Influence of short-term fasting during the luteal phase of the estrous cycle on ovarian follicular development during the ensuing proestrus of ewes

• Published in: Animal reproduction science Vol. 97; no. 3; pp. 356 - 363
• Main Authors: Alexander, B.M., Kiyma, Z., McFarland, M., Van Kirk, E.A., Hallford, D.M., Hawkins, D.E., Kane, K.K., Moss, G.E.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-02-2007
• Subjects: Animals; blood chemistry; corpus luteum; diameter; Dinoprost - pharmacology; Estradiol; Estradiol - blood; estrous cycle; Estrous Cycle - physiology; ewes; Fasting; fecundity; feed deprivation; Female; Follicle Stimulating Hormone - blood; follicle-stimulating hormone; Follicles; Food Deprivation - physiology; hypothalamus; Luteal Phase - physiology; luteinizing hormone; Luteinizing Hormone - blood; ovarian development; Ovarian Follicle - growth & development; ovarian follicles; Ovariectomy - veterinary; ovaries; Pituitary; pituitary gland; proestrus; progesterone; Progesterone - blood; Random Allocation; Sheep; Sheep - blood; Sheep - physiology; sheep feeding; synthetic prostaglandins; temporal variation; Time Factors; Sheep; Fasting; Follicles; Estradiol; Pituitary
• ISSN: 0378-4320; 1873-2232
• DOI: 10.1016/j.anireprosci.2006.01.012

Short-term fasting of mature ewes during diestrus results in increased serum concentrations of progesterone and a delayed pre-ovulatory surge release of LH. To determine if these changes in reproductive hormones influence subsequent follicular development, mature ewes observed in estrus were assigned randomly to control (
n
=
10) or fasted (
n
=
15) groups. Control ewes had ad libitium access to feed, whereas fasted ewes were not fed from day 7 through 11 of their estrous cycle. Daily blood samples were collected from control and fasted ewes throughout the fasting period. Fasting increased (
P
<
0.001) serum concentrations of progesterone (4.4
ng/mL versus 2.7
ng/mL [±0.3]). On day 12, all ewes were treated with 10
mg of PGF
2α and fasted ewes were returned to ad libitum feed. Ovaries were collected from ewes (
n
=
5 each group) at 0 and 72
h following PGF
2α in control and 0, 72 and 96
h in fasted ewes. Ovaries were weighed and small (≤2
mm), medium (3–4
mm), and large (≥5
mm) follicles were enumerated. Total numbers of follicles were less (
P
<
0.001) in fasted than fed ewes (14.6 versus 30.2 [±2.2]) at 0
h, but did not differ (
P
=
0.9) when numbers of follicles were compared at similar times before the anticipated LH surge (i.e., at 72
h versus 96
h in control and fasted ewes, respectively). Within follicular size class, numbers of small and medium follicles were decreased (
P
=
0.04) at 0
h in fasted ewes. Numbers of large follicles did not differ (
P
=
1.0) between groups. Although numbers of small and medium ovarian follicles in fasted ewes recovered by 96
h to values comparable to fed ewes at 72
h following PGF
2α, serum concentrations of estradiol 17β (
P
=
0.08) and FSH (
P
=
0.06) tended to be decreased in fasted ewes before the anticipated surge release of LH. Pituitary content of LH and FSH also tended to be lower (
P
≤
0.09) at 96
h in fasted ewes than at 72
h in control ewes, but did not differ (
P
≥
0.4) at hour 0 following PGF
2α. Hypothalamic and stalk median eminence contents of GnRH were not influenced (
P
≥
0.2) by fasting at any time period. Fasting during the luteal phase perturbs gonadotropin secretion and may influence fertility by causing a delay in ovarian follicle development.