Stress effect on conception rate in Nellore cows submmited to fixed time artificial insemination. Preliminary results / Efeito do estresse na taxa de concepção de vacas Nelore inseminadas em tempo fixo. Resultados preliminares

ABSTRACT

In beef cattle, fixed time artificial insemination (FTAI) provides a method to inseminate large numbers of females in a specific time, which result in economical gains due, among others, to a more uniform calf crop. However, FTAI requires frequent manipulation of animals in order to inject hormones and for clinical examination. Consequently, animals seemed stressed in less or higher extent at the time of insemination. This can be a problem because it has been demonstrated that application of an acute stress treatment (electric shock, confinement, restraint and rotation) twice a day during the follicular phase of the oestrous cycle prevents the pre-ovulatory LH surge. This study aimed to evaluate if FTAI efficiency of Nellore cows is affected by the degree of stress observed at time of AI. Nellore cows (n=92) were treated (Day 0) with a progesterone intravaginal devise (Primer®, Tecnopec, São Paulo, Brazil) containing 1 g of progesterone and injected with estradiol benzoate (2mg EB, Estrogin, AUSA, Brazil). Primer was removed on Day 8 (0800 AM) and administered one injection of cloprostenol (125 mcg, Prolise®, Tecnopec, São Paulo, Brazil). Twenty-four hours later, cows received 2 mg EB and insemination (semen from one sire) was done on the afternoon (1400 to 1600 PM) of day 10. At time of FTAI, the stress condition was classified as 1 (low), 2 (moderate) or 3 (high) according

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