171 Supplementing Ca Salts of Soybean Oil Via Low-Moisture Molasses-Based Blocks to Improve Reproductive Performance and Overall Productivity of Beef Cows

Abstract

Abstract This experiment evaluated reproductive and productive responses of beef cows receiving self-fed low-moisture blocks (LMB) enriched or not with Ca salts of soybean oil (CSSO) throughout the breeding season. Non-pregnant, suckling multiparous Angus-influenced cows (n = 554) were assigned to a fixed-time artificial insemination (AI) protocol (day -10 to 0) followed by natural service (day 15 to 70). Cows were managed in 12 groups (46 ± 4 cows/group) maintained in individual pastures, and groups received LMB enriched with 25% (as-fed basis) of CSSO or ground corn (CON) from day -10 to 100. Both treatments were designed to yield a daily LMB intake of 0.454 kg/cow (as-fed basis). Groups were enrolled in an estrus-synchronization + fixed-time AI protocol from day -10 to 0 (AI occurred on day 0) of the experiment and beginning 15 days after AI cows were exposed to mature Angus bulls for 55 d. Pregnancy status was verified on day 55 and 100 of the experiment, and cows that gave birth during the initial two weeks were considered pregnant to fixed-time AI. Calf birthdate and weight was recorded during the subsequent breeding season. All calves were weaned at the same time, and a calf BW and age were recorded. Blood samples were also collected from a subsample of cows on days -10, 0 (fixed-time AI), and 55 (pregnancy diagnosis). All data were analyzed using group as the experimental unit and Satterthwaite approximation to determine the denominator df for the tests of fixed effects. Quantitative data were analyzed with the MIXED procedure of SAS, and binary data analyzed with the GLIMMIX procedure of SAS with a binomial distribution and logit link function. Data were analyzed with group (treatment × location), cow(group), and location as random variables. Significance was set at P ≤ 0.05 and tendencies were determined if P > 0.05 and ≤ 0.10. Cows receiving CSSO had greater (P < 0.01) mean concentrations of ω-6 fatty acids in plasma samples collected on days 0 and 55. Cows receiving CSSO had greater (P = 0.05) pregnancy rate to fixed-time AI (67.2 vs. 59.3%), whereas final pregnancy rate did not differ (P = 0.92) between treatments. Pregnancy loss was less (P = 0.03) in CSSO cows (4.50 vs. 9.04%), which also calved earlier during the calving season (treatment × week; P = 0.04). Weaning rate tended to be greater (P = 0.09) in CSSO (84.8 vs. 79.4%), although calf weaning age and weight did not differ (P ≥ 0.72) between treatments. Kilos of calf weaned/cow exposed was greater (P = 0.04) in CSSO cows (234 vs. 215 kg). Therefore, supplementing CSSO to beef cows via LMB during the breeding season improved their reproductive and overall productivity during a cow-calf cycle.