Yearling Beef Bulls Research Articles

A Longitudinal Characterization of the Seminal Microbiota and Antibiotic Resistance in Yearling Beef Bulls Subjected to Different Rates of Gain.

In this study, we evaluated the seminal and fecal microbiota in yearling beef bulls fed a common diet to achieve moderate (1.13 kg/day) or high (1.80 kg/day) rates of weight gain. Semen samples were collected on days 0 and 112 of dietary intervention (n = 19/group) as well as postbreeding (n = 6/group) using electroejaculation, and the microbiota was assessed using 16S rRNA gene sequencing, quantitative PCR (qPCR), and culturing. The fecal microbiota was also evaluated, and its similarity with seminal microbiota was assessed. A subset of seminal bacterial isolates (n = 33) was screened for resistance against 28 antibiotics. A complex and dynamic microbiota was detected in bovine semen, and the community structure was affected by sampling time (R2 = 0.16, P < 0.001). Microbial richness increased significantly from day 0 to day 112, and diversity increased after breeding (P > 0.05). Seminal microbiota remained unaffected by the differential rates of gain, and its overall composition was distinct from fecal microbiota, with only 6% of the taxa shared between them. A total of 364 isolates from 49 different genera were recovered under aerobic and anaerobic culturing. Among these seminal isolates were pathogenic species and those resistant to several antibiotics. Overall, our results suggest that bovine semen harbors a rich and complex microbiota which changes over time and during the breeding season but appears to be resilient to differential gains achieved via a common diet. Seminal microbiota is distinct from the fecal microbiota and harbors potentially pathogenic and antibiotic-resistant bacterial species. IMPORTANCE Increasing evidence from human and other animal species supports the existence of a commensal microbiota in semen and that this seminal microbiota may influence not only sperm quality and fertility but also female reproduction. Seminal microbiota in bulls and its evolution and factors shaping this community, however, remain largely underexplored. In this study, we characterized the seminal microbiota of yearling beef bulls and its response to the bull age, different weight gains, and mating activity. We compared bacterial composition between seminal and fecal microbiota and evaluated the diversity of culturable seminal bacteria and their antimicrobial resistance. Our results obtained from sequencing, culturing, and antibiotic susceptibility testing provide novel information on the taxonomic composition, evolution, and factors shaping the seminal microbiota of yearling beef bulls. This information will serve as an important basis for further understanding of the seminal microbiome and its involvement in reproductive health and fertility in cattle.

Assessment of Novel Semen Evaluation Technologies and Breed Comparisons in Yearling Beef Bulls

Objective: The objectives were 1) to evaluate the iSperm, when conducting breeding soundness exams (BSE) on bulls by comparing sperm motility to a technician’s assessment and 2) to evaluate correlations between sperm response to reactive oxygen species (ROS) and functional sperm measurements.

50 Long-term Motility of Semen Following Breeding Soundness Exams for Yearling Beef Bulls

Abstract To find an in vitro predictor of in vivoM/em&amp;gt; semen motility prompted this study. Our objective was to evaluate semen motility for an 8-hour period immediately following a breeding soundness exam. Ejaculates from 52 Angus and 56 Charolais bulls were evaluated. Motility, morphology, scrotal circumference and pH of ejaculate were evaluated at the time of collection. Ejaculates were then extended using a one to one ratio and incubated in a water bath held at 37 degrees Celsius and evaluated hourly. Motility was evaluated hourly for 8 hours, or until motility of the sample reached zero. Data were analyzed for breed and hourly effects using the GLIMMIX procedure of SAS. There was statistical evidence for difference (P &amp;lt; 0.0001) between breeds for motility over time. Angus ejaculates had higher pH values than Charolais ejaculates showing an association between breed and pH (6.82 vs 6.76, respectively). Primary spermatozoa abnormalities were greater (P &amp;lt; 0.0001) for Angus bulls compared to Charolais bulls (13.33% vs. 10.91%, respectively). Scrotal circumference between breeds tended to be different (P &amp;lt; 0.07), with Charolais bulls having a larger scrotal circumference compared to Angus bulls (38.29 vs. 38.03 centimeters, respectively). There was no difference (P &amp;gt; 0.05) between breeds for secondary abnormalities. There was a significant interaction (P &amp;lt; 0.01) between breed and time of motility measurement. Angus bull’s motility decreased drastically until hour 4, it then had a more gradual decrease until hour 8. Charolais bulls had a more gradual decrease in the percentage of motile sperm over time. In conclusion, there was evidence for difference between breeds for pH, primary spermatozoa abnormalities, and long-term motility, and a scrotal tendency. Understanding the effects of breed and individual biological factors may help producers adjust BSE expectations and lead to future research in long term semen motility.

