19 THE EFFECT OF FOLLICLE-STIMULATING HORMONE IN A MODIFIED CO-SYNCH SYNCHRONIZATION PROTOCOL ON SUBSEQUENT PREGNANCY RATES OF CROSSBRED LACTATING BEEF CATTLE

2013 ◽  
Vol 25 (1) ◽  
pp. 156
Author(s):  
L. R. Gentry ◽  
R. W. Walker ◽  
J. Lambe-Steinmiller ◽  
R. A. Godke ◽  
G. T. Gentry
Keyword(s):  
Treatment Group ◽  
Beef Cattle ◽  
Pregnancy Rate ◽  
Beef Cows ◽  
Subsequent Pregnancy ◽  
Pregnancy Rates ◽  
Reproductive Efficiency ◽  
Follicular Waves ◽  
Estrus Detection ◽  
Synchronization Protocol

Heritability of reproductive traits is relatively low, leaving only management strategies as an alternative to affect reproductive efficiency in beef cattle. The use of assisted reproductive technologies such as fixed-timed AI (FTAI) offers the ability to increase reproductive efficiency through selection of superior genetics and manipulation of calving dates through estrous-synchronization protocols. Application of these technologies has not been fully embraced by cattlemen due to variation in success rate, primarily associated with the apparent lack of control of follicular waves. While it has been reported that an endogenous increase in FSH precedes the emergence of follicular waves in cattle, we could find no reports on the effects of exogenous FSH on FTAI pregnancy rates. Artificial insemination remains the most important reproductive technology that could positively affect cattlemen. Therefore, this experiment was conducted to test the hypothesis that incorporation of FSH into the CO-Synch synchronization protocol would increase FTAI pregnancy rates in beef cattle. Crossbred beef cows (n = 182) with a mean body weight (BW) of 596 ± 6.6 kg and mean body condition score (BCS) of 5.4 ± 0.07 from 3 different locations were stratified across treatment groups by BW, BCS, and days postpartum or cyclicity status based on plasma progesterone concentrations. Females were estrus synchronized using the 7-day CO-Synch+CIDR protocol. All females received a CIDR insert and 100 µg of gonadotropin-releasing hormone (GnRH; Factrel) on Day 0, followed by CIDR removal, 25 mg of prostaglandin (Lutalyse) IM and fitted with an estrus-detection patch (Estrotect) on Day 7. On Day 2, all females (n = 92) in the FSH treatment group were administered 20 mg of FSH (Folltropin) IM and the remaining females (n = 90) served as nontreated controls. Fixed-timed AI was performed at 72 h following CIDR removal when all females were administered 100 µg of GnRH and the estrus-detection patch was evaluated. The overall FTAI pregnancy rate was 55% (100/182) and there was no difference (P = 0.41) in pregnancy rates across locations so the data were pooled and reanalyzed. Pregnancy rates were not affected (P = 0.54) by treatment group and were 52% (48/92) for the FSH-treated females and 58% (52/90) for the nontreated control group. Similarly, based on evaluation of the estrus-detection patch, there was no difference (P = 0.68) in the percentage of females responding to the synchronization protocol [61% (55/92) v. 68% (61/90)] and no difference (P = 0.55) in the pregnancy rate of responding females [62% (34/55) v. 69% (42/61)] for the FSH-treated and nontreated control groups, respectively. In conclusion, administration of FSH 10 days prior to FTAI in CO-Synch+CIDR synchronized crossbred beef cows did not increase subsequent pregnancy rates. However, exogenous FSH administration should be evaluated further to determine its effects, if any, on follicular dynamics related to FTAI in the lactating beef cow.

scholarly journals Calving sub-season and reproductive efficiency of beef cows

2010 ◽  
Vol 39 (10) ◽  
pp. 2182-2186
Author(s):  
Cristiane Reinher ◽  
Júlio Otávio Jardim Barcellos ◽  
Vanessa Peripolli ◽  
Ênio Rosa Prates ◽  
Maria Eugênia Andrighetto Canozzi
Keyword(s):  
Pregnancy Rate ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Reproductive Efficiency ◽  
Climate Variations ◽  
Southern Brazil ◽  
Chi Square ◽  
Chi Square Test

