Effects of lamb sex and ewe parity on suckling-related neonatal behaviors and weaning weight of small-tailed han lambs

Suckling behavior is essential for the growth, health, and welfare of the lamb. The factors that influence the suckling-related behavior varied across breeds, and they remain unclear in Small-tailed Han lamb. This study aims to investigate the effects of ewe parity, lamb sex, and birth order on the suckling-related behaviors of Small-tailed Han lamb. The neonatal behaviors of 36 lambs were observed during the first week after birth using focal-animal sampling methods, and the levels of cholecystokinin (CCK), endogenous opioid peptides and growth hormone (GH) were measured with ELISA methods before weaning. Results showed that male lambs began standing and suckling behaviors earlier than female lambs, and the duration of each suckling bout was longer in male lambs ( P < 0.05). Lambs born to multiparous ewes more frequently suckled and attempted to stand earlier than lambs from primiparous ewes ( P < 0.05). The weaning weights of male lambs and lambs from multiparous ewes were heavier, and the serum levels of CCK, opioid peptides, and GH were sometimes higher in these lambs before weaning ( P < 0.05). Meanwhile, lamb birth order has no significant effect on the suckling-related behaviors of lambs ( P > 0.05). In addition, the suckling-related behaviors of male lamb and lambs born to multiparous ewes were found to strongly correlate with each other. In conclusion, lamb sex and ewe parity could affect the sucklingrelated behaviors and weaning weights of Small-tailed Han lambs. Moreover, male lambs and lambs born to multiparous ewes seemed to have better suckling-related behaviors. Many of these behaviors were highly connected with one another. These phenomena may be related to the higher serum levels of CCK, opioid peptides, and GH. The effects of lamb sex on suckling-related behaviors were different from those of other breeds in previous research. The male lambs were observed to initiate sucking-related behaviors earlier in this study. Our findings will also help in extensively understanding the variability in the effects of these factors on suckling-related behavior across sheep breeds.(c) 2022 Elsevier Inc. All rights reserved.