Conception Rate Of Cows Research Articles

Long-lasting effects of in utero heat stress on subsequent performances of heifers and primiparous cows

The performance of an adult dairy cow may be influenced by heat stress that occurs during her gestation. The present study investigated potential effects of temperature-humidity index (THI) experienced by a cow during pregnancy, on the gestated daughter's performance on her first lactation, for the French Holstein and Montbeliarde dairy cattle populations. Fourteen traits were analyzed, all measured on genotyped cows: 305-d milk, fat, and protein yields, 305-d somatic cell score, clinical mastitis (both occurrence and number of events), body conformation traits, and heifer and cow conception rate. To study the effect of heat stress, we considered the THI experienced by the gestating cow, averaged for each month of her pregnancy and then categorized in 7 classes (≤40; 40-45; 45-50; 50-55; 55-60; 60-65; and >65). These average THI classes were then fitted as categorical covariates in the regression models used for this study, which included other fixed effects, and the genomic estimated breeding value as a covariate, both specific to each trait, the latter previously obtained from the official French evaluations. The THI effect was therefore estimated as the deviation between the observed and the predicted performances. In general, the estimated heat stress effects were small, presenting limited practical impact on the studied traits, and particularly for fertility and udder health, the estimated heat stress effects were not statistically significant. For the production traits, i.e., milk, fat, and protein yields, the estimated effect associated to high THI experienced at the beginning of the gestation was negative, and lightly positive when associated to high THI experienced by the dam at the end of her pregnancy. Finally, our results suggest that under the current French climate conditions, heat stress experienced by cows during any stage of their pregnancy has limited impact on future performances of their gestated daughters, however we cannot exclude that significant in utero heat stress effect may be present in climate conditions warmer than the French.

Investigating the impact of paternal age, paternal heat stress, and estimation of non-genetic paternal variance on dairy cow phenotype

BackgroundLinear models that are commonly used to predict breeding values in livestock species consider paternal influence solely as a genetic effect. However, emerging evidence in several species suggests the potential effect of non-genetic semen-mediated paternal effects on offspring phenotype. This study contributes to such research by analyzing the extent of non-genetic paternal effects on the performance of Holstein, Montbéliarde, and Normande dairy cows. Insemination data, including semen Batch Identifier (BI, a combination of bull identification and collection date), was associated with various traits measured in cows born from the insemination. These traits encompassed stature, milk production (milk, fat, and protein yields), udder health (somatic cell score and clinical mastitis), and female fertility (conception rates of heifers and cows). We estimated (1) the effects of age at collection and heat stress during spermatogenesis, and (2) the variance components associated with BI or Weekly aggregated BI (WBI).ResultsOverall, the non-genetic paternal effect estimates were small and of limited biological importance. However, while heat stress during spermatogenesis did not show significant associations with any of the traits studied in daughters, we observed significant effects of bull age at semen collection on the udder health of daughters. Indeed, cows born from bulls collected after 1500 days of age had higher somatic cell scores compared to those born from bulls collected at a younger age (less than 400 days old) in both Holstein and Normande breeds (+ 3% and + 5% of the phenotypic mean, respectively). In addition, across all breeds and traits analyzed, the estimates of non-genetic paternal variance were consistently low, representing on average 0.13% and 0.09% of the phenotypic variance for BI and WBI, respectively (ranging from 0 to 0.7%). These estimates did not significantly differ from zero, except for milk production traits (milk, fat, and protein yields) in the Holstein breed and protein yield in the Montbéliarde breed when WBI was considered.ConclusionsOur findings indicate that non-genetic paternal information transmitted through semen does not substantially influence the offspring phenotype in dairy cattle breeds for routinely measured traits. This lack of substantial impact may be attributed to limited transmission or minimal exposure of elite bulls to adverse conditions.

