Abstract #T158

# T158
Short-term feeding of a rumen-protected carbohydrate increases plasma insulin concentrations in early postpartum dairy cows.
M. C. Lucy*1, A. R. Castillo2, J. P. Russi3, G. Díaz-Pérez1, S. G. Moore1, L. M. Mayo1, R. Doyle1, 1University of Missouri, Columbia, MO, 2University of California, Cooperative Extension, Merced, CA, 3RUSITEC, Piedritas, Buenos Aires, Argentina.

Low blood glucose concentrations early postpartum are associated with low blood insulin concentrations, postpartum metabolic disorders, and infertility. The hypothesis was that short-term feeding of a rumen protected carbohydrate (RPC; 56% soybean meal, 40% soluble carbohydrates, 3.2% urea, and 0.8% minerals) would increase blood insulin concentrations by increasing glucose supply from the gastrointestinal tract. Lactating dairy cows (4 Holstein and 1 Guernsey; 17 ± 2 DIM; 30.9 ± 4.6 kg milk and 13.7 ± 2.6 kg DMI per day) were jugular catheterized, barn housed, and milked 2×. During the first 24 h (d 1), cows were fed a nutritionally balanced TMR (corn silage, haylage, wet brewer grains, dry corn, alfalfa hay, rumen protected and unprotected soybean meal, soyhulls, and premix). After 24 h (d 2, 3, and 4), cows were fed the TMR with the RPC added at 10% of diet DM. On d 5, cows were switched to control TMR. Blood was sampled every 2 h for d 1 to 5 through a jugular catheter. Plasma was isolated and analyzed for insulin, glucose, β-hydroxybutyrate (BHB) and nonesterified fatty acids (NEFA). Data were analyzed for the effects of day, time, and day by time with cow as a random effect (Proc GLM of SAS). There was an effect of day (P < 0.001) on plasma insulin concentrations (0.23, 0.24, 0.31, 0.40, and 0.36 ng/mL; SEM = 0.027; d 1 to 5, respectively). The increase in blood insulin was associated with a decrease in plasma glucose (54.4, 55.7, 51.0, 50.9, and 51.3 mg/dL; SEM = 0.7; d 1 to 5) and an increase (P < 0.001) in plasma BHB (1.64, 1.78, 2.01, 2.19, and 1.97 mmol/L; SEM = 0.06; d 1 to 5; P < 0.001). There was no effect of day on plasma NEFA but there was an effect of time (P < 0.001). Milk produced and DMI were similar (P > 0.10) for d 1 to 5. In conclusion, short-term feeding of the RPC increased blood insulin concentrations. The increase in blood insulin was associated with a decrease in blood glucose and an increase in BHB. Feeding RPC to early postpartum dairy cows effectively alleviated depressed insulin and shifted associated metabolite concentrations.

Key Words: insulin, glucose, bypass carbohydrate