Response of plasma glucose, fructose and insulin to dietary glucose and fructose in the lactating sow

Twenty-two Hampshire-Yorkshire X Large White sows of second and third parity were allotted randomly to one of three dietary treatments. Five sows were fed 6.0 kg/day of a corn-soybean meal lactation diet (control diet). Twelve sows were fed the control diet in which 24% of the composition was supplied by corn syrup containing 72% fructose on a dry matter basis (fructose diet) and five sows were fed the control diet in which 24% of the composition was supplied by powdered dextrose (glucose diet). All diets were fed from days 1 through 21 of lactation. Blood was collected from all sows immediately prior to feeding and hourly for 6 hours postprandial via jugular vein cannulae following a single feeding on seven separate but nonconsecutive days during the 21-day period. Fructose was absorbed from the digestive tract of sows as evidenced by elevated (P less than 0.01) conventions of fructose in plasma. Sows fed the fructose diet also had higher (P less than 0.01) plasma glucose concentrations than did those fed the glucose and control diets. The concomitant elevated glucose concentration following ingestion of the fructose diet was not associated (P greater than 0.10) with increased insulin concentration. Fructose in plasma was associated with a slight but significant increase in insulin although the mean concentration of insulin in plasma was only one-third that measured in sows fed the glucose and control diets. These data suggest that fructose in vivo has a glucose-sparing effect presumably mediated through a physiological mechanism that lowers insulin concentration.