A retrospective case series of the surgical management of thirty-one penile fibropapilloma cases presented to University College Dublin Veterinary Hospital (UCDVH) between 2017 and 2023

BACKGROUND

Penile fibropapilloma is a condition caused by bovine papilloma virus and is frequently encountered in young bulls. Penile fibropapillomatosis is thought to be spread through homosexual mounting behaviour. Fibropapillomas of the penis are painful, often bleed and can impede normal intromission. Treatment may range from allowing time for slow, spontaneous regression to surgical resection but recurrence following surgery is reported by some authors.

CASE PRESENTATION

Thirty one bulls that were presented to University College Dublin Veterinary Hospital from March 2017 to March 2023 for surgical resection of penile fibropapillomas were included in this retrospective case series. Twenty-seven of the 31 bulls (87%) were under two years of age. The majority (42%) of bulls presented were Hereford, but Angus, Charolais, Holstein-Friesian and Limousin breeds were also seen. Following examination and diagnosis of penile fibropapilloma, regional anaesthesia (xylazine-procaine epidural and internal pudendal nerve block) and standing surgical intervention (resection and cautery) was performed in each case. Phone call follow-up was performed by one author (EET) in all 31 cases and 2 cases out of the 28 that were contactable showed post-surgical recurrence of penile fibropapillomatosis (i.e., 7.1% recurrence rate).

CONCLUSION

This case series summarises the history and presenting findings of 31 bovine penile fibropapilloma cases and describes a regional anaesthetic and standing surgical approach for successful case management.

Castration alters the ileum microbiota of Holstein bulls and promotes beef flavor compounds

BACKGROUND

In the beef industry, bull calves are usually castrated to improve flavor and meat quality; however, this can reduce their growth and slaughter performance. The gut microbiota is known to exert a significant influence on growth and slaughter performance. However, there is a paucity of research investigating the impact of castration on gut microbiota composition and its subsequent effects on slaughter performance and meat flavor.

RESULT

The objective of this study was to examine the processes via which castration hinders slaughter productivity and enhances meat quality. Bull and castrated calves were maintained under the same management conditions, and at slaughter, meat quality was assessed, and ileum and epithelial tissue samples were obtained. The research employed metagenomic sequencing and non-targeted metabolomics techniques to investigate the makeup of the microbiota and identify differential metabolites. The findings of this study revealed the Carcass weight and eye muscle area /carcass weight in the bull group were significantly higher than those in the steer group. There were no significant differences in the length, width, and crypt depth of the ileum villi between the two groups. A total of 53 flavor compounds were identified in the two groups of beef, of which 16 were significantly higher in the steer group than in the bull group, and 5 were significantly higher in the bull group than in the steer group. In addition, bacteria, Eukaryota, and virus species were significantly separated between the two groups. The lipid metabolism pathways of α-linolenic acid, linoleic acid, and unsaturated fatty acids were significantly enriched in the Steers group. Compared with the steer group, the organic system pathway is significantly enriched in the bull group. The study also found that five metabolites (LPC (0:0/20:3), LPC (20:3/0:0), LPE (0:0/22:5), LPE (22:5/0:0), D-Mannosamine), and three species (s_Cloning_vector_Hsp70_LexA-HP1, s_Bacteroides_Coprophilus_CAG: 333, and s_Clostridium_nexile-CAG: 348) interfere with each other and collectively have a positive impact on the flavor compounds of beef.

CONCLUSIONS

These findings provide a basic understanding that under the same management conditions, castration does indeed reduce the slaughter performance of bulls and improve the flavor of beef. Microorganisms and metabolites contribute to these changes through interactions.

Cretan HLA genetics supports its early Minoan culture as a link between North Africa and Europe

HLA studies in Crete show that this population is related to North Africans and also Iberians. This may be a reflection of a common prehistoric first Europeans relationships with North Africans and drying Saharan emigration after 10,000 years BC; it may be specifically represented by a primitive and early cult to the bull in both Cretan (Minoan) and Iberian populations. In the present study, unrelated Cretans representing different Island parts have been studied for class II HLA-DRB1 and -DQB1 alleles. The most frequent ones were HLA-DRB1*11:01 and HLA-DRB1*07:01 and HLA-DQB1*03:01 and DQB1*05:01. Also, the Cretan HLA class II haplotype HLA-DBR1*11:01-DQB1*03:01 had the highest frequency and is also common to other Mediterraneans, including Iberians. In addition, DRB1*07:01-DQB1*02:01 and HLA-DRB1*04:02-DQB1*03:02 Cretan haplotypes are shared with North Africans (the latter with Algerians, Tunisians and Moroccans). In summary, Crete was one of the first European classic cultures (Minoan) which was probably an early link, like Iberia, between North Africa /Sahara and Europe,also supported by genetic results.

Sperm exposure to accessory gland secretions alters the transcriptomic response of the endometrium in cattle

In cattle, mating to intact, but not vasectomised, bulls has been shown to modify the endometrial transcriptome, suggesting an important role of sperm in the modulation of the uterine environment in this species. However, it is not clear whether these changes are driven by intrinsic sperm factors, or by factors of accessory gland (AG) origin that bind to sperm at ejaculation. Therefore, the aim of the present study was to determine whether ejaculated sperm, which are suspended in the secretions of the AGs, elicit a different endometrial transcriptomic response than epididymal sperm, which have never been exposed to AG factors. To this end, bovine endometrial explants collected from heifers in oestrus were (co-)incubated for 6 h alone (control), or with epididymal sperm or ejaculated sperm, following which transcriptomic changes in the endometrium were evaluated. Epididymal sperm elicited a more dramatic endometrial response than ejaculated sperm, in terms of the number of differentially expressed genes (DEGs). Indeed, RNA-sequencing data analysis revealed 1912 DEGs in endometrial explants exposed to epididymal sperm compared with control explants, whereas 115 DEGs were detected between endometrial explants exposed to ejaculated sperm in comparison to control explants. The top pathways associated with genes upregulated by epididymal sperm included T cell regulation and TNF, NF-KB and IL17 signalling. Interestingly, ejaculated sperm induced downregulation of genes associated with T cell immunity and Th17 differentiation, and upregulation of genes involved in NF-KB signalling, in comparison to epididymal sperm. These data indicate that factors of AG origin modulate the interaction between sperm and the endometrium in cattle.

The Bull Breeding Soundness Examination and Its Application in the Production Setting

breeding soundness for several reasons and at several times during their life span. These include before sale for the reason of affirming their sale ability or before a breeding season to determine their readiness for breeding. Bulls may also be evaluated for diagnostic purposes. The breeding soundness examination (BSE) is universally promoted as an important management tool, but there continues to be a level of inconsistency in its performance. A complete bull BSE consists of a thorough physical examination including internal and external reproductive tract, measurement of the circumference of the scrotum and evaluation of individual sperm motility and morphology.

Nutrition and Sexual Development in Bulls

This manuscript provides an overview of the effects of nutrition during different stages of bull sexual development. Nutrition during the prepubertal period can modulate the hypothalamic GnRH pulse generator. Increased nutrition results in greater LH secretion, earlier puberty, and greater testicular mass in yearling bulls, whereas low nutrition has opposite effects. Targeting average daily gain from birth to 24 weeks of age to > 1.2 kg/d and limiting gain after 24 weeks of age to < 1.6 kg/d is recommended to optimize bull sexual development.

Sperm-borne tsRNAs and miRNAs analysis in relation to dairy cattle fertility

Sperm small non-coding RNAs (sncRNAs), such as microRNAs (miRNAs) and tRNA-derived small RNAs (tsRNAs), have been found to have implications for male fertility and play a role in the intergenerational transmission of specific phenotypes by influencing the early embryo's physiological processes in various animal species. This study postulates that there exists a correlation between sperm small non-coding RNAs (sncRNAs) and bull fertility, which in turn can influence the fertility of offspring through the modulation of early embryo development. To investigate this hypothesis, we generated comparative libraries of sperm sncRNAs from sires exhibiting high (n = 3) versus low bull fertility (n = 3), as well as high (n = 3) versus low daughter fertility (n = 3), as determined by the industry-standard Bull fertility index and Daughter fertility index. In total, 12 tsRNAs carried by sperm (11 down-regulated and 1 up-regulated) were found to be associated with bull fertility, while 19 tsRNAs (11 down-regulated and 8 up-regulated) were found to be associated with daughter fertility (q < 0.05, Log2foldchange>±1.5, base mean > 50). Notably, tRX-Glu-NNN-3811 exhibited potential as a biomarker for predicting fertility in both male and female dairy cattle. Moreover, a total of six miRNAs sperm-borne (two up-regulated and four down-regulated) and 35 miRNAs (27 up-regulated and eight down-regulated) exhibited a significant correlation with both bull fertility and daughter fertility individually (p < 0.05, base mean > 50, log2foldchange>±1.5), two microRNAs, namely miR-2385-5p (down-regulated) and miR-98 (up-regulated), exhibit a significant association (p < 0.05, base mean > 50, log2foldchange>±1.5) with the fertility of both bulls and daughter. The targets of these two microRNAs were subsequently identified and integrated with the transcriptomic database of the embryonic cells at the two-cell stage, which is known to be indicative of embryonic competence. The KEGG analysis revealed a potential correlation between these targets and choline metabolism, a crucial factor in embryonic epigenetic programming. In summary, the findings of this study indicate that sperm-borne small non-coding RNAs (sncRNAs) hold promise as biomarkers for predicting and enhancing fertility in dairy cattle. Furthermore, it is plausible that these sncRNAs may exert their effects on daughter fertility by targeting genes in the early embryo.