PSI-39 Retrospective analysis of semen quality attributes of bulls in the Cal Poly Bull Test

Abstract The Cal Poly Bull Test has been offering valuable information for genetic improvement via a performance test of yearling beef bulls across the western United States since 1951. Growth and reproductive performance phenotypes were measured and collected over time. Therefore, the objective of this study was to determine the relationship between growth traits and semen quality traits. Performance records and semen samples of Hereford and Angus bulls were collected over a 12-year span from 2001–2013. A total of 1,982 records from Angus (n = 1692) and Hereford (n = 290) bulls were analyzed. All bulls were fall-born and weaned prior to the start of test in May. Bulls were fed for 99.83 ± 0.37 days in accordance with the guidelines of the Beef Improvement Federation where growth performance was assessed monthly during that period. After the conclusion of the test, usually in August, semen was collected from bulls and assessed for sperm motility, morphology and total sperm count. Bulls were retrospectively classified as low (0–1.4 kg), moderate (1.4–1.8 kg), or high (1.8–2.7 kg) average daily gain (ADG) bulls. The correlation among traits was evaluated using Pearson correlation, whereas a linear mixed model was used to evaluate the effect of growth on semen quality attributes. Bull age was moderately, negatively correlated (P &amp;lt; 0.01, r2 = -0.3) with scrotal circumference. Sperm motility and morphology were moderately correlated (P &amp;lt; 0.01, r2 = 0.35). Bull ADG was not strongly correlated (P &amp;lt; 0.01, r2 = 0.15) with semen motility or morphology. The results indicated a significant breed effect (P &amp;lt; 0.01) on semen motility and morphology. Angus bulls had a higher percent of progressively motile spermatozoa (P &amp;lt; 0.01; 72.23% ± 0.73) when compared with Hereford bulls (65.88% ± 1.37). Additionally, Angus bulls had a higher percentage of morphologically normal sperm (P &amp;lt; 0.01; 73.65% ± 0.59) when compared with Hereford bulls (66.29% ± 1.1). However, ADG as a class variable had no impact (P ≥ 0.50) on semen motility or morphology. Thus, these results indicate that higher levels of ADG during the testing period did not negatively impact semen quality attributes. More data must be collected to assess the biology behind the breed effects and validate the effect of body weight gain on semen quality attributes.

PSII-32 Effects of feeding 60% dried distillers grains plus solubles or the equivalent sulfur as calcium sulfate on hydrogen sulfide gas production in the rumen

Abstract Objective of this study was to evaluate the impact of feeding 60% dried distillers grains plus solubles (DDGS) or the equivalent sulfur from calcium sulfate (CaSO4) to yearling beef bulls on ruminal hydrogen sulfide (H2S). The hypothesis for this study was that bulls consuming elevated concentrations of sulfur in their diet will have an increase in H2S present in the rumen. Twenty-four crossbred beef bulls (10 months of age, BW=319.6 kg) were assigned one of three treatments 1) corn based diet containing 60% concentrate (CON, S=0.2%, n = 8); 2) diet containing 60% DDGS as a replacement for corn (DDGS, S=0.44% DM, n = 8); 3) CON diet+ equivalent sulfur of DDGS in diet added as CaSO4 (SULF, S=0.43%, n = 8). Bulls were individually fed in Calan gates at 2% of BW. Ruminal gas samples were taken via rumen puncture 4 to 6 hours post feeding on d0, 14 and 42. Concentrations of H2S were determined using hydrogen sulfide detector tubes which were connected to a volumetric gas pump (Gastec, Kanawaga, Japan). Data were analyzed as repeated measures using the MIXED procedures of SAS for effects of day, treatment, and a day × treatment interaction. A day × treatment interaction was present for ruminal H2S (P = 0.005). On d0, there was no effect of treatment (P = 0.97). Bulls fed DDGS or SULF had similar H2S concentration on d14 (P = 0.06), while animals fed CON had lower H2S concentration (P = 0.004). On d42, concentrations of H2S was greater in SULF than all other treatments (P£0.006), while DDGS was greater than CON (P£0.05). Elevated H2S in bulls fed the SULF treatment compared with the DDGS treatment may indicate that ruminal availability of sulfur (S) in CaSO4 was greater than that of the combination of sulfuric acid and S-containing amino acids present in DDGS.

