The influence of transfer gun passage time through the uterine cervix on pregnancy rate in recipient heifers

2010 ◽  
Vol 58 (1) ◽  
pp. 125-132 ◽  
Author(s):  
Jędrzej Jaśkowski ◽  
Krzysztof Urbaniak ◽  
Paweł Antosik ◽  
Renata Włodarczyk
Keyword(s):  
Stainless Steel ◽  
Pregnancy Rate ◽  
Uterine Cervix ◽  
Insertion Site ◽  
Passage Time ◽  
Uterine Horn ◽  
Conception Rate ◽  
Experienced Operator ◽  
Metal Tip ◽  
Stage 1

The influence of passage time of the transfer gun through the uterine cervix and body to the embryo insertion site on pregnancy rate was analysed in 248 recipient heifers (mean age: 15–17 months). Embryos (90 fresh and/or 88 and 70 frozen in glycerol and ethylene glycol, respectively, grades 4 and 5, stage 1 or 2) were transferred to the ipsilateral uterine horn on day 7. Two different transfer guns were used in this experiment: a sterilisable steel transfer instrument to be used without sheaths with a removable tip made of gold-plated stainless steel (Wörrlein Minitüb) or a transfer stylet with sheaths with a metal tip and a side opening (Cassou gun, IMV Technologies). The time of passage of the instruments through the uterine cervix and body to the site of embryo deposition in the uterine horn was measured in the study. In order to randomise the risk of errors, all manipulations were carried out by the same experienced operator. The average time needed for the insertion of embryos into the uterus was 50.6 seconds (s) and it was longer for the transfer gun with sheaths than for the metal-tipped transfer gun (60.1 and 40.8 s, respectively) (P < 0.001). The average conception rate was 45.6%. If the time needed to insert embryos into the uterus was 10-60 s, the conception rate was 53.4% (up to 20, 21–30, 31–40, 41–50 and 51–60 s − 57.7, 52.5, 50, 51.5 and 50%, respectively). In contrast, if the time needed to insert the embryo in the uterine horn was longer than 60 s, the conception rate was 20.4% (61–80, 80.1–120 and > 120 s − 28.0, 6.0 and 24.9%, respectively). Thus, it cannot be excluded that the type of the applied transfer gun may influence pregnancy rate in recipient cows due to its effect on cervical passage time.

scholarly journals Fertility parameters in German dairy herds: Associations with milk yield and herd size

2019 ◽  
Vol 64 (No. 11) ◽  
pp. 459-464
Author(s):  
Jörn Rethmeier ◽  
Michael Wenzlau ◽  
Martin Wagner ◽  
Steffi Wiedemann ◽  
Lisa Bachmann
Keyword(s):  
Pregnancy Rate ◽  
Milk Yield ◽  
Reproductive Performance ◽  
Dairy Farms ◽  
Herd Size ◽  
Pregnancy Rates ◽  
Conception Rate ◽  
Service Rate ◽  
Dairy Herds ◽  
Key Factor

Fertility in dairy cows has decreased over the last fifty years while milk production per cow has increased. Furthermore, dairy herds become larger resulting in fewer employees per cow, which might also influence reproductive performance. To elucidate the situation in Germany, selected parameters (conception rate, service rate, pregnancy rate, days to first insemination and days open) were studied using data on 148 herds. For statistical analysis the herds were categorized concerning milk yield: (1) &lt; 30 kg, (2) 30‒35 kg, and (3) &gt; 35 kg/cow/day as well as concerning herd size: (1) &lt; 200, (2) 200‒400, (3) 400‒1000 and (4) &gt; 1000 milking cows. There was no difference in conception rate among herds. That means on dairy farms of larger size or with high milk yield the chance of an inseminated cow to become pregnant is the same as in small herds or in herds with low milk yield. Small herds (&lt; 200 cows) had lower pregnancy rates than larger herds (200–400 cows). The pregnancy rate in herds with different milk yield was not statistically different. Though there was a trend that dairy farms with higher milk yield (&gt; 30 kg) had higher pregnancy rates. The statistical differences and trends of pregnancy rates are due to higher service rate in larger herds as well as in herds with high milk yield. Therefore, service rate is the key factor for high reproductive performance on dairy farms. Poor fertility is not associated with high milk yield on herd basis or large herd size but may represent inappropriate farm management.

