Breeding Soundness Research Articles

A description of biosecurity practices among selected dairy farmers across Australia

Aims The study investigated critical biosecurity control points and dairy farmers’ motivations towards biosecurity practices among selected dairy farmers across Australia. Methods A questionnaire template was administered via an online survey. A three-stage process was used to develop the questionnaire by pooling of potential questions, selection and reduction of the questions to fit an 8–10 min survey. Key results A total of 55 responses were obtained. Mixed species rearing was practiced on 69% of the farms, with a majority keeping either sheep or beef cattle within the same property as dairy cattle. Approximately half of the farms (49%) did not provide formal training to new staff on aspects of animal health, as well as not conducting bull breeding soundness. Most of the farms (98%) required staff to use personal protective equipment, such as overalls and gumboots, but only a few of the farms (34%) had designated areas to clean footwear and a system for recording visitors (17%). Record keeping pertaining to animal health, maintenance of good fences and use of vendor declaration forms was practiced in a majority of the farms. The practice of quarantining new stock before mixing with other stock was practiced in only 45% of the farms. Monthly herd health visits by a veterinarian were utilised by 55% of the farms. Multivariable analysis showed positive significant associations between mixed species rearing with the practice of regular pest control (P = 0.004) and use of footbaths (P = 0.024) and no biosecurity plan (P = 0.025). Furthermore, a positive significant association was also recorded on the presence of a biosecurity plan and the presence of a designated area to clean footwear (P = 0.002) and no regular deworming (P = 0.024). Animal and human health reasons were the main motivators for implementing and maintaining ‘best practice’ biosecurity practices, whereas government regulation was the lowest motivator. Conclusions It is concluded that the biosecurity practices were variable, and animal and human health reasons were the primary motivators for instituting biosecurity practices. Implications There is a need to continue educating farmers on the importance of biosecurity practices.

204 Relationships between semen quality and scrotal circumference, adiposity, and rumen conditions of developing bulls

Abstract Growing concern over breeding soundness examination failures has led to increased interest in identifying factors that may influence semen quality of developing bulls. An experiment was conducted to evaluate relationships between semen quality and scrotal circumference, adiposity, and rumen conditions of Angus bulls (n = 48; 332 ± 47 d of age) that were developed over an 84-d period. Bulls underwent breeding soundness examinations at each of four 21-d intervals. Backfat thickness was measured on d 0 and 84, and rumen pH and temperature were continuously monitored throughout the experiment via rumen boluses (eBolus; eCow, Devon, UK). Simple linear regression was conducted (JMP 13.0; SAS Institute Inc., Cary, NC) to determine independent relationships between semen characteristics and respective explanatory variables. Change in scrotal circumference between d 0 and 84 was directly related to change in percent morphologically-normal sperm (R2 = 0.12; P < 0.05), but no other semen quality characteristics (P ≥ 0.17). Change in backfat thickness throughout the experiment tended to be inversely related to change in percent morphologically-normal sperm (R2 = 0.06; P < 0.10), but was directly related to changes in semen volume (R2 = 0.10; P < 0.05) and total sperm per ejaculate (R2 = 0.12; P < 0.05), but not change in motility (P = 0.24). Mean rumen pH tended to be directly related to changes in semen volume (R2 = 0.07; P < 0.10) and total sperm per ejaculate (R2 = 0.07; P < 0.10), but not changes in motility (P = 0.28) or percent morphologically-normal sperm (P = 0.94). Mean rumen temperature was not related to any semen quality characteristics (P ≥ 0.15). Collectively, these results suggest that rumen pH, as well as changes in scrotal circumference and adiposity are related to and independently explain variation in semen quality of developing bulls.

