Superovulatory Response In Cows Research Articles

198 Superovulatory response in cows undergoing aromatase inhibitor treatment

The aromatase inhibitor letrozole has been used in the treatment of infertility in women by inducing mild ovarian superstimulation or augmenting the ovarian response to FSH treatment. The effect has been attributed to an apparent up-regulation of FSH receptors on granulosa cells as a result of increased androgens (Weil et al. 1999 J. Clin. Endocrinol. Metab. 84, 2951-2956). The objective of this study was to determine whether letrozole will augment the superstimulatory response in FSH-treated cattle. Mature, non-lactating Holstein cows (n=30) were given 2 luteolytic doses of PGF2α 12h apart and scanned daily by transrectal ultrasonography to detect ovulation. Transvaginal ultrasound-guided ablation of follicles ≥5mm was performed in all cows as a group, at 5 to 8 days after ovulation. On the day of ablation, cows were assigned randomly to 2 groups (n=15 per group) and given either an intravaginal letrozole-releasing device or a blank device for 5 days. Coinciding with expected wave emergence (Day 0), cows in both groups were given 8 doses of 50mg of pFSH (Folltropin; Vetoquinol, Lure, France) IM at 12-h intervals, and PGF2α on Days 3 and 3.5. At the time of the second PGF2α, vaginal devices were removed and paint was applied to the tailhead to facilitate detection of oestrus. On Day 5, cows were given gonadotropin-releasing hormone (100mg gonadorelin) IM and artificially inseminated 12 and 24h later. Ova/embryos were collected by transcervical uterine flush on Day 12. The ovaries were examined by ultrasonography on Day 0, 3.5, 5, 6.5, and 12 to record the follicular and luteal response. Nominal data were compared between groups by t-test and by ANOVA for repeated-measures and are expressed as mean±s.e.m. Binomial data were compared by chi-squared test. The number of follicles at wave emergence did not differ between letrozole and control groups (24.6±3.1 and 26.5±3.3 respectively; P=0.68). There was no treatment effect or treatment×day interaction in the number of follicles >8mm on Day 3.5, 5, and 6.5. Letrozole-treated cows exhibited oestrus later than controls (50.3±1.1h v. 40.7±2.0h after first PGF2α; P<0.001) and had less variance in interval to oestrus (residuals, 3.1±0.48h v. 6.7±0.87 h; P<0.01). The number of CL on Day 6.5 was lower in the letrozole group than in the control group (9.1±1.1v. 12.3±1.1; P=0.05). The proportion of ovulations (number of CL on Day 12 over number of follicles ≥3mm on Day 0) was lower in the letrozole group than in the control group (0.65±0.05v. 0.82±0.08; P=0.02). The total number of ova/embryos collected per cow did not differ between letrozole and control groups (5.0±1.9v. 5.4±1.8; P=0.75), nor did the number of transferable embryos differ (3.0±1.2v. 4.3±1.5; P=0.56). In conclusion, treatment with a letrozole-releasing device during ovarian superstimulation did not improve the superovulatory response or embryo collection rate in mature Holstein cows, but letrozole treatment resulted in more synchronous oestrus, which may be used in the design of a fixed-time AI protocol following superstimulatory treatment in cattle. This research was supported by the Alberta Livestock and Meat Agency.

Preliminary study of factors affecting the superovulatory response of high producing dairy cows superstimulated regardless of the stage of estrous cycle in Egypt

This work was conducted as a first time commercial production of embryos from lactating Holstein and Brown Swiss cows using multiple ovulation embryo transfer (MOET) technology in Egypt. We studied factors affecting the superovulatory response (SR) in superovulated cows and effects of propylene glycol (PG) on embryo quality. Daily milk production at flushing had significantly negative effects on SR and embryo yields in superovulated cows. In addition, Brown Swiss cows had better SR than Holstein cows. Moreover, cows having more than 3 parities yielded better response, compared to cows in the first three parities. However, factors such as body weight at flushing, body condition score (BCS) at flushing and days in milk (DIM) at flushing did not have any association with SR in cows. In addition, drenching of PG prior to and during the superovulatory treatment improved SR (Right CL number, P < 0.05; Left CL number, P < 0.05), total embryos per flush (P < 0.05), first grade embryos per flush (P < 0.01) and tended to improve transferable embryos (P = 0.13) and second grade embryos per flush (P = 0.11). However, it tended to increase the number of degenerated embryos per flush (0.06). In conclusion, commercial production of embryos from lactating Holstein and Brown Swiss cows regardless of stage of estrous cycle by MOET proved successful under Egyptian conditions. Milk yield was negatively associated with SR and embryo yields in superovulated cows. Moreover, drenching of PG prior to and during the superovulatory treatment improved SR and embryo yields.