scholarly journals Embryo recovery from the oviduct in superovulated ewes: a method to improve MOET systems

2008 ◽  
Vol 53 (No. 4) ◽  
pp. 145-151
Author(s):  
J.P. Ramon-Ugalde ◽  
J. Folch ◽  
M.J. Cocero ◽  
R.E. Piña-Aguilar ◽  
J.L. Alabart
Keyword(s):  
Recovery Rate ◽  
Uterine Horn ◽  
Conception Rate ◽  
The Other ◽  
Embryo Recovery ◽  
Intramuscular Injections ◽  
Other Hand

The efficiency of embryo recovery in a superovulatory treatment was studied by perfusing the oviduct or the uterine horn in 3.5 and 7 days after sponge withdrawal, respectively. Eighty-four and seventy ewes of Aragonesa breed were used as embryo donors and receptors, respectively. The donors were distributed in 3 replications. The oestrus was synchronized with the insertion of FGA intravaginal sponges (30 mg) for 13 days. Six intramuscular injections of 18 mg pFSH were applied in decreasing doses at 12 hour intervals starting 48 hours after sponge withdrawal. The recovery rate (RR) (83.2 vs. 75.8%), the viability rate (VR) (73.5 vs. 47.2%) and the number of viable embryos (VE) per donor ewe (5.9 ± 0.79 vs. 3.0 ± 0.37) were higher (<I>P</I> < 0.01) in ewes whose perfusion was done directly in oviducts. The interval from sponge withdrawal to oestrus had no influence on RR in any groups; however it had an effect on the VR in 3.5 and 7 days old embryos. Embryos from ewes showing the oestrus within 20 hours after sponge withdrawal had a higher viability. On the other hand, using morphologic criteria, 26.5% and 52.7% of 3.5 and 7 days old embryos, respectively, were discarded before transfer. The percentage of ewes in each group that became pregnant was similar in both groups. We conclude that in superovulated ewes the embryo recovery rate, viability and number of viable embryos are higher in embryos recovered from the oviduct compared to those recovered from the uterus, without decreasing the conception rate and the viability rate is higher in ewes that show the oestrus 20 hours before sponge withdrawal.

scholarly journals Study on the effect of insemination time on pregnancy rate of Bangladeshi buffalo in intensive farming

2019 ◽  
Vol 16 (2) ◽  
pp. 143-152
Author(s):  
MA Hamid
Keyword(s):  
Pregnancy Rate ◽  
Artificial Insemination ◽  
Conception Rate ◽  
Transrectal Ultrasonography ◽  
Livestock Breeding ◽  
Intensive Farming ◽  
Rectal Palpation

The study was designed to evaluate the insemination time and pregnancy rate of Bangladeshi buffalo at Lal Teer Livestock Breeding and Research Farm, Bhaluka, Mymensingh, Bangladesh during January 2017 to June 2018. A total of 30 cyclic buffaloes were included in this study. The animals were inseminated under four different times, i.e. inseminated i) between 0-6 hours after seeing first sign of estrous, ii) between 6-12 hours after seeing first sign of estrous, iii) between 12-18 hours after seeing first sign of estrous and v) between 18-24 hours after seeing first sign of estrous. The pregnancies (positive or negative) were confirmed by rectal palpation and transrectal ultrasonography after 60 days of artificial insemination (AI). The total pregnant animals in this study were 40%. The highest pregnancy rate (60%) was observed in insemination between 12-18 hours after seeing first sign of estrous and the lowest pregnancy rate (0%) was observed in insemination between 0-6 hours after seeing first sign of estrous. The findings of the study suggest that, the conception rate of buffalo depend on the time of AI, detection of proper estrus symptoms and site of semen deposition. SAARC J. Agri., 16(2): 143-152 (2018)

scholarly journals RELATIONSHIP OF ELECTRICAL RESISTANCE OF VAGINAL MUCUS DURING OESTRUS WITH POST-AI PREGNANCY IN COWS

2018 ◽  
Vol 15 (2) ◽  
pp. 113-117 ◽  
Author(s):  
M. Ahmed ◽  
M. K. Chowdhury ◽  
M. M. Rahman ◽  
J. Bhattacharjee ◽  
M. M. U. Bhuiyan
Keyword(s):  
Pregnancy Rate ◽  
Electrical Resistance ◽  
Genital Tract ◽  
Conception Rate ◽  
Heat Detector ◽  
The Mean ◽  
The Difference ◽  
Rectal Palpation ◽  
Relationship Of ◽  
In Pregnancy