Use of a new artificial vagina without a liner reduced sperm motility in a stallion

A 24 year old Tennessee Walking Horse stallion was presented at beginning of breeding season for a sudden decrease in sperm motility noticed 1 hour after semen was collected with a new artificial vagina. Stallion was healthy and previous breeding soundness examinations indicated no signs of subfertility. Collection procedure, processing temperature, semen extender addition, and seminal plasma exclusion were examined as possible causes. None identified the reason for reduced motility. When the same artificial vagina, with or without a liner, was used to collect semen from this stallion and 2 other stallions, sperm motility increased for all 3 stallions when a liner was used. Therefore, the new artificial vagina was regarded as the cause of decreased sperm motility.

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.

Evaluation of the effect of laboratory methods on semen analysis and breeding soundness examination (BSE) classification in stallions

The stallion Breeding Soundness Examination (BSE), as proposed by the Society for Theriogenology, recommends that a stallion produce a minimum of one billion progressively motile, morphologically normal sperm (PMMNS) in the second of two ejaculates collected 1 h apart to be classified as a Satisfactory Prospective Breeder. With this in mind, the first objective of this study was to determine if the classification outcome of the traditional BSE differs depending on the methods used to evaluate sperm motility, morphology and concentration. We hypothesized that application of Computer Assisted Sperm Motion Analysis (CASA) and Differential Interference Contrast (DIC) microscopy to stallion semen evaluation would yield a more conservative estimate of the number of PMMNS. If this hypothesis is correct, then the use of CASA and DIC microscopy for semen evaluation would result in significantly fewer stallions meeting the historical standards for classification as a Satisfactory Prospective Breeder. Additionally, we determined whether the use of these modern technologies resulted in more accurate prediction of the actual fertility of a stallion compared to the use of more traditional technologies. Our results support the hypothesis that modern semen analysis techniques (including CASA and DIC microscopy) result in more conservative estimates of the number of PMMNS when compared to standard semen analysis techniques. As a result, the choice of methods used for semen analysis may impact the outcome of the traditional BSE. However, none of the methodologies used in this study reliably predicted different levels of fertility among this group of moderately to highly fertile stallions within the context of the traditional BSE. Additionally, the only individual semen measure that was significantly correlated with fertility was the percentage of morphologically normal sperm as determined using DIC microscopy. These results caution against strict use of the traditional ‘cutoff’ of 1 billion PMMNS for classification of breeding potential, particularly when attempting to differentiate between moderately and highly fertile stallions and regardless of the laboratory methods employed for semen analysis.

138 The Tifton Bull Evaluation Program: A 5-year review

Abstract The Tifton Bull Evaluation Program is an educational program that utilizes an investment and reward system to convey livestock selection, nutrition, and data management education to beef cattle producers. The program is held annually at the Tifton Bull Evaluation Center in Irwinville GA. Consignors are required to pay nomination and testing fees to cover the cost of bull development. At 28 d intervals, BW is collected and used to calculate ADG, and weight per day of age (WDA). Carcass ultrasound data, scrotal circumference and beginning and ending hip height are also collected. At the end of the 112-d test, bulls in approximately the top two-thirds of each breed based on an index of ADG and WDA, and meet all standards for health and breeding soundness, are eligible for the sale. In the last 5 years, 769 bulls have been tested at Tifton. The respective sales resulted in 847 people having registered to bid with 329 actual buyers from 7 states purchasing 504 bulls for a total of $1,672,800. As expected, Angus accounted for most bulls tested (48.7%) and sold (49.2%) with the average Angus bull worth $3,508, $195 more than the 5-yr average. Breeds with less than 5 entries per year were assigned to a single breed group (AOB). Bulls in the AOB group were the least valuable (average = $2,482) averaging $831 below the 5-yr average price. Lower feed costs have helped the program reduce test fees from $940 per bull in 2014 to a low of $760 and $765 per bull in 2017 and 2018; however, sale fees have risen from 3.39% in 2015 to 7.29% in 2018. No large changes have been noted in bull performance or carcass ultrasound parameters across years. Consignors have reported positive experiences with the program overall

Kinematic and head morphometric characterisation of spermatozoa from the Brown Caiman (Caiman crocodilus fuscus)

