Artificial Insemination Conception Rate Research Articles

Characterization of conception rate after embryo transfer in comparison with that after artificial insemination in dairy cattle

Artificial insemination (AI) and embryo transfer (ET) are important in the reproduction of dairy cows. The conception rate after AI or ET is an essential indicator when selecting appropriate breeding methods. However, information on the environmental factors affecting ET conception rate when compared with AI is limited. We aimed to investigate environmental factors affecting ET conception rate and characterize the differences in environmental factors between AI and ET. Records of the first AI (n = 1,870,143) and ET (n = 29,922) from Holstein nulliparous, primiparous, and multiparous cows in Hokkaido, Japan, were analyzed using separate multivariable logistic regression models. For each breeding method, we grouped primiparous and multiparous cows according to milk yield at peak lactation (PY; < 25, 25-30, 30-35, ≥ 35 kg in primiparous, < 40, 40-45, 45-50, ≥ 50 kg in multiparous) and the interval from calving to first AI or ET (CFI/CFT; < 60, 60-79, 80-99, ≥ 100 d) to evaluate the effects of PY and CFI/CFT on conception rate. AI conception rate decreased with increasing PY in primiparous and multiparous cows, whereas ET conception rate did not decrease significantly. Additionally, the ET conception rate did not decrease even in primiparous and multiparous cows slightly earlier than 60 d in CFI/CFT when compared with those in CFI/CFT after 60 d, which differed from the AI conception rate. Collectively, breeding by ET leads to the avoidance of negative effects of high milk yield and calving on the conception rate, indicating that cows are fertile by ET within 60 d after calving.

Determining the clinical utility of a single pre-breeding examination for predicting subsequent reproductive performance in seasonal pasture-based dairy heifers

Heifers that conceive early in the breeding season are key to the maintenance of a compact calving pattern in seasonal dairy herds. The purpose of this prospective observational study was to determine whether a single pre-breeding examination is useful in predicting future reproductive and calving performance in dairy heifers. This evaluation was based on a matrix of easily measurable variables which could be applied to seasonal, pasture-based dairy heifers. The matrix variables were; body weight (≥55% mature body weight at mating start date), body condition score (≥3.5), and the presence of a corpus luteum. Seasonal, pasture-based dairy heifers (n = 572) on six commercial dairy farms were examined at an average of 28 days prior to the breeding season. At this examination, they were classified as READY (meeting all three of the above criteria), INTERMEDIATE (meeting one or two of the above criteria) or PROBLEM (meeting none of the above criteria) based on the matrix and then exposed to a routine artificial insemination (AI) breeding period followed by bull breeding depending on individual farm management. Subsequent pregnancy status was determined by transrectal ultrasonography initially at 30–60 days in calf (DIC), and confirmed at over 60 DIC. After the breeding season, 519 (96%) of heifers were determined to be pregnant, of which 345 (64%) became pregnant within the first three weeks of the breeding season. Farmers collected calving data; including calving difficulty score, from the heifers the following spring. A logistic regression model was used to analyse the association between the matrix categories and the following outcomes: reproductive (21 day submission rate, 1st AI conception rate, 3 wk and 6 wk in calf rate) and calving (assistance and dystocia). Heifers classified as PROBLEM had significantly lower odds of conceiving to the first AI serve and of becoming pregnant within the first three and six weeks of the breeding season (P ≤ 0.05). In conclusion, the proposed matrix could be practically useful for classifying heifers prior to the breeding season.

Impacts of heifer postweaning residual feed intake classification on reproductive and performance measurements of first-, second-, and third-parity Angus beef females.