A large population study to assess the magnitude of prenatal programming in dairy cattle

The performance of an adult dairy cow may be influenced by events that occur before her birth. The present study investigated potential effects of 2 prenatal groups of factors, Assisted Reproductive Techniques (ART) and maternal characteristics (e.g., dam parity), on offspring performance during their first lactation, in populations of 2 dairy cow breeds: French Holstein and Montbéliarde. The different ART studied included the type of semen (conventional or X-sorted) used for Artificial Insemination (AI) and the technology of conception used (AI, embryo transfer, or in vitro fertilization). Three maternal characteristics were considered: (1) the dam age at first calving, (2) dam parity number, and (3) indicators of dam udder health during gestation (somatic cell score and events of clinical mastitis). First, we investigated whether heifer survival from 3d to 18 mo old was associated with any of the prenatal factors considered. We then estimated the associations of these prenatal factors with 8 traits of commercial interest: (1) stature, (2-4) milk, fat, and protein yields, (5) somatic cell score, (6) clinical mastitis, and (7-8) heifer and cow conception rate, all measured on genotyped cows. Linear models were used for this study with the prenatal factors as covariates in the model, and for the 8 traits, phenotypes were adjusted for their corresponding genomic estimated breeding value. The results indicated that the survival rate of heifers born from embryo transfer was significantly higher than that of heifers born from AI (probably due to preferential management practices), while the other prenatal factors did not explain differences in heifer survival. Among the Montbéliarde cows born from AI, those born from X-sorted semen showed a lightly but significantly lower milk yield than those born without X-sorting of the semen (-52 kg of milk in the first lactation). Among the Holstein cows, those born from embryo transfer presented significantly lower milk performance than cows born from AI. Regarding the maternal characteristics, none or very weak associations were found between the dam age at first calving and the offspring performance in both breeds. Dam parity, on the other hand, was associated with offspring performance for milk, fat, and protein yield in both breeds, however not in the same direction. In the Holstein breed, an increase in dam parity was favorable for offspring performance for milk, fat, and protein yield, whereas in the Montbéliarde breed, an increase in dam parity was associated with lower milk and protein yield and no association was found for fat yield. The udder health of the dam during gestation was not or only weakly associated with the traits studied in the offspring. Although some significant associations were identified due to the large sample size, the effects were modest, typically less than 1% of the phenotypic mean, and were not consistently observed across the 2 breeds.

Conception rates of cows inseminated with frozen semen of Rural Development Academy, Bogura, Bangladesh

Background: The first service conception rate (FSCR) is an important parameter for any artificial insemination (AI) programme. The present study was conducted to determine the FSCR and its influencing factors in cows inseminated with frozen semen produced by Rural Development Academy, Bogura. Methods: Data were collected from 372 cows at 39 villages under Sherpur Upazilla of Bogura district on breed, age, body condition score (BCS), parity, milk yield, suckling, AI season and the interval between oestrus to AI using a questionnaire. Results: The overall FSCR of cows was 66.4% and the service per conception was 1.53. The FSCR was higher (74.1%) in local cows compared to the Holstein-Friesian (HF) cross counterpart (64.2%). The FSCR was higher (70.4%) in 24-47 months old cows compared to 84-98 months old counterpart (61.5%). The highest FSCR (81.6%) was observed in cows with 3.0 to 3.5 BCS and the lowest (25.7%) was observed in cows with 2.5 BCS. The highest FSCR (68.3%) was observed in the 0 (zero) parity (heifers) group of cows and the lowest (62.5%) was observed in the 4-7 parity counterpart. The highest FSCR (72.4%) was observed in cows yielded daily >15-22 L milk and the lowest (62.1%) was observed in cows yielded ≤5 L milk. The highest FSCR (72.7%) was observed in suckling restricted cows and the lowest (60.9%) was observed in cows that had several times suckling daily. The highest FSCR (72.1%) was observed in cows received inseminations in Rainy (July-October) season and the lowest (58.4%) was observed in cows received inseminations in Winter (November-February). The highest FSCR (67.1%) was observed in cows received inseminations between 12-18 hrs of detection of oestrus and the lowest (59.1%) was observed in cows received insemination between 8-11 hrs of detection of oestrus. However, the difference in FSCR in cows with different BCS groups was significant (p<0.01). Conclusion: The current FSCR in cows can be considered to be satisfactory. The BCS of cows significantly influences the FSCR in cows.

Effect of seminal plasma treatment on conception rate in Holstein cows

Effect of seminal plasma treatment on conception rate in Holstein cows

Rumen-protected methionine modulates body temperature and reduces the incidence of heat stress temperatures during the hottest hours of the day of grazing heat-stressed Bos indicus beef cows.

