scholarly journals 113 Influence of cattle stress response to restraint method on artificial insemination pregnancy rates

2019 ◽  
Vol 97 (Supplement_1) ◽  
pp. 41-42
Author(s):  
Russell C Carrell ◽  
William B Smith ◽  
Lea A Kinman ◽  
Vitor R G Mercadante ◽  
David Roper
Keyword(s):  
Pregnancy Rate ◽  
Stress Responses ◽  
Artificial Insemination ◽  
Bos Taurus ◽  
Physiological Stress ◽  
Negative Impact ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Restraint Mechanism ◽  
In Pregnancy

Abstract Activation of physiological stress responses have been associated with decreased pregnancy rates in beef cattle. Therefore, alternative cattle restraint methods have been developed to reduce this negative impact. However, little evidence exists comparing pregnancy outcomes of differing methods. Thus our objective was to determine if a difference was present in pregnancy rate to fixed-time artificial insemination in Bos taurus beef females when using a breeding box (b) versus a squeeze chute (c). Cows and heifers from two separate locations (Virginia Tech University, VT; and R.A. Brown Ranch, RAB) were exposed to FTAI protocols at location of origin while restrained in a squeeze chute (n = 169) or a breeding box (n = 162). Females were exposed to the 7 day Co-Sync + CIDR protocol pre-breeding. At day of breeding, females were randomly assigned to treatment. Immediately following breeding, blood was collected via coccygeal venipuncture for assessment of plasma cortisol concentration using an automated ELISA assay (Immulite 2000 XPi, Siemens). Chute and Exit Score (1–5) were assessed at the time of breeding by a trained technician at each location. Pregnancy was verified thirty days post-breeding via rectal ultrasonography. Pregnancy rate (PROC FREQ) and cortisol (PROC GLIMMIX) were analyzed using SAS version 9.4. Also, a Linear Regression Model (SAS version 9.4) was used to determine relationships between chute score, exit score, and cortisol. It was found that there was no difference in pregnancy rate between the breeding box and the squeeze chute (61.73% vs 64.71%, P = 0.31, respectively). Cortisol showed no difference between b and c (59.44±10.17 vs 58.61±10.16, P = 0.68, respectively). There was no linear relationship between cortisol, exit score, and chute score (P = 0.14). It can be concluded that stress responses are similar between the breeding box and squeeze chute. Therefore females will have similar pregnancy rates when exposed to FTAI in either restraint mechanism.

scholarly journals Effect of progesterone, human chorionic gonadotropin and progesterone + human chorionic gonadotropin treatment on conception rates in repeat breeder cows

2020 ◽  
Vol 89 (4) ◽  
pp. 307-315
Author(s):  
Hasan Alkan ◽  
Huseyin Erdem
Keyword(s):  
Pregnancy Rate ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Group 4 ◽  
Prostaglandin F ◽  
Repeat Breeder ◽  
Group 1

The aim of this study was to investigate the effects of hormonal support on the pregnancy rate in repeat breeder cows. Prostaglandin F2α + Ovsynch oestrus synchronization protocol was applied to the cows. Following the fixed time insemination (day 0), the cows were divided into 4 groups. In Group 1 (n = 42), progesterone releasing intravaginal device (PRID) was placed vaginally at 84 h and removed on the 9th day after the artificial insemination. In Group 2 (n = 40), the cows were administered human chorionic gonadotropin (hCG) on the 7th day. Group 3 (n = 45) was applied a combination of progesterone and hCG. Group 4 (n = 42) was not given any treatment. Blood samples were collected from all cows 4 times on days 3.5, 7, 12, and 18 to evaluate progesterone concentrations. The pregnancy rates were 40.47%, 37.50%, 44.44%, and 30.95% in Group 1, 2, 3, and 4, respectively (P > 0.05). In addition, in cows with progesterone concentrations <2 ng/ml on day 3.5, the pregnancy rates were found to be lower than in the cows with progesterone concentrations >2 ng/ml in Group 4 (P < 0.05). Progesterone supplementation in cows with progesterone concentrations < 2 ng/ml appeared to increase pregnancy rates (P < 0.05) in Groups 1 and 3. As a result, post-insemination hormonal applications in the repeat breeder cows did not increase the pregnancy rate. However, it was concluded that determination of progesterone concentrations on day 3.5 following artificial insemination and then hormonal support in the cows with low concentrations would increased the pregnancy rate.

