Sire Conception Rate Research Articles

Delineating marker genotypes for higher reproduction performance to aid in selection of Murrah bulls

Unraveling the genetic variability of performance traits is the key basis of selection in farm animals. Murrah is a predominant milch breed of India, efforts were being made in the past to select them for higher production, which is negatively related with the fertility. Keeping this fact in mind and to select the animals having optimum production and fertility performance, present study was conducted to validate suitable markers and the association of their allelic variation with the fertility traits in Murrah buffaloes. Study was conducted on 280 Murrah buffaloes to explore SNPs in SPEF2 gene and their association with sire conception rate (SCR), conception rate (CR) and weight at birth of Murrah bulls. Results revealed that SNP C168T of SPEF2 gene with genotype CC was found to have non-significant but higher CR and SCR in comparison to CT and TT genotype. Although no significant association of the identified SNPs could be established with bull fertility traits, a further study with a large number of samples could make the differences due to genotypes a significant effect and can be used as an aid for early selection of high fertile Murrah bulls

Factors influencing pregnancy loss between days 30 and 70 in a single cattle herd: A comprehensive analysis of sire, cow, and other contributing factors

This retrospective study utilized a mixed-effects logistic model analysis to investigate variables associated with the probability of pregnancy loss (PL) between days 30 and 70 in a dataset comprising 9507 pregnancies from a single cattle herd over 10 years. The model incorporated fixed-effect variables including cow breed (Holstein, Crossbred, and Brown Swiss), parity (1st, 2nd, 3rd, and 4th or more), insemination seasons, insemination number (≤3 vs >3), estrus nature (spontaneous vs synchronized), postpartum problems, sire breed (Holstein, Fleckvieh, Brown Swiss, and Montbéliarde), zygote genotypic (pure vs crossbred), days in milk (DIM) at insemination, actual 305-day milk yield, and sire conception rate. Additionally, random effects included sire (n = 129), cow (n = 3463), and production years (n = 10). The results revealed that cows inseminated with Brown Swiss sires or sires with lower initial conception rates had higher PL rates. Biparous cows, cows with lower 305-day milk yield, cows inseminated later in DIM, cows receiving the 4th or subsequent insemination, and cows inseminated during winter or autumn had lower PL rates. The estrus type and zygote genotype did not significantly impact PL. The random effects of cow, sire, and production years were estimated at 0.230, 0.054, and 0.112, respectively. In conclusion, the study findings suggested that improving management practices for high-yielding cows, cows in early lactation stages, and cows exposed to thermal stress conditions, along with utilizing Brown Swiss cows and sires with high initial conception rates per insemination, could potentially decrease overall PL rates on the farm. Nonetheless, the results did not support the use of Crossbred cows, sires from different breeds, or specific sires to mitigate PL rates on the farm.

Genomic prediction of male fertility in Brown Swiss cattle

Bull fertility has been recognized as an important factor affecting dairy herd fertility. The objective of this study was to assess the feasibility of predicting male fertility in Brown Swiss cattle using genomic data. The data set consisted of 1,102 Italian Brown Swiss bulls with sire conception rate (SCR) records and genotype data for roughly 480k SNP. The analyses included the use of linear kernel-based regression models fitting all SNPs or incorporating markers with large effect. Predictive performance was evaluated in 5-fold cross-validation using the correlation between observed and predicted SCR values and mean squared error of prediction. The entire SNP set exhibited predictive correlations around 0.19. Interestingly, the inclusion of 2 markers with large effect yielded predictive correlations around 0.32. Overall, using linear kernel-based models fitting markers with large effect is a promising approach. Our findings could help Brown Swiss breeders make enhanced genome-guided management and selection decisions on male fertility.

Identification of runs of homozygosity associated with male fertility in Italian Brown Swiss cattle.