New insights from poly-lactic acid and ionomer films coupled with recombinant antibodies for processing sexed-sorting bovine sperm

In this study, the efficacy of ionomers and poly-lactic acid (PLA) as an alternative solid material combined with scFv antibodies specific to bovine Y-sperm (Y-scFv) was studied to create a novel method of sexing technology. The coupling efficiency of Y-scFv to the surface of PLA, Na+ and Zn2+ ionomer film was between 2 and 8 mg/mL. Fourier transform infrared spectra confirm that Y-scFv was bound with a carboxylic acid group in each film. Therefore, Na+, Zn2+ ionomers and PLA films conjugated with 4 and 8 mg/mL Y-scFv showed the highest concentration of Y-sperm in the eluted fraction. Considering that the elute fraction was enriched Y-sperm fraction, it contained 67.70-77.94 % of the Y-sperm ratio related to the produced supernatant fraction, which contained up to 69.31-76.01 % enriched X-sperm. In addition, the sperm quality after the sexing process was analyzed by CASA and imaging flow cytometry, which showed that each polymer did not have a negative effect on sperm motility and acrosome integrity for X-sperm. The capacity of ionomer and PLA combined with Y-scFv are used for bovine sperm sexing.

DNA methylation profiles in bovine sperm are associated with daughter fertility

The current decline in dairy cattle fertility has resulted in significant financial losses for dairy farmers. In the past, most efforts to improve dairy cattle fertility have been focused on either management or genetics, while epigenetics have received less attention. In this study, 12 bulls were selected from a provided 100 bull list and studied (High daughter fertility = 6, Low daughter fertility = 6) for Enzymatic methylation sequencing in the Illumina HiSeq platform according to the Canadian daughter fertility index (DFI), sires with high and low daughter fertility have average DFI of 92 and 112.6, respectively. And the bull list provided shows a mean DFI of 103.4. 252 CpGs with methylation differences greater than 20% (q < 0.01) were identified, as well as the top 10 promising DMRs with a 15% methylation difference (q < 1.1e-26). Interestingly, the DMCs and DMRs were found to be distributed more on the X chromosome than on the autosome, and they were covered by gene clusters linked to germ cell formation and development. In conclusion, these findings could enhance our ability to make informed decisions when deciding on superior bulls and advance our understanding of paternal epigenetic inheritance.

Relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls: a cross sectional study

The aim of this study was to investigate the relationship between age, scrotal circumference, postweaning weight and semen quality in Nellore and Caracu bulls selected for postweaning weight. Data from the andrological evaluation of 836 bulls born between 2000 and 2019, including 583 Nellore animals (Bos indicus) and 253 Caracu animals (Bos taurus), were used. The bulls were divided into categories of age at the time of assessment: category 1 consisted of animals aged 20 to 23 months (22 ± 0.76 months, 518 ± 94.17 kg), category 2 consisted of animals aged 24 to 35 months (30 ± 4.42 months, 679 ± 137.19 kg), and category 3 consisted of animals ≥ 36 months (60 ± 14.12 months, 907 ± 161.73 kg). The statistical model included the effects of breed, age category, date of semen collection, and breed x age category interaction. Heritability estimates for scrotal circumference at 13 months of age (SC1year) and semen quality traits were obtained for the sample of Nellore animals. Most semen quality traits improved with increasing age in both Nellore and Caracu animals. High heritability was observed for SC1year (0.45), while sperm motility, vigor, turbulence, and major, minor and total sperm defects exhibited low heritability (0.11, 0.019, 0.047, 0.017, 0.017 and 0.019, respectively). Spearman correlations of breeding values for postweaning weight (W378) and SC1year with the semen quality traits were low. Nellore and Caracu bulls have similar semen quality that improves with increasing age. In the Nellore breed, the heritability of SC is high, while semen quality traits exhibit low heritability. Selection for higher postweaning weight does not phenotypically affect the semen quality of bulls at breeding age.

Pre-freezing selection of Holstein bull semen with the BoviPure colloid as double- or single-layer centrifugation improves the post-thawing quality

Artificial insemination (AI) is critical for breeding in the dairy industry. High-merit bulls can present low freezability, hampering genetic dissemination. Thawed semen can be improved using density gradient centrifugation (DGC) with colloids, but little information deals with the pre-freezing application. Thus, the BoviPure colloid (optimized for bull spermatozoa) was tested for pre-freezing application as the usual double-layer (DLC) versus single-layer (SLC, quick and economical). Semen from twelve Holstein-Friesian bulls was extended with OPTIXcell extender, frozen (Control), or processed by SLC or DLC and frozen. Sperm were assessed pre-freezing for motility and viability and post-thawing (directly and after 4 h 38 °C) for apoptosis, capacitation status, acrosomal damage, mitochondrial activity, cytoplasmic and mitochondrial reactive oxygen species (ROS), and chromatin status (SCSA for DNA fragmentation and chromatin compaction and monobromobimane, mBBr, for disulfide bridges evaluation). The DGC improved parameters post-thawing (e.g., 57.5%±10.1 motility vs. control 53.3% ± 11.2) at the cost of sperm loss (sperm recovery of DGC 14.4% ± 2.5 and SLC 17.4% ± 2.5). DNA fragmentation (%DFI) decreased (0.21% ± 0.53 vs. control 1.30% ± 0.10), and SLC reduced chromatin compaction. A clustering procedure separated lesser (LF) and greater freezability (GF) bulls. LF samples were especially benefited by DGC, with SLC providing better post-thawing results for this group. In conclusion, pre-freezing DGC improved sperm parameters post-thawing, potentially improving the cryopreservation of low-freezability semen from high-merit bulls. SLC, quicker and economical, would be preferable since it showed similar or higher performance than DLC.

Evaluation of pregnancy per artificial insemination of dairy animals detected in estrus during the synchronization protocol and assigned to conventional or sexed semen

Three experiments were designed to evaluate the effects of conventional and sexed-semen on reproductive performance of dairy females detected in estrus. In Exp. 1, 978 lactating Holstein cows and 116 Holstein heifers were used. Cows or heifers were randomly assigned to receive conventional (CONV) or sexed (SEXD) semen on day 0 of a TAI protocol. The TAI was performed using commercial CONV or SEXD frozen-thawed semen from the same 6 Holstein bulls, and SEXD semen was sexed through fluorescence cytometry. In Exp. 2, 390 lactating Holstein × Gir dairy cows and 344 Holstein × Gir heifers were used. Cows and heifers were randomly assigned to receive CONV or SEXD semen on day 0 with frozen-thawed semen from 5 Holstein × Gir bulls. The SEXD was sorted through the Sexcel™ methodology. In Exp. 3, 789 primiparous lactating Holstein cows were enrolled. Cows were randomly assigned to receive CONV or SEXD semen from 5 Holstein bulls, and the SEXD semen was sexed using the same semen allocation methodology described in Exp. 2. All data were analyzed using SAS. Regardless of the experiment, no treatment × bull interaction was observed for any of the variables analyzed herein (P ≥ 0.20). In Exp. 1, multiparous cows assigned to CONV had a greater P/AI vs. cohorts assigned to SEXD (P < 0.01) and a similar response tended to be observed for secundiparous cows (P = 0.10). No treatment effects were further observed when the effects of semen on day 60 P/AI were stratified by heat stress, milk yield, and CL at the beginning of the protocol. In Exp. 2, no P/AI differences between treatment were detected either on days 32 (P = 0.32) or 60 of pregnancy (P = 0.20). In Exp. 3, cows assigned to SEXD had reduced P/AI on day 32 (P = 0.03) and tended to have a reduced P/AI on day 60 of pregnancy (P = 0.06). No further treatment effects or interactions were observed herein (P ≥ 0.13). Overall P/AI of SEXD semen was 78% of the CONV (P < 0.01), but the variation of these results requires some attention. Moreover, an additional analysis was performed considering the median value of P/AI in bulls assigned to CONV and SEXD, and bulls that had a greater P/AI in CONV also had a greater P/AI in SEXD (P = 0.03). In summary, although not directly comparable, the sexing technologies herein provided similar results in heifers, but not in other categories (primiparous, secundiparous, and multiparous cows). Additionally, the P/AI of a sexed semen is associated to its performance on the conventional semen counterpart. Moreover, in the present experiment, no other parameters were shown to impact fertility of dairy females assigned to conventional or sexed-semen.

Seroprevalence and detection of bovine leukosis virus in semen from breeding bulls in Costa Rica

Bovine leukemia virus (BLV) causes enzootic bovine leukosis, a persistent infection and the most important neoplastic disease in cattle. It is spread primarily by transferring infected lymphocytes through blood from carriers to healthy animals. The present study is aimed at determining the seropositivity of BLV in breeding bulls from Costa Rica and at detecting for the first time in the country BLV DNA in bull semen. Between May 2011 and August 2018, 379 blood and 133 semen samples were collected from bulls distributed in 118 farms. The serum was analyzed by an enzymatic immunoassay and the semen by polymerase chain reaction and sequencing. BLV seropositivity was 43.5% (165/379), while 64.4% (76/118) of the farms had positive reactors. Holstein (75.7%) and Jersey (73.0%) breeds showed the highest seropositivity. In addition, Bos taurus bulls (68.1%), older than seven years (50.0%), and those belonging to dairy farms (75.5%) had higher seropositivity compared to Bos indicus (17.7%), younger than seven years (42.2%), and those from beef farms (15.5%), respectively. Moreover, Bos taurus bulls had a higher risk of being seropositive than Bos indicus (OR = 3.4; 95% CI: 1.7-6.8). BLV DNA was found in one semen sample (2.5%; 1/40) from a seropositive bull. The importance of serum and molecular BLV screening in semen samples and the potential role of some risk factors associated with the disease, such as the bull's age, genotype, and type of livestock productive system, is argued in the present report.

