Effect of plane of milk replacer intake and age on glucose and insulin kinetics and abomasal emptying in female Holstein Friesian dairy calves fed twice daily.

The objective of this study was to investigate how preweaning plane of milk replacer intake and age can affect insulin and glucose kinetics as well as abomasal emptying rate in dairy calves fed twice a day. A total of 12 female Holstein Friesian calves were blocked by cow parity, paired by colostrum origin, and were randomly assigned to a high plane of milk replacer intake (8 L/d, 1.2kg of milk replacer/d; n=6) or a low plane of nutrition (4 L/d, 0.6kg of milk replacer/d; n=6). All calves received 4 L of colostrum over 2 meals (1 and 6h after birth) and were then directly transferred to their assigned feeding plans until they were stepped-down from milk by 50% during wk 7 and weaned on wk 8. Milk replacer (24% crude protein, 18% crude fat) was fed at 150g/L twice daily (0700 and 1700h) and all calves had ad libitum access to pelleted calf starter, chopped wheat straw, and water. Jugular catheters were placed in all calves at 4, 7, and 10wk of age. Then, postprandial response to plasma glucose, insulin, and acetaminophen (supplied with the meal) were determined to measure abomasal emptying. The next day, a glucose tolerance test was conducted by infusing glucose via the jugular catheter. At 4 and 7wk of age, the rate constant (%/h) for abomasal emptying of the meal was lower in high calves (0.21±0.02 in wk 4; 0.27±0.02 in wk 7) compared with low (0.34±0.02 in wk 4; 0.47±0.02 in wk 7). The postprandial plasma insulin area under the curve over 420min was greater in high calves (18,443±7,329; low=5,834±739 µU/mL) compared with low. We found no differences in glucose tolerance test kinetics between the high and low dairy calves at 4, 7, or 10wk of age. The findings from this study suggest that feeding dairy calves an elevated plane of nutrition in 2 meals of milk replacer per day does not decrease insulin sensitivity.