Capsaicin improves immune status of lactating calves by modulating serum parameters and gut and upper respiratory microbiota. Bos taurus

Capsicum annuum is an herb of the genus Capsicum in the family Solanaceae and is used for medicinal purposes. Capsaicin (CAP) has been reported as the active component of red pepper, which has biological activities such as antibacterial, anti-inflammatory, antioxidant and stimulating small intestine development (Srinivasan, 2016). CAP antibacterial activity has been shown to be associated with Salmonella typhimurium, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Streptococcus pyogenes, Helicobacter pylori, Staphylococcus pyogenes and Aspergillus niger (Adaszek et al., 2019; Al-Delaimy & Ali, 1970; Xing et al., 2006). Experimental animal studies revealed that CAP reduced the incidence and severity of foot inflammation and also delayed the onset of adjuvant-induced foot inflammation in rats (Joe & Lokesh, 1997; Reddy & Lokesh, 1992). In addition, CAP inhibited the peroxidation reaction, and its inhibitory effect was stronger than that of a-tocopherol, a well-known antioxidant (Kogure et al., 2002). Therefore, the aim of this study was to evaluate the effect of CAP addition on antioxidant and immune capacity in lactating calves and to explore possible mechanisms by analyzing blood metabolites as well as gut and upper respiratory tract (URT) microbiota.