CpG DNA methylation changes during epididymal sperm maturation in bulls

BACKGROUND

During epididymal transit spermatozoa acquire specific morphological features which enhance their ability to swim in a progressive manner and interact with the oocytes. At the same time, sperm cells undergo specific molecular rearrangements essential for the fertilizing sperm to drive a correct embryo development. To assess epigenetic sperm changes during epididymal maturation, the caput, corpus and cauda epididymis sperm tracts were isolated from eight bulls and characterized for different sperm quality parameters and for CpG DNA methylation using Reduced Representation Bisulfite Sequencing (RRBS) able to identify differentially methylated regions (DMRs) in higher CpG density regions.

RESULTS

Caput sperm showed significant variation in motility and sperm kinetics variables, whereas spermatozoa collected from the corpus presented morphology variation and significant alterations in variables related to acrosome integrity. A total of 57,583 methylated regions were identified across the eight bulls, showing a significantly diverse distribution for sperm collected in the three epididymal regions. Differential methylation was observed between caput vs corpus (n = 11,434), corpus vs cauda (n = 12,372) and caput vs cauda (n = 2790). During epididymal transit a high proportion of the epigenome was remodeled, showing several regions in which methylation decreases from caput to corpus and increases from corpus to cauda.

CONCLUSIONS

Specific CpG DNA methylation changes in sperm isolated from the caput, corpus, and cauda epididymis tracts are likely to refine the sperm epigenome during sperm maturation, potentially impacting sperm fertilization ability and spatial organization of the genome during early embryo development.

Candidate genes and proteins regulating bull semen quality: a review

Poor semen profile reflected by suboptimum fertility statistics is a concern in bulls reared for breeding purpose. A critical review of research on candidate genes and proteins associated with semen quality traits will be useful to understand the progress of molecular marker development for bull semen quality traits. Here, we have tabulated and classified candidate genes and proteins associated with bull semen quality based on a literature survey. A total of 175 candidate genes are associated with semen quality traits in various breeds of cattle. Several studies using candidate gene approach have identified 26 genes carrying a total of 44 single nucleotide polymorphisms. Furthermore, nine genome-wide association studies (GWASes) have identified 150 candidate genes using bovine single nucleotide polymorphisms (SNP) chips. Three genes, namely membrane-associated ring-CH-type finger 1 (MARCH1), platelet-derived growth factor receptor beta, and phosphodiesterase type 1, were identified commonly in two GWASes, which, especially MARCH1, are required to explore their regulatory roles in bull semen quality in in-depth studies. With the advancement of high-throughput-omic technologies, more candidate genes associated with bull semen quality may be identified in the future. Therefore, the functional significance of candidate genes and proteins need to be delved further into future investigations to augment bull semen quality.

New insights into posttranslational modifications of proteins during bull sperm capacitation

BACKGROUND

Due to the unique nature of spermatozoa, which are transcriptionally and translationally silent, the regulation of capacitation is based on the formation of posttranslational modifications of proteins (PTMs). However, the interactions between different types of PTMs during the capacitation remain unclear. Therefore, we aimed to unravel the PTM-based regulation of sperm capacitation by considering the relationship between tyrosine phosphorylation and reversible oxidative PTMs (oxPTMs), i.e., S-nitrosylation and S-glutathionylation. Since reversible oxPTMs may be closely related to peroxyredoxin (PRDX) activity, the second aim was to verify the role of PRDXs in the PTM-based regulation of capacitation.

METHODS

Cryopreserved bull sperm were capacitated in vitro with or without PRDX inhibitor. Qualitative parameters of sperm and symptoms characteristic of capacitation were analyzed. Posttranslational protein modifications (S-nitrosylation, S-glutathionylation, tyrosine phosphorylation) were investigated at the cellular level (flow cytometry, fluorescence microscopy) and at the proteomic level (fluorescent gel-based proteomic approach).

RESULTS

Zona-pellucida binding proteins (ACRBP, SPAM1, ZAN, ZPBP1 and IZUMO4) were particularly rich in reversible oxPTMs. Moreover, numerous flagellar proteins were associated with all analyzed types of PTMs, which indicates that the direction of posttranslational modifications was integrated. Inhibition of PRDX activity during capacitation caused an increase in S-nitrosylation and S-glutathionylation and a decrease in tyrosine phosphorylation. Inhibition of PRDXs caused GAPDHS to undergo S-glutathionylation and the GSTO2 and SOD2 enzymes to undergo denitrosylation. Moreover, PRDX inhibition caused the AKAP proteins to be dephosphorylated.

CONCLUSIONS

Our research provides evidence that crosstalk occurs between tyrosine phosphorylation and reversible oxPTMs during bull sperm capacitation. This study demonstrates that capacitation triggers S-nitrosylation and S-glutathionylation (and reverse reactions) of zona-pellucida binding proteins, which may be a new important mechanism that determines the interaction between sperms and oocytes. Moreover, TCA-related and flagellar proteins, which are particularly rich in PTMs, may play a key role in sperm capacitation. We propose that the deglutathionylation of ODFs and IZUMO4 proteins is a new hallmark of bull sperm capacitation. The obtained results indicate a relationship between PRDX activity and protein phosphorylation, S-glutathionylation and S-nitrosylation. The activity of PRDXs may be crucial for maintaining redox balance and for providing proper PKA-mediated protein phosphorylation during capacitation. Video Abstract.

A potent allele marker related to low bull conception rate in Japanese Black bulls

Over the years, there has been considerable variation in the bull conception rate (BCR) of Japanese Black cattle; moreover, several Japanese Black bulls with a low BCR of ≤10% have been identified. However, the alleles responsible for the low BCR are not determined yet. Therefore, in this study, we aimed to identify single-nucleotide polymorphisms (SNPs) for predicting low BCR. To this end, the genome of Japanese Black bulls was comprehensively examined by a genome-wide association study with whole-exome sequencing (WES), and the effect of the identified marker regions on BCR was determined. The WES analysis of six sub-fertile bulls with a BCR of ≤10% and 73 normal bulls with a BCR of ≥40% identified a homozygous genotype for low BCR in Bos taurus autosome 5 in the region between 116.2 and 117.9 Mb. The g.116408653G > A SNP in this region had the most significant effect on the BCR (P-value = 1.0 × 10^-23), and the GG (55.4 ± 11.2%) and AG (54.4 ± 9.4%) genotypes in the SNP had a higher phenotype than the AA (9.5 ± 6.1%) genotype for the BCR. The mixed model analysis revealed that g.116408653G > A was related to approximately 43% of the total genetic variance. In conclusion, the AA genotype of g.116408653G > A is a useful index for identifying sub-fertile Japanese Black bulls. Some positive and negative effects of SNP on the BCR were presumed to identify the causative mutations, which can help evaluate bull fertility.

Extension of the equilibration period up to 24 h maintains the post-thawing quality of Holstein bull semen frozen with OPTIXcell®

Semen cryopreservation in bovine livestock is well established, but logistics often require deviations from standard protocols. Extending the equilibration time to the following day is convenient in many situations. To improve our knowledge of the effects of this modification, we studied the post-thawing and post-incubation (4 h, 38 °C) sperm quality after freezing with 4 or 24-h extension in the OPTIXcell extender by using an ample panel of analyses: CASA for motility; flow cytometry for viability, physiology, oxidative stress, and chromatin parameters (DNA fragmentation, chromatin compaction, and thiol groups status); and spectrometry for malondialdehyde production. Semen was obtained from 12 Holstein bulls. The 24-h equilibration time showed few significant effects, with only a tiny decrease in progressive motility and a positive impact on chromatin structure. The incubation removed some of these effects, with the pattern for chromatin compaction remaining the same. No detrimental oxidative stress or increase in apoptotic or capacitation markers was detected. Additionally, the individual bull interacted with the effects of the incubation and the equilibration, especially regarding the chromatin status. Whereas this interaction did not critically affect sperm quality, it could be relevant in practice. Bull fertility as non-return rates (NRR56) was associated with some sperm parameters (especially with an improved chromatin structure) but not in the 4-h post-thawing analysis. Our study supports that extending the equilibration time by at least 24-h is feasible for bull semen freezing with the OPTIXcell extender.

