A large dairy herd was established free of bovine leukosis virus (BLV) infection at the US Dairy Forage Research Center, Madison, Wis. Cattle introduced into the herd originated from BLV-infected herds, but only those negative for BLV antibodies by an agar gel immunodiffusion test were accepted there. Cattle that were found to be seropositive after their arrival at the new facility were promptly removed. Embryo transfer and artificial insemination were used to introduce new genetic stock into the herd. All recipients receiving embryos from BLV-positive donors and the 30 calves born from the successful transfers were seronegative at 21 months for BLV antibodies. Thus, under these conditions, embryo transfer and artificial insemination did not spread BLV. The agar gel immunodiffusion test was effective in screening cattle for BLV antibodies.

The objectives were to determine if early in gestation (less than day 30) an embryo in the ipsilateral horn increases the survival rate of an embryo in the contralateral horn and if later in gestation (greater than day 30) the presence of two embryos adversely affects the survival of both embryos in cattle. The experiment involved surgical embryo transfer. Sixty Holstein heifers were assigned to 4 groups: group 1) sham bilateral transfers, group 2) one embryo inserted ipsilateral to CL, group 3) one embryo inserted contralateral to CL, and group 4) one embryo inserted into each horn. Diagnosis of pregnancy and ovarian activity were recorded from day 7 or 8 (surgery) to day 110. Results indicated that the rate of embryo survival early in pregnancy (less than day 30) in heifers with the embryo inserted contralateral to the CL (33%, group 3) was increased (P = 0.05) when an embryo was also inserted into the ipsilateral horn (67%, group 4). The hypothesis that the ipsilateral embryo would have a protective effect on the contralateral embryo was, therefore, supported. This may have been due to the prevention of luteolysis by the ipsilateral embryo. However, when an embryo was present in each horn considerable loss occurred greater than day 30 resulting in a low survival rate by day 110 (27%). The hypothesis that the presence of two embryos would decrease the survival probability of both embryos later in gestation was, therefore, supported.

The effect of multiple ampules of frozen semen on conception rate in superovulated Holstein heifers was studied using 3 breeding regimens (n=25): 1 ampule at 12 hr (0 hr = beginning of estrus), 3 ampules at 12 hr, and 1 ampule at each of 0, 12, and 24 hrs. There was no significant effect of breeding regimen on recovered number of ova or percentage of fertilized ova. In another project, months during which heifers were superovulated with PMSG (5–8 heifers/month) did not significantly affect rate of superovulation (number of CL). Clinical records for 173 superovulatory treatments in 150 Holstein heifers were studied to obtain preliminary information on efficacy of treatment regimens, repeatability of response within heifers, and relationships between superovulation and length of estrous cycle; where indicated, contemporary, nontreated heifers were used for comparisons. Efficacy of PMSG vs FSH treatments did not differ in number of CL or number of ova recovered, but percentage of recovered ova that were transferable was greater (P<.05) for FSH (58.3) than for PMSG (42.9). There was an intraclass correlation coefficient of 0.33 (n=37) indicating repeatability within heifers in the magnitude of response to superovulatory treatment. Mean length (days) and coefficient of variation were significantly greater for superovulatory estrous cycles (cycles during which multiple CL were present; n, 141; mean, 31.2; SE, ± 1.2; CV, 46.2%) than for contemporary cycles in nontreated heifers (n, 63; mean, 20.8; SE, ± 0.4; CV, 13.9%). Treated heifers with short cycles (<15 days) had fewer CL (6.8 ± 1.4; mean ± S.E.) than heifers with intermediate cycles (15 to 27 days; 9.4 ± 0.6) or prolonged cycles (>27 days; 11.5 ± 0.7). Collection of an ovum from nontreated heifers resulted in shortening (P<.05) of the estrous cycle (n, 16; mean, 18.1 days) when compared to cycles from contemporary heifers in which collections were not done (n, 16; mean, 20.4 days).

The hypothesis of a unilateral uteroovarian relationship between location of embryos and maintenance of corpora lutea (CL) was tested in superovulated cattle. Ovulations were induced in both ovaries and a uterine horn was isolated subsequent to insemination to produce unilateral pregnancy. The mean weight of CL on day 24 was greater (P<.05) on the gravid side (2580 mg) than on the nongravid side (1200 mg; n=5), supporting the hypothesis. Involvement of the main uterine vein in the unilateral pathway between a gravid horn and the adjacent ovary was demonstrated in an experiment which utilized separation of uterine horns, anastomosis of uterine veins between sides, and insertion of embryos into one side by embryo transfer. Mean weight of CL on day 24 was less (P<.05) when the gravid horn was contralateral to the CL (950 mg; n=3), than when the gravid horn was ipsilateral to the CL (4760 mg) or when the gravid horn was contralateral to the CL and the uterine vein from the contralateral side was anastomosed to the vein on the ipsilateral side (3580 mg; n=3).

