Impact of Bacillus Licheniformis supplementation on growth performance, health status, and oxidative stress in male dairy calves during the weaning transition period

This study evaluated the effects of Bacillus licheniformis (BL) supplementation on growth performance, health status, blood metabolic parameters, inflammatory responses, and intestinal permeability in Holstein dairy calves during the weaning transition. Sixteen male Holstein calves, averaging an initial body weight (BW) of 60 ± 5.0 kg at 35 days of age, were divided into two groups: a control group (milk replacer without BL) and a BL-supplemented group (milk replacer with 0.5 g of BL per head per day). The calves were weaned on day 75 (d 75) and monitored until day 90 (d 90). Results indicated that BL supplementation significantly increased average daily gain (ADG) (P < 0.05), although it did not affect starter intake, hay intake, BW, or feed efficiency (P > 0.05). Notable increases in withers height on days 75 and 89 (P < 0.05), and body circumference on day 65 were observed (P < 0.05). Conversely, a decrease in body length was noted on days 50 and 65 (P < 0.05). Immunological activity improved in the BL-supplemented calves, demonstrated by elevated levels of IL-10 and IgG (initially) (P < 0.05), and a decrease in TNF-α concentration by day 14 (P < 0.05). Additionally, BL supplementation enhanced catalase (CAT) levels on days 3 and 14, and malondialdehyde (MDA) on days 1 and 7(P < 0.05), with a notable reduction in fecal MDA concentrations on day 7 (P < 0.05). In conclusion, BL supplementation not only enhanced growth performance and immune function but also bolstered antioxidant capacity and mitigated intestinal oxidative stress in dairy calves during the weaning transition.