Chronic ergot exposure in adult bulls suppresses prolactin but minimally impacts results of typical breeding soundness exams

Canadian standards allow ≤3000 μg ergot alkaloids/kg cattle feed. A concentration-response relationship was hypothesized between ergot in feed and reductions in plasma prolactin, sperm motility, sperm function, and increase in sperm abnormalities. The study consisted of pre-treatment (12 weeks), treatment (9 weeks), and post-treatment periods (10 weeks). Adult bulls were fed 1113 (n = 8; low ergot group) or 2227 (n = 6; high) μg/kg of dry matter intake. Endpoints were measured every two weeks. Ejaculates were analyzed for sperm concentration, total and progressive motility, plasma membrane and acrosome integrity, mitochondrial membrane potential and sperm abnormalities. Data were analyzed by repeated measures MIXED PROC in SAS. Average outside ambient temperature during the pre-treatment, treatment, and post-treatment periods was -13 (-31 to 1), 0.5 (-18 to 19), and 21 (13-28) °C. Plasma prolactin decreased markedly during treatment (-52.4%; Experimental period p < 0.01). Rectal temperature increased during the treatment and post-treatment periods (EP p < 0.01) but was within the normal physiological range. Bull weight increased during the study (EP p < 0.01). Scrotal circumference in low ergot group increased during treatment (+0.8 cm; Tx∗EP p = 0.05). Progressive motility in high ergot group decreased during treatment (-7%; Tx∗EP p = 0.05), however, semen volume and sperm concentrations were unaffected (p ≥ 0.11). Live sperm with high and medium MMP decreased during treatment (-1.4 and -3.7%; EP p < 0.01). Results suggest that feeding ≤2227 μg ergot alkaloids/kg has only minor effects on adult bull semen quality.

Molecular detection of Tritrichomonas foetus in bovine samples: a novel real-time polymerase chain reaction (PCR) assay targeting EF1-alpha-Tf1 and a comparative study of published PCR techniques

The parasite T. foetus causes trichomonosis in cattle but is generally asymptomatic in males. Thus, many bulls carrying the disease go unnoticed, making the detection of T. foetus in bulls an important aspect for its control. Due to drawbacks posed by its cultivation, PCR is a preferred option for diagnostic laboratories. Most published PCR protocols target the genomic region compring the 18S, 5.8S, and 28S rRNA genes and internal transcribed spacers 1 and 2 (rRNA-ITS region), homologous to that of other Tritrichomonas species. There is minimal information on alternative genetic targets and no comparative studies have been published. We compared a protocol based on the microsatellite TfRE (called H94) and five protocols based on the rRNA-ITS region (called M06, M15, G02, G05, and N02). We also designed and evaluated a novel PCR-based assay on the EF1-alpha-Tf1 gene (called V21). The analytical sensitivity and specificity assays for the PCR protocols were performed according to the World Organisation for Animal Health (OIE) directives and the comparative study was performed with a widely used PCR (M06) on clinical samples from 466 breeding bulls. V21 showed a high degree of agreement with our reference M06 (kappa = 0.967), as well as M15 (kappa = 0.958), G05 (kappa = 0.948), and H94 (kappa = 0.986). Protocols H94 and V21 appear to be good approaches for confirming clinical cases in preputial bull samples when genomic regions alternative to rRNA-ITS are required. By contrast, N02 gave false negatives and G02 false positives.

A rare urachal abscess in a young bull with conservative management

Background

The urachus is an embryonic remnant occurring as a result of the involution of the allantoic duct and the ventral cloaca. This canal becomes progressively obliterated after birth. It uncommonly persists to different degrees after birth.

Case Description

A young bull was presented with distended abdomen and clinical signs of chocking, with low-grade fever, loss of appetite, frothy mouth arched back. On the first inspection, the animal was suspected to have simple indigestion. The treatment was attempted in this stage by introducing a stomach tube but only little relief was achieved. Therefore, 5 days later, an exploratory laparotomy was done and a big balloon-like cyst structure extended ventro-latrally in the abdominal cavity was noticed. That structure was located on the floor of the abdominal cavity extending from the pelvic rim caudally to the umbilical region cranially. The structure was then incised and evacuated and a rubber tube was fixed for constant drainage for up to one month later. The bull was followed-up and made a good recovery after a month post-surgery.

Conclusion

We found that urachal abscess could be treated simply via surgical evacuation of the abscess and proper drainage for some time with a very promising outcome. Additionally, this affection can be diagnosed based on history, clinical signs, and exploratory surgery, when relatively modern diagnostic techniques are not available.

Detection of DNA Damage in Frozen Bovine Semen Using Eosin Staining

&lt;b&gt;Background and Objective:&lt;/b&gt; Early detection of DNA defects in spermatozoa is vital because genetic abnormalities are associated with infertility and miscarriage. Eosin is an acidic stain with negatively charged chromatolytic components also found in the cytoplasm of spermatozoa. This study aimed to observe the effectiveness of eosin staining in detecting spermatozoa DNA deterioration. &lt;b&gt;Materials and Methods:&lt;/b&gt; A total of four-hundred frozen beef straws from Simmental, Limousin and Brahman cattle and Ongole crossbreeds, were obtained from the Singosari National Artificial Insemination Center, Malang, Indonesia.Hydrogen peroxide was used to degrade frozen sperm. In addition, the sperm was subjected to three treatments: Agarose trapping, membrane lysis and eosin staining. &lt;b&gt;Results:&lt;/b&gt; Damaged bull spermatozoa stained with eosin were bright red in color around the head and mid piece, whereas the head of undamaged spermatozoa were darker red. The average value of damaged DNA was 89.08±3.27% as assessed with eosin staining. &lt;b&gt;Conclusion:&lt;/b&gt; Eosin staining effectively detects DNA damage in bull spermatozoa, but extended effectiveness tests are considered necessary.

Pharmacokinetics of tulathromycin on plasma and semen of beef bulls

The objective of this investigation was to evaluate the pharmacokinetic parameters of tulathromycin in plasma and semen of beef bulls after administering a single sc dose at two different sites in the neck. Four Simmental bulls with excellent temperament received a comprehensive physical exam that included breeding soundness examination. In addition, blood was collected and analyzed for CBC and chemical panel in order to rule out any subclinical liver or kidney disease. All bulls were diagnosed as healthy and satisfactory potential breeders. The mean plasma levels of tulathromycin for the two neck sites of sc administration were not different between posterior aspect of the ear where it attaches to the head (RP; regio parotidea; 77.9 ± 43.3 ng/mL; X ± SD) and to the middle of the neck (RC; regio collis lateralis; 73.7 ± 39.7 ng/mL; P = 0.84). The mean seminal plasma levels of tulathromycin after administration in the RP was 608 ± 374 ng/mL and for RC was 867 ± 599 ng/mL without differences between both sites (P = 0.29). The mean level of tulathromycin in plasma was 75.8 ± 40.2 ng/mL, which was lower than mean seminal plasma levels of 781 ± 482 ng/mL (P = 0.001). The plasma peak tulathromycin concentration (C_max) was 160 ± 27 ng/mL at 21 ± 6 h (T_max) post-administration. The seminal plasma C_max was 1539 ± 44.4 ng/mL at 33.00 ± 18.00 h (T_max) post-administration. The C_max between plasma and seminal plasma were different (P = 0.008) without any differences in T_max between plasma and seminal plasma (P = 0.35). The terminal half-life for plasma tulathromycin (81.4 ± 27.6 h) showed a tendency to be shorter than in seminal plasma (114.7 ± 21.7; P = 0.10). The plasma area under the curve concentration time from the first to the last sample (AUC_0-last) was 15,440 ± 1717 ng/mL/h, which was significatively smaller compared with 171,071 ± 58,556 ng/mL/h for seminal plasma AUC_0-last (P = 0.01). The plasma means residence time from the first to the last sample (MRT_0-last) was 89.3 ± 5.1 h and it was shorter than for seminal plasma of 96.6 ± 5.0 h (P = 0.05). From the present investigation, it was concluded that tulathromycin is a suitable antibiotic based in its pharmacokinetic properties that could be used for treatment of bull genital infections when its application is indicated.

Effects of reduced glutathione supplementation in semen freezing extender on frozen-thawed bull semen and in vitro fertilization

During cryopreservation, spermatozoa may suffer cold and cryo-induced injuries -associated with alterations in cell defense systems- that are detrimental to their function and subsequent fertility. This study aimed to determine the efficacy of supplementing the semen freezing extender with the antioxidant reduced glutathione (GSH) in cattle. Semen was collected from four bulls and diluted in a freezing extender supplemented with or without GSH (0, 1, 5, and 10 mM) before the cooling step of the cryopreservation process. After thawing, the quality of the frozen-thawed semen was investigated for motility, viability, acrosomal and DNA integrity, and subsequent embryo development after in vitro fertilization of bovine oocytes. Additionally, semen from one of the bulls was used to analyze semen antioxidative potential, sperm penetration into oocytes, male pronucleus formation rate, and embryo DNA integrity. The sperm quality varied among bulls after GSH supplementation. One bull had decreased sperm total motility, and two bulls had decreased sperm DNA integrity. GSH supplementation had positive effects on embryo development for three bulls. Two of them showed both improved cleavage and blastocyst formation rates, while the other one only showed an improved cleavage rate. We observed positive effects on early male pronucleus formation and no negative effects on DNA integrity and cell number in blastocyst stage embryos. Although the effect varies depending on individual bulls and GSH concentration, GSH supplementation in semen may improve in vitro embryo production from frozen semen.

