Dairy Bulls Research Articles

Genome-wide detection of non-additive quantitative trait loci for semen production traits in beef and dairy bulls

Semen production traits are important aspects of bull fertility, because semen quantity leads to direct profits for artificial insemination centres, and semen quality is associated with the probability of achieving a pregnancy. Most genome-wide association studies (GWASs) for semen production traits have assumed that each quantitative trait locus (QTL) has an additive effect. However, GWASs that account for non-additive effects are also important in fitness traits, such as bull fertility. Here, we performed a GWAS using models that accounted for additive and non-additive effects to evaluate the importance of non-additive effects on five semen production traits in beef and dairy bulls. A total of 65 463 records for 615 Japanese Black bulls (JB) and 50 734 records for 873 Holstein bulls (HOL), which were previously genotyped using the Illumina BovineSNP50 BeadChip, were used to estimate genetic parameters and perform GWAS. The heritability estimates were low (ranged from 0.11 to 0.23), and the repeatability estimates were low to moderate (ranged from 0.28 to 0.45) in both breeds. The estimated repeatability was approximately twice as high as the estimated heritability for all traits. In this study, only one significant region with an additive effect was detected in each breed, but multiple significant regions with non-additive effects were detected for each breed. In particular, the region at approximately 64 Mbp on Bos taurus autosome 17 had the highest significant non-additive effect on four semen production traits in HOL. The rs41843851 single nucleotide polymorphism (SNP) in the region had a much lower P-value for the non-additive effect (P-value = 1.1 × 10−31) than for the additive effect (P-value = 1.1 × 10−8) in sperm motility. The AA and AB genotypes on the SNP had a higher phenotype than the BB genotype in HOL, and there was no bull with the BB genotype in JB. Our results showed that non-additive QTLs affect semen production traits, and a novel QTL accounting for non-additive effects could be detected by GWAS. This study provides new insights into non-additive QTLs that affect fitness traits, such as semen production traits in beef and dairy bulls.

Energy Use in the EU Livestock Sector: A Review Recommending Energy Efficiency Measures and Renewable Energy Sources Adoption

This study conducts a review bringing together data from a large number of studies investigating energy use in EU livestock systems. Such a study has not been conducted previously, and improvements in our understanding of energy use concentrations in livestock systems will aid in developing interventions to achieve the EU’s 2030 and 2050 sustainability targets. The results from the Life Cycle Assessments included in this review indicate that energy use is concentrated in feed, housing, and manure management. In most systems, animal feed is the dominant energy use category. Regarding specific livestock categories, the studies covered indicate that energy use requirements range from 2.1 to 5.3 MJ/kg per ECM for cow milk, 59.2 MJ/kg for a suckler cow–calf, and 43.73 MJ/kg for a dairy bull, 15.9 MJ/kg to 22.7 MJ/kg for pork production, 9.6 MJ/kg to 19.1 MJ/kg for broiler production, 20.5–23.5 MJ/kg for chicken egg production. Our review indicates dominance of and dependence on fossil fuel and discusses the situation and research around transitioning towards renewable energy sources and improving energy efficiency. Our analysis indicates that existing energy use data in livestock systems are fragmented and characterized by multiple methodologies and considerable data gaps. In our view, there is a need for the development of a standardized methodology for measuring energy use in livestock systems, which we consider a necessary step to develop interventions that reduce fossil energy use in livestock systems and its contribution to climatic change.

Board Invited Review: Crossbreeding beef × dairy cattle for the modern beef production system.

Current trends in the United States dairy industry suggest that crossbred beef × dairy calves are replacing a proportion of the calf-fed Holstein steers slaughtered for beef each year. Economic pressures value preweaned beef × dairy calves at a premium over preweaned dairy bull calves; however, there is little modern data to support that intensively fed crossbred calves maintain their premium value over dairy steers across the supply chain. Data from international production systems and from historic research suggests that beef × dairy cattle had greater average daily gains and converted feed to gain more efficiently than dairy steers. Regarding carcass characteristics, across the literature crossbreds consistently yielded heavier carcasses that had lower proportions of trim than dairy steers. Fewer comparisons of beef × dairy and dairy steers exist in the literature for other economically relevant carcass characteristics such as ribeye area, backfat, marbling, tenderness, and eating quality. Existing published data are inconsistent among studies, highlighting the necessity for more research tailored to the United States beef production system

Non-gonadal linear type traits can discriminate reproductive ability of breeding dairy bulls.

