CONICET | Buscador de Institutos y Recursos Humanos

The objectives of the present study were to evaluate ovarian changes in cows following treatment with Ca2+-Naloxone. The effect of treatment on hormone serum levels and the disappearance/persistence of cysts were evaluated in cows with cystic ovarian disease (COD). Forty pluriparous high yielding Argentinean Holstein cows affected by COD at least 45 days after calving were injected, via epidural at lumbo-sacral level, with 0.6 mg of Naloxone dissolved in 3 ml of Ca2+ gluconate 20% (Ca-Nx) together with 2ml of GnRH analogue. Blood samples were taken immediately before the treatment and 2 week after treatment for serum LH, FSH, estradiol, progesterone and cortisol determination. A significant reduction in the cyst mean size was observed and 77.5% of cows with ovarian cysts began cystic regression or recovery of the cyclic ovarian activity within 2 weeks after treatment. The proportion of recovered cows was higher than that of cows only treated with a GnRH analogue. We have observed no adverse effects following treatment. Before treatment, the progesterone level was less than 1 ng/ml in all animals, but it underwent a significant 8-fold increase 2 weeks after treatment. No differences in concentrations of LH, FSH, estradiol and cortisol were observed. To our knowledge, this is the first comprehensive examination of the hormonal and follicular response to Ca-Nx plus GnRH treatment in high yielding cows with COD. The results of the present study are strong evidence that this treatment triggers cystic regression and follicle development leading to a normal oestrus with sexual behaviour and fertile ovulations. Also, the therapeutic efficacy of Ca-Nx indirectly demonstrates an involvement of endogenous opioids in the COD pathogenia. In conclusion, Ca-Nx is an effective treatment for COD in dairy cattle and the treatment resulted in ovulation and formation of copora lutea. Key words: Cystic ovarian disease, Dairy Cattle, Naloxone, Treatment

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