Intensive selection for improved productivity has been accompanied by an increase in inbreeding rates and a reduction in genetic diversity. The increase in inbreeding tends to impact performance, especially fitness-related traits such as male fertility. Inbreeding can be monitored using runs of homozygosity (ROH), defined as contiguous lengths of homozygous genotypes observed in an individual's chromosome. The goal of this study was to evaluate the presence of ROH in Italian Brown Swiss cattle and assess its association with bull fertility. First, we evaluated the association between ROH and male fertility using 1,102 Italian Brown Swiss bulls with sire conception rate records and 572K SNPs spanning the entire genome. Second, we split the entire population into 100 high-fertility and 100 low-fertility bulls to investigate the potential enrichment of ROH segments in the low-fertility group. Finally, we mapped the significant ROH regions to the bovine genome to identify candidate genes associated with sperm biology and male fertility. Notably, there was a negative association between bull fertility and the amount of homozygosity. Four different ROH regions located in chromosomes 6, 10, 11, and 24 were significantly overrepresented in low-fertility bulls (Fisher's exact test, p-value <0.01). Remarkably, these four genomic regions harbor many genes such as WDR19, RPL9, LIAS, UBE2K, DPF3, 5S-rRNA, 7SK, U6, and WDR7 that are related to sperm biology and male fertility. Overall, our findings suggest that inbreeding and increased homozygosity have a negative impact on male fertility in Italian Brown Swiss cattle. The quantification of ROH can contribute to minimizing the inbreeding rate and avoid its negative effect on fitness-related traits, such as male fertility.

Relationship of field and in vitro fertility of dairy bulls with sperm parameters, including DAG1 and SERPINA5 proteins

IntroductionSperm interacts with the female reproductive tract and oocyte through proteins, and these cell-to-cell interactions may play a role in sperm fertility. For consideration of a protein as a potential marker of fertility, there must be variability expressed among animals. The proteins dystroglycan (DAG1) and plasma serine protease inhibitor (SERPINA5) have been reported to play a role in cell-to-cell interactions. Thus, the objectives of this study were to characterize the localization and abundance variability of DAG1 and SERPINA5 in bovine sperm, and to investigate the relationship of DAG1 and SERPINA5 with field fertility (i.e., sire conception rate; SCR), in vitro embryo production (IVP), and sperm parameters.Material and methodsDairy bulls (n = 22) were classified as high-SCR (SCR &amp;gt; 1.0) or low-SCR (SCR &amp;lt; –4.0), and good [blastocyst (BL)-by-cleavage (CL) ratio (BL/CL) &amp;gt; 39%] or poor (BL/CL &amp;lt; 38%) BL/CL. Sperm was evaluated for DAG1 and SERPINA5 immunolocalization, and concentration in two separate ejaculates. Variance between bulls compared with within bulls was evaluated using a generalized linear model (GLM) procedure. The relationship of SCR and IVP classification on DAG1 and SERPINA5 concentrations, percentage of tail labeled for SERPINA5, SCR, sperm total and progressive motility, sperm plasma membrane integrity (PMI), CL, BL, and BL/CL were evaluated with the GLIMMIX procedure, and the correlations between these variables were evaluated.ResultsBoth proteins were localized on the sperm head; however, SERPINA5 was also localized on the sperm tail. There was greater variance in concentration among bulls than within bulls for DAG1 (P &amp;lt; 0.0001; 69.4 vs. 49.1, respectively) and SERPINA5 (P &amp;lt; 0.0001; 325.8 vs. 285.4, respectively). There was a positive correlation between the concentrations of DAG1 and of SERPINA5 (P = 0.01; r = 0.54). In addition, the percentage of tail labeled for SERPINA5 was correlated with PMI (P = 0.05; r = 0.44). There was no relationship between SCR and IVP classifications and DAG1 (P ≥ 0.55), SERPINA5 (P ≥ 0.54), or the percentage of sperm tail labeled for SERPINA5 (P ≥ 0.22).DiscussionIn conclusion, DAG1 and SERPINA5 were localized to the sperm head, and SERPINA 5 was also localized to the tail. Concentrations of DAG1 and SERPINA5 on the sperm head were correlated with each other. The percentage of tail labeled for SERPINA5 was correlated with sperm PMI; however, neither protein was associated with SCR or IVP. Thus, when evaluated by immunofluorescent microscopy, DAG1 and SERPINA5 concentrations are variable and are not good fertility markers for bull sperm.