59 Genotypic effects of a Dopamine receptor type-2 SNP on growth and semen quality in beef bulls exposed to a dopamine agonist

Abstract Ergot alkaloids (EA) share similar structural properties to neurotransmitters and are able to elicit physiological responses in cattle that consume them by binding receptors such as the Dopamine type-2 receptor (DRD2). A single nucleotide polymorphism (SNP) in DRD2, previously found to be correlated to prolactin (PRL) serum concentrations was evaluated for impact on growth traits and semen quality parameters. Yearling beef bulls were allowed to graze a diet containing (E+) (n = 41) or lacking EA (E-) (n = 43) over a four-year study. Blood samples and semen were collected every 21 or 28 d. Semen motility, morphology, body condition score (BCS), and scrotal circumference (SC) were recorded. Prolactin (PRL) serum concentrations were assessed by radioimmunoassay (RIA). Bulls were sacrificed from the first year at the end of a 126-day period or 60 days after removal of treatment. Testicles and epididymis were collected and immunohistochemistry was performed on testis, epididymis, and sperm cells. Tissues and cells were incubated in the presence or absence of primary antibody against DRD2 with a DAPI counterstain. Isolation of DNA was performed on sperm pellets from semen collected using DNAzol (Thermo Fisher Scientific, Waltham, MA, USA). Amplification of the DRD2 SNP region was performed by PCR and resulting products were assessed for genotype through restriction fragment length polymorphism (RFLP) analysis. These data show the presence of DRD2 in the testis, epididymis, and sperm cells; however, semen quality and growth traits did not differ across DRD2 genotype or treatment. Body condition (P = 0.0009), SC (P = 0.0053), and semen velocity (P = 0.0398) differed across period. As expected, consumption of EA resulted in decreased prolactin serum concentrations (P = 0.0240).

30 Genotypic effects of a Dopamine receptor type-2 SNP on growth and semen quality in beef bulls exposed to a dopamine agonist

Abstract Ergot alkaloids (EA) share similar structural properties to neurotransmitters and are able to elicit physiological responses in cattle that consume them by binding receptors such as the Dopamine type-2 receptor (DRD2). A single nucleotide polymorphism (SNP) in DRD2, previously found to be correlated to prolactin (PRL) serum concentrations was evaluated for impact on growth traits and semen quality parameters. Yearling beef bulls were allowed to graze a diet containing (E+) (n = 41) or lacking EA (E-) (n = 43) over a four-year study. Blood samples and semen were collected every 21 or 28 d. Semen motility, morphology, body condition score (BCS) and scrotal circumference (SC) were recorded. Prolactin (PRL) serum concentrations were assessed by radioimmunoassay (RIA). Bulls were sacrificed from the first year at the end of a 126-day period or 60 days after removal of treatment. Testicles and epididymis were collected and immunohistochemistry was performed on testis, epididymis, and sperm cells. Tissues and cells were incubated in the presence or absence of primary antibody against DRD2 with a DAPI counterstain. Isolation of DNA was performed on sperm pellets from semen collected using DNAzol (Thermo Fisher Scientific, Waltham, MA, USA). Amplification of the DRD2 SNP region was performed by PCR and resulting products were assessed for genotype through restriction fragment length polymorphism (RFLP) analysis. These data show the presence of DRD2 in the testis, epididymis, and sperm cells; however, semen quality and growth traits did not differ across DRD2 genotype or treatment. Body condition (P = 0.0009), SC (P = 0.0053), and semen velocity (P = 0.0398) differed across period. As expected, consumption of EA resulted in decreased prolactin serum concentrations (P = 0.0240)

Bovine dopamine type-2 receptor SNP has no effect on growth, semen characteristics and prolactin concentrations in beef bulls treated with a dopamine agonist

A dopamine type-2 receptor (DRD2) SNP, previously found to be correlated with serum prolactin (PRL) concentrations in cattle, was evaluated for impact on growth traits, serum prolactin concentration, and semen quality. Over a four-year period, yearling beef bulls were allowed diets containing or lacking ergot alkaloids (EA). Every 21 or 28 d semen was collected for semen motility and morphology assessment and blood samples were collected to measure serum PRL concentrations. In addition, body condition score and scrotal circumference were evaluated. Serum PRL concentrations were assessed using a radioimmunoassay. In the first year, all bulls were sacrificed at the end of a 126-day study. Testicles and epididymis were collected at the end of the study or 60 days after removal from treatment. Immunohistochemistry was performed on testis, epididymis, and sperm cells, incubated with or without a primary antibody for DRD2 and counterstained with DAPI. Isolation of DNA was performed on sperm pellets using DNAzol (Thermo Fisher Scientific, Waltham, MA, USA) methods. Polymerase chain reaction was performed to amplify the region of the DRD2 gene containing the SNP of interest. The products were subjected to restriction fragment length polymorphism analysis. Further, all samples were subjected to genotyping using a custom Taqman genotyping assay (Applied Biosystems, Foster city, CA, USA). The presence of DRD2 was detected in the testis, epididymis, and sperm cells. The DRD2 genotype was not associated with semen quality, serum PRL, or growth traits. Consumption of EA resulted in lesser PRL serum concentrations but had no effect on values for other variable examined.