Artificial insemination of farmed red deer (Cervus elaphus)

1990 ◽  
Vol 51 (3) ◽  
pp. 613-621 ◽  
Author(s):  
P. F. Fennessy ◽  
C. G. Mackintosh ◽  
G. H. Shackell
Keyword(s):  
Pregnancy Rate ◽  
Cervus Elaphus ◽  
Artificial Insemination ◽  
Red Deer ◽  
Pregnancy Rates ◽  
Progesterone Treatment ◽  
Serum Gonadotropin ◽  
The Difference ◽  
Fixed Times ◽  
In Pregnancy

ABSTRACTSix experiments involving the artificial insemination (AI) of a total of 300 female red deer (hinds) with frozen-thawed red deer semen (collected by electro-ejaculation) were conducted over 3 years. Insemination took place at fixed times following various oestrous synchronization procedures using progesterone withdrawal and treatment with pregnant mare's serum gonadotropin (PMSG). In the 1st year, the experiments evaluated basic AI techniques in which pregnancy rates were 45% in 20 hinds receiving two inseminations per vaginam (PV) and 56% in 27 hinds inseminated by the laparoscopic intrauterine method (IU). In the 2nd year, the experiments involved comparisons of the progesterone regime, one or two PV inseminations, and the timing of a single PV insemination. There was no effect of replacement of the progesterone device after 9 days and withdrawal 3 days later compared with the use of one device for the whole period in two experiments. The pregnancy rate for a double PV insemination was significantly higher than for a single PV insemination (58 and 34%; P < 0·05) and there was also a small effect of timing of insemination relative to the synchronization treatment. In the 3rd year all hinds were inseminated by the IU method. The experiments involved a comparison of various times of AI following progesterone withdrawal and a comparison of the progesterone regime. The overall pregnancy rate for 63 hinds inseminated was 56% with no difference between three times of insemination (48, 52 and 55 h). In the second experiment, the difference in pregnancy rate between treatment with progesterone for 15 days and 12 days (44 and 72% for 18 hinds per group) was not significant, but the interaction between the length of progesterone treatment and insemination time was significant (P < 0·05), with the 12-day progesterone/55 h insemination giving a much higher pregnancy rate than the 15-day/55 h insemination (89 and 20% respectively). Although no experiments involved direct comparisons of the routes of insemination, overall pregnancy rates were 56% for IU, 53% for double PV and 35% for single PV inseminations.

scholarly journals Evaluation of follicular growth and progesterone production in Bos taurus cows strategically treated with insulin

2019 ◽  
Vol 40 (5Supl1) ◽  
pp. 2287
Author(s):  
Andressa Stein Maffi ◽  
Mityelle da Costa Chaves Rodrigues ◽  
Lucas Balinhas Farias ◽  
Joabel Tonellotto dos Santos ◽  
Gabriela Bueno Luz ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Artificial Insemination ◽  
Bos Taurus ◽  
Fixed Time ◽  
Estradiol Benzoate ◽  
Control Group ◽  
Follicular Growth ◽  
Insulin Group ◽  
Vaginal Device

The goal of this study was to evaluate the effects of strategic insulin administration on follicular growth, progesterone production, and pregnancy rate in beef cattle. Two experiments were conducted, in experiment 1, 215 cows crossbreed cows (Bos indicus × Bos taurus) (Control Group, n = 109; Insulin Group, n = 106) were submitted to fixed-time artificial insemination (TAI) with application of 2 mg of estradiol benzoate and a vaginal device containing progesterone on day 0. On day 9, the device was removed and 0.5 mg of estradiol cypionate was administered with 12.5 mg of dinoprost and 0.25 UI kg-1 of insulin for the treated animals. On day 11, artificial insemination (AI) was performed on all animals. On days 9 and 11 according to the protocol, was evaluated follicular growth and estrus manifestation, and 30 days after AI the pregnancy rate. In experiment 2, 85 cows were utilized, including Aberdeen Angus, Hereford, and crossbreeds (Control Group, n = 49 and Insulin Group, n = 36), and were submitted to the protocol for fixed-time embryo transfer (FTET), and progesterone concentrations were evaluated. On day 0, the cows received 2 mg of estradiol benzoate and a vaginal device containing progesterone. On day 5 of the protocol, 0.150 mg of cloprostenol was administered. On day 8, the vaginal device was removed and 20 mg of purified porcine pituitary extract and 0.25 UI kg-1 of insulin was given to the animals in the treatment group, and on day 9, 1 mg of estradiol benzoate was administered. On day 17, an embryo transfer was performed and blood collection for evaluation of progesterone levels in animals submitted to FTET were collected. In experiment 1, the follicular growth rate and the pregnancy rate were similar between groups (P > 0.05) and in experiment 2, the production of P4 was not different between the animals that received the insulin application and the control group. The utilization of a single dose of insulin for beef cows did not affect the ovulatory follicular diameter, progesterone concentrations, or pregnancy rate.

