Publicação: Effects of excessive energy intake and supplementation with chromium propionate on insulin resistance parameters, milk production, and reproductive outcomes of lactating dairy cows
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This experiment compared insulin resistance parameters, milk production, and reproductive outcomes in: (1) lactating dairy cows consuming adequate or excessive energy, and (2) lactating dairy cows consuming excessive energy and receiving or not Cr-propionate supplementation. Seventeen primiparous and multiparous, non-pregnant, lactating Holstein cows (initial days in milk=76±2) were assigned on d 0 to: (1) concentrate intake to meet their requirements of net energy for lactation (NE<inf>L</inf>) without Cr supplementation (MAN; n=5), (2) concentrate intake to exceed their NE<inf>L</inf> requirements without Cr supplementation (HIGH; n=6), and (3) HIGH with 2.5g/d of Cr propionate (HIGHCR; n=6). Throughout the experiment (d 0 to 210), cows were offered corn silage for ad libitum consumption, and individually received a corn-based concentrate twice daily. Concentrate intake was formulated to allow diets to provide 100% of daily NE<inf>L</inf> requirements of MAN, and 160% of daily NE<inf>L</inf> requirements of HIGH and HIGHCR cows. Cow BW, BCS, and milk production were recorded weekly. Blood samples were collected weekly, prior to and at 2 and 4h after the morning concentrate feeding. Six glucose tolerance tests (GTT) were performed, every 42d, by infusing cows with 0.5g of glucose/kg of BW. Follicle aspiration for in vitro embryo production was performed via transvaginal ovum pick-up 2d after each GTT. Increase in BCS from d 0 to 210 was greater (P≤0.04) in HIGH and HIGHCR vs. MAN. Milk production was similar (P=0.92) between treatments. Within weekly samples, serum non-esterified fatty acids concentration were greater (P≤0.05) for MAN vs. HIGH and HIGHCR. Serum insulin concentrations and insulin:glucose ratio were often greater (P≤0.05) for HIGH, intermediate for HIGHCR, and lesser for MAN (treatment×day interaction, P<0.01). During the GTT, serum insulin concentrations and insulin:glucose ratio were greater (P≤0.05) for HIGH compared with HIGHCR and MAN from 10 to 60min relative to the time of glucose infusion. Proportion of embryo produced per oocyte collected was greater (P≤0.02) for MAN vs. HIGH and HIGHCR, and similar (P=0.59) between HIGH and HIGHCR. In conclusion, lactating cows consuming excessive concentrate and NE<inf>L</inf> experienced increased insulin resistance and reduced proportion of embryo produced per oocyte collected compared with cows consuming adequate amounts of energy, whereas Cr-propionate supplementation was effective in alleviating insulin resistance caused by excessive NE<inf>L</inf> intake.
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Chromium, Dairy cows, Energy intake, Insulin resistance
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Inglês
Como citar
Livestock Science, v. 180, p. 121-128.
