Timed artificial insemination of two consecutive services in dairy cows using prostaglandin F2alpha and gonadotropin-releasing hormone

Ovarian cysts, an anovulatory condition in dairy cattle

Ovarian cysts are one of the most common ovarian dysfunctions in dairy cattle, which can lead to a considerable economic loss through its high incidence and can reduce the reproductive performance. Anestrus is the most significant clinical sign observed in dairy cattle suffering from this condition. For diagnosis, most of the veterinarians use a combination of methods, from ultrasonography as an additional approach to trans-rectal palpation and symptomatology when assessing ovarian cysts. Although the Ovsynch treatment seems to be preferred, the pregnancy rate after this treatment is relatively low. Despite such reports on dairy cattle ovarian cysts, the data is insufficient to validate all the characteristics of this condition. This review summarizes what the literature has so far provided from definition to treatment of ovarian cysts in dairy cattle.

Ovarian follicular response to oestrous synchronisation and induction of ovulation in Norwegian Red cattle

BACKGROUND

Oestrous synchronisation of cattle has been widely applied to accomplish simultaneous ovulation in animals and facilitate timed artificial insemination. The main aim of this study was to investigate the ovarian follicular growth and ovulatory response to oestrus and ovulation synchronisation in Norwegian Red heifers and cows. Oestrous cycles in 34 heifers and 10 cows from 4 herds were synchronised with two PGF_2α analogue treatments 11 days apart, followed by GnRH analogue treatment for induction of ovulation. Thereafter, the ovaries were examined by ultrasonography at 3 h intervals until ovulation.

RESULTS

The luteolytic effect of the PGF_2α analogue was verified in 9 of 10 cows by progesterone contents in milk. Maximum physical activity of the cows occurred on average 69 h after PGF_2α analogue treatment. An ovulatory response was recorded in 95.5% (42/44) of the animals. A significant difference in follicle size at ovulation was found between 2 of the herds. Animals with medium sized and large follicles and heifers aged > 16 months ovulated earlier than other animals.

CONCLUSIONS

The applied sequence of treatments in the study was shown to be effective in synchronizing and inducing ovulation within a relatively narrow time interval in the Norwegian Red heifers and cows, consistent with findings in other cattle breeds.

The effect of presynchronization with prostaglandin F2α and gonadotropin-releasing hormone simultaneously, 7 d before Ovsynch, compared with Presynch-10/Ovsynch on luteal function and first-service pregnancies per artificial insemination

Pregnancy per artificial insemination (P/AI) following Ovsynch is optimized when cows ovulate to the first GnRH of Ovsynch. Fertility programs are designed to presynchronize cows to d 6 or 7 of the estrous cycle to increase the chances of ovulation of a first-wave dominant follicle to the first GnRH of Ovsynch. The hypothesis of this experiment was that simplification of a presynchronization program through the combination of PGF_2α and GnRH on the same day, 7 d before Ovsynch, would allow for similar P/AI compared with Presynch-10. Lactating dairy cows (n = 432) 41 to 47 d in milk (DIM) were randomly assigned to 2 treatments within parities for first service. Control cows received Presynch-10/Ovsynch consisting of the following: PGF_2α-14 d-PGF_2α-10 d-GnRH-7 d-PGF_2α-56 h-GnRH-16 h-AI. Treated cows received PGF_2α and GnRH-7 d-GnRH-7 d-PGF_2α-56 h-GnRH-16 h-AI. All cows received a supplemental injection of PGF_2α 24 h after the PGF_2α of Ovsynch to enhance complete luteolysis. All cows received timed AI between 75 and 81 DIM. Blood was collected to assess circulating concentrations of progesterone (P4), and the number and size of corpora lutea (CL) were recorded using ultrasonography on day of PGF_2α of Ovsynch. The administration of PGF_2α simultaneously with GnRH and 7 d before Ovsynch (PG+G) had similar P/AI at 28 (46 vs. 48%), 35 (43 vs. 43%), 49 (39 vs. 39%), and 77 d post-AI (38 vs. 39%) compared with Presynch-10. No differences were observed in P/AI in primiparous versus multiparous cows at 28 (52 vs. 45%), 35 (48 vs. 41%), 49 (45 vs. 37%), and 77 d post-AI (43 vs. 36%). No difference existed between treatments in percentage of cows with functional CL at PGF_2α of Ovsynch, total luteal area (mm²), or serum concentrations of P4 at time of PGF_2α of Ovsynch, regardless of parity. Number of CL had a tendency to be greater for multiparous PG+G vs. Presynch-10 cows (2.34 ± 0.09 vs. 2.15 ± 0.08) but not in primiparous cows (1.95 ± 0.10 vs. 1.98 ± 0.11). In summary, administering both PGF_2α and GnRH on the same day, 7 d before the start of Ovsynch, appears to be a simple and effective alternative to Presynch-10 Ovsynch.