Improving national fertility evaluations by accounting for the rapid rise of embryo transfer in US dairy cattle

Dairy producers have improved fertility of their herds by selecting bulls with higher conception rate evaluations. This research was motivated by the rapid increase in embryo transfer (ET) use to 11% of recent births and >1 million total births, with >5 times as many ET calves born in the United States in 2021 compared with just 5 yr earlier. Historical data used in genetic evaluations are stored in the National Cooperator Database. Recent records in the national pedigree database revealed that only 1% of ET calves have corresponding ET records in the breeding event database, 2% are incorrectly reported as artificial inseminations, and 97% have no associated breeding event. Embryo donation events are also rarely reported. Herd years reporting >10% of calves born by ET but less than half of the expected number of ET breeding events were removed to avoid potential biases. Heifer, cow, and sire conception rate evaluations were recalculated with this new data set according to the methods used for the official national evaluations. The edits removed about 1% of fertility records in the most recent 4 yr. Subsequent analysis showed that censoring herd years with inconsistent ET reporting had little effect on most bulls except for the highest ranking, younger bulls popular for ET use, and with largest effects on genomic selection. Improved ET reporting will be critical for providing accurate fertility evaluations, especially as the popularity of these advanced reproductive technologies continues to rise.

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

Integrating sperm cell transcriptome and seminal plasma metabolome to analyze the molecular regulatory mechanism of sperm motility in Holstein stud bulls.

Considering that artificial insemination is the most widely used assisted reproductive technique in the dairy industry, the semen quality of bulls is very important for selecting excellent stud bulls. Sperm motility is one of the important traits of semen quality, and related genes may be regulated by environmental factors. Seminal plasma can affect sperm cell transcriptome and further affect sperm motility through exosome or other processes. However, the molecular regulation mechanism of bull sperm motility has not been studied by combining the sperm cell transcriptome with seminal plasma metabolome. The number of motile sperm per ejaculate (NMSPE) is an integrated indicator for assessing sperm motility in stud bulls. In the present study, we selected 7 bulls with higher NMSPE (5,698.55 million +/- 945.40 million) as group H and 7 bulls with lower NMSPE (2,279.76 million +/- 1,305.69 million) as group L from 53 Holstein stud bulls. The differentially expressed genes (DEGs) in sperm cells were evaluated between the two groups (H vs. L). We conducted gene co-expression network analysis (WGCNA) on H and L groups of bulls, as well as two monozygotic twin Holstein bulls with different NMSPE values, to screen candidate genes for NMSPE. The regulatory effect of seminal plasma metabolome on the candidate genes of NMSPE was also investigated. A total of 1,099 DEGs were identified in the sperm cells of H and L groups. These DEGs were primarily concentrated in energy metabolism and sperm cell transcription. The significantly enriched Kyoto encyclopedia of genes and genomes (KEGG) pathways of the 57 differential metabolites were the aminoacyl-tRNA biosynthesis pathway and vitamin B6 metabolism pathway. Our study discovered 14 genes as the potential candidate markers for sperm motility, including FBXO39. We observed a broad correlation between transcriptome of sperm cells and seminal plasma metabolome, such as three metabolites, namely, mesaconic acid, 2-coumaric acid, and 4-formylaminoantipyrine, might regulate FBXO39 expression through potential pathways. The genes related to seminal plasma metabolites expressed in sperm cells are not only located near the quantitative trait loci of reproductive traits, but also enriched in the genome-wide association study signal of sire conception rate. Collectively, this study was the first to investigate the interplays among transcriptome of sperm cells and seminal plasma metabolome from Holstein stud bulls with different sperm motility.

Deciphering the genetic basis of male fertility in Italian Brown Swiss dairy cattle

Improving reproductive performance remains a major goal in dairy cattle worldwide. Service sire has been recognized as an important factor affecting herd fertility. The main objective of this study was to reveal the genetic basis of male fertility in Italian Brown Swiss dairy cattle. Dataset included 1102 Italian Brown Swiss bulls with sire conception rate records genotyped with 454k single nucleotide polymorphisms. The analysis included whole-genome scans and gene-set analyses to identify genomic regions, individual genes and genetic mechanisms affecting Brown Swiss bull fertility. One genomic region on BTA1 showed significant additive effects. This region harbors gene RABL3 which is implicated cell proliferation and motility. Two genomic regions, located on BTA6 and BTA26, showed marked non-additive effects. These regions harbor genes, such as WDR19 and ADGRA1, that are directly involved in male fertility, including sperm motility, acrosome reaction, and embryonic development. The gene-set analysis revealed functional terms related to cell adhesion, cellular signaling, cellular transport, immune system, and embryonic development. Remarkably, a gene-set analysis also including Holstein and Jersey data, revealed significant processes that are common to the three dairy breeds, including cell migration, cell–cell interaction, GTPase activity, and the immune function. Overall, this comprehensive study contributes to a better understanding of the genetic basis of male fertility in cattle. In addition, our findings may guide the development of novel genomic strategies for improving service sire fertility in Brown Swiss cattle.

