Diet induced ruminal papillae development in neonatal calves not correlating with rumen butyrate

The objective of this study was to investigate the development of rumen mucosa and the level of plasma IGF-1 in calves induced by different amounts and types of milk replacers and solid diet. Forty-five male Holstein calves 7 days of age were assigned to three groups: group I milk free replacer, late weaned; group II milk free replacer, early weaned, and group III milk replacer, early weaned. All animals received additional concentrate, water and maize silage were offered ad libitum. In each group, three calves were slaughtered at 41 days of age. The concentration of ruminal total SCFA and the molar proportion of butyrate did not differ between the groups, but the molar proportion of acetate was lower ( P = 0.01) and the proportion of propionate was higher ( P = 0.02) in early weaned calves. Compared to the late weaned calves ( group I) the length, width and surface of the papillae of atrium ruminis, the length and width of the papillae of ventral ruminal sac and the length of the papillae of ventral blind sac were greater ( P < 0.05) in the early weaned calves fed low amounts of milk and high amounts of concentrate ( group III). Furthermore, there was a tendency of plasma IGF-1 concentration to be increased ( P = 0.1) in early weaned calves. The plasma levels of glucose and insulin were decreased ( P < 0.01, and P = 0.03, respectively). Positive correlations existed between papillae length and plasma IGF-1 concentrations ( P < 0.10). Insulin and glucose concentrations were negatively correlated with parameters of papillae development ( P < 0.1). In conclusion, the development of rumen papillae was stimulated in calves consuming increased amounts of concentrate. The effect was not correlated with the molar proportion of butyrate, but with the molar propionate proportion in the rumen and with the plasma IGF-1 concentration.