The development of analytical methods for the evaluation of crocodilian semen is an important component for the assessment of male breeding soundness and the development of assisted breeding technology in this taxon. Computer-Assisted Semen Analysis (CASA) technology is becoming an increasingly common technique in seminal evaluations for animals but there has been no application of this technique for reptilian spermatozoa. The aim of this study was to analyse sperm kinematic and morphometric variables in Caiman crocodilus fuscus semen samples and to determine whether there were sperm subpopulations. Four ejaculates from four sexually mature captive caimans were used for this study. A CASA-Mot and CASA-Morph system was used with an image acquisition rate of 50 Hz for 2 s of capture. The ISAS®D4C20 counting chambers were used and spermatozoa incubated at 25 °C. Total and progressive motilities did not differ among animals (P > 0.05). There was a significant animal effect in the model with respect to sperm morphometry, and kinematic indices including linearity (LIN) and straightness (STR) (P < 0.05). Results for principal component (PC) analysis indicated variables were grouped into four components: PC1 related to velocity, PC2 to progressivity, PC3 to oscillation and PC4 to sperm path cross-linking. Subpopulation (SP) structure analysis indicated there were four groups, namely, rapid non-progressive (SP1), slow non-progressive (SP2), rapid progressive (SP3) and medium progressive (SP4), representing 14.5%, 45.4%, 18.7%, and 21.4% respectively. Findings in the present study indicate the importance of continuing development of reliable protocols regarding the standardisation of computer-based semen analyses in reptilian species.

Breeding bulls as a potential source of bovine leukemia virus transmission in beef herds.

To determine the prevalence of bovine leukemia virus (BLV) in beef bulls; evaluate the presence of BLV provirus DNA in blood, smegma, and semen samples; and analyze whether blood BLV proviral load was associated with differential blood cell counts. Observational cross-sectional study. 121 beef bulls ≥ 2 years old from 39 Michigan herds. Blood, smegma, and semen samples were collected from each bull during a routine breeding soundness examination. An ELISA was used to detect serum anti-BLV antibodies. A coordination of common motifs-quantitative PCR assay was used to detect BLV provirus DNA in blood, smegma, and semen samples. Bulls with positive results on both the BLV serum ELISA and coordination of common motifs-quantitative PCR assay were considered infected with BLV. 19 of 39 (48.7%) herds and 54 of 121 (44.6%) bulls were infected with BLV. Provirus DNA was detected in the blood of all 54 and in smegma of 4 BLV-infected bulls but was not detected in any semen sample. Lymphocyte count was significantly greater in BLV-infected bulls than in uninfected bulls. The proportion of BLV-infected bulls with lymphocytosis (16/54 [29.6%]) was greater than the proportion of uninfected bulls with lymphocytosis (6/67 [9%]). Lymphocyte count was positively associated with BLV proviral load in BLV-infected bulls. Results indicated that almost half of beef bulls and herds were infected with BLV, and BLV provirus DNA was detected in the smegma of some BLV-infected bulls. Bulls may have an important role in BLV transmission in beef herds.

Testicular function and fertility in bulls

Summary. Since one bull may be responsible for impregnating numerous cows, testicular function and fertility are of critical importance. Within this broad context, this review will focus on: the effects of nutrition on reproductive development; scrotal/testicular thermoregulation; breeding soundness; and sperm function/fertility. Bulls fed above-maintenance levels of energy and protein before 30 wk of age had increased luteinizing hormone pulse frequency, hastened puberty, and increased testicular size at maturity (compared to those that were underfed during this interval). However, after 30 wk of age, supplemental nutrition generally did not improve reproductive potential (but sometimes decreased it). There are several mechanisms (including blood vessels) that maintain a bull's testes 2 to 6 °C cooler than core body temperature for production of fertile sperm (increased testicular temperature reduces semen quality). Although fertility varies substantially among bulls, it is generally easier to identify bulls with low fertility than to accurately distinguish among bulls with good to excellent fertility. Compensable sperm abnormalities can be overcome by increasing the number of sperm used for artificial insemination; these abnormalities are attributed to sperm failing to reach and penetrate the zona pellucida. In contrast, increasing the insemination dose will not improve fertility for uncompensable defects, implying that these sperm are able to cause fertilization and initiate development, but they do not sustain embryogenesis.