Factors associated with yearling bulls passing subsequent breeding soundness evaluations after failing an initial evaluation.

OBJECTIVE To determine the proportion of yearling beef bulls classified as satisfactory potential breeders when reevaluated after failing an initial breeding soundness evaluation (BSE) and identify any factors at initial BSE that predicted satisfactory performance at reevaluation. DESIGN Retrospective observational study. ANIMALS 2,064 beef bulls between 11 and 14 months of age at first BSE, evaluated from 2006 to 2014. PROCEDURES For each bull, data on age (categorized by month), breed, and BSE findings were extracted from the medical records. Bulls were classified as satisfactory potential breeders if they met Society for Theriogenology standards at the initial BSE or up to 2 subsequent reevaluations. Generalized linear mixed models were generated to assess potential associations between certain variables at initial BSE and passing that evaluation or passing subsequent BSEs after initial failure. RESULTS 1,921 of 2,064 (93.1%) yearling bulls passed 1 of up to 3 BSEs. The proportion of yearling bulls that were not classified as satisfactory during initial BSE but were later classified as satisfactory was 143 of 287 (49.8%). A significant interaction was identified between bull age and breed in the probability of passing the initial evaluation. No variable, including breed, age, scrotal circumference per day of age, and spermatozoa morphology at initial BSE, significantly predicted passing subsequent reevaluations after failing an initial BSE. CONCLUSIONS AND CLINICAL RELEVANCE Age and breed information should be considered when deciding the age at which initial BSE should be scheduled for a yearling bull cohort.

Seminal plasma protein concentrations vary with feed efficiency and fertility-related measures in young beef bulls

Fertility-associated proteins (FAP) found in seminal plasma indicate sexual maturity, which appears to be influenced by feed efficiency in cattle. This study characterized FAP via proteomics and verified associations of these proteins with feed efficiency, body composition and fertility-related measures in yearling beef bulls. Assessments including testicular ultrasonography, infrared thermography, seminal quality, seminal plasma proteomics, carcass composition, and reproductive organ biometry were obtained. From a population of 31 bulls, the seven most and least feed efficient (efficient, inefficient) bulls were used for categorical comparisons. Correlations between FAP, productive performance and fertility-related measures were determined. These traits were also correlated with orthogonal factors summarized from the FAP. Efficient bulls had increased epididymal sperm-binding protein-1 and decreased concentration of protein-C inhibitor compared to inefficient bulls. Correlations between FAP with age, body size, body composition, reproductive organ biometry, scrotal temperature, and seminiferous tubule maturity are reported. Acrosin and cathepsin D increased with development of the testes and osteopontin increased with greater numbers of mature seminiferous tubules. Phosphoglycerate kinase-2 was higher in animals with a higher scrotum temperature and a higher prevalence of sperm morphology defects. The principal factor indicated that FAP variability concentrations were positively correlated with age, reproductive organ biometry, body size and composition. Our results indicate that FAP changes with body size and sexual development, and demonstrates differences in the proteomics of bulls with diverging feed efficiency. This is related to the delay in the sexual maturity of efficient young bulls.

Effects of label-dose permethrin administration in yearling beef cattle: I. Bull reproductive function and testicular histopathology

