Whole corn grain as fiber source for dairy calves: effects on performance, ruminal development and metabolism

Abstract

The objective of the study is to evaluate the supplementation of whole corn grain with the starter concentrate as a source of fiber on the performance, metabolism and ruminal development of Holstein dairy calves. Thirty - six Holstein calves will be used in a randomized complete block design, considering the weight of the calves at 28 d, when the supplementation is started. The animals will be housed in tropical shelters and divided into three treatments: 1) initial concentrate, 2) initial concentrate with the supplementation of whole corn from 28d of life and 3) initial concentrate with hay supplementation from the 28d of life. The duration of the experiment will be 84 days, with the first 28 days of life destined for adaptation, when the animals will receive 6 liters of whole milk per day and the conventional solid diet. After this period the volume of milk will be reduced 4 liters of whole milk per day for 28 days along with and the solid diet containing the conventional concentrate exclusively or with the supplementation of whole corn grain or hay. At 56 days of age, the animals will be weaned and evaluated for a further period of 28 days, when control animals will also receive hay ad libitum. For the evaluation of the corporal development calves will be weighted and corporal measures will be taken weekly. Blood samples will be collected weekly to analyze metabolic indicators for ruminal development. Samples of rumen fluid will be collected at weeks 4, 6, 8, 10 and 12 of life, 2h after morning feeding, using a oro-esophageal probe for ruminal pH determination, and the concentrations of short chain fatty acids and N-ammoniacal. Fecal samples will be collected at weeks 4, 6, 8, 10 and 12 of life for fecal pH measurement and subsequent analyzes of fecal starch. At 56d (weaning) 4 animals per treatment will be chosen randomly to be slaughtered. Rumens of all animals will be emptied, washed and weighed. Subsequently, samples of the ventral sac of the ruminal epithelium of each animal will be collected, to determine the mean number of papillae, the absorptive surface area, the mean area and height of the papillae, the thickness of the keratin layer and the mitotic index in the basal layer. The compartments of the large intestine will be separated, cleaned with running water and graded according to the incidence of lesions, based on a scale of 0 (no lesions) to 10 (ulcerative lesions throughout the cecum). The data will be analyzed as time-repeated measurements using the PROC MIXED SAS statistical package (version 9.0, SAS Institute Inc., Cary, NC). (AU)