Disruption of bovine sperm functions in the presence of aplastic midpiece defect.

Bulls are of great importance in the productive chain and for this reason they should have a good semen quality. There is no doubt that sperm morphology is very important to bull fertility, although little is known about how exactly the abnormal morphologies may affect sperm functions. To detail the morphological description of the aplastic midpiece defect (AMD), as well as to understand its consequences for male fertility based on membrane and acrosome status, mitochondrial membrane potential and DNA integrity parameters. The bulls were divided into two groups: control, consisting of satisfactory potential breeders (n=3); and AMD, consisting of unsatisfactory potential breeders with a high percentage of AMD (n=3). Bulls were evaluated by the breeding soundness evaluation; five ejaculates were collected from each animal and analyzed by flow cytometry. Spermatozoa from AMD group exhibited lower sperm motility and vigor (p<0.05). In addition, it also exhibited lower mitochondrial membrane potential (p<0.05), a higher percentage of spermatozoa with DNA fragmentation (p<0.05), lower acrosome and plasma membrane integrity (p<0.05), and higher lipid bilayer sperm membrane disorganization (p<0.05) in comparison with control bulls. These findings may be due to oxidative stress and a reduction of the energy production capacity in addition to an alteration in the structural composition of the sperm cell. Moreover, semen with a high percentage of AMD may also be undergoing apoptosis. Bulls with a high percentage of AMD in their semen are not suitable for reproduction. Furthermore, it suggests there is a putative genetic basis for this sperm defect.

Effect of testicular consistency on semen quality of Murrah buffalo breeding bulls

The present study was conducted to find out the effect of testicular consistency on semen quality of Murrah buffalo breeding bulls. For this study, 64 mature Murrah buffalo breeding bulls, which were in regular semen collection, were selected. Four ejaculates from each bull were evaluated for semen quality attributes viz. ejaculate volume (EV, ml), mass motility (MM, 0-5), sperm concentration (SPC, million/ml), sperm motility (SM, %), viability (%) and sperm abnormality (SA, %). Testicular consistency was measured by palpation of the testis and categorised them as soft, moderate and firm state; the bulls were also grouped on the basis of testicular consistency as soft, moderate and firm group. The results revealed that EV, MM, SPC, SM, sperm viability and SA did not show any significant difference among the groups , however better quality semen was obtained in soft testicular group than firm and moderate groups. From this study it can be concluded that the bulls having soft testicular consistency produced better quality semen, therefore testicular consistency can also be included in routine breeding soundness evaluation of buffalo bulls.

Effect of scrotal bifurcation on breeding soundness traits in Beetal bucks during summer season.

Relationship of scrotal bifurcation or splitness with breeding soundness traits was investigated in 15 Beetal bucks (17-20months of age and 48.72 ± 1.57kg mean BW). Breeding soundness traits of conjoined/unsplit (n = 6) scrotal bucks was compared with split (n = 9) scrotal bucks having lengthwise > 1in. bifurcation. Two consecutive semen ejaculations per buck were collected at monthly interval during summer season (April to June 2018) using intact buck as teaser and sexual behavior was simultaneously recorded. Scrotal morphometry parameters, i.e., scrotal circumference, scrotal volume, scrotal skin thickness, testis length, width, and thickness were also recorded. Bucks with split scrotum had relatively more scrotal dimensions (scrotal circumference (P < 0.01), scrotal volume (P < 0.01), testis length (P < 0.01)) than conjoined scrotal bucks. Among various semen attributes, semen volume of first ejaculate (P < 0.01), second ejaculate (P < 0.05), mean semen volume (P < 0.01), total sperm count of first ejaculate, and mean sperm count of both ejaculates were more (P < 0.01) in split scrotal bucks. However, scrotal bifurcation had no influence on sexual behavior of bucks. It is concluded that Beetal bucks with split scrotum had relatively better breeding efficiency traits than conjoined scrotal bucks.