Accurate detection of oestrus is a common problem for farmers to do AI timely resulting in conception failure in cows. The objective of the present study was to know the electrical resistance of vaginal mucus (ERVM) during oestrus to determine the best time of AI for improvement of conception in cattle. A total of 28 cows were inseminated with frozen thawed semen after detection of ERVM with Draminski estrus detector at Kendua Upazila Livestock Office under Netrakona district of Bangladesh. Pregnancy was diagnosed by per rectal palpation of genital tract 8-10 weeks after insemination. The mean ERVM in pregnant cows was 208.5 ± 31.2 Ω (163.3 to 263.3 Ω) and the ERVM in non-pregnant cows was 214.4 ± 36.6 Ω (153.3 to 280.0 Ω). Moreover, the pregnancy rate was higher in cows (80.0 to 83.3%) when ERVM during oestrus varied from 150 to 220 Ω than that of 221 to 280 Ω counterpart (36.4%). The difference in pregnancy rates between groups was significant (P<0.05). The present study indicates that Dramniski electrical heat detector may be used for prediction of time for AI in cows of Bangladesh. Up to 220 Ω ERVM during oestrus is better for higher conception rate than that of more than 220 Ω counterparts. Further studies with high number of inseminated cows should be conducted before wide application of this electrical heat detector under field conditions in Bangladesh.

Effect of zeranol implants on age at onset of puberty, fertility and embryo fetal mortality in beef heifers

1995 ◽  
Vol 75 (2) ◽  
pp. 225-230 ◽  
Author(s):  
B. D. King ◽  
R. N. Kirkwood ◽  
R. D. H. Cohen ◽  
G. A. Bo ◽  
C. Lulai ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Breeding Season ◽  
Pregnancy Loss ◽  
Age At Onset ◽  
Uterine Horn ◽  
Fetal Mortality ◽  
Diagnostic Ultrasonography ◽  
Beef Heifer ◽  
The Right ◽  
And Control

Thirty-three cross-bred beef heifer calves were implanted with zeranol (36 mg) at birth, 100 and 300 d of age and 40 heifer calves remained as untreated controls. Heifers were examined rectally by diagnostic ultrasonography every 14 d from 10 to 14 mo of age and then, every 21 d until the end of test (100 d after exposure to bulls). The presence of a CL, diameter of the largest follicle, total number of follicles ≥ 3 mm, diameter of the right uterine horn and age at puberty were recorded. At 15 mo heifers were exposed to bulls for 63 d. Mean (± SEM) age at onset of puberty in zeranol-implanted heifers (420 ± 8.9 d) was greater than control heifers (362 ± 6.2 d; P < 0.05). The diameter of the largest follicle was smaller (P < 0.05) in pre-pubertal zeranol-implanted heiferes than in pre-pubertal control heifers between 10 and 14 mo of age and at puberty. Within the zeranol-implanted heifers, the diameter of the largest follicle was smaller in pre-pubertal (P < 0.05) than pubertal heifers until 14 mo of age. The uterine diameter of zeranol-implaned heifers was smaller (P < 0.05) than that of control heifers during all examinations prior to breeding. Pubertal heifers had a larger (P < 0.05) uterine diameter than pre-pubertal heifers. Pregnancy rate after the first 21-d period of the breeding season and at the end of test was higher (P < 0.001) for control than for zeranol-implanted heifers (82.5 and 100%, respectively and 24 and 42.5%, respectively). Pregnancy loss in zeranol-implanted heifers was 37.5% compared with 0% for control heifers (P < 0.001). Heifers that became pregnant during the first 21 d of the breeding season had reached puberty earlier (396.9 ± 12.5 and 358.7 ± 6.4 d of age for zeranol-implanted and control heifers, respectively) than heifers not conceiving in the first 21 d (472.8 ± 10.8 d and 380.0 ± 17.7 d for zeranol-implanted and control heifers, respectively; P < 0.05). Heifers that became pregnant during the first 21 d of the breeding season had a larger (P < 0.001) uterine diameter (18.17 ± 0.21 mm) than non-pregnant heifers (16.28 ± 0.36 mm). Within the zeranol-implanted group, pregnant heifers had a larger (P < 0.05) uterine diameter (17.75 ± 0.05 mm) than non-pregnant heifers (15.78 ± 0.38 mm). Heifers that were not pregnant at the end of test began cycling later and had a numerically smaller uterine diameter than pregnant heifers (430 ± 17.5 d vs. 374.7 ± 6.2 d; and 15.1 ± 0.6 mm vs. 17.3 ± 0.24 mm, respectively), however these differences were not significant (P > 0.05). It was concluded that zeranol implants from birth delay the onset of puberty and decrease uterine horn diameter. Futhermore, the lower pregnancy rate in zeranol-implanted heiferes 100 d after exposure to bulls was caused by failure to cycle early in life, and in those that were cycling, failure to conceive and abortions between 25 and 45 d of gestation. Key words: Zeranol, bovine, puberty, fertility, uterine diameter, ultrasonography

