600-1700 IU/kg dry matter of the diet. Deficiencies of vitamin D causes to metritis, anestrum, milk fever, and retained placenta in dairy cows and impotentia coeundi in bulls.
Vitamin E: Vitamin E is plays a vital role in regulating immune functions and works in association with selenium. Vitamin E has been found to minimize the chances of retention of fetal membranes in cows. It is reported that supplementation of greater than 2000 IU/day of Vitamin E during transition period reduces incidence of mastitis and retained fetal membranes.
Vitamin B Complex: Reduction in appetite and decrease in feed intake occurs in vitamin-B12 deficiency which further leads to delay to sexual maturity and atrophy of the ovaries and uterus in cows. Cobalt is essential for vitamin-B12 synthesis. In case of biotin, biotin supplementation is essential. In an experiment feeding of 200 mg/day reduce conception days from 169 to 108 and reduces service per conception from 2.96 Vs 1.7.
APPLICATION OF CURRENT NUTRITIONAL CONCEPT FOR FERTILITY MANAGEMENT:
· Niacin feeding can prevent ketosis and maintain dry matter intake. The current recommended is to feed 6-12 grams/day until maximum dry matter in takes occurs (10-12 weeks postpartum).
· Buffers used as additive to maintain rumen pH between 6-6.3 Sodium bicarbonate and sodium sesquicarbonate are the most common commercial products fed at 120-250 grams/cow/day.
· Propylene glycol use, it is converted by liver to glucose which can prevent ketosis and fatty liver formation.
· Yeast culture and yeast products can activate fibre fermenting bacteria, maintain rumen pH, and stimulate volatile fatty acid (VFA) production. Yeast product can also be kept as for cattle feed and these are palatable. The level of yeast cultures and products vary from10-115 grams/cow/day.
· Reducing heat stress, in dairy cattle can improve production and fertility. Early lactation cows are most severely affected. This decreased feed intake changes the environment of the rumen and leads to acidosis and decreased fat content of milk.
· Maintaining a body condition score 3.0 – 3.5 at calving. Over feeding cows are more prone to uterine infection, retained placenta, ketosis and displaced abomasums.
· Protein level – Feeding inadequate level of protein feeding upto 12-14% and close to14-16% has been shown to increase the incidence of retained fetal membranes.
· Urea nitrogen and fertility: It is well known that daily intake of high protein increases milk production in dairy cows. However, at the same time, dairy cows fed high protein increases blood urea nitrogen (BUN) concentration, which is associated with reduced reproductive performance.
· Potassium level: High potassium will increase the incidence of milk fever and other fresh cow problems. Forages with low potassium content should be fed to keep levels of potassium under 1.5%.
Adequate dietary fibre: Maintainan adequate level for early lactating cows (minimum22-24% forage. Feed high quality, forage results in higher dry matter intakes. Avoid feeding stale or mouldy feed to cows because mouldy feed contain estrogenic compounds that can effect reproduction.
· Higher levels of vitamin E and adequate selenium intake will improve immune function and reduce the incidence of RFM. Close up cows should receive at least 1000-1300 IU of vitamin E.
· Fat: Consider feeding supplemental protected fat to improve energy status.
· Macro minerals: Calcium 0.60%,Phosphorus 0.38%, Magnesium 0.20%, Potassium 0.90%, Sodium 0.18%, Chloride 0.25%, Sulphur 0.20%.
· Trace minerals: Iron 50 ppm, Cobalt 0.10 ppm, Copper 10 ppm, Manganese 40 ppm, Zinc 40 ppm, Iodine 0.60ppm, Selenium 0.30ppm.
· Vitamins: Vitamin A 3190IU/kg, Vitamin D 990IU/kg, Vitamin E 15 IU/kg.
CONCLUSION
Management of feeding in bovines is essential for their proper production and reproduction. Infertility and other related problems such as poor reproductive performance caused due to deficiencies of trace minerals, inadequate intake of various vitamins, imbalances in energy and proteins lead to heavy economic loss to dairy farmers. A balanced ration supplying adequate quantities of minerals, vitamins, protein and energy balance is essential for proper production and reproduction of livestock.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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