SUPEROVULATORY RESPONSE, EMBRYO RECOVERY AND PROGESTERONE SECRETION IN BORAN (BOS-INDICUS) COWS AFTER TREATMENT WITH EITHER PERGOVET OR PLUSET

Boran (Bos indicus) cows (n = 24) were allocated, based on body weight , to be treated with either a human menopausal gonadotropin (Pergovet) at doses of 1050 or 1350 IU or a porcine gonadotropin (Pluset) at dos es of 500 or 1000 IU. The cows were arranged in a balanced crossover d esign, and each cow was superovulated 3 consecutive times, which resul ted in a total of 72 superovulations. Superovulatory treatment started on Day 10+/-1 of the estrous cycle, and cows were treated for 5 conse cutive days. Estrus was induced with PGF(2) alpha (2 ml, im) at 72 h a fter initiation of treatment. Cows were inseminated at 12 and 24 h aft er the onset of estrus using 2 doses of semen each from a Friesian bul l. Daily blood samples were collected from die beginning of superovula tory treatment to the onset of estrus for determination of progesteron e concentrations. The mean (+/-SEM) estrus response interval after PGF (2) alpha and estrus duration were 33.1+/-4.1 and 9.3+/-0.5 h, respect ively, and did not vary between treatment groups. Similarly, the mean numbers of palpable corpora lutea and follicular cysts were 7.8+/-0.7 and 3.0+/-0.4, with no treatment effect. The number of superovulations which yielded embryos/ova was 50 (69.4%) and was higher (P>0.05) In c ows treated with Pergovet (75%) than with Pluset (63.9%). The mean num ber of embryos/ova recovered per superovulation was not affected by tr eatment and averaged 4.0+/-0.4, with a range from 3.2+/-0.9 to 4.6+/-1 .0 in the 4 treatment groups. There was no treatment effect on the mea n number of transferable embryos per superovulation, which averaged 3. 1+/-0.3. The mean numbers of embryos/ova and transferable embryos per embryo yielding superovulation were 5.6+/-0.4 and 4.3+/-0.4, respectiv ely. Return to natural estrus after the induced estrus averaged 43.3+/ -6.1 d (range 37.2+/-11.8 to 56.4+/-12.2 d), with no apparent treatmen t effect. The mean numbers of embryos/ova, transferable embryos arid i nterval to return to natural estrus did not vary between consecutive s uperovulations. Mean plasma progesterone concentrations dropped from 7 .6+/-0.3 ng/ml on the first day of superovulatory treatment to 1.3+/-0 .1 ng/ml on the day of induced estrus and did not differ between treat ment groups and between cows which yielded different numbers of embryo s/ova. Progesterone concentration on the day of estrus was negatively correlated with the number of embryos/ova (-0.29) and the number of tr ansferable embryos (-0.26), suggesting that progesterone concentration on the day of induced estrus can help to predict embryo yield and qua lity in Boran cows. It was concluded that both Pergovet and Pluset can be used to superovulate Boran cows with no residual effect of repeate d treatment on embryo yield and return to natural estrus. However, tre atment with Pergovet tended to increase the proportion of cows which y ielded embryos. Moreover, Pergovet given at 1050 IU and Pluset at 1000 IU resulted in the production of 19.4 and 39.0% more number of transf erable embryos than at 1350 and 500 IU, respectively.