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Insulin and insulin-like growth factor-I (IGF-I) are known to stimulate follicle and oocyte development, either indirectly at the brain level via stimulation of luteinizing hormone or directly at the ovarian level. Both insulin and IGF-I can be modulated by diet composition or specific feed components such as carbohydrates. Among the different sources of carbohydrates, sugars, like dextrose and sucrose, result in a quick and high increase in insulin directly after feeding, whereas fermentable carbohydrate sources may increase insulin levels for a prolonged period after feeding. Effects of different carbohydrate sources on plasma glucose, insulin and IGF-I levels were compared to subsequently be able to study effects of insulin-stimulating diets on follicle development in sows multiparous. The following feed components were tested in 12 multiparous sows (parity 7.7 ± 0.5; range: 4-10) during six consecutive test periods of 9.5 days: dextrose (DEX), sucrose (SUC), lactose (LAC), dextrose plus lactose (DL), sucrose plus lactose (SL), dextrose plus sugar beet pulp (DSBP) and control (CON). Sows arrived at the experimental farm at 25.8 ± 1.4 days (range: 19–33 days) after weaning and an adaptation period of 7 days was conducted before starting the trial. Sows were housed in individual farrowing crates and all test diets were fed at 3 kg/day. Blood samples were collected from the jugular vein on day 2, 5 and 9 of each test period and plasma glucose (only at day 9), insulin and IGF-I profiles were determined.
Despite similar glucose profiles for all diets, the postprandial insulin response was higher for DL and SL compared with CON and LAC; the other diets were intermediate. Plasma IGF-I levels were higher in CON, LAC and SL compared with DSBP, but differences were only marginal. It was concluded that dextrose and sucrose have the potential to stimulate fast and high insulin peaks, especially when combined with additional lactose. Despite the high dextrose in the DSBP diet, the insulin response was flattened, probably due to the viscosity of sugar beet pulp.
The results show that modulation of plasma insulin levels by dietary carbohydrates seems possible in anabolic sows, but IGF-I levels are less easily modified.
JGM Wientjes, NM Soede, F Aarsse, BFA Laurenssen, RE Koopmanschap, H van den Brand and B Kemp. Dietary carbohydrate sources affect plasma glucose, insulin and IGF-I levels in multiparous sows. 2012. Journal of Animal Physiology and Animal Nutrition, 96: 494-505. doi: 10.1111/j.1439-0396.2011.01171.x.