J. Robalo Silva

Plasma progesterone profiles and factors affecting embryo-fetal mortality following embryo transfer in dairy cattle

Abstract The relationship between plasma progesterone (P4) levels and embryo survival, and the value of P4 profiles for the selection of cattle embryo transfer recipients is still a matter of controversy. This study reports a comparison between lactating cows and heifers (n=407) from a single dairy herd, after transfer of either fresh or frozen-thawed good quality embryos, of their ability to sustain embryo-fetal development to term. Plasma P4 concentrations on the day of estrus (Day 0=D0), Day 4, Day 7 and on Day 21 were measured and related to embryo survival. Plasma P4 levels on Days 0, 4 and 7 were similar in recipients later found pregnant or open. Plasma P4 levels on Day 7 were significantly higher (P

Embryo yield and plasma progesterone profiles in superovulated dairy cows and heifers.

This study was conducted to compare the superovulatory (SOV) response of dairy cows (n=172) and heifers (n=172), with two SOV treatments started at the mid-luteal-phase of the estrus cycle. Donors were randomly treated either with equine chorionic gonadotrophin (eCG) plus neutra-eCG serum (eCG+N group, n=167) or follicle stimulating gonadotrophin (FSH-P group, n=177). No significant differences were observed among groups in the percentage of superovulatory responsive donors (SR donors; corpora lutea (CL) ≥2), the mean number of total ova, fertilized ova and viable embryos recovered. Cows yielded significantly less total ova and less fertilized ova (P<0.05) and tended to yield less viable embryos (P<0.06) than heifers. Plasma progesterone (P4) concentrations (n=135 donors) on the day of PGF2α (PGF) injection and on the day of SOV estrus were significantly higher (P<0.01) in eCG+N than in FSH-P donors and, the increase between those 2 days was also significantly higher (P<0.05) in group eCG+N than in group FSH-P, suggesting a higher luteotrophic effect of eCG than FSH-P. SR donors had P4 levels significantly higher (P<0.001) than non-SR donors only on day 5 after the SOV estrus and on the day of embryo recovery. Plasma P4 concentrations at 5 days after the SOV estrus and at embryo recovery correlated significantly (r=0.76, P<0.001). Heifers had significantly higher P4 levels than cows at gonadotrophin injection (P<0.01), PGF injection (P<0.001), 5 days (P<0.01) and 7 days (P<0.001) after the SOV estrus. At day 7 after the SOV estrus, P4 concentrations per ova recovered were significantly higher in heifers than in cows (P<0.01). The increase of plasma P4 per ova recovered, between days 5 and 7 after the SOV estrus, was significantly (P<0.01) higher in heifers than in cows. Also, the increase of plasma P4 between injections of gonadotrophin and PGF was significantly higher (P<0.05) in heifers than in cows. These results suggest that heifers have higher plasma P4 concentrations at diestrus (either before or after the SOV treatment) and this is associated with a higher embryo yield and quality, as compared to lactating cows. These higher plasma P4 concentrations reflect not only differences in ovulation rate as well as the competence of the corpus luteum, which is potentialized by gonadotrophin stimulation.

Superovulatory response, embryo quality and fertility after treatment with different gonadotrophins in native cattle.