scholarly journals Comparative Study Between Different Methods of Insemination in Iraqi Does

2011 ◽  
Vol 35 (2) ◽  
pp. 95-104
Author(s):  
HA . AL-Mutar
Keyword(s):  
Comparative Study ◽  
Pregnancy Rate ◽  
Breeding Season ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Experimental Animals ◽  
Pregnant Mare Serum Gonadotropin ◽  
Abdominal Palpation ◽  
Serum Gonadotropin ◽  
In Pregnancy

Present experimental was carried out on 22 does 2-4 years old. The aim was to induction of estrous in non-breeding season using impregnated sponge with 20 mg of medroxy progesterone acetate (MPA) for 13 days and with an i/m injection of 500 IU Pregnant Mare Serum Gonadotropin (PMSG) hormone 24 hrs before sponge withdrawal and to compare the pregnancy rate using three different methods of insemination; natural , cervical and laparoscopic artificial insemination at fixed time 24-48 hrs after estrous onset. All does were showed signs of estrous (100%), the estrous time was 46.9±4.90hrs (24-60hrs) after sponge withdrawal. While estrous length was 37.09±1.91 (24–72hrs). All experimental animals followed up by abdominal palpation, ultrasonography at 30, 60 and 90 days post-insemination, while the laparoscopic examination was performed at day 30 post-insemination, to improve the efficiently of the different methods of inseminations in pregnancy rate ultrasonographical diagnosed by rectal and abdominal methods of 14 does post-inseminations appeared that two were pregnant, seven suspected and five non pregnant. At day 60th , post-insemination the pregnancy diagnosis of (22) does appeared that (14) were pregnant, six suspected and two non pregnant. While at day 90, the examination of all does appeared that (16) animals were pregnant and six were not. The laparoscopic examination, at 30 days post-insemination showed that eight does were pregnant, two suspected and two were not pregnant. In conclusion that the pregnancy rate of laparoscopic insemination is (75%), comparisons to natural (66.7%) and cervical AI method (75%) but there is no significant different between them, while the kidding percentage was appear in natural insemination (75%), cervical (100%) and laparoscopic insemination (150%). The results of this study indicate that estrus can be efficiently induced in female goats during non-breeding season using 20mg MPA impregnated spongewith 500IU PMSG.

scholarly journals STRATEGIES TO INCREASE FERTILITY DURING FIXED-TIME ARTIFICIAL INSEMINATION IN BEEF CATTLE

SPERMOVA ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 73-82
Author(s):  
Ana Clara Canto Souza ◽  
◽  
Gabrieli Dutra Gonçalves ◽  
Andrey Osvaldo Souza Ferro ◽  
Deborah Nakayama Yokomizo ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Estrous Cycle ◽  
Breeding Season ◽  
Critical Points ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Follicular Wave ◽  
New Strategies ◽  
In Pregnancy

The application of Fixed Time Artificial Insemination (FTAI) protocols has strongly boosted artificial insemination in Brazilian bovine herds. The control of the estrous cycle with protocols based on progesterone and estrogen involves synchronizing the emergence of a follicular wave, controlling the progesterone phase, and inducing ovulation in a synchronized manner. The increase in pregnancy rates starts with the preparation of the breeding season and the choice of protocols and females. Thereafter, based on the characteristics of the property and the lots of animals, small adjustments can be made to the hormonal protocols as needed. Finally, resynchronization can increase usability by allowing multiple inseminations within short periods. The search for new strategies is of paramount importance for the development of the FTAI protocol and the increase in final pregnancy rates. Thus, this review sought to highlight the main critical points and adjustments of the FTAI protocols and their applicability in the reproduction of beef cattle.

scholarly journals Pregnancy rates in hair sheep after Ovsynch synchronization and a combined intracervical fixed-time artificial insemination and 10-day mating period

