Effect of age at weaning (30 vs. 60 day) on intake, growth, serum hormone and metabolite profiles in young ewe and ram lambs

Abstract

Twenty-four Polypay lambs (12 sets of twins; 12 ewe and 12 ram lambs) born within a 3-d period were randomly allotted at birth within sex group to be weaned at either 30 (EW) or 60 (LW) d of age. Six lambs (three ewe and three ram lambs)/treatment were intensively bled at 30, 37, 60, and 67 d of age. Feed intake was higher (P < 0.05) in EW lambs following weaning and up through weaning of LW lambs. Throughout the study, BW were similar (P > 0.10) between treatments; however, ram lambs were heavier (P < 0.05) than ewe lambs beginning at 18 d of age. At 37 d of age, EW lambs had lower (P < 0.05) insulin and IGF-I concentrations (P = 0.10), and greater (P < 0.05) GHmn values than LW lambs. Ram lambs had greater (P < 0.05) serum GHmn, GHbl and GHam values, and greater (P < 0.05) serum insulin and IGF-I concentrations than ewe lambs at 30, 60, and 67 d of age. At 37 d of age, EW lambs had lower (P < 0.05) insulin:GH ratios than LW lambs. At 37 d of age, PRLmn and PRLam values were lower (P < 0.05) in EW lambs than LW Lambs, and rams had lower (P < 0.05) PRLam values than ewe lambs. The results indicate that weaning at 30 d of age is associated with major changes in metabolic hormones 1 wk postweaning, whereas weaning at 60 d of age had no apparent effect on hormonal patterns postweaning. Differences between EW and LW lambs may reflect early postweaning feed intake, along with stage of rumen development at weaning. Key words: Lambs, growth, hormones, weaning, metabolites