Influence of age and ovarian antral follicle count on the reproductive characteristics of embryo donor mares.

BACKGROUND: Age and antral follicle count (AFC) are related to fertility in cattle, but this information remains limited in mares. METHODS: To verify the influence of age and AFC on the reproductive characteristics of mares, 15 Quarter Horse donors, with 5-15 antral follicles, ranging from three to 17 years old, healthy and in good nutritional status, were divided into groups with low AFC (≤9 follicles) or high AFC (≥10 follicles) and mares considered young (≤9 years) or old (≥10 years). Mares were submitted to ultrasonography to determine the dominant follicle diameter, follicular growth rate, degree of uterine oedema and embryonic recovery for a minimum of three oestrous cycles. RESULTS: AFC was higher (P=0.001) in young mares compared with old mares. An interaction (P=0.001) between AFC and age was observed with regard to follicular growth rate, being that mares with low AFC and are old showed the lowest follicular growth compared with those of low AFC and young, high AFC and old, and high AFC and young. Younger mares and those with high AFC exhibited higher degree of uterine oedema (P<0.05) on the third day of oestrus compared with older mares and with low AFC (3 and 2, respectively). However, in both groups, the degree of oedema reduced by the time of ovulation. CONCLUSION: Follicular growth rate, degree of uterine oedema and the number of antral follicles are higher in young mares with high AFC. However, the rate of embryonic recovery is not influenced by donors' age or AFC.

Growth and Differentiation Factor-9 Supplementation Affects Viability and Morphology of Preantral Follicles in Equine Ovarian Fragments During Short-term in vitro Culture

Abstract This study aimed to evaluate different concentrations of growth and differentiation factor-9 (GDF-9) on the development and maintenance of equine preantral follicle morphology during short-term in vitro culture. Ovaries (n=5) from five mares were collected from a local slaughterhouse and transported to the laboratory, where nine fragments (5x5x1mm) were procured from each ovary. One fragment from each was immediately fixed and submitted for histological analysis (control group; D0). The other eight fragments were cultured in situ for two (D2) or six (D6) days in MEM+ or MEM+ supplemented with GDF-9 at different concentrations (i.e., 50, 100 and 200 ng/mL the GDF-9). After culturing with different concentrations of GDF-9 for 2 or 6 days, the fragments were processed for histological analysis. After two days of cultivation, we observed an increase in the percentage of developing follicles for 0 (MEM+), 50, 100 and 200 ng/mL GDF-9 compared to control (D0; P<0.05). When we evaluated all treatments that preserved follicular integrity, the GDF-9 concentration of 100 ng/mL presented results superior to those of the other cultures (P<0.05). While, at six days of culture, the concentration of 200 ng/mL of GDF-9 appeared to be more efficient in providing development compared to MEM+ (P<0.05). The percentage of morphologically intact follicles in the 6 days culture samples treated with 50 ng/mL of GDF-9 indicated that this concentration was effective in maintaining the integrity of the follicle (P<0.05). We conclude, therefore, that graduated GDF-9 addition to the medium ensure follicular development and is sufficient maintain the architecture.

The correlation between the number of antral follicles and ovarian reserves (preantral follicles) in purebred Bos indicus and Bos taurus cows.

The objectives of this study were to compare populations of preantral follicles between purebred Bos indicus and Bos taurus cows with high or low antral follicle counts (AFC) and to correlate the number of preantral follicles with the population of antral follicles. Nelore (Bos indicus, n=100) and Angus (Bos taurus, n=100) cow ovaries were collected at abattoirs and examined using ultrasonography. Antral follicles ≥3mm were counted, and the cows ovaries were assigned to high (G-High) or low (G-Low) AFC groups based on the mean number (±1 SD) of ovarian antral follicles: Bos indicus with high AFC (≥57 follicles, n=8) or low AFC (≤21 follicles, n=8) and Bos taurus with high (≥45 follicles, n=10) or low AFC (≤13 follicles, n=10). The ovaries were processed, and the number of preantral follicles was estimated. Between-groups comparisons were performed using a Kruskal-Wallis test, and the correlation between preantral and antral follicles was evaluated using a Pearson's correlation test (P≤0.05). A large variation in the number of preantral follicles was observed among the animals. Although there was a correlation between the population of preantral follicles and the number of antral follicles, there was no difference between the mean number of preantral follicles in the Bos indicus G-High (48,349±30,149) and G-Low groups (33,037±31,710) or between the Bos taurus G-High (35,050±36,060) and G-Low groups (30,481±43,360). Therefore, the preantral follicle population did not differ between purebred Bos indicus and Bos taurus cattle with high or low AFC but was correlated with the number of antral follicles. In addition to the large within-groups variation in the number of preantral follicles, some cows with high AFC had lower populations of preantral follicles compared to the low AFC group, and the highest population of preantral follicles was observed in both Bos indicus and Bos taurus with low AFC.