2019 ◽  
Vol 12 (11) ◽  
pp. 1779-1783
Author(s):  
D. A. Vallejo ◽  
J. D. Londoño ◽  
Y. A. Yepes ◽  
V. Tamayo ◽  
A. F. Mejia ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Prostaglandin F2α ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Control Group ◽  
Mating Period ◽  
Mating Group ◽  
Alternative Materials ◽  
And Control

Aim: This study aimed to evaluate the pregnancy rates in hair ewes using an Ovsynch synchronization protocol under a breeding system that combines fixed-time insemination plus a 10-day mating period as an alternative. Materials and Methods: Through an experimental study (n=27), ewes were randomly located into one of three treatments: (1) Pre-synch (n=9): Prostaglandin F2α (PGF2α)+Gonadotropin-releasing hormone (GnRH)+PGF2α+GnRH; (2) Ovsynch (n=9): GnRH+PGF2α+GnRH; and (3) control: Ewes bred by natural mating (NM) (n=9). Ewes were fixed-time inseminated (fixed-time artificial insemination [FTAI]) with fresh semen, collected just before the insemination time through vaginoscopy at 16 h after the second GnRH (gonadorelin) injection. Each experimental group was placed separately during 15 days and, after this time, fertile rams were allowed back with ewes for a 10-day mating period. Control group ewes remained with the rest of the herd suitable for breeding and were bred under NM. Pregnancy diagnosis was performed by ultrasound at 28-, 56-, and 84-day post-breeding to differentiate between FTAI and NM pregnancies. Total (FTAI±NM) pregnancy rates at 56-day post-breeding were used to compared Pre-synch, Ovsynch, and control. For this purpose, two-tailed proportions comparison z-test was used with a 95% confidence level, for testing as the null hypothesis whether two proportions were equal. Results: Pregnancy rates were higher in control ewes (66.4%) than FTAI (46.6%). When pregnancy rates after a 10-day mating period (40%) were added, the final rate (86.6%) was significantly (p<0.05) higher in Ovsynch-based protocols. The pregnancy rate was significantly lower in FTAI ewes compared to FTAI +10-day mating group (p<0.05). The overall pregnancy rate was 88.0, 85.7, and 67.0 (p>0.05) for Pre-synch, Ovsynch, and control ewes, respectively. Conclusion: These results provide evidence on the benefits of combined FTAI protocols for improving the reproductive efficiency of sheep.

22 PREGNANCY RATES IN DAIRY COWS TREATED WITH PROGESTERONE-RELEASING DEVICES AND DIFFERENT GONADOTROPIN-RELEASING HORMONE OR ESTRADIOL PLUS EQUINE CHORIONIC GONADOTROPIN FIXED-TIME ARTIFICIAL INSEMINATION PROTOCOLS

2008 ◽  
Vol 20 (1) ◽  
pp. 91 ◽  
Author(s):  
G. Veneranda ◽  
L. Filippi ◽  
D. Racca ◽  
L. Cutaia ◽  
G. A. Bo
Keyword(s):  
Dairy Cows ◽  
Pregnancy Rate ◽  
Milk Yield ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Gonadotropin Releasing Hormone ◽  
Pregnancy Rates ◽  
Device Removal ◽  
Treatment Groups ◽  
Lactating Dairy Cows