It was evaluated in this work the effect of calving sub-season on the pregnancy rate of 7,726 multiparous Hereford beef cows grazing on natural pastures in southern Brazil, from 1994 to 2007. Calving sub-season periods were divided in 20-day intervals from August 12th to 31st; from September 1st to 20th; from September 21st to October 10th; from October 11th to 31st; from November 1st to 20th. Calving in each sub-season and pregnancy rate (PR) were analyzed by the Chi-square test. Overall means of each sub-season were 92.7% (from August 12th to 31st), 90.6% (from September 1st to 20th), 82.1% (from September 21st to October 10th), 77.7% (from October 11th to 31st), and 70.6% (from November 1st to 20th). Calving sub-season significantly influenced pregnancy rate. Cows which calved in the initial sub-season showed higher pregnancy rates than cows which calved from the fourth calving sub-season. However this difference did not occur in 1999 and in 2007 since calving rates did not statistically differ among the five sub-seasons. In 1998 and 2004, calving rates were lower and the effects of calving sub-season on pregnancy rates were higher, possibly due to climate variations. In general, pregnancy rate decreases as calving occurs later in the year, particularly in years when the weather adversely affects pasture growth.

9 EFFECT OF TIMING OF INSEMINATION WITH SORTED SEMEN ON SUBSEQUENT PREGNANCY RATE IN POSTPARTUM BEEF COWS SYNCHRONIZED WITH A MODIFIED 14-DAY PROGESTERONE PROTOCOL

2014 ◽  
Vol 26 (1) ◽  
pp. 119
Author(s):  
A. J. Davis ◽  
J. G. Powell ◽  
T. D. Lester ◽  
R. W. Rorie
Keyword(s):  
Pregnancy Rate ◽  
Animal Health ◽  
Prostaglandin F2α ◽  
Beef Cows ◽  
Subsequent Pregnancy ◽  
Pregnancy Rates ◽  
Treatment Groups ◽  
Rate Analysis ◽  
Chi Squared ◽  
Pregnancy Status

A study investigated the effect of AI timing on pregnancy rate when using X sorted semen, and whether prostaglandin F2α (PGF2) injection on Day 7 of a modified 14-day progesterone (P4) protocol improved oestrous response in beef cows. Angus-based cows were allotted across treatment groups by cyclicity, parity, weight, body condition, and days postpartum. Treatment 1 (n = 132) cows received a CIDR P4 insert (Eazi-Breed CIDR, Pfizer Animal Health, Groton, CT, USA) on Day 0, with CIDR removal on Day 14, followed by 100 μg of gonadotropin-releasing hormone (GnRH; Factrel, Pfizer) on Day 16, and 25 mg of PGF2 (Lutalyse, Pfizer) on Day 23. Treatment 2 (n = 132) cows received the same synchronization treatment, except for an additional 25 mg dose of PGF2 given on Day 7 of CIDR treatment. Cows were observed for oestrus over an 84-h period and inseminated with X-sorted semen at 9 to 14, 15 to 17, 18 to 21 or 22 to 24 h after detected oestrus, followed 10 days later by exposure to fertile bulls for 45 days. Ultrasonography was used to determine pregnancy status ~45 days after AI and again 45 to 55 days after bull removal. Chi-squared analysis was used to determine the effects of treatment on oestrus response, AI pregnancy, and seasonal pregnancy rates, and the effect of AI timing on pregnancy rate. Analysis of variance was used to determine the effects of treatment on the interval from PGF2 dosing to detected oestrus. Oestrus response to synchronization treatment was similar (P = 0.33) at 76.5 and 71.2% for cows in Treatments 1 and 2, respectively. The mean interval from PGF2 to the onset of oestrus was extended (P = 0.03) ~3 h for cows in Treatment 2 (57.4 v. 54.3 h, respectively). About two-thirds of the cows in each treatment were cyclic at the start of synchronization. The extended interval from PGF2 to observed oestrus was due to an effect on cyclic, but not acyclic, cows in Treatment 2. Of the cows expressing oestrus, 69 and 89% expressed oestrus 48 to 72 h post-PGF2 in Treatments 1 and 2, respectively. Pregnancy rates after AI with sorted semen were similar (P = 0.64) at 63.3 and 66.7% for Treatments 1 and 2, respectively. No differences (P = 0.98) were detected in AI pregnancy rates for insemination intervals ranging from 9 to 24 h after detected oestrus. At the end of the breeding season, seasonal pregnancy rates were also similar (P = 0.74), at 83.3 and 84.9% for cows in Treatments 1 and 2, respectively. The addition of a PGF2 treatment on Day 7 of our 14-day CIDR-based protocol was expected to ensure all cows has sub-luteal P4 concentrations and would develop a persistent follicle capable of ovulation in response to GnRH given on Day 16. Whereas the Day 7 PGF2 treatment had no effect on oestrus response or pregnancy rate, it did result in a more synchronous oestrus within a 24-h period. Results indicate that acceptable pregnancy rates can be achieved in lactating beef cows when using sorted semen over a range of insemination times.

