Folic acid supplementation during fattening period affects growth and nutritional metabolism in Japanese Black beef cattle.

The folate requirements for beef cattle have not been established. Therefore, we investigated whether rumen-unprotected folic acid supplementation during the fattening period affects carcass traits and nutritional metabolism in Japanese Black beef cattle. Eighteen Beef cattle aged 16 months were divided into three groups: control, low folic acid supplementation (0.43 g DM/day), and high folic acid supplementation (0.86 g DM/day). Treatment was administered for 12 months. Folic acid supplementation dose-dependently increased serum folate levels, suggesting that supplemental folic acid can be absorbed into the body. Folic acid supplementation dose-dependently decreased serum vitamin B levels, while plasma total homocysteine and methylmalonic acid levels-markers for deficiency of folate and/or vitamin B-were unaffected. Thus, the treatment did not clearly affect the nutritional status of these vitamins. Supplementation increased body weight, with no negative effects on other carcass traits. The levels of insulin-like growth factor 1, retinol, albumin, and some amino acids in serum or plasma were affected by supplementation. These results suggest that rumen-unprotected folic acid supplementation during the fattening period could increase the body weight of Japanese Black beef cattle and the mechanism of action may be related to growth-related hormones and/or the metabolism of some nutrients, including folate.