Miller T P, Tucker W B, Lema M, Shin I S, Hogue J F, Adams G D
Animal Science Department, Oklahoma State University, Stillwater 74078.
J Dairy Sci. 1993 Nov;76(11):3571-9. doi: 10.3168/jds.S0022-0302(93)77696-1.
The objective of this study was to evaluate the influence of dietary buffer value index on ruminal fluid pH, buffering capacity, and buffer value index in lactating cows. Three Holstein cows averaging 18 +/- 10 DIM were used in a 3 x 3 Latin square with 3-wk experimental periods. Diets contained grain:sorghum silage DM ratios of 50:50, 60:40, and 70:30. By analysis, these diets had buffer value indexes of -74, -41, and -7. The analyzed dietary buffer value index of the total diets was higher than the index that was calculated from the buffer value index of individual ingredients. Although milk fat content tended to be highest for milk from cows fed the 50:50 concentrate to forage diet and although milk protein production was highest for cows fed the 70:30 concentrate to forage diet, milk yield, 4% FCM, milk fat yield, protein content, and milk fat content were not significantly affected by dietary buffer value index. Dietary buffer equivalents were calculated to be 11% of total buffering equivalents available to the cow, and dietary acid equivalents were 15% of total acid production in the rumen. Compared with ruminal acid production and salivary buffering in the rumen, dietary acid and dietary buffer contributions to the acid-base balance of the cow are minor quantitatively. Ruminal fluid pH, hydrogen ion concentration, buffer value index, buffering capacity, and total VFA were not affected significantly by dietary buffer value index. Hence, dietary acid-base status alone is inadequate as a predictor of the need for buffers in the diet of lactating cows.
本研究的目的是评估日粮缓冲值指数对泌乳奶牛瘤胃液pH值、缓冲能力和缓冲值指数的影响。选用3头平均产犊天数为18±10天的荷斯坦奶牛，采用3×3拉丁方设计，试验期为3周。日粮中谷物与高粱青贮干物质比例分别为50:50、60:40和70:30。经分析，这些日粮的缓冲值指数分别为-74、-41和-7。总日粮的分析缓冲值指数高于根据各成分缓冲值指数计算得出的指数。虽然饲喂50:50精粗比日粮的奶牛所产牛奶的乳脂含量趋于最高，饲喂70:30精粗比日粮的奶牛所产牛奶的蛋白质产量最高，但日粮缓冲值指数对牛奶产量、4%乳脂校正乳、乳脂产量、蛋白质含量和乳脂含量均无显著影响。日粮缓冲当量计算为奶牛可利用的总缓冲当量的11%，日粮酸当量为瘤胃总酸产生量的15%。与瘤胃酸产生和瘤胃唾液缓冲相比，日粮酸和日粮缓冲对奶牛酸碱平衡的贡献在数量上较小。日粮缓冲值指数对瘤胃液pH值、氢离子浓度、缓冲值指数、缓冲能力和总挥发性脂肪酸均无显著影响。因此，仅日粮酸碱状态不足以预测泌乳奶牛日粮中缓冲剂的需求。
