The reproductive performance of dairy cows is directly related to the level of production. There are many factors that affect the reproductive performance of dairy cows, such as breed, age, genetics, disease, nutrition and so on. The nutrients needed to supply dairy cows are the basis for improving the reproductive performance of dairy cows. Proper regulation of the supply level of dairy cows' various nutrient elements is the key to guaranteeing high yields of dairy cows.
1. Effect of energy on reproductive performance
(1) Prenatal energy excess: mainly refers to the first 2-3 months of dry milk, and the energy conversion efficiency is up to 70%. If the dairy cows are supplied with excessive energy during this period, the sensation is too good, which can easily lead to prenatal obesity syndrome. Postpartum prone to problems such as dystocia, ketosis, retention of placenta, and mastitis. Therefore, in this period, the supply of silage corn and concentrates should be reduced and more hay should be fed.
(2) Insufficient prenatal energy: Mainly refers to the end of lactation and dry milk period. The energy supply to dairy cows is too low, which makes the cows have poor sensation, which can easily cause the cows to get over the placental clothes and the lochia, resulting in delayed follicular growth and reduced the conception rate. . Therefore, it is necessary to appropriately increase the amount of concentrate and corn silage fed.
(3) Post-partum energy excess: Mainly refers to the cows with poor genetic potential and low milk yield. It is prone to post-production obesity, decreased egg cell mass, follicular cysts, and abnormal estrus.
(4) Insufficient postpartum energy: This period is the peak period of lactation, which can easily cause negative energy balance, delay the estrus of the cows, delay the development of follicles, and increase the resting estrus. Postpartum should be based on the level of lactation, appropriate to raise the level of dietary nutrition, feed fish meal, puffed soybeans and fats and other high-energy feed. For the first fetus, the appropriate amount of fat can effectively relieve the negative balance of energy, reduce the synthesis and release of insulin, promote the absorption of fat-soluble vitamins, and increase the number of ovulation.
2. Effect of protein on reproductive performance
(1) Insufficient protein: During the dry period, the diet with crude protein content of 8% was fed with a retention rate of 50%; the crude protein content of the diet was increased to 15%, and the retention rate of the dressing was reduced by 50%. Postpartum low protein causes slow follicular development, leading to abnormal estrus in dairy cows. Therefore, postpartum dietary protein content should be 16%-17%.
(2) Excess protein: Feeding too much protein during the postpartum period will reduce the pH in the uterus, increase the urea content in the blood, and change the composition of the uterus's fluids. It will have a toxic effect on the eggs and embryos, and it will weaken the immune system. Therefore, the amount of postpartum crude protein fed should not exceed 17%.
3. The effect of calcium and phosphorus on reproductive performance
(1) 15-20 days before birth: add anionic salt in the diet, do not feed the buffer, acidify the diet, lower the blood pH, stimulate the release of parathyroid hormone before delivery, and increase the absorption rate of calcium and phosphorus. Reduce the occurrence of postpartum calving fever and increase milk intake.
(2) Postpartum and peak lactation period: timely adjust the diet structure, increase calcium and phosphorus levels, and meet the needs of dairy cows for lactation, growth and reproduction. Therefore, the amount of calcium in the diet is 0.81%, and phosphorus is 0.5%-0.6%.
4. Effect of vitamins on reproductive performance
(1) In the absence of vitamin A, the cows showed miscarriage, no placental retention, metritis, and abnormal embryo development.
(2) Vitamin E can enhance the secretion of luteinizing hormones in the body and thus complete the fertilization process; adding vitamin E in early embryos can reduce embryonic death and miscarriage.
5. Effect of trace elements on reproductive performance
(1) Copper is a component of many enzymes and is directly involved in reproductive reproduction, protecting cells from the hazards of oxidative metabolism. Copper deficiency inhibits cow estrus.
(2) Zinc deficiency can affect prostaglandin synthesis and impair corpus luteum function.
(3) Manganese maintains normal reproduction and participates in vitamin synthesis. Manganese deficiency will cause abortion of dairy cows and malformation of newborn calves, resulting in an increase in the rate of recessive oestrus and a decline in the conception rate.
(4) Iodine is a substance necessary for the synthesis of thyroxine and triiodothyronine that regulates energy metabolism and can promote the synthesis of vitamin A. Iodine deficiency can easily cause obstruction of fetal development, increase the rate of retention of fetal clothing and decrease the reproductive capacity of dairy cows.
(5) Selenium can maintain the body's normal reproductive function, lack of selenium can cause cows, fetal clothing, metritis, ovarian cysts.
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