Superovulatory responses of cattle

Interrelationships of hormonal and ovarian responses in superovulated heifers pretreated with FSH-P at the beginning of the estrous cycle

The objective of this study was to determine the relationships between follicle stimulating hormone, (FSH), estradiol (E(2)), and progesterone (P(4)) concentrations in peripheral blood samples and the follicular dynamics prior to and during superovulation in heifers pretreated with FSH-P (10 mg, i.m.) (FSH-P-primed; n=9) or not (saline-primed; n=9) on Day 3 (Day 0 = estrus) of the estrous cycle. On Day 10, all heifers were superovulated with FSH-P (27.7 mg i.m.) in declining dosages over 5 days. Prior to and during superovulation, blood samples were collected one to five times daily, and the follicular dynamics were monitored daily by ultrasonography. Prior to superovulation, profiles of P(4) and E(2) did not differ (P>1) between the saline- and FSH-P-primed heifers. The FSH concentrations in saline-primed heifers decreased from 0.43 +/- 0.05 ng/ml to 0.30 +/- 0.04 ng/ml between Days 3 and 7 and then increased progressively to 0.59 +/- 0.04 ng/ml on Day 10. In contrast (P<0.002), FSH concentrations in the FSH-P-primed heifers remained constant between Days 3 and 10 and averaged 0.41 +/- 0.03 ng/ml. Higher increases in E(2) during superovulation (maximum values, 100 vs 46 pg/ml) and in P(4) after superovulation (maximum values, 39 vs 22 ng/ml) in the saline-than in the FSH-P-primed heifers reflected the greater increase in the number of follicles (>10 mm) and in the number of corpora lutea (CL) in the saline-primed heifers. Prior to the preovulatory luteinizing hormone (LH) peak during superovulation, there was a parallel (P>0.1) decrease in FSH concentrations in the saline- and FSH-P-primed groups. Within heifers partial correlations indicated that E(2) was correlated positively with the number of follicles (>/= 7 mm) and the size of the largest follicle during superovulation (r=0.54 to 0.81; P<0.01). Negative correlations were detected (P<0.01) between FSH and the number of follicles >/=7 mm prior to (r=-0.26) and during superovulation (r=-0.37). The results cofirm earlier reports indicating that priming with FSH-P decreases the superovulatory response in cattle. Interrelationships of hormonal and ovarian responses support the concept that the presence of large dominant follicles prior to superovulation limits the superovulatory response.

Fine structure of corpora lutea in superovulated heifers

The aim of the present study was to determine the degree of development and structural status of perfusion-fixed day-7 corpora lutea (CL) (using qualitative and quantitative histology at light and electron microscopy levels) in FSH-induced superovulated (SO) and untreated heifers. Blood samples were collected daily to monitor the plasma progesterone levels during the FSH treatment up to slaughter 7 days after oestrus. Meanwhile the ovarian activity was followed by ultrasonography and rectal palpation. At slaughter, the ovaries were fixed by vascular perfusion to avoid distortion of the structures and conventionally processed for electron microscopy. The volume density of the luteal tissue was calculated on the examined sections by point-counting. The histology of the corpora lutea, exception made of a higher incidence of degenerated luteal and endothelial cells in the superovulated animals, did not differ from that of the untreated animals, confirming their normal development. The mean weight and volume of the CL in SO animals was 50% smaller than that of the untreated heifers. The progesterone concentration (nmol/l) at day 7 was significantly positively correlated with the number of CLs/heifer (r = 0.93, P less than 0.01), with the weight of Cls/heifer (r = 0.97, P less than 0.005) and with the volume of CLs/heifer (r = 0.97, P less than 0.005). The results indicated that there were no morphological differences, in terms of histological structure and volume density, between the luteal tissue of SO heifers and the luteal tissue of non-SO heifers on day 7 of the oestrous cycle which could interfere with its endocrine function.

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)

The effects of FSH-priming and dominant follicular regression on the superovulatory response of cattle

Thirty superovulatory treatments were administered to 19 mixed-breed, nonlactating cows. In 10 superovulatory treatments, the cows were primed with follicle stimulating hormone (FSH) on the second and third day of the estrous cycle, and in another 10 superovulatory treatments, the cows received no priming dosage of FSH. Initiation of the superovulatory treatments in both groups was determined by ultrasonically monitoring for regression of the dominant anovulatory follicle. Still another 10 superovulatory treatments were begun on Day 10 without regard for regression of the dominant anovulatory follicle and without a priming dosage of FSH. The mean days for starting the superovulatory treatment in the FSH-primed cows, in the nonprimed cows and in the controls were 10.5, 11.9 and 10 days, respectively. All cows were treated with eight injections of FSH at 12-hour intervals in a declining dosage (36 mg total). Cows were bred naturally and embryos collected nonsurgically seven days later. There was no significant difference (P>0.05) between the total number of embryos or transferable embryos in the three treatment groups. In this study neither priming on Days 2 or 3 nor initiating the superovulatory treatment, based on the morphologic regression of the dominant anovulatory follicle, was an effective means for improving the superovulatory response in cattle.

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.

