Stem cell-based strategies and challenges for production of cultivated meat.

Cultivated meat scale-up and industrial production will require multiple stable cell lines from different species to recreate the organoleptic and nutritional properties of meat from livestock. In this Review, we explore the potential of stem cells to create the major cellular components of cultivated meat. By using developments in the fields of tissue engineering and biomedicine, we explore the advantages and disadvantages of strategies involving primary adult and pluripotent stem cells for generating cell sources that can be grown at scale. These myogenic, adipogenic or extracellular matrix-producing adult stem cells as well as embryonic or inducible pluripotent stem cells are discussed for their proliferative and differentiation capacity, necessary for cultivated meat. We examine the challenges for industrial scale-up, including differentiation and culture protocols, as well as genetic modification options for stem cell immortalization and controlled differentiation. Finally, we discuss stem cell-related safety and regulatory challenges for bringing cultivated meat to the marketplace.

Animal board invited review: Animal agriculture and alternative meats - learning from past science communication failures.

Sustainability discussions bring in multiple competing goals, and the outcomes are often conflicting depending upon which goal is being given credence. The role of livestock in supporting human well-being is especially contentious in discourses around sustainable diets. There is considerable variation in which environmental metrics are measured when describing sustainable diets, although some estimate of the greenhouse gas (GHG) emissions of different diets based on varying assumptions is commonplace. A market for animal-free and manufactured food items to substitute for animal source food (ASF) has emerged, driven by the high GHG emissions of ASF. Ingredients sourced from plants, and animal cells grown in culture are two approaches employed to produce alternative meats. These can be complemented with ingredients produced using synthetic biology. Alternative meat companies promise to reduce GHG, the land and water used for food production, and reduce or eliminate animal agriculture. Some CEOs have even claimed alternative meats will 'end world hunger'. Rarely do such self-proclamations emanate from scientists, but rather from companies in their efforts to attract venture capital investment and market share. Such declarations are reminiscent of the early days of the biotechnology industry. At that time, special interest groups employed fear-based tactics to effectively turn public opinion against the use of genetic engineering to introduce sustainability traits, like disease resistance and nutrient fortification, into global genetic improvement programs. These same groups have recently turned their sights on the 'unnaturalness' and use of synthetic biology in the production of meat alternatives, leaving agriculturists in a quandary. Much of the rationale behind alternative meats invokes a simplistic narrative, with a primary focus on GHG emissions, ignoring the nutritional attributes and dietary importance of ASF, and livelihoods that are supported by grazing ruminant production systems. Diets with low GHG emissions are often described as sustainable, even though the nutritional, social and economic pillars of sustainability are not considered. Nutritionists, geneticists, and veterinarians have been extremely successful at developing new technologies to reduce the environmental footprint of ASF. Further technological developments are going to be requisite to continuously improve the efficiency of animal source, plant source, and cultured meat production. Perhaps there is an opportunity to collectively communicate how innovations are enabling both alternative- and conventional-meat producers to more sustainably meet future demand. This could counteract the possibility that special interest groups who promulgate misinformation, fear and uncertainty, will hinder the adoption of technological innovations to the ultimate detriment of global food security.

A novel risk assessment tool for bovine respiratory disease in preweaned dairy calves.

Due to the increased morbidity and mortality of bovine respiratory disease (BRD) in dairy calves, as well as an increasing urgency for the judicious use of antimicrobials in farm animals, a comprehensive risk assessment tool for BRD in preweaned dairy calves has been designed based on a longitudinal and a cross-sectional study. As a multifactorial disease complex in which immune function stressors increase susceptibility to respiratory pathology, risk management programs for environmental and husbandry practices may be an effective approach for BRD control. Practices of known or suspected effect on BRD in preweaned calves have been explored in 2 large studies correlating management factors to BRD prevalence (BRD 100 study) and incidence (BRD 10K study) and forming the scores presented here. Priority was given to results from multivariable over univariable model estimates. However, when used, univariable model estimates were adjusted for confounders or stratified by effect modifiers if necessary. Regression coefficients were translated into scores, which are presented in a field-ready tool consisting of (1) a risk assessment questionnaire, which identifies the herd-specific risk factors and the risk scores associated with each; (2) the California BRD scoring system to estimate the BRD prevalence at the time of risk assessment for future comparison with the prevalence after interventions; and (3) the BRD control and prevention herd management plan, which can be used to plan and track the interventions identified. Scores for 100 dairies across California were used to benchmark a dairy's risk on a spectrum. With the help of the risk assessment tool, dairy producers, calf managers, and veterinarians may be able to adjust management factors that affect BRD risk on a farm and objectively monitor BRD prevalence before and after management interventions. As a result, the BRD risk assessment tool described here is the first comprehensive effort for herd-specific BRD control and prevention.

Preweaning cost of bovine respiratory disease (BRD) and cost-benefit of implementation of preventative measures in calves on California dairies: The BRD 10K study.

