Effect of Butyric Salt Supplementations, as Metabiotics, on Rumen Functions in Pre-Weaned Dairy Calves

Rumen development is critical for optimal growth, feed efficiency and health in pre-weaned dairy calves. Butyric acid, a short-chain fatty acid produced in the rumen, has been shown to stimulate epithelial development and modulate immune responses. This study evaluated the effects of butyric salt supplementations, as metabiotics, on rumen morphometry and investigated the potential associations with feed intake, growth performance and health indicators in pre-weaned dairy calves. Thirty calves were randomized into three groups: controls (G1), 25 g (G2) or 50 g (G3) sodium butyrate from birth until weaning. The gross and histological rumen morphometry, dry matter intake, growth performance, complete blood count, total protein determination and fecal (oo)cyst counts for <i>Giardia</i> spp. and <i>Eimeria</i> spp. were analyzed using one-way ANOVA. When significant effects were detected, treatment means were compared using Tukey's HSD at <i>p</i> ≤ 0.05. Sodium butyrate supplementation produced dose-dependent responses. Compared with controls (<i>p</i> ≤ 0.05), G3 calves had a greater mean papillae height (3.20 vs. 1.36 mm) and rumen wall thickness (7.08 vs. 3.62 mm), higher final body weight (93.9 vs. 80.1 kg), increased daily weight gain (798 vs. 550 g/day), increased total dry matter intake (69.4 vs. 55.1 kg) and improved feed conversion ratio (1.45 vs. 1.67). In addition, G3 calves showed reduced <i>Giardia</i> and <i>Eimeria</i> (oo)cyst excretions and favorable hematological shifts at weaning (i.e., higher hematocrit, hemoglobin and mean corpuscular hemoglobin concentration and altered leukocyte differentials) consistent with improved health. In conclusion, sodium butyrate supplementation in pre-weaned dairy calves resulted in dose-dependent improvements in rumen morphometry, voluntary dry matter intake and growth performance. These physiological benefits were accompanied by decreased <i>Giardia</i> spp. and <i>Eimeria</i> spp. (oo)cyst shedding and by positive shifts in hematological health indicators, suggesting a potential enhancement of the animals' immune response.