Maekawa M, Beauchemin K A, Christensen D A
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Canada.
J Dairy Sci. 2002 May;85(5):1165-75. doi: 10.3168/jds.S0022-0302(02)74179-9.
Eight ruminally cannulated lactating Holstein cows were used in a double 4 x 4 Latin square to determine the effects of 1) proportion of barley silage [40, 50, and 60% of dry matter (DM)] in the diet, and 2) feeding a total mixed ration (TMR) compared with separate ingredients (SI) on chewing activities, saliva production, and ruminal pH. Although cows fed SI were offered a diet containing 50% silage, they actually consumed a diet containing 43% silage (DM basis). Dry matter intake and milk yield were similar for all diets (18.2 kg of DM/d and 27.2 kg/d, respectively). Cows fed the 40% silage TMR spent more time eating than cows fed SI (243 vs. 198 min/d), but rumination time was similar (546 min/d). Eating time was similar among the TMR diets, but rumination time increased from 498 to 516 and 584 min/d as silage in the TMR increased from 40 to 50, and then to 60%, respectively. The secretion of saliva per gram of feed was 4.43, 3.18, and 1.19 ml/g of DM with consumption of silage, TMR, and concentrate, respectively. Resting salivation rate was similar for all diets (101 ml/min). Regardless of the diet, cows secreted 239 +/- 17 L/d of saliva, and ruminal pH was below 5.8 for 10 h/d. Results indicated increased chewing time did not increase total daily saliva secretion because increased eating and ruminating saliva was associated with decreased resting saliva. Feeding SI increased the risk of acidosis, because cows ate a higher proportion of concentrate than intended.
选用8头安装有瘤胃瘘管的泌乳荷斯坦奶牛，采用双4×4拉丁方设计，以确定以下因素的影响：1）日粮中大麦青贮料的比例[干物质（DM）的40%、50%和60%]，以及2）与单独饲喂各成分（SI）相比，饲喂全混合日粮（TMR）对咀嚼活动、唾液分泌和瘤胃pH值的影响。尽管饲喂SI的奶牛所提供的日粮含有50%的青贮料，但它们实际采食的日粮青贮料含量为43%（以DM计）。所有日粮的干物质采食量和产奶量相似（分别为18.2千克DM/天和27.2千克/天）。饲喂40%青贮料TMR的奶牛比饲喂SI的奶牛采食时间更长（分别为243分钟/天和198分钟/天），但反刍时间相似（546分钟/天）。TMR日粮之间的采食时间相似，但随着TMR中青贮料比例从40%增加到50%，再增加到60%，反刍时间分别从498分钟/天增加到了516分钟/天和584分钟/天。每克饲料的唾液分泌量分别为：采食青贮料时为4.43毫升/克DM，采食TMR时为3.18毫升/克DM，采食精料时为1.19毫升/克DM。所有日粮的静息唾液分泌率相似（101毫升/分钟）。无论日粮如何，奶牛每天分泌239±17升唾液，瘤胃pH值每天有10小时低于5.8。结果表明，咀嚼时间增加并未增加每日唾液分泌总量，因为采食和反刍时唾液分泌增加与静息唾液分泌减少有关。饲喂SI增加了酸中毒风险，因为奶牛采食的精料比例高于预期。