We studied native Mertolengo cattle to evaluate superovulatory (SOV) treatments, subsequent fertility of donors and pregnancy rate of recovered embryos. In Experiment 1 we compared superovulatory response (SR), embryo quality and plasma progesterone (P4) levels between donors treated with eCG (10 cows and 5 heifers) vs. FSH (pure, FSH-1, n= 10 cows and crude, FSH-2, n= 10 cows), during progestagenic impregnation. We also compared fertilization rates and embryo quality of bred and inseminated eCG and FSH-1 donors. Significantly more viable embryos were yielded by FSH than by eCG treated donors. Less FSH-1 than FSH-2-treated donors showed SR, but the response was identical in responder donors of both groups. Fertilization rates were significantly higher in bred than in inseminated donors. Plasma P4 levels were only significantly different (higher) between responder and non-responder donors on the day of embryo recovery. Experiment 2 compared FSH treatments (FSH-2, crude, n= 11 cows and FSH-3, pure, n= 10 cows) started at the midluteal phase. The mean number of viable embryos was significantly higher in FSH-3 than in FSH-2 treated donors. Both FSH treatments exerted a similar luteotrophic effect upon injection. The FSH-2 donors treated during the midluteal phase yielded more ova and showed significantly higher plasma P4 levels at a.ll sampling days than those treated during progestagenic impregnation. The pregnancy rates of recipient cows were 67% and 46% for fresh and frozen-thawed embryos respectively. In Experiment 3, the fertility of donors (n= 20) after SOV treatments was compared with that of untreated cows (n= 40). Time to conception of donors, after mating with a bull 14 days after embryo recovery, was identical to that of control cows. There was some delay to conception in eCG-treated cows, but the difference was not significant. These preliminary results suggest that response to SOV treatments in Mertolengo cattle might be affected by the type of gonadotrophin and by the treatment protocol. The fertility of a traditional breeding season after SOV treatments was not impaired. Cryopreserved embryo banking can be used to preserve the breed. 0 2001 by Elswier Science Inc.

Plasma progesterone profiles, ovulation rate, donor embryo yield and recipient embryo survival in native Saloia sheep in the fall and spring breeding seasons.

The response to superovulatory (SOV) and estrus synchronization (ES) treatments and the fertility of donor (n=68) and recipient (n=118) Saloia ewes was evaluated in the fall and spring breeding seasons. The proportion of acyclic ewes at treatment time was significantly higher in the spring than in the fall (42.6% versus 4.0%, P<0.00001). Donors treated with eCG had a significantly higher mean number of follicles over 5mm in diameter in the ovaries at embryo recovery and a significantly lower mean efficiency of recovery than FSH-treated ewes. These negative effects were more pronounced in the fall than in the spring, which resulted in a significantly lower mean number of total and fertilized ova recovered from eCG-treated ewes, compared to FSH donors in the fall, but not in the spring. Season had no significant effect on the ovulation rate and plasma P4 concentrations of recipients treated with a progestagen plus eCG combination. Although the recipient lambing and embryo survival rates were higher in the fall than in the spring the differences were not significant. No significant differences were observed in the ovulation rate or P4 concentrations of recipients that lambed compared to those that did not lamb. These preliminary results show that, in Portugal, response of Saloia ewes to SOV or ES treatments and donor fertility following the SOV treatment were similar in the spring and the fall, which suggests that in the spring acyclic ewes are in moderate anestrus. The effect of season on fertility following embryo transfer should be confirmed in further studies involving a larger number of animals. The semilaparoscopic transfer method reported here allowed lambing and embryo survival rates higher (although not significantly) than a standard surgical approach.

Cyclic reproductive activity and efficiency of reproduction in Serrana goats

Reproductive efficiency was studied in mature Serrana goats in three commercial units with ovarian activity being assessed from plasma progesterone profiles between October and May. Over a 2 year period, the mean fertility was 76.2% and the prolificacy was 1.73. Parturitions were recorded between 1 October and 28 February, with 50% of them occurring before the end of October. Goats kidding in October had a significantly shorter (P<0.01) postpartum anoestrous period in the first year (33.0±9.4 days; n = 20) than in the second year of this experiment (50.3±19.7 days; n = 20). Ovarian activity, assessed by plasma progesterone profiles, was low in October (postpartum anoestrus), increased until early January, then declined suddenly to less than 3% and remained low until the first week of May (seasonal anoestrus) when the breeding period commenced. The data suggest that Serrana goats have a period of anoestrus from January to May. Fertility in the beginning of the breeding period (May) could be improved by adequate management techniques so that most parturitions occur in October/November.

