Influence of biological and environmental factors on growth of Ouled Djellal lambs (Ovis aries) in Northeastern Algeria

This study evaluated the influence of biological (sex, litter size) and environmental (region, year, and month of birth) factors growth performance of Ouled Djellal lambs raised under semi-intensive systems in northeastern Algeria. Data from 2,605 lambs born between 2015 and 2021 across three wilayas (administrative divisions equivalent to provinces) Constantine, Bordj Bou Arréridj, and Oum El Bouaghi were analyzed using generalized linear models. Body weights were recorded at birth, 30, 60, 90, and 120 days of age, and average daily gains for the corresponding periods (ADG0–90, ADG90–120, ADG0–120) were calculated. Results showed that the mean BW, W90, and W120 were 4.48 ± 0.16 kg, 18.79 ± 0.10 kg, and 21.82 ± 0.14 kg, respectively. The mean ADG0–90, ADG90–120, and ADG0–120 were 159.6 ± 1.08, 107.2 ± 1.64, and 144.7±1.18 g·day-1, respectively. These results varied according to biological and environmental factors (P