This study evaluated heifer postweaning residual feed intake (RFI) classification on reproductive and performance measurements of first-, second-, and third-parity Angus beef females. We analyzed the annual, as well as, cumulative production of 347 Angus females from birth through weaning of their third calf. Heifer postweaning RFI was calculated as the actual dry matter intake minus the predicted dry matter intake based on the average daily gain of the contemporary group on an annual basis. Heifers were categorized based on RFI as either low (< −0.50 SD from mean), average (± 0.50 SD from mean), or high (> +0.50 SD from the mean) within year. There was no RFI × Parity interaction (P ≥ 0.14) observed for all production/reproduction traits except for conception rates (P = 0.02). Julian birth date of cows was influenced by RFI classification (P < 0.01) and displayed a quadratic (P = 0.02) effect with high RFI cows being born earlier in the calving season than average RFI cows (71.2 vs. 75.3 d), but did not differ from low RFI cows (74.0 vs. 75.3 d). Cow birth weight, weaning weight, as well as all other cow weight and body condition measurements were not influenced by RFI classification (P ≥ 0.14). As expected, there was a linear increase in cow body weight at weaning with increasing parity (P < 0.01). Cow RFI classification had no influence on progeny weaning weight, birth date, calving interval, or postpartum interval (P ≥ 0.15). Calf birth weights displayed a quadratic parity effect (P < 0.01) with first calf heifers having calves with lower birth weights than second- and third-parity calves. Calf 205-d adjusted weaning weights displayed a quadratic effect (P = 0.01) with first calf heifers weaning lighter calves than second- and third-parity cows. Weaning weight ratio displayed a linear decrease with increasing parity (P < 0.01). Cow conception probability displayed a linear tendency for pregnancy 2 (P = 0.09), and a quadratic tendency for pregnancy 4 (P = 0.07) as a function of RFI classification, but no effects were observed for pregnancy 1 and 3. Cow artificial insemination conception rates differed by year of pregnancy (P < 0.01), but not RFI classification (P = 0.81). In summary, heifer postweaning RFI classification had minimal effects on beef cattle production and reproductive efficiency.

Correlation between in vitro fertilization and artificial insemination in Holstein bulls.

ObjectiveOwing to the lack of a breeding index for efficient and quick fertility evaluations of Holstein bulls when using traditional or genome-wide detection methods, this study aimed to determine whether in vitro fertilization (IVF) could be used as an indicator of conception rate of artificial insemination (AI).MethodsConventional and sexed frozen semen from nine bulls were used for IVF and AI.ResultsThe IVF and AI conception rates of each bull were confirmed to be positively correlated between the conventional frozen and sexed frozen semen. The correlation coefficient R values of nine bulls between IVF and AI methods were 0.73 and 0.97 for the conventional frozen and sexed frozen semen, respectively. The average conception rate of three bulls undergoing AI was 69.5% and 64.2%, 61.8% and 58.8%, and 48.2% and 46.2% in first-, second-, and third-born cows when conventional frozen and sexed frozen semen were used, respectively, which showed a positive correlation with the fertilization rate in the same parity. We propose an evaluation standard to assess the fertilization ability of bulls based on their IVF test results, which is categorized into three grades: grade one, normal fertility bull with an AI conception rate of 40%±5% and IVF rate of 45% to 60%; grade two, higher fertility bull with an AI conception rate of 50%±5% and IVF rate of 61% to 80%; and grade three, highest fertility bull with an AI conception rate of 60%±5% and IVF rate of >80%.ConclusionThese findings reveal that IVF results can be used as a breeding index for bulls to evaluate their AI conception ability, which may shorten the time required to select bulls for breeding.

Effect of a second treatment of prostaglandin F2α during the Ovsynch program on fixed‐time artificial insemination conception rates and luteolysis in split‐calving, pasture‐fed dairy cows

To compare fixed-time artificial insemination (FTAI) conception rates and serum progesterone concentrations at the time of FTAI for cows treated with the original Ovsynch program (OV) with those treated with a modified Ovsynch (MO) program. This was a randomised clinical trial. The study used five split-calving, pasture-based dairy herds in Southwest Victoria, Australia. Controls (n = 851) received the OV program: day 0 gonadotropin-releasing hormone, day 7 prostaglandin F2α (PGF), day 9 gonadotropin-releasing hormone and FTAI at day 10. The treatment group (n = 852) received a MO program with an additional prostaglandin injection on day 8. Subsets of cows from each group were sampled for blood progesterone at the time of FTAI. The treatment group demonstrated FTAI conception rates that were 7% (95% confidence interval 2%-12%) greater than the control group. After adjusting for the effect of age, days in milk at Mating Start Date and herd, the odds of conception using FTAI was 1.36 (95% confidence interval 1.12-1.66) times greater for treatment group cows compared with control group cows. The variability of serum progesterone concentrations at the time of FTAI was significantly less for treatment group cows compared with control group cows. For Holstein-Friesian and Holstein-Friesian cross-bred cows managed in pasture-based dairy herds in southern Australia, a MO protocol, including a second injection of prostaglandin F2α on day 8, increased FTAI conception rates compared with cows receiving the OV protocol.

