Effect of JSynch treatment on pregnancy rate in heifers submitted to fixed time artificial insemination

Abstract

The objective of the present work was to evaluate the effect of J-Synch protocol used in heifers on pregnancy rate submitted to fixed time artificial insemination (FTAI). Six hundred and thirteen Angus heifers were used (age range: 13.5 to 15 months; body condition: 3 to 3.5 -scale 1 to 5 (1: emaciated and 5: obese) and weight: ≥ 260 kg. The animals were randomly assigned to the experimental units (heifers) according to a completely randomized design, to the following group: 1) J-Synch (n=205): on day 0 an intravaginal device was inserted with 0.6 g of progesterone (IVD) plus 2 mg of estradiol benzoate. On day 6 the device was removal and 0.15 mg of d-cloprostenol was administered. On day 9 (70-72 h after device removal), 0.10 mg of buserelin was injected and FTAI was performed. 2) Conventional 7D (n=206): on day 0 an intravaginal device (IVD) was inserted plus 2 mg of estradiol benzoate. On day 7 the device was removed and 0.15 mg of d-cloprostenol and 0.5 mg of estradiol cypionate were administered. On day 9 (50-52 h after device removal), FTAI was performed. 3) Conventional 8D (n=202): similar to Conventional group 7D, with the exception that the device remained in the vagina for a period of 8 days. For FTAI, frozen / thawed semen from a bull of proven fertility was used. Gestation diagnosis were performed at 30 days after FTAI. The statistical analysis was made by SAS. A 95% confidence level was established (α=0.05). Animals that lost the device (3.4%) were excluded from the statistical analysis. The pregnancy rate was not different between treatments (J-synch: 50.8%, Conventional 7D: 43.4% and Conventional 8D: 47.7%, p>0.05). In conclusion, J-Synch treatment used in beef heifers (13.5-15 months of age) generates pregnancy rate after FTAI similar to conventional treatment.