The effect of co-treatment with recombinant bovine somatotrophin on plasma progesterone concentration and number of embryos collected from superovulated Holstein heifers

Mature Holstein heifers were induced to superovulate with twice-daily injections of porcine follicle-stimulating hormone (FSH), and were given either 20 mg i.m. of recombinant bovine somatotrophin (rBST) or saline with each FSH injection. The animals were artificially inseminated and the embryos were collected nonsurgically at Day 7. There was no significant difference in the mean (+/-S.D) total number of embryos collected from rBST-treated animals (8.3+/-5.3) when compared with that of the controls (7.2+/-6.6), or in the mean number of transferable embryos (5.3+/-4.0 vs 5.2+/-4.5). However, co-treatment with rBST tended to increase the ovulatory response, and it significantly increased plasma progesterone concentrations at Day 6 (P = 0.04). Based on these latter observations, we conclude that treatment with rBST enhanced the superovulatory response in heifers.

Dynamics of ovarian follicular development in cattle during the estrous cycle, early pregnancy and in response to PMSG

Ovarian follicular dynamics of cattle were examined during the estrous cycle, early pregnancy and in response to PMSG. Number and size of follicles were monitored by ultrasonographic examinations. During the estrous cycle, distinct periods of follicular dominance (measured by the increase in difference in size between the largest and second largest follicle) occurred in both the luteal (Days 6-8) and proestrus (18-22) phases of the estrous cycle (two follicular waves). Associated with the well timed development of the first dominant follicle was a change in distribution of follicle numbers in small (less than 5 mm; increased on Days 2-4), medium (6-8 mm; increased on Days 3-5) and large (greater than or equal to 9 mm; increased on Days 6-9) follicular size classes. Follicular development was greater on the ovary bearing the CL for the period that the CL was present. The dominant follicle formed during the first follicular wave was capable of ovulating (6 of 8 heifers) following an injection of a synthetic analogue of prostaglandin F-2 alpha on Day 9 of the estrous cycle. During early pregnancy (Days 6-34), follicular development (size of largest follicle, number of follicles and total accumulated size of all follicles) on the ovary bearing the CL was suppressed between Days 24 and 34 of pregnancy. This was a local effect in that follicular development was sustained on the contralateral ovary. Therefore, the CL or conceptus may be regulating follicular development in a manner to help prevent luteolysis. Associated with the injection of PMSG was an initial increase in the number of small follicles followed by their recruitment into medium and large size classes leading to ovulation. Number of follicles greater than 5 mm on the Day of estrus was related (r = .97) to the number of subsequent embryos and oocytes collected. Ultrasonography is a valuable technique to monitor ovarian follicular dynamics in cattle, and can thereby be used to infer changes in physiological and endocrine states.

Pattern of sex steroids secretion and their relationship with embryo yield in Jersey cows superovulated with PMSG

The levels of progesterone and estrogen secretion were studied in relationship to the superovulatory response in Jersey cows. Progesterone and estrogen concentrations were measured in superovulated Jersey cows with the objective of correlating the patterns of steroid secretion with embryo yield and quality. Pregnant mare serum gonadotropin (PMSG) was used in combination with prostaglandin F(2) alpha analogue to induce superovulation in 18 multiparous, cyclic cows. Serum progesterone and estradiol levels from cows which exhibited estrus within 24 to 48 h after prostaglandin administration (n=13) were used to estimate the superovulatory response. Sex steroid concentrations at the day of estrus (Day 0) was a strong indicator of embryo yield. Progesterone was negatively (r=-0.56) and estrogen positively (r=0.80) correlated to the number of embryos collected. Dramatic increase in progesterone from Day 0 to Day 7 was a significant indicator of embryo yield. A higher rise of estrogen in the follicular phase was an indicator of a larger number of growing follicles and, consequently, better superovulatory response. Nonresponding animals did not show any significant change in the hormonal profile from the day of PMSG treatment to the day of embryo collection. The estimation of progesterone and estradiol concentrations, simultaneously, gave a more objective prediction of embryo yield.

Superovulation in heifers given FSH initiated either at day 2 or day 10 of the estrous cycle

The aim of this study was to determine if initiation of superovulation in heifers during the time of development of the first dominant follicle (Days 2 to 6) would give equivalent ovulation and embryo production rates as treatment initiated at mid-cycle. Estrus was synchronized in 60 beef heifers using luprostiol (PG) and they were randomly allocated to treatment with 4.5, 3.5, 2.5 and 1.5 mg of porcine follicle stimulating hormone (FSH) administered twice daily, either on Days 2, 4, 5 and 6 (Day-2 group), respectively, or with similar doses at four consecutive days during mid-cycle (Day-10 group, initiation on Day 9 to 11). All heifers received 500 mug cloprostenol at the fifth FSH injection and 250 mug at the sixth injection. Blood samples for progesterone determination were collected at the time of FSH injections. Heifers were slaughtered 7 d post estrus, and the number of ovulations and large follicles (>/=10mm) were determined on visual inspection of the ovary. Following flushing of the uterine horns the quality of embryos and the fertilization rate were determined. Significant differences between treatments were determined using a two-sided t-test, and frequency distributions were compared using Chi-square tests. The mean number (+/-SEM) of ovulations for heifers in the Day-10 group was 12.9+/-1.0, and 8.5+/-0.9 embryos were recovered. Both the number of ovulations (6.7+/-0.8) and embryos recovered (4.1+/-0.6) were lower (P=0.0001) in heifers in the Day-2 group. Following grading based on a morphological basis, a higher number (P=0.002) of embryos was categorized as Grades 1 and 2 (4.1+/-0.6) and Grade 3 (2.1+/-0.4) in Day-10 heifers than in the Day-2 group (Grade 1 and 2, 1.9+/-0.3; Grade 3, 0.7+/-0.2). The number of Grade 4 and 5 embryos (Day 10, 1.6+/-0.2; Day 2, 1.4+/-0.2) and the number of unfertilized ova (Day 10, 0.7+/-0.4; Day 2, 0.2+/-0.1) did not differ between treatments. Progesterone concentrations were lower (P=0.0001) in Day-2 heifers at FSH treatment prior to prostaglandin, and the decline was more rapid following prostaglandin injection at Day 5 (P=0.02). Results of this study indicate that the number of ovulations and embryos recovered was lower in heifers when FSH treatment was initiated on Day 2 compared with Day 10 of the estrous cycle.