We have previously shown that the addition of eCG improved pregnancy rates following fixed-time artificial insemination (FTAI) in lactating dairy cows treated with estradiol benzoate (EB) and progesterone releasing devices (Veneranda et al. 2006 Reprod. Fertil. Dev. 18, 118). An experiment was designed to compare pregnancy rates in lactating dairy cows treated with progesterone-releasing devices and EB plus eCG with different gonadotropin-releasing hormone (GnRH)-based protocols. Five-hundred lactating dairy cows between 30 and 51 days postpartum (when prostaglandin F (PGF) treatments were given in the Pre-Synch groups), with a milk yield of 29.5 � 7.0 kg per day (range 13.0 to 46.0 kg) and a body condition score (BCS) between 2.5 to 3.5 out of 5 were used. Cows were blocked by days postpartum and randomly assigned to five treatment groups. Cows in the Pre-Synch group received PGF 28 and 14 days prior to the insertion of a DIB device (1 g progesterone, Syntex SA, Buenos Aires, Argentina) and the administration of 50 µg of Lecirelin (GnRH, Ovusin, Syntex SA) IM (Day 0). On Day 7, DIB were removed and cows received PGF (0.5 mg cloprostenol, Ciclase, Syntex SA). On Day 9, cows received a second GnRH treatment and were FTAI 16 h later (60 h after device removal). Cows in the Modified Pre-Synch group were treated similarly except that they received a DIB for 7 days prior to the second PGF injection and no DIB at the time of the first GnRH. Cows in the P4-Synch group were treated as those in the Pre-synch group but did not receive the two doses of PGF 28 and 14 days earlier. Cows in the P4 + EB + eCG groups received a DIB for 8 days, 2 mg of EB at DIB insertion (Day 0), and PGF and 400 IU eCG (Novormon, Syntex SA) IM at DIB removal (Day 8); they were subdivided to receive 1 mg of EB on Day 9 (P4 + EB + eCG + EB group) or GnRH on Day 10 (P4 + EB + eCG + GnRH group). Cows in these latter two groups were also FTAI 60 h after device removal. Pregnancy was determined by rectal palpation 50 days after FTAI and data were analyzed by logistic regression. Pregnancy rates were not affected by BCS, days postpartum, or milk yield (P > 0.5). However, there was a significant group effect due to a higher (P < 0.05) pregnancy rate in the P4 + EB + eCG + EB (49%) and P4 + EB + eCG + GnRH (44%) treatment groups than in those in the Modified Pre-Synch group (30%). Pregnancy rate in the P4-Synch group (39%) was lower (P < 0.05) than those in the P4 + EB + eCG + EB group but not different from the others. Finally, pregnancy rate in Pre-Synch group (41%) was intermediate and not different from the other treatment groups. Results of these experiments suggest that treatments with progesterone-releasing devices, EB, and eCG result in pregnancy rates that are comparable to or better than those obtained in GnRH-based protocols in lactating dairy cows. Further studies are needed to investigate whether eCG could increase pregnancy rates in cows treated with GnRH and progesterone-releasing devices. The authors thank Syntex SA for providing the hormones used in the study.

49 USE OF DILUTION OF CRYOPRESERVED SEMEN IN FIXED-TIME ARTIFICIAL INSEMINATION OF MANGALARGA MARCHADOR MARES

2012 ◽  
Vol 24 (1) ◽  
pp. 136
Author(s):  
M. B. R. Nogueira ◽  
A. C. F. Farinasso ◽  
A. C. Rezende ◽  
T. L. C. Pinto ◽  
J. C. Souza
Keyword(s):  
Osmotic Stress ◽  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Binomial Distribution ◽  
Osmotic Shock ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Ovulatory Follicle ◽  
Frozen Semen

Equine AI with frozen semen has become more frequent in reproduction centers, but osmotic shock during thawing is still a major problem as it impairs gamete viability and fertility. To overcome this, multi ultrasonographic (US) exams must be performed to ensure AI at the closest time to ovulation possible. The objective was to evaluate, in vivo, the effects of dilution of the cryoprotectant dimethylphormamide on the success of a fixed timed (20 h post-ovulation) AI protocol, in an attempt to reduce osmotic shock and the intense labour usually required during equine AI with frozen semen. Thirty-five Mangalarga Marchador mares were used in this trial. When dominant follicles reached at least 35 mm in diameter, ovulation was induced with 6 mg of equine gonadotrophin extract (EGE) intravenously. Artificial insemination was performed 20 h after ovulation according to 1 of the following protocols: no dilution (n = 14): three 0.5-mL straws were thawed and the semen deposited by a flexible rod at the uterine tip in the ipsilateral horn where the pre-ovulatory follicle was detected; or dilution (n = 21): three 0.5-mL straws were thawed as described and centrifuged after addition of 1.5 mL of BotuSêmen® extender (1:1 dilution). Pregnancy rates were evaluated between treatments, age and presence of intrauterine liquid (IUL) classes and period between ovulation and AI. Data were analysed as a binomial distribution with the GENMOD procedure (SAS, Cary, NC, USA). Pregnancy rate was higher (P < 0.05) for mares inseminated with diluted semen (42.9%) compared to those inseminated with no semen dilution (4.8%). Age and IUL class did not influence pregnancy rates. It can be concluded that reduction of osmotic stress through the dilution of cryopreserved equine semen increased pregnancy rates after AI. Semen dilution, as tested in this trial, yielded good pregnancy rates in a fixed-time AI protocol in mares, simplified mare management greatly and allowed the use of a fixed-time protocol successfully. Supported by CNPQ, CAPES.