Pyrethroid administration to a wide variety of laboratory animals has been shown to cause detrimental effects on male fertility, including sperm quality, by means of endocrine disruption. The objective of this experiment was to study the effects of a commercial, permethrin-containing pour-on product on reproductive variables and testicular histopathology of yearling beef bulls. Black Angus bulls (n = 60; aged 369 ± 17 days; 511 ± 33 kg; 6.2 ± 0.5 body condition scores) were assigned to either (1) saline control (CON) or (2) permethrin pour-on administered at label dose (PYR). Blood samples were collected, and industry standard breeding soundness examinations (BSE), via electroejaculation, were performed on all bulls at 5 days before and 14 days after treatment. Progressive sperm motility and eosin-nigrosin–stained sperm were analyzed using high-power phase-contrast microscopy. Plasma testosterone concentrations were analyzed via radioimmunoassay. Bulls were slaughtered at 34 days, and one testicle per bull was randomly collected for histologic examination. Change in sperm motility between BSEs was not different because of treatment; sperm morphology however improved across treatments, but PYR bulls had less improvement in percent of head (P < 0.001) sperm abnormalities compared to CON, resulting in less improvement of primary abnormalities (P = 0.04). Nonetheless, morphological differences did not change the overall outcome for satisfactory breeder status. Change in testosterone concentration did not differ because of treatment. Histopathologic examination identified that testicular degeneration and tubule diameter did not differ as a result of treatment. It should be noted, however, that degeneration score (higher score having more degeneration) was positively correlated with primary abnormalities (P < 0.01; r = 0.35) and negatively correlated with normal sperm cells (P < 0.001; r = −0.43). In summary, these data indicate that a single use of permethrin at label dose in yearling Angus bulls results in minimal detrimental effects on sperm morphology but not to a degree that impacts the ability of bulls to pass a standard BSE.

Effect of semen collection by transrectal massage of accessory sexual glands or artificial vagina on the outcome of breeding soundness examinations of Italian yearling beef bulls

Although semen quality is one of the major traits that influence breeding soundness examination outcomes in bulls, field conditions occasionally do not allow for the collection of semen samples by means of an artificial vagina. The aims of the present study were to report the results of a large number of semen collections that were performed via the transrectal massage (TRM) of the accessory sexual glands of Italian yearling beef bulls and compare this semen collection method to the artificial vagina (AV) method in term of breeding soundness examination outcomes; furthermore, we determined whether the breed affected the semen characteristics. In the TRM group (n = 475), the semen samples were collected via TRM of the accessory sexual glands, and in the AV group (n = 502), the AV method was used. In the TRM group, semen samples were obtained from 81.3% of the bulls and penile protrusion was observed in 87.6% of the animals during semen collection. The sperm concentrations (920.5 ± 439.0 vs. 281.0 ± 259.8 × 106/mL) and the percentages of total abnormal spermatozoa (22.8 ± 15.0 vs. 18.8 ± 12.9) were significantly higher in the AV group than those in the TRM group. The percentage of bulls that did not meet the minimum requirement for normal cells (≥70%) was 6.2% higher in the AV group than that in the TRM group (P < 0.05). Moreover, the samples collected from Chianina bulls by TRM exhibited a lower percentage of motile sperm and a higher percentage of abnormal spermatozoa when compared with the other two breeds. The major drawbacks of the TRM technique were the inability to conduct complete evaluation of the libido and mating ability of the yearling bulls, a significant reduction of the number of spermatozoa collected, and an increase in the variability of the semen characteristics due to breed. In conclusion, despite the drawbacks, TRM guarantees that semen evaluation can be conducted in cases in which the semen samples cannot be collected with the AV method.

Impact of oral meloxicam administration before and after band castration on feedlot performance and behavioral response in weanling beef bulls

Two experiments evaluated the effects of band castration and oral administration of an analgesic in association with castration on performance and behavioral and physiological responses in yearling beef bulls. In Exp. 1 Angus and Charolais-crossbred bull calves (n = 127; 309.8 ± 59.04 kg BW) and in Exp. 2 Hereford, Angus, and Hereford × Angus crossbred bulls (n = 30; 300.8 ± 4.96 kg BW) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) band castration (BAND), 2) band castration with oral administration of meloxicam (BAND-MEL), and 3) sham castration (SHAM). The BAND and SHAM procedures were completed on d 0. The SHAM treatment consisted of all animal manipulations associated with band castration without band application. Meloxicam was administered on d -1, 0, and 1 (1.0, 0.5, and 0.5 mg/kg, respectively) via an oral bolus. Body weight and a subjective chute score (CS) were collected on d -1, 0, 1, 7, 14, and 21 (d 28 Exp. 1 only). In Exp. 2, jugular blood samples were collected immediately before castration and 24 h postcastration for substance P (SP) analysis. In Exp. 2, video documentation on d 0 was used to determine range of vertical head motion (DIST) on a subset of animals during treatment administration. In both experiments, ADG was similar (P ≥ 0.50) between BAND and BAND-MEL, but ADG in SHAM cattle was greater (P < 0.001) and tended (P = 0.07) to be greater than castrates in Exp. 1 and 2, respectively. In Exp. 1, CS did not differ (P ≥ 0.26) between BAND and BAND-MEL on any day, but castrates exhibited less desirable CS on d 1 and 28 than SHAM cattle. In Exp. 2, CS was not affected (P ≥ 0.41) by castration or the presence of meloxicam. In Exp. 2, DIST did not differ (P = 0.57) between BAND and BAND-MEL, but when pooled, castrates exhibited greater (P = 0.04) DIST than SHAM. In Exp. 2, plasma SP concentrations were similar between BAND and BAND-MEL (P = 0.81) and between castrates vs. sham cattle (P = 0.67). Results indicate no impact of meloxicam administration on performance or behavioral and physiological responses to band castration. However, there was a negative impact of castration on ADG and DIST.