Impacts of heifer postweaning residual feed intake classification on reproductive and performance measurements of first, second, and third parity Angus beef females.

This study evaluated heifer postweaning residual feed intake (RFI) classification on reproductive and performance measurements of first-, second-, and third-parity Angus beef females. We analyzed the annual, as well as, cumulative production of 347 Angus females from birth through weaning of their third calf. Heifer postweaning RFI was calculated as the actual dry matter intake minus the predicted dry matter intake based on the average daily gain of the contemporary group on an annual basis. Heifers were categorized based on RFI as either low ( +0.50 SD from the mean) within year. There was no RFI × Parity interaction (P ≥ 0.14) observed for all production/reproduction traits except for conception rates (P = 0.02). Julian birth date of cows was influenced by RFI classification (P < 0.01) and displayed a quadratic (P = 0.02) effect with high RFI cows being born earlier in the calving season than average RFI cows (71.2 vs. 75.3 d), but did not differ from low RFI cows (74.0 vs. 75.3 d). Cow birth weight, weaning weight, as well as all other cow weight and body condition measurements were not influenced by RFI classification (P ≥ 0.14). As expected, there was a linear increase in cow body weight at weaning with increasing parity (P < 0.01). Cow RFI classification had no influence on progeny weaning weight, birth date, calving interval, or postpartum interval (P ≥ 0.15). Calf birth weights displayed a quadratic parity effect (P < 0.01) with first calf heifers having calves with lower birth weights than second- and third-parity calves. Calf 205-d adjusted weaning weights displayed a quadratic effect (P = 0.01) with first calf heifers weaning lighter calves than second- and third-parity cows. Weaning weight ratio displayed a linear decrease with increasing parity (P < 0.01). Cow conception probability displayed a linear tendency for pregnancy 2 (P = 0.09), and a quadratic tendency for pregnancy 4 (P = 0.07) as a function of RFI classification, but no effects were observed for pregnancy 1 and 3. Cow artificial insemination conception rates differed by year of pregnancy (P < 0.01), but not RFI classification (P = 0.81). In summary, heifer postweaning RFI classification had minimal effects on beef cattle production and reproductive efficiency.

Post artificial insemination conception rate of a Brahman bull in selected areas of Bangladesh

Background: To mitigate the increasing protein demand in Bangladesh, recently the government has started a program to inspire the farmers for rearing Brahman as a beef breed. But, it is necessary to assess the performance of frozen semen of Brahman bull and the other factors that affect the rate of conception after Artificial Insemination (AI) before widespread rearing in Bangladesh. Methods: Data on AI performance, different factors and rate of conception were collected from 150 inseminated cows and heifers of Sadar upazila, Mymensingh. The cows were inseminated by trained technician of Research Animal Farm of Department of Surgery and Obstetrics, BAU, Mymensingh. Results: The overall conception rate was 55.3%. The conception rate in Holstein Friesian cross (68.9%) and Sahiwal cross (66.7%) cows were relatively higher than that of Local (46%) cows. Upon increasing age the service required for conception was irregular. The conception rate with respect to different parities ranged from 47.0% to 58.7%. Cows received insemination at parity 1-2 showed highest conception rate (60.0%) and cows received insemination at parity 3-7 showed lowest conception rate (47.0%). There was no significant difference between them on conception rate. The conception rate was observed higher (69.2%) in the cows which were inseminated in spring than cows were inseminated in summer (57.3%), winter (53.3%) and rainy (38.5%). The pregnancy rate in cows having BCS 2.5-3 was higher (60.7%) than that of 2.0 and 3.5-4.0. However, the difference in conception rate did not vary significantly among different BCS of cows (p&gt;0.05). The present study indicated that the pregnancy rate in cows was higher (76.9%) that yield 6-10 L of milk than those of 0, 1-2 and 3-5 L counterpart. However, the variation in conception rate with different milk yield was significant (p&lt;0.05). The pregnancy rate in cows that inseminated between 19-24 hours was higher (66.0%) than that of ≤12 and 13-18 hours. The variation in conception rate with different interval between estrus to AI was significant (P&lt;0.05). Conclusion: Further studies using more population of cows and semen donors are needed to confirm this result as low number of cows and only one semen donor were used in this study.