This study evaluated the effects of supplementation of rumen-protected methionine (RPM) on body thermoregulation and conception rate of Nelore cows exposed to high temperature-humidity index (THI). On -31 days before the artificial insemination protocol, 562 lactating, multiparous cows were assigned to receive (MG) or not (CG) RPM supplementation (3 g/cow mixed into 100 g of mineral supplement). Both groups remained in tropical pastures and received supplementation for 77 days. A subset of cows (n= 142) remained with an intravaginal thermometer collecting intravaginal temperature (IT). The respective minimum, average, and maximum environmental THI were 72.8, 78.0, and 83.3. Effects of treatment × hour of the day were detected (P< 0.0001) for IT. From 1330 to 1730 h and 1830 to 1900 h, IT was higher (P< 0.05) for CG versus MG cows when exposed to moderate and high THI. The supplementation with RPM did not affect conception rate (CG = 64.4% vs. MG = 58.2%; P> 0.05). In conclusion, 3g of RPM supplementation lowered internal body temperature and possibly altered critical THI threshold in Nelore cows with no impact on reproduction.

Exploring Prevalence and Contributing Risk Factors of Repeat Breeding Syndrome of Crossbred Dairy Cows in Bangladesh

The dairy sector suffers significant financial losses due to repeat breeding syndrome (RBS), a significant reproductive disease in dairy cattle. For a very long time, repeat breeding has been regarded as one of the most critical reproductive issues in cattle. The objective of this study is to investigate the frequency and identify the risk factors related to repeat breeding in dairy cows in the Bogura district of Bangladesh. Additionally, the study aims to assess the influence of repeat breeding on reproductive performance in this population. This study collected indigenous and crossbred 179 cow's data using a pre-structured questionnaire. The cows that needed more than three consecutive inseminations to conceive were considered repeat breeders, and those that needed ≤3 inseminations were regular cyclic cows. The incidence rate of RBS in this study was 33.50%. In BCS 2.5 to 3.0, the incidence rate was significantly higher (58.30%) in repeat breeders than in others. Cows with &lt; 5-litre average daily milk production and reared in intensive farming systems with moderate to poor levels of hygienic management have a significant (p&lt;0.005) effect of repeat breeding syndrome. Different reproductive diseases have a significant (p&lt;0.001) effect on the conception rate of cows. Stillbirth (77.87%) followed by fetal death (76.47%) were recorded as major reproductive obstacles in repeat breeding, whereas pyometra (71.43%), followed by abortion (66.67%), dystocia (70.00%) and endometritis (57.14%) were the major recorded complications in repeat breeders. The rate of conception would go up if cows had optimal BCS, good hygiene and management practices were used, and farmers were trained on how to manage cattle reproduction. This would lower the repeat breeding syndrome.

Evaluation of later timepoints for fixed-time artificial insemination of beef heifers and cows when using sex-sorted semen

Two experiments were designed to evaluate later timepoints for fixed-time artificial insemination (FTAI) of beef heifers and cows, with the hypothesis that use of a later timepoint would allow a greater proportion of animals to express estrus prior to FTAI and result in greater conception rates among estrous females inseminated with sex-sorted semen. In Experiment 1, estrus was synchronized for 1640 heifers using the 14 d CIDR-PG protocol: insertion of an intravaginal progesterone-releasing insert (CIDR; 1.38 g progesterone) on Day −33 and removal on Day −19, and administration of prostaglandin F2α (PG; 500 μg cloprostenol sodium) on Day −3. Heifers were inseminated at one of three FTAI timepoints: 66 h, 70 h, or 74 h after PG administration. In Experiment 2, estrus was synchronized for 414 beef cows using the 7 & 7 Synch protocol: administration of PG coincident with CIDR insertion on Day −17, gonadotropin-releasing hormone (GnRH; 100 μg gonadorelin) on Day −10, and PG coincident with CIDR removal on Day −3. Cows were inseminated at one of two FTAI timepoints: 66 h or 72 h after PG administration. In both experiments, only animals that expressed estrus prior to FTAI were inseminated with sex-sorted semen. In Experiment 1, the proportion of heifers that expressed estrus prior to FTAI (66 h: 62 %; 70 h: 67 %; 74 h: 71 %) was greater when FTAI was performed at 74 h versus 66 h (P = 0.0097); however, conception rate of heifers that expressed estrus and were serviced with sex-sorted semen did not differ among treatments (P = 0.67; 66 h: 56 %; 70 h: 53 %; 74 h: 53 %). In Experiment 2, the proportion of cows expressing estrus prior to FTAI did not differ between treatments (P = 0.30; 66 h: 71 %; 72 h: 76 %). Additionally, conception rate of estrous cows inseminated with sex-sorted semen did not differ between treatments (P = 0.24; 66 h: 45 %; 72 h: 40 %). These results indicate that performing FTAI later following the 14 d CIDR-PG protocol increases the proportion of heifers that express estrus and are serviced with sex-sorted semen but does not improve conception rates. Later timing of FTAI following the 7 & 7 Synch protocol was not observed to increase the proportion of cows expressing estrus prior to FTAI or improve conception rates among estrous cows inseminated with sex-sorted semen. Together, these results provide further insight into optimal timing of FTAI when using sex-sorted semen.