293 SUBCUTANEOUS ADMINISTRATION OF FOLLICLE STIMULATING HORMONE FOR SUPEROVULATION OF HOLSTEIN COWS

Follicle stimulating hormone (FSH) is usually administered in a series of intramuscular (IM) injections to induce multiple ovulations for embryo production in cattle and other species. The objective of this study was to determine the superovulatory response of dairy cows to subcutaneous (SC) administration of FSH using a reduced number of injections in combination with a progesterone-releasing device. Eighteen non-lactating Holstein cows initially received 25 mg Prostaglandin F2α IM (PGF; Lutalyse; Pfizer Animal Health, Groton, CT, USA) on Day –7. All cows then received an intravaginal progesterone-releasing device (CIDR-B, 1.38 mg progesterone; Pfizer Animal Health) on Day 0, and 100 μg GnRH IM (Cystorelin; Merial Ltd, USA) on Day 2. Cows were randomly assigned to receive a total of 400 mg (20 mL) of FSH (Folltropin-V; Bioniche Animal Health, USA) either by IM injection (IM Group, n = 9 cows) given at 12 h intervals on Days 4 (60 mg, 60 mg), 5 (55 mg, 55 mg), 6 (45 mg, 45 mg) and 7 (40 mg, 40 mg), or by SC injection (SC Group, n = 9 cows) given at 24 h intervals on Days 4 (140 mg), 5 (140 mg) and Day 6 (120 mg). On Day 7, CIDR-B inserts were removed and cows received two 25 mg PGF IM injections given 12 h apart. Cows were artificially inseminated at 12 and 24 h after standing estrus. Blood samples were obtained from all cows at 0, 2, 4, 8, 12, 24, 36, 48, 60, 72, and 84 h after the first FSH injection for determination of serum FSH concentrations. Ovarian follicles and CL were monitored using ultrasonography on Days 4, 7, and 16. Embryos were recovered non-surgically on Day 16 (7 days after estrus). The effects of treatment on follicular response and embryo yield were analyzed by Wilcoxon test, and the response of cows to treatment was analyzed by chi-square test. The effects of treatment on concentrations of serum FSH were analyzed using ANOVA for repeated measures. There was no effect (P &gt; 0.05) of route of FSH administration on the concentrations of serum FSH at any time point. The superovulatory response of cows to treatment, defined as greater than 2 CL per cow, did not differ (P &gt; 0.05) between the IM (77.8%, 7/9 cows) and SC (88.9%, 8/9 cows) Groups. There was also no difference (P &gt; 0.05) between the IM and SC Groups for the number of 5 to 10 mm follicles prior to FSH treatment (mean ± SEM; 0.6 ± 0.2 v. 0.9 ± 0.4), the total number of follicles after FSH treatment (12.4 ± 1.6 v. 12.7 ± 2.2) or the number of CL at embryo recovery (6.4 ± 1.5 v. 10.4 ± 2.1). Similarly, there were no differences (P &gt; 0.05) between the IM and SC Groups for total number of oocytes/embryos (5.6 ± 2.6 v. 13.0 ± 4.3), transferable embryos (Grade 1, 2, 3; 3.0 ± 1.4 v. 6.1 ± 2.9) or Grade 1 embryos (2.9 ± 1.4 v. 4.3 ± 2.5). In conclusion, administration of FSH using 3 SC injections in combination with a progesterone-releasing device was an effective method for superovulation of Holstein cows. Supported by USDA Animal Health Formula Funds and the State of North Carolina.

295 SUPEROVULATORY RESPONSE IN COWS FOLLOWING SYNCHRONIZATION OF FOLLICLE WAVE EMERGENCE WITH ESTRADIOL AT DIFFERENT STAGES OF THE ESTROUS CYCLE