Protein biomarkers for male artificial insemination subfertility in bovine spermatozoa.

BackgroundAlthough artificial insemination (AI) technique is an established biotechnology for bovine reproduction, the results of AI (conception rates) have a tendency to decline gradually. To our annoyance, moreover, AI‐subfertile bulls have been occasionally found in the AI centers. To resolve these serious problems, it is necessary to control the sperm quality more strictly by the examinations of sperm molecules.MethodsWe reviewed a number of recent articles regarding potentials of bovine sperm proteins as the biomarkers for bull AI‐subfertility and also showed our unpublished supplemental data on the bull AI‐subfertility associated proteins.Main findingsBull AI‐subfertility is caused by the deficiency or dysfunctions of various molecules including regulatory proteins of ATP synthesis, acrosomal proteins, nuclear proteins, capacitation‐related proteins and seminal plasma proteins.ConclusionIn order to control the bovine sperm quality more strictly by the molecular examinations, it is necessary to select suitable sperm protein biomarkers for the male reproductive problems which happen in the AI centers.

Optimizing the freezing rate for ovine semen cryopreservation: Phospholipid profiles and functions of the plasma membrane and quality and fertilization of spermatozoa

The objective of this study was to investigate the effects of freezing rate on plasma membrane (PM) phospholipids and the function and fertilization of ram spermatozoa during freezing. Semen was obtained from 10 Merino rams using an artificial vagina, diluted with glucose-egg yolk buffer, and frozen in a programmable freezer at rates of −1, −20, −40, −60, and −80°C/min. After thawing, we examined PM phospholipid content and distribution, fluidity, permeability, potential, spermatozoa quality, and in vivo and in vitro fertilization rates. The results showed that phospholipid, phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) contents of the PM decreased significantly (P<0.05), whereas diphosphatidylglycerol (DPG) content and the cholesterol: phospholipid (CH: PL) ratio increased significantly compared to those of fresh semen after freezing (P<0.05). PE, phosphatidylinositol (PI), and DPG were transferred to the outer leaflet, whereas PS and PG were transferred to the inner leaflet after freezing. Spermatozoa cryopreserved at −40°C/min resulted in distributions of PS, PE, and DPG, as well as increased PM fluidity, permeability, and potential that was greater than those of the other freezing-rate groups (P<0.05). No differences in vitality, PM and acrosome integrity, in vitro fertilization hatching rate, or artificial insemination conception rate were observed in any of the freezing-rate groups (P>0.05), whereas cleavage rate (69.67±5.11%) at −40°C/min increased significantly (P<0.05). Therefore, the optimal freezing rate to cryopreserve ram spermatozoa based on cryoinjury of phospholipids, membrane functions, and fertilization rate was −40°C/min.

Postpartum uterine diseases and their impacts on conception and days open in dairy herds in Italy