SUMMARY Four experiments were conducted to define reasons for failure of nonsurgical transfer of bovine embryos. Single embryos were transferred to the uterine horn ipsilateral to the corpus luteum-bearing ovary 6 to 9 days after estrus. All recipient heifers were within ± 24 hours of heat synchrony with the donors. All nonsurgical transfers were accomplished, using the Cassou apparatus with 0.5 ml French straws. Pregnancy was determined by rectal palpation on day 40 (31 to 34 days after transfer). In experiment 1, when embryos were transferred surgically, pregnancy rates were not different between the midventral approach (11/14, 77%) and the flank approach (10/14, 71%) but were lower (P < 0.05) when transfers were done nonsurgically (3/14, 36%). In experiment 2, transfer to the midportion of the uterine horn was compared with transfer to the cranial end of the uterine horn. Embryo survival in the midportion of the uterine horn tended to be higher (P < 0,06) when embryos were placed nonsurgically (15/20, 75%) than when transfer was accomplished surgically (9/20, 45%). Surgical transfer to the midportion of the uterine horn was not affected by sham nonsurgical manipulation. Pregnancy rate was not different between nonsurgical transfer to the middle portion of the uterine horn (15/20, 75%) and surgical transfer to the cranial portion (12/20, 60%). In experiment 3, pregnancy rate was not affected by digital compression to the uterine horn during withdrawal of the Cassou instrument after nonsurgical transfer. Pregnancy rates in experiment 4 were not different between the midportion of the uterine horn and the caudal portion of the uterine horn, using nonsurgical embryo transfer. An operator experienced in nonsurgical embryo transfer obtained higher pregnancy rates (23/40, 58%) than did an operator with no previous nonsurgical embryo transfer experience (14/40,35%, Ρ < 0.05). Amount of time to penetrate the cervix did not affect transfer results; however, increasing the time that the Cassou catheter remained in the uterus tended to decrease pregnancy rates (P < 0.07). It is concluded that experience in nonsurgical transfer is important in achieving acceptable success rates and that specific regional placement of the embryo in the uterine horn ipsilateral to the corpus luteum-bearing ovary is not imperative for nonsurgical transfer success.

Embryos were non-surgically recovered from superovulated donors. Two trials of ipsilateral single embryo transfer were performed with the Japanese AI instrument.For the first trial, neither the AI instrument nor the cervical expander were ensheathed. The overall pregnancy rate was 33.3 % (2226). Pregnancy rates obtained from three groups with different media were almost identical.In the second trial, both the AI instrument and the cervical expander were covered with a paper sheath to minimize uterine infection. The overall pregnancy rate after the second trial was 59.1 % (1322).

Study was made of effects of administration of bovine follicular fluid (FF) on the ovaries of sheep and cattle. The FF was obtained by aspiration of follicles from ovaries obtained at a slaughterhouse. Diestrous ewes treated with prostaglandin F2α (PG) had an increased interval to estrus when treatment with PG was followed by treatment with whole FF (7.0 ± 0.8 vs 2.0 ± 0.0 days for controls, mean ± SEM). Treatment of diestrous heifers with PG and FF resulted in similar increases in the interval from PG to estrus and ovulation. Laparotomy of ewes and palpation of heifers after treatment with PG indicated no differences in diameters of corpora lutea. Laparotomy of ewes after 8 days of treatment with FF indicated significant follicular inhibition: diameter of largest follicle, 6.3 ± 0.8 vs 2.5 ± 0.3 mm; number of follicles greater than 3 mm, 2.5 ± 0.5 vs 0.0 ± 0.0, for control and treated ewes, respectively. The delay in return to estrus, therefore, was due to inhibition of follicular development rather than to an interference with luteolysis. Crude fractionation of whole bovine FF in an attempt to attribute the biological activity to either a charcoal extractable substance (steroid) or a substance denaturable at 100°C (protein) had mixed results. In the ewe, both charcoal extracted FF and heated FF were as effective as whole FF in delaying estrus. In one experiment with heifers, neither preparation was effective alone, but the combination was as effective as whole FF. When treatment with charcoal extracted FF was repeated in a second experiment, it was found to be effective alone. It was concluded that the bovine FF contained a nonsteroidal substance that had follicle inhibiting activity in cattle and sheep.

