INRA, UR 631 SAGA, Auzeville, F-31326, Castanet-Tolosan, France.
J Anim Sci. 2013 Jul;91(7):3121-8. doi: 10.2527/jas.2012-6176. Epub 2013 May 8.
Improvement of feed efficiency can be achieved by genetic selection directly on feed to BW gain ratio or for alternative traits. In the present study, 2 different traits were explored in the growing rabbit and their heritability and genetic correlations with traits recorded between weaning (30 d) and 63 d of age: i) residual feed intake (RFI), to select animals having low ad libitum feed intake independently from their production level, and ii) ADG under restricted feeding (ADGR; with a restriction level of 80% compared with ad libitum feeding of a control group), to select animals having high growth rate despite limited feed intake. To study these traits, 2 rabbit lines were established named i) ConsoResidual line and ii) ADGrestrict line. Under ad libitum or restricted feeding, it comes to select animals that waste less energy for maintenance, metabolism, or activity and retain more for tissue deposition. The selection process was similar in both lines. Data comprised records from generations 0 to 6 for about 1,800 rabbits per line measured for their BW at weaning and 63 d of age (BW63) and their individual feed consumption. Under ad libitum feeding, the heritability estimates were moderate for RFI (0.16 ± 0.05), ADG (0.19 ± 0.05), and feed conversion ratio (FCR; 0.22 ± 0.05). The high genetic correlation estimated between RFI and FCR (0.96 ± 0.03) was in accordance with the literature. The genetic correlation between RFI and ADG traits was not significant. Thus, selection for low RFI with ad libitum feeding was confirmed as a potential trait to improve FCR and reduce feed intake, with little effect on ADG. To our knowledge, there is no previous selection experiment on growing rabbits with restricted feeding. Our heritability estimates for ADGR and feed conversion ratio under restricted feeding (FCRR) were moderate (0.22 ± 0.06 and 0.23 ± 0.07, respectively) and had very high negative genetic correlation. Both selection criteria were found with high and favorable genetic correlations with feed efficiency recorded under each feeding regimen. However, their different genetic correlations with BW at weaning and at 63 d of age (BW63R; respectively, 0.85 and 0.17 for RFI and -0.25 and 0.81 for ADGR) suggested different impacts on major production traits that need further analyses to decipher the relative advantages of the 2 selection criteria, together with interactions between genotypes and feeding regimen.
通过对饲料与体重增长比或替代特性的直接遗传选择，可以提高饲料效率。在本研究中，对生长兔进行了 2 种不同特性的探索，这些特性的遗传力和与断奶（30 日龄）至 63 日龄之间记录的特性的遗传相关性如下：i）残余采食量（RFI），选择自由采食时采食量低但生产性能不受影响的动物，ii）限饲条件下的平均日增重（ADGR；与对照组自由采食相比，限制水平为 80%），选择在限制采食条件下仍有较高生长速度的动物。为了研究这些特性，建立了 2 个兔品系，分别命名为 i）ConsoResidual 系和 ii）ADGrestrict 系。在自由采食或限饲条件下，选择那些用于维持、代谢或活动的能量消耗较少，而用于组织沉积的能量保留较多的动物。在这两条线中，选择过程是相似的。数据包括 1800 只左右的兔子的记录，每条线大约有 1800 只兔子，用于记录断奶时和 63 日龄时的体重（BW63）和个体饲料消耗量。在自由采食条件下，RFI（0.16 ± 0.05）、ADG（0.19 ± 0.05）和饲料转化率（FCR；0.22 ± 0.05）的遗传力估计值适中。RFI 和 FCR 之间估计的高遗传相关性（0.96 ± 0.03）与文献一致。RFI 和 ADG 性状之间的遗传相关性不显著。因此，在自由采食条件下对低 RFI 的选择被证实是提高 FCR 和减少饲料摄入的一种潜在特性，对 ADG 的影响很小。据我们所知，以前没有关于生长兔限饲的选择实验。我们对限饲条件下 ADGR 和饲料转化率（FCRR）的遗传力估计值适中（0.22 ± 0.06 和 0.23 ± 0.07），且具有非常高的负遗传相关性。两个选择标准都与每个饲养方案下记录的饲料效率具有高度有利的遗传相关性。然而，它们与断奶和 63 日龄体重（BW63R；分别为 RFI 的 0.85 和 0.17，ADGR 的-0.25 和 0.81）的遗传相关性不同，这表明对主要生产特性有不同的影响，需要进一步分析以破译这两个选择标准的相对优势，以及基因型和饲养方案之间的相互作用。
