Effects of melatonin implants in late gestation and at lambing on colostrum and milk quality of ewes, birth temperature and growth performance of their lambs

Abstract

The objective of this study was to measure the effects of melatonin implants in meat ewes at late pregnancy, at lambing, or both, on colostrum and milk composition, growth of their lambs, and lamb surface and rectal temperatures under intensive conditions. Pregnant Rasa Aragonesa ewes, that were previously synchronized (mean parity number ( ± SD): 2.50 ± 0.82, mean live weight: 55 ± 4 kg; mean body condition: 3.00 ± 0.25) received a subcutaneous melatonin implant thirty days before lambing (M-0, n = 14), at lambing (0-M, n = 14), at both periods (M-M, n = 10), or did not receive an implant (0–0, n = 12). Mean ( ± SD) prolificacy (number of lambs born/lambing) was 1.43 ± 0.14; 1.57 ± 0.13; 1.40 ± 0.16, and 1.42 ± 0.14 for the M-0, 0-M, M-M and 0–0 groups, resp. The distribution of lambs born according to their sex was: M-0, 7 males, 12 females; 0-M, 10 males, 11 females; M-M, 6 males, 7 females, and 0–0, 8 males, 6 females. Fat (F), protein (P), and lactose (L) content were measured in colostrum (collected at lambing) and milk (collected every two weeks), and ºBrix and IgG were quantified in colostrum. Lamb weight (LW) was recorded at birth and every two weeks until weaning (day 42 of age). At birth, lamb rectal temperature (RT) and thermography images were taken (Eye=ET; shoulder=ST; mid loin=MT; hips=HT). P and L concentrations in colostrum were significantly (P < 0.05) higher in the M-0 (P: 9.01 ± 0.45, L: 8.53 ± 0.42%) than they were in the M-M group (P: 7.38 ± 0.34, L: 6.99 ± 0.32), with no significant differences among groups for F content. No significant differences were found for birth weight among groups, as well as considering litter size. However, at weaning, male lambs reared by 0-M (12.31 ± 0.57 kg) ewes had significantly (P < 0.05) higher LW than did male lambs reared by M-0 (9.43 ± 1.01) or 0–0 (9.65 ± 0.99 kg) ewes. Lambs from M-0 and M-M ewes had the highest MT and HT, and the effects were most pronounced in male lambs. In conclusion, melatonin implants during pregnancy had positive effects on ewes by improving colostrum quality, and increased the MT and HT in lambs. Implants at lambing enhanced the productive performance of ewes and male lambs, but implants at both moments did not provide beneficial effects.