Effect of nutrition on testicular traits of tropically adapted yearling beef bulls

The effects of different management practices on testicular development of young Bonsmara bulls fed a high energy (HE), medium energy (ME) and low energy (LE) diet after weaning were determined. Testicular histology and seminal traits were examined together with scrotal circumference (SC) development over an 84-day performance test trial period. The SC differed significantly (P &lt; 0.001) between HE-, ME- and LE-fed bulls. Seminal traits, such as semen concentration were significantly (P &lt; 0.001) lower in bulls fed the HE diet (1.3 ± 0.134) compared with those fed the ME diet (2.4 ± 0.18) and LE diet (2.6 ± 0.16). Similarly, linear movement of sperm was also affected by diet and movement was slower (P &lt; 0.05) in bulls fed the HE diet (1.7 ± 0.30) compared with bulls fed the ME diet (2.2 ± 0.31) and LE diet (3.1 ± 0.23). The percentage total major (P &lt; 0.001) and total minor (P &lt; 0.05) sperm defects were also greater in the HE-fed bulls (27.1 ± 6.82 and 7.4 ± 0.91) compared with the ME-fed bulls (9.7 ± 1.45 and 5.5 ± 0.87) and for the LE-fed bulls (5.4 ± 1.26 and 3.9 ± 0.58). Dietary energy level (P &lt; 0.05) influenced the percentage inactive seminiferous tubuli, with bulls fed the HE diet having 35% more seminiferous tubules classified as inactive compared with those bulls fed ME and LE diets. Scrotal fat deposits were higher (P &lt; 0.05) in bulls fed the HE diet (243.4 ± 21.59 g) compared with those fed the ME (110.0 ± 12.1 g) and LE (88.4 ± 9.65 g) diets. Feeding HE diets to young bulls probably reduces their reproductive potential.

Intraglandular injection of antibiotics for the treatment of vesicular adenitis in bulls

Two experiments were designed to determine the efficacy of intraglandular antibiotic treatment in beef bulls. Experiment 1 was designed to evaluate the glandular tissue reaction to intraglandular antibiotic treatment. Experiment 2 was conducted to determine the efficacy intraglandular injection of antibiotics for the treatment of naturally occurring cases of vesicular adenitis. Healthy beef bulls ( n = 15), 2 and 3 years of age, were randomly allocated to three equal treatment groups to receive 10% of the daily recommended parenteral dose of penicillin, ceftiofur, or oxytetracycline in a volume of 6 mL injected directly into one of the vesicular glands. Ultrasonography was performed before, immediately after, and at 24, 48 and 168 h after intraglandular injection. The size and hardness of vesicular glands injected with oxytetracycline was greater ( P < 0.01) than those injected with ceftiofur. Ultrasonographic pixel intensity increased ( P < 0.01) after treatment with antibiotics, especially after treatment with oxytetracycline or penicillin. In Experiment 2, yearling beef bulls with clinical vesicular adenitis ( n = 14) were referred to the Western College of Veterinary Medicine for treatment. Eight bulls had unilateral and six had bilateral vesicular adenitis. The most common isolate was Arcanobacterium pyogenes. Corynebacterium pseudotuberculosis was isolated from one bull. Bulls were subjected to rectal palpation and ultrasonography of the vesicular glands, semen collection by electroejaculation, and intraglandular treatment with ceftiofur ( n = 13) and if necessary, a second intraglandular treatment of penicillin ( n = 6). One bull was treated only with an initial intraglandular injection of penicillin. Bulls were evaluated once a week over 6 weeks by palpation of the glands, and evaluation of semen. All bulls recovered from vesicular adenitis after 3–6 weeks. There was a difference in the amount of pus ( P = 0.042), leukocytes ( P < 0.001) and blood ( P = 0.003) present in ejaculates from before treatment to 3 weeks after treatment. Pixel intensities in ultrasonographic images of healthy or affected vesicular glands, whether treated or untreated, did not change over time. Intraglandular injection of ceftiofur in yearling bulls via the ischiorectal fossa was effective for treating vesicular adenitis.

