J. Anim Sci.
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J. Anim Sci. 1988. 66:3174-3184.
© 1988 American Society of Animal Science
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Influence of Infusion of Prostaglandin F2{alpha} (PGF2{alpha}) and Weaning on Surface and Histologic Populations of Ovarian Follicles in Early Postpartum Beef Cows1,2,

P. Villeneuve3, J. J. Dufour3 and L. A. Guilbault4,5,

Université Laval, Québec, Canada G1K 7P4 and Agriculture Canada Research Station, Lennoxville, Québec J1M 1Z3

Abstract

Twenty-four beef cows were infused continuously for 11 d (d 2 to 13 after parturition) into the descending aorta with either prostaglandin F2{alpha}-Tham salt (PGF2{alpha}; 33.5 mg/d; n = 12) or with .9% NaCl (saline; n = 12) vehicle. Cows from each infusion treatment then were assigned to three slaughter groups (G). Cows in G1 and G2 were suckled until slaughter on d 15 and 3 5, respectively, whereas calves in G3 were weaned on d 31 and cows were slaughtered on d 35 after parturition. Nonatretic and atretic (>4 pycnosis) antral follicles (>.15 mm) on ovaries ipsilateral to the previously gravid uterine horn were evaluated by histological techniques. Compared with saline infusion, PGF2{alpha} increased mean diameters of the largest (F1) follicles on the ipsilateral (d 15 and 35; P < .07) and contralateral (d 15; P < .07) ovaries (surface evaluation) as well as mean diameters of the largest (F1, d 35; P < .002), second- and third-largest (F2, F3, d 15 and 35;P < .01) nonatretic follicles (histologic evaluation) in suckled cows. Compared with suckled cows slaughtered on d 35, weaning on d 31 increased the number of medium follicles (3 to 5 mm), diameters of the three largest nonatretic follicles, percentage of large nonatretic follicles (> 3.67 mm) and mitotic index of class 3 (.68 to 1.57 mm) follicles in saline-infused cows. In contrast, in PGF2{alpha}-infused cows, weaning decreased (P < .05 to P < .001) all of these responses. Surface and histologic evaluations of follicular activity indicated that postpartum infusion of PFG2a stimulated development of large follicles. In response to weaning, PGF2{alpha} infusion favored development of those large follicles toward ovulation or atresia on nonovulated follicles.

Footnotes

1 Partial financial support by Conseil des recherches et services agricoles du Québec (#LA-85-B-114S) and by Canadian Association of Animal Breeders (CAAB) is gratefully acknowledged.

2 We thank R. S. Graham, Tuco Products Company, Orangeville, Ontario for supplying the PGF2{alpha} Tham salt, N. Ouellet for expert technical assistance and J. P. Charuest for assistance in statistical analysis.

3 Dept. de Zootechnie, Universite Laval, Quebec, Canada, G1K 7P4.

4 Agriculture Canada Res. Sta., Lennoxville, Quebec, J1M 1Z3.

5 Please address reprint requests to L. A. Guilbault. Agriculture Canada contribution no. 216.






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Copyright © 1988 by the American Society of Animal Science.