Environmental temperature and relative humidity differently affect the sperm characteristics in Brown Swiss and Belgian Blue bulls

In a temperature-increasing scenario, due to global warming, the individual thermic resilience of the male assumes a crucial role in the reproductive efficiency of a male since the thermic stress, such as the inability of the male to reduce body or regional temperature on a physiological level, impairs testicular function. In this study, the effect of the environmental conditions on the fresh semen quality, in terms of volume, concentration, total sperm in the ejaculate, total motility, normal morphology, membrane integrity, and discarding rate, were compared longitudinally in Belgian Blue (BB) and Brown Swiss (BS) bulls. The environmental conditions, summarized in the mean temperature-humidity index (THI), were calculated on the day of collection, as well as 7 days (epididymal maturation), 35 days (late spermatogenesis), and 70 days (early spermatogenesis) before the collection, to reflect spermatogenesis time. Our findings showed that limited seasonal effects were present in the semen quality of BS bulls. On the other hand, in BB bulls lower semen quality was found between July and November, with a different timing depending on the seminal parameter. This effect of the season on BB semen parameters appears to be related to the THI. The data presented in this study shows that the temperature and humidity, summarized in THI, could affect the semen quality of the bull on breed basis, given that volume, concentration, total sperm in the ejaculate, total motility, membrane integrity, and sperm normal morphology were significantly reduced by an increasing THI in the Belgian Blue bulls, but not in Brown Swiss bulls.

Sperm chromatin condensation as an in vivo fertility biomarker in bulls: a flow cytometry approach

Background

Genetic selection in cattle has been directed to increase milk production. This, coupled to the fact that the vast majority of bovine artificial inseminations (AI) are performed using cryopreserved sperm, have led to a reduction of fertility rates over the years. Thus, seeking sensitive and specific sperm biomarkers able to predict fertility rates is of vital importance to improve cattle reproductive efficiency. In humans, sperm chromatin condensation evaluated through chromomycin A3 (CMA3) has recently been purported to be a powerful biomarker for sperm functional status and male infertility. The objectives of the present study were: a) to set up a flow cytometry method for simultaneously evaluating chromatin condensation and sperm viability, and b) to test whether this parameter could be used as a predictor of in vivo fertility in bulls. The study included pools of three independent cryopreserved ejaculates per bull from 25 Holstein males. Reproductive outcomes of each sire were determined by non-return rates, which were used to classify bulls into two groups (highly fertile and subfertile).

Results

Chromatin condensation status of bovine sperm was evaluated through the combination of CMA3 and Yo-Pro-1 staining and flow cytometry. Sperm quality parameters (morphology, viability, total and progressive motility) were also assessed. Pearson correlation coefficients and ROC curves were calculated to assess their capacity to predict in vivo fertility. Sperm morphology, viability and total motility presented an area under the ROC curve (AUC) of 0.54, 0.64 and 0.68, respectively (P > 0.05), and thus were not able to discriminate between fertile and subfertile individuals. Alternatively, while the percentage of progressively motile sperm showed a significant predictive value, with an AUC of 0.73 (P = 0.05), CMA3/Yo-Pro-1 staining even depicted superior results for the prediction of in vivo fertility in bulls. Specifically, the percentage of viable sperm with poor chromatin condensation showed better accuracy and precision to predict in vivo fertility, with an AUC of 0.78 (P = 0.02).

Conclusions

Chromatin condensation evaluated through CMA3/Yo-Pro-1 and flow cytometry is defined here as a more powerful tool than conventional sperm parameters to predict bull in vivo fertility, with a potential ability to maximising the efficiency of dairy breeding industry.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00634-7.

Supraphysiological concentration of urea affects the functional competence of Holstein-Friesian (Bos taurus) sperm

To understand the effects of urea on sperm functional attributes, fresh bull semen (n = 12) was subjected to four different concentrations (mg/mL) of urea to mimic the physiological (0.04 and 0.13), supraphysiological (0.43) concentrations and control (0 mg/mL). Sperm membrane integrity, kinematics, chromatin integrity, and mitochondrial membrane potential were assessed at different time points (before incubation, 0, 1, 2, and 4 h) of incubation. The concentration of urea in serum and seminal plasma was estimated and correlated with the ejaculate rejection rate and sperm functional attributes. The relative expression of urea transporter gene transcripts (UT-A and UT-B) was assessed in sperm and testis (control) using real-time PCR. The supraphysiological concentration of urea affected sperm kinematics, viability, functional membrane integrity, and acrosome integrity within 1 h of incubation (p < 0.05). Sperm head area decreased (p < 0.05) at 0 h and subsequently increased at 1 h of incubation in all media except supraphysiological (0.43 mg/dL) concentration of urea. Seminal plasma urea concentration showed a significant negative correlation with sperm motility, membrane integrity, and mitochondrial membrane potential (p < 0.05), but had a positive correlation with the ejaculate rejection rate (r = 0.69). Relative expression of the urea transporter genes revealed that UT-A was expressed only in the testis. In contrast, UT-B was expressed in both the testis and sperm, suggesting UT-B's role in regulating urea transport in sperm. At a supraphysiological level, urea adversely affected sperm functional attributes, osmoadaptation and may affect fertility.

Effects of paternal diet and antioxidant addition to the semen extender on bovine semen characteristics and on the phenotype of the resulting embryo

The aim of this study was to examine the effects of long-term dietary supplementation of young Nellore bulls with rumen-protected polyunsaturated fatty acids (PUFAs) and of the inclusion of catalase in the semen extender on semen quality, in vitro sperm fertilizing ability, and intracytoplasmic lipid content in the resulting embryos. Twelve Nellore bulls were supplemented with rumen-protected PUFAs or with a basal diet from 14 to 24 months of age. The semen was collected at the end of supplementation. For cryopreservation, the ejaculate was divided into two equal volumes and catalase was added to the extender in one of the fractions. Thus, the experimental design consisted of a 2 × 2 factorial scheme with two diets (control and PUFA) and two extenders (Cat+ and Cat-). Total motility and the percentage of rapid cells in fresh semen were negatively affected by dietary supplementation with PUFAs (P < 0.05), but these effects did not persist after freezing. The frozen/thawed semen of animals fed PUFAs exhibited an increase in the percentages of damaged plasma and acrosomal membranes, as well as an increase in the proportion of lipids ions at m/z 578 and m/z 757 detected by MALDI-MS. Nevertheless, there was no effect of the treatments on in vitro embryo development. However, embryos derived from bulls supplemented with PUFAs exhibited higher lipid accumulation compared to control (P < 0.05). In conclusion, PUFA supplementation promoted worsening of semen quality without affecting the in vitro sperm fertilizing ability; however, the paternal diet affected the intracytoplasmic lipid content in the resulting embryos.

Effect of supplemental trace minerals on standard and novel measures of bull fertility

Two studies were conducted to evaluate the effects of trace mineral supplementation on traditional and novel measures of bull fertility. In Experiment 1, 37 mature bulls received one of three dietary supplements daily for 71 d: 1) Supplement without Cu, Zn, and Mn (CON); 2) Supplement with Cu, Zn, and Mn sulfate (SULF); and 3) Supplement with basic Cu chloride, and Zn and Mn hydroxychloride (CHLR). In Experiment 2, 128 Angus or Angus-Hereford bull calves were maintained on a growing diet for 75 d (year 1) or 119 d (year 2) in Calan gate equipped pens without mineral supplementation. Bulls (n = 32 head/treatment) received one of four trace mineral supplements daily for 84 d: 1) Zn with no Cu (ZN), 2) Cu with no Zn (CU), 3) Cu and Zn (ZNCU), or 4) no Cu or Zn (CON). Bull fertility measures included a breeding soundness evaluation (BSE) and novel fertility measures conducted using flow cytometry. In mature bulls, final liver Zn concentration was positively correlated (P = 0.02) with sperm concentration (r = 0.31) and tended (P = 0.06) to be negatively correlated with acrosome damage (r = -0.39). Peripubertal bulls receiving ZNCU had greater ADG than bulls in the CU group (P = 0.05). Each BSE and novel fertility component improved from Day 0-84 in peripubertal bulls and were not affected (P > 0.10) by mineral supplementation. Bulls that received no supplement (CON) had greater (P < 0.01) percentage of sperm with distal midpiece reflex (6.9 vs 4.0% for CON and TM supplement, respectively) and Dag or Dag-like defect (2.6 vs 1.4% for CON and TM supplement, respectively) in their ejaculates. Sperm viability after 30 min of incubation were not affected by trace mineral supplementation, but after 3 h incubation, sperm viability tended to differ (P = 0.06) between treatments and tended to be less for CON bulls (48.5%) compared to ZNCU bulls (55.1%). Among contrast comparisons, trace mineral supplemented bulls had greater (P < 0.05) percentage of viable sperm at 3 h post collection and reactive oxygen resistant sperm than CON bulls. Addition of Zn to trace mineral containing Cu (ZNCU) improved (P < 0.05) percentage of sperm in the ejaculate with high mitochondrial energy potential and viable sperm with intact acrosome membrane. In summary, it appears the homeostasis mechanisms for bull trace mineral maintenance are extremely efficient and mineral supplementation of mature and peripubertal bulls did not have major improvements in any laboratory or chute-side measures of bull fertility, however bulls exposed to breeding or in environments with diet antagonists might respond differently.

