| Autor: |
Patterson, A. L., Beard, J., Herrington, M. C., Rosasco, S. L., Soares, E. M., Northrop, E. J., Larimore, E. L., Rich, J. J. J., Amundson, O. L., McNeel, A. K., Chase, C. C., Perry, G. A., Summers, A. F., Cushman, R. A. |
| Zdroj: |
Journal of Animal Science; March 2017, Vol. 95 Issue: 1, Number 1 Supplement 2 p154-155, 2p |
| Abstrakt: |
Beef heifers that give birth within the first 21 d of their first calving season have greater lifetime productivity and longevity. A favorable relationship exists between the number of antral follicles detectable by ultrasonography and calving date in beef heifers, indicating greater lifetime fertility in cows with more antral follicles. In contrast, Bos indicuscows have more surface antral follicles than Bos tauruscows but exhibit no advantage in fertility. Prior studies demonstrated that despite having more antral follicles, Bos indicuscows have equal numbers of primordial follicles per ovary as Bos tauruscows. Bos indicuscows do have heavier ovaries with more stromal tissue than Bos tauruscows. This study served to further compare preantral follicle populations between Bos indicusand Bos tauruscows to test the specific hypothesis that number of primordial follicles per gram of ovarian tissue are decreased in Bos indicuscows compared with Bos tauruscows. Ovaries were collected from Bos indicuscows (n= 7) and Bos tauruscows (n= 42), weighed, fixed, and sectioned for histological evaluation to determine the number of primordial, primary, and secondary follicles per ovary. The total number of follicles per ovary was divided by the weight of the ovary to determine the number of follicles per gram of ovarian tissue. Data were analyzed using the GLM procedure of SAS (SAS Inst. Inc., Cary, NC) with species as a class effect. Ovaries from Bos indicuscows were heavier than ovaries from Bos tauruscows (12.6 ± 1.1 vs. 7.0 ± 0.5 g, respectively; P< 0.01). No difference was found between Bos indicusand Bos tauruscows in the number of primordial follicles per ovary (P= 0.64); however, Bos indicuscows had a greater number of primary and secondary follicles per ovary (P< 0.01). Upon being adjusted for ovarian weight, Bos indicuscows tended to have fewer primordial follicles per gram of ovary than Bos tauruscows (P= 0.06) but still had greater numbers of primary follicles per gram of ovary (P< 0.01). This suggests that the mechanisms controlling primordial follicle activation are different between Bos indicusand Bos tauruscows. From these results, we conclude that Bos indicuscows do not display enhanced fertility over Bos tauruscows because despite having more antral follicles, Bos indicuscows do not have larger ovarian reserves in comparison to the size of their ovaries. The USDA is an equal opportunity provider and employer. |
| Databáze: |
Supplemental Index |
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