Linear type traits are easily measurable phenotypic characteristics that help breed characterization, selection of animals for breeding and found to be associated with animals' performance. Unlike cows, there have been limited studies linking body linear traits with male reproductive ability and semen cryo-preservability of breeding bulls. Present study reported the age-related changes in body linear type traits in Frieswal (N=378) dairy bulls and its relevance with reproductive potentials of breeding bulls. Our results indicated that body frame size traits were significantly and positively correlated with gonadal linear traits. Among the selected body mophometric parameters body length, chest girth and head circumference were the important body linear type traits having capability to discriminate between bulls of frozen semen doses (FSD) and non-FSD categories. Discriminant function has been developed based on body linear traits of crossbred dairy bulls to find out males of superior reproductive potentials. Our finding provided evidence that body length (humerous tuberosity to tuber ischii) was the most powerful linear body trait associated with breeding bulls' reproductive ability and semen quality.

Increasing the frequency of ejaculate collection in young dairy bulls increases semen production and field fertility

Younger bulls typically produce lower volumes of semen per ejaculate with a lower sperm concentration than older more mature, bulls and often fail to meet semen demand using standard collection frequency schedules. The objective of this study was to assess the effect of ejaculate collection frequency on semen output, sperm quality and field fertility in young bulls under commercial conditions. Holstein Friesian bulls aged 366 ± 8 days (mean ± SEM) were assigned one of two ejaculate collection frequencies: (i) HF (n = 14 bulls), where ejaculates were collected twice a day, five days in each two-week period or (ii) LF (n = 12 bulls), where ejaculates were collected once a day, two days per week. The trial period continued until each bull reached both 20 ejaculates and 1000 marketable frozen semen straws. Subjective motility was assessed on all ejaculates pre-freeze and post-thaw (at 0 and 2 h). A subset of ejaculates were assessed post-thaw by computer-assisted sperm analysis for motility, kinematics and morphological defects and by flow cytometry for viability, membrane fluidity, acrosome integrity, reactive oxygen species and DNA fragmentation. A total of 13,846 inseminations (9,541 for HF and 4,305 for LF) were carried out on dairy cows and heifers. HF reached the 1000 straw threshold 41 days earlier than LF (P < 0.01) with the same number of ejaculates. Ejaculate volume and sperm concentration were not affected by treatment but the first ejaculate of the day (HF only) had a greater volume (P < 0.001) and sperm concentration (P < 0.05) than the second ejaculate. HF had higher pre-freeze total (P < 0.01) and gross (P < 0.05) motility than LF. HF had higher post-thaw (2 h) total and gross motility than LF (P < 0.05). Ejaculate rejection rates did not differ between treatments. There was no effect of treatment, week or ejaculate number of the day (HF only) on post-thaw motility and kinematic parameters or sperm viability, membrane fluidity, acrosome integrity and DNA fragmentation. However, HF had lower superoxide production than LF (P < 0.05). Pregnancy per artificial insemination was 64.5 ± 1.0% and 59.9 ± 1.1% for the HF and LF bulls, respectively (mean ± SEM; P = 0.05). In conclusion, collecting ejaculates more frequently from young bulls significantly reduced the number of days required to obtain 1000 straws, increased semen quality in terms of lower superoxide production and increased field fertility.