Combined single-step evaluation of functional longevity of dairy cows including correlated traits

BackgroundFor years, multiple trait genetic evaluations have been used to increase the accuracy of estimated breeding values (EBV) using information from correlated traits. In France, accurate approximations of multiple trait evaluations were implemented for traits that are described by different models by combining the results of univariate best linear unbiased prediction (BLUP) evaluations. Functional longevity (FL) is the trait that has most benefited from this approach. Currently, with many single-step (SS) evaluations, only univariate FL evaluations can be run. The aim of this study was to implement a “combined” SS (CSS) evaluation that extends the “combined” BLUP evaluation to obtain more accurate genomic (G) EBV for FL when information from five correlated traits (somatic cell score, clinical mastitis, conception rate for heifers and cows, and udder depth) is added.ResultsGEBV obtained from univariate SS (USS) evaluations and from a CSS evaluation were compared. The correlations between these GEBV showed the benefits of including information from correlated traits. Indeed, a CSS evaluation run without any performances on FL showed that the indirect information from correlated traits to evaluate FL was substantial. USS and CSS evaluations that mimic SS evaluations with data available in 2016 were compared. For each evaluation separately, the GEBV were sorted and then split into 10 consecutive groups (deciles). Survival curves were calculated for each group, based on the observed productive life of these cows as known in 2021. Regardless of their genotyping status, the worst group of heifers based on their GEBV in 2016 was well identified in the CSS evaluation and they had a substantially shorter herd life, while those in the best heifer group had a longer herd life. The gaps between groups were more important for the genotyped than the ungenotyped heifers, which indicates better prediction of future survival.ConclusionsA CSS evaluation is an efficient tool to improve FL. It allows a proper combination of information on functional traits that influence culling. In contrast, because of the strong selection intensity on young bulls for functional traits, the benefit of such a “combined” evaluation of functional traits is more modest for these males.

Genetic and Managerial Factors Affecting the Conception Rate of Cows in Rajshahi City Corporation Area of Bangladesh

Given the significant economic importance of getting cows pregnant, we investigated the factors affecting the conception rate of cows in Rajshahi City in this study. As we know, when the sperm fertilizes the egg, this is the moment we call conception. The number of dams that actually give birth compared to the number of dams that have been served or exposed to the sire is traditionally understood to be the conception rate. There have been many management and environmental factors, such as nutrition, metabolic disorders, reproductive health, heat detection, insemination practices, and climate, which can result in significant differences in conception rates. In terms of the effect of herd size on cow’s conception, we observed that herd with &gt;30 cows had the highest (71.12%) conception rate (P&lt;0.001), while the overall conception rate was 60.28%. Private farms showed higher conception (66.68%) than NGO-led ones (22%). Farmers having higher (&gt;3 years) experience managed better conception rate (62.34%) in their farms. Cows under good housing management showed better conception (65.65%) than poorly or on-averagely maintained ones. Cows that were given good quality feed showed better conception (66.82%) compared to those provided with medium to poor quality feed; likewise, cows supplied with good quality fodder performed better regarding CR (63.68%). Cows that were under regular deworming resulted better (63.90%) conception rate compared to irregularly (55%) or no-dewormed (22.22%) groups. Regarding the effects of breed on CR we noticed that Friesian crossed showed better conception (75.13%) than local (50%) and Sahiwal crossed (40%). About the effect of age, 4-6 years old cows showed a better conception rate (68.88%), and in terms of parity 3rd one revealed highest conception rate (84.26%). We noticed frozen semen performed better (62.43%) than liquid ones (57.24%) and the govt. supplied semen resulted in better CR (65%). Heat detection through mounting resulted in a better conception rate (68.08%) than bellowing (67.14%) and vaginal discharge (52.57%), and service around 12-18 hours of Heat showed the highest conception rate (76.32%). In terms of the effect of methods of pregnancy detection on conception rate we noticed that by observing the clinical signs, we can better confirm conception (70.69%) compared with rectal palpation (38.14%). Under various limitations, we carried out our experiment; our findings are striking; however, further studies are needed to go more in-depth into it

