Age Of Bulls Research Articles

Influence of THI index, age of bulls, year, and season on production and quality of native sperm of Holstein-Friesian bulls

Influence of THI index, age of bulls, year, and season on production and quality of native sperm of Holstein-Friesian bulls

Formation of the biological value of beef protein depending on the age and breed of bulls

Formation of the biological value of beef protein depending on the age and breed of bulls

53 Relationship of Angus yearling bull pulmonary arterial pressure estimates with birth weight, gestation length and growth traits

Abstract Pulmonary arterial pressure (PAP), determines the susceptibility to High Altitude Disease (HAD) of an animal, which causes pulmonary hypertension due to hypoxia. Cattle that reside in elevations greater than 1,500 m are more susceptible to HAD. PAP measures the resistance of blood flow through the lungs and can be used as an indicator of the susceptibility of an animal to HAD. It is estimated that 1.5 million head of cattle are raised in high altitude environments (above 1,500 m) and HAD accounts for 3 to 5% of calf death loss yearly. The objectives of this study were to model the relationship of PAP estimates with birth weight, gestation length and growth traits of developing bulls. PAP estimates were collected from Angus yearling bulls ranging in age from 12 to 18-mo of age from a Montana-based Angus operation (> 1,600 m elevation, 5,400 yearlings/18-mo-old bulls from 2016 – 2023). We hypothesized that the relationship between PAP and performance traits could be described with linear or asymptotic models. We used Akaike’s Information Criterion adjusted for small sample sizes (AICc) to evaluate support for competing models reflecting hypotheses about the effects of bull age at time of testing and performance traits. Models containing an asymptotic relationship between PAP and all measured variables were the best supported from the candidate model sets. Bull age at time of PAP testing was not supported in model selection for any of the performance traits measured. PAP was greater for bulls with greater birth weight (P < 0.01; β = 2.86 ± 0.81; R2marginal = 0.25 %; R2conditional = 0.77 %). PAP was greater for bulls that had greater gestation lengths (P < 0.01; β = 33.74 ± 11.25; R2marginal = 1.40 %; R2conditional = 27.37 %). There were no observed relationships between bull PAP and weaning weight (P = 0.26). PAP was less for bulls that had greater yearling weights (P = 0.04; β = -2.16 ± 1.05; R2marginal = 0.09 %; R2conditional = 0.65 %). In addition, PAP was less for bulls that had greater weaning to yearling gains (P = 0.02; β = -1.21 ± 0.54; R2marginal = 0.12 %; R2conditional = 0.79 %). In summary, PAP was related to birth weight, gestation length, yearling weight, and growth between weaning and yearling; however, these relationships explain very little of the variation of PAP estimates.

Evaluation of Body Measurements of Limousin Young Bulls by Principal Component Analysis

The aim of this study was to analyse how body measurements, live weight and age in young Limousin bulls are interrelated, and what ratio of the phenotype variance can be explained by a group of them, so what traits should be considered in early selection. Body measures of 8-9 months old Limousin young bulls (n=610) in two consecutive years from 32 Hungarian farms were registered, and their covariance structure was studied by principal component analysis. Two components were defined, explaining 71.58% of the total variance. The first component was composed of live weight and body measures; the second component contained age. Live weight, withers’ height and hip height measures had highly definitive effect in the first component. Length of back, width at shoulders, and width at hip bone measurements had lower, but still significant effects. Eigenvalue of the first component had been very high, with 58.36% eigenvalue variance. Only effect of age proved to be highly significant in the second component, with an eigenvalue variance 13.22%. As age contributes less, if correction is needed for transforming results of individuals comparable, then it is advised to be based on live weight. Registered body measurements could be considered together in selection decisions, not needless to take all separately.

