Besufkad Shanbel, Goshme Shenkute, Bisrat Asfaw, Abebe Aschalew, Abebe Ayele, Getachew Tesfaye, Areaya Alemnew, Zewdie Tesfaye, Gizaw Solomon
Debre Birhan Agricultural Research Center, Debre Birhan, Ethiopia.
International Centre for Agricultural Research in the Dry Areas (ICARDA), Addis Ababa, Ethiopia.
Heliyon. 2024 Jan 19;10(2):e24971. doi: 10.1016/j.heliyon.2024.e24971. eCollection 2024 Jan 30.
The study aimed to estimate genetic and phenotypic parameters for growth traits and Kleiber ratio in Dorper sheep breed. Data used in this study were collected over 12 years (2012-2023) at Debre Birhan Agricultural Research Center sheep research station in Ethiopia. Studied traits were body weights at birth (WT0), weaning (WT3), six month (WT6), and yearling (WT12) age; average daily gains from birth to weaning (ADG0-3), from weaning to six months (ADG3-6), from six months to yearling (ADG6-12); and Kleiber ratios from birth to weaning (KR1) and from weaning to six months (KR2). The (co)variance components were estimated with different animal models using Average Information Restricted Maximum Likelihood (AI-REML) procedure. The best-fitted model for each trait was determined using likelihood ratio tests. Phenotypic performance for WT3, WT6, WT12, ADG0-3 and ADG3-6 showed a decline trend at a rate of 0.216 kg, 0.794 kg, 0.671 kg, 2.601 g and 4.865 g over years respectively. However, WT3, WT6, WT12, ADG0-3 showed a positive genetic improvement trend at a rate of 0.029 kg, 0.043 kg, 0.049 kg and 0.257 g over years respectively. Year of birth had a significant effect (P < 0.001) on all studied traits. Model including direct genetic as well as permanent environmental effect (Model 2) was chosen as the most appropriate model for WT0. Model which included only direct genetic effect (Model 1) was the best-fit model for all other studied traits. Direct heritability estimates based on suitable models were 0.07 ± 0.06, 0.11 ± 0.06, 0.09 ± 0.07, 0.11 ± 0.09 0.11 ± 0.06, 0.00 ± 0.04, 0.15 ± 0.07 and 0.00 ± 0.04 for WT0, WT3, WT6, WT12, ADG0-3, ADG3-6, KR1 and KR2 respectively. The variance ratio for the permanent environmental effect was 0.13 ± 0.04 for WT0. Genetic correlations among the traits ranged from negative (-0.39) for WT0-KR1 to high (0.99) for WT3-ADG0-3 and phenotypic correlations ranged from negative (-0.31) for WT0-KR1 to high (0.98) for WT3-ADG0-3. The low direct heritability estimates for the studied traits indicated that genetic improvement by direct selection might be difficult. Further investigation for the unexpected declined trend of phenotypic performance over years need to be required.
本研究旨在估计杜泊绵羊品种生长性状和克莱伯比率的遗传和表型参数。本研究使用的数据是在12年（2012 - 2023年）期间于埃塞俄比亚德布雷伯尔汉农业研究中心绵羊研究站收集的。研究的性状包括出生体重（WT0）、断奶体重（WT3）、6月龄体重（WT6）和周岁体重（WT12）；出生至断奶的平均日增重（ADG0 - 3）、断奶至6月龄的平均日增重（ADG3 - 6）、6月龄至周岁的平均日增重（ADG6 - 12）；以及出生至断奶的克莱伯比率（KR1）和断奶至6月龄的克莱伯比率（KR2）。使用平均信息约束最大似然法（AI - REML）程序，通过不同的动物模型估计（协）方差分量。使用似然比检验确定每个性状的最佳拟合模型。WT3、WT6、WT12、ADG0 - 3和ADG3 - 6的表型表现多年来分别以每年0.216千克、0.794千克、0.671千克、2.601克和4.865克的速率呈下降趋势。然而，WT3、WT6、WT12、ADG0 - 3多年来分别以每年0.029千克、0.043千克、0.049千克和0.257克的速率呈正遗传改良趋势。出生年份对所有研究性状均有显著影响（P < 0.001）。包含直接遗传效应以及永久环境效应的模型（模型2）被选为WT0的最合适模型。仅包含直接遗传效应的模型（模型1）是所有其他研究性状的最佳拟合模型。基于合适模型的直接遗传力估计值分别为WT0为0.07 ± 0.06、WT3为0.11 ± 0.06、WT6为0.09 ± 0.07、WT12为0.11 ± 0.09、ADG0 - 3为0.11 ± 0.06、ADG3 - 6为0.00 ± 0.04、KR1为0.15 ± 0.07、KR2为0.00 ± 0.04。WT0的永久环境效应方差比率为0.13 ± 0.04。性状间的遗传相关性范围从WT0 - KR1的负相关（-0.39）到WT3 - ADG0 - 3的高相关（0.99），表型相关性范围从WT0 - KR1的负相关（-0.31）到WT3 - ADG0 - 3的高相关（0.98）。所研究性状的低直接遗传力估计表明，通过直接选择进行遗传改良可能很困难。需要对多年来表型表现出人意料的下降趋势进行进一步调查。
