Breeding Bulls Research Articles

Impact of Implementing Female Genomic Selection and the Use of Sex-Selected Semen Technology on Genetic Gain in a Dairy Herd in New Zealand

Genomic selection (GS) has changed cattle breeding, but its use so far has been in selecting superior bulls for breeding. However, its farm-level impact, particularly on female selection, remains less explored. This study aimed to investigate the impact of implementing GS to identify superior cows and using artificial mating of those cows with sex-selected semen in a New Zealand Holstein-Friesian (HF) dairy herd (n = 1800 cows). Heifers (n = 2061) born over four consecutive years between 2021 and 2024 were genotyped and their genomic breeding values (GBVs) were estimated. These heifers were ranked based on the Balanced Performance Index (BPI; DataGene, Dairy Australia) Lower-performing cows producing less than 15 L/day (or 20 L/day for older cows) and those with severe mastitis were culled. Cows were mated with HF genetics based on production and udder breeding values, while lower-performing cows were mated to beef genetics. Milking adult cows were mated to bulls with similar BPI value. Annual genetic change was measured using Australian breeding values (ABVg) for milk fat production (FAT), protein production (PROT), fertility (FER), Mastitis Resistance (MAS), and BPI. The genetic merits of the heifers improved annually, with BPI increasing from 136 to 184 between 2021 and 2023, corresponding to a financial gain of NZD 17.53 per animal per year. The predicted BPI gain from 2023 to 2026 is expected to rise from 184 to 384, resulting in a financial gain of NZD 72.96 per animal per year. Using sex-selected semen on the top 50% of BPI-rated heifers in 2024 further accelerated genetic gain. Predicted BPI values for progeny born in 2025 and 2026 are 320 and 384, respectively. These findings revealed that the female GS, combined with sex-selected semen from genomically selected bulls, significantly accelerates genetic gain by improving the intensity and accuracy of selection. The approach achieves genetic progress equivalent to what traditionally would have required eight years of breeding without female GS, and has potential to improve dairy herd performance and profitability.

Effect of age-associated oxidative stress on sperm viability, acrosomal integrity and sperm apoptosis and DNA fragmentation in Sahiwal breeding bulls.

Sperm motility is the prime functional attribute for semen quality and fertility of the bull. However, the bull's age directly affects the semen quality, and the bull's fertility and productive life decline with age. Even though research on age has been conducted in the past, it is still unclear how old a bull should be maintained at artificial insemination centers. The minimum standard protocol (MSP) states that a bull has an 8-years productive lifespan, yet it has been shown that some bulls older than 8 years have produced freezable ejaculates. It has yet to be established what the bull's ideal productive life is under the tropical climate of India without affecting in-vitro sperm functions. For the validation of the maximum age of a bull up to that it could be utilized in the artificial insemination centers, cut-off values of oxidative stress in freezable semen ejaculates were used. The current study was done at the Artificial Breeding Research Centre, ICAR-NDRI, Karnal, Haryana, India. A total of eighteen Sahiwal breeding bulls were divided into three groups: Young (2-4 years), Adult (> 4-8 years), and Older (> 8-11 years). Three ejaculates were taken from each bull; thus, a total of 18 ejaculates were utilized in each group for semen examination. Semen quality of Young bulls was poor compared with adult and older bulls. Seminal parameters such as dead, moribund, apoptotic, reacted acrosome, and protamine deficient sperms were higher in older bulls than in adult bulls; however, the values were non-significant. Less difference was found in the semen parameters among adult and older bulls. This indicates that the semen quality of older Sahiwal bulls was optimum, freezable, and can be utilized for up to 11 years (Average 9.5 years).

Heritability Estimates of Age at First Calving and Correlation Analysis in Angus Cows Bred in Hungary.

