Chizzotti M L, Tedeschi L O, Valadares Filho S C
Texas A&M University, College Station, TX 77843, USA.
J Anim Sci. 2008 Jul;86(7):1588-97. doi: 10.2527/jas.2007-0309. Epub 2008 Mar 28.
A meta-analysis was conducted to determine NE and net protein requirements of growing bulls, steers, and heifers of Nellore purebred and Nellore x Bos taurus crossbreds. A database of 16 comparative slaughter studies (n = 389 animals) was gathered to provide enough information to develop equations to predict the requirements of NE(m), NE(g), and net protein for maintenance (NP(m)) and growth (NP(g)). The data were analyzed using a random coefficients model, considering studies as random effects, and sex and castrate status (bulls, steers, and heifers; n = 262, 103, and 24, respectively) and breeds as fixed effects. There were no differences in NE(m) requirements among sex and castrate status (P = 0.73) and breeds (P = 0.82). The combined data indicated a NE(m) requirement of 75 kcal/ kg(0.75) of empty BW (EBW) with a partial efficiency of use of ME for NE(m) of 0.67. The NE(g) requirement was different (P = 0.009) among sex and castrate status and tended (P = 0.06) to be different among breeds. The equation for NE(g) requirement for bulls was 0.0514 x EBW(0.75) x EWG(1.070); for steers, it was 0.0700 x EBW(0.75) x EWG(1.070); and for heifers, it was 0.0771 x EBW(0.75) x EWG(1.070), where EWG = EBW gain (kg/d). The partial efficiency of use of ME for NE(g) was not different among sex and castrate status (P = 0.33) and breeds (P = 0.20) and averaged 0.44. There were no differences in NP(m) requirement among sex and castrate status (P = 0.59) and breeds (P = 0.92); the overall NP(m) requirement was 1.74 g of NP.kg(-0.75) of EBW.d(-1). The overall MP requirement for maintenance was 2.59 g of MP.kg(-0.75) EBW.d(-1). The NP(g) requirement (g/d) was not different among sex and castrate status (P = 0.59) and breeds (P = 0.14); the overall equation was EWG x [217 - (12.8 x RE/EWG)], where RE = retained energy (Mcal/d). The percentage of RE deposited as protein (%RE(p)) decreased exponentially as the content of RE in the gain (REc, Mcal/kg of EWG) increased. Because no study effect was observed, we pooled the data across studies and the overall equation to predict %RE(p) was 10.1 + 167e((-0.66 x REc)). Our results do not support the hypothesis that bulls have greater NE(m) requirements than steers and heifers. Likewise, no significant differences in the NP(m) requirements among bulls, steers, and heifers were detected. Nonetheless, the NE(g) requirement of steers was greater than bulls and less than heifers. Even though the %RE(p) was negatively correlated with the concentration of energy in the EWG, our findings indicated no differences in NP(g) requirement among bulls, steers, and heifers.
进行了一项荟萃分析，以确定内洛尔纯种牛以及内洛尔×黄牛杂交种生长公牛、阉公牛和小母牛的净能（NE）和净蛋白质需求。收集了一个包含16项比较屠宰研究（n = 389头动物）的数据库，以提供足够的信息来建立预测维持（NP(m)）和生长（NP(g)）所需的NE(m)、NE(g)和净蛋白质的方程。使用随机系数模型对数据进行分析，将研究视为随机效应，性别和去势状态（公牛、阉公牛和小母牛；分别为n = 262、103和24）以及品种视为固定效应。性别和去势状态（P = 0.73）以及品种（P = 0.82）之间的NE(m)需求没有差异。合并数据表明，NE(m)需求为每千克空体重（EBW）0.75的75千卡，ME用于NE(m)的部分利用效率为0.67。性别和去势状态之间的NE(g)需求不同（P = 0.009），品种之间有差异趋势（P = 0.06）。公牛的NE(g)需求方程为0.0514×EBW(0.75)×EWG(1.070)；阉公牛为0.0700×EBW(0.75)×EWG(1.070)；小母牛为0.0771×EBW(0.75)×EWG(1.070)，其中EWG = EBW日增重（千克/天）。ME用于NE(g)的部分利用效率在性别和去势状态（P = 0.33）以及品种（P = 0.20）之间没有差异，平均为0.44。性别和去势状态（P = 0.59）以及品种（P = 0.92）之间的NP(m)需求没有差异；总体NP(m)需求为每千克EBW每天1.74克NP。维持所需的总体可代谢蛋白质（MP）需求为每千克EBW每天2.59克MP。NP(g)需求（克/天）在性别和去势状态（P = 0.59）以及品种（P = 0.14）之间没有差异；总体方程为EWG×[217 - (12.8×RE/EWG)]，其中RE = 沉积能量（兆卡/天）。随着增重中能量含量（REc，兆卡/千克EWG）的增加，沉积为蛋白质的RE百分比（%RE(p)）呈指数下降。由于未观察到研究效应，我们对各研究的数据进行了合并，预测%RE(p)的总体方程为10.1 + 167e((-0.66×REc))。我们的结果不支持公牛比阉公牛和小母牛有更高NE(m)需求的假设。同样，在公牛、阉公牛和小母牛之间未检测到NP(m)需求的显著差异。尽管如此，阉公牛的NE(g)需求大于公牛且小于小母牛。尽管%RE(p)与EWG中的能量浓度呈负相关，但我们的研究结果表明公牛、阉公牛和小母牛之间的NP(g)需求没有差异。
