Browsing by Author "Washburn, KEVIN E"
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Item NOVEL CHALLENGES AND STRATEGIES TO OPTIMIZE REPRODUCTIVE EFFICIENCY IN POSTPARTUM CATTLE ADAPTED TO TROPICAL AND SUBTROPICAL CLIMATES.(2019-11-07) Oliveira Filho, Ramiro; Pohler , Ky G; Cooke, REINALDO F; Washburn, KEVIN EThe resumption of ovarian activity after parturition is one of the main challenges of Bos indicus beef cows. The prolonged postpartum anestrus is correlated with many factors and impair the reproductive success of beef cows. Investigations of the factors affecting fertility and the development of strategies to increase reproductive efficiency is an important key to improve productivity in beef cattle herds. Therefore, two studies were conducted. The aim of experiment 1 was to investigate the incidence and effects of subclinical endometritis (SE) on the reproductive performance of postpartum Bos indicus beef cows. Endometrial cytology samples were collected from 654 postpartum Nellore cows before the beginning of the breeding season (d – 11; 28 – 61 DPP) and positive diagnosis of SE were determined when polymorphonuclear cells (PMN) were ≥ 5.0%. Pregnancy diagnosis was performed 30 and 100 days post fixed-time AI (d 0, TAI) and blood samples for pregnancy associated glycoprotein (PAG) were collected at d 30. The prevalence of positive SE was 5.7%. No effect of BCS and DPP was observed in the incidence of SE. Positive SE cows had decreased (P = 0.04) pregnancy rates compared to negative SE cows (33.0 ± 9.1 vs 51.6 ± 3.2; P = 0.04; respectively). The increased percentage of PMN cells decreased (P = 0.02) the probability of the cow becoming pregnant. Embryonic mortality and circulating concentration of PAG did not differ between positive and negative SE cows (P > 0.35). In conclusion, SE decreased pregnancy rate to TAI in postpartum Bos indicus beef cows. The objective of the experiment 2 was to evaluate the effect of clitoral stimulation postTAI on pregnancy rates and temperament of Bos indicus beef cows. A total of 1,186 multiparous Nellore cows were assigned to an estradiol-based estrus synchronization protocol + TAI (d 0) and randomly assigned to receive either 3 seconds of clitoral stimulation or no clitoral stimulation. Concurrently with AI, estrus expression was evaluated based on estrus detection patch activation. Individual chute score was assessed based on a 5 - point subjective scale before AI and individual exit velocity was measured after AI. Pregnancy diagnosis was performed 30 days after TAI via transrectal ultrasonography. Clitoral stimulation had no beneficial effect (P = 0.42) on pregnancy rates of Bos indicus beef cows when compared to those not stimulated (50% ± 4.6 vs. 48.0% ± 4.6). Cows that expressed estrus had greater (P < 0.01) pregnancy rates compared to those that did not express estrus (37.6% ± 4.7 vs. 60.6% ± 4.6); however, no interaction of clitoral stimulation and estrus expression was observed (P > 0.05). Furthermore, clitoral stimulation did not affect (P = 0.75) the exit velocity of cows after TAI. No effect of clitoral stimulation by AI technician on pregnancy rate was observed (P = 0.21). In summary, clitoral stimulation was not a useful managerial tool to improve pregnancy rates in multiparous Bos indicus cows submitted to TAI using an estradiol-based protocol.