113 EFFECT OF SOME FACTORS ON CONCEPTION RATE IN ALPACAS UNDER PERUVIAN HIGHLAND CONDITION

2011 ◽  
Vol 23 (1) ◽  
pp. 161
Author(s):  
A. Diaz ◽  
W. Huanca ◽  
A. Ampuero ◽  
H. Huaman ◽  
J. Camacho ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Fibre Production ◽  
Conception Rate ◽  
South American ◽  
Exact Test ◽  
Domestic Species ◽  
South American Camelids ◽  
Conception Rates ◽  
Service Conception ◽  
Mating Time

Alpacas are a domestic species of South American camelids with a great importance to highland people because of their high-quality fibre production. However, their reproductive performance has been reported to be poor, with a birth rate of 50% under the Andean community’s conditions. Two experiments were designed to evaluate the effect of some factors on the pregnancy rate of alpacas at first service in lactating, 3- to 8-years old, without parity problems. The objective of the first experiment (n = 85) was to evaluate the effect of age (G1: 3, G2: 4 to 5, G3: ≥ 6 years old); mating time (G1: 15 min, G2: 16–24 min, G3: ≥ 25 min), and interval from parturition to mating (G1: 20 days, G2: ≥ 20 days) on first service conception rate. A second experiment (n = 174) evaluated the effect of month of calving (January, February, or March) on conception rate in females with a postpartum interval ≥20 days. Animals were mated with male of good fertility after a receptivity test and confirmation of presence of a dominant follicle ≥7 mm by ultrasonography. Pregnancy was determined by ultrasonography 25 days after mating. Proportional data were compared by Fisher’s exact test. In the first experiment, conception rates were 57.9, 66.7, and 47.2% in females of G1, G2, and G3, respectively (P ≤ 0.05); 50.0, 54.5, and 59.0% in females with mating time of 15, 16–24, or ≥ 25 min of mating; 48.0 and 59.4% in those with a postpartum interval <20 days and ≥20 days (P ≤ 0.05). In the second experiment, conception rates were 58.3, 70.7, and 82.1% in alpacas calving in January, February, and March, respectively (P ≤ 0.05). The results suggest that age of female, postpartum interval, and month of calving are factors that affect conception rates in alpacas. Therefore, a reproductive management system that includes these factors would improve the pregnancy rate in alpacas under highland Peruvian conditions. Consejo Superior de Investigacion – UNMSM.

150 EXAMINATION OF ESTRUS SYNCHRONIZATION USING A PRID® + PROSTAGLANDIN F2α AND PREGNANCY RATE AFTER ARTIFICIAL INSEMINATION FOLLOWING TRANSFER OF IN VITRO-PRODUCED EMBRYOS IN REPEAT-BREEDING COWS

2008 ◽  
Vol 20 (1) ◽  
pp. 155
Author(s):  
M. Urakawa ◽  
A. Ideta ◽  
K. Hayama ◽  
K. Tsuchiya ◽  
Y. Aoyagi
Keyword(s):  
Pregnancy Rate ◽  
Rate Control ◽  
Prostaglandin F2α ◽  
Estradiol Benzoate ◽  
Pregnancy Rates ◽  
Uterine Horn ◽  
Estrus Synchronization ◽  
Significant Difference ◽  
Clinical Disorders