Effect of Age on Sexual Behaviour, Scrotal Circumference and Scrotal Surface Temperature in Sahiwal Bulls

Age of the bull influences the sexual behaviour and quality of semen. The present study was conducted to find out the age window at which the bull shows best reproductive performance. Fifteen Sahiwal bulls were selected and classified into three age groups (n=5, in each group) - G1(2- 3.5), G2 (>3.5-8) and G3 (>8-12) years. The sexual behaviour was recorded at the time of semen collection by CCTV camera at 15 days interval. Scrotal circumference (by scrotal tape) and scrotal surface temperature (by IRT) were also taken at monthly interval. The data so obtained in the experiment was subjected to statistical analysis by one-way analysis of variance (ANOVA) using SPSS software version 26.0 to draw scientific interferences. The results revealed that the mean value of scrotal circumference was significantly (p<0.05) low in G1 as compared to the other two groups. No significant difference was observed among the groups for scrotal surface temperature and scrotal temperature gradient. Most of the sexual behaviour parameters were significantly high in the G2 (>3.5-8) group except for the time to enter arena from preparation site and total number of mountings. Therefore, it can be concluded from this study that sexual behaviour is influenced by age and adult (middle) aged bulls performed better as compared to young and old groups.

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

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

Evaluation of Genetic and Non-genetic Factors Influencing Semen Production Potential in Sahiwal Bulls

Background: Understanding genetic and non-genetic factors that influence the quality and quantity of semen production plays a crucial role in determining the reproductive efficiency and genetic progress within the Sahiwal breed. The objective of this study was to assess the impact of genetic and non-genetic factors on the semen production potential of Sahiwal bulls. Methods: Semen ejaculate data, including volume (VOL), sperm concentration per milliliter (CONC), total sperm count per ejaculate (TS), initial motility (INIT) and post-thaw motility (PT), as well as semen quality traits such as hypo-osmotic swelling test (HOST) and acrosome integrity of frozen semen (AIFS), were obtained from 52 Sahiwal bulls. The data spanned from January 2011 to December 2018 and were collected at BAIF’s frozen semen station in Jind, Haryana, India. To ensure data reliability, observations beyond the mean±4 standard deviations (S.D.) were identified as outliers and subsequently excluded from the study. Two key factors, namely the season of semen collection (winter, summer and monsoon) and the age of bulls at collection (categorized into 12-month intervals ranging from less than 36 months to 156 months), were considered influential factors affecting semen characteristics. To investigate the correlation between bulls (genetic + permanent environmental correlation) and semen parameters, a repeatability animal model was employed, treating the bull as a random effect. The statistical analysis was conducted using WOMBAT software. Result: The findings revealed that the season of semen collection had a highly significant effect (P less than 0.01) on VOL, CONC, TS and PT. However, INIT, HOST and AIFS were not influenced (P greater than 0.05) by the season of collection. Furthermore, age at semen collection significantly affected all semen characteristics. VOL and TS exhibited an increasing trend until 72 to 84 months, followed by a decline until 96 to 108 months.

Impact of bull age, sperm processing, and microclimatic conditions on the viability and DNA integrity of cryopreserved bovine sperm.

Context Seasonal microclimatic fluctuations can cause changes in sperm quality even in dairy bulls bred under temperate climate. These changes can vary between sires of different age and affect sperm freezability. Aims We aimed to evaluate the modulating effect of bull age and equilibration time before freezing on the seasonal pattern of sperm viability and DNA integrity post-thaw. Methods In the frame of systematic sperm quality control, we assessed the integrity of sperm plasma membrane and acrosome (PMAI) in 15,496 cryopreserved bovine batches, and the percentage of sperm with high DNA fragmentation index (%DFI) after 0h and 3h incubation at 38°C post-thaw (3h) in 3422 batches. Semen was equilibrated for 24h before freezing if collected on Monday or Wednesday and 72h if produced on Friday. We investigated the effect of season, bull age, equilibration, and temperature-humidity index (THI) on the day of semen collection on sperm traits using mixed-effects linear models. Key results PMAI and %DFI (0h and 3h) deteriorated with increasing THI. The effect of THI on %DFI was detected with a 30-day time lag. Seasonal fluctuations of sperm quality were similar between young, mature, and older sires. Prolonged equilibration did not affect PMAI but was linked to elevated %DFI (3h) in summer. Conclusions Extending equilibration from 24 to 72h is compatible with commercial standards of bovine sperm quality post-thaw; however, it could interfere with the seasonal pattern of the latter. Implications Systematic monitoring of bovine sperm quality enables the prompt detection of stress factors related to microclimate and semen processing.

