Replacement of dry ground corn with reconstituted corn grain silage in the starter concentrate of dairy calves

Thirty-six newborn Holstein calves were used in a randomized block design and allocated to the following groups: 1 ??? starter concentrate based on ground corn grain, soybean meal, wheat bran and premix of minerals and vitamins (Control); and 2 ??? the same diet composition, but ground corn replaced with reconstituted corn grain silage (RCGS). Calves were fed 6 l/day of whole milk and had free access to water and concentrate. Calves were weaned from day 57 to 63 and fed hay ad libitum until 70 days of age. The period from birth to 56 days of age was called pre-weaning and from day 57 to 70 ??? the transition period. On day 70, five animals/treatment were slaughtered to assess ruminal development. Dry matter intake (DMI) and health problems were recorded daily, while weight and blood samples were collected weekly. Ruminal fluid was collected at weeks 8 and 10. Replacing corn grain with RCGS resulted in greater feed efficiency (FE) at pre-weaning (0.71 vs 0.66). Concentrate DMI was higher for control during the transition period (303 vs 256 g/day). Control calves presented higher faecal scores throughout the study. The control diet resulted in higher concentrations of isovaleric and isobutyric acids and ammonia-N at week 8. RGCS increased glucose levels, but decreased total protein concentration during the whole evaluation period. Feeding RCGS was efficient during the pre weaning period; however, it decreased intake during the transition period. Data from a longer feeding period after weaning are needed to evaluate the effects of a highly digestible starch source in the diet of young calves.