Hematological condition of breeding bulls after a long winter period of operation in the conditions of the Udmurt Republic

Purpose: to study hematological parameters of blood in bulls-producers of dairy breeds on the day of semen collection in the Udmurt Republic after a long winter period of operation, depending on the breeds, age and place of selection.Materials and methods. The work was performed at the Federal Research Center for Animal Husbandry named after Academy Member L. K. Ernst on the basis of AO "Udmurtplem" of the Udmurt Republic in the period from 2020 to 2021 on dairy bulls (n=20) aged 15-69 months, including a purebred Holstein breed of domestic selection (n=6), a Holstein black-and-white breed of European selection (the Netherlands, n=6), a black-and-white breed with blood transfusion on Holsteins on at the level of 94-98% (n=8). The content of white blood cells, red blood cells, hemoglobin and hematocrit, depending on age and breed, was studied on the ABC VET hematological analyzer on the day of taking the seed.Results. It was found that on average, in 20 bulls aged 15-69 months, the level of white blood cells was at the level of reference values of 8.8±0.25 x 109/l, red blood cells 10.3 x 1012/l, which is 50% more than the reference values. The concentration of hemoglobin is 128.0±2.92 g/l, hematocrit is on average 54.3%, with a norm of 24-46%. Breeding bulls at a reliable level, differing in age, showed that some animals had high indicators for red blood cells of 10.3±0.26 x 102, for hematocrit of 54.3% against 24-46% of reference values. Also, according to hematological indicators, there was a tendency to increase the concentration of hemoglobin and hematocrit in European-bred bulls.Conclusion. The study of the variability in hematological parameters depending on the selection showed that there is no significant difference in leukocytes and all indicators are at the level of reference values, and in erythrocytes more than 50% than the highest indicators. The highest hemoglobin values were at the level of 141-156 g/l instead of 128 g/l according to the highest reference values. Hematocrit also showed high max values in all groups in comparison with the reference values of 59-66% versus 46% in the norm. It is necessary when analyzing hematological blood parameters in addition to the average statistical indicators (M+m) also, monitor the variability (min-max) in order to obtain more objective information.

НЕКОТОРЫЕ МЕТОДЫ ПОВЫШЕНИЯ ПРОИЗВОДСТВА ГОВЯДИНЫ В УСЛОВИЯХ КОЛЫМЫ

For the first time in the conditions of the Magadan region, studies were carried out to study the characteristics of the meat productivity of crossbred bulls obtained from absorption and industrial crossing of animal meat breeds. The effectiveness of the organization of specialized rearing of crossbred young animals, taking into account its breed specificity, has been established. Scientific and economic experiments were carried out on young cattle in the production conditions of the Magadan region. The work was carried out in accordance with the plan for scientific research in 2021. The purpose of the research was to obtain data on a comparative analysis of the meat productivity of bulls of different genotypes obtained as a result of industrial and absorption crossing using animals of specialized meat breeds. The control group consisted of purebred dairy bulls. It has been established that crossbred bulls have the ability to intensively build muscle and form full-flesh carcasses by the age of 18 months. They are superior to purebred Holstein peers in pre-slaughter and slaughter weight, slaughter yield and meat index. The conducted studies showed that the differences in the intensity of growth, the use of feed and the productivity of crossbred and purebred young animals had a significant impact on the efficiency of their fattening. The data of economic analysis indicate a higher profitability of rearing crossbred bulls of the studied genotypes. The research results prove the successful use of absorption and industrial crossing with producers of specialized meat breeds in the conditions of commercial livestock enterprises of the Magadan region. The data obtained can be used to improve the efficiency of breeding work in beef cattle breeding in the development of plans for breeding work in the commercial farms of the region.

THE RELATIONSHEEP OF THE BREEDING VALUE OF BULLS WITH THE PRODUCTIVITY OF THEIR MOTHERS AND THE BREEDING VALUE OF THEIR PARENTS BREEDING

THE RELATIONSHEEP OF THE BREEDING VALUE OF BULLS WITH THE PRODUCTIVITY OF THEIR MOTHERS AND THE BREEDING VALUE OF THEIR PARENTS BREEDING

Service Sire Effects on Body Condition Score, Milk Production, and Rebreeding of Mixed-Aged Dairy Cows Bred to Angus and Hereford Bulls—A Case Study in New Zealand