Rapid milk progesterone assay as a tool for the selection of potential donor cows prior to superovulation

This study investigated the accuracy of a commercially available rapid milk progesterone (P(4)) assay (RMPA) and its usefulness for the screening of potential donor cows prior to superovulatory treatment. Superovulation was induced in 90 lactating Holstein-Friesian crossbred dairy cows with twice daily injections over a 4-day period for a total of 40 mg follicle stimulating hormone (FSH-P), starting 9 to 13 d post estrus. Prior to induction of superovulation, a milk sample was collected and assayed for a P(4) level using the RMPA. The test determines P(4) by a simple visual color inspection of the respective sample, which is compared to a standard containing 10.5 ng/ml of P(4). All animals were divided into six groups according to the color intensity of their sample; three groups had a lower level, one group had an equal level and two groups had a higher P(4) level than the standard. Results of the semiquantitative RMPA were verified by a quantitative enzymeimmunoassay (EIA). Samples evaluated as equivalent to the standard had a mean P(4) level of 10.7 +/- 1.3 ng/ml (x +/- SEM). In total, P(4) levels differed (P<0.05) among groups, except in those with lower P(4) concentrations (1.1 +/- 0.0; 1.0 +/- 0.0; 3.7 +/- 1.5; 10.7 +/- 1.3; 13.8 +/- 1.3; 19.0 +/- 1.5 ng/ml, respectively). The correlation between RMPA-groups and EIA P(4) levels was 0.69 (P<0.001). Donors classified as having less P(4) than the standard yielded fewer corpora lutea (CL) (P<0.005), ova and embryos (P<0.05), and transferable embryos (P<0.05) compared with donors having similar or higher P(4) levels (3.4 +/- 1.0 vs 10.8 +/- 0.7 CL; 1.7 +/- 0.8 vs 6.2 +/- 0.9 ova and embryos; 1.2 +/- 0.7 vs 2.8 +/- 0.4 transferable embryos). Our results indicate that RMPA determines milk P(4) levels with sufficient accuracy and is a simple and useful tool for the screening of potential donor cows.

Sequential uterine horn versus simultaneous total uterine flush to recover bovine embryos nonsurgically

Beef cows were superovulated with follicle stimulating hormone (FSH) to compare two nonsurgical methods of embryo recovery from the uterus. In the first method each uterine horn was independently flushed with physiological saline solution (PSS) through a Foley catheter passed through the cervix and into the uterine horn. In the second method both uterine horns were simultaneously flushed with PSS by passing the catheter into the uterine body. In both methods, the numbers of ovulations were determined after embryo collection by counting the corpora lutea (CL) on both ovaries of each cow through a flank incision. Independent flushing (n = 19) averaged 6.4 embryos and 16.1 CL per cow for a recovery rate of 40%. Simultaneous flushings (n = 22) averaged 5.4 embryos and 17.7 CL per cow for a recovery rate of 31%. This difference between the recovery rates of the two flushing methods was not significant (P>0.05).

Effect of variability in response to superovulation on donor cow selection differentials in nucleus breeding schemes

The effectiveness of nucleus breeding schemes based on multiple ovulation and embryo transfer in practice is highly dependent upon the achieved reproductive rate. This study quantifies the effects of donor cow variability in response to superovulation (random and phenotypically correlated with milk yield) and failure rates (proportion of selected cows producing no transferable embryos) on the mean and variance of realized female selection differentials as affected by herd size, average embryo yield, and the coefficient of variation for embryo yield. Results show that differences in failure rates (0 to 40%) reduced realized female selection differentials up to 64%. The existence of a negative phenotypic correlation (-.3) between donor cow embryo yield and milk yield caused smaller reductions (up to 19%). Variability in realized female selection differentials is largest for small nucleus units and should not be neglected when planning the establishment of a nucleus breeding unit. The use of multiple flushes rather than a single flush per cow to produce the same average number of transferable embryos can reduce the variability in realized selection differentials but increases generation interval. Variability in response to superovulation will also affect inbreeding rates and the average accuracy of selection. Simulation studies are needed to quantify the total effect of variability in response to superovulation on the genetic responses possible in nucleus breeding schemes relying on multiple ovulation and embryo transfer.