Ovarian asynchrony and variability in response to superstimulation remain the most limiting factors in any embryo transfer program (Armstrong D 1993 Theriogenology 39, 7–24). Ovarian response can be increased and less variable if superstimulatory treatment is started at the time of follicular wave emergence (Bö GA et al. 1995 Theriogenology 43, 31–40). A combination of progesterone (P4) and estradiol have been used to synchronize follicular wave for superstimulation. A retrospective analysis was done to compare the ovarian response, superovulatory response and embryo production of cows in Argentina that received progesterone and estradol prior to superstimulation at different stages of the estrous cycle. This research was carried out using different breed of donors (n = 584, 88% Angus) during the last 4 years in Buenos Aires province, Argentina. Heat detection was performed twice a day. At random stages of the estrous cycle, donors received an intravaginal progesterone device (DIB; Syntex, Buenos Aires, Argentina), 2 mg of estradiol benzoate and 50 mg of progesterone (Syntex, Buenos Aires, Argentina) IM on the same day. On day 4 after DIB insertion, superestimulatory treatment was initiated on a decreasing dose regimen of FSH (Pluset; Callier, Spain, or Folltropin, Bioniche Animal Health Inc., Belleville, Ontario, Canada) as IM injections every 12 h over 4 d. On day 6, DIBs were removed, and cows received two doses of 2 mL of cloprostenol 12 h apart. At heat detection, all donors received a dose of 2 mL of GnRH (Dalmarelin; Fatro Von Franken, Buenos Aires, Argentina) by IM injection and were inseminated 12 and 24 h later. Seven days later, embryo collection was performed and ovarian response was evaluated as number of CL + unovulated follicles by transrectal ultrasound using a 7.5-MHz transducer (Pie Medical, Maastricht, the Netherlands). Ova/embryos were evaluated and classified according to the IETS manual. Donors were assigned to receive DIB and estradiol during the following stages of the cycle: group 1: between days 4 and 7 post-estrus (dominant follicle period), group 2: between days 8 and 12 post-estrus (emergence of the second follicular wave), and group 3: between days 13 and 21 post-estrus (dominant follicle of the second wave). Kruskal-Wallis test was used to compare variables among groups, and results are shown in Table 1. Ovarian response as CL + unovulated follicles and number of ovulations were significantly different among groups (P &lt; 0.05). However, there was no significant difference in the number of fertilized ova or transferable embryos. Nevertheless, numeric differences that show that group 2 (started between days 8 and 12 post-estrus) was always superior for all variables. In conclusion, data suggest that estradiol may be more effective in synchronizing follicle wave emergence for superstimulation during the mid-part of the estrous cycle. Table 1. Superovulatory response in cows in which follicle wave emergence was synchronized with estradiol at different stages of the estrous cycle (mean ± SD) Research supported by Centro Genetico Bovino Eolia S.A.

Superovulatory responses in Japanese black beef cows following largest follicle aspiration or human chorionic gonadotrophin (hCG) treatment.

The effect of largest follicle aspiration or hCG administration before induction of superovulation on the ovarian response of Japanese Black beef cows was investigated using a crossover design in which induction of superovulation was attempted in every cow. The superovulatory response of cows whose largest follicle had been aspirated from the ovaries by ultrasound-guided follicular aspiration 1 day before induction of superovulation, did not differ from the response in non-treated control cows. In contrast, in cows given 5,000 IU of hCG 3 days before induction of superovulation, the proportions of fertilized ova and transferable embryos significantly decreased compared with the other groups.

Changes in morphological appearance and functional capacity of recruited follicles in cows treated with FSH in the presence or absence of a dominant follicle

This study was designed to determine the effect of the presence of a dominant follicle at the beginning of FSH stimulation on the morphological appearance and functional capacity of recruited follicles during FSH stimulation in cattle. Synchronized nonlactating dairy cows were assigned to 1 of 2 groups and treated with FSH in the presence (n = 5) or absence (n = 6) of a dominant follicle between Days 7 and 12 of the estrous cycle (Day 0 = estrus) to stimulate follicular growth. Dominant follicles were identified by daily ultrasonographic observations, beginning on Day 3 of the estrous cycle. Dominant follicle had an ultrasonographic diameter ≥ 10 mm and were in a growing phase, or maintaining a constant diameter (≥ 10 mm) for less than 4 d. Ovaries were collected at slaughter on the morning of the third day following initiation of the FSH stimulation. All follicles > 2 mm were dissected, classified according to diameter (Class 1: 2 to 4.4 mm; Class 2: 4.5 to 7.9 mm; Class 3: > 8 mm), and incubated individually for 90 min in medium M-199 (37 °C, 5% CO 2). Following incubation, integrity of each follicle was evaluated histologically to assess the level of atresia and biochemically to determine the in vitro release of estradiol (E2) and androstenedione in culture media. On Day 3 of the FSH treatment, mean number of follicles in each class was similar (P > 0.1) between the 2 groups. The percentage of atretic follicles in Classes 1 and 3 on Day 3 of the FSH stimulation did not differ (P > 0.1) between the 2 groups. However, the percentage of atretic follicles in Class 2 was higher (P < 0.005) in cows treated with FSH in presence than in absence of a dominant follicle (60.8 vs 38.2%). The release of E2 in culture media by small Class 1 atretic or healthy follicles, by Class 2 atretic and by Class 3 healthy follicles was not affected (P > 0.1) by the ovarian status. However (P < 0.001), the release of E2 in culture media of Class 2 healthy and Class 3 atretic follicles was less for follicles harvested from cows bearing than from those not bearing a dominant follicle. Within each follicular class, concentrations of androstenedione in the culture media did not differ between the 2 groups (P > 0.1). These results suggest that the presence of a dominant follicle at the beginning of FSH stimulation alters the population of follicles recruited FSH stimulation. This may be associated with the reported decrease of the superovulatory response in cows superovulated in presence of a dominant follicle.

