Syncro-Mate-B Research Articles

Efficiency of single-sire mating programs with beef bulls mated to estrus synchronized females

Efficiency in reference to pregnancy rates of breeding beef bulls with estrus synchronized cows and heifers was tested. Most bulls (104 of 112) were given a breeding soundness examination and two 10-min libido/serving capacity tests. Females received either Syncro-Mate-B (SMB) or two injections of Prostaglandin F 2α (PGF) to synchronize estrus. They were assigned to single-sire breeding groups with bull-to-female ratios ranging from 1:7 to 1:51. Control groups consisted of untreated females maintained in single-sire breeding pastures with ratios from 1:24 to 1:37. Continuous observations of sexual activity were made for 30 h (SMB) and 48 h (PGF). After the 120-h posttreatment breeding period, females were placed in breeding pastures. During the synchronized breeding period the percentage of pregnant cattle of total treated was 43.5 ± 1.7% compared (P < 0.01) with 58.9 ± 3.3% for the control group after 23 d of breeding. At end of 28-d (treated) and 46-d (control) period, the percentage of pregnant females was 75.0 ± 2.4 and 79.6 ± 4.7, respectively (P > 0.05). In SMB trials, the percentages of females exhibiting estrus, those serviced at estrus and those pregnant following service during the synchronized breeding period were 90.8 ± 1.5, 73.3 ± 4.5 and 56.4 ± 5.6%, respectively. In PGF trials, the means for these same factors were 78.3 ± 2.4, 70.4 ± 5.9 and 56.1 ± 6.5%, respectively.

Comparison of Melengestrol Acetate-Prostaglandin F 2α to Syncro-Mate B for estrus synchronization in beef heifers

Three hundred and ten yearling heifers of various breeds were used in five trials to compare two estrus synchronization treatments. Treatment 1 consisted of Melengestrol Acetate-Prostaglandin F 2α (MGA-PGF 2α). Heifers were fed 0.5 mg MGA/head/d for 14 to 16 d. Sixteen or 17 d after the final MGA feeding, heifers were injected i.m. with 25 mg PGF 2α. Treatment 2 consisted of Syncro-Mate B (SMB). Heifers were given a 9-d norgestomet implant plus an injection containing 3 mg norgestomet and 5 mg estradiol valerate i.m. at implant insertion. Heifers were observed for estrus at 6-h intervals for 120 h after the end of treatments and were artificially inseminated 12 to 18 h after observed estrus. Heifers synchronized with MGA-PGF 2α and SMB had a similar (P > 0.10) estrous response (83.4 vs 90.2%) and a similar (P > 0.10) degree of synchrony (71.8 vs 79.0%) following treatment. However, the synchronized conception rate (68.7 vs 40.6%) and the synchronized pregnancy rate (57.3 vs 36.6%) were higher (P < 0.01) in MGA-PGF 2α than SMB heifers. Breeding season pregnancy rates were similar in both treatment groups. Heifers in both groups that were classified as cycling prior to initiation of treatment had improved reproductive performance following synchronization compared with those classified as noncycling. Based on higher synchronized conception and pregnancy rates and lower labor requirements and drug costs, the MGA-PGF 2α system appears to be a better method to synchronize estrus in beef heifers than the SMB system.

Breeding capacity, behavior and fertility of bulls with Brahman genetic influence during synchronized breeding of beef females

The objective of this experiment was to evaluate the feasibility of using bulls of Brahman-derived breeds for synchronized breeding of females treated with Syncro-Mate-B (SMB). Suckled, postpartum cows (n = 261) and virgin heifers (n = 227) were given the standard SMB treatment. Calves were removed from cows for 48 h beginning at implant removal, and individual bulls were placed in pens with 15 to 20 females ( x = 1:15.7 ) for 48 h beginning at implant removal. Bulls (n = 31) were 18 to 36 mo of age and had scored satisfactorily on a breeding soundness evaluation (BSE). The mean ± SEM percentage of females in estrus, percentage of estrous females serviced and percentage of total females serviced were 77.2 ± 2.4, 72.9 ± 2.9 and 55.7 ± 3%, respectively. Total average services per bull was 23.6 ± 1.6; however, average number of individuals serviced was only 8.6 ± 0.42. Mean ± SEM percentage of females conceiving of those serviced, percentage conceiving of those in estrus and percentage conceiving of total females available were 57.3 ± 3.7, 40.6 ± 2.6 and 32.6 ± 2.5%, respectively. Mean BSE scores of eight Simbrah bulls tested immediately before and 5 d after synchronized breeding did not differ (P > 0.05). These data suggest that the conception rate of Brahman-influenced bulls servicing SMB-synchronized cows is within the normal range. However, the total number of individual females serviced and the total pregnancy rate under the protocol employed was low. This occurred because all estrous females were not inseminated, and some bulls exhibited unpredicted low fertility.

