Depew C L, Bunting L D, Fernandez J M, Thompson D L, Adkinson R W
Department of Dairy Science, Louisiana State University Agricultural Center, Louisiana Agricultural Experiment Station, Baton Rouge 70803, USA.
J Dairy Sci. 1998 Nov;81(11):2916-23. doi: 10.3168/jds.S0022-0302(98)75853-9.
Forty-two Holstein calves were used to study performance and metabolic responses when milk replacer and then postweaning starter were supplemented with 1 ppm of Cr as Cr-tripicolinate. From birth through 8 wk of age, supplemental Cr tended to improve the growth performance of bull calves but not of heifer calves. Starter intake and feed efficiency were not affected by supplemental Cr. From 1 to 5 wk of age, plasma cortisol concentrations sampled just prior to feeding decreased, and concentrations of insulin-like growth factor-I increased. All calves appeared to become less sensitive to insulin as they aged. From 1 to 5 wk of age, plasma glucose and insulin concentrations gradually diverged for all calves; glucose concentrations decreased, and insulin concentrations increased. In addition, glucose clearance rate, measured by i.v. glucose tolerance tests, was more rapid when calves were 2 wk of age than when calves were 8 wk of age. The glucose clearance rate was greater in heifer calves than in bull calves but was not affected by supplemental Cr. Entry of plasma glucose following an i.v. propionate load was also greater in heifer calves than in bull calves but was not affected by supplemental Cr. Plasma nonesterified fatty acids were lower in calves fed milk replacer or starter supplemented with Cr than in control calves, although this effect diminished as calves aged. This finding was considered to be indirect evidence of enhanced insulin sensitivity in calves fed milk replacer or starter supplemented with Cr. Overall, data suggested that supplemental Cr-tripicolinate had minor effects on the metabolism and growth performance of conventionally managed dairy calves. The most notable effects occurred during the initial few weeks of life.
选用42头荷斯坦犊牛，研究在代乳粉和断奶后开食料中添加1 ppm吡啶羧酸铬（Cr）时的生产性能和代谢反应。从出生到8周龄，补充铬倾向于提高公牛犊的生长性能，但对母牛犊没有影响。补充铬对开食料采食量和饲料效率没有影响。在1至5周龄时，喂食前采集的血浆皮质醇浓度降低，胰岛素样生长因子-I浓度升高。随着年龄增长，所有犊牛似乎对胰岛素的敏感性都降低。在1至5周龄时，所有犊牛的血浆葡萄糖和胰岛素浓度逐渐出现差异；葡萄糖浓度降低，胰岛素浓度升高。此外，通过静脉注射葡萄糖耐量试验测得的葡萄糖清除率在犊牛2周龄时比8周龄时更快。母牛犊的葡萄糖清除率高于公牛犊，但不受补充铬的影响。静脉注射丙酸盐负荷后，母牛犊的血浆葡萄糖进入量也高于公牛犊，但不受补充铬的影响。与对照组犊牛相比，饲喂添加铬的代乳粉或开食料的犊牛血浆非酯化脂肪酸含量较低，不过随着犊牛年龄增长，这种影响会减弱。这一发现被认为是饲喂添加铬的代乳粉或开食料的犊牛胰岛素敏感性增强的间接证据。总体而言，数据表明补充吡啶羧酸铬对传统饲养的奶牛犊的代谢和生长性能影响较小。最显著的影响发生在生命的最初几周。
