Effects of feeding milk replacer once versus twice daily on glucose metabolism in Holstein and Jersey calves.

Eighteen Holstein (experiment 1) and 15 Jersey (experiment 2) heifer calves were fed milk replacer once or twice daily to determine effects of feeding frequency on weight gain, starter intake, and glucose metabolism. Body weights were measured weekly from birth to 8 wk. Blood samples were collected at wk 1 through 6 from all calves before and at 30, 60, 90, 120 and 180 min after the morning feeding. Plasma was analyzed for glucose, insulin, glucagon, and nonesterified fatty acids (NEFA). Urine was collected 90 min postfeeding to measure glucose concentration. Treatment did not affect mean starter intake or body weight. In experiments 1 and 2 mean plasma glucagon, glucose, NEFA, and insulin and urinary glucose concentrations were not affected by treatment. There was an interaction of sampling time and treatment for plasma insulin concentrations but not for glucose concentrations in both experiments. Following feeding, calves fed milk replacer once daily had higher insulin concentrations than those fed twice daily. There was an interaction of sampling time and treatment for plasma NEFA concentrations in Jersey calves only. Jersey calves fed milk replacer once daily had higher plasma NEFA concentrations before the morning milk replacer feeding. At wk 3 and 6, frequently sampled intravenous glucose tolerance tests were performed to assess glucose effectiveness, insulin sensitivity, and acute insulin response. In experiments 1 and 2 glucose effectiveness and insulin sensitivity were similar regardless of milk replacer feeding frequency. In Holstein and Jersey calves fed milk replacer twice daily, acute insulin response was greater than in calves fed once daily. However, insulin sensitivity decreased with age, while acute insulin response increased with age. These data suggest that feeding calves milk replacer once daily did not deleteriously affect performance or glucose metabolism regardless of breed.