Individual and interactive effects of multi-species probiotic and mineral biochar on growth performance and health status in Holstein suckling calves

Poor immune system and the incidence of gastrointestinal diseases are major challenges in the rearing of pre-weaning calves. Dietary supplementation with probiotics and biochar as feed additives could offer a promising strategy to mitigate these adverse conditions by potentially enhancing gut health and modulating the immune response. This study evaluated the effects of a combined dietary supplement of a multi-species probiotic and biochar on growth performance and health status in Holstein suckling calves over a 67-day period. Twenty-eight newborn female calves (initial body weight: 41.2 ± 3.8 kg) were randomly allocated to four experimental groups in a 2×2 factorial arrangement under a completely randomized design. The dietary treatments were as follows: 1) control (no additive), 2) probiotic (2 g/day per calf), 3) biochar (1% of dietary DM), and 4) probiotic + biochar (at the same levels as in treatments 2 and 3). The results demonstrated that weaning weight was significantly higher (P < 0.05) in calves receiving biochar compared to the control and probiotic-only groups. Dietary biochar supplementation also increased (P = 0.05) urinary allantoin excretion and microbial nitrogen synthesis. Serum albumin concentration was elevated (P < 0.05) in response to both probiotic and biochar supplementation. Furthermore, the inclusion of these additives significantly reduced (P < 0.05) rectal E . coli counts and improved fecal consistency scores. In conclusion, the simultaneous dietary inclusion of probiotic (2 g/calf/day) and biochar (1% of dietary DM) enhanced overall growth performance, microbial nitrogen synthesis, and key health indicators in Holstein suckling calves.