The objective of this study was to describe the incidence and the impact of postpartum uterine diseases in postpartum cows on future uterine status and reproductive performance in large Italian dairy herds. This study provides an important quantitative estimate of uterine and postpartum diseases incidence that afflict high-producing Italian dairy cows. The total number of cows included in the study was 1498 on three farms; all cows were followed from the dry period until 300 days postpartum. All farms used high-quality data collection systems and standard operating procedures: weekly herd health visits, monthly Dairy Herd Improvement Association visits, and, due to cheese-making milk quality requirements, a supplementary milk sample collected at 7 ± 3 days postpartum evaluated for milk components. Clinical metritis in primiparous cows did not change the time to the first artificial insemination (AI) or days open; conversely, clinical metritis in multiparous cows had impact on the time to first AI (hazard ratio: 0.66, P < 0.01) and resulted in a lower conception rate at first insemination and a increase in days open (odds ratio: 0.64, P < 0.05). Clinical endometritis had a strong deleterious effect on first AI conception rate (odds ratio: 0.34, P < 0.05) and days open across all lactations (hazard ratio: 0.68, P < 0.05). Persistent metritis, defined as the presence of both clinical metritis and clinical endometritis in the same animal in the same lactation, caused low conception rate both in the first-lactation and in older cows and had a strong negative effect on the proportion of pregnant cows at 300 days (P < 0.05). In conclusion, the impact of endometritis on fertility was true across lactation groups. A good management and precocious diagnosis of the pathologies is not resolutive to restore good fertility parameters, and understanding the immune response in first-lactation cows may be of value for developing alternative intervention protocols for older-lactation cows.

Analysis of the Effect of Natural Environments on Artificial Insemination Conception Rate

This study analyzes the effect of changes in natural environments on the artificial insemination conception rate. For the analysis we set panel data that is comprised of 32 farms and 60 months. For the dependent variable, we calculate artificial insemination conception rate from the 32 farms. For the explanatory variables, we consider three major natural environmental variables: temperature, precipitation, and wind speed. Furthermore, we use monthly dummy variables to control the effects of monthly fixed effects. Results show that temperature variable is highly significant variable. It is estimated that one celsius degree increase leads to -0.6% decrease in artificial insemination conception rate. Among monthly variables, January, April, June, July, and August are highly significant. Average conception rates are 44%, 33%, 32%, and 27% for January, April, June, July, and August, respectively. Conception rate is analyzed to be decreased in Summer season and to be increased in Winter season.

Relationships between docility and reproduction in Angus heifers (2014)

Reproductive success is relevant in beef cattle operations because income generated by the sale of calves is often a large portion of an operation's income. Selecting for fertility is difficult because it is influenced by a variety of factors. Temperament could be a factor affecting fertility. Physiological responses associated with temperament can influence the probability of cows becoming pregnant because stress hormones in the bloodstream can negatively affect the release of reproductive hormones. Methods have been developed to assess temperament in cattle. Exit velocity measures the time it takes for an animal to cover a predetermined distance after vacating a chute. Chute scores range from 1 (quiet) to 6 (aggressive) and are based on the animal's behavior when confined in a chute. Positive correlations of chute score and exit velocity with cortisol indicate that both scores are reliable indicators of temperament. Handling of cattle is associated with changes in concentrations of stress hormones. Blood serum collection can provide insight into short-term stressors, and fecal sampling can be reflective of stress experienced 2'3 days before sampling. This study was conducted to investigate the relationship between animal temperament and heifer fertility as indicated by first-service artificial insemination conception rate.

Artificial Insemination With Seminal Plasma Improves the Reproductive Performance of Frozen‐Thawed Boar Epididymal Spermatozoa

Frozen-thawed epididymal spermatozoa have good fertilization capability in vitro; however, their artificial insemination conception rate is less than half of that of frozen-thawed ejaculated spermatozoa. Because the addition of seminal plasma to the thawing solution enhances the in vivo fertilizing ability of frozen-thawed ejaculated spermatozoa, we hypothesized that the reproductive performance of frozen-thawed epididymal spermatozoa could also be improved by the inclusion of seminal plasma. When frozenthawed epididymal spermatozoa were incubated for up to 6 hours, the motility of the sperm significantly decreased in a time-dependent manner. The acrosomal membrane was damaged in the majority of frozen-thawed epididymal spermatozoa. The addition of seminal plasma to the thawing solution significantly decreased the percentage of sperm with abnormal acrosomes and increased their total motility in a dose-dependent manner. Furthermore, the addition of seminal plasma reduced the abundance of a 15-kDa tyrosinephosphorylated protein in frozen-thawed sperm, and the maximum effect was observed at 15% (vol/vol) seminal plasma. When cryopreserved epididymal spermatozoa from 3 different boars were thawed with a 15% (vol/vol) seminal plasma-containing solution, the conception rate and mean litter size obtained by artificial insemination were significantly increased as compared with those in the control without seminal plasma. From these results, we concluded that the addition of seminal plasma to the thawing solution is a key step in obtaining an optimal number of piglets by artificial insemination using frozen-thawed boar epididymal spermatozoa.