Sperm phenotypic characteristics and oviduct binding ability are altered in breeding bulls with high sperm DNA fragmentation index

In the present study, we standardized an in vitro oviduct explants model for cattle and assessed the oviduct explants binding ability and phenotypic characteristics of spermatozoa obtained from breeding bulls with high- and low-sperm DNA fragmentation index (DFI%). Cryopreserved spermatozoa from Holstein Friesian crossbred breeding bulls (n = 45) with known field fertility were assessed for DFI% and were classified into either high DFI% or low DFI% category. Flow cytometry was used to assess sperm membrane integrity, acrosome reaction status, mitochondrial membrane potential and intracellular calcium concentrations. It was found that spermatozoa from bulls with low DFI% had significantly higher (P < 0.05) membrane integrity, acrosome intactness, and mitochondrial membrane potential. To assess the sperm oviduct binding ability, oviduct explants were prepared by incubating the oviduct cells overnight in TCM-199 medium at 38.5 °C under 5% CO₂. Different sperm concentrations and times of incubation were evaluated and found that 2 million spermatozoa and 1-h incubation yielded high binding index (BI). The BI was also significantly (P < 0.01) higher (>2 times) in the bulls with low-DFI% as compared to high DFI% bulls. The correlation between binding index and DFI% was negative and significant (r = -0.528; P < 0.05). Further, the binding index was positively correlated with conception rate (r = 0.703), intact sperm membrane (r = 0.631) and mitochondrial membrane potential (r = 0.609). It is inferred that sperm phenotypic characteristics and oviduct binding ability are impaired in breeding bulls with high sperm DFI%, which might be associated with low conception rates in these bulls.

Ouabain-induced activation of phospholipase C zeta and its contributions to bovine sperm capacitation

The sperm-derived oocyte activating factor, phospholipase C zeta (PLC ζ), is the only PLC isoform reported in cattle. The objectives were to (1) localize PLC ζ in fresh and capacitated bovine sperm and (2) investigate the activation of PLC ζ during bull sperm capacitation and contributions of PLC activity to this process. We confirmed interaction of testis-specific isoform of Na/K-ATPase (ATP1A4) with PLC ζ (immunolocalization and immunoprecipitation) and tyrosine phosphorylation (immunoprecipitation) of PLC ζ (a post-translational protein modification commonly involved in activation of PLC in somatic cells) during capacitation. Furthermore, incubation of sperm under capacitating conditions upregulated PLC-mediated hyperactivated motility, tyrosine phosphoprotein content, acrosome reaction, and F-actin formation (flow cytometry), implying that PLC activity is enhanced during capacitation and contributing to these capacitation processes. In conclusion, we inferred that PLC ζ is activated during capacitation by tyrosine phosphorylation through a mechanism involving ATP1A4, contributing to capacitation-associated biochemical events.

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.

Cryopreservation of Semen from Domestic Livestock: Bovine, Equine, and Porcine Sperm

In modern livestock breeding, cryopreserved semen is routinely used for artificial insemination. Sperm cryopreservation allows for long-term storage of insemination doses and secures reproduction at a desired time point. In order to cryopreserve semen, it needs to be carefully processed to preserve its vital functions after thawing. In this chapter, we describe the processes involved in cryopreservation of bull, stallion, and boar sperm. These include preparation of diluents, dilution of sperm in primary and freezing extender, slow cooling from room temperature to 5 °C, packaging of insemination doses in straws, freezing at a defined cooling rate in liquid nitrogen vapor, cryogenic storage, and thawing. Two-step dilution approaches, with commonly used diluents, are presented, namely, TRIS-egg yolk (TEY) extender for bull sperm, skim milk (INRA-82) extender for stallion sperm, and lactose-egg yolk (LEY) extender for boar sperm. Furthermore, simple methods are presented for cooling and freezing of sperm at defined cooling rates.

Seasonal differences in seminal plasma proteins from two bovine breeds adapted to a subtropical climate

This study was designed to evaluate the seasonal expression of seminal plasma proteins from two bovine breeds adapted to a subtropical climate and their associations with post-thawing sperm and environmental characteristics. Semen samples were obtained three times in summer and three times in winter from four Crioulo Lageano and four Angus bulls. Seminal plasma was obtained by centrifugation, and the other portion of the semen was cryopreserved. Seminal plasma proteins were identified by 2D-nanoUPLC-MS^E. Post-thawing assessments of sperm kinetics, morphology and membrane integrity were performed. Environmental data such as air temperature, air humidity and black globe temperature (BGT) were recorded, and the temperature-humidity index (THI) was calculated in summer and winter. Results showed that the climate varied significantly between seasons. Although no statistical differences were observed in semen quality between breeds, the protein profiles varied within and between seasons. We suggest that the most critical proteins in summer affecting sperm characteristics were TIMP-2, DNase, Clusterin, CFAH and GPx6. TIMP-2 and DNase showed a higher abundance in Crioulo Lageano in comparison with Angus, while Clusterin, CFAH and GPx6 presented a lower abundance. To the best of our knowledge, this is the first report of a recently evolved type of glutathione peroxidase, GPx6, in seminal plasma of bovines. In winter, five proteins were considered to be more critical: BSP1, BSP3, CCL2, Sulfhydryl oxidase and TIMP-2. BSP1 and TIMP-2 showed a lower abundance while BSP3, CCL2 and Sulfhydryl oxidase presented a higher abundance in this season in Crioulo Lageano in comparison with Angus.

Antimicrobial activity of silver-carbon nanoparticles on the bacterial flora of bull semen

The spermicidal effects of silver nanoparticles (AgNPs) hinder its application in the field of artificial insemination. In this study, silver-carbon NPs (Ag@C NPs) was synthesized and applied as an alternative antibiotic agent for bull semen extender. Ag@C NPs were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption flame spectroscopy, transmission electron microscope (TEM), and high-resolution TEM (HR-TEM). Data analysis revealed the successful synthesis of Ag@C NPs with a particle size of 1-5 nm (average particle size of 2.5 nm) embedded into carbon. The antimicrobial activity of Ag@C NPs was tested against bacteriospermia of fresh semen collected from five fertile bulls (three ejaculates/bull). Escherichia coli (E. Coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) were isolated from fresh semen samples and identified by culture, staining, and conventional biochemical tests. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Ag@C NPs against bacteriospermia was determined at 5 and 37 °C. Ag@C NPs showed efficient antimicrobial activity (MIC: 3.125-12.5 μg/mL) against the tested strains and strong bactericidal effect on S. aureus, and P. aeruginosa (MBC: 3.125 μg/mL), with no detrimental effect (P ˃ 0.05) on the percentage of sperm motility (70.71 ± 4.82; 74.65 ± 4.46), plasma membrane integrity (68.39 ± 4.31; 72.38 ± 4.91), acrosome integrity (88.40 ± 13.21; 86.77 ± 14.23), and normal sperm morphology (86.85 ± 7.43; 87.82 ± 8.15) at concentrations of 15 and 30 μg/mL, respectively, after a cold storage of 48 h. However, Ag@C NPs showed a detrimental effect on sperm parameters in a dose dependent manner at concentrations ≥60 μg/mL. Ag@C NPs showed no adverse effect on the sperm's ultrastructure with limited sperm internalization at MIC. In conclusion, Ag@C NPs could be used as an alternative antibiotic agent for bull semen extender without a significant cytotoxic effect on the sperm during cold storage. However, further investigations for their effects on embryo production and female genitalia are still required.

Calves' management conditions affect sperm count in adult bulls

Background

Early maternal separation may have long-lasting physiological effects on different organ systems. Although long-lasting effects of early maternal separation are mostly studied in connection with the development and function of the central nervous system hypothalamic–pituitary–adrenal axis, animal health, behaviour and productivity, there is a lack of information about its impacts on the reproductive system. In the dairy industry, calves are often separated from mothers 1 or 2 days after birth and are not nursed. In the present retrospective study based on data from an artificial insemination (AI) centre, we compared semen parameters and fertility in bulls that were separated from their mothers one day after birth with the semen parameters of bulls that remained with their mothers and were nursed for approximately 2 months. Semen parameters were followed in 3 consecutive years in 52 maternally separated and 22 nursed bulls.

Results

Ejaculate volume and total sperm count in ejaculate were significantly higher in nursed bulls in comparison to maternally separated bulls at the age 25–36 and 37–48 months, but interestingly, not at the age 12–24 months, during the first year in the AI centre. Non-return rates did not differ between separated and nursed bulls.

Conclusion

The results suggest that early maternal separation causes long-lasting effects on the functioning of the male reproductive system, evident by reduced production of semen in adult bulls. The data suggest that with a standard of 20 million sperms per straw of frozen semen, 27–78 fewer straws can be obtained from one ejaculate of maternally separated bulls in comparison to the nursed bulls.

Evaluation of bovine sperm telomere length and association with semen quality

The study aimed to evaluate if the sperm telomere length can be considered as a new biomarker for sperm quality in bulls. Sperm Telomere Length was evaluated by Monochrome Multiplex Quantitative PCR in group A (n = 8) and group B (n = 8) bulls, classified according to standard semen analysis. Also, this parameter was measured before and after Percoll gradient separation within bulls that produced semen of satisfactory quality. Sperm telomere length, measured as T/S ratio (average ratio of telomere repeats copy number to a single copy gene), was higher in group A than in group B bulls (0.77 ± 0.03 vs 0.43 ± 0.06; P < 0.01). Sperm telomere length was positively correlated with motility, viability and membrane integrity, and it was negatively correlated with sperm anomalies. Furthermore, Percoll gradient selected sperms with higher T/S ratio than unselected sperms (1.19 ± 0.02 vs 0.67 ± 0.03). These results suggest that sperm telomere length can be used as a new marker of bovine semen quality.