Beef-breed bulls are used in dairy herds to produce a calf of greater value for finishing than calves sired by dairy bulls. There is limited research about which beef-breed bulls are most appropriate, and whether any negative impact on cow performance in terms of milk production and rebreeding should be considered. The aim of this case study was to compare the body condition score, milk production, and rebreeding performance of mixed-aged dairy cows bred to a selection of Angus and Hereford beef-breed bulls. Body condition score, post-calving live weight, milk production, rebreeding performance, and survival of 952 mixed-aged dairy cows artificially bred to 65 Angus and Hereford bulls were compared. There was no effect of service sire on post-calving live weight, days in milk, milk production, or inter-calving intervals of mixed-aged cows. Service sire had an effect on the calving day due to differences in gestation length (p &lt; 0.001), although this did not translate into an effect on days in milk. A longer gestation length negatively influenced pregnancy rates, and greater birth weight of the calf negatively influenced survival to rebreeding (p &lt; 0.05), indicating the potential for an effect of service sire. Selection of beef-breed service sires for dairy cows should include emphasis on lighter calves and shorter gestation lengths. The general absence of the service sire effect on the parameters measured in this study indicated that any of the service sires used in this experiment would be appropriate for use over dairy cows.

Youngstock health: a focus on Mycoplasma bovis, nematode control and the use of NSAIDS in scour

Foreword Farming is under increasing scrutiny on environmental issues (including greenhouse gas emissions, resource use, water and air quality, biodiversity and other impacts), in addition to increasing economic and social pressures. It is increasingly clear that we need to ensure that every animal has a good healthy life, while reducing losses throughout the production system. As cattle vets, we work with cattle at every stage of the production cycle, but on many dairy farms, youngstock are still seen as being of secondary importance compared with the mature herd, suffering significant levels of disease, and sustaining high mortality. This is despite the fact that dairy replacements are, or should be, the group with the highest genetic merit on the farm and are the future of the herd. In contrast to the dairy herd, calves from the suckler herd are the only saleable product of the cow and thus her whole production for the year is lost if the calf should die. Despite this, more could still be done on many farms to improve health and productivity of these calves allowing them to be finished faster with associated environmental benefits. For environmental, economic and social reasons, it is no longer acceptable to cull dairy bull calves, or to ignore high levels of morbidity or mortality. An animal that has a suboptimal growth rate or dies represents a financial loss to the farmer, a welfare concern to the consumer, and an environmental impact that is not compensated for by food (milk or meat) production. If we are to serve our clients to the best of our ability and help make their businesses as sustainable as possible, we need a greater focus on youngstock. This supplement is a good place to start with its focus on Mycoplasma bovis, nematode control and the use of NSAIDs in calf scour.

PSV-5 Relationship between sire conception rate, sperm motility, sperm SERPINA5 relative concentration, and in vitro produced embryos in dairy bulls

