Analysis of factors affecting pre-weaning and post-weaning daily gains in Nigerian breeds of sheep

Sheep play significant role in the socio-economic life of the large human population. Improving the productivity of sheep through selection and breeding would require understanding of their growth characteristics. This study was conducted to assess the pre- and post-weaning daily weight gains (ADG) of four Nigerian sheep breeds and some non- genetic factors affecting them. Pre- and post-ADG were measured in 33, 34, 43 and 47 lambs of Balami, Uda, WAD and Yankasa ewes respectively, and analyzed to determine the effect of breed, sex, year, season, parity, and birth type. At the pre-weaning stage, Balami and Uda had similar gains (91.89g vs. 92.44g) which were higher than that of Yankasa (74.22g) which was in turn higher than that of WAD (62.44g). During the post weaning stage, Balami gained most (77.19g), followed by Uda (71.12g), and Yankasa (59.37g) while WAD still maintained the lowest rate of gain (55.15g). Male sheep had higher ADG than females, 100.7g vs. 87.8g at pre-; and 65.67 vs. 58.15g at post weaning. However, sex within breed analysis revealed non- significant influence of sex in all breeds except WAD at pre-weaning stage but males maintained better (p<0.01) rates of gain post-weaning. Pre-ADG decreased with increased litter size. Lambs born at first parity gained more (85.00g) than subsequent parity lambs. Season and year had no significant effect on both pre- and post-weaning gains. It is concluded that breed, sex, birth type and parity influenced average daily gain in sheep.     Les moutons jouent un role important dans la vie socio-economique de la population humaine. Pour ameliorer la productivite des moutons grâce a la selection et a l'elevage, il faudrait comprendre leurs caracteristiques de croissance. Cette etude a ete menee pour evaluer les gains de poids quotidiens avant et apres le sevrage (le 'ADG') de quatre races de moutons nigerians et certains facteurs non genetiques qui les affectent. Le Pre- et le post- 'ADG' ont ete mesures dans 33, 34, 43 et 47 agneaux de Balami, Uda, WAD et Yankasa brebis respectivement, et analyses pour determiner l'effet de la race, sexe, annee, saison, parite, et le type de naissance. Au stage de pre-sevrage, Balami et Uda ont connu des gains similaires (91.89 g contre 92.44 g) superieurs a ceux de Yankasa (74.22 g), ce qui est a son tour superieur a celui de WAD (62.44 g). Au cours de l'etape post-sevrage, Balami a gagne le plus (77.19 g), suivi par Uda (71.12 g) et Yankasa (59.37 g) tandis que WAD a maintenu le taux de gain le plus bas (55.15 g). Les moutons mâles avaient un ADG plus eleve que les femelles, 100.7 g contre 87.8 g a l'avant; et 65.67 contre 58.15 g au sevrage apres le sevrage. Cependant, le sexe dans l'analyse de race a indique l'influence non significative du sexe dans toutes les races excepte WAD au stade de pre-sevrage mais les mâles ont maintenu de meilleurs taux (p<0.01) de gain apres le sevrage. Le pre-ADG a diminue avec l'augmentation de la taille des portees. Les agneaux nes a la premiere parite ont gagne plus (85.00 g) que les agneaux parite subsequents. La saison et l'annee n'ont eu aucun effet significatif sur les gains avant et apres le sevrage. On conclut que la race, le sexe, le type de naissance et la parite influencait le gain quotidien moyen chez les moutons.