scholarly journals Fertility response of lactating dairy cows subjected to three different breeding programs under subtropical conditions

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Abdeltawab Abdelrazek Yassin Khalil
Keyword(s):  
Pregnancy Rate ◽  
Treatment Success ◽  
Pregnancy Rates ◽  
Seasonal Effect ◽  
Reproductive Efficiency ◽  
Ovarian Cysts ◽  
Breeding Programs ◽  
Efficient Treatment ◽  
Release Device ◽  
Synchronization Protocol

Abstract Background It is comprehensively recognized that reduced reproductive efficiency represents a great economic loss to dairy producers. Ovarian cysts and anestrus syndromes are considered the greatest significant causes of low reproductive efficiency in dairy herds worldwide as they detrimentally affect the longevity and profitability of dairy herd. Pregnancy rate is the best available single deciding parameter used for assessment of the reproductive efficiency at the herd level which measures the probability that open cows become pregnant per unit of time. So, the current study was planned to evaluate the suitability of using Ovsynch plus CIDR and G6G resynchronization protocols as an efficient treatment regimen for cystic ovarian diseased cows and anestrus cows, respectively, through comparing pregnancy rates of cystic ovarian diseased cows that subjected to Ovsynch supplemented with controlled internal drug release device with the pregnancy rate of healthy cows that subjected to a Presynch-Ovsynch synchronization protocol, as well as through comparing pregnancy rates of anestrus cows that subjected to G6G treatment protocol with the pregnancy rate of healthy cows. Moreover, possible factors such as breed, parity, and season which may affect the treatment success were also evaluated. Results The results of the current study revealed an overall mean pregnancy rate of 36.64%. Moreover, Simmental cows recorded a greater (p < 0.01) pregnancy rate (45.16%) than that recorded for Holstein cows (34.98%). A highly significant seasonal effect was observed, as a higher (p < 0.01) pregnancy rate was recorded for cows inseminated during cold months (39.54%) compared with that recorded for cows inseminated during hot months (29.18%). Conclusions No significant differences were detected in the pregnancy rates among the three breeding programs; thence, the application of the G6G synchronization protocol for anestrus cows and Ovsynch-CIDR synchronization protocol for cows with ovarian cysts could be used as effective treatment regimens as they resulted in nearly the same pregnancy rates that recorded for healthy cows. In addition, the treatment response was highly influenced by cow’s breed, parity, and season of breeding.

11 CALF REMOVAL IMPROVES CO-SYNCH + CONTROLLED INTERNAL DRUG-RELEASE PREGNANCY RATES IN BEEF COWS

2009 ◽  
Vol 21 (1) ◽  
pp. 105 ◽  
Author(s):  
D. J. Kesler ◽  
D. B. Faulkner ◽  
F. A. Ireland ◽  
J. Dahlquist ◽  
S. Z. El-Zarkouny ◽  
...  
Keyword(s):  
Treatment Group ◽  
Pregnancy Rate ◽  
Estrous Cycle ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Control Treatment ◽  
Control Group ◽  
Research Station ◽  
Treatment Groups ◽  
Calf Removal