Identificación del polimorfismo aquaporin 7 Gene y fertilidad in vivo de búfalos en Egipto

This work aimed to investigate the genetic polymorphism of Aquaporin 7 (AQP7) gene and its association with the in-vivo fertility of Egyptian buffalo bulls. A total of 188 fresh semen ejaculates were collected from 47 buffalo bulls and subjected to semen evaluation. The bulls were grouped according to in-vivo fertility relying on sire conception rate (SCR) into high (SCR&gt;50%, n=41) and low (SCR&lt;50%, n=6) fertile bulls. DNA was extracted from semen and a 200 bp fragment of the AQP7 gene was amplified by PCR. The genetic polymorphism of AQP7 gene was detected by restriction fragment length polymorphism, the single strand conformation polymorphism and the nucleotide sequencing. The results revealed that SCR was significantly (p&lt;0.001) increased in high (71.4±1.3) than low (44.7±2.8) fertile bulls while the ejaculate volume, individual motility%, lives sperm%, sperm concentration and sperm abnormalities showed a non-significant difference in both groups. The AQP7 gene showed no genetic variation in all bulls. The alignment of the resultant sequence with buffalo AQP7 gene sequence (ID: XM_006066699.2) showed 100% identity (122/122), however, deletion of A49 was discovered when the sequence was aligned with ID: XM_006066700.2 of buffalo in GenBank. In conclusion, the sire conception rate is not associated with any genetic variation in Aquaporin 7 gene. The Aquaporin 7 gene could be a highly conserved sequence in Egyptian buffalo bulls. Future research on large herd populations in different regions of AQP7 gene is required for evaluating the AQP7 gene polymorphism and its association with the fertility of Egyptian buffalo bulls.

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

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 &amp;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 &amp;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.

PSV-5 Relationship between sire conception rate, sperm motility, sperm SERPINA5 relative concentration, and in vitro produced embryos in dairy bulls

Abstract Sire conception rate (SCR) is a field measure of fertility among bulls, but it can be influenced by several factors (Sperm transport, sperm-egg binding, early embryo development, etc). The objective of this study was to evaluate the relationship between SCR, sperm motility, SERPINA5 concentrations, and in vitro embryo development. Measurements were performed in 19 bulls with SCR values ranging from -7.7 to 4.45. For each bull, an aliquot of frozen-thawed semen was used for analyses of total (TMOT) and progressive (PROG) motility. Remaining semen was fixed with 2% formaldehyde, and concentration of SERPINA5 was determined by immunolocalization (antibody SERPINA5/Dylight405; PA5-79976-Invitrogen / ab201798-Abcam). Mean fluorescence intensity was determined in ~200 sperm heads/bull. Approximately 149 oocytes/bull were fertilized in vitro for embryo development analysis (cleavage and blastocyst rates). Statistical procedures were performed in SAS (9.4) using the procedures CORR for correlations (SCR, TMOT, PROG, SERPINA5, cleavage and blastocyst) and GLIMMIX for comparison of “field-fertility” (SCR divided in HIGH or LOW) and “field-embryo-fertility” (LOW-SCR sires were divided based on blastocyst rate (HIGH or LOW) resulting in two classifications; LOW-HIGH≥31% and LOW-LOW≤26%, respectively). There were positive correlations (P &amp;lt; 0.05) between cleavage-blastocyst (r=0.50), SERPINA5-cleavage (r=0.48), and TMOT-PROG (r=0.76). Sire SCR was not associated with SERPINA5, TMOT, PROG, cleavage and blastocyst rate (P &amp;gt; 0.52). Among LOW-SCR sires, LOW-LOW sires (-4.83±0.60) tended to have a better SCR score than LOW-HIGH (-6.18±0.42) sires (P = 0.08), but there were no differences (P &amp;gt; 0.43) between LOW-HIGH, LOW-LOW, and HIGH sires for SERPINA5, TMOT, PROG, and cleavage. In conclusion, some LOW SCR sires have good embryo development indicating a different mechanism for their low SCR; however, these differences in SCR could not be explained by TMOT, PROG, SERPINA5, cleavage and blastocyst. There were, however, positive correlations between cleavage-blastocyst rate, and SERPINA5-cleavage rate.