Abstract Sire conception rate (SCR) is a field measure of fertility among bulls, but it can be influenced by several factors (Sperm transport, sperm-egg binding, early embryo development, etc). The objective of this study was to evaluate the relationship between SCR, sperm motility, SERPINA5 concentrations, and in vitro embryo development. Measurements were performed in 19 bulls with SCR values ranging from -7.7 to 4.45. For each bull, an aliquot of frozen-thawed semen was used for analyses of total (TMOT) and progressive (PROG) motility. Remaining semen was fixed with 2% formaldehyde, and concentration of SERPINA5 was determined by immunolocalization (antibody SERPINA5/Dylight405; PA5-79976-Invitrogen / ab201798-Abcam). Mean fluorescence intensity was determined in ~200 sperm heads/bull. Approximately 149 oocytes/bull were fertilized in vitro for embryo development analysis (cleavage and blastocyst rates). Statistical procedures were performed in SAS (9.4) using the procedures CORR for correlations (SCR, TMOT, PROG, SERPINA5, cleavage and blastocyst) and GLIMMIX for comparison of “field-fertility” (SCR divided in HIGH or LOW) and “field-embryo-fertility” (LOW-SCR sires were divided based on blastocyst rate (HIGH or LOW) resulting in two classifications; LOW-HIGH≥31% and LOW-LOW≤26%, respectively). There were positive correlations (P &amp;lt; 0.05) between cleavage-blastocyst (r=0.50), SERPINA5-cleavage (r=0.48), and TMOT-PROG (r=0.76). Sire SCR was not associated with SERPINA5, TMOT, PROG, cleavage and blastocyst rate (P &amp;gt; 0.52). Among LOW-SCR sires, LOW-LOW sires (-4.83±0.60) tended to have a better SCR score than LOW-HIGH (-6.18±0.42) sires (P = 0.08), but there were no differences (P &amp;gt; 0.43) between LOW-HIGH, LOW-LOW, and HIGH sires for SERPINA5, TMOT, PROG, and cleavage. In conclusion, some LOW SCR sires have good embryo development indicating a different mechanism for their low SCR; however, these differences in SCR could not be explained by TMOT, PROG, SERPINA5, cleavage and blastocyst. There were, however, positive correlations between cleavage-blastocyst rate, and SERPINA5-cleavage rate.

PSV-10 The effects of maternal programming on postnatal growth and inflammation in neonatal dairy bull calves

Abstract Neonatal dairy calves are highly susceptible to respiratory and digestive diseases. A mechanism that could be predisposing calves to disease is maternal programming. We hypothesized that high milk production and/or mastitis infection during gestation will 1) affect postnatal growth and development 2) cause increased inflammation in neonatal dairy bull calves. Calves (n = 45) were selected from dams classified has high producers (HI; Top 25% for herd M305; n = 7), high producers with high SCC (HIMAST; SCC test during pregnancy over 200,000 cells/mL; n = 15), moderate producers (MOD; lower 60% for herd M305; n = 17) or moderate producers with high SCC (MODMAST; n = 6). Calves were transported to the University of Rhode Island at 24 hrs of age. Body weights and body measurements (crown rump length (CRL), skull length (SL), skull width (SW), Girth, Height) were collected at 24 hrs (Initial) and at weaning (8 weeks). C-reactive protein (Abclonal, Woburn, MA) and Malondialdehyde (Abcam, Cambridge, MA) analyses were performed on plasma samples collected 72 hrs post travel. Data were analyzed in SAS using repeated measures (BW and growth measurements) and proc mixed (inflammatory biomarkers). As expected, an effect of time was observed on calf BW, CRL, SL, SW, Girth and Height (P ≤ 0.01). However, no difference in calf BW, CRL, SL, SW, Girth and Height were observed between groups (P&amp;gt;0.05). No effect of dam milk production and/or SCC during gestation was observed on CRP or MDA concentrations at 72 hrs post travel (P ≥ 0.17). In conclusion, high maternal milk production and/or mastitis infection during gestation does not affect calf BW and body measurements when analyzed overtime. Correlation analyses will be performed to better understand the relationship between maternal programming and calf growth. Additional inflammatory biomarkers are also going to be evaluated.

