Vitamin A and E in the total mixed ration as influenced by ensiling and the type of herbage

The objective of this study was to evaluate the effects of ensiling on vitamin A (retinol) and vitamin E (α-tocopherol) contents in the total mixed ration (TMR) containing different types of herbage. Oat hay (O-TMR), alfalfa hay (A-TMR) and oat hay + alfalfa hay (OA-TMR) were separately mixed with soybean milk residue, corn meal, soybean meal, salt and a vitamin-mineral supplement to make the TMR. The TMR was sampled after 0, 7, 14, 28 and 56 days of ensiling. The fermentation quality, chemical composition and contents of vitamins A and E were determined. The vitamin A content was affected by the ensiling and herbage type (p < 0.05). After 56 days of ensiling, the three TMR silages had good fermentation quality, but the vitamin A content of O-TMR, OA-TMR and A-TMR decreased by 59.4%, 58.1% and 53.7%, respectively. Moreover, the content of vitamin A was positively correlated with the pH and negatively correlated with the lactic acid content during the 56 days of ensiling of the TMR silages. However, there were no effects of ensiling and herbage type on the vitamin E content. Thus, the preservation strategy for vitamin A in the TMR during ensiling requires further study.