Improving AI pregnancy rates in beef cattle will enhance the profitability of beef herds during these current times of increasing cost inputs by enhancing the quality of the calf crop. This experiment was aimed at determining the effect of calf removal (from CIDR removal to timed AI) during estrous cycle synchronization on AI pregnancy rates. This experiment was conduced at the Dixon Springs Research Station (Simpson, IL) during the fall 2007 breeding season. The beef cows used for this research project were crossbred Angus cows between 2 and 8 years of age that had calved in August to October of 2007. Cows were at least 45 days postpartum at the timed AI (November 2007). All cows were randomly divided into 1 of 2 treatment groups: cows in treatment group 1 (control group, n = 284) were allowed to keep their calves for the entire estrous cycle synchronization and AI program (except during brief times of treatment administration), whereas cows allotted to treatment group 2 (n = 258) had their calves removed at the time of CIDR implant removal/PGF2α treatment and returned following AI. The calves were maintained on creep feed out of sight and sound of their dams. All cows were synchronized by using the CO-Synch + CIDR protocol [CIDR (1.38 g) + GnRH (100 μg) on Day 0 and CIDR removal on Day 7 + PGF2α (25 mg)] and were inseminated at a predetermined time of 60 to 66 h post PGF2α with semen from proven bulls. At AI, cows also received an injection of GnRH (100 μg). All cows were pregnancy checked 50 to 65 days after timed AI via ultrasonography. Statistical comparisons were performed by using the chi-square test of SAS. The pregnancy rate for cows in the control treatment group was 47% (132 of 284) and was 57% (147 of 258) for the calf-removal treatment group. There was a significant increase in pregnancy rate in the treatment group (P < 0.02) that resulted in 10 more calves per 100 synchronized AI breedings. Although excellent facilities are needed to maintain calves away from their dams during this 60 to 66 h and there are additional costs for the feedings required for the calves, there is a savings in time (one calf separation from the cow is eliminated). In conclusion, removing the calves at the onset of estrous cycle synchronization can improve pregnancy rates to synchronized timed AI and can increase the ease of cattle handling during this process by reducing the number of calf removals during routine cow workings. Table 1.Pregnancy rates to single synchronized timed AI for control and calf removal treatment groups

scholarly journals 218 Effect of GnRH injection at -72 h in MGA-PG estrus synchronization protocol

2019 ◽  
Vol 97 (Supplement_2) ◽  
pp. 122-122
Author(s):  
McKay Erickson ◽  
Rick N Funston
Keyword(s):  
Pregnancy Rate ◽  
Prostaglandin F2α ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Estrus Synchronization ◽  
Estrus Detection ◽  
To Receive ◽  
Observation Period ◽  
Synchronization Protocol

Abstract Beef heifers (n = 1524) from two operations in central Nebraska were randomly assigned to one of two treatments [0 or 5 μg GnRH at prostaglandin F2α (PGF) administration 72 hrs before insemination]. Both locations utilized MGA-PG fixed-time AI (TAI) estrus synchronization protocol. The first location (L1, n = 1076, 382 ± 3 kg) processed heifers 72 hours prior to insemination and every third heifer was assigned to receive an injection of GnRH (5 ug) (TRT) and an injection of PGF. The remaining heifers received PGF and 0 μg GnRH. At insemination all heifers received 100 ug GnRH. Heifers were then observed for estrus behavior from 10–21 days post TAI and re-inseminated if estrus was detected. Heifers pregnant from the second breeding were added to final pregnancy rate. The second location (L2) utilized estrus detection patches and performed only TAI (n = 448, 363 ± 7 kg) following MGA-PG synchronization protocol outlined above without the estrus observation period. Treatment did not significantly (P > 0.20) improve TAI pregnancy rates [L1 TAI 56.3% (TRT) vs 57.3%; L1 AI Total 78.3% (TRT) vs 73.9%; L2 TAI 58.5% (TRT) vs 52.5%] among the two herds. The administration of 5 μg GnRH at PGF tended to increase (P = 0.12, 74% vs 63%) pregnancy rates for those inseminated during the follow up heat detection period at L1. The treatment did not (P > 0.20) improve pregnancy for the time-AI heifers. In addition, TAI pregnancy rates were similar (P > 0.20) at L2. There were greater (P < 0.20) effect of pen on pregnancy rate.

