Abstract:

Weaning stress in young ruminants is a comprehensive physiological response induced by multiple factors during the weaning period, including mother–offspring separation, sudden dietary changes, and environmental reorganization. It triggers psychological, physiological, and immune stress responses, thereby exerting both immediate and long-term effects on growth performance and the immune system. This paper systematically elaborates on the detrimental effects of weaning stress from three aspects. Regarding production performance, abrupt (one-step) weaning and inappropriate weaning timing—such as failing to meet the required age, body weight, or feed intake—lead to a sharp decline in feed consumption, stagnation or even negative growth in body weight, and delayed market weight. Concerning digestive and absorptive function, the abrupt transition from a milk-based diet (lactose and milk fat) to solid feeds results in decreased activities of key digestive enzymes, including amylase and trypsin, impaired intestinal barrier integrity, increased intestinal permeability, poor digestion and absorption, and exacerbated oxidative stress. In terms of immune function, the withdrawal of passively transferred immunoglobulins, lysozyme, and other protective factors from maternal milk, coupled with an immature active immune system and social stress arising from environmental reorganization, leads to an overall decline in disease resistance and significantly increases the risk of respiratory and digestive tract infections. To address these issues, this paper proposes three mitigation strategies. In pharmacotherapy, given the context of antibiotic prohibition, dietary supplementation with appropriate Chinese herbal medicines or plant extracts provides a safe and effective alleviation approach. Single compounds such as Astragalus aqueous extract and astragaloside IV can enhance immune and antioxidant capacity and improve average daily gain. Compound formulations (e.g., Astragalus–angelica–glycyrrhiza) can reduce cortisol levels, repair intestinal mucosa, improve mucosal morphology and intestinal health, while fucoidan and eugenol can elevate digestive enzyme activities and antioxidant levels. In nutritional regulation, scientifically formulated concentrate-to-forage ratios promote rumen development, and the use of rapeseed meal and cottonseed meal as partial replacements for soybean meal ensures protein supply. Supplementation with composite probiotics, including Lactobacillus and Bifidobacterium species, modulates gut microbiota and improves immune function and nutrient absorption. For animals exhibiting pronounced stress responses, electrolyte and glucose supplementation effectively alleviates digestive disturbances and growth suppression. In management optimization, maintaining stable pen temperature and humidity, controlling stocking density, regular disinfection, and minimizing unnecessary stressful procedures such as regrouping and transport are essential. Adoption of gradual weaning protocols, based on age, body weight, and feed intake thresholds, avoids the severe impact of abrupt weaning. In the early weaning phase, housing calves in pens adjacent to dams with continued visual and olfactory contact can alleviate separation anxiety and psychological stress, thereby improving weight gain and health status. During the transition period, the ratio of milk replacer to starter feed should be adjusted progressively to avoid sudden feed changes. In conclusion, weaning stress is a systemic issue arising from the synergistic action of multiple factors. The integrated application of alternative pharmacotherapies, nutritional regulation, and management optimization can systematically mitigate its negative effects on young animal growth and health, providing practical references for healthy ruminant production.

Key words: Weaning stress, Ruminant animals, Growth performance