Pregnancy detection with progesterone determinations in synchronized beef cows: Efficacy and improvement with multiple sampling

To achieve successful embryo transfer programs, ewes must be hormonally stimulated to induce multiple follicular development. Knowing the times of ovulation in these stimulated animals is critical for accurate timing of insemination. To determine the timing of ovulation in ewes treated with Syncro-Mate-B (SMB) and FSH, ewes (n=13) were implanted with SMB for 14 days and were treated with FSH twice daily for 4 days, starting on day 11 after SMB implantation. Ewes underwent laparoscopy at 36, 48, and 60 h after SMB removal (day 0) to count corpora hemorrhagica (CH), followed by laparotomy on day 8 to count corpora lutea (CL). Blood samples were taken every 6 h to record plasma LH, estradiol-17β, and progesterone concentrations on days 1–3, and one sample was collected before laparotomy on day 8. Ovulation rates (number of CH expressed as a percentage of the total number of CL) increased (P<0.01) from 4±2% at 36 h, to 50±7% at 48 h, to 67±7% at 60 h. Between 36 and 48 h after SMB removal, 50% of the follicles had ovulated, and between 48 and 60 h another 16% of the follicles had ovulated. However, at 60 h after SMB removal, approximately 30% of the follicles still remained unovulated. Plasma LH concentrations increased (P<0.05) from 1.4 ng/ml at 7:00 a.m. on day 1 to 10.1 ng/ml at 1:00 a.m. on day 2 and then decreased (P<0.05) to 0.6 ng/ml at the time of laparotomy (day 8). Plasma estradiol-17β concentrations increased (P<0.05) from 8.5 pg/ml at 7:00 a.m. on day 1 to 24.3 pg/ml at 7:00 p.m. on day 1 and then decreased (P<0.05) to 8.6 pg/ml on day 8. Progesterone concentrations were very low (<0.2 ng/ml) on days 1–3, but increased (P<0.01) to 4.3 ng/ml on day 8, after formation of the CL. These results demonstrate that the ovulation in SMB- and FSH-treated ewes occurs over an extended period of time and that almost a third of follicles do not ovulate until more than 60 h after SMB removal.

The effect of estradiol with Synchro-Mate-B in the superovulation of beef heifers with FSH-P

A study was conducted to determine whether luteal tissue formed after administration of exogenous luteinizing hormone (LH) was capable of maintaining pregnancy in the absence of the original corpus luteum (CL) of pregnancy in heifers. Nineteen beef heifers, confirmed pregnant by ultrasonography approximately 28 days after breeding, were randomly assigned to one of two groups. Nine heifers remained as untreated controls to determine the incidence of spontaneous embryonic or fetal loss. Each of the remaining ten heifers was given two Syncro-Mate-B (SMB) ear implants (12 mg of norgestomet) between 30 and 35 days after breeding (day of SMB implant was Day 1). An additional SMB was implanted on Day 8 and another on Day 15. All implants were removed on Day 20. On Day 2, SMB-implanted heifers were given an intramuscular (i.m.) injection of 500 μg of cloprostenol to induce luteal regression. On Day 5, regression of the CL was confirmed by ultrasonography and these heifers received a highly purified porcine LH preparation (50 mg Armour, i.m.); an additional 25 mg was injected i.m. on Day 6. Ovulation occurred in all ten LH-treated heifers and was detected on Day 7.2±0.1 (mean±SEM). In five of ten LH-treated heifers, the induced CL regressed, and was last detected by ultrasonography on Day 15.8±0.4 (range, Day 15–17). Pregnancy was not maintained in these heifers after SMB implants were removed. Pregnancy was maintained until Day 40 (end of experiment) in the remaining five LH-treated heifers and in all nine control heifers. In all five heifers in which the induced CL regressed, this CL had formed in the ovary contralateral to the original CL of pregnancy. In contrast, in four of five heifers in which the induced CL was maintained, this CL had formed in the ovary ipsilateral to the original CL of pregnancy. Although LH induced ovulation and CL formation in the absence of the CL of pregnancy and in the presence of continuous progestagen support, short-lived CL were formed in five of ten heifers.

