مطالعه اثرات طولاني مدت تغذيه بر فعاليت فوليكولي تخمدان در قبل و بعد از بلوغ جنسي در تليسه هاي برهمن

Study of long-term nutritional effects on ovarian follicular function in pre- and postpubertal period in Brahman heifers

The objective of this study was to determine the long-term nutritional effects on ovarian follicular function during the pre- and postpubertal period in Brahman heifers. Twenty-two growing heifers were randomly assigned into two equal groups based on their age and initial body weight. Group 1, heifers that fed on pasture with good condition and group 2, heifers that fed on pasture with bad condition. Ovarian follicular function for both groups was observed bi-weekly using ultrasound. The mean number of follicles with 0-2 mm was greater in heifers of group 1 compared to heifers of group 2 (P<0.05). The mean number of small-sized follicles (3-5 mm) fluctuated during the experiment. However, the mean number of small-sized follicles in heifers of group 1 was significantly greater (P<0.05). Growth pattern of medium-sized follicles (6-9 mm) was similar for both groups during the experimental period (P>0.05). The size of large-sized follicles increased during the two first months of experiment (P<0.05), thereafter it was constant. The mean number of large follicles did not differ between experimental groups (P>0.05). Although the percentage of small-, medium- and large-sized follicles did not differ between experimental groups, the percentage of primordial follicle was significantly greater for heifers fed on good pasture (P<0.05). The size of the pre-ovulatory follicle was greater for heifers in group 1 than heifers in group 2 (P<0.05). The percentage of ovulation for treatments 1 and 2 was 100 and 10, respectively (P<0.05). These results show that nutrition may through stimulating of smaller-sized follicles (0-2 mm) and also increasing of the size of ovulatory follicle increase the proportion of ovulation.