Slow Recovery of Blood Glucose in the Insulin Tolerance Test during the Prepartum Transition Period Negatively Impacts the Nutritional Status and Reproductive Performance Postpartum of Dairy Cows

In peripartum dairy cows, insulin resistance (IR) increases to adjust the direction of energy to lactation after calving. To investigate the effect of prepartum IR on postpartum reproductive performance, the insulin tolerance test (ITT) was applied to 15 cows at 3 weeks (Pre21) and 10 days (Pre10) before the predicted calving date. Blood glucose area under the curve (AUC(glu)) within 120 min after administration of 0.05 IU/kg-BW insulin was calculated. The occurrence of first ovulation, days to first artificial insemination (AI) and first AI conception rate were recorded. Nutritional status postpartum was evaluated by blood chemical analysis. Based on AUC(glu) changes from Pre21 to Pre10, cows were classified into either the AUC-up group (AUC(glu) increase, n=5) or the AUC-down group (AUC(glu) decrease, n=10). There was no difference in the decrease in blood glucose at 30 min after insulin injection between groups, although glucose recovery from 30 to 60 min during the ITT was slow at Pre10 in the AUC-up group. The AUC-up group had a higher number of days to first AI and high glucose, total protein, globulin, γ-glutamyltransferase, triacylglycerol levels and a low albumin-globulin ratio at the 14th day postpartum. The present study infers that prepartum slow glucose recovery rather than insulin sensitivity might increase the potential for subclinical health problems postpartum and thus suppress reproductive performance. During the prepartum transition period, glucose dynamics in the ITT can be considered as a new indicator for the postpartum metabolic status and reproductive performance of dairy cows.

Efficacy of carprofen on conception rates in lactating dairy cows after subcutaneous or intrauterine administration at the time of breeding

Manipulation of the reproductive tract can cause inflammatory processes in the endometrium and release of cytokines and prostaglandins. It has been shown that PGF2α has direct negative effects on embryonic survival and development. Treatment with nonsteroidal antiinflammatory drugs (e.g., ibuprofen lysinate, flunixin meglumine) might improve pregnancy rates after embryo transfer in recipient heifers. The primary objective of this study was to evaluate the effect of a nonsteroidal antiinflammatory drug on reproductive performance in lactating dairy cows when administered at the time of first-service artificial insemination (AI) based on the hypothesis that uterine manipulation during AI might be similarly intense compared with embryo transfer in its effect on prostaglandin release. A total of 970 cows (333 primiparous and 637 multiparous) from 17 Holstein dairy farms were enrolled. On the day of first AI, cows were randomly allocated to 1 of 3 treatment groups. Cows of group 1 received 1.4mg/kg of body weight (BW) of carprofen subcutaneously immediately after AI (SC group). In group 2, 1.4mg/kg of BW of carprofen was administered into the uterus using a sterile disposable catheter 12 to 24h after AI (IU group). Animals of group 3 remained as untreated controls. First AI conception rate was similar for the SC group (42.2%) compared with the untreated control group (45.1%). A binary logistic regression model for the odds of conception at first AI revealed a negative effect of an intrauterine administration of carprofen on conception rate (38.3%). Cows allocated to the IU group had a lower likelihood of being pregnant within 200 d in milk than cows in the control group. In summary, subcutaneous treatment with the nonsteroidal antiinflammatory drug carprofen at the time of AI did not influcence conception rate, whereas an intrauterine administration of carprofen 12 to 24h after first AI had a negative effect on first-service conception rate in lactating dairy cows.