This study aimed to examine the age at first calving (AFC) in Hungarian Angus herds. This study was conducted on the basis of data from 2955 registered cows, classified into five groups (based on different Angus types), and 200 breeding bulls, which were the sires of the cows. The data were made available by the Hungarian Hereford, Angus, and Galloway Breeders' Association. The variance and covariance components, heritability, breeding value (BV), and genetic trends of AFC between 1998 and 2021 were evaluated. A general linear model (univariate analysis of variance) was used to examine the various effects, while best linear unbiased prediction was used to estimate the population genetic parameters and BV, and linear regression analysis was used for the trend analysis. The average AFC obtained was 28.1 ± 0.1 months (SD = 5.3 months), showing a relatively large variance (CV = 18.9%). The environmental factors that influenced the development of the phenotype were the cow's birth season (28.99%, p < 0.01), cow's birth year (28.7%, p < 0.01), the cow's sire (18.32%, p < 0.01), and the herd (11.77, p < 0.05). The cow's color variant (8.10%, p > 0.05) was not significant and did not influence the AFC in this study. The direct heritability of AFC (h2 = 0.51 ± 0.06) was higher than data in the literature (0.38 ± 0.05); however, the maternal heritability was low (h2m = 0.00 ± 0.03). The correlation between direct and maternal genetic effects was zero (rdm = -0.97 ± 1.00). The phenotypic trend of AFC increased by +0.03 months per year, which was not statistically significant. The genetic trend calculation showed no significant changes. Based on the h2 and BV results, it seems that selecting a suitable sire can effectively reduce the AFC of daughters. Since AFC is also an important trait in economic terms, it would be appropriate to include AFC BV in the bull catalog.

171 Association between Angus bulls breeding soundness exam classification and expected progeny differences

171 Association between Angus bulls breeding soundness exam classification and expected progeny differences

Sire mating advice framework for cattle to recommend which beef bull to mate to individual dairy females.

A decision support tool or system is a computerized information system used to support decision-making in a business; one central component to profitable dairy cattle production systems is the appropriate mating of bulls and females. While tools have been described to aid mating decisions between dairy bulls and dairy females, or between beef bulls and beef females, there is a void of such tools that recommend which beef bull to mate to individual dairy females. The objective of the present study was to develop and validate a framework, founded on linear programming, to aid herd-level mating decisions where the bull-female mating is tailored based on complementarity and compatibility of both mates; consideration in the process was given to the genetic merit of both mates for a series of traits as well as the life history of the female herself. Traits considered in the linear function to be maximized in the linear programming procedure were those related to calving performance traits (i.e., calving dystocia, perinatal mortality and gestation length) and subsequent beef performance (i.e., docility, feed intake, and carcass merit); each trait was weighted in the linear function by its respective economic importance. First, a calibration and validation data set from a national database were generated using data truncated on calendar year to validate predictions of progeny performance. Expected performance of progeny was based on a combination of estimated genetic merit and non-genetic effects which would be available at the time of mating. The direction of the associations in the validation population was in line with expectations and, in many instances, the extent of the association was close to expectation. Using real dairy cow data of 284,334 cows from 1,535 herds, 6 randomly chosen candidate beef bulls of multiple breeds were selected per herd for mating assignments to all cows, each with an equal number of matings. Bull-cow matings were assigned either at random or using the developed linear programming framework. While the mean expected genetic merit of the hypothetical progeny was the same for both scenarios (as expected), the bull-cow assignments proposed by the linear programming mating framework were assortative in nature. Bulls with a greater genetic risk of dystocia in their progeny were, on average, recommended for mating to cows that, genetically, were less likely to experience calving dystocia based on their direct and maternal estimates of genetic merit. Similarly, where possible, bulls that genetically were expected to produce, on average, heavy and more conformed carcass progeny were mated to cows whose progeny were expected to have lighter and less conformed carcasses based on the genetic merit inherited from the cow. A case study of one large dairy herd illustrating in more detail how the linear programming-based mating algorithm operates is also presented especially in relation to assortative mating for calving dystocia and carcass merit. The validated linear programming-based mating decision support tool presented in this study describes a digital framework for aiding decision making in beef-on-dairy herd breeding programs.

