Reconstituted versus dry alfalfa hay in starter feed diets of Holstein dairy calves: Effects on growth performance, nutrient digestibility, and metabolic indications of rumen development.

We investigated the effect of reconstitution of alfalfa hay on starter feed intake, nutrient digestibility, growth performance, rumen fermentation, selected blood metabolites, and health criteria of dairy calves during the pre- and postweaning periods. A total of 20 newborn male Holstein calves (3 d of age; 40.3 ± 1.30 kg of body weight; ±SE) were assigned randomly to 1 of 2 treatments, a starter feed containing either 10% dry (AH) or reconstituted alfalfa hay (RAH), each consisting of 10 calves. Alfalfa hay was reconstituted with water 24 h before feeding to achieve a theoretical dry matter content of 20%. Both starter feeds had the same ingredients and nutrient compositions but differed in their dry matter content (91.2 and 83.8% dry matter for AH and RAH, respectively). Calves were weaned on d 50 and remained on the study until d 70. All calves had free access to fresh and clean drinking water and the starter feed at all times. During the study period, the average maximum temperature-humidity index was 73.8 units, indicating no degree of environmental heat load for dairy calves. Starter feed dry matter intake, total dry matter intake, and body weight (at weaning and at the end of the trial) were unaffected by treatment. Nutrient intake (except for total ether extract intake) increased during the postweaning period compared with the preweaning period. Average daily gain and feed efficiency were unchanged between treatments. Calves had higher average daily gain and skeletal growth during the postweaning period; however, feed efficiency was lower during the post- versus preweaning period. Calves fed RAH gained more hip width and body barrel compared with calves fed AH during the preweaning and all studied periods, respectively. Rectal temperature was similar between treatments, but feeding RAH decreased fecal score and general appearance score during the preweaning period. Apparent total-tract nutrient digestibility was not affected by reconstitution of alfalfa hay; however, reconstitution increased total-tract digestibility of neutral detergent fiber during the postweaning period. Ruminal fluid pH, and concentrations and profile of total volatile fatty acids were unchanged between treatments. Molar concentration of propionate and acetate to propionate ratio increased and decreased, respectively, during the postweaning period. Reconstitution of alfalfa hay did not affect concentrations of glucose, β-hydroxybutyrate, blood urea N, and albumin, and albumin to globulin ratio during the studied periods; however, reconstitution increased concentration of blood total protein during the overall period. Calves had higher concentrations of blood glucose and globulin during the preweaning and β-hydroxybutyrate during the postweaning period. Overall, reconstitution of alfalfa hay did not interact with calf phase (pre- vs. postweaning) to affect dry matter intake, growth performance, and metabolic indications of rumen development (measured as ruminal volatile fatty acids and selected blood metabolites), but improved health-related variables (fecal score and general appearance score) during the preweaning period.