A technique of visual assessment of cattle for reproductive efficiency, described by Professor Jan Bonsma of South Africa, was evaluated in two well-managed large herds of 12 to 34 Brahman cross heifers and cows located in the dry tropics of north Australia. Individual lifetime performance records were available for all animals. Experienced cattlemen carried out the assessments. Higher scores were previously claimed to indicate higher fertility.The technique had high repeatability (0.7) and was quickly learned by the assessors. Scores from visual assessment had no useful predictive value for either heifer or cow fertility or for growth rate up to 27 mo of age, although 2.5-yr-old heifers which were scored as subfertile matured into 4% smaller cows than heifers which had scored higher. Scores decreased as fatness increased (P < 0.05).Some biases in visual assessment occurred. Lactating cows scored higher than nonlactating cows (P < 0.05), independently of their reproductive record. Red and grey cows scored higher than brindle and black/brown cows (P < 0.05). Bonsma scores were not influenced by the percentage of Brahman in the genotype. Significant, but apparently random, age effects on scores also occurred.It was concluded that the visual assessment criteria described by Bonsma were of no practical value in assessing potential productivity of breeding animals in well-managed Brahman cross cattle in the dry tropics.

The unilateral relationship between embryo and corpus luteum was studied in two experiments in Holstein heifers. Two fertilized ova were inserted into one uterine horn of recipient heifers on Day 6 after estrus. Recipients were given progesterone from Day 13 through Day 23 and were necropsied on Day 24 (18 days after ova transfer). Corpora lutea were weighed and classified as maintained or regressed. In Exp. 1, the uterine horns were separated and the fertilized ova were inserted ipsilateral (group 1, 5 heifers) or contralateral (group 2, 5 heifers) to the CL. Nine of 10 heifers were pregnant at necropsy. Mean CL weight for group 1 (3725 mg) was greater (P<0.01) than that for group 2 (1300 mg). Results indicated that in heifers with a surgically isolated uterine horn a unilateral utero-ovarian mechanism was involved in maintenance of the CL during early pregnancy. Experiment 2 was designed to determine if embryos inserted into the uterine horn contralateral to the CL in uterine-intact heifers would maintain the CL and, if so, whether the luteotropic message passed from gravid to nongravid side through the uterine body and horns or through the intercornual area. Recipient heifers were randomized into 4 groups (n=4): 1) uterine-intact controls; 2) ipsilateral horn transected, intercornual ligament intact; 3) uterine horns intact, intercornual ligament severed; 4) ipsilateral horn and intercornual ligament severed. Mean CL weight was smaller (P<0.05) in group 1 (2900 mg), group 2 (1405 mg) and group 4 (578 mg) than in group 3 (4848 mg). There was a significant difference between groups 1 and 3 although the CL in all heifers in both groups were classified as maintained. Mean CL weight was not significantly different between groups 2 and 4. Results indicated that embryos transferred to the contralateral horn were capable of maintaining the CL if the uterine horns were not separated. The passage of the luteotropic message from gravid to nongravid side was exerted through the uterine body and horns rather than through the intercornual area and is most likely attributable to the growth of embryonic membranes into the nongravid horn.

The uteri of 34 heifers were flushed for ova six to nine days following estrus using a single cannula nonsurgical technique. The technique involved the infusion of fluid by gravity and agitation within the uterus by to-and-fro action of a syringe followed by unassisted fluid collection. Each horn was flushed five times using 30–150 ml of flushing fluid per flush. Recovered fluid (flushing fluid plus uterine secretion) was an average of 95% of the volume of the fluid inserted. Ova were recovered from 12 of 19 nontreated, single ovulating heifers (63%) and from all of 15 superovulated heifers (mean and S.D. for number of ova, 6.3 ± 4.4/ superovulated heifer; range, 1 to 14 ova). Based on the number of corpora lutea, the ova recovery index was 54% as averaged over the 15 superovulated heifers. The technique has been used in 4 additional superovulated heifers with modification (increased number of flushes to 8) subsequent to the termination of the planned project. Recovery index for the first 5 flushes was 58%. However, some ova were recovered in the 6th, 7th, and 8th flushes resulting in an apparent improved recovery index of 69%.

Twenty-four Holstein heifers were used in a 2 × 2 factorial experiment to study the effect of unilateral ovariectomy, performed on day 8 of the estrous cycle, upon cycle length and upon follicle number and size in the retained ovary at the next estrus. The factors were the number of ovaries (one or two) and the presence or absence of the corpus lutem (CL) in each animal. In the presence of the CL, the one-ovary and the intact animals did not differ significantly in cycle length (21.2 and 20.0 days, respectively); in the absence of the CL, the one-ovary heifers had a significantly longer cycle length (13.2 days) than the intact heifers (10.2 days). The number of follicles 5 mm or more in diameter was significantly greater in the retained ovary of the one-ovary animals than in the corresponding ovary of the intact animals; total follicular fluid, however, was practically equal in both groups. The largest follicle in the retained ovary of the one-ovary animals was smaller than the largest follicle in either ovary of the intact animals. The total follicular surface area in the retained ovary of the one-ovary animals was almost twice as large as that of the corresponding ovary of the intact animals. These results demonstrate ovarian compensatory changes (in the presence or absence of the CL) following unilateral ovariectomy in a monotocous species.