Luteinizing hormone and progesterone concentrations in serum of heifers administered a short half-life prostaglandin (PGF 2α) or long half-life prostaglandin analogue (fenprostalene) on days six or eleven of the estrous cycle

Two trials were conducted to measure the progesterone (P 4) decline and luteinizing hormone (LH) surge in serum subsequent to administration of a short half-life (short t 1 2 ) prostaglandin (PGF 2α) or a long half-life (long t 1 2 ) prostaglandin analogue (fenprostalene) on Days 6 or 11 of the estrous cycle. Twenty-five crossbred Shorthorn and five Hereford heifers with a mean weight of 331.4 ± 29.8 kg were used in both trials. The heifers were randomly allotted to receive either a short t 1 2 or long t 1 2 prostaglandin treatment on Day 6 or 11 of the estrous cycle. A crossover design for the main effect, treatment (type of prostaglandin), was conducted. Heifers that received PGF 2α in Trial I were given fenprostalene in Trial II and vice versa. Stage of the estrous cycle (day) was the same for each heifer in both trials. Stage of estrous cycle was standardized to either Day 6 or 11 by administering Syncro-Mate B (SMB). Blood was collected every hour for 80 h post injection to quantify LH and P 4 concentrations. There were no significant differences (P > 0.05) between the short t 1 2 or long t 1 2 for either P 4 or LH profiles. In addition, no differences were detected between stages of the estrous cycle for the timing of the preovulatory surge of LH after prostaglandin administration.

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.

Serum and milk progesterone in Syncro-Mate-B treated postpartum beef cows

Fifteen post-partum (61.5±6.1 days) cyclic beef cows (4.1±0.3 years old) were randomly assigned to receive the Syncro-Mate-B (SMB) treatment on day 0 (estrus), day 9 or day 18 of their cycle with implant removal nine days later. An additional five post-partum (41.7±5.6 days) beef cows (3.2±0.4 years old) not detected in estrus and without corpora lutea also received the SMB treatment. Blood samples (10ml) were obtained via venipuncture on the day of implantation and one, three, five, seven and nine days after implantation and ten days after the post-treatment estrus. Milk samples (25 ml) were obtained by hand stripping at the same periods. Nineteen of twenty cows were synchronized, i.e. estrus occurred within five days of implant removal. Progesterone concentrations in both serum and milk were similar and followed similar patterns for each group. The day-9 treated cows had greater serum and milk progesterone concentrations than the other groups of cows on days 1, 3, and 5 after implantation. In conclusion, cows treated with SMB had similar serum and milk progesterone concentrations, endogenous progesterone secretion was inhibited by SMB treatment and the inhibition was influenced by prior luteal function.

Effect of steroids and/or 48 HR calf removal on serum luteinizing hormone concentrations in anestrous beef cows

Serum luteinizing hormone (LH) concentrations were quantified in 27 thin, anestrous cows with suckling calves in each of three treatment groups: Syncro-Mate-B (SMB), 48 hr calf removal (CR), and SMB plus CR (SMB + CR). The SMB treatment consisted of a 9 day ear implant containing 6 mg norgestomet and an intramuscular injection containing 3 mg norgestomet and 6 mg estradiol valerate given at the time of implant placement. In the SMB + CR group, CR began at the time of implant removal (0 hr). Blood samples were collected every 4 hr via puncture of a tail vessel beginning 12 hr prior to implant and/or CR and continued for 72 hr thereafter. Before implant and/or CR (−12 to 0 hr), LH concentrations were higher (P<.01) in the CR (1.1 ng/ml) group than in the SMB (.6 ng/ml) and SMB + CR (.8 ng/ml) groups. Following implant and/or CR (4 to 48 hr), LH concentrations increased (P<.01) in the CR (1.8 ng/ml) and SMB + CR (1.3 ng/ml) groups, but remained unchanged in the SMB (.7 ng/ml) group. Furthermore, LH concentrations were higher (P<.05) in the CR group compared to the SMB + CR group. Circulating concentrations of LH declined (P<.01) to 1.2 ng/ml in the CR group following calf return, but remained unchanged in the other two groups. Although more (P<.01) cows in the SMB and SMB + CR groups were detected in estrus than in the CR group, there was no difference (P.10) in the number of cows ovulating between the three treatment groups. These results suggest that CR will increase circulating LH concentrations by 24 hr post CR and that SMB may partially suppress the CR induced LH release following implant and calf removal.

