Lactation performance and nitrogen utilization of dairy cows on diets including unfermented or fermented yellow wine lees mix

Abstract Yellow wine lees (YWL) consist of a high content of crude protein with relatively low price. With microbial pretreatment, the increased crude protein content in the fermented YWL mix may be beneficial for the lactation performance of dairy cows. The current study was conducted to investigate lactation performance and nitrogen (N) utilization in lactating dairy cows receiving unfermented and fermented YWL mix as alternative protein source for soybean meal. Fifteen multiparous mid-lactation Chinese Holstein dairy cows with similar parity (2.30, SD 0.32), days-in-milk (190, SD 15.2) and milk yield (25.0, SD 0.45 kg) were used in a replicated 3 × 3 Latin square design. Diets were isonitrogenous and isocaloric, with a forage-to-concentrate ratio of 60:40 [dry matter basis]. Three dietary treatments were designed as follows (dry matter basis): (1) total mixed ration containing 18% soybean meal (Control), (2) total mixed ration containing 11% unfermented YWL mix (UM), and (3) total mixed ration containing 11% fermented YWL mix (FM). Each period lasted for 20 d, with the first 15 d used for adaptation and the next 5 d used for sampling. Dry matter intake (P = 0.04), milk yield (P = 0.02), milk protein yield (P = 0.02) and energy-corrected milk yield (P = 0.05) were higher in cows fed the control and FM diets than in those cows fed the UM diet. Milk composition, feed efficiency (milk yield/dry matter intake), and N conversion rate were not different (P > 0.05) among the three groups. The cows fed the UM diet showed lower N intake (P