Genetic correlations between live yearling bull and steer carcass traits adjusted to different slaughter end points. 2. Carcass fat partitioning1,2

Partial carcass dissection data from 1,031 finished crossbred beef steers were used to calculate heritabilities and genetic correlations among subcutaneous, intermuscular, and body cavity fat percentage and marbling score adjusted to slaughter age-, HCW-, fat depth-, and marbling score-constant endpoints. Genetic correlations were also calculated among these fat partitions with live growth and ultrasound traits evaluated in yearling beef bulls (n = 2,172) and steer carcass measurements. Heritabilities of the different fat partitions ranged from 0.22 (marbling score-constant body cavity fat) to 0.46 (HCW-constant marbling score). Genetic correlations between subcutaneous fat and intermuscular fat (rg = 0.16 to 0.32) and between intermuscular fat and body cavity fat (rg = 0.38 to 0.50) were more highly associated than subcutaneous fat and body cavity fat (rg = -0.08 to 0.05), indicating that fat depots are not under identical genetic control. Adjusting fat depots to different end points affected the magnitude but usually not the sign of the genetic correlations. Bull postweaning gain was associated with intermuscular (-0.24 to -0.35), body cavity (-0.24 to -0.29), and marbling fat (-0.24 to -0.39) in steers. Bull hip height was associated with body cavity (-0.20 to -0.29) and marbling fat (-0.20 to -0.47) in steers. Bull ultrasound fat depth was associated with subcutaneous (0.11 to 0.29), intermuscular (0.05 to 0.36), body cavity (0.27 to 0.49), and marbling fat (0.27 to 0.73) in steers. Bull ultrasound intramuscular fat percentage was associated with subcutaneous (-0.22 to -0.44) and intermuscular fat (-0.06 to 0.31) in steers. Bull ultrasound LM area was associated with body cavity (-0.25 to -0.31) and marbling fat (-0.25 to -0.30) in steers. Ultrasound LM width measurements were negatively correlated with subcutaneous fat (rg = -0.09 to -0.18), intermuscular fat (rg = -0.53 to -0.61), body cavity fat (rg = -0.63 to -0.69), and marbling score (rg = -0.75 to -0.87) at slaughter age-, HCW-, and fat depth-constant endpoints; correlations were generally lower at a marbling score-constant end point (rg = 0.07 to -0.49). Ultrasound indicator traits measured in seedstock may be useful in altering fat partitioning in commercial beef carcasses.

Comparison between the Sperm Morphology in Semen Samples Obtained from Yearling Beef Bulls by Transrectal Massage of the Ampullae and Cauda Epididymal Dissection

As electroejaculation (EEJ) is prohibited for use on unanaesthetized animals in Sweden, there is a need for an alternative method of semen collection from bulls in the field. The aim of the present study was to evaluate the use of transrectal massage (TM) of the ampullae to collect semen from yearling beef bulls under field conditions in Sweden. Transrectal massage was performed on 52 yearling beef bulls. Volume of semen collected, duration of procedure, percentage progressively motile sperm, and sperm concentration were measured. Smears were prepared for sperm morphology examination. Semen samples were obtained from 47 of 52 bulls. Mean volume was 3.2 ml (SD +/- 3.7), mean duration of collection was 7.4 min (SD +/- 2.8), mean percentage progressively motile sperm was 43.5% (SD +/- 29.2) and mean concentration was 201.9 x 10(6) spermatozoa/ml (SD +/- 278 x 10(6)). Twenty-three of the 52 bulls were slaughtered 3-4 days after semen collection and aliquots of the cauda epididymal contents were collected for sperm morphology examination. The percentages of proximal droplets, abnormal tails and abnormal midpieces were significantly higher (p < 0.05) and the percentage of detached heads was significantly lower (p < 0.05) in the post-mortem samples compared with those in the TM samples. However, importantly there was no significant difference between the two sample types in the percentages of abnormal heads. This study demonstrates that semen can be collected from yearling beef bulls by TM. We think that TM constitutes a useful tool, when semen collection with EEJ or artificial vagina (AV) is not possible under field conditions, when included in the bull breeding soundness evaluation (BBSE) protocol. However, further studies are needed, and presently being carried out, to evaluate if semen samples collected by TM are comparable with semen samples collected by AV.