19 Comparative Evaluation of Human-edible Animal Products Derived from Offspring of Genome Edited and Control Cattle

Abstract Risk assessments of genetically modified (GM) animals include evaluating whether milk and meat derived from the GM animal is as nutritious to humans and/or animals as traditionally-bred animals. The underlying assumption of this comparative approach is that traditionally-bred animals have a well-established history of safe use. The goal of this project was to provide empirical data on the development and nutritional composition of animal products derived from the offspring of a genome edited dairy bull, homozygous for the dominant PC Celtic POLLED allele. The bull was crossed with horned Hereford (HH) cows (pp) to obtain five male and one female heterozygous hornless (RC) calves. Hereford, Angus and Holstein bulls were also bred to Hereford cows to produce five HH calves, two polled Angus/Hereford (AH) calves, and three horned Holstein/Hereford (HO) calves (with 25% genetic identity to the hornless offspring), respectively as contemporary controls. Weights were recorded at 8 months, 1 year and slaughter (n = 9–16). Following calving, individual quarters of the RC heifer (RC.calf1), one HO heifer (HO.calf2), two horned HH heifers, and one contemporaneous hornless AH cow (3113) were milked at varying timepoints during the first seven weeks of lactation. Meat samples were collected from the 6 hornless RC calves and 3 horned HO comparator offspring after slaughter. Proximate analysis was conducted for meat and milk samples. Cattle that inherited a POLLED allele from the genome-edited bull showed no differences in their overall growth (Figure 1) or meat composition (Figure 2) when compared to contemporary controls. Milk composition varied between animals and by days in milk (DIM), although values were within the normal range reported in peer-reviewed literature (Figure 3). Bovine milk composition is known to be influenced by breed, nutrition, parity, and DIM, making it difficult to obtain appropriate comparators in experiments with a limited number of GM animals.

PSI-8 Determining the effect of dam milk production and mastitis infection during pregnancy on blood biochemistry in dairy bull calves

Abstract Maternal programming can affect offspring health postnatally. We hypothesized that high milk production and/or mastitis infection during pregnancy will adversely affect calf blood biochemical analytes. Holstein bull calves (n = 45) were transported to the University of Rhode Island within 24 hrs of birth. Calves were classified by dam production and somatic cell counts (SCC) during pregnancy; HI (top 25% for herd M305, n = 7), MOD (lower 60% for herd M305, n = 16), HIMAST (HI with SCC ≥ 200,000 cells/mL; n = 15), and MODMAST (MOD with high SCC; n=6). Calves were sampled once a week for 8 wks. Serum was sent to the Missouri State Veterinary Medical Diagnostic Laboratory (Columbia, MO) for analyses. Results were analyzed in SAS using proc mixed. At wk 1, Calcium (Ca) concentrations were greater in HI calves (11±0.61mg/dL; P =.05) than MOD calves (10± 0.25mg/dL). At wk 3, Ca concentrations were greater in HIMAST (10± 0.13mg/dL) compared to HI (8±.048mg/dL; P&amp;lt;0.01) and MOD (9±0.36mg/dL; P =.02) calves respectively. MODMAST calves (10 ± 0.460 mg/dL) exhibited greater Ca concentrations than HI calves (P = 0.05). Aspartate aminotransferase concentrations were greater in HIMAST calves compared to MODMAST calves at wk 1 (36±2.49 Units (U)/L vs. 27±2.63U/L; P = .04) and wk 8 (79±7.08U/L vs. 47±5.71U/L; P&amp;lt;0.01). At wk 8, total protein concentrations were greater in HIMAST (6 ± .13g/dL) calves compared to MODMAST(5±0.13g/dL; P =.01) and MOD calves(5±.13g/dL; P = .03). In conclusion, maternal mastitis infection and production level during pregnancy does affect key circulating factors in the offspring. Correlation and gene expression analyses will be performed to better understand these changes.

PSII-19 The Effects of Maternal Programming on Dairy Bull Calf Response to an Intravenous Glucose Tolerance Test

Abstract Calves are prone to health issues with high mortality observed during the first 3 weeks of life. We hypothesized that dam milk production levels and/or mastitis infection during gestation will lead to reduced insulin production and increased circulating glucose concentration in response to an Intravenous Glucose Tolerance Test (IVGTT) in young dairy bull calves. Calves (n = 45) were selected from dams classified has high producers (HI; Top 25% for herd M305; n = 7), high producers with high somatic cell count (SCC; HIMAST; SCC test during gestation over 200,000 cells/mL; n = 15), moderate producers (MOD; lower 60% for herd M305; n =17) or moderate producers with high SCC (MODMAST; n = 6). IVGTT were performed on the calves at 7 weeks of age. Blood samples were collected prior to (-30, -15 and 0 min) infusion of glucose. After glucose (0.15 grams /kg bw) administration, samples were collected at 2, 5, 10, 15, 30, 60, and 120-minutes post infusion. Serum insulin and glucose concentrations were determined at Cornell Veterinary Medical Diagnostic Laboratory (Ithica, NY). Data were analysed in SAS using Proc Mixed. Insulin:glucose ratio was analysed using Proc Mixed with repeated measures for treatment x time. No effect of maternal milk production and/or mastitis infection during gestation was observed on calf baseline insulin, insulin AUC, baseline glucose or glucose AUC (P ≥ 0.12). Similarly, no difference in Insulin:Glucose ratio was observed in these calves (P = 0.66). In conclusion, high maternal milk production and/or mastitis infection may not have an effect on circulating insulin production in calves in response to an IVGTT. Correlation analyses will be performed on these data, as well as additional analyses, to determine if insulin sensitivity or response (ie: phase 1 response) was altered further.

