EFFECT OF AGE AT WEANING (30 VS 60 DAY) ON INTAKE, GROWTH, SERUM HORMONE AND METABOLITE PROFILES IN YOUNG EWE AND RAM LAMBS

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 gr oup to be weaned at either 30 (EW) or 60 (LW) d of age. Six lambs (thr ee 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 fo llowing weaning and up through weaning of LW lambs. Throughout the stu dy, 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 concentrati ons (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 gre ater (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 v alues were lower (P < 0.05) in EW lambs than LW Lambs, and rams had lo wer (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 h ormones 1 wk postweaning, whereas weaning at 60 d of age had no appare nt 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.