scholarly journals 142 Evaluation of estrus detection patches as a tool to classify postpartum beef cows as estrous cycling or anestrous prior to the start of the breeding season

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 116-117
Author(s):  
Emily G Smith ◽  
Rachael C Bonacker ◽  
Carson M Andersen ◽  
Jordan M Thomas
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Beef Cows ◽  
Estrus Synchronization ◽  
Serum Progesterone ◽  
Estrus Detection ◽  
Estrous Cyclicity ◽  
Type Ii Errors ◽  
Estrous Cycling

Abstract Estrus detection patches were evaluated as a tool to classify postpartum cows as estrous cycling or anestrous at the start of the breeding season. EstrotectTM Breeding Indicators were applied to 257 postpartum beef cows in three locations 25 days prior to the start of estrus synchronization. Coincident with the start of estrus synchronization, patches were scored using a 1 to 4 scale (1 = 0–25%; 2 = 25–50%; 3 = 50–75%; 4 = 75–100%) with scores of 3 or 4 considered activated. Blood samples were collected from each cow 10 days prior to, and at the start of the estrus synchronization. Serum progesterone concentrations were determined via radioimmunoassay; cows were considered estrous cycling if one or both samples exceeded a concentration of 0.5 ng/ml. Based on progesterone, 54.9% of cows were estrous cycling at the start of estrus synchronization. When missing patches were considered inconclusive results, use of patches to infer estrous cyclicity resulted in 85.0% sensitivity and 79.2% specificity with a positive predictive value of 87.2%. However, 75.1% of all cows presented with missing patches at the start of synchronization. If missing patches were considered activated, sensitivity was 95.7%, but specificity (16.4%) and PPV (58.2%) were poor, as 47.6% of cows presenting with missing patches were anestrous based on progesterone. Across all cows, pregnancy rate to AI was 58.0% (149/257). Cows with activated patches that were classified as false positives based on serum progesterone concentrations achieved a 71.4% (5/7) pregnancy rate to AI, raising questions as to whether sensitivity was underestimated due to inherent Type II errors in classification of cyclicity via progesterone. In summary, estrus detection aids are a sensitive tool to identify estrous cycling postpartum cows prior to the start of the breeding season; however, poor specificity and patch retention are limitations for this application.

Response of beef heifers and non-suckling beef cows to different oestrous synchronization protocols

2002 ◽  
Vol 74 (3) ◽  
pp. 547-552 ◽  
Author(s):  
D. Cavestany ◽  
N. Negrin ◽  
R. Negrin ◽  
J. F. Groth
Keyword(s):  
Beef Cattle ◽  
Medroxyprogesterone Acetate ◽  
Artificial Insemination ◽  
Experimental Period ◽  
Fixed Time ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Gnrh Analogue ◽  
Beef Heifers

AbstractThe objective was to evaluate different oestrous synchronization schemes in beef cattle under range conditions. In experiment 1, 202 heifers averaging 26 months of age were assigned randomly to three treatments: (a) GnRH-PG. (no. = 44) day 0 (D0): injection of GnRH; D7: injection of PGF2α; D0 to D25 oestrous detection (OD) and artificial insemination (AI); (b) OD-PG. (no. = 45) D0 to D4; OD + AI; D5: injection of PGF2α; D5 to D25 OD + AI; and (c)Ovsynch. (no. = 113) D0: injection of GnRH; D7: injection of PGF2α; D9: injection of GnRH and 16 h later AI at fixed time. In experiment 2, 318 non-suckling cows were assigned randomly to three treatments: (a) GnRH-PG. (no. = 106) D0: injection of GnRH; D7: injection of PGF2α; D0 to D25 OD + AI; (b) GnRH-MAP-PG. (no. = 106) D0: injection of a GnRH analogue and insertion of an intravaginal sponge impregnated with 250 mg of medroxyprogesterone acetate; D7: injection of PGF2α and sponge withdrawal; D0 to D25 OD + AI; (c) controls. (no. = 106) OD and AI. The experimental period lasted 25 days and, with exception of the Ovsynch treatment, oestrous detection was carried out twice a day (a.m./p.m.) and inseminations performed 12 h later. The pregnancy rates assessed by ultrasonography 30 days after AI were: experiment 1: (a) 30·0%; (b) 28·6% and (c) 62·3% (P < 0·05); experiment 2: (a) 60·2%; (b) 57·8% and (c) 45·5% (P < 0·05). It is concluded that in heifers and non-suckling cows, oestrous synchronization treatments result in higher pregnancy rates. In non-suckling cows, the addition of a progestagen did not improve the response.