The impact of bull breeding management on reproductive function (review)

Providing the population with quality food products is currently relevant. High-tech production of meat and dairy products requires breeding animals with high genetic potential. The main role is given to bull sires, since they are responsible for the constant reproduction of the breeding stock, which depends on the non-stop renovation of the herd with high breeding value’s calves. Management of growing and breeding of young bulls can directly affect the reproductive function of sires and the physiological health. The article provides analytical data based on literary sources containing research by various authors on this topic, and reviews methods and technologies for keeping breeding bulls on various farms in the Russia and abroad. Currently, there is a many problems of getting high-quality breeding young bulls to an artificial insemination center. Currently, there are problems with obtaining high-quality breeding bulls of the enterprise. There are animals with abnormal development of the musculoskeletal system, joints, hooves, with signs of osteomalacia, etc. Such animals require additional costs for veterinary and breeding services. The quality of the sperm products they produce often does not comply with state normative. The reason is related either to the choice of maintenance technology or feeding technology. It is necessary to competently organize management, breeding and veterinary work in farms that are purposefully engaged in breeding young animals.

Endogenous Tissue Inhibitor of Metalloproteinase-2 Levels Are Associated With High-Quality Neat Semen but Unrelated to Sperm Cryoresistance in Bulls.

Tissue Inhibitor of Metalloproteinase-2 (TIMP-2) is part of the tissue inhibitors of the metalloproteinases (TIMPs) family. Its primary function is to regulate the activity of matrix metalloproteinases (MMPs) across various tissues, including those of the reproductive system. This study aimed to quantify the natural levels of TIMP-2 in seminal plasma (SP) and sperm membrane (SM) of bulls, explore potential associations between TIMP-2 levels and semen quality parameters, and examine the relationship between TIMP-2 levels and sperm cryoresistance in bulls. Thirty semen samples from Frieswal breeding bulls were categorized into two groups based on their initial progressive motility (IPM): Good (IPM ≥ 70%; n = 21) and Poor (IPM ≤ 40%; n = 9). The samples were evaluated for their quality parameters at the fresh stage, and TIMP-2 levels were measured in SP and SM using a bovine-specific ELISA kit. Following cryopreservation of Good samples (n = 21), post-thaw motility (PTM) was used to further classify samples into Freezeable (PTM ≥ 50%; n = 14) and Non-Freezable (PTM < 50%; n = 7) groups. In frozen-thawed samples, sperm attributes, kinetics, and functional parameters were assessed, and the results were correlated with retrospective TIMP-2 levels of SP/SM. Our study revealed that the quantified levels of TIMP-2 ranged from 100.27 to 535.95 ng/L in SP and from 0 to 115.78 ng/10 million spermatozoa in SM. TIMP-2 levels in both SP and SM were significantly higher in Good ejaculates compared to Poor ejaculates (p < 0.01). Furthermore, total TIMP-2 levels in the SP/SM of semen samples from bulls showed a positive correlation with fresh semen attributes. However, SP/SM TIMP-2 levels in the Freezeable group did not show any significant differences compared to the Non-Freezable group in post-thaw semen quality attributes, kinetic parameters, and functional tests, except for a significant positive correlation (r = 0.530, p < 0.05) between sperm DNA integrity and SP-TIMP-2 levels. In conclusion, the findings suggested that TIMP-2 can be a positive regulator of semen quality at the neat stage. However, when it comes to the resilience of sperm to cryopreservation, the levels of TIMP-2 do not seem to exert any significant influence in breeding bulls.

Production and Evaluation of Frozen Semen of Sahiwal Bull Using Two Different Diluters and Protocols