Presynchronization with gonadotropin-releasing hormone increases the proportion of Bos indicus-influenced females ovulating at initiation of synchronization but fails to improve synchronized new follicular wave emergence or fixed-time artificial insemination conception rates using intravaginal progesterone, gonadotropin-releasing hormone, and prostaglandin F2α1

The objectives were to evaluate the effect of presynchronization with GnRH on pregnancy rates (Exp. 1) and ovarian events (Exp. 2) in Bos indicus-influenced females synchronized with CO-Synch + controlled internal drug release (CIDR) as described below. In Exp. 1, a total of 135 Brahman x Hereford (F(1)) females were assigned randomly after stratification to 1) Presynch; presynchronization followed by CO-Synch + CIDR, or 2) No Presynch; CO-Synch + CIDR without presynchronization. On d -7, cattle received 100 microg of GnRH or 2 mL of intramuscular (i.m.) saline. On d 0, all cattle received a CIDR and i.m. injection of GnRH (GnRH-1), followed by CIDR removal and i.m. injection of 25 mg of PGF(2alpha) (PGF) on d 7, and i.m. injection of GnRH (GnRH-2) and timed AI (TAI) 66 h after CIDR removal (d 10). An additional 77 cows not involved in the Presynch comparison were also treated with CO-Synch + CIDR. Pregnancy rates for Presynch (37.3 +/- 6%) and No Presynch (48.5 +/- 6.1%) did not differ (P = 0.6). Pregnancy rate for all CO-Synch + CIDR-treated cattle combined was 41.9 +/- 6.1 (n = 145). In Exp. 2, we examined ovarian events in 98 Brahman x Hereford (F(1)) cows assigned randomly to Presynch or No Presynch. Ovulatory response to GnRH-1 was greater (P < 0.01) in the Presynch (58 +/- 7.1%) than in the No Presynch (27.1 +/- 6.5%) group. However, emergence of a synchronized new follicular wave after GnRH-1 and ovulation rate after GnRH-2 did not differ between groups (P = 0.4). Presynchronization increased the proportion of females ovulating after GnRH-1, but this did not increase synchrony of new follicular wave emergence or ovulation after GnRH-2, and did not improve TAI pregnancy rates.

Oestrus synchronisation and fixed time artificial insemination in beef heifers

To compare two oestrus synchronisation protocols in beef heifers presynchronised with two prostaglandin F2α (PG) treatments, 36 h after the second PG treatment one group (hCG-OB group; n = 112) received 250 IU of hCG and 0.5 mg of oestradiol benzoate (OB) followed by fixed time artificial insemination (FTAI) 30 h later. Additional oestrus detection (OD) and artificial insemination (AI) was done in this group for 3 days after FTAI; heifers rebred during this period were considered open to the FTAI. The Control group (n = 112) received only OD and AI for 6 days after the second PG treatment. Follicular size was measured at the time of AI in a subsample of heifers (59 in the hCG-OB group and 34 in the Control group). Results were evaluated separately either considering heifers pregnant at FTAI or those pregnant at FTAI + 3-day OD + AI. The FTAI conception rate was 45.5 vs 76.5% for the Control group (P &lt; 0.0001) and pregnancy rates were 45.5 and 67.0% (P = 0.0014); FTAI + OD + AI conception rates were 63.4 and 76.2% (P = 0.0404) and pregnancy rates 63.4 and 62.8% (P = 0.5719) (hCG-OB and Control groups, respectively). There was a significant correlation (r = 0.713, P &lt; 0.01) between follicle size at FTAI and pregnancy in the hCG-OB group, but not in the Control group (r = 0.3465, P &gt; 0.1). In conclusion, acceptable synchronised conception rate and pregnancy rate were obtained by using this protocol, and the results were improved by complementing it with OD + AI for 3 days after FTAI.

Relationships Between the Concentration of Insulin-Like Growth Factor-1 in Serum in Dairy Cows in Early Lactation and Reproductive Performance and Milk Yield

