Nutrition and Clinical Nutrition Department, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt.
J Anim Physiol Anim Nutr (Berl). 2010 Apr;94(2):264-72. doi: 10.1111/j.1439-0396.2008.00913.x. Epub 2009 Nov 11.
One hundred and twenty early lactating Holstein dairy cows were assigned to investigate the effect of dietary chromium (Cr) supplementation (0 or 6 mg Cr/head/day from organic preparation) on the productive and reproductive performance as well as on some blood serum parameters under heat stress (35-40 degrees C). Cows received treatment from 3 weeks pre-partum through 12 weeks post-partum. Chromium supplemented diet had lower body weight loss and improved dry matter intake with consequent reduction in the energy balance deficits during the first period after calving when compared with the control group. Chromium supplementation increased (p < 0.05) milk yield by 6.7%, 12.3% and 16.5% at 4, 8 and 12 weeks post-partum, respectively, whereas milk composition and milk to feed ratio were unaffected (p > 0.05) when compared with the control. Moreover, dietary Cr supplementation had no effect (p > 0.05) on blood serum glucose, calcium and phosphorus concentrations. A reduction (p < 0.05) of non-esterified fatty acids at 1 week pre-partum, 2 and 4 weeks post-partum was also observed. Serum insulin concentration increased whereas cortisol concentration decreased, when compared with the control group, throughout the whole experimental period. Also Cr supplementation showed a trend towards improving reproductive performance as indicated by increased percentage of pregnant cows in the first 28 days of breeding. It could be concluded that dietary Cr supplementation at level of 6 mg/head/day may offer a potential protective management practice to lessen the effect of heat stress in dairy cattle.
120 头泌乳早期荷斯坦奶牛被分配来研究日粮铬（Cr）补充（0 或 6mg Cr/头/天来自有机制剂）对热应激（35-40 摄氏度）下生产性能和繁殖性能以及一些血清参数的影响。奶牛从产前 3 周开始接受治疗，直至产后 12 周。与对照组相比，补充铬的日粮使产后第一阶段的体重损失减少，干物质采食量增加，从而减少了能量平衡赤字。铬补充剂使产后 4、8 和 12 周的牛奶产量分别增加（p<0.05）6.7%、12.3%和 16.5%，而与对照组相比，牛奶成分和奶料比不受影响（p>0.05）。此外，日粮 Cr 补充对血清葡萄糖、钙和磷浓度没有影响（p>0.05）。还观察到，在产前 1 周、产后 2 周和 4 周，非酯化脂肪酸（NEFA）减少（p<0.05）。与对照组相比，血清胰岛素浓度增加，皮质醇浓度降低，整个实验期间均如此。此外，Cr 补充剂也表现出改善繁殖性能的趋势，表现在配种后 28 天内怀孕牛的比例增加。可以得出结论，日粮 Cr 补充水平为 6mg/头/天可能为减轻奶牛热应激的影响提供一种潜在的保护管理措施。