The experiment was designed to evaluate the effects of diluters and freezing protocols on frozen semen production of Sahiwal breeding bulls. Imported 100% Sahiwal breeding bulls were then reared in the American dairy limited (ADL). Semen samples are processed and frozen once a week in the ADL. Spermatozoa with various motility patterns were collected; these included post-thawing, progressive, fast, slow, circular, and local. Computer Assisted Semen Analyzer (CASA) was used to measure the straight-line velocity (VSL), curvilinear velocity (VCL) and linearity (LIN) parameters. Two diluters (tris egg-yolk and tris egg-yolk aqua) and freezing protocols (slow freezing and fast freezing) were used for frozen semen production of these bulls. The significantly highest (P&lt;0.05) number of post-thawing total, progressive and progressive fast motility (78.42±1.88, 73.50±1.90 and 59.68±2.10%), VCL (115.31±3.82µm/s) and lowest slow, circular and local motility (13.44±1.40, 0.57±0.08 and 4.92±0.41%), LIN (0.39±0.01%) was found in diluter 1 and freezing protocol 2. On the other hand, highest number of circular motility (0.77±0.18%) and VSL (44.83±1.17µm/s) was found in diluter 1 and freezing protocol 1 whereas highest number of slow and local motility (18.84±1.23 and 7.46±0.57%) and LIN (0.61±0.20%) and lowest progressive fast motility (48.73±2.28%), VCL (98.90±3.42µm/s), VSL (39.76±1.33µm/s) was found in diluter 2 freezing protocol 2 and also lowest post-thawing and progressive motility (73.44±1.94 and 66.51±2.02%) was observed in diluter 2 freezing protocol 1. The study reveals that diluter 1(one step egg yolk based) and freezing protocol 1 (5 steps) and 2 (2 steps) seems to be an efficient method for frozen semen production.

Experience of preputiotomy performing in bull with acroposthitis and fibrous affect of penis’ S-shaped curve

The aim of this study was to perform a preputiotomy with the formation of an artificial opening in a breeding bull to realize his reproductive potential. Scientific and production research was conducted in the spring of 2024. In a 3.5-year-old Holstein breeding bull, kept at a breeding station for keeping breeding bulls, acroposthitis and fibrous lesion of the penis in the area of the S-shaped bend were detected due to the developed infectious process caused by Pseudomonas aeruginosa. The resulting pathology prevented the penis from fully extending beyond the preputial sac when collecting sperm for an artificial vagina (the last sperm collection was performed on 02/07/2024). The operation performed consisted of the following stages: insertion of a thick-walled tube into the preputial sac for better orientation in the tissues; making a V-shaped incision of all layers of the prepuce near its fornix; excision of the prepuce section necessary for free removal of the penis when collecting sperm; formation of an artificial opening by connecting the parietal preputial layer to the skin with an interrupted suture. The postoperative period included daily monitoring of the animal's condition, antibiotic therapy (amoxicillin (0.15 g), three injections every 48 hours), and the use of non-steroidal anti-inflammatory drugs (meloxicam (0.002 g), 3 days). A month after the operation, sperm was collected (06.05.2024, three months later) and the presence of all unconditioned reflexes was noted. At the same time, the copulatory reflex was full, painless and ended in ejaculation. The obtained volume of sperm after two mountings was 2.5 ml, the concentration was 1.3x108, the activity was 8 points. Thus, preputiotomy is an effective method for surgical correction of lesions of the preputial sac and adhesions in the area of the S-shaped bend of the penis in breeding bulls.

Efectiveness of growing simmental breed cares with diferent maintenance technologies.

The purpose of the work was to establish the features of meat productivity of Simmental breed bulls depending on the rearing technology: 1 - traditional technology used on farms (indoors); 2 - using feeding and final fattening. The rearing technology had a significant impact on the live weight of bull calves and the amount of gain at different age periods. The difference in live weight between groups I and II was: at 6 months – 11.2 kg (P &gt; 0.99); at 14 months – 20.3 kg (P &gt; 0.999); at 18 months – 43.9 kg (P &gt; 0.999) in favor of bulls of the second experimental group. On average, by the age of one and a half years, bulls of group II were 43.9 kg heavier than their peers of group I. At 18 months of age, the digestibility coefficients in both groups were high, but in young animals of group II, the coefficients of fiber digestibility were 18.2 % and fat 17.9 % higher than in group I bulls. The best slaughter qualities were in bulls reared using fattening and final fattening. The bulls of group II compared to group I had heavier carcasses: at the age of 6 months by 7.4 kg, at 14 months by 14.5 kg, and at 18 months by 37.0 kg. The deposition of internal fat was relatively small and somewhat greater in bulls of group II. At the age of 14 months, the carcass weight of group II bulls was greater than group I by 6.74 %, and the pulp by 1.34 %. This difference persisted at 18 months. The type of feeding had a significant impact on bone strength. The load that caused bone fractures in volume-fed bulls averaged 1,477 kg, and with concentrated feeding, an average of 1,209 kg, or 18 % less.

