The number of antral follicles counted (AFC) by ultrasound is associated with fertility in cattle. Cows with higher follicle count (HFC) have higher performance in reproductive‐assisted technologies than cows with lower follicle count (LFC). In this study, we aimed to define the preantral follicle count by histology and to identify differentially expressed genes (DEGs) using a microarray in Nelore and Angus heifers with HFC and LFC. The ovaries of each animal were scanned with an ultrasound device 12 to 24 hr after estrus. The groups were formed based on the average number of total follicles (≥3 mm) counted in each breed consistently ± the standard deviation. For the histological analysis, preantral follicles were counted and classified under a stereo microscope, and follicle density was determined. Microarray analysis was performed on pools of three follicles dissected from the ovaries of 15 Nelore (6 HFC and 9 LFC) and 17 Angus heifers (9 HFC and 8 LFC). Angus heifers have increased total and primordial follicle density. Nelore heifers have increased antral follicle count. Different patterns of gene expression regulate follicle recruitment and development in Angus and Nelore heifers and may be associated with the different follicle densities observed in Angus versus Nelore heifers. Furthermore, HFC heifers presented increased expression of genes associated with cellular development and metabolism.

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In the bovine oviduct, estradiol (E2) stimulates secretion and cell proliferation, whereas progesterone (P4) suppresses them. In this study, we have evaluated the effect of two superstimulatory protocols (follicle‐stimulating hormone [FSH] or FSH combined with equine chorionic gonadotropin [eCG]) on the oviductal levels of E2 and P4 and its outcome on oviductal cells. Compared with the control group (a single pre‐ovulatory follicle), we have observed that the cows submitted to FSH/eCG treatment showed a higher concentration of E2 in the oviduct tissue, together with a higher abundance of messenger RNA encoding steroid receptors (ESR1 and progesterone receptor), and genes linked to gamete interactions and regulation of polyspermy (oviduct‐specific glycoprotein 1, heat‐shock protein family A member 5, α‐l‐fucosidase 1 [FUCA1], and FUCA2) in the infundibulum and ampulla segments of the oviduct. However, we did not observe any modulation of gene expression in the isthmus segment. Even though the FSH protocol upregulated some of the genes analyzed, we may infer that the steady effect of FSH combined with eCG on oviduct regulation might benefit fertilization and may potentially increase pregnancy rates.

In vitro-produced embryos (IVP) are known to have poor quality and be susceptible to heat and oxidative stress. In addition, they constantly undergo long-distance transport, which causes low conception rates. The aim of this study was to search for alternatives to long-distances transport of embryos produced in vitro by evaluating the use of different media and different temperatures. Bos indicus cumulus–oocyte complexes (COC; 823, quality I and II) were matured in TCM-199 bicarbonate–10% FBS (38.5°C, 5% CO2, in air) for 24 h. The fertilization was performed in TALP-IVF medium for 18 h of incubation. Presumptive zygotes were transferred to SOF medium and in vitro culture in a controlled atmosphere (5% O2, 5% CO2, 90% N2) for 7 days at 38.5°C. At Day 7, 366 embryos (quality I and II, IETS), were randomly allocated to the designated experimental groups. For Experiment 1, blastocysts were filled into straws and kept for 12 h at 36°C, using the medium as an independent variable according to the following groups: GSup, embryo support medium without FCS and amino acids (n = 115); and GHSOF, embryo culture medium SOF (HSOF) with FCS and amino acids (n = 105). Both media were buffered with HEPES. For Experiment 2, blastocysts were filled into straws with HSOF medium and sustained in transportation for 12 h, using temperature as the independent variable according to the following groups: G36, 36°C (n = 65); and G38, 38°C (n = 81). After 12 h of transport in both experiments, embryos were evaluated and classified as viable or nonviable blastocysts and were recultured in the same conditions mentioned. On Day 10, hatching rates and degeneration were evaluated. Logistic regression was used to compare the groups in each experiment. In Experiment 1, blastocyst viability after 12 h of transport was higher in the culture medium (GHSOF: 91.4%) than the support medium (GSup: 75.6%; P < 0.001). The hatching capacity in the culture medium (GHSOF: 72.4%) was higher than that in the support medium (GSup: 34.5%; P < 0.001). In Experiment 2, blastocyst viability post-transport was the same in both temperatures (G36: 92.3%, G38: 82.7%; P > 0.09). Blastocyst hatching capacity at 36°C (G36: 75.4%) was superior to that at 38°C (G38: 49%; P < 0.001). The hatching capacity immediately after 12 h of transport was minimal, so it was not possible to apply the logistic regression method in any experiment. In conclusion, the culture medium was more efficient for long-distance transport than the support medium; moreover, a temperature of 36°C for the culture medium increased embryo development compared with a temperature of 38°C during transport. Financial support was provided by CESUMAR.

Cattle from Bos indicus breeds recruit and develop more follicles per oestrous cycle compared with cattle from Bos taurus breeds. The number of antral follicles in the ovaries is a decisive factor for the success of reproductive technologies such as ovum pick-up and embryo transfer. The reasons why indicine cattle recruit and develop more follicles are not known. Our objectives were to evaluate the ovarian reserve of Nellore and Angus heifers and determine at which stage of follicle development Nellor ovarian reserve differs from Angus ovarian reserve. To determine if animals were in the low or high follicle count group (LFC or HFC), antral follicles (≥3 mm) were scanned with an ultrasound device (US; Mindray Vet DPS 2200, Sao Paulo, Brazil) equipped with a 7.5-MHz probe Day 1 after ovulation (Day 0) for 3 consecutive oestrous cycles. Eighteen Nellore heifers (11 LFC and 7 HFC) and 25 Angus heifers (12 LFC and 13 HFC) were used in the experiment. Oestrous cycles were synchronized with 2 doses of PGF2α  ± 11 days apart. Animals were slaughtered ~24 h after ovulation of the third oestrous cycle. Ovulation was determined by oestrous observation, absence of the dominant follicle on the ultrasound, and presence of the corpus luteum after slaughter. One ovary from each animal was used for histology. The ovary was sliced longitudinally in 6 parts, fixed in 10% paraformaldehyde for 24 h, and stored in 70% ethanol until processing. Two longitudinal slices were blocked in paraffin. One section (8 μm thick) was stained after every 50 sections, totaling 10 sections per longitudinal slice of ovarian tissue. Sections were stained using eosin and hematoxylin. Follicles were counted and classified under a stereo microscope with a 40× objective; only follicles with a visible nucleus were counted. Follicles were classified as primordial, primary, and secondary. The area of each section was measured using the hand tool on the ImageJ software. Area measurements were expressed as pixels squared. The density of each follicle classification was calculated as follicle/log10 [pixel2]. Data were analysed using PROC GLM procedure of SAS 9.2 considering the effects of breed and group (LFC or HFC). Angus heifers had more primordial follicles (P < 0.02) when compared with Nellore heifers, but there was no difference within groups. There was no difference in the number of primary follicles within breeds or groups. Secondary follicle numbers tended to be higher (P = 0.09) in Nellore heifers when compared with Angus heifers and was higher within groups (P < 0.02), with HFC Angus and Nellore heifers having more follicles than LFC heifers. It is possible that HFC heifers have a mechanism that is developing more follicles beginning at the secondary stage, especially Nellore heifers. The development of more secondary follicles may contribute to the depletion of primordial follicles observed in Nellore heifers. This research is funded by Sao Paulo Research Foundation (FAPESP) grant #2011/50964-0. Scholarships for Favoureto, Queiroz, Loureiro, Ereno, and Pupulin are also from FAPESP.