The high mortality of lambs has always restricted the development of Small-tailed Han sheep breeding, causing serious economic losses and welfare problems in the sheep breeding industry. Stable and good-quality maternal behavior is critical for the survival of offspring, and given the importance of maternal behavior on early lamb survival, improving maternal behavior in ewes seems to be an effective way to improve lamb survival rates. Thus, exploring the factors that influence maternal behavior is a good place to begin. Therefore, in this study, we investigated the effects of parity, litter size, and lamb sex on the maternal behavior of Small-tailed Han sheep. The neuroendocrine mechanism involved in regulating maternal behavior were also analyzed. Primiparous and multiparous ewes, ewes with different litter sizes, and ewes with different lamb sexes were selected, and their maternal behaviors, including lactating, grooming, following, looking, and udder refusal, were observed and analyzed using scanning and sampling methods during the first 7 days after parturition. The lambs’ body weights were recorded for the first 35 days after birth. The concentrations of estradiol, oxytocin, norepinephrine, dopamine, NO, and γ-aminobutyric acid (GABA) of ewes were measured with ELISA kits for 35 days after parturition. The results showed that the looking and udder refusal behavior of multiparous ewes was significantly lower than primiparous ewes (P = 0.004 and P = 0.036). The grooming behavior was significantly higher in both primiparous and multiparous ewes at Day 0 than at Day 1∼7 after parturition (P < 0.05). Ewes with two offspring expressed significantly more lactating behavior than ewes with single lambs in the first 3 days after parturition (P < 0.05). The looking behavior was significantly lower in twin-lambing ewes than in single-lambing ewes at Day 7 postpartum (P = 0.031). The grooming behavior was significantly higher in both single and twin lambing ewes at Day 0 post parturition than at Day 1∼7 post parturition (P < 0.05). Lactation behavior was significantly higher in ewes producing female lambs than in ewes producing male lambs at Day 2 after parturition (P = 0.018). When a female lamb was born, the looking behavior of ewes was significantly higher than ewes with male lambs on Day 3 after parturition (P = 0.01). The grooming behavior and the udder refusal behavior of male lambing ewes were significantly higher at the Day 0 after parturition than at the Day1∼7 after parturition, similar temporal trend was observed in female lambing ewes (P < 0.05). The body weight of lambs was higher in the multiparous ewes group. This was especially significant at Day 0 and Day3 after birth (P = 0.045 and P = 0.007). Single lambs seemed to have higher birth weights than twin lambs; however, the differences were not significant (P > 0.05). Male lambs were significantly heavier than female lambs at Day 0 and Day 7 after birth (P = 0.044 and P = 0.048); thereafter, the lambs of the two groups showed no significant difference in body weight. The level of oxytocin in multiparous ewes was significantly higher than that of primiparous ewes (P < 0.05). The levels of oxytocin, norepinephrine, dopamine, NO, and GABA in ewes with twin lambs were significantly higher than those of ewes with single lambs (P < 0.05). Ewes with female lambs had a significantly higher level of oxytocin than ewes with male lambs at Day 0 (P = 0.024). In conclusion, multiparous ewes exhibited better quality maternal behavior than primiparous ewes, and this was associated with the level of oxytocin in the serum. Ewes with twin lambs exhibited better quality maternal behaviors than the single lamb group, and this was related to the levels of oxytocin, norepinephrine, dopamine, NO, and GABA. Oxytocin was also found to be associated with the improved ewe maternal behavior with female lambs. Altogether, ewes with better maternal behavior have a higher level of oxytocin and noradrenaline. Moreover, the expression of maternal behavior in ewes is positively correlated with lamb weight. Our findings contribute the understanding of the neuroendocrine mechanisms of maternal behavior in Small-tailed Han sheep and provide a theoretical basis for the further exploration of artificial methods to improve ewe maternal behavior, and ultimately improve the survival rate and welfare of lambs.

羔羊的高死亡率一直制约着小尾寒羊养殖的发展，给养羊业造成严重的经济损失和福利问题。稳定和优质的母性行为对于后代的生存至关重要，鉴于母性行为对早期羔羊存活的重要性，改善母羊的母性行为似乎是提高羔羊成活率的有效途径。因此，探索影响母亲行为的因素是一个很好的起点。因此，在本研究中，我们调查了胎次、窝产仔数和羔羊性别对小尾寒羊母性行为的影响。还分析了参与调节母体行为的神经内分泌机制。初产和经产母羊，不同窝产仔数的母羊，选择不同羔羊性别的母羊，在分娩后的前7天，采用扫描和采样的方法观察和分析其母性行为，包括泌乳、梳理、跟随、寻找和拒绝乳房。在出生后的前 35 天记录羔羊的体重。分娩后35天，用ELISA试剂盒测定母羊雌二醇、催产素、去甲肾上腺素、多巴胺、NO和γ-氨基丁酸（GABA）的浓度。结果表明，经产母羊的拒乳行为显着低于初产母羊（P=0.004和P=0.036）。初产和经产母羊在分娩后第 0 天的梳理行为均显着高于分娩后第 1~7 天（P < 0.05）。在分娩后的前 3 天内，有两个后代的母羊的泌乳行为明显高于单只羔羊的母羊（P < 0.05）。在产后第 7 天，双生母羊的外观行为明显低于单生母羊（P = 0.031）。单胎和双胎母羊在分娩后第 0 天的梳理行为均显着高于分娩后第 1~7 天（P < 0.05）。在分娩后第 2 天，产雌性羔羊的母羊的泌乳行为明显高于产雄性羔羊的母羊（P = 0.018）。当母羊出生时，母羊在分娩后第 3 天的观察行为显着高于雄性羊（P = 0.01）。产后第0天雄性产羔羊的理毛行为和拒乳行为显着高于产后第1～7天，雌性产羔羊的时间趋势相似（P < 0.05）。经产母羊组的羔羊体重较高。这在出生后第 0 天和第 3 天尤为显着（P = 0.045 和 P = 0.007）。单头羔羊的出生体重似乎比双胞胎羔羊高；但差异不显着（P > 0.05）。公羊羔在出生后第 0 天和第 7 天明显比母羊重（P = 0.044 和 P = 0.048）；此后，两组羔羊的体重均无显着差异。经产母羊催产素水平显着高于初产母羊（P < 0.05）。双胎母羊的催产素、去甲肾上腺素、多巴胺、NO、GABA水平显着高于单胎母羊（P < 0.05）。在第 0 天，母羊母羊的催产素水平显着高于公羊母羊（P = 0.024）。总之，经产母羊比初产母羊表现出更好的母性行为，这与血清中的催产素水平有关。双胎的母羊表现出比单羊组更好的母性行为，这与催产素、去甲肾上腺素、多巴胺、NO 和 GABA 的水平有关。还发现催产素与改善母羊的母羊行为有关。总之，母性行为较好的母羊催产素和去甲肾上腺素水平较高。而且，母羊母性行为的表达与羔羊体重呈正相关。我们的研究结果有助于了解小尾寒羊母性行为的神经内分泌机制，为进一步探索人工方法改善母羊母性行为，最终提高羔羊的成活率和福利提供理论依据。