Repeat-breeding Holstein cows (RBCs), i.e. cows that have undergone three or more AIs, have reduced pregnancy rates. The present study aimed to determine whether application of a combination of a PRID� (ASKA Pharmaceutical Co., Inc., Tokyo, Japan) + prostaglandin F2α (PGF2α) for estrus synchronization and AI + embryo transfer (ET) would improve pregnancy rates in RBCs. All RBCs selected showed a normal interval between the previous insemination and estrus, and were free of clinical disorders. The RBCs (n = 107) received a PRID for 9 days with a capsule containing 10 mg of estradiol benzoate, 0.5 mg IM of cloprostenol (PGF2α, Resipron�-C; ASKA, Japan) at 2 days before PRID removal. The cows were inseminated with frozen–thawed semen from a bull at 0 to 12 h after onset of estrus. Seven days after AI, single in vitro-produced embryos were transferred to the same RBCs. Pregnancy was diagnosed by palpation per rectum at e60 days post-insemination. Exp. 1 estimated the response to estrus synchronization treatment (n = 107). The factors examined were lactation number (mean � SD: 2.3 � 1.5, range: 1–6), insemination number (5.2 � 2.2, range: 3–13), and the interval from calving to next AI (275.9 � 97.6 days, range: 93–650 days). Exp. 2 compared the pregnancy rate in control RBCs (n = 161) and PRID-treated RBCs (n = 100). The factors examined included lactation number (2.5 � 1.6, range: 1–12), insemination number (6.0 � 2.5, range: 3–19), the interval from calving to next AI (288.0 � 102.1 days, range: 102–797 days), and whether the ET was into the uterine horn ipsilateral or contralateral to the CL in a total of 261 RBCs. Data were analyzed using logistic regression. The results for Exp. 1: 103 cows (96.3%) were confirmed to be in estrus (2.0 � 0.3 days after PRID removal). Although the frequency of estrus was affected by the lactation number (P = 0.014) and the interval from calving to the first AI (P = 0.005), the AI number did not have an affect (P = 0.624). Exp. 2: PRID synchronization had no effect on pregnancy rate (control: 37.3%, 60/161; and PRID-treated: 40.0%, 40/100). For the RBCs, the pregnancy rate was not affected by lactation number (P = 0.093), AI number (P = 0.694), or the interval from calving to next AI (P = 0.762). No significant difference (P = 0.428) in pregnancy rate was observed in cows when the embryos were transferred into the uterine horn contralateral to the CL (43.5%, 20/46), compared to those embryos transferred into the uterus horn ipsilateral to the CL (37.2%, 80/215). In conclusion, our findings suggest that the pregnancy rate may be improved by considering lactation number and the interval from calving to the next AI of RBCs in estrus synchronization using a combination of PRID + PGF2α and AI + ET.

PSV-8 Sire field fertility does not correlate with sire conception rate (SCR) score

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 304-305
Author(s):  
Gessica A Franco-Johannsen ◽  
Marcos Henrique C Pereira ◽  
M Sophia Ortega ◽  
Sydney T Reese ◽  
Jose Luiz M Vasconcelos ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Pregnancy Loss ◽  
Current Method ◽  
Conception Rate ◽  
Main Hypothesis ◽  
Significant Challenge ◽  
Fertility Status ◽  
Sire Conception Rate ◽  
Individual Service ◽  
In Pregnancy

Abstract Accurate sire fertility evaluation remains a significant challenge in the livestock industry. Sire conception rate (SCR) has been used since 2008 in the dairy industry to rank sire fertility. The objective was to characterize individual sire pregnancy rate, pregnancy loss, and determine the correlation with the sire’s respective SCR. Our main hypothesis is that large variances in fertility parameters by sire cannot be explained by variance of the SCR values. Data from 6,570 timed artificial inseminations (AI) and 25,287 timed embryo transfers (ET) from 55 dairy farms were retrospectively analyzed to assess: pregnancy rate at day 30 (P30), pregnancy rate at day 60 (P60) and pregnancy loss (PL) during this interval. The effect of sire (AI: n = 39; ET: n = 81) for each reproductive parameter was evaluated. SCR records published prior to individual service were obtained to correlate with fertility parameters. For AI mating, pregnancy rate at P30 was 33.13% (2,177/6,570), and 27.6 % for P60 (1,815/6,570) and PL occurred in 16.6% (362/2,177) of pregnancies. Large variance was observed between sires for each parameter but no or negligible correlation (r &lt; 0.2) with published SCR was observed. For ET, pregnancy rate at P30 was 47.8% (12,082/25,287) and 40.5% for P60 (10,246/25,287) with an overall PL of 15.2% (1,836/12,082). Similar to AI, all fertility parameters were highly variable among sires but no or negligible correlation (r &lt; 0.03) with respective SCR was observed. In summary, the current method to evaluate sire fertility using SCR does not truly represent the field fertility status. Large variance in pregnancy loss between days 30 and 60 of gestation were observed among sires and these phenotypes should be considered when evaluating sire fertility to increase the score reliability.