Bovine respiratory disease (BRD) is a multifactorial disease that is estimated to affect 22% of preweaned dairy calves in the United States and is a leading cause of preweaning mortality in dairy calves. Overall cost of calfhood BRD is reflected in both the immediate cost of treating the disease as well as lifetime decrease in production and increased likelihood of affected cattle leaving the herd before their second calving. The goal of this paper was to develop an estimate of the cost of BRD based on longitudinal treatment data from a study of BRD with a cohort of 11,470 preweaned dairy calves in California. Additionally, a cost-benefit analysis was performed for 2 different preventative measures for BRD, an increase of 0.47 L of milk per day for all calves or vaccination of all dams with a modified live BRD vaccine, using differing assumptions about birth rate and number of calves raised per year. Average short-term cost of BRD per affected calf was $42.15, including the use of anti-inflammatory medications in the treatment protocols across all management conditions. The cost of treating BRD in calves appears to have increased in recent years and is greater than costs presented in previous studies. A cost-benefit analysis examined different herd scenarios for a range of cumulative incidences of BRD from 3 to 25%. Increasing milk fed was financially beneficial in all scenarios above a 3% cumulative incidence of BRD. Use of a modified live vaccine in dams during pregnancy, examining only its value as a form of BRD prevention in the calves raised on the farm, was financially beneficial only if the cumulative incidence of BRD exceeded 10 to 15% depending on the herd size and whether the dairy farm was raising any bull calves. The cost-benefit analysis, under the conditions studied, suggests that producers with high rates of BRD may benefit financially from implementing preventative measures, whereas these preventative measures may not be cost effective to implement on dairy farms with very low cumulative incidences of BRD. The long-term costs of calfhood BRD on lifetime productivity were not factored into these calculations, and the reduction in disease may be associated with additional cost savings and an improvement in calf welfare and herd life.

Bovine respiratory disease (BRD) cause-specific and overall mortality in preweaned calves on California dairies: The BRD 10K study.

Mortality in preweaned dairy calves is a significant source of economic loss for dairy producers. In particular, bovine respiratory disease (BRD) is a leading cause of death in preweaned dairy calves. The objectives of this study were to investigate management practices and their effects on mortality, both that specifically attributed to BRD and overall mortality due to all causes, in preweaned dairy calves. Rates of failure of passive transfer of immunity (FPT) are also reported. The study consisted of a convenience sample of 5 dairies across California, selected based on management practices, calf records, location, and size. Trained study personnel performed comprehensive calf management surveys on every dairy at least once every season. Calves were enrolled in the study at birth and followed until weaning. Mixed-effect logistic regression models were specified for the outcomes all-cause mortality (any death before weaning) and mortality attributed to BRD. The 2 final models included a total of 11,470 calves that were born on the study dairies and followed until weaning. The study cohort's overall crude mortality was 2.8%, with crude mortality of individual dairies ranging from 1.7 to 7.2%. The proportion of mortality attributed to BRD was 19.3%, with a range of 0 to 27.1% on the study dairies. Increasing the frequency of changing maternity pen bedding was associated with a decreased risk of mortality due to BRD. Calves diagnosed with BRD in the spring had an increased risk of mortality compared with calves born in the summer; mortality in calves with fall and winter BRD diagnoses did not different significantly from that in summer. Season of mortality was not significant in either model. Feeding ≥5.7 L of milk per day per calf (vs. ≤3.7 L/d) decreased the risk of mortality in calves over 21 d of age. Twins had a 68% increased risk of all-cause mortality compared with calves born as singletons. Both mortality models showed an association between administration of a modified live vaccine in dams (targeting BRD pathogens) and a decreased risk of mortality in calves. Using a serum total protein cut-off of 5.2 g/dL, 16.8% of calves had FPT, with a mean serum total protein concentration of 5.94 ± 0.06 g/dL across all calves sampled.

Epidemiology of bovine respiratory disease (BRD) in preweaned calves on California dairies: The BRD 10K study.

Bovine respiratory disease (BRD) is one of the leading causes of death in dairy heifers. The objective of this prospective cohort study was to characterize the epidemiology of BRD in preweaned dairy calves and to identify management practices associated with decreased risk of BRD. Dairies were chosen for the study based on management practices, location, size, and willingness to participate. A total of 6 dairies, ranging in size from 700 to 3,200 milking cows, in 6 counties across California's Central Valley, were enrolled in the study for at least 1 year. A total of 11,945 calves were born on the study dairies and followed until weaning. Incidence of BRD was estimated using treatment records. Trained study personnel performed comprehensive calf management surveys and estimated BRD prevalence on every dairy at least once every season. A shared frailty model was used to model the associations between management practices and BRD hazard. The final models included data from complete records of 11,470 calves. The overall BRD study period prevalence across the study herds was 22.8%. The mean BRD incidence density rate on all the study dairies was 0.17 BRD cases [95% confidence interval (CI) = 0.16-1.74] per calf-month at risk. The shared frailty model identified that feeding only waste or saleable milk (compared with use of milk replacer), feeding over 3.8 L of milk per day to calves under 21 d of age, frequent changing of maternity pen bedding, and administration of modified live or killed BRD vaccines to dams before calving significantly reduced the risk of BRD. Risk factors for BRD included housing calves in wooden hutches with metal roofs, compared with all-wood hutches, twin births, and perception of dust occurring "regularly," as reported by calf managers, compared with a perception of "no dust" in the calf-raising area. All 4 seasons were analyzed, and both summer (hazard ratio = 1.15; 95% CI = 1.01 to 1.32) and spring (hazard ratio = 1.26; 95% CI = 1.11 to 1.44) were associated with a higher risk of BRD compared with winter. The current longitudinal study identified specific housing and feeding practices that could be modified to decrease risk of BRD. In addition, season was observed to have a strong effect on calves' risk of developing BRD on California dairies.

