RESUMO
The objective of this study was to evaluate the effect of environment on follicular diameter and repeatability of the size of preovulatory follicles of mares. Temperature, rainfall, and photoperiod were measured, and their effects were evaluated on follicular dynamics. Data were studied by analysis of variance of follicular size and environment traits. During the five years, 7% double ovulations and 159 anovulatory follicles were recorded. Mean preovulatory follicle diameters of left and right ovaries were 39.3±3.8 and 39.2±3.5 mm respectively. There was no effect of evaluation year on follicular diameter. Reproduction season affected the right preovulatory follicle diameter. There was no effect of temperature and rainfall on follicular diameter. Repeatability values of the preovulatory follicular diameter were low. In the subtropical climate studied, temperature and rainfall caused no effect on follicular dynamics, and photoperiod had only a small effect on dominant preovulatory follicular diameter. Repeatability of follicular diameter was low, so this characteristic should be evaluated daily to predict ovulation and the optimal time to inseminate mares.(AU)
Assuntos
Animais , Feminino , Meio Ambiente , Folículo Ovariano/anatomia & histologia , Cavalos/anatomia & histologiaRESUMO
The objective of this study was to evaluate the environmental effects on embryo recovery rate and pregnancy rate of Mangalarga Marchador mares. The reproductive characteristics of donor and recipient mares were evaluated during five years in Brazilian tropical environment. The mares were used throughout the year and seasons were classified as: October to April (breeding season - BS); May (autumn transition out of the breeding season - ATBS); June to August (non-breeding season - nBS); and September (vernal transition into the breeding season - VTBS). Daily temperature rainfall and hours of daylight (photoperiod) were measured during all months and years of evaluation. The embryo recovery rate (ERR) and the pregnancy rate (PR) were observed and frequencies were calculated. The effect of environmental variables, day of flushing, and hormonal treatments (estradiol benzoate and progesterone) were determined for the reproductive measures using the Chi-square and Kruskal-Wallis tests. Significant effects were noted of the year, season and temperature on ERR (Pâ¯<â¯0.05), but no significant effects were observed of the environmental parameters (year, season, hormone treatment, rainfall and photoperiod) on PR (Pâ¯>â¯0.05). The day of uterine flush affected ERR (Pâ¯<â¯0.05) but did not affect PR (Pâ¯>â¯0.05). In addition, hormone treatment also supported favorable results of PR in recipient mares during nBS. The conclusion is that mares of this breed can be used in reproduction all year long, with good pregnancy rates, in Brazil's tropical environment. The hormone treatment also supported favorable pregnancy rates in recipient mares during the non-breeding season. It seems that mares can have good pregnancy rates throughout the year in Brazil´s tropical environment.