Influência da dificuldade de inseminação, temperamento e cortisol plasmático sobre a taxa de concepção de vacas e novilhas da raça Nelore inseminadas em tempo fixo

The objective was to evaluate the influence of stress and difficulty of insemination (DifIA) on conception rate (CR) of Nellore cows (n = 93) and heifers (n = 72) in Timed-AI. On D9, temperament (NTe) and time for chute exit (TSB) were recorded for all animals, and blood samples were colected from heifers. On the day of Timed-AI (D11), NTe, TSB, DifIA and time for AI were recorded. For cows, CR was 36% and for heifers 46% (P > 0.05). No effect (P > 0.05) of NTe was observed on CR. However, a tendency (P < 0,10) for higher CR was observed in animals with no difficulty for insemination (DifIA1; CR=42%) compared to animals that presented moderate or high difficulty (DifIA2+DifIA3, CR=27%). Time required for AI was lower (P < 0.05) in animals DifIA1 (17:31 +/- 06:02sec) than in animals DifIA2-3 (30:10 +/- 15:45sec). Heifers with greater (P < 0.05) cortisol levels presented higher Nte (P < 0.05). However, CR (59%) of less reactive heifers (cortisol=4,12 +/- 1,12ng/mL; NTe=3,2 +/- 0,6) did not differ from CR (41%; P > 0.05) of stressed animals (cortisol=7,76 +/- 1,33ng/mL; NTe=3,82 +/- 0,79). It was concluded that assessments of temperament were related to stress level, although these parameters did not affect the CR of this study. However, the higher difficulty and/or time to complete AI showed to be a potential factor for reducing fertility after timed-AI.