scholarly journals The reproductive performance of dairy cows with anovulatory anoestrus that were injected with either gonadotrophin-releasing hormone or oestradiol benzoate as part of a re-treatment process after insemination

2007 ◽  
Vol 78 (1) ◽  
Author(s):  
B.V.E. Segwagwe ◽  
J. Malmo ◽  
K.L. Macmillan ◽  
P.D. Mansell
Keyword(s):  
Dairy Cows ◽  
Pregnancy Rate ◽  
Reproductive Performance ◽  
Conception Rate ◽  
Control Group ◽  
Releasing Hormone ◽  
Start Date ◽  
Oestradiol Benzoate ◽  
Conception Rates ◽  
Gonadotrophin Releasing Hormone

This experiment compared the reproductive performance of synchronised anoestrous dairy cows that were treated initially with a combination of progesterone and oestradiol benzoate and then with either gonadotrophin-releasing hormone (GnRH) or oestradiol benzoate to resynchronise returns to service. It was hypothesised that injecting anoestrous dairy cows with GnRH 12-15 days after insemination and coinciding with the time of insertion of a controlled intravaginal progesterone-releasing (CIDR) device would increase conception rates to the preceding 1st insemination compared with oestradiol benzoate treated cows; both GnRH and oestradiol benzoate would resynchronising the returns to service of those cows that did not conceive to the preceding insemination. Groups of cows in 11 herds were presented for a veterinary examination after they had not been seen in oestrus postpartum. Those cows diagnosed with anovulatory anoestrus (n = 1112) by manual rectal palpation and / or ultrasonography were enrolled in the trial. Each enrolled cow was injected with 2mg oestradiol benzoate i.m. on Day -10, (where Day 0 was the 1st day of the planned insemination) concurrently with vaginal insertion of a CIDR device. The device inserted was withdrawn on Day -2 and then each cow injected i.m. with 1 mg of oestradiol benzoate on Day -1 unless it was in oestrus. Observation for oestrus preceded each insemination. Every cow that had been inseminated on Days -1,0,1 or 2 was presented for treatment for resynchrony on Day 14 (n=891). They were divided into 2 groups; those with an even number were each injected i.m. with 250 µg of a GnRH agonist (Treatment group n = 477); each of the cows with an odd number injected i.m. with 1mg of oestradiol benzoate (control group, n = 414). Each GnRH or oestradiol benzoate injection preceded reinsertion of a CIDR device previously inserted from Days -10 to -2. It was withdrawn on Day 22, 24 hours before injecting 1mg oestradiol benzoate. Cows observed in oestrus were submitted for a 2nd insemination. Every enrolled cow still present in the herd was pregnancy tested by palpation of uterine contents per rectum about 6 weeks later and again at the end of a herd's seasonal breeding programme. The alternative use of GnRH instead of oestradiol benzoate did not affect the percentage of cows conceiving within 3 days of the mating start date (MSD) (35.6 %vs 35.3 %, P=0.90), resubmission rates for a 2nd insemination among cows not pregnant to the 1st insemination (81.6 % vs 83.5 %, P=0.41), 6-week pregnancy rate (59.3 % vs 60.6 %, P=0.65), 21-week pregnancy rate (86.6 vs 85.0, P=0.36), mean interval from MSD to conception (32.5 + 1.8 days vs 29.9 + 1.8 days, P = 0.26) or conception rate of cows reinseminated by Day 28 (43.3 % vs 38.8 %, P=0.39). When GnRH conception rate of cows reinseminated by Day 28 (43.3% vs was compared with oestradiol benzoate, it did not increase conception rates to the 1st service; it was as effective as oestradiol benzoate in synchronising returns to service in previously treated anoestrous cows that did not conceive to the 1st service. Its use affected neither conception rates to the preceding 1st inseminations nor to the following 2nd inseminations.

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