GenPhySE, INRA, Université de Toulouse, INPT, ENVT, 31326, Castanet Tolosan, France.
Institute for Food and Agriculture Research and Technology, Torre Marimon s/n, 08140, Caldes de Montbui, Barcelona, Spain.
Genet Sel Evol. 2018 May 10;50(1):25. doi: 10.1186/s12711-018-0395-9.
Indirect genetic effects (IGE) are important components of various traits in several species. Although the intensity of social interactions between partners likely vary over time, very few genetic studies have investigated how IGE vary over time for traits under selection in livestock species. To overcome this issue, our aim was: (1) to analyze longitudinal records of average daily gain (ADG) in rabbits subjected to a 5-week period of feed restriction using a structured antedependence (SAD) model that includes IGE and (2) to evaluate, by simulation, the response to selection when IGE are present and genetic evaluation is based on a SAD model that includes IGE or not.
The direct genetic variance for ADG (g/d) increased from week 1 to 3 [from 8.03 to 13.47 (g/d)] and then decreased [6.20 (g/d) at week 5], while the indirect genetic variance decreased from week 1 to 4 [from 0.43 to 0.22 (g/d)]. The correlation between the direct genetic effects of different weeks was moderate to high (ranging from 0.46 to 0.86) and tended to decrease with time interval between measurements. The same trend was observed for IGE for weeks 2 to 5 (correlations ranging from 0.62 to 0.91). Estimates of the correlation between IGE of week 1 and IGE of the other weeks did not follow the same pattern and correlations were lower. Estimates of correlations between direct and indirect effects were negative at all times. After seven generations of simulated selection, the increase in ADG from selection on EBV from a SAD model that included IGE was higher (~ 30%) than when those effects were omitted.
Indirect genetic effects are larger just after mixing animals at weaning than later in the fattening period, probably because of the establishment of social hierarchy that is generally observed at that time. Accounting for IGE in the selection criterion maximizes genetic progress.
间接遗传效应（IGE）是许多物种中各种性状的重要组成部分。尽管伴侣之间的社会互动强度可能随时间而变化，但很少有遗传研究调查在选择压力下的家畜性状的 IGE 如何随时间变化。为了克服这个问题，我们的目标是：（1）使用包含 IGE 的结构化相依（SAD）模型分析经历 5 周限饲期的兔子的平均日增重（ADG）的纵向记录，（2）通过模拟评估当存在 IGE 时的选择响应，以及当遗传评估基于包含或不包含 IGE 的 SAD 模型时。
ADG（g/d）的直接遗传方差从第 1 周到第 3 周增加[从 8.03 增加到 13.47（g/d）]，然后减少[第 5 周为 6.20（g/d）]，而间接遗传方差从第 1 周到第 4 周减少[从 0.43 减少到 0.22（g/d）]。不同周的直接遗传效应之间的相关性为中度至高度（范围为 0.46 至 0.86），并随测量之间的时间间隔而趋于降低。IGE 的趋势也相同，从第 2 周到第 5 周（相关性范围为 0.62 至 0.91）。第 1 周的 IGE 与其他周的 IGE 之间的相关性估计并不遵循相同的模式，相关性较低。直接效应和间接效应之间的相关性估计一直为负。经过 7 代的模拟选择，基于包含 IGE 的 SAD 模型的 EBV 选择对 ADG 的增加幅度（~30%）高于省略这些效应时的增加幅度。
在断奶后混合动物时，间接遗传效应比育肥期后期更大，这可能是由于此时通常观察到的社会等级制度的建立。在选择标准中考虑 IGE 可最大限度地提高遗传进展。