Recovery of bovine oocytes from small vesicular follicles for in vitro maturation and fertilization

Five dairy and four beef breed, mature cows were used as oocyte donors to develop a system of multiple recovery of oocytes for in vitro maturation and fertilization. The animals were alternately treated with either 20 mg of follicle stimulating hormone (FSH) in four equal intramuscular injections or saline at 12 h intervals starting between days 9 and 13 of the oestrous cycle, and the procedure was repeated at three-week intervals for up to four collections. Eighteen collections resulted in the recovery of 124 oocytes from 181 follicles (69%). No serious side-effects were observed. Recovery was equally successful in both breeds and was not reduced in repeat attempts upon the same animal. Treatment with FSH only marginally increased the recovery rate (p less than 0.07) and did not affect the number of follicles aspirated (p greater than 0.05), which varied significantly (p less than 0.05) between cows. From 110 oocytes matured and fertilized in vitro, 70 embryos were recovered after culture in the rabbit oviduct or with trophoblastic vesicles in vitro, of which 30 had cleaved and 5 had progressed to an advanced stage of development. Hormone treatment did not affect zygote development (p greater than 0.05). Four non-surgical transfers of embryos obtained in these studies have resulted in two pregnancies determined ultrasonographically and the birth of a heifer calf. This suggests that the procedure for multiple oocyte recovery is safe and that it can be used successfully for obtaining oocytes for in vitro maturation and fertilization.

Superovulation and embryo recovery in Red deer () hinds

In two experiments, Red deer hinds were synchronized with intravaginal progesterone and were given 4 d of treatment (3 d before progesterone withdrawal and 1 d after) with an ovine follicle stimulating hormone (FSH) preparation which had a claimed low level of luteinizing hormone (LH) contamination. In Experiment 1, 12 hinds received one of four FSH levels by osmotic minipump. Hinds were run with fertile stags, and laparotomy and embryo recovery were performed 9 d after progesterone withdrawal. The ovulation rates (mean of three hinds per dosage) were 1.0, 2.0, 4.3 and 15.3 (number of corpora lutea counted) for estimated daily dosages rates of 0.036, 0.071, 0.11 and 0.14 units FSH preparation/day; the response to the increasing dosage was exponential (P<0.01). The recovery rate of ova on flushing was 38% (24 63 ), with all recovered ova being fertilized and of transferable quality. In Experiment 2, performed later in the breeding season, eight hinds received 0.14 units FSH/day either by minipump or by intramuscular injection. The mean ovulation rates were 3.0 and 11.0 (a significant difference, P<0.01), respectively, with a recovery rate of 72% (34 47 ), and with only 18 34 ova considered to be of transferable quality. The recovery rate in Experiment 2 was significantly higher than that in Experiment 1 (P<0.001). Overall, the results were better than those previously recorded for red deer, perhaps a function of both the FSH preparation used and an improved progesterone profile in estrus synchronization.

Ultrasonographic determination of ovarian follicular. Development in superovulated heifers pretreated with FSH-P at the beginning of the estrous cycle

On Day 3 of the estrous cycle (estrus = Day 0), dairy heifers were given either 10 mg i.m. FSH-P (FSH-P primed; n = 9) or a saline vehicle (saline primed; n = 9). On Day 10, all heifers were superovulated with FSH-P (total = 27.7 mg i.m.) in declining doses over 5 d. Heifers were inseminated artificially at estrus. From Day 2 until estrus, the number and size of follicles >2 mm were monitored daily by ultrasonography. The mean (+/- SEM) number of corpora lutea (CL) (6.2 +/- 1.5 vs 10.7 +/- 0.9; P<0.05) and the mean number of recovered embryos and unfertilized ova (3.6 +/- 1.7 vs 8.4 +/- 2.2; P<0.05) were lower in FSH-P-primed than in saline-primed heifers. Prior to initiation of superovulation, follicles >10 mm appeared on Days 6 to 7 in saline-primed heifers but only on Days 8 to 10 in FSH-P-primed heifers (P<0.05). Also, until Day 10, the mean number of follicles 4 to 6 mm and 7 to 10 mm was higher (P<0.05) in FSH-P-primed than in saline-primed heifers. After initiation of the superovulatory treatment (Day 10 to estrus), saline-primed heifers had a greater and faster increase in the mean number of follicles >10 mm (P<0.02) than FSH-P-primed heifers did. Depletion in the number of follicles 2 to 3 mm (P<0.001) between Day 10 and estrus and in the number of follicles 4 to 6 mm (P<0.05) between Day 12 and estrus occurred in both groups of heifers. Decreased superovulatory response and embryo recovery in FSH-P-primed heifers may have been due to the presence of large follicles (>10 mm) prior to the initiation of the superovulatory treatment which reduced the ability of small follicles to grow into larger size classes during superovulatory treatment.