Reproductive behavior in hair sheep rams under tropical conditions.

The reproductive efficiency of sheep herds depends to a great extent on the ram. Male reproductive evaluation allows to select for the best and eliminate those with reproductive problems. The objective was to evaluate the effect of breed and age group on the reproductive behavior of hair sheep rams in the tropics of Mexico. Pelibuey (n = 42), Blackbelly (n = 30), Dorper (n = 44), and Katahdin (n = 30) rams of two age groups: young (n = 74, 1-1.5years old) and adult (n = 72, 2-4years old) were evaluated. Serving capacity (10-min duration) and breeding soundness evaluation (BSE) tests were carried out in each ram. In the first test, rams were classified as suitable and unsuitable, and in the BSE test, they were classified as satisfactory, questionable, or unsatisfactory. The response variables were analyzed using chi-square test or analyses of variance (ANOVA). ANOVA included the fixed effects of breed, age group, and their interaction. In the serving capacity test, 79.5% of the rams were considered suitable, with no breed differences (P > 0.05). Adult rams (90.3%) had the highest proportion of suitable rams (P < 0.05). In the BSE test, 80.2% of the rams were satisfactory; only breed being significant (P < 0.05). Pelibuey breed had the highest proportion of satisfactory rams (91.4%). Breed × age interaction was no significant for any trait. After serving capacity and BSE tests, a high proportion of rams was found not suitable for reproduction (36.3%), which is expected to cause low fertility in the flock.

Scrotal circumference, bodyweight and semen characteristics in growing dairy-breed natural-service bulls in Tasmania, Australia

ABSTRACTAims: To provide herd managers with a set of decision rules allowing them to predict the likelihood that a juvenile bull is ready for Bull Breeding Soundness Evaluation (BBSE), or breeding, if bodyweight and scrotal circumference are known.Methods: This was a longitudinal study following two groups of young pasture-fed Holstein and Jersey bulls from northwest Tasmania, Australia. Individual scrotal circumference, bodyweight and semen characteristics were recorded at 6–8 weekly intervals, from 6–18 months of age. Classification and regression tree analyses were used to predict the probability that a bull had ≥70% normal sperm morphology based on scrotal circumference and bodyweight measurements.Results: Overall 1,661 scrotal circumference and bodyweight measurements were obtained, and 518 semen samples from 356 bulls were assessed for sperm morphology, from 16 examination sessions that took place between 29 May 2015 and 17 August 2016. Classification and regression tree analyses generated a decision tree for Holstein bulls with four node endpoints, and for Jersey bulls with three node endpoints. Diagnostic test performance showed that for Holstein bulls, using the node endpoints of scrotal circumference ≥27 cm and bodyweight ≥349 kg, 98% had ≥70% normal sperm (positive likelihood ratio 10.4; 95% CI = 2.7–41), and using the node endpoints of scrotal circumference ≥27 cm and bodyweight between 282–349 kg, 89% had ≥70% normal sperm (positive likelihood ratio 1.6; 95% CI = 0.9–2.6). For Jersey bulls, using the node endpoints of bodyweight ≥259 kg and scrotal circumference ≥29 cm, 88% had ≥70% normal sperm (positive likelihood ratio 3.4; 95% CI = 1.6–7.0).Conclusions: This study provides a set of relatively simple decision rules based on bodyweight and scrotal circumference measurements that allows herd managers to assess the likelihood that juvenile bulls are ready for BBSE or breeding.Abbreviations: BBSE: Bull breeding soundness evaluation; BRT: Boosted regression tree

