Dataset_14-d interval ovum pick up
The dataset contains information obtained in a two-treatment (FWS vs. control) and two-period (1 vs. 2) crossover design study run in a commercial dairy herd from Argentina to test the hypothesis that follicular wave synchronization (FWS) before ovum pick-up (OPU) modifies follicle size and increases oocyte recovery and in vitro embryo development in beef cows and that short intersession interval OPU schemes, such as 14-day intersession interval, lead to potential carryover effects. The objectives were to evaluate: 1- the effect of FWS on follicle size, oocyte recovery, and in vitro embryo development in cows subjected to OPU sessions with an interval of 14 days, and 2- the probability of a carryover effect due to the short intersession interval used. The treatment had neither effect on follicle size nor the number of oocytes (P = 0.81 and 0.53, respectively). However, treatment tended to affect the total embryo number (P = 0.06) given that cows receiving FWS had twice the number of embryos as control cows. Finally, treatment did not affect the number of frozen embryos (P = 0.76). The period affected the number of good oocytes (P = 0.05). The period also tended to affect the number of viable oocytes given that it also increased in the second one (P = 0.07). Finally, the period tended to affect the total number of embryos given that it decreased in the second one (P = 0.10). Otherwise, treatment by period interaction (testing for carryover effect) affected the total number of follicles (P = 0.05) and, also, the number of viable oocytes (P = 0.02). It also tended to have effect on the number of < 6 mm follicles (P = 0.13), the total number of oocytes (P = 0.11), the number of good oocytes (P = 0.12), and the number of regular oocytes (P = 0.13).
Steps to reproduce
Angus primiparous cows (n: 6) from a commercial farm located in Buenos Aires, Argentina were enrolled in a replicated 2x2 crossover design where cows were randomly assigned to receive one of the following treatment sequences: FWS in period 1 and control in period 2 or control in period 1 and FWS in period 2. In addition, the experiment was replicated once. Therefore, the FWS group received the following protocol: on day 0, cows received 1 g progesterone via an intravaginal device (DIB, Syntex, Argentina), 2 mg estradiol benzoate (Syntex), and an intramuscular dose of synthetic prostaglandin F2 alpha (150 μg D-cloprostenol; Ciclase, Syntex), and on d 5, the intravaginal device was removed. Control group animals did not receive any hormone treatment and acted as the negative control. The OPU sessions were carried out on the same day in cows from both study groups (day 5 of FWS). Nine days after OPU, the synchronization protocol was implemented again (day 0) in FWS cows. In total, four OPU sessions per cow were performed every 14 days, during which each cow received the FWS and control treatment twice. Body condition score (BCS) was assessed with a 9-point scale on the day of OPU. All follicular aspirations were performed by a single trained technician using a Mindray DP10 ultrasound scanner equipped with a 7.5 MHz micro-convex transducer and an aspiration guide connected to a vacuum pump (Cook Veterinary Products, Queensland, Australia). Before starting OPU, the follicular population (the number of antral follicles observed in both ovaries), follicle size (the number of follicles < 6 mm, 6 - 10 mm, and >10 mm), and the presence of corpus luteum were determined. Immediately after OPU, oocytes were examined and morphologically classified into four categories according to the number of cumulus cell (CC) layers, the expansion of CC, and the appearance of the cytoplasm regarding color, homogeneity, and integrity, as follows: good (more than three layers of CC), regular (at least one layer of CC), denuded (Partly covered with CC or without CC), and atretic (irregular cytoplasm, with dark cumulus oophorous and signs of cytoplasmic degeneration). Good, regular, and denuded oocytes were used together for IVP (viable oocytes). Atretic oocytes were discarded. The number of the total oocyte (atretic plus viable oocytes) was recorded for each treatment group. Oocyte in vitro maturation (IVM), fertilization (IVF), and embryo culture (IVC) were performed according to Anchordoquy et al. (2017). Poisson regression models included treatment (FWS vs. Control), period (1 vs. 2), treatment by period interaction (testing for carryover effect), and BCS (6 vs. 7) as fixed effects, and replicate (n=2) as a blocking factor. In addition, cows were nested in the sequence of treatment (Control-FWS and FWS-Control). A P ≤ 0.05 was considered significant and a P ≤0.10 was regarded as a trend. In the case of interactions, a P ≤ 0.10 was significant, and a P ≤ 0.15 was a trend.