Effects of Campylobacter fetus on bull sperm quality

Campylobacter fetus is a gram-negative, motile, spiral or S-shaped bacterium, which induces campylobacteriosis. This disease causes decrease productivity of cattle. Although considerable research has been done on the role of C. fetus on female fertility, little is known about the effect on bulls. The aim of this work was to evaluate the effect of C. fetus subsp. fetus (Cff) and C. fetus subsp. venerealis (Cfv) on bull sperm quality. Samples of frozen semen (n = 29 straws) were each distributed into three groups: two of them incubated with the microorganism (Cff, Cfv) and a control group. The proportions of live spermatozoa, with functional membrane and true acrosomal reaction in control group were significantly (P < 0.01) greater than those observed in Cff and Cfv groups. However, no significant differences (P > 0.05) were found in sperm chromatin structure among treatments. In adhesion assay, proportions of spermatozoa with adhered Campylobacter were similar for both subspecies. Results confirm that Cff and Cfv have the same ability to bind in an irreversible way to bull spermatozoa and to affect sperm quality. It is proposed that adherence could be considered as the main cause of sperm alterations, and also an important step of pathogenesis and venereal transmission.

The role of environmental optimization for storing bulls' sperm cells

Artificial insemination has achieved a dynamic increase in genetic progress, and this is due to the improvement of sperm preservation technology. In recent years, a lot of attention has been paid to optimizing bull sperm storage environment and objectifying methods of sperm quality analysis. This review presents bull sperm preservation methods and ways to modify their storage environment. The main purpose of sperm preparation for artificial insemination is to obtain sperm with a high percentage of viable, motile sperm with normal morphology and low DNA fragmentation rates. Currently conducted experiments indicate the possibility of improving the quality of insemination doses produced using various components enriching common diluents. However, despite extensive research, no better results have been achieved than obtaining insemination doses with sperm viability that exceeds just over 60%. Obtaining a very good quality of frozen semen seems to be still unachievable today.

Differences in sperm functionality and intracellular metabolites in Norwegian Red bulls of contrasting fertility

In the dairy breeding industry, prediction of bull fertility in artificial insemination (AI) is important for efficient and economically sustainable production. However, it is challenging to identify bulls with superior fertility applying conventional in vitro sperm assays. In the present study, sperm functionality was investigated to identify a multivariate model that could predict fertility. Two groups of young Norwegian Red bulls were selected, one with inferior fertility (18 bulls) and one with superior fertility (19 bulls) based on non-return rate after 56 days (NR56). Frozen-thawed semen doses were analysed for sperm chromatin integrity, viability, acrosome integrity, motility, and ATP content. A targeted approach was used to study intracellular concentrations of amino acids and trace elements in viable sperm cells. Significant differences between the two groups of bulls were observed, both for sperm functional attributes and intracellular concentrations of metabolites. Pearson correlation analyses indicated a negative relationship between NR56 and chromatin integrity parameters, DNA fragmentation index (DFI) and high DNA stainability (HDS). Several motility parameters correlated positively with NR56. The concentrations of cysteine and glutamic acid in sperm cells correlated negatively with NR56, while the concentrations of aspartic acid, leucine and serine showed a positive NR56-correlation. The sperm intracellular concentrations of the trace elements Fe, Al and Zn, correlated negatively with NR56. Correlations were observed between several sperm parameters and metabolites. Stepwise multiple regression analysis indicated that the best predictor of NR56 was a model containing %DFI, together with the intracellular sperm concentration of aspartic acid, Fe and Zn. This model explained 59% of the variability in NR56.

Effect of relaxin on cryopreserved beef bull semen characteristics

This study aimed to improve the quality of cryopreserved beef bull (Piedmontese) semen by incorporation of relaxin in diluted semen before cryopreservation procedures. Semen samples were collected from 4 proven fertile bulls, using artificial vagina, once per week for 8 consecutive weeks and pooled together then diluted with Bullxcell® extender, and supplemented with different concentrations of relaxin (0 (control), 25, 50 and 100 ng/ml) before cooling, equilibration and freezing procedures. Frozen semen was thawed and assessed for motility by Computer-Assisted Sperm Analysis and vitality parameters such as acrosome, plasma membrane and DNA integrities, apoptosis, mitochondrial membrane potential, mucus penetration and SOD activity. The developmental potential of bovine embryos produced in vitro by using relaxin-treated was also investigated. In the present study, 50 and 100 ng/ml relaxin incorporation in extended bull semen before cryopreservation induced a reduction of sperm motility immediately after thawing (0h), whereas, during long incubation periods (1-2 h), relaxin showed a significant positive effect on sperm quality by improving the sperm motility and velocity parameters. Interestingly, sperm vitality was improved by 25 and 100 ng/ml relaxin and the blastocyst developmental rate was significantly increased in the 25 ng/ml relaxin group compared with controls (52/118, 44.0% vs. 32/116, 27.6%, respectively). These findings suggest a potential use of relaxin at the doses tested in the present study as an additive in the cryopreservation media of bull semen to improve sperm quality.

Bull horn injury causing traumatic tooth intrusion - ultrasound and CT imaging

Introduction

Traumatic injury to upper alveolus may result in apical displacement of the affected tooth/teeth into the underlying alveolar bone. The tooth while being driven into the socket under the upwardly directed impact force usually causes a crushing fracture of the alveolar socket bone. The tooth may also be displaced through the labial plate of bone or may even impinge upon the bud of the permanent tooth.

Case report

We present a case of tooth intrusion due to bull horn injury and its imaging features on ultrasound and CT scan.

Discussion

Most common teeth involved in dental trauma in children of 6 to 12 year age group, are the maxillary anteriors, and this age group also constitutes the most common group in whom tooth intrusion is seen. Tooth intrusion usually involves a single dental element. Common etiologic causes are injuries, falls, sports accidents, violence and traffic accidents. Traumatic intrusion due to injury by animals is rarely described and is more commonly seen in less developed areas that too in rural set-up where man-animal encounters are frequent.

Conclusion

In such cases, whenever the conventional imaging modalities like the X-rays such as intra oral peri-apical views and orthopantomograms are unavailable, or where use of ionizing radiation is a grave concern (especially in children and pregnant patients), ultrasonography offers a non-invasive diagnostic imaging method which helps in diagnosis of the condition and also helps in supplementing the clinical information, thereby helping in better understanding of the underlying condition.

A comprehensive overview of bull sperm-borne small non-coding RNAs and their diversity across breeds

Background

Mature sperm carry thousands of RNAs, including mRNAs, lncRNAs, tRNAs, rRNAs and sncRNAs, though their functional significance is still a matter of debate. Growing evidence suggests that sperm RNAs, especially sncRNAs, are selectively retained during spermiogenesis or specifically transferred during epididymis maturation, and are thus delivered to the oocyte at fertilization, providing resources for embryo development. However , a deep characterization of the sncRNA content of bull sperm and its expression profile across breeds is currently lacking. To fill this gap, we optimized a guanidinium–Trizol total RNA extraction protocol to prepare high-quality RNA from frozen bull sperm collected from 40 representative bulls from six breeds. Deep sequencing was performed (40 M single 50-bp reads per sample) to establish a comprehensive repertoire of cattle sperm sncRNA.

Results

Our study showed that it comprises mostly piRNAs (26%), rRNA fragments (25%), miRNAs (20%) and tRNA fragments (tsRNA, 14%). We identified 5p-halves as the predominant tsRNA subgroup in bull sperm, originating mostly from Gly and Glu isoacceptors. Our study also increased by ~ 50% the sperm repertoire of known miRNAs and identified 2022 predicted miRNAs. About 20% of sperm miRNAs were located within genomic clusters, expanding the list of known polycistronic pri-miRNA clusters and defining several networks of co-expressed miRNAs. Strikingly, our study highlighted the great diversity of isomiRs, resulting mainly from deletions and non-templated additions (A and U) at the 3p end. Substitutions within miRNA sequence accounted for 40% of isomiRs, with G>A, U>C and C>U substitutions being the most frequent variations. In addition, many sncRNAs were found to be differentially expressed across breeds.

Conclusions

Our study provides a comprehensive overview of cattle sperm sncRNA, and these findings will pave the way for future work on the role of sncRNAs in embryo development and their relevance as biomarkers of semen fertility.

Vascular wall injury and inflammation are key pathogenic mechanisms responsible for early testicular degeneration during acute besnoitiosis in bulls

Background

Bovine besnoitiosis, caused by the apicomplexan parasite Besnoitia besnoiti, is a chronic and debilitating cattle disease that notably impairs fertility. Acutely infected bulls may develop respiratory signs and orchitis, and sterility has been reported in chronic infections. However, the pathogenesis of acute disease and its impact on reproductive function remain unknown.

Methods

Herein, we studied the microscopic lesions as well as parasite presence and load in the testis (pampiniform plexus, testicular parenchyma and scrotal skin) of seven bulls with an acute B. besnoiti infection. Acute infection was confirmed by serological techniques (IgM seropositive results and IgG seronegative results) and subsequent parasite detection by PCR and histological techniques.

Results

The most parasitized tissue was the scrotal skin. Moreover, the presence of tachyzoites, as shown by immunohistochemistry, was associated with vasculitis, and three bulls had already developed juvenile tissue cysts. In all animals, severe endothelial injury was evidenced by marked congestion, thrombosis, necrotizing vasculitis and angiogenesis, among others, in the pampiniform plexus, testicular parenchyma and scrotal skin. Vascular lesions coexisted with lesions characteristic of a chronic infection in the majority of bulls: hyperkeratosis, acanthosis and a marked diffuse fibroplasia in the dermis of the scrotum. An intense inflammatory infiltrate was also observed in the testicular parenchyma accompanied by different degrees of germline atrophy in the seminiferous tubules with the disappearance of various strata of germ cells in four bulls.