265 Awardee Talk: Maternal and Paternal Contributions to Fertility

Abstract Using over 56,000 pregnancy diagnostic records in beef cattle, a meta-analysis was conducted to objectively determine that 28.4 % of embryos will not develop past day 7 of gestation with most embryonic losses occurring before day 4. Furthermore, by day 30 of gestation, 47.9 % of cows submitted to a single insemination at day 0 will not be pregnant and pregnancy loss between days 32 and 100 was 5.8%. Reproductive success, however, is highly variable and influenced by maternal and paternal factors. Maternal characteristics, including subspecies, parity and reproductive tract size, intersect with breeding management decisions regarding estrus expression and detection to influence conception and pregnancy rates. The maternal endocrine environment, from estradiol associated with estrus around fertilization to elevated prostaglandins during the embryonic to fetal transition period, play critical roles in pregnancy success. Despite the numerous maternal factors involved with pregnancy establishment, sire contribution to reproductive failure should not be overlooked. Sires are reported to influence pregnancy loss during the second month of gestation in both beef and dairy herds. These differences in sire field fertility could not be explained by differences in semen characteristics nor differences in sire conception rate (SCR) score. To understand parental contribution to pregnancy development during the second month of gestation we developed parthenogenetic (PA) embryos (embryos lacking paternal genome). We observed that PA conceptus had well developed trophectoderm tissue at day 31 of gestation but no site of embryo attachment to the endometrium. Moreover, conceptus secretion such as pregnancy-associated glycoproteins and interferon-stimulated genes were not found in maternal circulation. These results suggest that paternal genetics is required for post-elongated embryo attachment to endometrium. Further exploring the maternal vs paternal contribution to pregnancy development can help elucidate the mechanism that drives reproductive failure in cattle.

Evaluation of bull fertility in Italian Brown Swiss dairy cattle using cow field data

Dairy bull fertility is traditionally evaluated using semen production and quality traits; however, these attributes explain only part of the differences observed in fertility among bulls. Alternatively, bull fertility can be directly evaluated using cow field data. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. We then estimated sire conception rate using only factors related to the bull. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between high-fertility and low-fertility bulls. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.

Targeted sequencing reveals candidate causal variants for dairy bull subfertility.

SummaryBull fertility is a key factor for successful reproductive performance in dairy cattle. Since the semen from a single bull can be used to inseminate hundreds of cows, one subfertile bull could have a major impact on herd reproductive efficiency. We have previously identified five genomic regions, located on BTA8 (72.2 Mb), BTA9 (43.7 Mb), BTA13 (60.2 Mb), BTA17 (63.3 Mb), and BTA27 (34.7 Mb), that show large dominance effects on bull fertility. Each of these regions explained about 5–8% of the observed differences in sire conception rate between Holstein bulls. Here, we aimed to identify candidate causal variants responsible for this variation using targeted sequencing (10 Mb per region). For each genomic region, two DNA pools were constructed from n≈20 high‐fertility and n≈20 low‐fertility Holstein bulls. The DNA‐sequencing analysis included reads quality control (using FastQC), genome alignment (using BWA and ARS‐UCD1.2), variant calling (using GATK) and variant annotation (using Ensembl). The sequencing depth per pool varied from 39× to 51×. We identified a set of nonsense mutations, missense mutations, and frameshift variants carried by low‐fertility bulls. Notably, some of these variants were classified as strong candidate causal variants, i.e., mutations with deleterious effects located on genes exclusively/highly expressed in testis. Genes affected by these candidate causal variants include AK9, TTLL9, TCHP, and FOXN4. These results could aid in the development of novel genomic tools that allow early detection and culling of subfertile bull calves.