Evaluation of some reproductive indices of the White Fulani indigenous bulls in Kwara State, Nigeria

This study was designed to evaluate some reproductive indices of the White Fulani Indigenous cattle bulls in Ilorin, Kwara State, Nigeria. Forty apparently healthy bulls of age one to five years were used for this study. The parameters studied included scrotal circumference, scrotal length, chest girth and body weight. These parameters were taken using measuring tapes. The result obtained showed that there was significant (p < 0.05) differences in the scrotal circumference and scrotal length between bulls in the age groups 1, 2 and 3 years old while 4 and 5 years old showed no significant (p > 0.05) difference. There was significant difference (p < 0.05) in the chest girth and body weight of bulls in all the five age groups (1 – 5 years old). This suggests that the age of puberty in the indigenous white Fulani bulls is three years. Veterinarians and farmers can leverage on these reproductive indices (scrotal circumference, scrotal length, chest girth, and body weight) to select bulls with superior breeding potential, ultimately improving herd health and productivity.

Genetic Variability and Conservation Challenges in Lithuanian Dairy Cattle Populations.

The purpose of the study was to investigate the genetic variability of open Lithuanian Red and Red-and-White (LRWP) and Lithuanian Black-and-White (LBWP) dairy cattle populations and indicate the differences from the old genotypes of Lithuanian Black-and-White (LBW) and Lithuanian Red cattle (LR), which are currently under a conservation program. In order to gain a better understanding of the populations under conservation and to minimize the potential influence of other breeds, a distinct subgroup was formed that comprised animals whose father and mother belonged to the same breed (LR_pure and LBW_pure). The genetic variability was estimated using the number of founders, pedigree completeness, number of males and females in reproduction and age distribution, generation interval (GI), inbreeding coefficient (F) and effective population size (Ne). The highest average pedigree completeness values in the second generations of the old genotype LR and LBW were 100%. Higher ages of females in the populations under conservation were related to a higher GI and their longer life expectancy. In 2021, the reproductive age of bulls used for insemination within these populations ranged from 5.1 to 27.8 years. The proportions of males producing offspring in their older age indicate that the semen was used from the national gene bank of commercial artificial insemination companies. The GI (>5) in LR and LBW females was higher than that in LRWP and LBWP. The analysis of the data over the 15-year period showed that the GI of males in LRWP and LBWP decreased equally by 38%, while in LR_pure population, it increased by 80%. A high (9.24%) average inbreeding coefficient (F) was found in inbred animals of LR_pure population, while in LBW_pure, it was 5.35% in 2021. The coefficient of inbreeding varied within the different cattle populations. In the open LR population, it ranged from 1.48% to 2.7%, while in the LRWP population, it fell between 2.12% and 3.72%. The lowest effective population size (Ne) concerning the rate of inbreeding was observed in LBW_pure (23) and LR_pure (59), with the highest Ne identified in the LBWP population (462). When considering Ne based on the number of parents, LR_pure displayed the lowest Ne (42), while the highest Ne was found in LBWP (4449). An analysis of local cattle populations reveals that LR faces the most critical situation. This particular population has been steadily declining for a number of years, necessitating additional measures and efforts to safeguard the LR's ancestral genetic makeup. The results of the LBWP analysis also highlight a concerning trend. Even in very large populations with open breeding programs, the effective population size per generation can experience a significant decrease.

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 23months (22 ± 0.76months, 518 ± 94.17kg), category 2 consisted of animals aged 24 to 35months (30 ± 4.42months, 679 ± 137.19kg), and category 3 consisted of animals ≥ 36months (60 ± 14.12months, 907 ± 161.73kg). 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 13months 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.

PSXIV-13 Evaluation of On-Animal Sensors for Monitoring Diurnal Physical Activity of Beef Bulls During the Breeding Season

