Superovulation in cattle: A combined treatment using syncromate B with either pregnant mare serum gonadotrophin or follicle stimulating hormone

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 all 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.

Number and viability of embryos collected in vivo or from the excised uteri of slaughtered donor cows

Embryos were collected from superovulated donor cows on Day 7 of the cycle either in vivo by a standard nonsurgical method (A) or in vitro from the excised uterus after slaughter of the donor cow (B). In Method B, the time between slaughter and flushing of the uterus ranged from 0.5 to 4 hours. Flush yield was 5.6 +/- 5.0 and 8.4 +/- 5.3 embryos (P<0.01); the recovery rate was 0.6 +/- 0.4 and 0.8 +/- 0.3 (P<0.05) for Methods A and B, respectively. Method B resulted in more Grade 3 (P<0.001) and 4 embryos, while Method A resulted in more Grade 1 and 2 embryos. The correlation between the percentage of Grade 1 and 2 embryos and the time interval between slaughter of the donor cow and flushing the excised uterus was -0.42 for in vitro flushes. Viability of fresh and frozen-thawed embryos, as determined by in vitro culture of Grade 1 and 2 morulae and early blastocysts, was considerably lower for Method B than Method A. The percentage of embryos developing into expanded blastocysts was 100% (10 10 ) and 40% (4 10 ) for fresh embryos (P<0.01) and 52.7% (29 55 ) and 0% (0 25 ) for the frozen-thawed embryos (P<0.001) for Methods A and B, respectively. This reduction in viability might be the result of a postmortem pH decrease in the uterine fluids within the first 30 minutes from 7.0 to 5.8 and 6.0. Flushing of the uterus directly after slaughter (within 5 to 10 minutes) may prevent the possible detrimental effect of a low pH on the embryos.

Pharmacologic manipulation of fertility

The professional application of agents to the manipulation of fertility of cows requires basic and applied knowledge of the physiologic mechanisms that are affected and of the pharmacologic agents that are used. In all areas of the pharmacologic manipulation of fertility, the achievement is less than the ideal, and further research is required to improve the efficiency of treatments. The induction of estrus in acyclic animals can involve a reduction in the depth of anestrus, pretreatment with progestagen to ensure estrous behavior and the formation of a normal corpus luteum, and then treatment with exogenous gonadotropin. Responsiveness to treatment can be variable and reflects the depth of anestrus of the animals. Improved treatment regimens require a knowledge of the basic mechanisms involved with the depth of anestrus, a means of assessing the depth of anestrus, and an understanding of the hormonal requirements of ovarian follicles for development and maturation in animals at different depths of anestrus. The optimal precision in the synchronization of estrus (and ovulation) in cyclic animals requires the synchronization of both follicular waves and the end of progestational phase. The end of progestational phase can be synchronized effectively using prostaglandin F2a (or analogs), or by treatment with progestagens with or without luteolytic agents. Procedures to synchronize follicular waves need to be established. The induction of superovulation can be achieved readily using gonadotropins prior to estrus synchronization using prostaglandin F2a. The responses to standard treatments in terms of ovulation rates and yield of transferable embryos are highly variable. The development of procedures to reduce this variability requires an understanding of the intra-ovarian mechanisms involved in recruitment of follicles for a wave of follicular growth, in the selection of dominant follicles for further development, and in the mechanisms controlling follicular atresia. Cystic ovarian disease can be treated effectively using HCG or GnRH (follicular cysts) or prostaglandin F2a (luteal cysts). The basic mechanisms resulting in failure of estrogen positive feedback on LH secretion (that results in cystic follicles) remain to be determined. Small but significant increases in pregnancy rates can be achieved treating cows with prostaglandin during the post-partum period, with prostaglandin to induce estrus for insemination, with GnRH or HCG at estrus, and with GnRH or progestagen treatment during diestrus. Beneficial effects of treatment have been shown in some trials but not in others.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of single deep insemination on transferable embryo recovery rates in superovulated dairy cows

Thirty superovulated Friesian lactating cows were randomly assigned to two groups. Group I donors were inseminated with one unit of semen deposited into the uterine body at 8, 20 and 32 h after the onset of estrus. Group II donors were inseminated with one unit of semen deposited deep into the uterine horns at 15 h after the onset of estrus. Neither the mean rates of fertilized ova nor the mean rates of transferable embryos were different between treatments (P > 0.05).