Schoonmaker J P, Cecava V M J, Faulkner D B, Fluharty F L, Zerby H N, Loerch S C
Department of Animal Sciences, The Ohio State University, Wooster 44691, USA.
J Anim Sci. 2003 Apr;81(4):843-55. doi: 10.2527/2003.814843x.
Seventy-three crossbred steers (initial BW = 170.5 +/- 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 +/- 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet.
来自俄亥俄州立大学的73头杂交阉牛（初始体重=170.5±5.5千克）（实验1）和来自伊利诺伊大学的216头杂交阉牛（初始体重135.4±4.4千克）（实验2）被用于确定能量来源和生长速度对早期断奶阉牛的生产性能、胴体特性以及葡萄糖和胰岛素水平的影响。使用瘤胃造瘘阉牛（实验3）对实验1和2中所用日粮对瘤胃pH值和挥发性脂肪酸（VFA）浓度的影响进行了量化。在所有实验中，牛平均在119日龄断奶，并根据年龄、体重和品种分配到四种日粮之一：高浓度日粮，自由采食（ALCONC）；高浓度日粮，饲喂以达到1.2千克/天（1.2CONC）或0.8千克/天（0.8CONC）的增重；或高纤维日粮，自由采食（ALFIBER）。在218日龄时，所有阉牛都改为ALCONC日粮直至屠宰。在所有实验开始时给阉牛植入复合剂量的药物，并在估计距屠宰还有100天时给它们植入瑞瓦洛-S。当实验1中的阉牛平均年龄达到181和279日龄时，采集血清样本以测定葡萄糖和胰岛素浓度。当脂肪厚度达到1.27厘米时（实验1）或在采食273天后（实验2）对阉牛进行屠宰。在实验1中，ALCONC和ALFIBER阉牛的育肥天数（P＜０.０１）和屠宰年龄（P＜０.０１）最低，0.8CONC阉牛的最高。总体而言，ALCONC阉牛的平均日增重最高，0.8CONC阉牛的最低；ALFIBER阉牛的饲料效率最低（P＜０.０１）。各处理间的最终体重无差异（P＞０.５７）。在181和218日龄时，ALCONC阉牛的血清胰岛素水平分别升高（P＜０.１０），肌内脂肪百分比最高（P＜０.０７）。在实验2中，ALCONC阉牛的总体平均日增重（P＜０.０６）和最终体重（P＜０.０４）最高，1.2CONC和0.8CONC阉牛的最低。总体饲料效率0.8CONC阉牛最高，ALFIBER阉牛最低（P＜０.０１）。生长阶段的日粮对218日龄或屠宰时的大理石花纹评分没有影响（P＞０.８１）。在实验3中，采食后瘤胃pH值的差异可能分别是由于乙酸（ALFIBER）、丙酸（ALCONC）或挥发性脂肪酸组合（0.8CONC和1.2CONC）增加所致（日粮×采食后时间，P＜０.１０）。与自由采食高浓度或高纤维日粮相比，通过限饲高浓度日粮仅持续100天来控制生长，并不会延长早期断奶阉牛的生长曲线或提高屠宰时的肌内脂肪沉积。
