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For piglet survival and performance after weaning, birth weight and litter uniformity are crucial. One way that may improve piglet birth weights and litter uniformity could be insulin-stimulating sow diets before mating, but the physiological mechanisms involved are not clear. The aim of this study was to evaluate the effects of different levels of insulin-stimulating feed components (dextrose plus starch; fed twice daily) during the weaning-to-estrus interval (WEI) on plasma insulin and IGF-1 concentrations, and on follicle development and subsequent luteal, fetal and placental development and uniformity at days 42 to 43 of pregnancy. A total of 60 multiparous sows (parity 4.7 ± 1.1 at farrowing) at day 35 of pregnancy were housed in groups of five sows until day 108 when housed in individual pens until weaning. After weaning, 57 sows were assigned to the experimental diets. During WEI, multiparous sows were isocalorically fed diets supplemented with different levels of dextrose plus corn starch and/or animal fat. Dietary treatments were: a) 375 g/day dextrose plus 375 g/day corn starch (INS-H), b) 172 g/day dextrose plus 172 g/day corn starch and 144 g/day animal fat (INS-L), and c) with 263 g/day animal fat (CON). Jugular vein catheters were inserted through the ear vein at 1.5 days before weaning to asses plasma insulin and IGF-1 concentrations. After estrus, all sows received a standard gestation diet until slaughter at days 42 to 43 of pregnancy.
The dextrose plus starch-diets enhanced the postprandial insulin response in a dose-dependent manner (P<0.001), but did not affect plasma IGF-1 concentrations during the first 3 days of WEI. Dietary treatments did not affect to follicle development and subsequent luteal, fetal and placental development and uniformity. Pre-weaning plasma insulin and IGF-1 concentrations were negatively related to sow body condition loss during lactation, but were not related to subsequent reproduction characteristics. BW loss during lactation was negatively correlated with IGF-1 concentrations before weaning (P<0.01) and at weaning (P<0.01).
This study shows that dietary dextrose plus starch are effective in stimulating insulin secretion, both insulin post prandial peak and long-term concentration, likely reflecting the separate effects of dextrose (rapid available glucose) and starch (slower available glucose), but not IGF-1 secretion during the first 3 days after weaning in multiparous sows. The extreme insulin-stimulating diets during WEI, however, did not improve follicle development, or subsequent development and uniformity of fetuses and placentas in these high-prolific sows.
J. G. M. Wientjes, N. M. Soede, B. F.A. Laurenssen, R. E. Koopmanschap, H. van den Brand and B. Kemp (2013). Insulin-stimulating diets during the weaning-to-estrus interval do not improve fetal and placental development and uniformity in high-prolific multiparous sows. Animal 1-10. doi:10.1017/S1751731113000566