Opportunities and challenges of a community-based bull breeding programme: a case of the regional pastoral livelihood resilience project in Uganda

The Regional Pastoral Livelihood Resilience Project Community-Based Breeding Programme (CBBP) was designed with the objective of increasing production and productivity of local Zebu cattle by introducing Sahiwal bulls among sedentary and agro-pastoral livestock farmers. This study mapped out actors, their roles and level of influence in the CBBP as well as the opportunities and challenges encountered during its implementation using the Process Net-Map tool. The results revealed that there were differences in number and type of influential actors between sedentary and agro-pastoral livestock farmers. The bull host and subcounty veterinary officer were the most influential actors among the sedentary livestock farmers whereas it was the herdsman, bull host, and Community Animal Health Workers (CAHWs) among the agro-pastoral farmers. The CBBP was associated with benefits such as increased market value for cattle, reduced chances for cattle rustling, increased cattle productivity in terms of milk and beef production volumes and ease of access to veterinary services. In contrast, the challenges encountered were related to both governance (limited availability of veterinarians, cattle rustling, exclusion of farmers in the planning phase of the CBBP, political interference and failure of collective action) and bull management (high costs of keeping and maintaining the bulls in terms of feeding, housing, watering and veterinary care, heavy bulls injuring or breaking the small cows, sexually transmitted reproductive diseases among others). Lastly, this paper recommends adoption of a combination of well-organized and facilitated Artificial Insemination (AI) programmes alongside the improved bull service scheme as each has capacity to address the challenges of another.

Assessing bull breeding soundness exam parameters following vaccination with modified-live or killed vaccine

Breeding bulls are often placed on a similar herd health plan and vaccinated for the same pathogens as the mature cow herd. The timing of the yearly vaccination is impacted by labor and time constraints with some bulls receiving vaccinations at the time of annual, complete breeding soundness exams or at the time of turnout prior to the breeding season. However, the potential impact of vaccination on spermatogenesis, if any, is unknown. Therefore, the study objective was to determine the impacts on normal sperm morphology through a complete spermatogenic cycle after vaccination of mature beef bulls against bovine herpesvirus 1 and bovine viral diarrhea virus using commercially available modified-live virus (MLV) or killed virus (KV) vaccine. Semen was collected from Bos taurus bulls (n = 11),which were randomly assigned prior to the first breeding soundness exam to vaccine treatment groups: 1) modified-live virus (MLVa); or 2) inactivated/killed virus (KVb). Breeding soundness exams were completed at days -7, 0, 5, 7, 17, 28, 61 following vaccination. No differences were found between vaccine treatment groups MLV and KV (P = 0.46) on the percentage of normal sperm over time (d = -7 through d = 61) as evaluated by two boarded theriogenologists. In conclusion, we found no detrimental effect of the administration of multivalent MLV or KV vaccines on percentage of normal sperm morphology of mature bulls over a 61 – day period.

Взаимосвязь геномного и расчетного инбридинга в популяции крупного рогатого скота голштинской породы Свердловской области

Abstract. The purpose of this paper is to study the inbreeding change of Holstein cattle in Sverdlovsk region and to show the correlation between genomic and estimated inbreeding. Methods. The study was conducted in six farms of the Sverdlovsk region and included 512 cows and heifers with date of birth from 2007 to 2022 and 12 breeding bulls. Chips GGP Bovine 150K (Neogen, USA) and Bovine 50K (Illumina, USA) were used for genotyping. Genome inbreeding estimates F were conducted with --het function in PLINK v1.9. Homozygosity inbreeding coefficient FROH was calculated with “sliding window” package of detectRUNS; FPED was taken from SELEX database, where it was calculated by pedigrees with Wright-Kislovsky formula. Scientific novelty. The comparison of genomic inbreeding for different age groups and estimation of correlations with pedigree inbreeding was conducted in Sverdlovsk region for the first time. Results. Our studies show that inbreeding coefficients increase radically from younger to older age groups. Holstein breed bulls show the highest value of inbreeding. At the same time heterozygosity level, estimated with sMLH tends to decrease with age. In addition, a strong correlation between estimated by pedegree inbreeding FPED and date of birth, as well as weak correlations between FPED and genomic coefficients (which have strong correlations with each other) were established.

