H Twagiramungu

In vitro embryo production in the cow: An effective alternative to the conventional embryo production approach

Development of new technology related to in vitro embryo production has allowed for the commercial use of this method of reproduction. In the present work, we evaluate the efficiency of this technology compared with conventional embryo production based on results obtained with a standard procedure, including the sexing of embryos. The donor animals were mature nonlactating dairy cows (n = 92) kept under a constant environment and feeding program in an ET center. Ultrasound guided transvaginal ovum pick-up following 48 h pre-treatment with FSH has been used for the IVF-IVC protocol. A total of 437 oocyte recovery sessions performed on 92 cows yielded 4145 oocytes, which were used in an IVF-IVC protocol. Using the conventional approach, 156 embryo collections on 49 cows yielded 1652 ova and embryos. All Quality 1 and 2 embryos were sexed by a PCR procedure, and embryos of the desired sex were transferred to synchronized recipients located at the center. The results obtained in the IVF protocol showed that 4 oocyte collections per cow performed within 60 d, yielded 38 oocytes, which resulted in 18.8 viable embryos, of which 7.05 were female. After transfer of the female embryos, an average of 3.8 recipients were pregnant at 60 d. One embryo collection under the conventional approach yielded an average of 1.2 female pregnancies, which was confirmed during the same 60-d time period. These results indicate that IVF procedures can effectively replace conventional embryo production methods when a predetermined number of pregnancies of known sex are needed within a short period of time.

Synchronization of estrus and fertility in beef cattle with two injections of buserelin and prostaglandin.

Postpartum beef cows and heifers in Group 1 received 8 mug of buserelin on Day 0 (the beginning of the experiment) and 500 microg of cloprostenol (PGF) on Day 6 (GnRH I, n=54). In Group 2 (GnRH II, n=54), the females were injected with buserelin on Day 0 (8 microg) and Day 3 (4 microg), and PGF on Day 6 and Day 9 for females not detected in estrus previously. Animals were bred by AI 12 hours after the onset of estrus. Blood samples were collected on Day -11 and Day 0 to assess cyclicity and on Day 3 and Days 6 to 12 to examine luteal activity. Progesterone levels did not differ between the 2 groups between Days 0 to 9. In both groups, the proportion of spontaneous estruses from Days 0 to 6 was reduced. Precision of estrus was higher (P<0.005) in the GnRH II group than in the GnRH I group of cows that were detected in estrus between Days 6 and 9. The synchronization rate, interval to estrus, pregnancy and conception rates were similar in GnRH I and GnRH II groups. The conception rate and interval to estrus were similar in cyclic and acyclic cows. Increasing the number of buserelin injections enhanced the precision of estrus, but not the conception rate, without any detrimental effect on luteal activity and induced more estruses in postpartum acyclic beef cattle.

Ovarian superstimulation after follicular wave synchronization with GnRH at two different stages of the estrous cycle in cattle.

The objective of this study was to evaluate superovulatory programs based on synchronization of follicular waves with GnRH at 2 different stages of the estrous cycle. Sixteen Holstein cows were randomly assigned to 1 of 3 groups and administered GnRH (Cystorelin, 4 ml i.m.) between Days 4 and 7 (Groups 1 and 3) or between Days 15 and 18 (Group 2) of the estrous cycle (estrus = Day 0). Four days after GnRH treatment, > or = 7-mm follicles were punctured in Groups 1 (n = 6) and 2 (n = 6) or were left intact in Group 3 (n = 4). All cows were superstimulated 2 d later (i.e., from Days 6 to 10 after GnRH treatment) with a total of 400 mg NIH-FSH (Folltropin-V) given twice daily in decreasing doses. The GnRH treatment caused a rapid disappearance of large follicles (P < 0.005), rapid decrease in estradiol concentrations (P < 0.003), and increase in the number of recruitable follicles (4 to 6 mm; P < 0.04), indicative of the emergence of a new follicular wave within 3 to 4 d of treatment. Between 4 and 6 d after GnRH treatment, the mean number of 4- to 6-mm follicles decreased (4.7 +/- 1.8 to 1.5 +/- 3.3) in the nonpunctured group but increased (3.9 +/- 1.0 to 7.3 +/- 1.9) in the punctured group of cows (P < 0.05). In response to FSH treatment, the increase in the number of > or = 7-mm follicles was delayed by approximately 2 d in the nonpunctured group (P < 0.006). Moreover, the mean number of > or = 7-mm follicles at estrus was higher (16.9 +/- 1.7 vs 11.5 +/- 3.0; P < 0.1) in the punctured than the nonpunctured group. The increase in progesterone concentration after estrus was delayed in the nonpunctured group (P < 0.1) compared with the punctured follicles. Mean numbers of CL as well as freezable (Grade 1 and 2) and transferable (Grade 1, 2 and 3) embryos were similar (P > 0.1) in punctured and nonpunctured groups. Spontaneous estrus did not occur prior to cloprostenol-induced luteolysis in any group, and stage of the estrous cycle during which GnRH was given did not affect (P > 0.1) hormonal and follicular responses in the punctured groups. In conclusion, GnRH given at different stages of the estrous cycle promotes the emergence of a follicular wave at a predictable time. Puncture of the newly formed dominant follicle increases the number of recruitable follicles (4 to 6 mm) 2 d later and, in response to superstimulation with FSH, causes a greater number and faster entry of recruitable follicles into larger classes (> or = 7 mm) and a faster postovulatory increase in progesterone concentrations.

Buserelin overcomes the effect of the corpus luteum on ovarian follicular development in postpartum cycling cows

Abstract Follicular development after treatment with a gonadotropin-releasing hormone agonist (buserelin) was compared in ovaries of postpartum cows bearing (CLO) or not bearing (NCLO) a corpus luteum (CL). In the first experiment, 16 cows on day 7 of the estrous cycle (day 0 of treatment) were treated either with saline or 8 μg of buserelin. Both ovaries were collected on day 3 or day 6 ( n = 4 per group per day) and follicles over 1.57 mm in diameter were observed histologically. Compared with day 3 in the saline group, there was a greater decrease in the percentage of Class I total (1.57–3.67 mm; P P P P P P P > 0.1) between CLO and NCLO within 3 days after treatment. In the second experiment, follicular responses in CLO and NCLO were compared by daily ultrasonography in cows that had ( n = 6) or did not have ( n = 4) a buserelin-induced ovulation. After buserelin treatment, the numbers of medium (5–10 mm) and large (over 10 mm) follicles were not different ( P > 0.1) between the CLO and the NCLO whether ovulation occurred or not. Results indicate that treatment with buserelin overcame most of the local effects of the CL on the growth and atresia of ovarian follicles in postpartum cycling cows within a 6 day period and this occurred whether ovulation was induced or not.