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A novel strategy for resynchronization of ovulation in Nelore cows using injectable progesterone (P4) and P4 releasing devices to perform two timed inseminations within 22 days
Author(s) -
Pugliesi Guilherme,
Bisinotto Danilo Zago,
Mello Barbara Piffero,
Lahr Fábio C.,
Ferreira Catia A.,
Melo Gabriela Dalmaso,
Bastos Michele Ricieri,
Madureira Ed Hoffmann
Publication year - 2019
Publication title -
reproduction in domestic animals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.546
H-Index - 66
eISSN - 1439-0531
pISSN - 0936-6768
DOI - 10.1111/rda.13475
Subject(s) - corpus luteum , artificial insemination , estrous cycle , pregnancy , ovulation , pregnancy rate , zoology , insemination , follicle , medicine , gynecology , endocrinology , biology , hormone , genetics
We aimed to evaluate the reproductive performance of Nelore lactating cows submitted to a resynchronization 12 days after timed artificial insemination (TAI) with or without a long‐acting progesterone (P4‐LA) treatment. Nelore cows were submitted to a P4/oestradiol‐based TAI protocol (D0 = insemination). On D12, cows in the control group ( n = 184) received a new P4 intravaginal device (0.96 g), whereas cows in the P4‐LA group ( n = 192) received the P4 device and 75 mg P4‐LA. Cows identified as non‐pregnant ( n = 120) by regression of corpus luteum using colour Doppler ultrasonography on D20 had the P4 device removed and received 500ug of sodium cloprostenol, 1 mg of oestradiol cypionate and 300 IU of eCG and were re‐inseminated on D22. There was no difference ( p > 0.10) in the pregnancy rate at D20, D30 and D60 after first TAI between the control (69%, 59.7% and 57%, respectively) and P4‐LA (67%, 55.7%, and 55.2%, respectively) groups. Pregnancy losses were similar between both groups ( p > 0.1). For cows submitted to the second TAI, the pre‐ovulatory follicle size did not differ ( p > 0.1), but the oestrous detection and pregnancy rates were greater ( p < 0.05) in the P4‐LA group (92.2% [59/64] and 60.9% [39/64], respectively) than in controls (75% [42/56] and 44.6% [25/56]). The cumulative pregnancy rate after two TAIs did not differ ( p > 0.1) between control (73.3% [135/184]) and P4‐LA (76% [146/192]) groups. The use of P4‐LA at 12 days after TAI potentially increases the pregnancy rates for a new early resynchronization strategy associated with the Doppler imaging for pregnancy diagnosis and results in an alternative to perform two TAIs in 22 days in beef cows.