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Home » Archive » 2020

TDK conference 2020

Estrus induction treatments (GnRH, eCG and longterm progesterone) used out of breeding season and their effect on hormonal changes and pregnancy rates in ewes
Selmeczi Petra Dorina - year 5
University of Veterinary Medicine Budapest, Department of Reproduction
Supervisors: Dr. Anna Csepreghy, Dr. Sándor Cseh

Abstract:

In sheep, it is a well researched problem that north from the 35°latitude ewes have a breeding season only during a short period of the year. In modern sheep farms, lengthening the breeding season and inducing the reproductive cycle have great economic importance.

In our experiment we induced the cycle of ewes outside of the breeding season, in the spring, using different sex-hormones (GnRH, eCG, and long-term progesterone. Our goal was to examine the effect of these protocols on the blood-progesterone and-oestradiol levels and on pregnancy rates.

We used 44 clinically healthy merino ewes. We divided the animals to 3 groups. The first was treated with progestagen and eCG; the second with progestagen and GnRH; and the third only with progestagen, this was the control group.

After the hormonal treatments, all groups were bred. We used hand mating with fertile, white- faced rams.In the next cycle, the ewes that were in heat again were bred with black-faced rams. This way we can see which mating led to the pregnancy from the phenotype of the lambs. Outside of the breeding season the hormonally induced heat is usually followed by one more cycle according to the literature. Because of this, we counted all the pregnancies from the first and second heat cycle in our results.

At the end of June, we performed ultrasound pregnancy examinations on all ewes. By this time, the ewes fertilized in the first cycle were about 45, the ones fertilised in the second were 28 days pregnant.

We took blood samples from each ewe on the day of hormonal treatments (1.), at the removal of intravaginal sponges (2.), at mating (3.), and on the day of pregnancy check (4.). We examined the blood progesterone and oestradiol levels. We did not find any significant difference in the progesterone levels among the three groups. At the time of the pregnancy check significantly higher levels of progesterone were found compared to samples taken at previous occasions.

We found significant differences in oestradiol levels between the 1. and 2., and the 2. and 4. occasions. We also found significant differences between the eCG and GnRH-treated groups at the 3. occasion.

At the time of ultrasound examination we found that 43 out of the 44 ewes were pregnant, (that means 97,73%).

From the 16 ewes that concieved after the first induced estrus, were born 18 white-faced lambs.

9 ewes concieved in the second estrus. The pregnancy rate was 56,81% altogether.



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