Feed intake patterns, growth performance, and metabolic and endocrine traits in calves fed unlimited amounts of colostrum and milk by automate, starting in the neonatal period.

Feed intake, growth performance, and metabolic and endocrine traits were studied in male calves fed unlimited (GrAL; n = 7) amounts of colostrum for 3 d after birth and mature milk up to d 28 and were compared with calves fed commonly recommended amounts of colostrum and milk (GrRS; n = 7). Calves were fed by automates, and software was available to continuously register the time points and amounts of ingested feed up to 11 d of age. Body weight was measured on d 1, 4, 7, 14, 21, and 28, and blood samples were taken on d 1, 2, 3, 7, 14, 21, and 28 to measure several metabolites and hormones. Feed intake of calves fed GrAL increased from d 1 to 4, then remained stable and was always higher than for calves fed GrRS. Total visits (visits with and without milk intake) were higher for GrRS than GrAL, but visits with milk intake were comparable between groups and meal sizes per visit with milk intake were greater in GrAL than in GrRS. Body weight gain was greater in GrAL than in GrRS in wk 1, but not later. There were significant group differences in plasma concentrations of albumin (GrRS > GrAL), nonesterified fatty acids (GrRS > GrAL), cholesterol (GrRS > GrAL; d 28), insulin (GrAL > GrRS), and cortisol (GrRS > GrAL), but not of immunoglobin G, urea, glucose, triglycerides, growth hormone, and glucagon. In conclusion, calves fed ad libitum were capable of ingesting very large amounts of colostrum and milk, even during wk 1 of life, accompanied by a greater body weight gain in GrAL in the first week, whereas in GrRS, the high number of visits without feed intake indicate that these calves reached no repletion. Compared with calves provided restricted amounts of feed, calves with free access to colostrum and milk were characterized by reduced plasma concentrations of nonesterified fatty acids and by a transiently enhanced insulin and reduced cortisol status.