Testicular Color Doppler Ultrasonography in Barki Rams

The aim of the present study was to determine the blood flow dynamics of the testes of pre and post pubertal clinically normal Barki rams. Rams (n=8) were divided into two equal groups according to age. The first group was pre-pubertal rams (aged 4-6 months) and the second group was post pubertal sexually mature rams (aged 18-24 months). Doppler indices such as resistive index (RI), pulsatility index (PI) of the supra-testicular artery (STA) and marginal artery (MA) were measured by color and spectral Doppler ultrasonography of the scrotum and spermatic cord region. Blood samples were collected and serum testosterone level was evaluated. Results revealed that there was no significant difference (p > 0.05) between the two age groups of Barki rams in blood flow parameters of supra-testicular artery and marginal artery. Even though, Serum testosterone was significantly higher in the post pubertal group (p < 0.05). In conclusion, the sexual maturity in the rams was associated with significant changes in testosterone concentration but not in Doppler indices. Moreover, Doppler ultrasound can be used during the breeding soundness reproductive examination and before reproductive surgical interference in Barki rams.

A two-injection prostaglandin F2α presynchronization treatment decreases pregnancy rates of cycling replacement beef heifers.

Improving artificial insemination (AI) pregnancy rates in replacement heifers improves the genetic advancement within a herd. Heifers that have completed at least three estrous cycles prior to breeding have greater pregnancy rates compared to acyclic females. Therefore, it was hypothesized that a presynchronization treatment program consisting of two injections of prostaglandin F2α (PGF2α) prior to the start of the CO-Synch + 5 d CIDR protocol would initiate earlier attainment of puberty and more estrous cycles prior to AI, thus increasing AI pregnancy rates. All heifers were managed the same at two locations over the course of 2 yr. Heifers were randomly assigned to receive either the two-injection PGF2α presynchronization treatment (PreSynch; n = 105) or no presynchronization (Control; n = 106) prior to the start of estrous synchronization. On the first day of the trial, reproductive tract scores (RTSs), pelvic areas, body condition scores, and weights were collected on all heifers. All heifers were synchronized with the CO-Synch + 5 d CIDR protocol and fixed-time artificially inseminated with semen from a bull of known fertility. Blood samples were collected three consecutive times at 7 d intervals starting 45 d prior to estrous synchronization to determine the onset of puberty via analyzing progesterone concentrations. Pregnancy status to AI was assessed using ultrasonography diagnosis at approximately 30 and 60 d post insemination. Data were analyzed using PROC MIXED of SAS and reported as least square mean. The PreSynch treatment decreased AI pregnancy rates (52.2% vs. 38.1 ± 6.3% for Control vs. PreSynch, respectively; P = 0.06) and did not result in earlier attainment of puberty in beef heifers (P > 0.05). The PreSynch treatment did not impact pregnancy rates in heifers with an RTS of 3 or 4 (P > 0.05). However, PreSynch heifers with an RTS of 5 had decreased pregnancy rates (68.3% vs. 46.9 ± 10.1% for Control vs. PreSynch, respectively; P < 0.05). Finally, PreSynch heifers with increased body condition of 6 had decreased pregnancy rates when compared to Control heifers (37.5% vs. 62.5 ± 11.6%, respectively; P < 0.05). On the basis of these data, implementation of heifer breeding soundness examination at least 3 wk prior to the start of the breeding season may be beneficial for selecting replacement females; however, presynchronization with prostaglandins immediately prior to estrous synchronization will negatively affect AI pregnancy rates in cycling pubertal heifers.

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.