The objective of this study was to evaluate the relationships of different insulin-like growth factor-1 (IGF1) measures [5 distinct IGF1 concentrations on particular days, area under the curve (AUC), and linear regression coefficient] in the postpartum period in lactating dairy cows and reproductive performance. A total of 417 healthy multiparous Holstein-Friesian cows were enrolled in the study. Serum samples for the determination of the concentration of IGF1 were collected on d 0, 4, 10, 20, and 40 postpartum (pp). The concentration of total IGF1 in serum was determined by immunometric chemiluminescence immunoassay. All cows were examined for vaginal discharge as a sign of clinical endometritis at 20 d pp by external inspection and rectal palpation. The mean concentration of IGF1 ranged from 57±18.9 ng/mL within the first 12h pp to 74±19.9 ng/mL at 40 d pp. On d 10 pp, first and all artificial insemination conception rates were greater in cows with IGF1 concentrations above the median compared with cows with IGF1 concentrations below the median. Cows with greater AUC (second to fourth quartile) conceived earlier (11.4, 16.0, and 18.8 d) than cows in the first IGF1 quartile (117.0±43.6). Proportion of cows pregnant within 200 d pp increased significantly from the first to the third IGF1 quartile of AUC (58.7, 66.7, and 74.0%). The proportion of cows culled decreased from the first to the fourth IGF1 quartile. Correlations between IGF1 measures and days to pregnancy were significant (except for the linear regression coefficients) but low (R2=0.0009 to 0.025). Differences between single or composite measurements of IGF1 were not significant. We could also demonstrate a statistically significant correlation between the concentration of IGF1 in serum and the average 10-d milk production (31.6 to 44.0kg). In conclusion, our study indicates that single or multiple measurements of IGF1 concentration in the postpartum period have very limited value to predict individual fertility in dairy cows.

Timed artificial insemination conception rates in response to a progesterone insert in lactating dairy cows (2007)

Our objective was to determine the effectiveness of exogenous progesterone in the form of an intravaginal insert (controlled internal drug release, CIDR) in conjunction with an ovulation synchronization protocol in lactating dairy cows. Cows received a Presynch protocol (two injections of prostaglandin F2α[PGF2α] 14 days apart) beginning 30 and 36 days in milk, respectively, in two herds. Cows were inseminated after the second Presynch injection when estrus was detected. Remaining cows were treated with the Ovsynch protocol, and alternate cows were assigned randomly to receive a progesterone insert(CIDR). Blood was collected, and body condition scores (BCS) were assigned to treated cows. Pregnancy status was confirmed by palpation on day 38 post timed AI (TAI) and verified again 4 weeks later. Progesterone increased conception rates in treated cows when compared with controls (38 vs. 24%), but did not differ from early inseminated cows(38%). Pregnancy loss was numerically less in progesterone-treated cows than in controls(4.4 vs. 11.8%).; Dairy Day, 2007, Kansas State University, Manhattan, KS, 2007; Dairy Research, 2007 is known as Dairy Day, 2007

A comparison of performance of the Ovsynch treatment program between cycling and non‐cycling cows within seasonally‐calving dairy herds

To compare performance of the Ovsynch program on reproductive performance between cycling and non cycling cows in seasonally-calving herds. An Ovsynch mating program (100 mg Gonadorelin on day 1 and day 9, 500 mg of Cloprostenol on day 7 with fixed time artificial insemination on day 10) was administered to 3,559 cows from 14 herds in Australia and New Zealand. Cycling status before planned start of mating was determined. All cows were treated and artificial insemination continued for at least 25 days after fixed time artificial insemination. Pregnancy testing was performed 75 to 100 days after fixed time artificial insemination. Multivariable modelling examined the impact of the Ovsynch program and other risk factors upon reproductive performance. Thirty percent of cows were classified as no visible oestrous (NVO). Odds of being NVO increased significantly for cows that were young, recently calved, and in low body condition. The fixed time artificial insemination conception rate was 35.7% and 33.2%, 21-day pregnancy rate was 54.5% and 48.4% and 42-day pregnancy rate was 69.7% and 62.6% for cycling and NVO cows respectively. Odds of pregnancy increased significantly for cows calved more than 40 days by planned start of mating, in greater body condition, and cycling, and there was a significant interaction between body condition and cycling status in both models. The return-to-service rates by 24-days were 67.6% and 55.9% and by the end of the AI period were 86.9% and 81.5% for cycling and NVO cows respectively. Odds of return to service increased significantly for cows in greater condition score in both models. Odds of return were increased for cycling cows in the 24-day multivariable model. The Ovsynch program may provide a useful treatment option for NVO cows within seasonally-calving pasture-based dairy herds.