Influence of summer heat stress on pregnancy rates of lactating dairy cattle following embryo transfer or artificial insemination

Lactating Holstein cows were used to determine if pregnancy rate from embryo transfer (n = 113) differed from contemporary control cows (n = 524) that were artificially inseminated (AI). Holstein heifers (n = 55) were superovulated with FSH-P (32 mg total) and inseminated artificially during estrus and subsequently managed under shade structures. On Day 7 post estrus, embryos were recovered, and primarily excellent to good quality embryos (90.3%) were transferred to estrus-synchronized lactating cows. Cows were managed under conditions of exposure to summer heat stress. Pregnancy status was determined by milk progesterone concentrations at Day 21 and palpation per rectum at 45 to 60 d post estrus. Pregnancy rates of cows presented for AI (Day 21, 18.0%; Days 45 to 60, 13.5%) were typical for lactating cows inseminated during periods of summer heat stress in Florida. Pregnancy rates of embryo recipient cows were higher (P<0.001) than those of control cows (Day 21, 47.6%; Days 45 to 60, 29.2%). Summer heat stress had no adverse effect on heifer superovulatory response, but it increased (P<0.05) the incidence of retarded embryos (</= 16 cells) and embryos graded as fair to poor quality. Increased pregnancy rate of recipient lactating cows indicates that the bovine embryo is sensitive to maternal heat stress during the first 7 d after estrus. Embryo transfer may bypass this period of embryonic sensitivity and provide an alternative to AI to partially circumvent heat stress-induced infertility in cattle.

Risk evaluation for bovine embryo transfer services using computer simulation and economic decision theory

A mathematical model was used to evaluate the dynamics and risks in bovine embryo transfer. Variables included embryo collection, fertilization, and transfer rates, plus overall pregnancy rates. Decision analysis was applied to three sets of 500 simulated flushes to test three strategies: 1) nonsuperovulation, 2) superovulation using follicle stimulating hormone (FSH) and 3) superovulation using pregnant mare serum gonadotropin (PMSG). Model validation involved comparing model performance against standards derived from 39 published studies. The model's repeatability was +/- 0.10 against standards in 93% of cases, and never exceeded +/- 0.13 in all 1500 simulations. Model outcomes were accurate to +/- 3% using average results. No pregnancies occurred in 22% of nonsuperovulated donors, 8% of FSH superovulated donors, and 6% of PMSG superovulated donors. PMSG treatment averaged more pregnancies per flush than FSH treatment (4.4 vs 3.9) but showed greater variation in response (64 vs 51%). Decision analysis suggests that a PMSG-induced flush would net $105 more than an FSH-induced flush, and that either superovulation strategy would yield approximately 10 times the net income of a nonsuperovulated flush. Pricing by response (PMSG) or by transfer (FSH) is optimal for the provider of embryo transfer services.

Superovulation and embryo recovery in goats treated with ovagen and folltropin

The purpose of the present study was to examine ovulation rates and embryo numbers and quality in goats of feral origin following treatment with either Folltropin (Vetrepharm Inc., Ontario, Canada) or Ovagen (Immuno-Chemical Products Ltd., Auckland). The mean +/- s.e.m. numbers of corpora lutea (CL) and embryos recovered after Ovagen treatment (N = 17 animals) were 16.2 +/- 2.1 and 12.6 +/- 1.9 respectively whereas after Folltropin treatment (N = 18 animals), the respective numbers were 16.3 +/- 1.8 and 10.2 +/- 1.6. The mean +/- s.e.m. numbers of good (i.e. transferable) embryos were 11.1 +/- 1.8 in the Ovagen group and 7.9 +/- 1.4 in the Folltropin group. AII the above values for each of the treatment groups were not significantly different from one another. There was a significant linear relationship between the number of CL and number of embryos (p<0.01; R = 0.925) after Ovagen treatment whereas there was no significant relationship after FolItropin treatment (p>0.05; R = 0.461). The proportions of animals producing more than five recoverable embryos after Ovagen (i.e. 76%) or Folltropin treatment (i.e. 72%) were similar although 22% of the Folltropin treated animals produced abnormal or prematurely regressing CL whereas no such CL were found after Ovagen treatment.

Effects of GnRH on superovulated cattle

Gonadotropin releasing hormone (GnRH) was given to 109 cows and heifers during the course of 224 superovulations. Follicle stimulating hormone (FSH) was administered twice daily (5 or 6 mg) for 3.5 to 4 days beginning on any of Days 9 to 14 of the estrous cycle; prostaglandin (45 mg PGF(2)alpha or 750 ug cloprostenol) was given in a split dose on the fourth day. Donor cows and heifers were placed into four groups according to previous superovulation treatments, which consisted of one to three treatments or of no previous treatment. Every other cow or heifer within each of the four subgroups was treated with GnRH (200 mug i.m.) at standing estrus. Only donors that exhibited estrus within 32 to 72 h after the first prostaglandin treatment were used in the study. Animals were inseminated artificially 12 and 24 h after standing estrus was first observed. No differences were noted in the number of ovulations, total ova or transferable embryos recovered from the GnRH or control groups; however, two interactions were detected. Cows given GnRH had fewer palpable corpora lutea than control cows (P < 0.05), but this difference was not seen in heifers. The second interaction was that GnRH seemed to depress ovulation rate in donors not previously superovulated, but this effect was not observed with subsequent superovulations. Cows yielded more total ova than heifers (P < 0.01). There was no difference in return to estrus between GnRH and control groups after a second prostaglandin treatment at the time of embryo recovery. Most donors within each group resumed cycling between 5 and 12 d after embryo recovery.