Incorporation of a rapid pregnancy-associated glycoprotein ELISA into a CIDR-Ovsynch resynchronization program for a 28 day re-insemination interval

The objective was to compare two resynchronization programs; one that used a blood-based ELISA for pregnancy-associated glycoproteins (PAG) for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 28 d after first TAI, and another that used transrectal ultrasonography for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 35 d after first TAI. The PAG_resynch cows (n = 103) began CIDR-Ovsynch resynchronization on Day 18 after first TAI (Day 0). On Day 25, the CIDR was removed and pregnancy diagnosis with a PAG ELISA was performed. If a cow was not pregnant on Day 25, she was treated with PGF(2α), treated with GnRH 2 d later (Day 27), and TAI on Day 28. Control cows (n = 99) were observed for estrus until Day 25, when they began an identical CIDR-Ovsynch program with pregnancy diagnosis by transrectal ultrasonography on Day 32. If a cow was not pregnant on Day 32, then she was treated with PGF(2α), treated with GnRH 2 d later (Day 34), and TAI on Day 35. There was no difference in pregnancy per AI (P/AI) for either group at first or second insemination. For cows without pregnancy loss, the interval between first and second (P < 0.001) or second and third (P < 0.016) TAI was shorter for PAG_resynch cows compared with Control cows. The interval between first and second or second and third TAI was not different if pregnancy loss cows were included in the analysis. Plasma progesterone concentrations were similar at PGF(2α) treatment, and plasma estradiol concentrations increased similarly after PGF(2α) treatment for PAG_resynch and Control cows. In conclusion, the 28 d CIDR-Ovsynch resynchronization protocol was comparable to a 35 d CIDR-Ovsynch resynchronization protocol that also included estrus detection. Shortened resynchronization protocols that do not require estrus detection may improve reproductive efficiency in dairy cattle.

Efficacy of a treatment with hCG 4 days after AI to reduce pregnancy losses in lactating dairy cows after synchronized ovulation

Content The objective of the study was to investigate whether a treatment with hCG 4 days after AI could reduce pregnancy losses in lactating dairy cows. Cows of a dairy herd presented to the veterinarian in a fixed reproductive management protocol were treated with an Ovsynch protocol if no corpus luteum (CL) could be palpated per rectum (Group OV). Cows with a CL received cloprostenol (0.15 mg). After 2 days, these cows were treated with buserelin (0.01 mg) and received timed AI 16-20 h later (Group PG). In both treatment protocols, cows were assigned to two groups to receive 2500 IU of hCG i.v. 4 days after AI or to serve as untreated controls (Groups OV-hCG, OV-Control, PG-hCG and PG-Control). Pregnancy diagnosis was carried out 27 days after AI via ultrasonography and 39 days after AI by rectal palpation. Pregnancy losses were defined as cows being pregnant on day 27 but not pregnant on day 39 after AI. Pregnancy rate (PR) by day 27 did not differ among the four groups (35.4, 35.0, 37.0 and 38.0% for Groups OV-hCG, OV-Control, PG-hCG and PG-Control, respectively). Pregnancy losses between day 27 and day 39 after AI were smaller in hCG treated animals in summer but not in autumn and spring. Pregnancy rate by day 39 after AI was higher in PG than in OV groups, but independent of hCG-treatment. In conclusion, treatment with hCG 4 days after AI did not significantly increase PR on 39 days after AI. A positive effect of hCG on pregnancy losses during the summer months warrants further investigation.