Determining the Accuracy of Holstein Bull Semen Prices with a Two-Tier Efficiency Model

The pricing accuracy of dairy bull semen available for artificial insemination is investigated using a price model cast in terms of a two-tier efficiency model, which allows estimating an overprice and underprice given the net return the bull’s daughter is expected to contribute to the farm based upon the transmittable trait characteristics of a bull. The estimation produces statistically significant coefficients, including the coefficients for the overpricing and underpricing of the semen. The average estimate of overpricing is around 25%, and the average estimate of underpricing is around 33%. As expected, low semen prices tend to be underpriced and high semen prices tend to be overpriced.

Creating an Optimal Structure of the Diet to Increase the Productivity of Calves in Calves of Dairy Breeds

The diet of dairy bulls contains little high-quality protein. This primarily affects the main indicators of feed growth and conversion. Poor-quality protein in the diet leads to excessive formation of ammonia in the rumen. Increased concentrations of ammonia, does not participate in the synthesis of microbial protein and is excreted in the urine, which is an energy-consuming process and negatively affects the gains. Ammonia has a toxic effect, when an excessive amount of it enters the bloodstream, where it causes hyperamonymy, and creates an additional load on the liver.&#x0D; Aims: The aim of the study is to create an optimal structure of the diet, in which the protein will be completely utilized by the rumen microbiota and animal protein will be reproduced on its basis to create the growth potential of fattening bulls. The development of this diet will allow creating a technology for fattening steers for meat that is economically profitable with a high proportion of healthy animals with high productivity.&#x0D; Methodology: The studies were conducted on calves of the Kholmogorsky breed raised in the VNIIFBIP vivarium, aged from 1.5 months to 14 months. At the age of 1.5 months, the animals were intensively accustomed to the introduction of concentrates and coarse feeds. Feeding with a milk substitute was carried out up to the age of 70 days with free access to mixed feed and hay.&#x0D; Results: During the study, the main factors responsible for the metabolic processes in bull calves were identified. The factors of digestibility in the rumen were studied. Physiological and biochemical parameters were established to assess the reduction of the risks of hyperammonemia. The use of concentrated feed against the background of strict proportional administration together with coarse feed with intensive cultivation and fattening of dairy bulls and the normal course of enzymatic processes in the rumen and throughout the body allows you to achieve an average daily increase of up to 1420 g by 14 months of age and reduce feed conversion.&#x0D; Conclusion: The results obtained make it possible to increase the productivity of fattening steers in regions with a large number of dairy cattle and the availability of concentrated feed.

Genomic prediction of milk-production traits and somatic cell score using single-step genomic best linear unbiased predictor with random regression test-day model in Thai dairy cattle