Conclusions

This study confirmed that severe acute besnoitiosis leads to early sterility that might be permanent, which is supported by the severe lesions observed. Consequently, we hypothesized that testicular degeneration might be a consequence of (i) thermoregulation failure induced by vascular lesions in pampiniform plexus and scrotal skin lesions; (ii) severe vascular wall injury induced by the inflammatory response in the testis; and (iii) blood-testis barrier damage and alteration of spermatogenesis by immunoresponse.

Impact of environmental contaminants on reproductive health of male domestic ruminants: a review

Environmental contaminants are gaining more attention in the livestock sector lately due to their harmful effects on productivity and fertility of livestock. Recent research indicates that many domestic ruminants are becoming subfertile/infertile due to confounding reasons associated with management. Contaminants like metals, metalloids, herbicides, pesticides, insecticides, chemicals, or natural contaminants are present everywhere in day to day life and are becoming a threat to the livestock. Studies on a broad-spectrum of animals suggest that high doses of acute or low doses of chronic exposure to the contaminants lead to disruption of multi-organs/systems including reproductive function. The lowered reproductive efficiency in animals is attributed to the endocrine disruptor activities of the environmental contaminants on the gonads, affecting gametogenesis and steroidogenesis. In vitro studies on testicular cells and the semen suggest that spermatozoa are more susceptible to damage by environmental contaminants. The quality of the semen happens to be a critical factor in the livestock industry. Contaminants affecting gametogenesis and steroidogenesis may lead to devastating consequences to the livestock reproduction, and thus the production. However, there is a lack of collective data on the effect of such environmental contaminants on the fertility of male domestic ruminants. This review discusses the studies related to the impact of environmental contaminants on male fertility in large (bull and buffalo) and small (sheep and goat) ruminants by focusing on the underlying molecular interactions between the contaminants and gonads.

Comparative expression of cell adhesion molecule1 (CADM1) in the testes of experimental mice and some farm animals

Cell adhesion molecule1 (CADM1) is a member of the immunoglobulin superfamily (IGSF) that has been found in mammalian testis and plays a substantial role in cell-to-cell interaction via either hemophilic (between spermatogenic cells) or heterophilic (between spermatogenic and somatic Sertoli cells) binding. The present study investigated the immunohistochemical localization of CADM1 in the testes of adult mice (Mus musculus), as well as sexually mature bull (Bos taurus), camel (Camelus dromedarius), and donkey (Equus asinus), using immunohistochemical techniques. The results revealed that CADM1 expression was observed in the spermatogonia and early spermatocytes as well as elongated spermatids in the mice testes; however, in the bull testis, its expression was restricted to the elongated spermatids. This expression was found in some of the early spermatocytes and elongated spermatids of the rutting camel testis but only found in the elongated spermatids of the non-rutting camel testis. Interestingly, CADM1 expression was detected in the spermatogonia, early spermatocytes, and elongated spermatids of the donkey testis. On the other hand, there was no expression of CADM1 observed in the Sertoli or interstitial cells. In conclusion, the expression of CADM1 during spermatogenesis differed among species and between rutting and non-rutting camel. Accordingly, this study emphasized the crucial role of CADM1 in the process of spermatogenesis and how it is related to sexual activity in both experimental and farm animals.

Intravenous infusion of kisspeptin increased serum luteinizing hormone acutely and decreased serum follicle stimulating hormone chronically in prepubertal bull calves

Kisspeptin (KP) is a hypothalamic neuropeptide that stimulates the secretion of gonadotropin releasing hormone. To determine the acute and chronic effects of KP on serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH), prepubertal bull calves [12 ± 1 (SD) weeks of age; 96.5 ± 14.5 kg BW] were administered one of four treatments [0.0 (control; CON), 0.125 (L-KP), 0.25 (M-KP), or 0.5 (H-KP) μg of KP/kg BW/hour] by intravenous infusion for 76 h. Blood samples were collected every 15 min for the first (acute; 1-6 h; Day 1) and last (chronic; 71-76 h; Day 4) 6 h of the intravenous infusions. Serum concentrations of LH and FSH were determined by radioimmunoassay. For each day, effects of treatment, time, and interactions on LH and FSH concentrations and pulse parameters were analyzed using procedures for repeated measures with JMP Software (SAS Inst. Inc., Cary, NC). There was a treatment effect (P = 0.002) and a treatment × time interaction during Day 1 (P = 0.02) such that LH concentrations were greatest following administration of all doses of KP when compared to CON. However, there was no treatment effect (P = 0.57) or a treatment × time interaction during Day 4 (P = 0.20) on serum LH concentrations. There was a treatment by day interaction (P = 0.02) on mean serum FSH concentrations. Most notably, on Day 4 mean serum FSH concentrations during intravenous infusion of M-KP and H-KP doses were less than that of CON. There was a treatment by day interaction (P = 0.0054) on FSH pulse amplitude concentrations, such that intravenous infusion of all doses of KP on Day 4 decreased FSH pulse amplitudes. In conclusion, acute infusion of KP increased LH concentrations and chronic infusion of KP decreased FSH concentrations. Despite the potential suppression of the hypothalamic-pituitary-gonadal axis with chronic infusion of KP, there are likely applications of KP, KP analogs, or KP receptor agonists to hasten the onset of puberty in livestock.

Selection for bull fertility: a review

Fertility is a critically important factor in cattle production because it directly relates to the ability to produce the offspring necessary to offset costs in production systems. Female fertility has received much attention and has been enhanced through assisted reproductive technologies, as well as genetic selection; however, improving bull fertility has been largely ignored. Improvements in bull reproductive performance are necessary to optimize the efficiency of cattle production. Selection and management to improve bull fertility not only have the potential to increase conception rates but also have the capacity to improve other economically relevant production traits. Bull fertility has reportedly been genetically correlated with traits such as average daily gain, heifer pregnancy, and calving interval. Published studies show that bull fertility traits are low to moderately heritable, indicating that improvements in bull fertility can be realized through selection. Although female fertility has continued to progress according to increasing conception rates, the reported correlation between male and female fertility is low, indicating that male fertility cannot be improved by selection for female fertility. Correlations between several bull fertility traits, such as concentration, number of spermatozoa, motility, and number of spermatozoa abnormalities, vary among studies. Using male fertility traits in selection indices would provide producers with more advanced selection tools. The objective of this review was to discuss current beef bull fertility measurements and to discuss the future of genetic evaluation of beef bull fertility and potential genetic improvement strategies.

A new paradigm regarding testicular thermoregulation in ruminants?

Increased testicular temperature reduces percentages of morphologically normal and motile sperm and fertility. Specific sperm defects appear at consistent intervals after testicular hyperthermia, with degree and duration of changes related to intensity and duration of the thermal insult. Regarding pathogenesis of testicular hyperthermia on sperm quality and fertility, there is a long-standing paradigm that: 1) testes operate near hypoxia; 2) blood flow to the testes does not increase in response to increased testicular temperature; and 3) an ensuing hypoxia is the underlying cause of heat-induced changes in sperm morphology and function. There are very limited experimental data to support this paradigm, but we have data that refute it. In 2 × 3 factorial studies, mice and rams were exposed to two testicular temperatures (normal and increased) and three concentrations of O₂ in inspired air (hyperoxia, normoxia and hypoxia). As expected, increased testicular temperature had deleterious effects on sperm motility and morphology; however, hyperoxia did not prevent these changes nor did hypoxia replicate them. In two follow-up experiments, anesthetized rams were sequentially exposed to: 1) three O₂ concentrations (100, 21 and 13% O₂); or 2) three testicular temperatures (33, 37 and 40 °C). As O₂, decreased, testis maintained O₂ delivery and uptake by increasing testicular blood flow and O₂ extraction, with no indication of anaerobic metabolism. Furthermore, as testicular temperature increased, testicular metabolic rate nearly doubled, but increased blood flow and O₂ extraction prevented testicular hypoxia and anaerobic metabolism. In conclusion, our data, in combination with other reports, challenged the paradigm that testicular hyperthermia fails to increase testicular blood flow and the ensuing hypoxia disrupts spermatogenesis.

Composition and diversity of the preputial microbiota in healthy bulls

Characterization of microbial communities inhabiting the reproductive tracts of cattle may lead to a better comprehension of bovine physiology and reproductive health. To date, reported studies have utilized culture-independent 16S ribosomal RNA (rRNA) for the classification of microbiota in the vaginal tract of cows but no studies have looked at the microbiota of the prepuce or penis of the bull. The aim of this study was to elucidate the microbiota present on the epithelial surface of the penis and prepuce of the post-pubertal bull using 16S rRNA gene sequencing. Ninety-two healthy bulls of a variety of ages and breeding history, presented for routine breeding soundness examinations, were utilized in this investigation. Bacteria belonging to Firmicutes, Fusobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria were identified in the prepuce. From all the bulls, two major community types were found, those with low or high bacterial species richness (up to 400 operational taxonomic units in one sample). There was no animal characteristic (breed or age) or management practice (feed type, antibiotic use, co-housing, breeding history) that was correlated with the bull penile microbial community composition. However, Bradyrhizobium was a distinguishing genus only found in the low diversity samples. The bull penile microbial community includes members of genera that are common in soil, cow vagina, respiratory tract, and feces. The baseline preputial microbial community in healthy bulls is described in the current study. This knowledge can be used later when investigating the interactions between disease and the male urogenital tract microbial community.