Effects of Dietary Lactoferrin–Osteopontin Complexes on Immune Function, Intestinal Health and Microbiota Composition in Kittens

Abstract

Simple Summary Young kittens have developing gastrointestinal and immune systems, which may increase their susceptibility to environmental stress and infection. Lactoferrin (LF) and osteopontin (OPN) are bioactive milk proteins with complementary antimicrobial and immunoregulatory activities and roles in intestinal-development functions; they, and that can associate to form an LF-OPN complex. In this study, 16 British Shorthair kittens received either a basal diet or the same diet supplemented for 28 days with a commercial LF-OPN preparation (LF:OPN mass ratio, 8:1; 240 mg/kg body weight). Supplementation did not adversely affect growth. Kittens receiving LF-OPN had higher serum immunoglobulin M, lower tumor necrosis factor-α, improved antioxidant indices, a higher proportion of circulating CD4+ lymphocytes, and a higher CD4+/CD8+ ratio. The preparation also selectively altered fecal bacterial taxa, decreasing Enterobacteriaceae and Escherichia-Shigella while enriching several taxa identified by LEfSe, although overall microbial diversity and fecal short-chain fatty acid concentrations remained unchanged. Whole-blood transcriptomics analysis identified changes in immune-related pathways, but these exploratory findings need independent verification. These observed changes support further evaluation of the LF-OPN complexes as a promising functional ingredient in kitten nutrition. Because LF-only, OPN-only, and uncomplexed LF + OPN groups were not included, the contributions of the individual proteins and any synergistic effect cannot be determined.