Effects of Weaning Age on Plasma Biomarkers and Growth Performance in Simmental Calves

Simple Summary Weaning plays a vital role in the management strategy of a dairy farms, also affecting the future animals' performances, such as growth, reproduction, and lactation. At the same time weaning strategy, as days at weaning, influences the feeding cost as milk supply during the pre-weaning period reaches 40% of the total feed costs. The aim of the study was to investigate the effects of weaning age, conventional (60 days) or early (45 days) on growth performances and inflammometabolic status of ten Simmental calves. The proposed results showed how early weaning strategy seemed to not affect inflammatory status and liver functionality after weaning, highlighting the possibility to reduce rearing costs but not jeopardizing calf development, as long as calves can reach body gains as reported in the present study. At least for performance, we are aware that the low number of calves enrolled in each treatment can limit the recommendations based on our findings. Hence, this study should be considered more like an explorative investigation since no recent data are available for Simmental calves in terms of growth performance and inflammometabolic adaptation. Weaning plays a key role in health status and future performance of calves. The aim of this study was to investigate the effects of weaning age (Wa), early (45 d, EW) or conventional (60 d, CW), on growth performance and metabolic profile of ten Simmental calves (5 EW and 5 CW calves). Daily intake of milk and calf starter was recorded. Blood samples and measurements of body weight (BW), heart girth (HG), and wither height (WH) were collected at -25, -15, 0, 6, and 20 days relative to weaning. Growth performances (BW, HG, WH) were affected by Wa, resulting lower in EW calves compared with CW calves (p < 0.05). Average daily gain was affected by overall Wa and Time but also by the interaction Wa x Time (p < 0.05). EW calves had lower paraoxonase and higher oxidation protein products levels, lower glucose levels in the post-weaning period, lower Ca and cholesterol levels at 20 d after weaning, and higher GGT activity at -25 d from weaning (p < 0.05). A significant interaction effect between Wa and Time was reached for glucose, Ca, cholesterol. In conclusion, weaning Simmental calves at approximately six weeks of age might not affect inflammatory status and liver functionality after weaning. As secondary outcome, even though the low number of animals could represent a limitation, the average daily gain obtained by Simmental calves weaned at 45 d supported this strategy (despite the lower body weight at weaning and after was due only to the age difference of 15 days). Hence, in order to reduce rearing costs, early weaning for Simmental calves (dual-purpose breed, milk and beef) might not jeopardize calf development, as long as calves can reach body gains as reported in the present study.