EFFECT OF DIETARY-PROTEIN SOURCE ON PERFORMANCES AND RUMEN CHARACTERISTICS OF DAIRY-COWS

A feeding trial of 8 weeks was carried out following a complete random ized design with 27 dairy cows in their second month of lactation. The aim was to evaluate the effect of three sources of dietary protein, s oybean meal, fish meal and cottonseed meal, on the performances and ru men characteristics of dairy cows, Three rumen-fistulated dairy cows w ere assigned for the study of rumen fermentation. The source of dietar y protein did not significantly influence the dry matter intake, but s ignificantly affected milk yield (P < 0.05), The fish meal group produ ced significantly less milk, but the concentration of total solids, la ctose and protein was higher than in the control group with soybean me al. 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 differe nce 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). Tota l VFA concentration was significantly higher in the cottonseed meal gr oup than in the other treatment groups before and within 2 h after fee ding (P < 0.05), Protein source also significantly influenced the acet ate and the propionate concentration and their ratio(P < 0.05), From 1 to 2 h postfeeding, the ratios were not statistically different. Howe ver, 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 bef ore feeding and from 4 to 6 h, postprandial (P < 0.05). (C) 1997 Elsev ier Science B.V.