Effect of follicular wave synchronization on in vitro embryo production in Nelore cows

In vitro embryo production is an important technology and many studies have been made to improve its efficiency. The aim of this study was to analyze the influence of follicular wave synchronization on embryo production. The experiment was conducted at Estancia Olho D' agua in Mandaguacu - PR from January and November 2012. Twenty Nelore cows (approximately 450 kg) were randomly assigned into one of two treatments: T1 - Control (n=10) and T2 - Synchronization of follicular wave (n=10). Animals in T2 received an ear implant containing 3.0 mg norgestomet (Crestar) on Day 0, 2.0 mg of estradiol benzoate (Estrogin) and 500 μg of PGF2α (Ciosin®). Five days later, follicles were aspirated using an ultrasound (Mindray DP2200) and a 5MHz convex probe coupled to a 18G (Jelcor) needle and vacuum pump (cook - 75 mm Hg). After each aspiration, oocytes were selected according to their morphology and immediately sent to the laboratory where they were submitted to in vitro maturation (IVM), fertilization (IVF) and culture (IVC). For data analysis, the SAS software was used, applying the procedure for generalized linear models (PROC GENMOD) with Poisson distribution and identity link function. Eight follicular aspirations in each animal were performed every 21 days. After each section, the animals were allocated to the other treatment in the following procedure. Thus a total of 160 follicular aspirations was performed. The total number of oocytes (T1: 18.46 ± 0.46, T2: 20.85 ± 0.49, p < 0.0005), viable oocytes (T1: 12.10 ± 0.37, T2: 13.14 ± 0.39, p < 0.06) and rate of embryo development (T1: 39.08 ± 0.68 %, T2: 43.25 ± 0.71 %, p < 0.0001) were higher in animals submitted to follicular wave synchronization before follicular aspiration, compared to those who were aspirated without synchronization. In conclusion, follicular wave synchronization is a viable alternative to increase embryo production in Nelore cows.