PSV-25 Investigating the effects of Chromium Propionate supplementation on productive and reproductive performance of beef cows

Abstract We investigated the effects of Chromium Propionate supplementation on reproductive performance of beef cows from pre-partum to weaning. Suckled beef cows at nine locations were enrolled in the study. Within location, cows were stratified by parity, dam age, and day postpartum (DPP) and randomly assigned to one of two treatments: 1) Control, supplementation of a mineral product at 113 gּ animal-1ּ d-1 (n = 464 cows; 13 experimental units); or 2) CrP, supplementation of mineral product at 113 gּ animal-1ּ d-1 containing 1.4 g of Chromium Propionate (0.4%KemTRACE Chromium 0.4%, Kemin Industries, Inc., Des Moines, IA; n = 489 cows; 13 experimental units). Treatments were initiated at approximately 37 d pre-calving until weaning for a total of 250 ± 12 d. Cows were enrolled in the 7-d CO-Synch+CIDR fixed-time artificial insemination (TAI) protocol followed by natural service for a 70-d breeding season. Pregnancy diagnosis was performed by ultrasonography at 55 d after TAI protocol and 40 d after the end of the breeding season. Cow body weight (BW) and body condition score (BCS) were recorded at initiation of the TAI protocol (d -10), at pregnancy diagnosis (d 55 and 110), and at weaning (d 285). Within group, mineral disappearance was determined by the difference in weight between offered mineral and refusals. Data were analyzed using the GLIMMIX and MIXED procedures of SAS with pasture/group as the experimental unit with the effect of treatment and included group (treatment × location), cow (group), and location as random variables. Age, DPP, d -10 BCS, and BW were similar (P 0.05) between treatments (5.4 and 5.3 ± 0.61 yr, 79.2 and 79.9 ± 4.61 d, 5.1 and 5.2 ± 0.05, 515.7 and 515.6 ± 15.11 kg for Control and CrP, respectively). Mineral disappearance was similar (P = 0.999) between treatments (165.5 and 152.9 gּ animal-1ּ d-1, for Control and CrP, respectively). Cow BW was similar (P 0.05) between treatments on d 55, 110 and 285 (558.5 and 551.4 ± 14.50 kg, 580.8 and 594.6 ± 13.51 kg, and 574.2 and 570.9 ± 14.32 kg for Control and CrP, respectively). Similarly, cow BCS did not differ (P 0.05) between treatments on d 55, 110 and 285 (5.4 and 5.4 ± 0.09, 5.3 and 5.3 ± 0.10, and 5.1 and 5.2 ± 0.10 for Control and CrP, respectively). Calf birth and weaning BW were similar (P 0.05) between treatments. However, CrP-supplemented cows tended (P = 0.081) to have greater estrus expression (60.2 and 68.3 ± 3.1 %, for Control and CrP, respectively) and CrP-supplemented cows had greater (P = 0.045) TAI pregnancy rate when compared with Control cows (49.9 and 55.2 ± 2.1 %). Supplementation of Chromium Propionate to beef cows from pre-partum through weaning did not affect cow BW and BCS, tended to increase estrus expression and increased TAI pregnancy rate.