Grion A L, Mercadante M E Z, Cyrillo J N S G, Bonilha S F M, Magnani E, Branco R H
Instituto de Zootecnia, Centro APTA Bovinos de Corte. Sertãozinho, SP, Brazil, 14160-970.
J Anim Sci. 2014 Mar;92(3):955-65. doi: 10.2527/jas.2013-6682. Epub 2014 Feb 3.
The objectives of this study were to estimate genetic parameters for indicator traits of feed efficiency and to recommend traits that would result in better responses to selection for increased weaning weight (weaning weight adjusted to 210 d of age [W210]), ADG, and metabolic BW (BW(0.75)) and lower DMI. Records of W210 from 8,004 Nellore animals born between 1978 and 2011 and postweaning performance test records from 678 males and females born between 2004 and 2011 were used. The following feed efficiency traits were evaluated: G:F, partial efficiency of growth (PEG), relative growth rate (RGR), Kleiber's ratio (KR), residual feed intake (RFI), residual weight gain (RWG), and residual intake and gain (RIG). Covariance and variance components were estimated by the restricted maximum likelihood method using multitrait analysis under an animal model. Estimates of genetic gain and correlated responses were obtained considering single-stage and 2-stage selection. Heritability estimates were 0.22 ± 0.03 (W210), 0.60 ± 0.08 (DMI), 0.42 ± 0.08 (ADG), 0.56 ± 0.06 (BW(0.75)), 0.19 ± 0.07 (G:F), 0.25 ± 0.09 (PEG), 0.19 ± 0.07 (RGR), 0.22 ± 0.07 (KR), 0.33 ± 0.10 (RFI), 0.13 ± 0.07 (RWG), and 0.19 ± 0.08 (RIG). The genetic correlations of DMI with W210 (0.64 ± 0.10), ADG (0.87 ± 0.06), and BW(0.75) (0.84 ± 0.05) were high. The only efficiency traits showing favorable responses to selection for lower DMI were G:F, PEG, RFI, and RIG. However, the use of G:F, PEG, or RFI as a selection criterion results in unfavorable correlated responses in some growth traits. The linear combination of RFI and RWG through RIG is the best selection criterion to obtain favorable responses in postweaning growth and feed intake of Nellore cattle in single-stage selection. Genetic gains in feed efficiency are expected even after preselection for W210 and subsequent feed efficiency testing of the preselected animals.
本研究的目的是估计饲料效率指标性状的遗传参数，并推荐一些性状，这些性状将能对提高断奶体重（调整至210日龄的断奶体重[W210]）、平均日增重（ADG）和代谢体重（BW(0.75)）以及降低干物质采食量（DMI）的选择产生更好的反应。使用了1978年至2011年间出生的8004头内洛尔牛的W210记录，以及2004年至2011年间出生的678头雄性和雌性牛的断奶后性能测试记录。评估了以下饲料效率性状：料重比（G:F）、生长部分效率（PEG）、相对生长率（RGR）、克莱伯比率（KR）、剩余采食量（RFI）、剩余增重（RWG）和剩余采食量与增重（RIG）。协方差和方差分量采用动物模型下的多性状分析，通过限制最大似然法进行估计。考虑单阶段和两阶段选择，获得了遗传进展和相关反应的估计值。遗传力估计值分别为0.22±0.03（W210）、0.60±0.08（DMI）、0.42±0.08（ADG）、0.56±0.06（BW(0.75)）、0.19±0.07（G:F）、0.25±0.09（PEG）、0.19±0.07（RGR）、0.22±0.07（KR）、0.33±0.10（RFI）、0.13±0.07（RWG）和0.19±0.08（RIG）。DMI与W210（0.64±0.10）、ADG（0.87±0.06）和BW(0.75)（0.84±0.05）的遗传相关性较高。对降低DMI的选择表现出有利反应的唯一效率性状是G:F、PEG、RFI和RIG。然而，将G:F、PEG或RFI用作选择标准会在一些生长性状上产生不利的相关反应。在单阶段选择中，通过RIG将RFI和RWG进行线性组合是在内洛尔牛断奶后生长和采食量方面获得有利反应的最佳选择标准。即使在对W210进行预选并对预选动物进行后续饲料效率测试之后，预计饲料效率仍会有遗传进展。