Improved embryo yield and condition of donor ovaries in cows after PMSG superovulation with monoclonal anti-PMSG administered shortly after the preovulatory LH peak

Nonlactating Dutch-Friesian cows were selected from a local slaughterhouse and synchronized with Syncro-Mate B. Cows with a normal progesterone pattern were treated with PMSG (3,000 I.U. i.m.) on Day 10 followed by PG (Prosolvin 22.5 mg) 48 h later. Blood samples were collected daily and at hourly intervals from 30 h after PG. Monoclonal anti-PMSG (Neutra-PMSG) was administered i.v. at 5.8 h after the LH peak in 16 cows; controls (n = 16) did not receive Neutra-PMSG. For comparison, 16 additional cows were superovulated with FSH-P in decreasing doses, twice a day (total 32 mg), starting at Day 10. All cows were inseminated at 10 h after the LH peak. Embryos were evaluated on Days 6 and 7 after flushing upon slaughter (recovery 87%). The number of corpora lutea and follicles on the donor ovaries were counted. No significant differences in the concentrations of progesterone and LH were observed between the three superovulation groups. Upon Neutra-PMSG, PMSG in blood was completely neutralized, it was decreased to < 0.5 ug/l at AI from 7.0 ug/l at the LH peak. The number of transferable embryos was significantly higher after Neutra-PMSG (9.1 per cow) than without Neutra-PMSG (5.3). or upon FSH-superovulation (4.6). The number of cysts on the ovaries of Neutra-PMSG-treated cows was reduced similarly to that after FSH-superovulation. Treatment with Neutra-PMSG shortly after the LH peak positively affects final follicular maturation in PMSG-superovulated cows and results in a nearly two-fold increase of transferable embryos.

Ovulatory response and embryo yield in superovulated holstein heifers given a priming dose of FSH-P at day 2 of the estrous cycle

Mature Holstein heifers were given either a priming dose of follicle-stimulating hormone-pituitary (FSH-P, 10 mg) or saline on Day 2 of the estrous cycle, or no pretreatment. All animals were subsequently given a decreasing dose superovulatory treatment of FSH-P beginning between Days 8 and 14, coupled with an injection of prostaglandin F2a to induce luteolysis. Pretreatment with FSH-P had no effect on the total superovulatory response or on the number of transferable embryos collected at Day 7 of gestation. Comparison of the results of our study with previous reports in the literature may suggest that FSH-priming early in the cycle may be advantageous in promoting superovulation only when the superovulatory response of the population of animals is otherwise weak.

Preovulatory evaluation of the superovulatory response in donor cattle

Dairy cows and heifers (n = 134) were induced to superovulate with exogenous gonadotrophins. In 103 animals, peripheral plasma concentrations of progesterone (P4) and luteinizing hormone (LH) were measured during the preovulatory period. On the basis of these measurements, normal and deviating profiles of P4 and LH were defined. A high degree of correlation existed between the normality of the two profiles; when the P4 profile was normal, the probability for the LH profile also to be normal was greater than 10:1. This relationship was utilized to evaluate donors based on four preovulatory measurements of P4. When used on 31 animals used for collection of eggs, a superior superovulatory response was encountered in animals with normal vs deviating P4 profiles (eggs recovered: 7.2 +/- 1.1 vs 0.5 +/- 0.3, P < 0.001; transferable embryos: 4.4 +/- 0.9 vs 0.3 +/- 0.2, P < 0.01). It is concluded that evaluation of donors by measurements of progesterone in plasma at four preovulatory sampling points allows for the early exclusion of donors with inferior embryo yield.

Embryonic development in superovulated dairy cattle exposed to elevated ambient temperatures between Days 1 to 7 post insemination

Holstein heifers (n = 29) were used to determine whether thermal stress during the first 7 d of embryonic development may increase the incidence of embryonic abnormalities in dairy cattle. Heifers were acclimated to environmental chambers at 20 degrees C for 9 d and superovulated with follicle stimulating hormone-pituitary (FSH-P; 40 mg total), beginning on Days 9 to 11 of the estrous cycle. Prostaglandin F(2)alpha (Lutalyse; 50 mg total) was administered on Day 3 of FSH-P. Heifers were inseminated artificially at estrus and then maintained at either thermal neutrality (20 degrees C) or under hyperthermic conditions (daily exposure up to 16 h at 30 degrees C and 8 h at 42 degrees C) for 7 d beginning at 30 h after the onset of estrus. On Day 7 post estrus, embryos were recovered nonsurgically and evaluated morphologically for stage of development and quality. The distribution of embryos classified as normal, abnormal, retarded or as unfertilized ova, differed (P<0.001) between heat stress and thermoneutral treatments. Only 20.7% of 82 embryos recovered from stressed heifers were normal compared with 51.5% of 68 embryos from thermoneutral animals. Stressed heifers had a higher incidence of abnormal and retarded embryos with degenerate nonviable blastomeres. Responses indicated that thermal stress from 30 h after the onset of estrus to Day 7 post estrus increases the incidence of abnormal and retarded embryos in superovulated heifers.

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).

