Interactions of starter starch and sodium butyrate for postweaned dairy calves: Growth performance, blood indices, and inflammation

In an earlier study, our team determined that sodium butyrate (SB) supplementation in calf starters with varying starch content impacts the growth performance, morphological and functional development of the rumen, and rumen microbiota in dairy calves during the preweaned period. The aim of this study was to assess the effects of SB supplementation in calf starters with varying starch content on the inflammation response of the rumen, liver, and systemic circulation, and growth performance in the postweaned period. In this study, 32 individually fed Holstein calves (39.4 ± 1.05 kg BW; 2 days of age) were fed following an experimental design with a 2 × 2 factorial arrangement of treatments: (1) a low-starch (270 g/kg DM) starter without SB supplementation, (2) a low-starch starter with SB supplementation (5 g/kg of dietary DM), (3) a high-starch (370 g/kg DM) starter without SB supplementation, and (4) a high-starch starter with SB supplementation. Calves were fully weaned on day 65 and data were collected thereafter; water, oat hay, and starter were offered ad libitum. Liver and rumen tissue were biopsied on day 65, and growth performance and blood samples were gathered on days 3, 7, 14, and 21 postweaned. Interactions between starter starch and SB supplementation significantly affected (P < 0.05) or showed tendencies (P < 0.10), particularly during postweaned day 1–3 on hay intake, average daily gain, and even feed efficiency. An instance of this interaction effect was observed when SB supplementation resulted in an increased average daily gain when incorporated with the low-starch starter, whereas a significant increase was not observed with the high-starch starter. Specifically, average daily gain was higher in the low-starch starter with SB supplementation group than in the other three groups (P < 0.05). These interactive responses corresponded with inflammation-related indices in the liver, rumen, and systemic circulation (blood). The indices included the Toll-like receptor 4-(nuclear factor kappa B (p65)-pro-inflammatory cytokines signaling pathway in the rumen and liver, along with lipopolysaccharide, lipopolysaccharide binding protein, and pro-inflammatory cytokines (interleukin-1β, interleukin-6, and tumor necrosis factor-α) within the rumen, liver, and blood (P < 0.05 or P < 0.10). This study underlines a noticeable interplay between starch and SB supplementation in calf starters, having significant implications on both the inflammatory response and growth metrics in weaned calves, chiefly during the vital initial postweaned period. These findings underscore the importance of implementing a carefully calibrated SB supplementation protocol that considers the starch levels and hay availability in calf starters to optimize health and growth outcomes.