Pregnancy rate in peripuberal beef heifers following treatment with syncro-mate-B and gonadotropin releasing-hormone

A study was conducted to evaluate the effectiveness of treatment with Syncro-Mate-B (SMB) d d G. D. Searle and Company, Chicago, IL 60680 and gonadotropin releasing-hormone (GnRH) on inducing a fertile estrus and/or ovulation in peripuberal beef heifers. Two hundred and twenty-three, 13 to 15 month peripuberal beef heifers, primarily of Angus or Simmental breeding, were alternately allotted by weight and age within breed to a non-treated control group (C) and three groups which received the SMB treatment regime. Treated groups differed in that one group was inseminated approximately 12 hr after detected in estrus (T) while two other groups were inseminated at a fixed time after implant removal (T-G-I42, T-I48). Heifers in group T-G-I42 received 125 μg GnRH at 30 hr, and were inseminated 42 hr after implant removal. The remaining group of SMB-treated heifers received no additional hormone therapy but were inseminated 48 hr after implant removal (T-I48). Age had no significant effect on estrous response or pregnancy rate nor were there significant age by weight interactions on these parameters. Weight was a significant source of variation on interval from start of breeding to pregnancy (P<.01) and the effect on interval to estrus approached statistical significance (P<.0.9). In control heifers, increased weight had a positive effect on estrous response during the first 21 days of breeding (P<.05). Conversely, weight had no effect on estrous response during the 5-day synchronized period in heifers treated with SMB and observed for estrus (group T). Cumulative estrous response in control heifers was 10, 47, 48 and 55% in 5, 21, 27 and 45 days of breeding, respectively. Cumulative estrous response in SMB-treated heifers obsrved for estrus (group T) was 88, 91, 91 and 91% in 5, 21, 27 and 45 days of breeding, respectively. Pregnancy rate after 5 days of breeding was 9, 27, 18 and 30% for heifers in groups C, T, T-G-I42 and T-I48, respectively. Pregnancy rate after 21 days of breeding for heirfers in groups C, T, T-G-I42 and T-I48, respectively, was 33, 38, 21 and 41%; after 27 days of breeding was 36, 43, 40 and 48%; after 45 days of breeding was 48, 61, 51 and 69% and after the total 88-day breeding season was 59, 68, 71 and 72%. While a large percentage of peripuberal beef heifers with adequate age but insufficient weight were induced into estrus with the SMB treatment, pregnancy rates were low. Timed insemination programs with or without GnRH do not appear to be effective in improving pregnancy response in non-cyclic beef heifers.

Endogenous hormone response and fertility in dairy heifers treated with norgestomet and estradiol valerate.

Seventy postpuberal dairy heifers were assigned to remain untreated (n = 26) or to receive the Syncro-Mate-B (SMB) treatment (n = 44). Untreated heifers were inseminated at 12 hr after detection of estrus, while SMB-treated heifers were inseminated either at 48 hr after implant removal (group 1) or at 12 hr after detection of estrus (group 2). Jugular blood was collected at regular intervals from four untreated heifers and from 20 SMB heifers. In untreated heifers, estradiol-17 beta (E) was unchanged throughout the estrous cycle. Progesterone (P) reached maximum concentrations during the luteal phase and then declined to less than 2 ng/ml before estrus. Follicle stimulating hormone (FSH) ranged between 50.1 and 100.2 ng/ml during the estrous cycle, then reached a peak (P less than .05) concentration of 516.2 ng/ml coincident with peak luteinizing hormone (LH) concentration at 12 hr after the detection of estrus. In SMB-treated heifers, plasma E increased by 12 hr after injection of estradiol valerate and then declined throughout the rest of the sampling period. P declined to less than 2 ng/ml by 24 hr after administration of the SMB treatment and remained low throughout the sampling period. FSH declined in response to SMB treatment, then reached a peak (P less than .05) concentration coincident with peak LH 40 hr after implant removal. First service pregnancy rates among the untreated, group 1 and group 2 heifers, were 65, 58 and 38%, respectively, and did not differ (P greater than .05). SMB treatment was effective in inducing luteolysis and in suppressing estrus and peak gonadotropin release. Intervals from implant removal until estrus and from implant removal until peak gonadotropin release were highly variable among SMB-treated animals.

Pregnancy rate among beef heifers from timed insemination following synchronization with a progestin treatment.

