Vitamin nutrition in high yielding dairy cows

Vitamins are a class of nutrients used by animals to maintain normal growth, production, reproduction and health. Cows, like other animals, need vitamins to maintain optimal production performance and health. Different from pigs, chickens and ducks, dairy cows are herbivorous livestock. Compared with water-soluble vitamins, fat-soluble vitamins are more likely to be deficient, so the nutrition of vitamins A, D and E is particularly important. However, under the conditions of stress or high yield, B vitamins need to be added to the diet of dairy cows, which changes the traditional view that B vitamins exist in natural feed, and B vitamins synthesized by rumen microorganisms can fully meet the requirements of adult ruminants for B vitamins.

Fat-soluble vitamins

Vitamin A: Vitamin A is found only in animals. Plants do not contain vitamin A, but do contain probeta-carotene. Vitamin A supplementation is required if the forage is not fed enough or of poor quality, or if the forage stored for a long time has oxidized and lost a large amount of carotene, or if roughage consists of a large amount of corn silage and concentrate feed has low carotene content. For high-yielding dairy cows, vitamin A requirements can be met by dietary carotene and stable vitamin A supplementation. One mg of carotene is equivalent to 400IU of vitamin A equivalent.

Vitamin E: Fresh herbage is rich in vitamin E (80 to 200IU/kg), and the content in silage and hay can be reduced by 20% to 80%. Vitamin E content in concentrate is usually low and will decrease with the extension of storage period. Vitamin E plays an important role in antioxidant, immune response improvement and perinatal disease reduction of dairy cows. Since the vitamin E content in the base diet varies greatly, the vitamin E requirement of dairy cows mainly refers to the supplemental amount. Studies on the relationship between vitamin E and perinatal diseases of dairy cows mainly focus on mammary gland infection, clinical mastitis incidence and fetal retention.

Vitamin D: Vitamin D is necessary for the absorption and metabolism of calcium and phosphorus. Vitamin D3 (cholecalciferosterol) can be formed by skin exposure to the sun, and vitamin D2 can be formed by grass exposure to the sun. Due to the structural instability of natural vitamin D, it is generally accepted that dietary supplementation should be based on the recommended amount of vitamin D. Vitamin D deficiency causes bone failure to calcify properly, leading to rickets in calves and osteomalacia in adult cattle. Vinet et al. (1985) supplemented dry dairy cattle with 0, 5000 or 10000IU of vitamin D daily, and measured the occurrence of milk fever and plasma concentrations of calcium, phosphorus and 25-OD-D3. The results showed that 10000IU of vitamin D daily supplementation could meet the vitamin D requirement of dry dairy cattle fed on silage base diet. And reduce the occurrence of milk heat. Hustmyer et al. (1994) injected 50 doses of 1,25 -(OH)2-D3 under the skin of Juan shan cow for 7 consecutive days, which enhanced lymphocyte differentiation and proliferation.

Water-soluble vitamin

Folic acid: Necessary for protein synthesis because folic acid is involved in the transfer of carbon units in amino acid metabolism. In the perinatal period, cows have a large amount of new tissue synthesis (fetal, fetal membrane and mammary gland development and milk protein synthesis) and a long cycle of pregnancy and lactation, thus requiring a high amount of folic acid [2]. Girard et al. (1995) reported that from 45 days gestation to 6 weeks after calving, 160mg of folic acid was injected intraduritoneum per week in cows, and folic acid concentrations in placenta and colostrum increased by 24% and 54%, respectively. The milk yield increased by 1.5kg/d from 45 days of gestation to dry milk period.

Niacin: Nicoic acid synthesized by ruminal microorganisms of ruminants can meet the needs of metabolism and production. However, dairy cows lack nicoic acid due to the increase of milk yield, the increase of concentrate ratio in diet or the excess of leucine, arginine and glycine, and the destruction of nicoic acid in feed and tryptophan that can synthesize nicoic acid in body during feed processing. 1997). Chemiller(1986), Jaster and Ward(1990) supplemented 6mg niacin daily to dairy cows in early lactation, increasing milk production by 4% to 6%. Kraszewski et al. (1991) supplemented cows with protected (rumen-protected) or unprotected nicotinamide 4, 8 and 16g/d from 10 days to 90 to 100 days postpartum. Results Supplementation of unprotected nicotinamide did not significantly affect milk yield of dairy cows, but supplementation of 16g protected nicotinamide could increase milk yield, milk fat percentage and milk protein content of dairy cows (P<0.01).

Each vitamin requirement is influenced by the availability of other major nutrients and micronutrients, so the nutritional requirements of high yielding cows need to be continuously studied to yield more benefits.