Reproductive and lactational responses of multiparous dairy cattle to short-term postpartum chromium supplementation during the summer months

Graphical Abstract Summary Twenty-two multiparous, lactating Holstein cows were enrolled in the experiment, spanning the summer months of June through September. Cows were housed in freestalls where they were individually fed using a Calan gate system. Cows were randomly assigned to the control (Con; no supplement; n = 10) or chromium propionate (CrPro; 12 mg/head per day chromium for 24 d; n = 12) treatment groups. Every 3 days, ovarian structures were counted and measured and blood samples, respiration rates, and rectal temperatures were collected. Every 6 days, a uterine swab was obtained for cytological evaluation to determine the incidences of subclinical endometritis, as determined by polymorphonuclear leukocyte percentage. Chromium supplementation benefited small ovarian follicles, polymorphonuclear leukocyte percentage, and the ratio of plasma progesterone to average corpus luteum volume.