Effect of glucose concentration and cryopreservation on mitochondrial functions of bull spermatozoa and relationship with sire conception rate

Mitochondrial function is essential for sperm viability, not only from a sperm metabolism perspective, but also for improvement of sperm storage in liquid and frozen states. Bull sperm have notable metabolic variability with energy production for motility and subsequently for fertilizing capacity resulting from both glycolysis and oxidative phosphorylation. The objective of this study was to determine mitochondrial function of sperm using high-throughput Seahorse Analyzer technology in fresh semen and subsequent to freezing-thawing when there was incubation in media commonly used for sperm storage (relatively large glucose concentration) and female tract (relatively small glucose concentration). Additionally, there were determinations whether there were differences in values for fertility variables by regressing sire conception rate on values for mitochondrial variables when there was evaluation of semen from bulls with varying fertility. Media with larger concentrations of glucose inhibited mitochondrial function in fresh sperm, as indicated by less maximal oxygen consumption, spare respiratory capacity and coupling efficiency when compared to sperm in the media containing less glucose. Furthermore, there was greater (P < 0.05) mitochondrial function in cryopreserved-thawed compared to fresh samples with there being no effect of incubation media. These results indicate that mitochondrial damage from cryopreservation cannot be simply overcome post-thawing with glucose supplementation of bull semen incubation media. The increase in mitochondrial function is likely due to “non-productive” oxygen consumption to maintain the mitochondrial proton gradient. Furthermore, there was a negative association of mitochondrial proton leakage with sire conception rate indicating this could be a potential biomarker of bull fertility.

113 Genetics Industry Infrastructure: How Are Artificial Insemination Organizations Adapting to Changes in the Beef Industry?

Abstract Cattle artificial insemination (AI) organizations are adapting quickly to changes within the beef industry domestically and abroad. Specifically, the increasing utilization of beef bulls, predominately Angus, in dairy herds to create terminal crossbred calves for beef underlies the majority of the changes and challenges. The procurement, management, and collection of beef sires on a commercial scale has become commonplace for AI organizations, and the subsequent optimization of beef sire housing, nutritional requirements, behavior surrounding semen collection, semen production ability, semen quality, and fertility is being examined. At one large AI organization, Angus sires are proving capable of producing as much semen as their dairy counterparts while being collected year-round to meet market demand. However, the percentage of collections that qualify for sale is ≤80% in beef bulls compared to &amp;gt;90% in Holstein bulls based on acceptable semen quality as determined by post-thaw computer-assisted motility analyses, flow cytometric viability assays, and visual sperm morphological assessment (Select Sires, Inc., unpublished). Large numbers of inseminations using beef sires, combined with reliable data recording on dairies, is allowing for precision management tools and sire fertility estimates to be generated. For example, the Council on Dairy Cattle Breeding (CDCB) recently applied the Sire Conception Rate (SCR) evaluation’s statistical model to Angus bulls used to inseminate Holstein cows and reported similar conception rates to Holstein sires used to inseminate Holstein cows (33.8% versus 34.3%, respectively). AI organizations have also begun to implement research, create products, and establish new supply chains to proactively account for dairy farms supplying crossbred or purebred (via embryo transfer) beef animals to calf ranches, feed yards, and packer networks. Examples include purebred commercial beef embryo sales, research on rearing crossbred beef calves, generating novel value-based (grid pricing) markets for crossbred calves, and facilitating traceability programs for packers.

