奶牛对甜菜粕(BP)替代谷物或饲料的反应不一致,热应激可能影响奶牛对这种替代的反应。本试验采用4 × 4拉丁方试验设计,以8头经产荷斯坦奶牛为试验对象,研究了用BP替代玉米青贮和大麦籽粒对采食量、生产性能和瘤胃参数的影响。泌乳中期(45.4 ± 3.6 kg/日产奶量,116 ± 10 d产奶量),平均体重664 ± 41.2 kg。饲粮处理如下:1)0% BP (0BP,对照,38.5%大麦籽粒和20.3%玉米青贮);2) 12% BP (12BP,大麦籽粒32.5%,玉米青贮14.3%);3) 18% BP (18BP、29.5%青贮大麦和11.3%青贮玉米);4) 24% BP (24BP,大麦26.5%,玉米青贮8.3%)。奶牛处于轻度热应激状态,平均温湿指数为70.5;血压升高导致呼吸频率线性下降(P < 0.01)。饲粮中较高的BP导致干物质摄入量(P = 0.01)和NDF消化率(P = 0.03)呈线性增加。 Dry and organic matter (OM) digestibilities tended to increase linearly with higher BP (P < 0.10). Milk yield, energy-corrected milk, protein, lactose, and fat production and content were not affected by the treatments. Increasing BP in the diet caused a linear decrease in feed efficiency and rumen ammonia (P < 0.05) and a tendency to a linear decrease in milk urea nitrogen (P < 0.10). Rumen pH and acetate to propionate ratio were not affected by the replacement. Total volatile fatty acid concentration in the rumen increased linearly with increasing the BP inclusion (P = 0.04). Acetate and butyrate (P = 0.07) proportion tended to increase, whereas propionate (P = 0.06) and isovalerate (P = 0.08) proportion tended to decrease linearly as BP was substituted for corn silage and barley grain. The results indicated that under mild heat stress condition, BP can be successfully substituted for barley grain and corn silage up to 24% of the diet without any negative effect on production and ruminal pH.
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