Effect of rearing system on pre-weaning growth, rumen development and its influence on post-weaning performance of lambs

Abstract. Twenty-four 21-day-old Balouchi male lambs were equally divided into two groups. Twelve subjects were artificially reared (AR), twelve others were ewe reared (ER) and used as control. AR in comparison of ER lambs maintained higher concentrations of blood beta- Hydroxybutyric acid (BHBA); however glucose concentration was not affected by rearing system. Unlike the DNA content and cell size, the RNA concentration and ribosomal capacity (Cs) of AR groups were significantly (P<0.05) higher than that of ER lambs. Rearing system did not affect morphologic characteristics of rumen wall except thickness of keratinized layer that was thickest in AR, 20 % less than in ER lambs (P<0.05). Stomach weight and capacity in AR animals were significantly (P=0.05) higher than ER lambs. Neither post-weaning growth rate nor feed conversion efficiency were affected (P>0.05) by rearing method. Also there were no differences with respect to slaughter and dissection data between groups in postweaning phase. In conclusion, the results of this study showed that naturally rearing system gave rise to developmental and carcass characteristics similar to those observed in artificial raised lambs.