Dry-aged beef quality with the addition of Mucor flavus – Sensory, chemosensory and fatty acid analysis

Dry-aged beef is a premium product known for its unique taste and aroma. These characteristics are thought to partially depend on the composition of the microorganisms present on the meat surface during ageing. Recently several attempts to standardise this process were made. This study aimed to assess the effect of a fungal biostarter application on the profile of volatile compounds, fatty acid composition and sensory quality of dry-aged beef. The Longissimus muscle used in the experiment originated from 20 crossbred (10 heifers and 10 steers) animals from the crossing of Holstein-Friesian cows with beef breed bulls. A fungal biostarter composed of Mucor flavus strain KKP2092p was used for meat inoculation. Half of the material was aged without the use of a biostarter (Control samples). The dry-ageing of the meat was performed at a temperature of 1.5 °C with approximately 80–90 % relative humidity for 28 days. The use of Mucor flavus KKP2092p improved meat quality attributes (aroma liking, flavour and overall liking) as a result of the formation of specific volatile compounds. The profile of volatile compounds in the meat aged with Mucor flavus and control variants was differentiated. This study also indicated that Mucor flavus biostarter had an impact on the specific fatty acid composition. An insignificant effect of Mucor flavus on lipid oxidation expressed as mg/kg of malonaldehyde was also observed.

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

205 An autosomal recessive mutation in PYGM causes myophosphorylase deficiency in composite cattle

Abstract Between 2020 and 2022, eight calves (6 heifers, 2 bulls) in a Nebraska herd (composite Simmental, Red Angus, Gelbvieh) experienced exercise intolerance during extended physical activity. These calves exhibited an inability to keep pace with the rest of the herd, with some eventually succumbing to physical collapse from which they did not recover. Increased creatine kinase, an indication of muscle degeneration, was confirmed in biopsy and necropsy samples. Available sire pedigrees revealed a common paternal ancestor within 2 to 4 generations in all the affected calves. Dam pedigrees were unavailable; however, the herd retained replacement females that occasionally shared common ancestors with breeding bulls. Thus, a de novo autosomal recessive mutation was hypothesized as the cause of exercise intolerance in these calves. Genomic data (100K SNP) from 6 affected calves and 715 herd mates were initially used for a whole genome-wide association study, pinpointing a significant region on chromosome 29. Whole-genome sequencing of 2 affected calves combined with 145 other sequenced cattle led to the identification of a nonsense mutation in the PYGM gene, also located on chromosome 29. The mutation, confirmed to be present in the skeletal muscle transcriptome, was predicted to produce a premature stop codon. The protein product of PYGM, myophosphorylase, has a crucial role in metabolizing glycogen stored within skeletal muscle to generate energy for muscle cells. As a result, the recessive genotype led to greater (P &amp;lt; 0.05) glycogen concentrations in affected calves (n = 2) compared with heterozygous animals (n = 3) and wild-type controls (n = 2). Immunohistochemistry and label-free quantitative proteomics analysis confirmed the absence of the PYGM protein product in skeletal muscle. Myophosphorylase is needed for efficient glycogen utilization, which is crucial for producing high-quality beef. In the 2 affected calves harvested, increased skeletal muscle glycogen persisted postmortem, resulting in increased pH and dark-cutting beef, which is associated with a negative consumer perception and economic losses to the industry. In addition to identifying the cause of exercise intolerance and welfare concerns in these cattle, this study is among the first to identify a specific genetic mutation associated with dark-cutting beef. Carriers of the mutation did not display any discernible differences in meat quality or measures of animal well-being. While cattle heterozygous for the mutation may not immediately impact the beef industry, identifying carriers is paramount for implementing proactive selection and breeding strategies to prevent the production of affected calves.

