Environmental factors and genetic parameters of growth traits in Tunisian local sheep

Abstract This study aimed to evaluate the growth performance of lambs from four Tunisian sheep breeds. It involved 45780 lambs in 134 flocks from 99 farms. The zootechnical data (live weight, average daily gain) for the period 2011–2016 were obtained from the C of Genetic Improvement of the Office of Livestock and Pastures in Sidi Thabet. The results obtained showed a significant difference in weight and daily gains at typical ages. Lambs from single births were heavier than lambs from double births (1.05 ± 0.14 and 1 ± 0,01 kg). ADGs were influenced by the sex-mode of birth (P < 0.05). Single-born lambs showed higher ADGs, followed by twice-born lambs. The genetic type factor significantly influenced the growth of the lambs (P < 0.05). However, it should be noted that performance (weight growth and average daily gain) was better at the QFO breed. The age of the dams showed higher ADGs in lambs from dams aged 3 to 4 years, while the lowest ADGs were recorded in lambs from dams aged 5 years and older. The heritability coefficients of weights at different ages were estimated at 0.16 ± 0.04 for ADG3060 and 0.48 ± 0.03 for W10. The lowest values were observed for the ADG3060 (0.16 ± 0.021). The highest value is obtained for P10. Estimates of the genetic correlation for W10 with other parameters (W60, ADG0030, and ADG3060) were of the order of 14–42% of the variability.