Cow genotypes are expected to improve the accuracy of genomic estimated breeding values (GEBV) for young bulls in relatively small populations such as Thai Holstein-Friesian crossbred dairy cattle in Thailand. The objective of this study was to investigate the effect of cow genotypes on the predictive ability and individual accuracies of GEBV for young dairy bulls in Thailand. Test-day data included milk yield (n = 170,666), milk component traits (fat yield, protein yield, total solids yield, fat percentage, protein percentage, and total solids percentage; n = 160,526), and somatic cell score (n = 82,378) from 23,201, 82,378, and 13,737 (for milk yield, milk component traits, and SCS, respectively) cows calving between 1993 and 2017, respectively. Pedigree information included 51,128; 48,834; and 32,743 animals for milk yield, milk component traits, and somatic cell score, respectively. Additionally, 876, 868, and 632 pedigreed animals (for milk yield, milk component traits, and SCS, respectively) were genotyped (152 bulls and 724 cows), respectively, using Illumina Bovine SNP50 BeadChip. We cut off the data in the last 6 yr, and the validation animals were defined as genotyped bulls with no daughters in the truncated set. We calculated GEBV using a single-step random regression test-day model (SS-RR-TDM), in comparison with estimated breed value (EBV) based on the pedigree-based model used as the official method in Thailand (RR-TDM). Individual accuracies of GEBV were obtained by inverting the coefficient matrix of the mixed model equations, whereas validation accuracies were measured by the Pearson correlation between deregressed EBV from the full data set and (G)EBV predicted with the reduced data set. When only bull genotypes were used, on average, SS-RR-TDM increased individual accuracies by 0.22 and validation accuracies by 0.07, compared with RR-TDM. With cow genotypes, the additional increase was 0.02 for individual accuracies and 0.06 for validation accuracies. The inflation of GEBV tended to be reduced using cow genotypes. Genomic evaluation by SS-RR-TDM is feasible to select young bulls for the longitudinal traits in Thai dairy cattle, and the accuracy of selection is expected to be increased with more genotypes. Genomic selection using the SS-RR-TDM should be implemented in the routine genetic evaluation of the Thai dairy cattle population. The genetic evaluation should consider including genotypes of both sires and cows.

Quantifying genetic differences between exported dairy bull calves and those sold for domestic beef production

Selection bias is introduced when selection among individuals exists but the information used to inform that selection decision is not considered in downstream genetic evaluations. Genetic evaluations are undertaken in several countries for carcass-related metrics in prime cattle; no consideration is generally taken for animals that are harvested at a younger age for veal production and thus do not express the prime carcass phenotype. Although no veal industry exists in Ireland, dairy calves are routinely exported to continental Europe for veal production. The objective of the present study, based on a cross-sectional analysis of calf export data, was to determine quantitatively if genetic variability exists in whether purchased dairy-bred bull calves are immediately exported or retained within the country for domestic production. Also of interest was whether such a genetic difference was associated with differences in carcass weight, conformation score, and fat score in prime cattle relatives. Editing criteria were imposed to consider only Holstein-Friesian bull calves. Post-editing, the fate of 43,890 Holstein-Friesian bull calves (<100 d of age) was available; variance components for the binary phenotype (sold for export or not) were estimated using both linear and threshold animal models, and genetic correlations with carcass traits from 56,366 prime cattle were estimated. The heritability (standard error) of whether or not a calf was exported was 0.04 (0.01) on the linear scale and 0.07 (0.02) on the threshold scale. Although no explicit maternal genetic effect was detected, the proportion of the phenotypic variance due to maternal effects was 0.03 to 0.07. The genetic correlation (standard error) between the export phenotype with carcass weight, conformation score [scale 1 (poor) to 15 (excellent)], and fat score [scale 1 (thin) to 15 (fat)] in prime cattle was 0.002 (0.12), −0.25 (0.12), and −0.32 (0.11), respectively. The low heritability of the calf export phenotype and lack of a strong genetic correlation with carcass metrics suggest that other calf features might be greater determinants of the eventual fate of the calf. Accounting for the export phenotype in genetic evaluations of carcass traits in prime cattle had a negligible effect on the estimated breeding values for carcass merit.

Evaluation of bull fertility in Italian Brown Swiss dairy cattle using cow field data

Dairy bull fertility is traditionally evaluated using semen production and quality traits; however, these attributes explain only part of the differences observed in fertility among bulls. Alternatively, bull fertility can be directly evaluated using cow field data. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. We then estimated sire conception rate using only factors related to the bull. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between high-fertility and low-fertility bulls. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.