Trans-rectal ultrasound monitoring of the cystic ovarian structures in high yielding cows treated with different doses of GnRH analogue – field trial
2011
Atanasov, B. | Esmerov, I. | Nikolovski, M. | Dovenski, T., Ss. Cyril and Methodius University, Skopje (The Former Yugoslav Republic of Macedonia). Faculty of Veterinary Medicine
The aim of this investigation was to observe the fate of ovarian cystic formations after application of different concentrations of GnRH. Follicular structures with diameter exceeding 25 mm, persisting more that 10 days on one or both ovaries without functional corpus luteum are regarded as ovarian cysts. Cystic ovarian disease – COD as one of the major ovarian dysfunction, stands for a significant reproductive problem in dairy cows in R. Macedonia. From the available data, its occurrence ranges between 5-25% in high yielding dairy cows. In practice, the true incidence of COD may be even 32% or higher due to the high incidence of spontaneous resolution in cows less than 60 days postpartum. During a routine ultrasound examination by 7.5 MHz rectal linear probe at one dairy farm, 12 cows with ovarian cysts (COD) were identified. Based on the thickness of the cyst wall, nine cows with follicular cysts (less than or equal to 3 mm) and three cows with luteal cysts (greater than 3 mm) were diagnosed. Both groups of cows were treated with adequate therapy, GnRH or PgF2 alpha, respectively. The group with GnRH was divided into three subgroups according to the dose of GnRH (500, 250 and 100 micro g). The results demonstrate that 7/9 (77.7%) of the cows resumed their cycle activity after day 11, regardless of the applied GnRH dose. Five cows (5.7 or 71.42%) formed new functional corpora lutea, while 28.58% cows (2 of 7) had lutenized cyst and all came in heat three days later after administration of prostaglandis. In conclusion, independently of the GnRH dose, the cows responded individually presenting two pathways of reaction. First, ovulating or luteinization of one of the subordinated follicles and forming functional corpus luteum regardless of the present cystic formation on the same or on the opposite ovary. Second, increase of luteal tissue within the cyst and reducement of antrum space, leading to full luteinisation of the cyst without forming accessory corpora lutea.
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