EFFECTS OF NON-GENETIC FACTORS ON PRE-WEANING GROWTH TRAITS IN DORPER SHEEP MANAGED INTENSIVELY IN CENTRAL MEXICO | The effect of non-genetic factors on growth traits in Dorper sheep managed intensively in Central Mexico

Inglés. The objective of this study was to determine the non-genetic factors which a ect growth traits in Dorper lambs under intensive conditions. Nine hundred and ninety birth weight records and 851 weaning weight data from a commercial sheep farm were used. A model containing the e ects of year of birth, season of birth, litter size, dams' age and gender was used for identi cation of factors a ecting growth traits. Birth weight was highest (p < 0.05) in summer and lowest in winter and spring. Male lambs excelled females in birth weight, weaning weight, and average daily gain. Young dams produced o spring with a lower (p < 0.05) birth weight and weaning weight than older ewes As a conclusion, important in uences of environmental factors on growth traits were identi ed for Dorper lambs.

Español; castellano. The objective of this study was to establish the non-genetic factors which affect growth traits in Dorper lambs under intensive conditions. 990 birth weight records and 851 weaning weight data from a commercial sheep farm were used. A model containing the effects of year of birth, season of birth, birth status, dam´s age and gender was used for identification of factors affecting growth traits. Birth weight was highest (P<0.05) in summer (4.0±0.7 kg) and lowest in winter and spring (3.7±0.8 kg). Male lambs excelled females in birth weight (3.9±0.7 vs. 3.7±0.8 kg), weaning weight (33.4±5.8 vs. 31.3±5.4 kg) and average daily gain (328±63 vs. 309±57 g). Young dams produced offspring with a lower (P<0.05) birth weight (3.6±0.8 vs 3.9±0.8 kg) and weaning weight (30.9±5.8 vs 32.3±5.9 - 33.6±5.4 kg) than older ewes. It was concluded that important influences of environmental factors on growth traits were identified for Dorper lambs.