Effects of a copper-bearing intrauterine device on the ovarian function, body weight gain and pregnancy rate of nulliparous heifers.
A copper-bearing intrauterine device (IUD), designed to cause a slight distention of the uterus, was inserted through the cervix into each uterine horn of 230 heifers; an additional 230 heifers served as the control group. Blood was drawn at 0, 1, 2, 20 and 120 d for progesterone and testosterone assays. The heifers were checked twice daily for estrus and examined at 0, 60 and 120 d for weight gain. Thereafter they were bred over a 120-d period. The IUD caused anestrus in 98% of the heifers, with a daily weight gain 25.5 % higher than in the control heifers. Moreover, the device was 100% effective in preventing pregnancy. At 20 and 120 d after IUD insertion progesterone levels averaged 0.7 ng/ml, which was 4 to 5 times lower than in the control animals, suggesting a failure in ovulation or in corpus luteum (CL) formation due to the IUD. Simultaneously, testosterone values were increased up to 8 times in IUD-treated heifers, reaching a mean concentration of 163 pg/ml. Associated histological evaluations of the ovaries from UD-treated heifers revealed the presence of 2 or more cysts per ovary, with marked hyperthecosis in many antral follicles in which the granulosa cell layers were either thinned or lacking. The results suggest that the action of the copper-releasing IUD used in this study resulted in high contraceptive efficiency but also in disturbance of ovarian function. Our findings further raise the possibility of a cause and effect relationship between hyperandrogenism and the higher body weight gain observed in heifers treated with the IUD.
Turin
E M
EM
Centro de Investigacion en Reproduccion Humana y Experimental del Centro de Educacion Medica e Investigaciones Clinicas (CEMIC) Buenos Aires, Argentina.
Nagle
C A
CA
Lahoz
M
M
Torres
M
M
Turin
M
M
Mendizabal
A F
AF
Escofet
M B
MB