326 Relationship between activity and social interactions of beef bulls during the pre-breeding period and siring capacity in multi-sire breeding groups

Abstract It is currently unknown whether the behavior of bulls during pre-breeding is related to their siring capacity. This information could help producers anticipate the reproductive potential of their bulls and include it in their decision-making. This study aimed to investigate the relationship between the activity and characteristics of social interaction of beef bulls expressed in drylot pens during the pre-breeding period and their siring capacity. Collars with 3-axis accelerometers and proximity sensors were placed on bulls for 12 d prior to breeding season in 2020 (n = 11 bulls) and in 2021 (n = 10 bulls). Bulls were satisfactory at the breeding soundness evaluation, and ages ranged from 1.5 to 5.4 yr. Afterward, bulls were exposed to cows in multi-sire groups at a 1:30 ratio for 2 mo, however, some bulls were removed early due to injuries (range = 15 to 62 d). DNA samples were collected from bulls and calves to calculate the number of calves sired per bull (SRC), adjusted to days exposed to cows. Daily proportion of time active (AC) was measured through a machine learning algorithm created in Python for beef bulls to differentiate activity vs. non-activity from accelerometer data every 20 sec (Precision = 95%). Daily non-directional social networks were created from proximity perceived by the sensors (Precision = 91%, &amp;lt;3m) in Python, where nodes represented bulls and a connection represented one second in proximity. Eigencentrality (how well connected a bull is to others, EC) and strength (proportion of connections among overall connections, ST) were calculated for each bull daily, where greater EC and ST values indicated more interactions. The statistical analyses were performed in RStudio. Negative binomial mixed effect models were fitted to AC (mean ± S.E., 26.05 ± 0.31 %), EC (26.50 ± 0.89), and ST (8.90 ± 0.21 %) as repeated measures, age (3.3 ± 0.3 yr), days exposed to cows (54 ± 3.1 d), and year as covariates, identification of bull as a random effect, and SRC as the outcome variable (21 ± 2, 2 to 45 calves). Estimates were transformed into percentage change. Days exposed to cows, year, and interactions were not significant (P &amp;gt; 0.05). Separate models with EC or ST (model-EC and model-ST) were built due to collinearity (r = 0.89, P &amp;lt; 0.001). In model-EC (marginal-R2 = 0.26, conditional-R2 = 0.70) bulls with increased AC (estimate = 2.16±0.67, P = 0.001), increased EC (0.56±0.24, P = 0.019), and younger (-20.75 ± 5.51, P &amp;lt; 0.001) had greater SRC. In model-ST (marginal-R2 = 0.25, conditional-R2 = 0.72) bulls with increased AC (2.29 ± 0.65, P &amp;lt; 0.001), increased ST (3.57 ± 0.98, P &amp;lt; 0.001), and younger (-19.90 ± 5.49, P &amp;lt; 0.001) had greater SRC. These preliminary results suggest that activity and social interactions during pre-breeding of beef bulls are related to SRC when accounted for age. Therefore, the behavior of beef bulls during the pre-breeding period might have the potential to predict their SRC, and future studies could investigate using this information to select bulls and form breeding groups aiming at optimization of the use of the bulls.

Relationship between bull signalment and testicular attributes in a Kenyan bull station.