Optimum Time of Insemination after Onset of Oestrus in Holstein – Friesian Dairy Cows in the Peri-urban Khartoum (Sudan)

The aim of this study was to determine the optimum time of insemination after onset of oestrus in Holstein-Friesian dairy cows. 146 and 92 Cows were randomly assigned to the control and prostaglandin F2α treated groups respectively. The experimental animals were then visually observed for oestrus for a period of twelve months. 188 and 99 inseminations were given to the control and prostaglandin F2α treated groups respectively. The inseminations were given at time intervals of 1-6, 7-12, 13-18, and 19-24 hours after onset of oestrus during winter, hot dry summer and hot wet summer. During the three seasons, inseminations were carried out in cows at postpartum interval of 41-60, 61-80, 81-100, 101-120, 121 and over days. The trial was conducted in Cows at parities 1 and 2 as a group, and parities 3 and over as a separate group. The optimum time of insemination to achieve the highest conception rates was at 13-18 hours in the control group of Cows. Winter had the highest conception rates compared to other seasons. Cows at postpartum intervals of 121 and over days had the highest conception rates. Conception rates in cows at parities 1 and 2 had the highest conception rate compared to other parities. The present study revealed that the control group of cows had the highest conception rates when inseminations were at 13 – 18 hours after onset of oestrus compared to prostaglandin F2α treated cows.

Review on performance responses of dairy cattle against thermal stress

This manuscript is aimed at reviewing the performance responses of dairy cattle against thermal stress resulting from climate change. Climate change is the major factor that largely affects the dairy industry. Thermal stress (TS) is the perceived discomfort and physiological strains associated with exposure to excessive ambient temperature. Temperature and Humidity Index (THI) have been adopted to describe thermal conditions that drive thermal stress in dairy cattle. The effects of TS are devastating in the dairy industry if not managed well. The thermo-neutral zone for dairy cattle and calves in the tropics is THI &lt;72. Milk yield reductions of up to 50% have been reported for Holstein cows due to thermal stress under summer climate conditions. Moreover, thermal stress is associated with alterations in milk composition. TS reduces the length and intensity of estrus manifestation. Moreover, 80% of estrus may be unnoticeable during the summer season in temperate regions, which further reduces fertility. Conception rates of dairy cows may drop up to 20–27% in the summer season. Climate-induced thermal stress resulted in a decrease of 3.5 kg and 25 kg in the birth weight and weaning weight of Fogera calves, respectively. Dry matter feed intake was reduced by 9.6%. Commonly used thermal stress reduction strategies included modification of the physical environment, breeding for heat-tolerant dairy cattle, and nutritional management. The productive and reproductive traits are susceptible to the negative impacts of thermal stress with an increase in THI above 68.0 for Holstein Frisian cattle and their crosses and 72 for tropical cattle under an open shed system. Mitigations of thermal stress by breeding heat-tolerant animals, using a loose house system, and season-based feeding should be considered an integral component of the dairy cattle management system.

Genomic evaluation of late-term abortion in cows recorded through Dairy Herd Improvement test plans