Use of equine chorionic gonadotrophin in female mink

This study was comprised of three trials to determine the effects of equine chrionic gonadotrophin (eCG) on induction of sexual receptivity in female mink that had failed to mate by late in the breeding season. In the first trial one ovary was removed from unmated mink, which were then injected with 100 IU eCG. This treatment induced ovarian activity, including ovulation in the remaining ovary. In the second experiment, mink that had not been observed to mate were treated with 100 IU eCG or saline, resulting in mating of 10 11 of the eCG-treated animals, compared to 5 11 controls. Litter sizes were larger in mink in the control group, suggesting that eCG interfered with some phase of the reproductive process. In the third trial, 226 mink that had failed to mate until late in the breeding season were treated with 100 IU eCG. Of the 191 that subsequently mated, 99 produced litters, but litter sizes were reduced slightly from those observed in the remainder of the herd that bred without hormone treatment prior to March 20. Neonatal kit loss per female whelping was greater in mink treated with eCG. It is concluded that eCG treatment will induce mating in mink that refuse to mate, but this treatment results in reduced whelping success and greater neonatal kit loss. Its utility may be restricted to salvage situations where large numbers of mink fail to mate.

Effect of transportation stress on ovarian function in superovulated Hereford heifers

A study was conducted to determine the effect of transportation stress on ovarian function in superovulated heifers. Thirty cyclic Hereford heifers of similar age and weight and in good body condition were randomly assigned to control and stress-treated groups. All animals received two daily injections of 5 mg follicle stimulating hormone (FSH) for 4 d beginning on Day 10 to 12 of the estrous cycle. A blood sample was collected at each FSH injection. On the fourth day of injections, heifers were given 25 mg prostaglandin F(2)alpha (PGF(2)alpha) in the morning and a second injection of 15 mg PGF(2)alpha in the afternoon. During superovulation, the stressed heifers were transported to a different location every 12 h whereas control animals remained at the pretrial site. Following 4 d of intermittent transporting and FSH treatment, stress-treated heifers were recombined with control animals. Ovaries were examined 8 d following the onset of standing estrus to determine length, width, thickness, and number of corpora lutea (CL). Peripheral plasma levels of cortisol were higher in the stressed group (P< 0.1). Least squares means for numbers of CL were 20.4 +/- 2.1 and 15.4 +/- 1.7 for control and treated heifers, respectively (P< 0.1). There were no treatment differences (P> 0.1) between length, width, or thickness of ovaries when the number of CL was held constant. These data suggest that stress of the type, intensity, and duration imposed in this study increased plasma levels of cortisol and reduced ovulation rate as determined by CL formation in superovulated heifers.

Premature ovulations in superovulated cattle

The incidence and consequences of premature ovulations in superovulated cattle were studied. These ovulations, presumably induced by the luteinizing hormone content of the gonadotrophin preparation used, were found in 17 of 133 (13%) stimulated cows and heifers used as oocyte donors. In general this group of donors exhibited deviating periovulatory patterns of plasma hormone profiles (progesterone, estradiol17beta and LH), estrus behaviour, follicular steroidogenesis of progesterone and estradiol-17beta, and oocyte meiosis. It is concluded that superovulated donor cattle exhibiting premature ovulations constitute a group of poor oocyte donors that also must be considered as inferior embryo donors.

Effect of low dose of FSH given at the beginning of the estrous cycle and subsequent superovulatory response in Holstein cows

A total of 47 superovulations were conducted on forty non-lactating cows to evaluate two different schemes using follicle stimulating hormone (FSH) for superovulating cattle. Cows randomly assigned to treatment A (26 collections) were superovulated beginning on days 9 to 13 of the estrous cycle by giving FSH at decreasing doses of 6, 6, 5, 5, 3, 3, and 2, 2 mg for 4 consecutive days at 12-h intervals while those in treatment B (21 collections) also received 2.5 mg of FSH on days 3 and 4 of the estrous cycle. Animals in both treatments were each given 12.5 mg of prostaglandin F2alpha (PGF2alpha) at 60 and 72 h after the initiation of superovulatory treatment. Cows were artificially inseminated at 0, 12, and 24 h after the onset of estrus. Embryos were recovered nonsurgically on d 6 and morphologically evaluated. Ovaries of the cows were palpated at the end of flushings to assess the number of corpora lutea (CL). The mean interval from PGF2alpha to the onset of estrus was not different (P>0.05) for treatments A (56.6 h) and B (50.0 h). Also, mean duration of standing estrus was not different for either treatment (13.4 h vs 12.8 h). The mean number of CL palpated (7.3 vs 12.9) and ova recovered (5.5 vs 14.2) were significantly greater (P<0.05) for treatment B. The mean number of excellent and good embryos recovered was lower for treatment A animals, but not significant (P>0.05). Therefore, low doses of FSH given at the beginning of the cycle increased ovulation rate and embryo recovery in non-lactating cows.

The use of embryo collection techniques in Holstein heifers: A model to study early embryonic death

Twenty-three cyclic Holstein heifers were purchased for use as embryo donors to study the effect of intrauterine exposure to Haemophilus somnus on the number, quality, and viability of embryos produced. Few problems were encountered using standard superovulation and nonsurgical embryo collection techniques on virgin heifers. Based on three or more ovulations, as determined by palpation per rectum of the ovaries at the time of embryo recovery, 28 of 30 heifers responded to the superovulation regimen. Of 29 nonsurgical recoveries, 27 produced one or more embryos. One hundred and seventy-six embryos and ova were collected from heifers synchronized, superovulated, and flushed 7 to 8 d after insemination.