scholarly journals The effect of clitoral stimulation post artificial insemination on pregnancy rates of multiparous Bos indicus beef cows submitted to estradiol/progesterone-based estrus synchronization protocol

2020 ◽  
Vol 98 (7) ◽  
Author(s):  
Ramiro V Oliveira Filho ◽  
Reinaldo F Cooke ◽  
Gustavo A de Mello ◽  
Victor M Pereira ◽  
Jose Luiz M Vasconcelos ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Body Condition Score ◽  
Bos Indicus ◽  
Fixed Time ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Estrus Synchronization ◽  
Exit Velocity ◽  
Clitoral Stimulation

Abstract Clitoral stimulation after artificial insemination (AI) in beef cattle is a common practice utilized by AI technicians; however, the effect of clitoral stimulation during fixed-time AI (TAI) is still unknown. The objective of the present experiment was to evaluate the effect of clitoral stimulation on temperament responses and pregnancy rates to TAI in Bos indicus beef cows. A total of 1,186 multiparous Nellore cows across three different locations were assigned to an estradiol/progesterone-based estrus synchronization + TAI protocol (day −11 to 0). Cows were randomly assigned to receive either 3 s of clitoral stimulation (n = 602) or no clitoral stimulation (n = 584) immediately after TAI (day 0). Cow body condition score (BCS) was recorded on day −11. Estrus expression was evaluated based on estrus detection visual aid patch activation on day 0 (estrus, ≥50% activated; no estrus, &lt;50% activated). Temperament was assessed by individual chute score based on a 5-point scale before TAI, and individual exit velocity was measured after clitoral stimulation. Pregnancy diagnosis was performed 30 d after TAI via transrectal ultrasonography. Pregnancy rate to TAI was positively affected by BCS (P &lt; 0.01) and estrus expression (P = 0.03). Pregnancy rates of cows receiving clitoral stimulation did not differ (P = 0.39) from cows non-stimulated (47.5 ± 4.6% vs. 44.3 ± 4.6%, respectively). No interaction of clitoral stimulation and estrus expression was observed (P = 0.26). Chute score was positively correlated to exit velocity (P &lt; 0.01; r = 0.29); however, clitoral stimulation did not affect exit velocity (P = 0.86). In summary, pregnancy rates to TAI are influenced by various factors and multiple strategies have the potential to increase the fertility of beef cows submitted to TAI; however, clitoral stimulation of Bos indicus beef cows did not improve TAI pregnancy rate.

scholarly journals 27 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

2019 ◽  
Vol 97 (Supplement_1) ◽  
pp. 20-20
Author(s):  
Claire L Timlin ◽  
Laura Hungerford ◽  
Tracey Redifer ◽  
John F Currin ◽  
Vitor R G Mercadante
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Economic Feasibility ◽  
Average Ratio ◽  
Conception Rates ◽  
Virginia Department ◽  
Natural Service

Abstract This retrospective study analyzed the effect of bull:cow ratio on pregnancy rates of cows returning to estrus after enrollment in fixed-time artificial insemination (TAI). Data were compiled over the course of 6 breeding seasons between 2014 and 2017 from the Virginia Department of Corrections herd containing 15 farms and 141 groups of cows (average 44 cows/group). Multiparous cows aged 2 years and older (n = 6002) were exposed to estrus synchronization. Non-pregnant cows after TAI (n=3079, average 21 cows/group) were exposed to natural service with bulls diagnosed as fertile by a breeding soundness exam. Percent data were given an arcsine transformation. A one-way ANOVA evaluated TAI rates by season and a linear regression was performed to compare conception rates to the bull:cow ratio. Pregnancy rate to TAI among groups averaged 53% and ranged from 11% to 83%. First bull pregnancy rate of cows returning to estrus was 47% overall, with fall seasons having greater conception rates than spring (51.1% vs. 44.5%, P = 0.03). The ratio of bulls to total number of cows ranged from 1:8 to 1:68 with an average ratio of 1:28. The ratio of bulls to the number of open cows ranged from 1:2 to 1:39 with an average ratio of 1:14. There was no correlation between the bull:cow ratio and return to estrus pregnancy rate (r = -0.12), and there was no correlation between the number of open cows per bull and return to estrus conception rates (r = -0.17). Thus, higher bull:cow ratios (between 1:8 and 1:68) did not effect return to estrus pregnancy rate; producers may consider a lower number of bulls needed for natural service breeding post TAI, decreasing bull related costs and increasing the economic feasibility of adopting TAI protocols.

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