Male fertility is essential to bovine reproduction, particularly when bulls are used for artificial insemination or single-sire breeding. Bull breeding and soundness examinations (BBSE) are routinely undertaken to identify potentially unfit bulls for breeding. Multiple criteria, including physical examination and determination of testicular and semen parameters, characterize BBSE. Knowledge interstices within this realm, especially in tropical African settings, necessitate pragmatic approaches to address the same. This study aimed to investigate the potential effects of bull parameters on testicular attributes in a tropical setting. The present study recruited healthy bulls (n = 96) aged >16 months with active semen collection used for artificial insemination at the Kenya Animal Genetic Resources Center. The breed breakdown was as follows: Ayrshire (n = 40), Boran (n = 3), Friesian (n = 36), Guernsey (n = 5), Jersey (n = 7), and Sahiwal (n = 5). Age, breed, body weight, scrotal circumference (SC), and testicular echotexture were collected, and the findings were analyzed using R statistical software. SC increased with age and body weight (p < 0.0001). SC varied from one breed to the others (p < 0.0001). Furthermore, as determined using trans-scrotal ultrasonography, hyperechoic testicular lesions were present in 30.21% of the bulls imaged, and the incidence was significantly related to age (p < 0.001). SC is significantly affected by age and body weight. The mean SC was higher in the Bos indicus, but this finding is only indicative because the Sahiwal and Boran sample sizes were small. Notably, the prevalence of hyperechoic testicular foci following trans-scrotal ultrasonography was common in older bulls. However, there is a need to further elucidate this phenomenon's pathophysiology with age as the etiology and possible sequelae of semen quality.

Improvement of dairy characters in farms and breeding value of the breeding bulls when assessing the quality of offspring

The article presents studies on comparison of the levels of precocity and milk productivity indicators of the daughters of Holstein bulls, who are evaluated for the quality of offspring simultaneously in two breeding plants of the Moscow region. According to the official ratings of breeding values, the bulls were divided into groups of "improving" and "worsening". The ratio of the daughters of the "best" and "worst" breeding bulls was 511:568 and 160:127 heads over the farms. It was determined which values of the differences in the "daughter – mother" indicators were increased in groups of officially evaluated bulls that received ratings of "improvers" and "deteriorators" according to the characteristics in these two breeding plants. The bulls being tested were fixed individually, and according to the number of pairs as the main ones. At the first insemination, the daughters of the "improving" group of bulls had 6.5–8.5 kg increased live weight of, but were relatively older by 0.36–0.6 months. According to the milk yield trait, the total yield of milk fat and protein, highly rated fathers in breeding plants were significantly inferior to competitors with low breeding value in milk yield by 688–1136 kg, according to the difference "mother – daughter" in the total yield of milk fat and protein per lactation – by 43.1–97.3 kg. In one of the farms, the "daughter – mother" differences in milk yield in all bull clusters increased by 599–1275 kg of milk; according to mass fat fraction (MFF) — by 0.02–0.20% and for mass protein fraction (MPF) — by 0.19–0.31%; in another farm, the increase in milk yield was by 43.8–1551 kg of milk and 0.05–0.13% according to the MPF. The daughters of the "worst" fathers in terms of MFF and MPF significantly outperformed the group of daughters of the "best" fathers in terms of "daughter–mother" differences by 35.6 and 61.7 kg of total milk protein and fat output over 305 days of lactation. At the same time, there were no significant differences between daughters and peers. The relativity of the official definition of the values of the breeding value of breeding bulls has been proved. It is proposed, regardless of the "commercial" and previously conducted estimates of breeding bulls, to take into account the indices of pedigrees and types of selection when breeding them. Conclusions are drawn about the significant influence of the factor and selection methods on the values of milk production traits; in order to save growing costs, it is proposed to optimize the live weight and age of insemination of heifers in farms.

Productive performance of beef bulls fed tall fescue silage or meadow fescue silage and complemented with cereal grains

ABSTRACT The purpose of this study was to compare the effectiveness of two different grasses offered to weaned beef breed bulls until slaughter. Three cuts of tall fescue (TF) and meadow fescue (MF) were harvested with as similar chemical composition as possible, pre-wilted and ensiled separately in bales. Forty newly weaned intact bulls of Continental beef breeds were kept indoors and randomized to one of the two silages, complemented with 2.5–3.0 kg grain/day, and followed until slaughter. The two silages were offered simultaneously from the same cut during most of the finishing period. Bulls receiving TF had a higher silage dry matter intake than bulls offered MF (7.69 vs. 7.04 kg-d; P = 0.0026) but had lower carcass weight (370 vs. 380 kg; P = 0.0357). From this limited study it was concluded that replacing traditional MF silage with TF silage might compromise the carcass performance of finishing beef bulls.