The literature relating to ovarian activity and related phenomena, endoscopic observation of the ovaries, the various methods for the control of ovarian activity such as synchronisation of ovulation, superovulation and the collection and transfer of ova in the cow was reviewed.
The existing technique to directly observe the cow's ovaries with an endoscope through a retained cannula in the paralumbar fossa were modified to overcome some of the problems encountered by earlier workers. The ovarian activity of a normal cycling cow and a superovulated cow was observed. The modified technique enabled the operator to locate easily the ovary and observe ovarian activity. However, only the ovary on the cannulated side, in each cow, could be distinctly observed.
The superovulatory response of cows' ovaries, during follicular and luteal phases of the oestrous cycle, and to two different dose levels of pregnant mare serum gonadotrophin, was studied. A significantly greater number of follicles ovulated (P<0.01) in cows which received 1500-2000 I.U. pregnant mare serum gonadotrophin during luteal phase (mean ovulation ±SE = 12.2 ± 2.4) than in cows that received the same dose of pregnant mare serum gonadotrophin during follicular phase (mean ovulation ± S.E. = 4.7 ± 2.4). Increasing the dose of pregnant mare serum gonadotrophin increased the number of ovarian follicles stimulated in cows but it did not affect the percentage of ovulations. By increasing the dose of pregnant mare serum gonadotrophin from 1500 - 2000 I.U. and from 2000 I.U. - 3000 I.U. during the first and second superovulatory treatments, the refractoriness of the bovine ovary to pregnant mare serum gonadotrophin was partly reduced.
The superovulatory response of the ovaries of prepuberal calves to different hormonal treatments was investigated. The combination of pregnant mare serum gonadotrophin, oestrogen and human chorionic gonadotrophin was found to be superior to the combination of either progesterone, pregnant mare serum gonadotrophin, oestrogen and gonadotrophin releasing hormone or pregnant mare serum gonadotrophin, oestrogen and gonadotrophin releasing hormone. A mean (±SE) of 15.5 ± 3.8 ovulations were recorded in 3 calves using the former treatment whereas 3.0 ± 3.8 and 1.7 ± 3.8 ovulations were recorded in two groups of 3 calves each using the latter two treatments respectively.
Plasma progestin levels in superovulated cows and calves were estimated by the competitive protein binding technique after Johansson (1970) . Plasma progestin levels in both the cow and the calf increased with the increase in the number of corpora lutea (r = 0.97, n = 4 for the cow and r = 0.99, n = 4 for the calf). Plasma progestin levels in cows increased about 24-48 hours after the administration of pregnant mare serum gonadotrophin. These high plasma progestin levels returned to the normal pro-oestrus levels after the administration of prostaglandin. In one cow, which did not exhibit standing oestrus no drop in progestin level was recorded.
Ova from superovulated cows were recovered by midventral laparotomy and flushing of the uterus through the Fallopian tubes. Out of 480 ovulations recorded in 40 donor cows 294 (61.2%) ova were recovered of which 222 (75.5%) were fertilised. An average of 5.6 fertilised ova were recovered per donor cow operated. Incomplete exposure and blockage of the Fallopian tubes, at the uterotubal junction, were the two main problems encountered. The former was noticed in dairy cows with large mammary glands. The latter was encountered while collecting blastocysts (8-9 day old fertilised ova). Due to these two problems the endometrium was ruptured in 4 cows at the time of flushing the uterus. Attempts to collect ova in superovulated cows either by cannulating the Fallopian tubes or by fixing silastic balloon catheters in the anterior third of the uterine horn were unsuccessful. The problems associated with these techniques and the possible reasons for failure were discussed.
Preliminary trials were conducted to develop an apparatus to collect ova non-surgically from superovulated cows. Based on these trials a rigid ova collecting apparatus was developed. Its success rate was compared with that of a flexible type apparatus. Ova were collected from 12 of 15 superovulated cows using the rigid apparatus and from all 20 superovulated cows using the flexible apparatus. The mean number of ova recovered was 3.1 and 4 for the rigid and the flexible apparatus respectively. The advantages and disadvantages with the recovery of ova in the cow using these two types of apparatus were discussed. No significant difference was achieved in the number of ova recovered using these two types of apparatus. However, the flexible type apparatus caused less trauma to the uterus.
A technique was developed to transfer ova by cannulating the Fallopian tubes of recipient cows. Two of eight cows prepared by this technique became pregnant and gave birth to live normal calves. The possible reasons for non-conception of the remaining six cows and the problems encountered with this technique were discussed. The presence of polyethylene tubes in the Fallopian tubes of these cows did not appear to alter the cyclic activity of the ovaries. The polyethylene tubes of two of these cows were found to be partially blocked. However, these two cows became pregnant when ova were transferred transcervically.
Preliminary trials were conducted to develop a simple non-surgical ova transfer technique in the cow. Twin calves were produced in a cow by transferring two fertilised ova into the uterine horn ipsilateral to the ovary containing the corpus luteum. Subsequently, the success rate of this technique was studied in 24 recipient cows. When ova were transferred under controlled conditions (Laboratory transfer) to 12 recipient cows, 10 (83.3%) and 8 (66,7%) were tested pregnant at 45 and 90 days after transfer respectively. When transfers were made to 12 recipient cows under field conditons (Paddock transfer), 9 (75%) and 5 (41.7%) were tested pregnant at 45 and 90 days after transfer respectively. The difference in pregnancy rates between laboratory and paddock transfers was not statistically significant.