Abstract Applications of on-animal sensors (OAS), commonly used to monitor behavioral patterns in livestock, remain largely undeveloped for extensively managed beef bulls. Thus, the objective of this study was to characterize and compare two OAS types for monitoring bull activity during the breeding season. Angus and Angus crossbred beef bulls (n = 50) aged 1 to 8 years, from six cow-calf operations in Ohio were placed into multi-sire breeding groups (n = 19) with a bull-to-female ratio of 1:25 (range 1:16 to 1:31). Bulls were placed with a female group from day 10 (range day 5 to 12) until day 60 after fixed-time artificial insemination. Before turnout, each bull was subjected to a breeding soundness examination and fitted with a collar-mounted GPS and an ear tag-mounted triaxial accelerometer (AX3). Raw GPS and AX3 activity measurements, namely speed (m/s) and motion intensity (g), were converted to standardized Z-scores and summarized to an hourly resolution by computing the median hourly activity over a 24-hour cycle at early (day 13 to 28) and late (day 34 to 49) stages of the breeding season. Linear mixed models were fitted to standardized activity measurements (expressed in log scale) to assess the dynamic effect of OAS type throughout the day at early and late stages of the breeding season. Size of the breeding group (males and females), bull age, scrotal circumference, and body condition score were evaluated as potential explanatory covariates using stepwise selection. Diurnal activity curves followed a pattern of relative inactivity overnight from hours 21 to 5 and relative activity during daylight from hours 6 to 20. For both OAS, mean activity early in the breeding season was ~47% greater (P < 0.01) than late. At both breeding season stages, mean activity of bulls differed between OAS types (P < 0.01) at hours 2, 3, 4, 5, and 6 by at least 38%, with greater activity from GPS than AX3 (P < 0.05 in all cases). Conversely, at hours 13, 14, and 16, activity derived from AX3 was greater than from GPS by at least 2.5-fold (14: P < 0.01; 13 and 16: P < 0.1). There was no evidence (P > 0.1) for differences between bull activity derived from GPS or AX3 during the remaining overnight (21-1) and daytime (7 to 12, 15, and 17 to 20) hours. In conclusion, this study provides evidence that simultaneous assessment of bull activity using independent OAS, differed between technologies throughout a 24-h day. Additionally, over the course of the breeding season, both OAS indicated a decline in activity. Bull breeding activities are expected to be less frequent as the breeding season progresses; thus, these may explain the observed differences between stages of the breeding season. Further exploration of benchmarks for bull activity may yield useful tools for the identification of health and reproductive-related behaviors.

Effect of age, season and sire on semen quality traits in Frieswal breeding bulls

The present study was undertaken to assess the effect of season of semen collection, age and sire on semen quality of Frieswal breeding bulls. The data on 8113 semen ejaculates of 155 bulls born to 34 Frieswal sires were utilized for the study. The effect of age of bulls on semen volume, sperm concentration (million) per ml and sperm motility (%) in fresh semen (directly after collection) was highly significant. Additionally, it was discovered that the sire effect of bulls on different semen quality parameters and the influence of season on sperm concentration and motility both were statistically significant. Heritability estimates of different semen quality traits studied were moderately high and exceptionally significant. For semen volume, the estimate was found to be 0.336±0.078 while for concentration and pre freezing sperm motility values were 0.296±0.068 and 0.407±0.089, respectively. From the results, it may be concluded that the age and sire of bulls significantly affected the semen volume, sperm concentration and sperm motility in Frieswal bulls. The season of semen collection caused significant variations in sperm concentration and motility but not the semen volume. The semen volume and concentration were superior in ejaculates collected during winter season while the summer season was conducive for increased sperm initial motility. The Frieswal bulls up to 4-5 years are able to produce semen of better quality. The moderately high heritability estimates of semen quality traits provide indication for genetic improvement of the traits through selection.

Estimation of genetic parameters for semen traits in Egyptian buffalo bulls

This study was conducted to characterize semen traits (ejaculate volume (VOL), mass motility (MM), sperm livability (LS), percentage of abnormal sperms (AS), and sperm concentration (CONC)) of Egyptian buffalo bulls and evaluate the importance of some nongenetic factors (year (YC) and season (SC) of semen collection and age of bull genetically and environmentally at collection (ABC)) affecting the investigated traits. A total of 7761 normal semen ejaculates were collected from 26 bulls from 2009 to 2019. Single-trait and bivariate repeatability animal models using Bayesian methods were used to estimate variance components, heritability, repeatability, and genetic correlations among the investigated semen traits. YC and ABC exerted significant effects on most semen traits, whereas SC exerted no significant effect on all the investigated semen traits. Heritability estimates were 0.08, 0.52, 0.51, 0.04, and 0.49 for VOL, MM, LS, AS, and CONC, respectively. Repeatability estimates were 0.14, 0.82, 0.79, 0.06, and 0.78 for VOL, MM, LS, AS, and CONC, respectively. The genetic correlations between MM and each of LS and CONC were highly significant (0.99 ± 0.01 and 0.95 ± 0.14, respectively), and that between LS and CONC was also highly significant (0.92 ± 0.20). The high heritability estimates for MM, LS, and CONC combined with the favorable high significant genetic correlations between these traits indicated that direct selection for MM may be an effective method to enhance semen quality in Egyptian buffalo bulls and consequently improve fertility.