Pre‐ovulatory Patterns of Estradiol‐17ß in Relation to the Superovulatory Response in Cows and Heifers

Pre‐ovulatory Patterns of Estradiol‐17ß in Relation to the Superovulatory Response in Cows and Heifers

Effects of follicular dominance and different gonadotropin preparations on the superovulatory response in cows

This study was conducted at Belen de Escobar, Argentina, in March and April 1987. Experimental work on synchronization of estrus, deep-freeze conservation of ram semen and small fertility trials involving cervical and intrauterine (i.u.) insemination methods was undertaken. A total of 80 Corriedale ewes were used in seven insemination trials. Insemination trials were grouped into two experimental groups for comparison of 1) frozen semen diluted with an experimental extender and a control diluent inseminated cervically or i.u. in synchronized/superovulated ewes and 2) cervical insemination of fresh diluted or frozen semen in ewes inseminated at natural estrus or in ewes that were synchronized/superovulated. An overall ovulation rate of 8.7 ± 0.5 was obtained by using a superovulatory regimen consisting of 3 mg Norgestomet implants and a total dose of 18 mg follicle stimulating hormone-pituitary (FSH-P). Numbers of ova recovered per ewe following superovulation ranged from 4.3 to 5.4. In experimental Group I, fertilization rates improved when laparoscopic intrauterine AI was used compared with cervical insemination (P<0.05). Fertility rates of i.u. and cervical insemination of frozen semen diluted with the experimental extender showed satisfactory fertilizing capacity. In experimental Group II, a lower number of fertilized ova were recovered from ewes inseminated with frozen semen (P<0.02), irrespective of their estrus manipulation.

The effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B implants

Two experiments were designed to evaluate the effect of estradiol valerate on follicular dynamics and superovulatory response in cows with Syncro-Mate-B (SMB)implants. In Experiment 1, 5 mg estradiol valerate (E 2), injected at the same time as superstimulation treatments were initiated, resulted in fewer corpora lutea (CL), ova/embryos collected and fertilized ova (P<0.05) than if E 2 was administered with the SMB implant 7 days earlier. In Experiment 2, 31 beef cows and 26 Holstein cows were placed in one of four treatment groups. Group I (control) cows were superstimulated on Day 9 (estrus=Day 0). On Day 2, cows in Groups II, III, and IV received SMB and cows in Group III received E 2. On Day 9, cows in Group IV received E 2, and all cows were superstimulated with Folltropin. The number of CL did not differ (P>0.19) among groups. However, there were more follicles < 10 mm and fewer fertilized ova and transferable embryos (P<0.02) in Group IV cows. Ovarian ultrasonography revealed that the diameter of the largest follicle in Group III cows declined from Day 2 to Day 7 and subsequently increased until Day 13. In contrast, Groups I, II and IV were characterized by apparently linear growth between Days 2 and 13. Differences (P<0.05) were detected between Days 5 and 9. Mean diameter of the largest follicle was smaller for cows in Group III than for the remaining groups on Day 9. It was concluded that SMB did not adversely affect superovulatory response and that E 2 administration resulted in atresia of the antral follicles in the cows with SMB implants.

Reproductive endocrinology of the cow: Part 2

In Part 1 the intricate hormonal relationships involved in the bovine estrous cycle were described. The widespread growth of the embryo transfer industry has made manipulation of reproductive events of both donors and recipients a commonplace practice in reproductive programs. This article presents a review of the various methods used to produce a superovulatory response in cows and the basic endocrinological changes which allow this response to occur.&#x0D; Superovulation can be defined as the increased ovulatory response induced in an individual above the normal range of ovulation rates for that individual. In cattle, therefore, three or more ovulations are considered as superovulatory responses.

Superovulatory response in cows following administration of FSH-P and prostaglandin

Superovulatory response in cows following administration of FSH-P and prostaglandin

Superovulatory response in cows following immunization against testosterone and treatment with bovine follicular fluid and PMSG

Superovulatory response in cows following immunization against testosterone and treatment with bovine follicular fluid and PMSG