Rumen fermentation, blood metabolites, and growth performance of calves during transition from liquid to solid feed: Effects of dietary level and particle size of alfalfa hay

This study evaluated the effects of particle size (PS) and dietary level of alfalfa hay (All) on rumen fermentation parameters, blood metabolites, eating behavior, and growth performance in dairy calves during transition from liquid to solid feed. Sixty newborn dairy calves (41 +/- 2.5, kg of body weight) were used in a 2 x 2 factorial arrangement with the factors dietary All level (medium, 12.5%, or high, 25%, on DM basis) and PS (fine -= 1 mm or medium = 3 mm, as geometric means) of AH. Hence, the dietary treatments were (1) medium level of All with fine PS (M-FPS), (2) medium level of All with medium PS.(M-MPS), (3) high level of All with fine PS (H-FPS), and (4) high level of All with medium PS (H-MPS). Particle size of All did not affect total DMI (TDMI) during the preweaning period, although TDMI was greater for calves fed MPS than in those fed FPS during the postweaning and overall periods. Calves fed MPS spent more time eating solid feed and ruminating and less time on nonnutritive oral behaviors compared with FPS calves. The dietary level of All did not affect behavioral parameters. Average daily gain of calves was not affected by dietary treatment before weaning. During the postweaning and overall periods, average daily gain was greater in calves fed MPS than in those fed FPS at the 25% All level, but this effect was absent with 12.5% All. Furthermore, the rumen pH values on d 35 and 70 of the study were greater for MPS than for FPS, regardless of the dietary level of AH.,Effects of All level, PS, and their interaction did not affect blood glucose concentrations in developing calves. These results indicate that feed intake, feeding behavior, rumen fermentation parameters, and blood beta-hydroxybutyrate concentration may be affected by rations differing in forage PS; thus, providing calves with MPS can improve calf performance and reduce their nonnutritive oral behaviors.