THE RESULTS OF WORK PROJECT TCP/RER/3604 “CONSERVATION AND DEVELOPMENT OF DUAL-PURPOSE CATTLE BREEDS IN EASTERN EUROPE”

THE RESULTS OF WORK PROJECT TCP/RER/3604 “CONSERVATION AND DEVELOPMENT OF DUAL-PURPOSE CATTLE BREEDS IN EASTERN EUROPE”

Semen quality of progeny-tested breeding bulls maintained at the National Artificial Insemination Centre, Arusha, Tanzania

The success or failure of artificial insemination (AI) depends on the quality of semen used. This study was conducted to investigate the effect of breed, age, collection period, and ejaculate number on semen quality collected from 15 breeding bulls available at the centre with different ages (4 Friesian, 4 Ayrshire, 3 Jersey, 2 Simmental and 2 Boran breeds) maintained at National Artificial Insemination Center (NAIC), Arusha, Tanzania. A total of 600 ejaculates were collected for four weeks per month consecutively from January to May 2022, weekly per bull and twice a day; morning (6.00 - 9.00 AM) and evening (3.00 - 6.00 PM) sessions). The ejaculates were first examined visually for volume, color, foreign bodies, and consistency whereas sperm concentration (SPC), progressive motility (PM) and total motility (TM) were assessed using Computer Assisted Semen Analysis System (CASA). Viability/vitality (SPVI) and morphology (SPNR) of sperms were analyzed microscopically after staining with Eosin-Nigrosin. Data were subjected to SAS program and results showed that ejaculate volume, progressive motility, total motility, sperm viability, and morphology were significantly (P<0.05) affected by age and collection period. Simmental, Friesian, and Ayrshire bulls produced more voluminous semen than Jersey and Boran bulls. Jersey bulls had higher (P<0.05) sperm concentrations and live spermatozoa as compared to other bulls. Boran and Jersey's bulls exhibited higher PM and TM than the other bulls. The period of semen collection (morning versus evening) negatively affected semen volume, total motility, and semen viability in which morning harvests performed better than evening collections. Middle aged bulls (3-5 years) produced semen of higher quality compared to other groups (< 3 years and > 5 years old bulls). In conclusion, age, breed, period of semen production and ejaculate number revealed significant effect on bovine semen characteristics.

BullVal$: An Integrated Decision-Support Tool for Predicting the Net Present Value of a Dairy Bull Based on Genetic Merit, Semen Production Potential, and Demographic Factors.

Deciding when to replace dairy bulls presents a complex challenge for artificial insemination (AI) companies. These decisions encompass multiple factors, including a bull's age, predicted semen production, and estimated genetic merit. This study's purpose was to provide a practical, objective tool to assist in these decisions. We utilized a Markov Chain model to calculate the economic valuation of dairy bulls, incorporating key factors such as housing costs, collection and marketing expenses, and the bull's probable tenure in the herd. Data from a leading AI company were used to establish baseline values. The model further compared a bull's net present value to that of a potential young replacement, establishing a relative valuation (BullVal$). The range of BullVal$ observed spanned from -USD 316,748 to USD 497,710. Interestingly, the model recommended culling for 49% of the bulls based on negative BullVal$. It was found that a bull's net present value was primarily influenced by market allocation and pricing, coupled with the interaction of semen production and genetic merit. This study offers a robust, data-driven model to guide bull replacement decisions in AI companies. Key determinants of a bull's valuation included market dynamics, semen production rates, and genetic merit.

