McGuffey R K, Basson R P, Spike T E
Lilly Research Laboratories, A Division of Eli Lilly and Company, Greenfield, IN 46140.
J Dairy Sci. 1991 Sep;74(9):3095-102. doi: 10.3168/jds.S0022-0302(91)78495-6.
Ninety multiparous Holstein cows were used to determine the effect of ration energy density and bST on lactation performance and whole body chemical composition. Seventy-eight cows, averaging 43.6 d postpartum, were assigned for 168 d to TMR with forage: concentrate ratios of 40:60, 50:50, and 60:40 (DM basis). Half of the cows on each ration received subcutaneously either 0 or 640 mg bST/28 d. Whole body chemical composition was determined by comparative slaughter in 12 cows (means = 35.9 d postpartum) prior to initiation of treatment and in 35 cows after either 84 or 168 d of treatment. Net energy intake was greater for 40:60 and 50:50 than for 60:40. Milk fat percentage was reduced in cows fed 40:60. Ration did not affect milk, 3.5% FCM, and DMI. There were no differences among rations for total body fat, protein, water, and calories. The bST increased milk and 3.5% FCM but had no effect on DM and net energy intakes. Yield of 3.5% FCM by cows receiving bST and fed 40:60 was 1.9 kg/d more and for 50:50 it was 2.7 kg/d more than for those fed 60:40. Administration of bST reduced total body fat and calories but did not affect protein and water. Partitioning of calories to milk at the expense of fat deposition is the primary mechanism for the galactopoietic action of bST.
选用90头经产荷斯坦奶牛来确定日粮能量密度和牛生长激素（bST）对泌乳性能及全身化学成分的影响。78头平均产后43.6天的奶牛被分配到全混合日粮（TMR）组，日粮的粗饲料:精饲料比例分别为40:60、50:50和60:40（干物质基础），为期168天。每组日粮中有一半的奶牛皮下注射0或640毫克bST/28天。在处理开始前，通过比较屠宰法测定12头奶牛（平均产后35.9天）的全身化学成分，在处理84天或168天后，测定35头奶牛的全身化学成分。40:60和50:50比例日粮的净能量摄入量高于60:40比例的日粮。采食40:60比例日粮的奶牛乳脂率降低。日粮对牛奶、3.5%乳脂校正乳（FCM）和干物质采食量（DMI）没有影响。不同日粮之间，全身脂肪、蛋白质、水分和热量没有差异。bST增加了牛奶产量和3.5% FCM，但对干物质和净能量摄入量没有影响。接受bST且采食40:60比例日粮的奶牛，其3.5% FCM产量比采食60:40比例日粮的奶牛每天多1.9千克；采食50:50比例日粮的奶牛，其3.5% FCM产量比采食60:40比例日粮的奶牛每天多2.7千克。注射bST减少了全身脂肪和热量，但不影响蛋白质和水分。以脂肪沉积为代价将热量分配到牛奶中是bST产奶作用的主要机制。
