PDF(Pubmed)
Abstract：
Feeding high-gain diets and an inadequate energy and protein ratio during pre-puberty may lead to impaired growth and mammary gland development of heifers. Thus, frequent application of bovine somatotropin (bST) may prevent future losses in productivity, improve mammary development and animal performance. We aimed to evaluate the effects of bST on digestibility, performance, blood metabolites, mammary gland development, and carcass composition of high-performance prepubertal Holstein × Gyr heifers. Thirty-four Holstein × Gyr heifers with an average initial body weight of 218 ± 49 kg and 14 ± 4 months of age were submitted to an 84-day trial evaluating the effects of no bST or bST injections. Treatments were randomly assigned to each animal within one of the tree blocks. The bST did not influence digestibility or performance parameters. Regarding blood results, IGF1 concentration presented an interaction between treatment and day, where bST heifers had the highest IGF1 concentration. Heifers receiving bST also showed increased ribeye area; however, only an experimental day effect for backfat thickness was observed, with greater accumulation of carcass fat on day 84. Heifers receiving bST had lower pixels/mm² on parenchyma, characteristic of greater parenchymal tissue. Moreover, heifers on bST treatment also had reduced pixels/mm2, characteristic of reduced fat pad tissue. Lastly, bST injections did not influence liver and muscle gene expression, nor most genes evaluated in mammary gland tissue, except for IGFBP3 expression, which was greater for bST heifers. In summary, we confirm the efficacy of bST injections to overcome the detrimental effects of high-gain diets on mammary gland growth and to improve lean carcass gain of prepubertal Holstein × Gyr heifers.
摘要：
在青春期前喂养高增益饮食以及能量和蛋白质比例不足可能导致小母牛的生长和乳腺发育受损。因此，频繁使用牛生长激素(bST)可以防止未来生产力的损失，改善乳腺发育和动物性能。我们旨在评估bST对消化率的影响，性能，血液代谢产物,乳腺发育,和高性能青春期前荷斯坦牛×体牛的car体组成。对34只平均初始体重为218±49kg，年龄为14±4个月的荷斯坦×Gyr小母牛进行了为期84天的试验，评估了不注射bST或bST的效果。将处理随机分配给一个树块内的每只动物。bST不影响消化率或性能参数。关于血液结果，IGF1浓度呈现治疗和天之间的相互作用，其中bST小母牛的IGF1浓度最高。接受bST的小母牛也显示出增加的肋眼面积；但是，仅观察到背脂厚度的实验日效应，在第84天，car体脂肪的积累更多。接受bST的小母牛的实质像素/mm²较低，大实质组织的特征。此外，bST治疗的母牛像素/mm2也减少，这是脂肪垫组织减少的特征。最后,bST注射不影响肝脏和肌肉基因表达，也不是在乳腺组织中评估的大多数基因，除了IGFBP3表达，这对bST小母牛来说更大。总之,我们证实了bST注射的有效性，以克服高增益饮食对乳腺生长的不利影响，并改善青春期前荷斯坦牛×Gyr小母牛的瘦car体增益。
