PSXVII-8 Effects of β-carotene and vitamins in grazing Nellore multiparous cows submitted to fixed timed artificial insemination (FTAI)

Abstract The aim was to evaluate the effects of feeding β-carotene and vitamins on reproduction performance of grazing multiparous beef cows. The experiment was conducted in two Brazilian farms (Sidrolandia and Rio Brilhante, MS) during the spring/summer reproduction season. A total of 487 multiparous suckled Nellore cows (Bos indicus) were maintained in 3 paddocks (Brachiaria brizantha) within each farm. Animals were homogeneously assigned into groups according the calving date (25.7 ± 6.3 days postpartum), BCS (2.79 ± 0.5) and β-carotene blood concentration (3.83 ± 0.9 mg/L) to receive treatments for 90 days (30 before and 60 after AI): Control (mineral supplement, n=159); Treatment 1 (mineral supplement with 300 mg β-carotene, 43.000 IU vitamin A, 6.250 IU vitamin D3, 300 mg vitamin E and 12.5 mg biotin/cow/day; n=163); Treatment 2 (mineral supplement with 500 mg β-carotene, 70.000 IU vitamin A, 10.000 IU vitamin D3, 500 mg vitamin E and 20 mg biotin/cow/day; n=165). The supplements were provided by DSM Produtos Nutricionais Brasil S.A. and daily offered in collective feeders. Cows were rotated through the paddocks every 15 days to avoid effects of pasture availability and quantity and synchronized using an estradiol/progesterone based FTAI protocol: D0 – progesterone device and 2.0 mg estradiol benzoate; D9 – 0.530 PFG2α analogue, 300 IU eCG, 1.0 mg estradiol cypionate and progesterone device withdrawal; D11 – FTAI. Pregnancy data were analyzed with orthogonal contrast of PROC GLIMMIX of SAS (Control vs. Treatments 1 + 2). The conception rate at FTAI tended to be greater (P=0.09) in cows supplemented with β-carotene and vitamins (63.4%; 208/328) compared to control group (57.2%; 91/159). No difference was observed between Treatments 1 and 2 (63.8%; 104/163 vs. 63.0%; 104/165 P=0.41). Feeding grazing multiparous Nellore cows with β-carotene and vitamins A, D, E and biotin can increase conception rate at FTAI by 10.8%.