Effect of dietary protein source on performances and rumen characteristics of dairy cows

Abstract

A feeding trial of 8 weeks was carried out following a complete randomized design with 27 dairy cows in their second month of lactation. The aim was to evaluate the effect of three sources of dietary protein, soybean meal, fish meal and cottonseed meal, on the performances and rumen characteristics of dairy cows. Three rumen-fistulated dairy cows were assigned for the study of rumen fermentation. The source of dietary protein did not significantly influence the dry matter intake, but significantly affected milk yield ( P < 0.05). The fish meal group produced significantly less milk, but the concentration of total solids, lactose and protein was higher than in the control group with soybean meal. The ruminal pH declined to its lowest level 1 h after feeding and gradually increased afterwards. The ruminal pH of the fish meal group was lowest 1 h postprandial, but did not reach the statistical difference level. The source of dietary protein did not significantly affect the ruminal ammonia concentration, but had a significant effect on the volatile fatty acid (VFA) concentration in the rumen ( P < 0.05). Total VFA concentration was significantly higher in the cottonseed meal group than in the other treatment groups before and within 2 h after feeding ( P < 0.05). Protein source also significantly influenced the acetate and the propionate concentration and their ratio ( P < 0.05). From 1 to 2 h postfeeding, the ratios were not statistically different. However, the ratio was significantly higher from 4 to 8 h postprandial in the cottonseed meal group as compared to the fish meal group ( P < 0.05). Compared to soybean meal, the ratio was only significant higher before feeding and from 4 to 6 h, postprandial ( P < 0.05).