Effect of Growth Hormone on Glucose, Nonesterified Fatty Acid and Insulin Levels, and on Glucose Utilization in Dairy Calves

Bovine growth hormone (1 mg/kg/day) and a comparable volume of saline were injected intramuscularly once daily for 5 consecutive days to 6 treated and 7 control 130-day-old dairy calves. Comparative treatment effects on blood and plasma glucose, plasma nonesterified fatty acid and plasma insulin concentrations, and on glucose utilization rate from 14C-glucose constant infusions were studied 16 hours postfeeding and post-treatment. Blood and Plasma nonesterified fatty acids increased altered by growth hormone treatment. Plasma nonesterified fatty acids increased following the first injection, reached a maximum on the second day, and declined to pretreatment concentration by the fifth day; whereas, the concentration declined slightly throughout the 5-day comparison in control calves. Growth hormone treatment did not change glucose utilization rate, since the adjusted difference between treated and control calves was only 1.8% and not significant. Similarly, fasting plasma insulin concentration remained relatively constant throughout the comparison in treated and control calves. Sustained effects of growth hormone treatment on carbohydrate metabolism were not demonstrable in the 16-hour post-feeding and post-treatment ruminant although the lipolytic effect was observed.