The effects of varying levels of dietary starch on reproductive traits in lactating dairy cows

The aim of this study was to determine the effects of three different dietary starch levels on postpartum milk yield, blood metabolites, and reproductive traits in cows. A total of 23 primiparous Holstein-Friesian cows were fed three different diets including different starch levels on a dry matter basis from parturition until day 80. Cows were randomly assigned into the three groups according to the starch levels: low (LS, 16%, n = 7), medium (MS, 20%, n = 8), and high (HS, 24%, n = 8). Milk yields were recorded daily, and body condition score (BCS) was determined every week. Transrectal ultrasonography was performed, and blood samples were taken three times each week to determine reproductive traits and blood metabolites. Although the milk yield was greater in the LS group compared to the other groups, BCS and blood metabolites did not differ among the groups. The postpartum follicular patterns, times of first postpartum ovulation, and involution processes did not differ among the groups. In addition, the ovulatory follicle and corpus luteum sizes and the progesterone levels after induced estrus were numerically greater in HS than other groups. Thus, there were no effects of starch levels on postpartum reproductive traits.