63 Effect of sire conception rate on bovine early embryo development

Currently, the only measure of sire fertility in the bovine is sire conception rate (SCR), which is determined by Day 70 pregnancy diagnosis and not reflective of early embryo development. Therefore, this study aimed to establish the relationship between SCR and early embryo development. In the first experiment, 65 sires of negative (&amp;lt;−1, n=25), average (−1 to 1, n=19), and high (&amp;gt; +1, n=21) SCR were characterised for their ability to produce embryos using an invitro embryo production (IVP) system. For each sire, 100 cumulus–oocyte complexes (COCs) were used. COCs were matured for 22h, fertilized by co-incubation with sperm selected from density gradient centrifugation for 18h, and then placed in culture medium. A sire of known IVP performance was used as a control in each run. Cleavage and blastocyst rates (BL) were measured on Days 3 and 8 post-insemination, respectively. Photographs were taken on Days 3, 5, and 8 to identify arrest stages of non-blastocyst embryos. Sires were ranked based on their blastocyst rate and grouped into quartiles for statistical analysis. Differences in BL were determined by ANOVA using sire, IVP run, and a sire×IVP run interaction. In addition, the correlation between SCR and BL was determined. All data were analysed using SAS software version 9.4 (SAS Institute Inc.). Mean BL between each quartile was significant (P&amp;lt;0.05), with rates ranging from 8 to 22% and 32 to 62% for the lowest and highest quartile, respectively. There was no correlation (P=0.90) between SCR and BL. Arrest stage was measured by subtracting the number of Day-8 blastocysts from, first, embryos that were morulas on Day 5, and then embryos that were 8- to 16-cell stage embryos on Day 5. This method is based on the assumption that embryos closer to the blastocyst stage on Day 5 are more likely to contribute to the Day 8 blastocyst population. The most frequent arrest stage was the 4- to 6-cell stage (39/52 sires). It has been shown that decreased rates of autophagy are associated with embryonic arrest at the 4- to 8-cell stage in humans, leading us to investigate this mechanism in the second experiment. Select high (n=3) and low (n=4) performing sires identified in experiment 1 were used to generate 4- to 6-cell embryos, and autophagy rates were measured using live immunofluorescence with CYTO-ID autophagy dye (n=20 embryos/sire). The mean fluorescent intensity of each embryo was divided by the number of cells within the embryo. Differences in autophagy between high and low sires were determined by ANOVA using SAS. Interestingly, low-performing sires had a significantly higher autophagy rates than high-performing sires (77.8±3.1 vs. 50.0±3.5). This could indicate that embryos produced with low-performing sires had higher levels of stress than their counterparts. In summary, the effect of sire on embryonic development seems to be independent of the SCR classification. The most common arrest stage observed is the 4- to 6-cell stage, right before embryonic genome activation. Further research is required to elucidate the mechanisms by which sires influence pre-implantation development. This research was supported by USDA-NIFA AFRI Competitive Grant No. 2019-67015-28998.

Differentially methylated CpG sites related to fertility in Japanese Black bull spermatozoa: epigenetic biomarker candidates to predict sire conception rate.

For semen suppliers, predicting the low fertility of service bull candidates before artificial insemination would help prevent economic loss; however, predicting bull fertility through in vitro assessment of semen is yet to be established. In the present study, we focused on the methylated CpG sites of sperm nuclear DNA and examined methylation levels to screen new biomarkers for predicting bull fertility. In frozen-thawed semen samples collected from Japanese Black bulls, for which the sire conception rate (SCR) was recorded, the methylation level of each CpG site was analyzed using human methylation microarray. According to regression analysis, 143 CpG sites related to SCR were significantly differentially methylated. Whole genome bisulfite sequence data were obtained from three semen samples and the differentially methylated regions (DMRs) that included the target CpG sites selected by human methylation microarray were confirmed. Using combined bisulfite restriction analysis, fertility-related methylation changes were detected in 10 DMRs. With the exception of one DMR, the methylation levels of these DMRs were significantly different between groups with high fertility (> 50%) and low fertility (< 40%). From multiple regression analysis of methylation levels and SCR, three DMRs were selected that could effectively predict bull fertility. We suggest that these fertility-related differences in spermatozoal methylation levels could be new epigenetic biomarkers for predicting bull fertility.

Marker-assisted selection vis-à-vis bull fertility: coming full circle-a review.

Bull fertility is considered an indispensable trait, as far as farm economics is concerned since it is the successful conception in a cow that provides calf crop, along with the ensuing lactation. This ensures sustainability of a dairy farm. Traditionally, bull fertility did not receive much attention by the farm managers and breeding animals were solely evaluated based on phenotypic predictors, namely, sire conception rate and seminal parameters in bull. With the advent of the molecular era in animal breeding, attempts were made to unravel the genetic complexity of bull fertility by the identification of genetic markers related to the trait. Marker-Assisted Selection (MAS) is a methodology that aims at utilizing the genetic information at markers and selecting improved populations for important traits. Traditionally, MAS was pursued using a candidate gene approach for identifying markers related to genes that are already known to have a physiological function related to the trait but this approach had certain shortcomings like stringent criteria for significance testing. Now, with the availability of genome-wide data, the number of markers identified and variance explained in relation to bull fertility has gone up. So, this presents a unique opportunity to revisit MAS by selection based on the information of a large number of genome-wide markers and thus, improving the accuracy of selection.