|PINTO, T - Federal University - Brazil|
|NOGUEIRA, M - Federal University - Brazil|
|SALES, J - Federal University - Brazil|
|CARVALHO, R - Federal University - Brazil|
|Cushman, Robert - Bob|
|SOUZA, J - Federal University - Brazil|
Submitted to: Science and Agrotechnology of Lavras
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2015
Publication Date: 10/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61589
Citation: Pinto, T.L., Nogueira, M.B., Sales, J.S., Carvalho, R.R., Cushman, R.A., Souza, J.C. 2015. Factors affecting pregnancy rates after ovum pick up-derived embryo transfer in lactating Holstein recipients under tropical conditions. Science and Agrotechnology of Lavras. 39(5):498-505.
Interpretive Summary: To eliminate environmental influences on oocyte quality and determine factors separate from oocyte quality contributing to fertility in cows, we used ultrasound-guided oocyte pick up and in vitro fertilization to generate embryos. Embryos were transferred to lactating Holstein cows 6 to 8 days after spontaneous standing estrus. Stage of lactation, milk yield, age (heifer or cow), serum progesterone concentrations, and body condition score were examined as potential factors influencing establishment of pregnancy after embryo transfer. None of these factors had a significant impact on establishment of pregnancy. Approximately two thirds of the cows were treated with gonadotropin releasing hormone (Buserelin or Deslorelin) on the day of embryo transfer in an attempt to improve pregnancy rates. While Buserelin increased the ovulation rate, it did not change serum progesterone concentrations compared to Control of Deslorelin treatments. There was an increase in the percent of cows pregnant at first examination in the Buserelin group; however, at the second pregnancy examination, there was no difference in percent pregnant among treatments. These data indicate that when a good quality embryo is transferred, lactational status, age, and body condition do not influence establishment of pregnancy. In addition, serum progesterone concentrations do not influence establishment of pregnancy. As we have demonstrated in the past, increases in ovulation rate do not increase serum progesterone concentrations most likely due to increased negative feedback at the hypothalamus and pituitary. From this, we conclude that oocyte quality has a major role in determining establishment of pregnancy.
Technical Abstract: High milk production, heat, physiological status and management impair reproduction in Holstein cows. The use of in vivo-produced embryos has been reported as an alternative to enhance pregnancy outcome in the tropics; however there are several limitations for its production, especially from variations in superovulatory responses. The in vitro production of embryos would avoid such variations, but few studies have been reported. This study aims to verify the effects of variables related to recipients under a program of routine in vitro embryo transfer on a commercial dairy farm in southeastern Brazil. It was hypothesized that pregnancy rates after transfer of ovum pick up or OPU-derived embryos (ET) to lactating Holstein recipients may be influenced by recipient GnRH-treatment at ET, parity, milk production and body condition score. Recipients (267) were allocated to one of three i.m. treatments given at ET: Control (92) – 2.5 ml saline; Buserelin (86) – 10 µg of Buserelin acetate; Deslorelin (89) – 750 µg of Deslorelin acetate. Ultrasound images and blood samples were taken at ET and seven days later. The first pregnancy diagnosis was performed between 30-40 days and the second between 60-80 days post ET. Data were analyzed by GENMOD (SAS). The proportion of pregnant cows was greater (P<0.05) in Buserelin-treated recipients (38.3%) at the first pregnancy diagnosis than Controls (24.1%), but similar to Deslorelin and control cows at the second diagnosis (13.0, 20.9 and 14.6% in Control, Buserelin and Deslorelin, respectively). In conclusion, Buserelin improved pregnancy rate only transitorily, under the present conditions.