Cooled semen for fixed-time artificial insemination in beef cattle

2016 ◽  
Vol 28 (7) ◽  
pp. 1004 ◽  
Author(s):  
Juliana C. Borges-Silva ◽  
Márcio R. Silva ◽  
Daniel B. Marinho ◽  
Eriklis Nogueira ◽  
Deiler C. Sampaio ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Sperm Motility ◽  
Artificial Insemination ◽  
Egg Yolk ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Reproductive Efficiency ◽  
Sperm Abnormalities ◽  
Hypoosmotic Swelling Test ◽  
Interesting Approach

This study evaluated the use of cooled semen in a fixed-time artificial insemination (FTAI) program compared with frozen–thawed semen to improve pregnancy rates in beef cattle. Ejaculates of three bulls were collected and divided into two treatments: (1) frozen–thawed semen and (2) cooled semen. Egg-yolk extender without glycerol was used for the cooled semen treatment. Straws (25 × 106 spermatozoa) were submitted to cooling for preservation at 5°C for 24 h, after which FTAI was performed. Nelore cows (n = 838) submitted to FTAI were randomly inseminated using frozen–thawed semen or cooled semen. There was a 20% increase in the pregnancy per AI (P AI–1) using cooled semen compared with frozen–thawed semen (59.9 ± 4.7 vs 49.4 ± 5.0%; P < 0.005). There was no difference in P AI–1 among the bulls (P = 0.40). The frozen–thawed semen had fewer functional spermatozoa than did the cooled semen when evaluated by sperm motility (61.7 vs 81.0%), slow thermoresistance test (41.7 vs 66.7%) and hypoosmotic swelling test (38.3 vs 53.7%; P < 0.05). The percentage of sperm abnormalities did not differ between the freeze–thawing and cooling processes (18.6 vs 22.1%; P > 0.05). Because there was less damage to spermatozoa and improvement in P AI–1, the use of cooled semen instead of frozen–thawed semen is an interesting approach to increase reproductive efficiency in cattle submitted to a FTAI protocol.

10 INFLUENCE OF ADMINISTRATION OF HUMAN CHORIONIC GONADOTROPIN ON DAY 4 AFTER FIXED-TIME AI ON CORPUS LUTEUM SIZE, FUNCTION, AND PREGNANCY RATE IN BEEF COWS

2014 ◽  
Vol 26 (1) ◽  
pp. 119
Author(s):  
J. B. S. Borges ◽  
D. X. Thedy
Keyword(s):  
Corpus Luteum ◽  
Pregnancy Rate ◽  
Fixed Time ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Control Group ◽  
Chi Square ◽  
Prostaglandin F2a ◽  
Successful Establishment ◽  
Early Rise

Successful establishment of pregnancy in the cow depends on early rise of progesterone (P4) to improve embryo development. The present study was carried out to determine the corpus luteum (CL) function and pregnancy rate following the administration of 1.500 IU of hCG in suckled beef cows on Day 4 after fixed-time AI (FTAI). Crossbred Angus cows (n = 429), 40 to 70 days postpartum, were synchronized using 2 mg of oestradiol benzoate (EB) i.m. and an intravaginal progesterone-releasing device containing 1 g of P4 for 7 days. At device removal, prostaglandin F2a (150 mg of D-cloprostenol) was injected i.m.; 24 h later, 1 mg of EB was given and the FTAI were done 30 to 36 h after EB using semen of just 1 bull. Cows were assigned alternatively to receive 1.500 IU of hCG i.m. (n = 200) or 1 mL of saline i.m. (n = 229) on Day 4 after FTAI. Ovaries were examined by transrectal ultrasonography (n = 71) on Days 4 and 7 to detect the presence and to measure the area of CL. Blood samples were collected on Days 4, 7, 10, 14, and 30 post-oestrus to determine P4 concentration by RIA. Pregnancy diagnoses were done 30 days after FTAI. The effects of treatments on CL area and serum P4 levels were analysed by ANOVA (Proc GLM, SAS Institute Inc., Cary, NC, USA) and pregnancy rates compared by chi-square (Proc CATMOT, SAS). The induction of accessory CL determined on Day 7 was 44% in cows treated with hCG and not observed in the control group. The area of the CL on Day 7 was significantly higher (P < 0.01; 3.37 ± 2.56 v. 2.56 ± 0.22 cm2) in the hCG group. Despite the increase in CL size, the mean levels of P4 on Days 4, 7, 10, 14, and 30 post-AI indicated no difference (P > 0.05) in CL function between control and hCG-treated cows. On Day 30, pregnancy rates were not different (P = 0.08), at 46.7 and 55% for control and hCG-treated cows, respectively. In conclusion, administration of 1.500 IU of hCG on Day 4 post-FTAI did not improve pregnancy rate in suckled beef cows.

