Effect of a mixture of short and medium chain fatty acids esterified to glycerol in milk replacer on weaning calves rumen papillae development

The supplementation of sodium butyrate in milk replacers (MR), commonly used to anticipate weaning, affects both small intestine and rumen development, determining earlier solid feed intake which leads to better performances in cattle. The present study aims to determine the effects of a mixture of short and medium chain fatty acids esterified to glycerol (SMCFA) added to MR on rumen papillae development of weaning calves offered starter diet at libitum. Eight bull calves (10-days-old) were divided in two balanced groups: Control (C) and Treated (T). The latter received 0.2% SMCFA in MR besides starter diet. Animals were slaughtered at the age of 72 days. Histomorphometric analysis performed on samples from the cranio-dorsal sack of the rumen did not indicate differences in the mean number of papillae or in their total surface/cm2 of mucosa but rather in their shape. T group had more wide, short tongue-like or irregular shaped papillae and many interposed papillae compared to C group whose narrow, tongue-to-finger-like papillae, often showed secondary papillae or irregular branches. In T group, enhanced proliferation of the epithelial cells of the stratum basale, spinosum and granulosum was observed in the interpapillar region, while C group showed more cellular layers in the stratum corneum at the base of the papillae and in the interpapillar region. SEM analysis confirmed the different morphology of the papillae in the two groups and, at high magnification, revealed the presence of more dense cytoplasmic protrusions covering horn cell surfaces in T group.