Effects of milk replacer composition on selected blood metabolites and hormones in preweaned Holstein heifers
Effects of milk replacer composition on selected blood metabolites and hormones in preweaned Holstein heifers
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DOI：
10.3168/jds.2007-0859
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发表时间：
2008-07-01
影响因子：
3.5
通讯作者：
Akers, R. M.
中科院分区：
文献类型：
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作者：
Daniels, K. M.;Hill, S. R.;Akers, R. M.
我们研究了增加日粮蛋白质和能量对荷斯坦小母牛血液代谢产物和激素浓度的影响。24头小母牛饲喂4种MR日粮中的1种，为期9周（n = 6/饲料）：对照组[ 20%粗蛋白（CP），21%脂肪MR，以441 g干物质（DM）/d饲喂]，HPLF（28%CP，20%脂肪MR，以951 g DM/d饲喂）、HPHF（27%CP，28%脂肪MR，以951 g DM/d饲喂）和HPHF+（27%CP，28%脂肪MR，以1，431 g DM/d饲喂）。小母牛每天饲喂两次，自由选择水和发酵剂（20%CP，1.43%脂肪），每天记录发酵剂运动。每周两次采集空腹12小时后的血样，分析血清和血浆等分试样的胰岛素样生长因子（IGF）-I、IGF结合蛋白（IGFBP）、生长激素（GH）、胰岛素、葡萄糖、非酯化脂肪酸、甘油三酯和血浆尿素氮浓度。仅血糖、IGFBP-2和IGFBP-3受饮食影响。仅当对照组与其他3种饮食的平均值进行比较时，才注意到饮食处理差异。向MR中添加脂肪（HPLF vs. HPHF）和增加MR体积（HPHF vs. HPHF+）对血糖浓度或IGFBP-2或IGFBP-3的相对丰度没有影响。饲喂对照饮食的小母牛比其他3种饮食的平均值具有更少的葡萄糖、更大的IGFBP-2和更少的IGFBP-3。IGF-I存在饮食与周的相互作用。对照组小母牛血清IGF-I浓度呈二次曲线变化，第4周达到最低值（20 +/- 4 ng/mL），而其他饮食组小母牛的IGF-I呈线性增加。胰岛素和甘油三酯均以复杂模式随时间变化（显著的线性和二次对比效应）。对于胰岛素和甘油三酯，在第0.5周测量最大浓度，在第6周测量最低浓度。血清GH浓度以线性方式下降，从第0.5周至第9周在所有小母牛。IGFBP-2的相对丰度随时间呈二次曲线，在第5周观察到最大量的IGFBP-2。除葡萄糖、IGF-I、IGFBP-2和IGFBP-3外，测量的血液变量不受治疗影响。IGF-I -GH-IGFBP轴需要在小母牛中进一步研究，以推断营养对下丘脑代谢调节的影响。我们预计在涉及蛋白质和脂肪代谢的代谢物浓度方面会有更多的治疗差异。很可能是本研究中使用的饲料组成不够多样化，不足以引起此类变化，或者这些动物中吸收蛋白质和脂肪的使用效率没有差异。
We investigated the effects of increasing dietary protein and energy on concentrations of selected blood metabolites and hormones in Holstein heifers. Twenty-four heifers were fed 1 of 4 milk replacer (MR) diets for 9 wk (n = 6/diet): control [ 20% crude protein (CP), 21% fat MR fed at 441 g of dry matter (DM)/d], HPLF (28% CP, 20% fat MR fed at 951 g of DM/d), HPHF (27% CP, 28% fat MR fed at 951 g of DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1,431 g of DM/d). Heifers were fed twice daily; water and starter (20% CP, 1.43% fat) were offered free choice and starter orts recorded daily. Serum and plasma aliquots from blood samples collected twice weekly after a 12-h fast were analyzed for insulin-like growth factor (IGF)-I, IGF-binding proteins (IGFBP), growth hormone (GH), insulin, glucose, non-esterified fatty acids, triglyceride, and plasma urea nitrogen concentrations. Only plasma glucose, IGFBP-2, and IGFBP-3 were affected by diet. Dietary treatment differences were only noted when the control was compared with the average of the other 3 diets. The addition of fat to the MR(HPLF vs. HPHF) and increased volume of MR (HPHF vs. HPHF+) had no effect on plasma glucose concentration or relative abundance of IGFBP-2 or IGFBP-3. Heifers fed the control diet had less glucose, greater IGFBP-2, and less IGFBP-3 than the average of the other 3 diets. There was a diet by week interaction for IGF-I. Serum IGF-I concentration in control heifers varied in a quadratic manner with a nadir (20 +/- 4 ng/mL) at wk 4, whereas IGF-I increased linearly in heifers on other diets. Both insulin and triglyceride changed over time in a complex pattern (significant linear and quadratic contrast effects). The greatest concentrations were measured at wk 0.5 with nadirs at wk 6 for both insulin and triglyceride. Serum GH concentration decreased in a linear manner from wk 0.5 to wk 9 in all heifers. Relative abundance of IGFBP-2 was quadratic over time with the greatest amount of IGFBP-2 observed at wk 5. With the exception of glucose, IGF-I, IGFBP-2, and IGFBP-3, the blood variables measured were not influenced by treatment. The IGF-I -GH-IGFBP axis requires further study in heifers to deduce effects of nutrition on hypothalamic regulation of metabolism. We expected to see more treatment differences in concentrations of metabolites involved with protein and fat metabolism. It is likely that the diets used in this study were not diverse enough in composition to elicit such changes or that the efficiency of use of absorbed protein and fat was not different in these animals.