116 PREGNANCY RATES AFTER ADMINISTRATION OF EQUINE CHORIONIC GONADOTROPIN (eCG) AT PROGESTERONE INTRAVAGINAL DEVICE REMOVAL AND 14 DAYS AFTER FIXED-TIME AI IN BEEF CATTLE

2011 ◽  
Vol 23 (1) ◽  
pp. 163 ◽  
Author(s):  
R. Núñez ◽  
T. de Castro ◽  
L. Cutaia ◽  
G. Bó ◽  
A. Menchaca
Keyword(s):  
Beef Cattle ◽  
Pregnancy Rate ◽  
Body Condition Score ◽  
Fetal Loss ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Control Group ◽  
Device Removal ◽  
Embryo Survival ◽  
Intravaginal Device

An important proportion of embryonic deaths in cattle occur during the critical period of embryo development and maternal recognition of pregnancy. High serum progesterone concentrations during this period are associated to higher embryo survival, and the use of eCG could enhance luteal activity. Two experiments were carried out to evaluate the effect of administering eCG at the time of removal of a progesterone-releasing device and 14 days after fixed-time artificial insemination (FTAI) in beef cattle. Multiparous suckled cows between 60 and 90 days postpartum (n = 297; Exp. 1), and two-year old prepuberal heifers (n = 689; Exp. 2) with a body condition score (BCS) between 3.5 and 5 (1 to 8 scale) were used. At the beginning of the experiments, none of females used had a corpus luteum detected by ultrasonography. Females received an intravaginal device containing 0.5 g progesterone (DIB 0.5, Syntex, Buenos Aires, Argentina) and 2 mg oestradiol benzoate i.m. (Benzoato de Oestradiol, Syntex). Eight days later, 500 μg of cloprostenol (Ciclase DL, Syntex) and 0.5 mg oestradiol cypionate (Cipiosyn, Syntex) were given i.m. and devices were removed; FTAI was performed 52 to 56 h after DIB removal. At the time of device removal, the animals were randomly allocated to 4 groups, to receive 400 IU of eCG i.m. (Novormon, Syntex) or placebo at device removal and/or 14 days after FTAI, in a 2 × 2 factorial design. Control group did not receive eCG. In Exp. 1, nose plates were placed on calves on the day of DIB insertion and left for 10 days in order to prevent suckling. Pregnancy diagnosis was performed by ultrasonography at 30 and 60 days after FTAI. Data were analysed by logistic regression. Pregnancy rate at 30 days after FTAI was affected by treatment (P < 0.05; Table 1). Late embryonic/fetal loss rates (non-pregnant females at 60 days after FTAI over those pregnant at 30 days) were 1.6% (3/182) for cows in Exp. 1 and 4.8% (14/292) for heifers in Exp. 2; no differences were detected among groups. In conclusion, administration of 400 IU of eCG at device removal increases pregnancy rate, both in anestrus cows and heifers. However, the administration of a second dose of eCG 14 days after FTAI suggests a possible effect on embryo survival within the first 30 days of pregnancy in cows but not in heifers. Further studies are required to confirm these results. Table 1.Pregnancy rates after administration of eCG at time of progesterone device removal and/or 14 days after insemination in beef cattle Supported by Syntex.

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