McClary D G, Sartin J L, Kemppainen R J, Williams J C
Department of Large Animal Surgery and Medicine, College of Veterinary Medicine, Auburn University, AL 36849.
Am J Vet Res. 1988 Oct;49(10):1702-4.
Five mature Holstein cows and 6 first-lactation Holstein cows were administered 100 mg of glucose/kg of body weight, IV, over a 20-minute period on postpartum day 30. A series (preinfusion, glucose infusion, and postinfusion) of blood samples was collected at -15, -10, -5, 5, 10, 15, 20, 30, 45, 60, 75, 90, 105, and 120 minutes from the start of the infusion. Serum was obtained and was assayed for glucose, immunoreactive insulin (IRI), growth hormone (GH), and free fatty acid concentrations. Baseline glucose and free fatty acid concentrations were similar in cattle of both groups throughout the sample collection period. Both groups of cattle disposed of the infused glucose in a similar manner. The first-lactation cows secreted significantly (P less than 0.0001) more IRI to utilize the glucose load than did the mature cows, 71 +/- 13 microU/ml vs 38 +/- 7 microU/ml, respectively (mean +/- SEM). Preinfusion and glucose infusion GH concentrations were similar in cattle of both groups. In the postinfusion period, GH values were significantly (P less than 0.0002) higher in the first-lactation cows (8.7 +/- 1.8 ng/ml) than in the mature cows (5.8 +/- 1.6 ng/ml). Compared with that in the mature cows, the higher IRI concentration required by the first-lactation cows to utilize approximately the same glucose load suggested that first-lactation cows were insulin resistant. The increased insulin response to increased glucose concentration may be one reason first-lactation cows produce less milk than do mature cows. Other factors, such as variation in the ability of the mammary gland to synthesize milk cannot be excluded.
在产后第30天，对5头成年荷斯坦奶牛和6头头胎泌乳荷斯坦奶牛静脉注射100毫克葡萄糖/千克体重，注射时间为20分钟。在输注开始后的-15、-10、-5、5、10、15、20、30、45、60、75、90、105和120分钟采集一系列血样（输注前、葡萄糖输注期间和输注后）。获取血清并检测葡萄糖、免疫反应性胰岛素（IRI）、生长激素（GH）和游离脂肪酸浓度。在整个样本采集期间，两组奶牛的基线葡萄糖和游离脂肪酸浓度相似。两组奶牛处理输注葡萄糖的方式相似。头胎泌乳奶牛为利用葡萄糖负荷分泌的IRI显著（P<0.0001）多于成年奶牛，分别为71±13微单位/毫升和38±7微单位/毫升（平均值±标准误）。两组奶牛输注前和葡萄糖输注期间的GH浓度相似。在输注后阶段，头胎泌乳奶牛的GH值（8.7±1.8纳克/毫升）显著（P<0.0002）高于成年奶牛（5.8±1.6纳克/毫升）。与成年奶牛相比，头胎泌乳奶牛为利用大致相同的葡萄糖负荷需要更高的IRI浓度，这表明头胎泌乳奶牛存在胰岛素抵抗。对葡萄糖浓度升高的胰岛素反应增加可能是头胎泌乳奶牛产奶量低于成年奶牛的一个原因。其他因素，如乳腺合成乳汁能力的差异也不能排除。
