Ga. Bo et al., OVARIAN FOLLICULAR WAVE EMERGENCE AFTER TREATMENT WITH PROGESTOGEN AND ESTRADIOL IN CATTLE, Animal reproduction science, 39(3), 1995, pp. 193-204
An experiment was designed to evaluate the effects of treatment with p
rogestogen and estradiol-17 beta (E-17 beta), in combination, at diffe
rent stages of development of the dominant follicle, on follicular dev
elopment and subsequent wave emergence, Cross-bred beef cows (n = 12)
and heifers (n = 25) were randomly allocated to one of four treatment
groups on Day 0 (ovulation), Treatment groups were untreated control a
nimals and those that were given progestogen ear implants on Day 2, 5
or 8 and injected intramuscularly with 5 mg E-17 beta in sesame oil on
Day 3, 6 or 9, respectively, Ovarian ultrasonography was performed da
ily from Day 0 until progestogen implant removal, 4 days after the eme
rgence of the post-treatment follicular wave. The mean (+/- SEM) time
(days) to cessation of growth and onset of regression of the dominant
follicle of the first wave were earlier (P < 0.05) in the Day 3 treatm
ent group than in the control group (3.6 +/- 0.2 vs. 5.6 +/- 0.4 and 7
.0 +/- 0.3 vs. 1 1.0 +/- 0.6, respectively). Characteristics of the do
minant follicle of the first wave in the Day 6 and Day 9 treatment gro
ups were not different from those of the control group. However, treat
ment on Day 9 resulted in earlier (P < 0.05) cessation of growth and o
nset of regression of the dominant and largest subordinate follicle of
the second wave than in the control group (9.6 +/- 0.2 vs, 13.4 +/- 0
.7 and 11,5 +/- 1.3 vs, 17.1 +/- 0.9, respectively), Follicle wave dyn
amics was affected by early emergence of the second follicular wave in
heifers treated on Day 3 (Day 7.3 +/- 0.3) and delayed emergence in t
hose treated on Day 6 (Day 10.7 +/- 0.2) compared with the control gro
up (Day 8.6 +/- 0.3; P < 0.05), Furthermore, treatment on Day 9 result
ed in earlier (P < 0.05) emergence of the third wave (Day 13.1 +/- 0.3
) than the control group (Day 15.3 +/- 0.6). The interval from treatme
nt to wave emergence was not different among treatment groups (4.3 +/-
0.2 days after E-17 beta and supported the hypothesis that treatment
with progestogen plus E-17 beta results in consistent emergence of a n
ew follicular wave, regardless of the stage of development of the domi
nant follicle at the time of treatment. It was concluded that treatmen
t with progestogen and E-17 beta in combination can be used effectivel
y to control and synchronize follicle wave development.