ABOMASAL INFUSION OF CASEIN ENHANCES NITROGEN-RETENTION IN SOMATOTROPIN-TREATED STEERS

被引:39
作者
HOUSEKNECHT, KL
BAUMAN, DE
FOX, DG
SMITH, DF
机构
[1] CORNELL UNIV,DEPT ANIM SCI,ITHACA,NY 14853
[2] CORNELL UNIV,DEPT CLIN SCI,ITHACA,NY 14853
关键词
SOMATOTROPIN; STEERS; IGF-1; PROTEIN REQUIREMENTS; GROWTH;
D O I
10.1093/jn/122.8.1717
中图分类号
R15 [营养卫生、食品卫生]; TS201 [基础科学];
学科分类号
100403 ;
摘要
The effects of bovine somatotropin (bST) administration and abomasal protein infusion on nitrogen metabolism were investigated using four abomasally-cannulated Holstein steers in a 4 x 4 Latin square design. Treatments were factorially arranged to include daily abomasal infusion (water or casein, 0.9 g/kg body wt) and dally bST injection (0 or 200-mu-g/kg body wt). Each treatment period lasted for 23 d and consisted of an adjustment period (d 1 to 7), casein infusion (d 8 to 23) and bST treatment (d 10 to 23). Nitrogen metabolism and serum insulin-like growth factor-I (IGF-I) profiles were characterized on d 16-22. Animals were fed a total mixed diet balanced to achieve 0.75 kg gain/d and supplemented to provide 115% of requirements for crude protein and minerals. Nitrogen retention was increased by casein and bST individually (21 and 33%, respectively) or in combination (75%). Somatotropin treatment increased the biological value of absorbed N, which was consistent with reductions in plasma urea nitrogen. Circulating IGF-I was increased by bST and was highly correlated (r = 0.73) with N retention. Overall, bST altered requirements so that less absorbed N was required per unit of N retained. However, results also demonstrated that because of limitations in amino acids supplied from microbial and ruminal escape protein in young growing cattle, amino acid supply may limit the magnitude of N retention response to bST under many situations.
引用
收藏
页码:1717 / 1725
页数:9
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