The effect of experimentally induced hypocalcaemia on uterine activity at parturition in the ewe

The effect of hypocalcaemia experimentally induced by the intravenous infusion of ethylene-diamine tetraacetic acid, disodium salt (Na(2)EDTA) upon myometrial activity at parturition was studied in eleven ewes. Infusions of Na(2)EDTA were performed during first stage of labour (three animals), second stage (four animals), third stage (three animals) and postpartum (two animals); one in the latter group had been previously treated during second and third stages. Uterine activity was recorded using balloon-tipped catheters surgically implanted into the uterus and was expressed in Montevideo Units (M.U.). Plasma calcium (nonchelated) concentrations were monitored throughout the infusion. Induced hypocalcaemia resulted in a reduction of the activity of the uterus when Na(2)EDTA was administered during the first stage of labour. In the ewes infused during the second stage of labour, there was difficulty in reducing the activity of the uterus and, consequently, in delaying parturition. Reduction in uterine activity was easier in the ewes infused during the third stage of labour and during postpartum. Uterine activity started decreasing when plasma calcium concentrations were 6.6 and 7.1 mg/100 ml in the ewes infused during third stage of labour and postpartum, respectively, compared with 4.9 mg/100 ml in those infused during first stage of labour; the difference between this last group and the first two was significant (p < 0.05). After the end of the infusion, the plasma calcium started rising and normal uterine activity quickly resumed.

The effect of experimental induced hypocalcaemia on uterine activity in the sow during parturition and post-partum

Uterine activity was measured by monitoring intrauterine pressure changes using ballon-tipped catheters placed in the lumen. An infusion rate of Na(2)EDTA of 35 mg/Kg/h gave a chelation rate equivalent to the rate of calcium mobilisation, and when infused at a level greater than this, resulted in a reduction in plasma calcium concentrations and a concomitant reduction in uterine activity. In three of the four sows infused intrapartum, there was complete cessation of uterine activity; however, plasma calcium concentrations of less than 6 mg 100 ml resulted in a reduction in uterine activity at this stage of parturition. The uterus of the sow post-partum appeared to be more sensitive to the effects of hypocalcaemia with reduced uterine activity when plasma calcium concentrations fell below 8.2 mg 100 ml and complete cessation of activity between 6 and 7 mg 100 ml . Although there was evidence of a delay in the expulsion of piglets in the hypocalcaemic sows, there was no evidence of an increased number of stillborn piglets compared with the two control sows.

Seasonal variation in the ovarian activity of beef cows assessed by monitoring progesterone concentrations

Ovarian activity was assessed for over a year in 16 beef cows, 10 of the Alentejano and 6 of the Mirandes breed, by measuring plasma progesterone twice weekly. It was observed that there were acyclic cows from January to the end of May and from the end of August to the end of September. The greatest number of acyclic cows (3 out of 16) was observed in April. Progesterone determinations showed that after the period of acyclia there was a small short-lasting increase in progesterone, then a cycle with a short dioestrus followed by cycles of normal duration. Oestrous cycles were on average 23.16 ± 0.16 days long; the difference between breeds was not significant. The duration of cycles throughout the year was statistically different (P < 0.01) between months. Minimum and maximum values were observed in March (21.5 ± 0.6 days) and December (25.05 = 0.58 days) respectively.

Spontaneous uterine activity and plasma progesterone and oestrogens in the ewe with live and stillborn lambs

Peripheral plasma progesterone and oestrogen concentrations were measured during late pregnancy and the parturient period in 12 ewes producing live lambs and three others producing stillborn lambs. Progesterone values started declining by 10 days before lambing but at minus 24 hours were still 6.1 +/- 3 ng/ml in the ewes bearing live lambs; during the last 24 hours progesterone was significantly lower in the ewes producing stillborn lambs. Oestrogens reached a maximum level of 550 +/- 280 pg/ml at the time of delivery and declined rapidly to basal values shortly after lambing. Oestrogens did not rise at lambing in the ewes producing stillborn lambs. In seven of the 12 ewes bearing live lambs, uterine activity, as determined by intrauterine pressure changes, was recorded throughout parturition and compared with the plasma values for progesterone and oestrogens. It was found that there was a highly significant positive correlation between uterine activity and plasma oestrogen concentrations, and a highly significant negative correlation between uterine activty and both plasma progesterone concentrations and the progesterone: oestrogen ratio.