LAUSR

The aim was to evaluate the effects of beta-carotene and vitamins (A, D3, E and biotin) on reproductive performance of grazing Nellore cows calving in different moments. A total of 497 multiparous cows (5.68 ± 0.11 parities) were homogeneously divided in 4 paddocks (Brachiaria brizantha spp.) according to BCS (2.8 ± 0.27), following a completely randomized design in a 2 x 2 factorial arrangement, being the factors: calving moment [CM = early October (EO; 1st-15th) or late October (LO; 16th-31st)]; and supplementation (SUP): control [(mineral supplementation, Fosbovi® Reprodução; n = 251) or vitamins (control + beta-carotene (150 mg), vitamins A (40.000IU), D3 (5.000IU), E (300 mg) and biotin (20 mg)/cow/day; n = 246)]. Mineral supplement and vitamins were daily offered for 60 days (30d before to 30d after 1st FTAI), and provided by DSM Produtos Nutricionais Brasil S.A. Cows were synchronized (1st FTAI) with a P4/E2-based FTAI protocol, and open cows were resynchronized (2nd FTAI) 30 days after the first insemination. The 1st FTAI conception rate (CR) tended to be greater for vitamins group, compared to control [64.2%(158/246) vs. 56.6%(142/251); P = 0.08], regardless of CM. The CM*SUP interaction was significant for CR at 2nd FTAI, with vitamins presenting higher CR over control in LO moment [52.1% (38/73) vs. 41.4% (24/58), P = 0.0053]. Greater cumulative CR (1st + 2nd FTAI) was observed for vitamins over control [83% (204/246) vs. 79% (198/251); P = 0,058], and for LO compared to EO [86% (157/183) vs. 78% (245/314); P = 0.01], without CM*SUP significance. The BCS was higher for the vitamins group, compared to control, at AI moment (3.00 vs. 2.81, P < 0.0001) and 30 days after AI (3.11 vs. 3.03, P < 0.0001), regardless of CM. The inclusion of beta-carotene and vitamins A, D3, E and biotin in mineral supplements is a tool to optimize reproductive performance and BCS of grazing Nellore beef cows during breeding season.