Genetic correlations among indicator traits for carcass composition measured in yearling beef bulls and finished feedlot steers

Genetic correlations were examined among 10 live growth and ultrasound traits measured in yearling beef bulls (n = 2172) and four carcass traits measured in crossbred finished feedlot steers (n = 1031). Heritabilities ranged from 0.13 (bull ultrasound longissimus muscle width) to 0.83 (yearling bull hip height). Genetic correlations indicated that selecting yearling bulls for increased growth rate and hip height would lead to higher carcass weight, increased longissimus muscle area and reduced levels of carcass marbling in steers. Bull ultrasound fat depth was positively associated with both carcass fat depth and marbling score. Most ultrasound longissimus muscle size measurements in bulls were positively associated with each other and with carcass longissimus muscle area in steers, but the magnitude of the genetic correlation with carcass measurements depended on the bull longissimus muscle size trait in question. This suggests that longissimus muscle shape in bulls may be related to carcass weight, fat and muscle traits in steers. Results confirm that while ultrasound is a valuable tool for the genetic improvement of carcass traits in beef cattle, genetic correlations between live bull ultrasound and steer carcass traits less then unity suggest that selection would benefit from multiple trait evaluations in situations where reliable carcass data are available. Key words: Ultrasound, beef carcass, heritability, genetic correlation

Fertility of yearling beef bulls during mating

Crossbred ( Bos taurus) yearling beef bulls were assessed for breeding soundness and physical traits prior to multi-sire natural mating at pasture. Bulls ( n = 60) were assigned to six groups of nine or 10 bulls and two bull-groups were rotated on 14-day intervals during a 63-day mating season in each breeding herd ( n = 3) of 191–196 cows. The remaining bulls ( n = 14) were maintained under similar environmental conditions without mating exposure. Bulls were observed during mating and assessed for breeding soundness and changes following mating. Bulls used for breeding (UFB) lost 77 kg of body weight and declined from body condition scores of 6 to 4.5, whereas bulls not used for breeding (NUB) maintained body condition scores of 6 and gained 27 kg. The UFB bulls incurred a 75% total injury rate with 63% incidence of lameness and 12% incidence of reproductive injuries, resulting in a 22% attrition rate. Only 45% were physically sound at the end of mating. Scrotal circumference declined in UFB bulls (−4.58%) and increased in NUB bulls (2.49%). From the 98% BSE-satisfactory rate (UFB) prior to breeding, only 61% were BSE-satisfactory post-breeding. The NUB bulls declined from 57 to 36% satisfactory. The BSE classification was influenced by significant increases in abnormal spermatozoa (primary and secondary), which was significantly associated with injuries incurred during mating. Group and breed differences in injury rates and BSE-status following mating were evident. Environmental conditions and mating activity influenced bull seminal quality and physical condition. Pregnancy rates in all three breeding herds (91–96%) were similar, with insignificant differences between bull-groups; the effects of physical and reproductive changes on individual bull fertility were immeasurable.

The Proportion of Beef Bulls in Sweden with Mature Spermiograms at 11–13 months of Age

Semen samples collected postmortem from 142 yearling beef bulls (11-13 months old) of three different breeds (Charolais, Hereford and Simmental) were examined to evaluate the proportion of bulls with mature spermiograms. Before slaughter, testes and epididymides were clinically examined and scrotal circumferences were measured. Aliquots of the cauda epididymal contents taken postmortem were used for sperm morphology examination. Sperm head morphology was studied in dry smears stained with carbol-fuchsine. For each preparation, 500 spermatozoa were counted in each smear under light microscope (x 1000). The presence of proximal cytoplasmic droplets, abnormal acrosomes, detached heads and abnormalities of the midpiece and tail were recorded in wet preparations of formol-saline-fixed spermatozoa. For each preparation, 200 spermatozoa were counted in each preparation under a phase-contrast microscope (x 1000). The abnormalities were classified according to a classification system developed by Bane (1961). Morphological abnormalities were recorded as a percentage of the total number of counted spermatozoa. Criteria for a spermiogram to be considered mature included <15% abnormal heads and <15% proximal droplets. According to this definition approximately 48% (68 of 142) of the examined bulls were considered mature. The bulls in this study represent approximately one-fifth of the total amount of performance-tested beef bulls in Sweden during 5 years. Our results indicate that only less than half of the Swedish yearling beef bulls at the testing station appear to have a mature spermiogram at the time they are offered for breeding purposes.