Five trials were conducted with 958 virgin beef heifers to evaluate the effects of various breeding management methods on pregnancy rate at synchronized estrus and during a 45-day artificial insemination (AI) season. Synchronization was achieved with the progestin treatment regimen Syncro-Mate-B (SMB). Pregnancy rate at first service and cumulative pregnancy rate were affected (P less than .01) by trial. Pregnancy rate at first service was 55% for all heifers on the SMB treatment regimen and 67% for nontreated control heifers (P less than .01). However, cumulative pregnancy rate during the 5-day synchronized period was higher (P less than .01) among treated heifers (54%) than among control heifers (21%). The pregnancy rate was 6% higher (P less than .06) after 27 days of breeding for treated heifers than for control heifers. Neither pregnancy rate at 21 days nor final pregnancy rate after a 45-day AI season was significantly affected by treatment. Pregnancy rate at first service among heifers undergoing the SMB treatment regimen and inseminated 12 hr after first detected in estrus was not significantly different from that among heifers inseminated once from 45 to 55 hr after implant removal or heifers inseminated twice at 48 and 60 hr after implant removal, regardless of occurrence of estrus.

Conception rates in synchronized beef cows with and without monensin feeding.

Two groups of Hereford and two groups of Hereford crossbred beef cows were each divided into herds of 74 to 76 cows. Forty nine to 51 cows in each herd were synchronized with the Syncro-Mate-B (SMB) treatment and inseminated once between 48 and 52 hr after removal of the implant. The other 25 cows served as controls and were bred naturally. All herds received 2.27 kg/head/day of a corn-based supplement plus corn silage fed ad libitum for 15 days before and 20 days after the scheduled insemination date. In addition, one herd of each breed group was fed 250 mg of monensin/head/day during the same period. Overall conception rates for control and SMB-treated cows were 77 and 84.3%, respectively, and were not significantly different. Conception rates for the SMB-timed insemination were lower (P < .10) for Herefords than for crossbreds, averaging 34.9 and 48.5%, respectively. There was no difference in conception rates due to monensin treatment. Rumen samples taken 3 to 4 hr after feeding showed a lower ratio of acetate to propionate for Herefords fed monensin as a result of a lower proportion of acetate and a higher proportion of propionate in those animals.

The effect of calf removal on estrous response and pregnancy rate of beef cows after SYNCRO-MATE-B treatment

The effect of calf removal on estrous response and pregnancy rate of cows given SYNCRO-MATE-B (SMB) was determined. Two hundred forty three lactating beef cows treated with SMB were allotted to three treatments: treatment 1, no calf removal; treatment 2, 24 hr calf removal and treatment 3, 48 hr calf removal. Calf removal time began with removal of the SMB implant. All cows were artificially inseminated 48 to 54 hr after implant removal. Body condition of cows in each heard was visually appraised as adequate or marginal. At each location, technicians and sires were stratified across all treatments. Estrous response of cows (n=143) was different (P<.01) between treatments which averaged 23, 40 and 77 percent for treatments 1, 2 and 3, respectively. Pregnancy rates of cows (n=243) after the first artificial insemination (AI) were 32, 28 and 46 percent for treatments 1, 2 and 3, respectively. The pregnancy rate was greater (P<.05) for treatment 3 than other treatments. After 25 days of breeding, the pregnancy rates were 59, 58 and 72 percent, respectively, for the three treatments. There was a linear relationship between days postpartum at the time of treatment and estrous response (P<.01) and first service pregnancy rate (P<.05). The partial regression coefficients for estrous response and first service pregnancy rate were 1.2 and .6 percent, respectively. In summary, estrous response and pregnancy rate of lactating beef cows treated with SMB were increased by 48 hr calf removal, compared to no calf removal or 24 hr calf removal, when calf removal time began with removal of the SMB implant.

Estrus and pregnancy in beef heifers following use of the Syncro-Mate-B treatment (SMB)

Five studies were conducted in yearling heifers which were either puberal or prepuberal utilizing the Syncro-Mate-B (SMB) treatment (G. D. Searle & Co., Chicago, Ill.). In trial 1 the pregnancy rate in Brahman crossbred heifers after 21 days of breeding was 56% and 28% greater (P<.005) in the SMB treated groups than in the nontreated groups. Pregnancy rate in 3 4 Simmental heifers (trial 2) was increased 39% (P<.05) after 21 days of breeding. Hereford and crossbred heifers (trial 3) weighing less than 250 kg failed to respond to SMB treatment whereas heifers weighing greater then 250 kg had increased reproductive performance. Conversely the results obtained in trial 4 using Brahman crossbred heifers was not influenced by weight or SMB treatment. Crossbred Santa Gertrudis heifers (trial 5) weighing greater then 250 kg and treated with SMB had improved reproductive performance compared to the control groups. While in treated heifers weighing less than 250 kg reproductive performance was far from optimum.