DNA-based Paternity Analysis in Multi-bull Breeding Programs on Beef Cattle Operations in Western Canada

A 3-yr study was conducted to evaluate deoxyribonucleic acid (DNA)-based paternity analysis on commercial beef ranches managing multi-bull breeding systems. Five commercial ranches in central Saskatchewan Canada participated in the study with a total of 22 breeding groups. All bulls (n = 75) and calves (n = 2243) were sampled to determine parentage. Number of calves sired per bull ranged from 1 to 87 (23 ± 15.9). The value of a calculated index of bull prolificacy (BPI) ranged from 0.05 to 3.83. Older bulls had a BPI averaging 1.10, 2-yr old bulls 1.00, and yearling bulls 0.76 (p > 0.05). Strong positive (r = 0.93, n = 74, p = 0.01) correlation was observed between total calves born per bull and calves born in the first 21 days BPI, between total calves born per bull and calves born in week-3 BPI (r = 0.69, n = 74, p = 0.01). Bull age was shown to play a significant role when determining prolificacy, with older bulls siring more calves than younger bulls. Bull number per breeding group influenced the number of calves sired. As number of bulls per breeding group increased so did the variation in the number of calves sired by each bull. Conducting DNA parentage testing only on calves born in the first 21 d or in week 3 of the calving season may provide an opportunity to decrease costs and turn-around time for laboratory results and decisions made, prior to the next breeding season.

Novel interpretation of sperm stress test and morphology for maturity assessment of young Norwegian Red bulls

The use of genomic selection significantly reduces the age of dairy bulls entering semen production compared to progeny testing. The study aimed to identify early indicators that could be used for screening bulls during their performance testing period and could give us insight into their future semen production performance, acceptance for the AI station, and prediction of their future fertility. The study population consisted of 142 young Norwegian Red bulls enrolled at the performance test station, followed until we received semen production data, semen doses, and, subsequently, non-return rates (NR56) from the AI station. A range of semen quality parameters were measured with computer-assisted sperm analysis and flow cytometry from ejaculates collected from 65 bulls (9–13 months). The population morphometry of normal spermatozoa was examined, showing that Norwegian Red bulls at 10 months of age have homogenous sperm morphometry. Norwegian Red bulls could be separated into 3 clusters according to their sperm's reaction patterns to stress test and cryopreservation. Results of semi-automated morphology assessment of young Norwegian Red bulls showed that 42% of bulls rejected for the AI station and 18% of bulls accepted had ejaculates with abnormal morphology scores. For the youngest age group at 10 months, the mean (SD) proportion of spermatozoa with normal morphology was 77.5% (10.6). Using novel interpretation of sperm stress test combined with sperm morphology analysis and consecutive cryopreservation at a young age allowed identification of the candidate's sperm quality status. This could help breeding companies introduce young bulls earlier to the AI stations.

Semen quality analysis of the Airshire bulls in relation to the AH1 fertility haplotype

The results of the studies (2019-2021) of increased incidence of genetic mutations, such as fertility haplotypes, in the population that result in lower reproductive rates in dairy cattle are presented. Semen quality of the Ayrshire breed bulls was evaluated for motility and morphological indices due to rs475678587 in the UBE3B gene locus associated with the AH1 fertility haplotype. Semen samples (n = 14) were obtained from the Center of Collective Use "Genetic Semen Collection of Domestic and Foreign Cattle Breeds" of the All-Russian Research Institute of Farm Animal Genetics and Breeding (ARRIFAGB) and belonged to the animals born in 2014 and older (average age of bulls was 6-15 years). Genotyping for rs475678587 of the UBE3B gene was performed by Sanger sequencing. Animals with the heterozygous CT genotype were defined as carriers of the AH1 haplotype (AH1-C), and those with the homozygous CC genotype were defined as free of the AH1 haplotype (AH1-F). Frozen-thawed semen was evaluated according to the following parameters: total and progressive motility, percentage of normal spermatozoa. Morphological indices of sperm quality were assessed after differential staining of cellular elements of spermatozoa using a commercial kit "Diakhim-Diff Quick" (ABRIS+ scientific and production company) in sperm smears. The following indicators were taken into account: acrosomal abnormalities, abnormalities in the head, tail, and neck of the spermatozoon. Data on the indicators of native semen (motility, concentration), obtained immediately after collection, were received from the archive of the technical service of the breeding enterprise. The results of the studies have shown that according to physiological and morphological indices the semen obtained from the bulls carrying the haplotype AN1 did not differ significantly from those of the bulls free of the mutation. In terms of total motility, the semen of the haplotype fertility carrier bulls was almost 2% higher than that of the haplotype free bulls. It can be noted that the haplotype carriers of fertility bulls were generally characterized by good sperm fertility indices.