2.6. Statistics Data were analysed using ANOVA or the general linear models procedure and
Ž .
included day, treatment, ewe and interactions where necessary SAS, Cary, NC .
Ž .
Multiple comparisons were made by the method of Tukey P - 0.05 . Prior to analyses, data were subject to Hartley’s test for heterogeniety of variance and logarithmic
transformations were done where necessary to yield homogeniety of variance. All values given are the mean SEM.
3. Results
Ž .
The life span of the ovulatory follicle was greater P - 0.01 in the ewes that
received a single long-duration sponge than those that received three short-duration
Ž .
Fig. 4. The mean SEM daily diameter of the largest follicle in each wave of follicular growth observed in Ž
the long-duration treatment group ns8, 60 mg medroxyprogesterone acetate sponge inserted on Day 5 of the .
Ž .
oestrous cycle, and removed on Day 19 treatment group. Prostaglandin arrows was given on Days 6 and 7. Ž
. Ž .
Three ewes ovulated a follicle from the second wave a and five ewes ovulated a follicle from the third
Ž . wave b of follicle growth. A total of three ewes developed identified follicles while the prolonged follicle
Ž .
was present dotted lines .
Ž .
sponges and control ewes Table 1 . The day of emergence of the ovulatory follicle was Ž
. similar P 0.05 between ewes in the control and long-duration groups, but was later
Ž .
Ž .
P - 0.01 in ewes in the short-duration group Table 1 . The maximum diameter of the Ž
. ovulatory follicle in ewes in the long-duration group was greater P - 0.01 than that in
Ž .
ewes in the short-duration and control groups Table 1 . All of the 21 ewes ovulated a single follicle. Based on once-a-day heat checking with raddled rams, the time from
Ž .
sponge withdrawal to oestrus was not different P 0.05 between groups of ewes that Ž
. Ž
. were treated with a single 2.3 0.4 days or multiple 3.0 0.5 days sponges.
Ž .
The diameter of corpora lutea decreased P - 0.01 after prostaglandin injection in sponge-treated ewes and were no longer ultrasonically visible after Day 13.7 0.6 of
Ž .
the cycle Fig. 1 . On Day 15 and between Days 17 and 19 there were more large Ž
. follicles present G 6 mm in diameter, P - 0.05 and between Days 15 and 18 plasma
Ž .
concentrations of oestradiol were greater P - 0.05 in long-duration ewes than short- Ž
. Ž
. duration ewes Fig. 1 . On Days 18 to 20 there were fewer P - 0.05 medium-sized
Ž .
follicles 4 and 5 mm in diameter present in the long-duration ewes than short-duration Ž
. Ž
. ewes Fig. 1 . There was no difference P 0.90 between groups for the numbers of
Ž small follicles 2 and 3 mm in diameter, overall mean 2.8 0.3 follicle per ewe per
. day .
During oestrous cycles, there were two or three waves of follicular growth in ewes in Ž
. the control and long-duration groups Figs. 2 and 4 , and three, four or five waves of
Ž .
follicular growth in ewes in the short-duration group Fig. 3 . The ovulatory follicle developed in the last follicular wave in all cases. An identified follicle grew and
regressed while the prolonged follicle was present in three of the eight ewes in the Ž
. long-duration group Fig. 4 . In each case the follicle emerged and grew to a maximum
Ž .
diameter of 4 mm and started to regress before the day of ovulation Fig. 4 .
Table 2 Ž
. Characteristics meanSEM of circulating LH and oestradiol concentrations in ewes on Day 18 of the
Ž .
oestrous cycle. Short-duration ewes ns 5 received a progestagen sponge on Day 5 of the oestrous cycle that Ž
. was replaced on Days 10 and 15, and removed on Day 19 of the cycle. Long-duration ewes ns 5 had a
sponge inserted on Day 5 and removed on Day 19 of the oestrous cycle. Both groups received prostaglandin on Days 6 and 7 of the cycle. Blood samples were collected every 12 min for 8 h for the pattern of LH in
Ž .
circulation and oestradiol concentrations are based on a single the first sample Short-duration
Long-duration Significance
Ž .
Ž .
Ž .
ns 5 ns 5
P - Circulating LH
y1
Ž .
Mean ng ml 0.360.05
0.610.14 0.09
y1
Ž .
Basal ng ml 0.320.02
0.460.08 0.10
Pulse amplitude 1.250.36
0.950.24 0.50
y1
Ž .
ng ml Pulse frequency
0.80.4 3.21.1
0.03 Ž
. pulses per 8 h
Mean oestradiol 0.540.08
1.150.09 0.01
y1
Ž .
pg ml
On Day 18 of the cycle, LH pulse frequency and mean oestradiol concentrations were Ž
. Ž
. greater P - 0.03 in the long-duration than the short-duration ewes Table 2 . There
Ž .
Ž .
was also a tendency for mean P - 0.09 and basal P - 0.10 LH concentrations to be Ž
. greater in ewes in the long-duration than the short-duration group Table 2 .
4. Discussion