Superovulation in the cow using estradiol 17β or GnRH in conjunction with FSH-P

A study was designed to evaluate the superovulatory response in the cow when either estradiol 17beta or gonadotrophin releasing hormone (GnRH) was used in a superovulatory regimen with follicle stimulating hormone (FSH-P). Fifty-four cyclic crossbred females were superovulated in replicates between Days 8 and 12 of their cycle. All animals were treated with 28 mg of FSH-P in twice-daily decreasing doses, each receiving 500 mug cloprostenol (PGF) 48 h after initiation of treatment. Group 1 served as FSH-P controls, Group 2 received FSH-P and 400 mug of estradiol 17beta 36 h after PGF, and Group 3 received FSH-P and 250 mug GnRH 48 h after PGF. Inseminations with one vial of frozen semen were done at 12, 24 and 36 h after the onset of estrus. Ova/embryos were collected nonsurgically at Day 7 postestrus. Numbers of corpora lutea (CL) were recorded after palpation per rectum and the recovered ova and embryos were evaluated. All females were bled for endocrine examination. There were no differences in ovarian response among these treatments. Mean total ova/embryos collected in Group 3 was significantly higher than in Groups 1 or 2 (P < 0.05); however, no significant difference existed between groups in the mean numbers of fertilized or transferable embryos. Similarly, no significant differences existed between groups for recovery rate, fertilization rate, or percentage of transferable embryos. Serum estradiol levels were significantly higher at the expected end of ovulation in Group 2, and this tended to be associated with higher fertilization and transferable embryo rates. Furthermore, a significant positive correlation was found to exist between CL numbers and each of the ova/embryo parameters and the estradiol levels at estrus.

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

A comparison between different superovulatory treatments in dairy cattle was carried out at a commercial embryo transfer unit in Israel. Both pregnant mare serum gonadotrophin (PMSG) and follicle stimulating hormone (FSH) were used, either alone or combined with Syncromate B (SMB). The use of PMSG + SMB significantly decreased the number of corpora lutea present at the time of embryo collection 7 d after insemination, as compared with other treatment regimens. Consequently, a significantly lower number of ova was found in those animals treated with PMSG + SMB. Better superovulatory responses were obtained when FSH, rather than PMSG, was used, regardless of whether they were administered alone or combined with SMB. It was clear that the use of SMB combined either with PMSG or FSH resulted in poorer responses than when either gonadotrophin was used alone.

Ovarian function in Holstein cows immunized against pregnant mare serum gonadotrophin

Six Holstein-Friesian cows were immunized against pregnant mare serum gonadotrophin (PMSG) using Freunds' adjuvant during the mid-luteal phase of the estrous cycle. Antibody response was maintained by five booster immunizations at 2- to 3-wk intervals. Four cows were treated with a single intramuscular injection of PMSG (2350 I U) 107 d after primary immunization. Cloprostenol (500 ug) was administered at 56 h and 72 h after the treatment with PMSG; the cows were inseminated three times at 12-h intervals starting 56 h after cloprostenol treatment. Five days after insemination, the animals were slaughtered and their reproductive organs were recovered to quantify the population of corpora lutea and unovulated follicles (>10 mm dia). Antibody titres and progesterone concentrations were determined from blood samples collected either on alternate days or twice a week. Initially, progesterone concentrations were measured in milk samples. All cows produced antibodies, and titres were elevated within 6 to 9 d following each booster immunization. After each boost, however, the antibody titres declined rapidly. Progesterone concentrations declined to below 1 ng/ml after two weeks of initial immunization and remained low throughout the study, except in one cow that ovulated on Day 75. All animals were observed to have large follicular cysts during this period. Treatment with PMSG induced a single ovulation in one cow. Ovulations were neither induced by PMSG nor observed in any of the other animals. In PMSG-treated animals, the mean number of large follicles (5.0) was greater than in those which were not treated (2.0). The results of this study suggest that low titres of antibodies against PMSG are sufficient to disturb ovarian activity, result in follicular cysts and block multiple ovulations in response to exogenous PMSG.

Superovulatory and endocrine responses in heifers treated with FSH-P at different stages of the estrous cycle

Forty-two Holstein heifers were superovulated with FSH-P (total dose, 30 mg) and cloprostenol. Treatment was initiated on Day 3 (Group D3, n = 11), Day 6 (Group D6, n = 11), Day 9 (Group D9, n = 10) or Day 12 (Group D12, n = 10) of the estrous cycle. Heifers were bled daily for serum progesterone and estradiol-17beta determinations and every 6 h for a 48-h duration at the expected time of estrus for luteinizing hormone (LH) assay. Ova and embryos were flushed from the reproductive tracts and the number of corpora lutea (CL) were recorded after slaughter on Day 7 post-estrus. Mean (+/- SEM) numbers of observed CL were higher (P < 0.05) in Group D9 (33.3 +/- 4.8) than in Group D3 (15.3 +/- 3.8), with Group D6 (17.0 +/- 2.9) and Group D12 (23.9 +/- 7.3) being intermediate. Similarly, mean (+/- SEM) numbers of fertilized embryos were highest (P < 0.05) in Group D9 (13.3 +/- 2.2). There was also a nonsignificant trend for the number of transferable embryos to be greatest in Group D9. Neither serum progesterone concentrations 3 d after the LH peak nor peak serum estradiol 17beta concentrations differed among groups, but both were significantly correlated with numbers of observed CL and total ova and embryos.