Late-term abortions cause significant economic loss and are of great concern for dairy herds. Late-term abortions >152 d and <251 d of gestation that terminate a lactation or initiate a new lactation have long been recorded by Dairy Herd Improvement (DHI). For 24.8 million DHI lactations, the average recorded incidence of late-term abortions across all years (2001–2018) was 1.2%. However, the 1.3% incidence of abortions reported in 2012 has declined to <1.0% incidence since 2015. Small adjustments were applied to the 82 million daughter pregnancy rate (DPR), 29 million cow conception rate (CCR), and 9 million heifer conception rate (HCR) records to account for late-term abortions more accurately. Fertility credits for CCR and HCR were changed to treat the last breeding as a failure instead of success if the next calving was coded as a late-term abortion. Similarly, when computing DPR, days open is now set to the maximum value of 250 instead of the reported days open if the next reported calving is an abortion. The test of these changes showed very small changes in standard deviation and high correlations (0.997) of adjusted predicted transmitting abilities (PTA) with official PTA from about 20,000 Holstein bulls born since 2000 with >50% reliability. For late-term abortion as a trait, estimated heritability was only 0.001 and PTA had a standard deviation of only 0.1% for recent sires with high reliability (>75%). Young animal genomic PTA have near 50% reliability but range only from −0.5 to +0.4 because of the low incidence and heritability. Genetic trend was slightly favorable and late-term abortion PTA were correlated favorably by 0.27 with net merit, 0.49 with productive life, 0.33 with livability, 0.23 with CCR, 0.20 with HCR, 0.26 with DPR, −0.31 with somatic cell score, −0.24 with daughter stillbirth, and −0.26 with daughter dystocia. Thus, PTA for late-term abortions should not be needed as a separate fertility trait and instead these minor edit changes should suffice. The PTA for late-term abortions would add little value because national evaluations for current fertility traits already account for those economic losses.

A Million-Cow Genome-Wide Association Study of Three Fertility Traits in U.S. Holstein Cows.

A genome-wide association study (GWAS) of the daughter pregnancy rate (DPR), cow conception rate (CCR), and heifer conception rate (HCR) using 1,001,374-1,194,736 first-lactation Holstein cows and 75,140-75,295 SNPs identified 7567, 3798, and 726 additive effects, as well as 22, 27, and 25 dominance effects for DPR, CCR, and HCR, respectively, with log10(1/p) > 8. Most of these effects were new effects, and some new effects were in or near genes known to affect reproduction including GNRHR, SHBG, and ESR1, and a gene cluster of pregnancy-associated glycoproteins. The confirmed effects included those in or near the SLC4A4-GC-NPFFR2 and AFF1 regions of Chr06 and the KALRN region of Chr01. Eleven SNPs in the CEBPG-PEPD-CHST8 region of Chr18, the AFF1-KLHL8 region of Chr06, and the CCDC14-KALRN region of Chr01 with sharply negative allelic effects and dominance values for the recessive homozygous genotypes were recommended for heifer culling. Two SNPs in and near the AGMO region of Chr04 that were sharply negative for HCR and age at first calving, but slightly positive for the yield traits could also be considered for heifer culling. The results from this study provided new evidence and understanding about the genetic variants and genome regions affecting the three fertility traits in U.S. Holstein cows.

Factors affecting first service conception rate in Holstein cows synchronized with double-ovsynch

Factors affecting first service conception rate in Holstein cows synchronized with double-ovsynch

Perspective: Can early embryonic losses be reduced in lactating dairy cows?

Perspective: Can early embryonic losses be reduced in lactating dairy cows?

Relation between body condition score and conception rate of Japanese Black cows.

This study analyzes interactions of body condition score (BCS) with other factors and the effect of BCS on estimates of genetic paremeters of conception rate (CR) in Japanese Black cows. Factors affecting CR were analyzed through the linear mixed model, and genetic parameters of CR were estimated through the threshold animal model. The interactions between BCS and each season and the number of artificial inseminations (AI) was significant (p<0.05), but that between BCS and parity showed no significance for CR. High CR was observed with BCS 3 in autumn (0.56±0.01) and BCS 4 in summer (0.56±0.02). The highest CR with BCS 3 (0.56±0.02) and BCS 4 (0.55±0.01) was observed at first AI. With BCS 5, however, the highest CR (0.55±0.08) was observed at second AI. The model with BCS was notably conducive to the estimation of genetic parameters because of a low deviance information criterion of heritability that, nevertheless, was slightly lower than the model without BCS.

The parity affects the relationship between the insemination-ovulation interval and the conception rate in lactating dairy cows.