Evaluation of bull breeding soundness examination

Records from 2,887 bull breeding soundness examination conducted at Michigan State University from 2007-2017 were analyzed to validate, verify, and evaluate the process. All bulls were examined using Society for Theriogenology Bull Breeding Soundness guidelines. With a conservative α of .001, nominal logistic regression was used to identify influential factors and potential sources of bias, and determine predictive accuracy of the breeding soundness examination itself in classifying reproductive potential. Of 2,887 records evaluated, 82% of bulls were classified as satisfactory potential breeders, 3% unsatisfactory, and 15% deferred. Factors identified as influential in final classification of bulls included season, veterinarian bias, presence of white blood cells, and percent morphologically normal sperm. Season of year and presence of white blood cells in ejaculate significantly affected the outcome. Routine and consistent evaluation of bulls is important for economic success of beef cow-calf operations. Further studies are needed to determine if the seasonal effect is related to ambient temperature or underlying physiology of spermatogenesis in the bull. Some components of the breeding soundness examination may be unnecessary. We concluded that veterinarians and farmers could save time and money by reducing the number of data collection points while increasing reproductive potential of the herd by using only influential factors in the process. Breeding soundness examination has been useful in evaluation of reproductive potential in bulls; however, alternate formulas of reproductive potential may have higher predictive accuracy and validity and may be more cost effective.

Relationship of testicular biometry with semen variables in breeding soundness evaluation of Nellore bulls

This study aimed to evaluate the correlation between testicular biometry and semen variables, as well as, to relate testicular variables to the probability of selecting Nellore bulls with desirable sperm morphology when conducting breeding soundness evaluations (BSE). A total of 2055 BSEs from 506 bulls comprised the dataset. Biometric variables evaluated were: scrotal circumference, testicular volume, width, length, ratio and eccentricity; and semen variables were sperm motility, major sperm defects, minor sperm defects and normal sperm. Data of testicular biometry were correlated with data for semen variables using the Pearson’s correlation assessment. Effects of testicular variables in selecting for sperm morphology of bulls in the BSE were evaluated by logistic regression. Scrotal circumference, testicular volume, length and width were positively correlated to sperm motility (0.18 to 0.19) and normal sperm (0.24 to 0.27) and negatively correlated with values for major defects (−0.24 to −0.27), but for testicular ratio and eccentricity there were coefficients near zero for all semen traits. Testicular ratio and eccentricity were not suitable for predicting the probability of selecting a bull based on semen variables using the BSE, but scrotal circumference, testicular volume, length and width were highly significant (P < 0.0001) with moderate values of area under ROC (Receiver Operating Characteristics) curve (0.608 to 0.620).

Breeding soundness evaluation (BSE) in boars from Costa Rica

Nerve Growth Factor-β (NGF) is a seminal plasma protein that regulates sperm physiology in bulls, yet its production and association with fertility remain unclear. The objective of this study was to describe NGF distribution in bull accessory sex glands, quantify its seminal plasma concentrations, and determine its association with sire conception rates. Accessory sex glands were collected post-mortem from mature bulls (n = 3). Quantitative PCR and immunohistochemistry were performed in tissue samples. Pre-ejaculate and sperm-rich fraction of seminal plasma from Angus (n = 42) and sperm-rich fraction from Holstein (n = 10) bulls were collected by electroejaculation. Holstein (n = 76) and Jersey (n = 14) bulls were collected by artificial vagina, and those with available sire conception rate scores were allocated to: (1) negative/0 (n = 15); or (2) positive (n = 45). Seminal plasma NGF concentrations were measured using ELISA. Relative abundance of NGF mRNA was greatest in the vesicular, intermediate in ampulla, and lowest in prostate and bulbourethral glands (P ≤ 0.03). The most intense NGF staining was detected in the ampulla and vesicular glands (P < 0.05). Concentrations of NGF were greater in the sperm-rich fraction than in the pre-ejaculate and in samples collected by artificial vagina (P < 0.01). Seminal plasma NGF concentrations were greater in bulls with positive sire conception rate than those with negative/0 (P = 0.05). This study determined that NGF is produced in the ampulla and vesicular glands of bulls and is secreted into the sperm-rich fraction of the ejaculate. The positive association of NGF with bull fertility warrants further investigation.