Akademik Veri Yönetim Sistemi
Turkish & Italian Joint International Animal Reproduction Congress, 1th National Reproduction and Artificial Insemination Science Congress,, Antalya, Türkiye, 10 - 13 Ekim 2024, ss.275-278
Introduction and aim
Small ruminants are the major mainstay of animal sourced foods in
developing and transitioning countries. However, sheep and goats are
short-day, seasonally polyestrous animals with a limited reproductive
season in a year. Therefore, estrous synchronization and breeding control
help to improve reproductive performance (1,2). The sheep breeders
prefer maximum prolificacy for flock productivity. Increased reproductive
efficiency in the flock positively affects economic parameters, annual milk
and meat production, and farm profitability (3). Studies on the enhancement
of reproductive productivity of nulliparous ewes are still ongoing, and the
reproductive management efficiency of these animals still needs to be
defined (4). Based on this uncertainty, the present study aims to determine
the efficacy of GnRH administration at the beginning of synchronization
protocol in nulliparous Assaf sheep at the end of the breeding season.
Methods
The study was carried out at the end of the breeding season (from the
beginning of December to the end of the parturition period) on a single
commercial farm. The animals’ body condition score ranged from 2.5 to
3.5 (on a 1-5 scale), and they were between 7 and 9 months old. Blood
samples were collected at the beginning of the study (day 0) from all
ewes and after intravaginal sponge removal (day 7) from synchronization
groups for progesterone analysis. The nulliparous ewes were randomly
divided into three groups. Ewes in Group I (n=49) received an intravaginal
sponge and were injected with GnRH (4 μg of busereline acetate) at the
time of sponge insertion (day 0). On the day of sponge removal (day 7), all
ewes received d-cloprostenol and 500 IU eCG. The rams were joined into
the herd for one ram for four ewes on day 8, and the onset of the estrous
of ewes was noted according to symptoms. In Group II (n=45), the same
treatment was received except for GnRH injection on day 0. Group III
(n=23) was designed as a control group, and any hormonal treatments were
not administered, and the rams were joined. Pregnancies were confirmed
on day 25 by transrectal ultrasonography and on day 45 by transabdominal
ultrasonography. Estrus response, pregnancy rates, embryonic death, aborts,
parturition rates, twinning rates, fecundity, prolificacy, and fertility rates were
noted. Vaginal discharge characteristics after sponge removal were observed
and scored.
Results
The mean serum progesterone concentrations of Group I, Group II, and
Control on Day 0 were 1.98, 1.75, and 3.09 ng/ml, respectively. The vaginal
discharge scores were statistically different between score 1 and score 2
in the synchronization groups (P<0.05). However, the vaginal discharge
characteristics and scores did not affect embryonic mortality and pregnancy
rates significantly (P>0.05). The estrus rates were similar Group I and Group
II (93.87% and 95.55%, respectively) (P>0.05) but higher than the control
group (56.52%) (P<0.05). The estrous duration and estrus onset were also
insignificant between hormone treatment groups (P>0.05). The pregnancy
rates on day 25 were higher in the Group I and Group II (79.59% and 93.33%,
respectively) than in the control group (52.17%). The fertility rate was significantly higher in the synchronization groups than in the control group
(P<0.05). The highest fecundity and prolificacy rates were found in Group II.
Discussion and conclusions
Ano-Perello et al. (5) reported that GnRH treatment in progesterone-based
synchronization protocols increases estrus response and reproductive
efficiency in ewes by improving follicular turnover. On the contrary, our
results showed that the GnRH administration did not positively affect estrus
response and other reproductive performances in nulliparous Assaf ewes.
A different breed, Segurena meat ewes, was treated in the study by Ano-
Perello et al. (5). Also, well management and environmental conditions
could affect the results. The vaginal drainage, pH, and microbiota could be
failed during intravaginal progesterone usage in sheep. The researchers
reported that the long-term treatments give decreased pregnancy rates
than the short-term treatments in accordance with vaginal discharge
characteristics (6). On the other hand, there are contrary results that the
vaginal discharge wasn’t affected the conception rates (7). In the present
study, the pregnancy rates were similar in the synchronization groups with
different vaginal discharge scores.
In conclusion, the GnRH administration on progesterone-based protocol
did not positively affect the reproductive values at the end of the season in
the nulliparous Assaf ewes. It was concluded that the economic burden and
workload should be evaluated during the planning of hormone usage and
treatment protocol.
Keywords: Assaf ewe, GnRH, progesterone based synchronization, fertility,
vaginal discharge.