The aim of the present study was to investigate the relationship between parity and the optimal insemination-ovulation interval (IOI) in lactating dairy cows, as well as the relationship between the optimal timing of artificial insemination (AI) based on the onset of estrus and parity. A total of 183 postpartum lactating Holstein cows participated in the study and underwent 522 AI procedures using unsorted frozen semen between 2011 and 2018. Transrectal ultrasound was used to detect ovulation times in 326 AI procedures, and a pedometer was used to detect estrus onset times in 470 AI procedures. An analysis was also performed on data from 265 AI procedures in which all the times of estrus onset, estrus end, and ovulation were detected. The results showed that ovulation occurring 6-12 hr after AI was associated with the numerical highest conception rate in multiparous cows. Moreover, the conception rate was higher when ovulation occurred between 6 and 12 hr after AI than when it occurred between 0 and 6 hr or 18 and 24 hr after AI. In contrast, the effect of IOI on the conception rate in primiparous cows was insignificant. There was no effect of AI timing based on the estrus onset on the conception rate in either primiparous or multiparous cows. Furthermore, the interval from estrus onset to ovulation was similar in primiparous and multiparous cows. The difference in optimal IOI between primiparous and multiparous cows may be due to the larger uterus size in multiparous cows. These findings suggest that the optimal timing for AI in multiparous cows is more restricted than in primiparous cows. Therefore, it is essential to carefully determine the timing of AI when it is performed in multiparous cows.

003 Sire conception rate in dairy and beef cows submitted to timed artificial insemination with sexed and unsexed semen

003 Sire conception rate in dairy and beef cows submitted to timed artificial insemination with sexed and unsexed semen

Induced endometritis in early lactation compromises production and reproduction in dairy cows

Objectives of this experiment were to study the effect of infusing utero-pathogenic bacteria to induce endometrial inflammation on productive performance in early lactation and subsequent reproduction. Although endometritis is associated with perturbed reproduction, numerous factors may contribute to the observed association. It was hypothesized that induced endometrial inflammation, resulting in localized and systemic inflammatory responses, compromises production and reproduction. Holstein cows without clinical disease and with less than 18% polymorphonuclear leukocytes (PMN) in endometrial cytology on d 31 ± 3 postpartum had their estrous cycle synchronized. Cows were blocked by parity and genomic breeding value for cow conception rate and, within block, assigned randomly to remain as untreated controls (CON; n = 37) or to receive an intrauterine infusion of 5.19 × 108 cfu Escherichia coli and 4.34 × 108 cfu Trueperella pyogenes during the luteal phase to induce endometrial inflammation (INF; n = 48). Endometrial cytology was taken on d 2 and 7 after treatment to evaluate the proportion of PMN. Rectal temperature, dry matter intake, and yields of milk and components were measured in the first 7 d after treatment. Blood serum was analyzed for concentration of haptoglobin. Leukocytes were isolated from blood on d 2 and 7 after treatment and on d 19 after artificial insemination (AI) and mRNA was quantified for a select group of genes. Cows received AI and reproduction was followed for 300 d postpartum. Bacterial infusion induced endometrial inflammation with increased proportions of PMN in the endometrial cytology on d 2 (4.4 ± 0.7 vs. 26.3 ± 2.8%) and 7 (10.9 ± 1.7 vs. 17.4 ± 2.1%) after treatment, resulting in increased mean prevalence of subclinical endometritis (>10% PMN; 23.3 ± 6.3 vs. 80.9 ± 5.1%). Rectal temperature did not differ between CON and INF, but the concentration of haptoglobin in serum tended to increase in INF compared with CON (113 ± 14 vs. 150 ± 16 µg/mL). Induced endometrial inflammation reduced yields of milk (44.9 ± 0.8 vs. 41.6 ± 0.8 kg/d), protein (1.19 ± 0.03 vs. 1.12 ± 0.03 kg/d), and lactose (2.17 ± 0.04 vs. 2.03 ± 0.04 kg/d) and tended to reduce dry matter intake (20.7 ± 0.5 vs. 19.4 ± 0.6 kg/d) in the first 7 d after treatment. Indeed, the reduction in milk yield lasted 4 wk. However, treatment did not affect yields of energy-corrected milk or fat because treatment with INF increased the concentration of fat in milk (3.54 ± 0.10 vs. 3.84 ± 0.10%). Induced endometrial inflammation reduced pregnancy per AI at all inseminations (33.4 ± 5.1 vs. 21.6 ± 3.7%) and the hazard of pregnancy (0.61; 95% CI = 0.36-1.04), which extended the median days open by 24 d. Blood leukocytes from INF cows had increased mRNA expression of the pro-inflammatory gene IL1B on d 2 and 7 after treatment, but reduced expression of the IFN-stimulated genes ISG15 and MX2 on d 19 after AI. Induced endometrial inflammation depressed production and caused long-term negative effects on reproduction in lactating dairy cows.