Management factors associated with bovine respiratory disease in preweaned calves on California dairies: The BRD 100 study.

The objective of this cross-sectional study was to determine how management practices on California dairies may be associated with bovine respiratory disease (BRD) in preweaned calves. A convenience sample of 100 dairies throughout California, providing a study population of 4,636 calves, were visited between May 2014 and April 2016. During each farm visit, in-person interviews with the herd manager or calf caretaker were conducted to collect information about herd demographics, maternity pen, colostrum and calf management, herd vaccinations, and dust abatement. A random sample of preweaned calves was identified and evaluated for the presence of BRD using a standardized tool. A survey-adjusted generalized linear mixed model with a logit link function was fitted with calf as the unit of analysis and dairy as the random effect. Mean study herd size (±SE) was 1,718 (±189.9) cows. Survey-adjusted estimates of breed types in the sample were 81.6% (±0.6) Holstein, 13.1% (±0.4) Jersey, and 5.3% (±0.5) crossbred or other purebred breeds, and calf sex proportions were 73.8% (±1.0) female and 26.2% (±1.0) male. Overall survey-adjusted BRD prevalence in the study herds was 6.91% (±0.69). Housing factors positively associated with BRD were metal hutches compared with wood hutches [odds ratio (OR) = 11.19; 95% confidence interval (CI) = 2.80-44.78], calf-to-calf contact in calves >75 d of age (OR = 9.95, 95% CI = 1.50-65.86), feeding Holstein calves <2.84 L of milk or replacer per day (OR = 7.16, 95% CI = 1.23-41.68), and lagoon water used for flushing manure under hutches compared with no flush (OR = 12.06, 95% CI = 1.93-75.47). Providing extra shade over hutches (OR = 0.08; 95% CI = 0.02-0.37), feeding calves at least 90% saleable milk (OR = 0.27, 95% CI = 0.13-0.54) or pasteurized milk (OR = 0.10; 95% CI = 0.03-0.36), and feeding >5.68 L of milk or replacer per day to Jersey calves (OR = 0.04; 95% CI = 0.01-0.28) were negatively associated with BRD. Our study identified management practices on California dairies with variability and that may contribute to differences in BRD prevalence, which will be incorporated into a risk-assessment tool to control and prevent BRD in preweaned dairy calves.

Comparison of gene editing versus conventional breeding to introgress the POLLED allele into the US dairy cattle population.

Disbudding and dehorning are commonly used cattle management practices to protect animals and humans from injury. They are unpleasant, costly processes subject to increased public scrutiny as an animal welfare issue. Horns are a recessively inherited trait, so one option to eliminate dehorning is to breed for polled (hornlessness). However, due to the low genetic merit and scarcity of polled dairy sires, this approach has not been widely adopted. In March 2018, only 3 Holstein and 0 Jersey active homozygous polled sires were registered with the National Association of Animal Breeders. Alternatively, gene editing to produce high-genetic-merit polled sires has been proposed. To further explore this concept, introgression of the POLLED allele into both the US Holstein and Jersey cattle populations via conventional breeding or gene editing (top 1% of bulls/year) was simulated for 3 polled mating schemes and compared with baseline selection on lifetime net merit (NM$) alone, over the course of 20 yr. Scenarios were replicated 10 times and the changes in HORNED allele frequency, inbreeding, genetic gain (NM$), and number of unique sires used were calculated. Gene editing decreased the frequency of the HORNED allele to <0.1 after 20 yr, which was as fast or faster than conventional breeding for both breeds. In the mating scheme that required the use of only existing homozygous polled sires, inbreeding reached 17% (Holstein) and 14% (Jersey), compared with less than 7% in the baseline scenarios. However, gene editing in the same mating scheme resulted in significantly less inbreeding, 9% (Holstein) and 8% (Jersey). Also, gene editing resulted in significantly higher NM$ after 20 yr compared with conventional breeding for both breeds. Additionally, the gene editing scenarios of both breeds used a significantly greater number of unique sires compared with either the conventional breeding or baseline scenarios. Overall, our simulations show that, given the current genetic merit of horned and polled dairy sires, the use of conventional breeding methods to decrease the frequency of the HORNED allele will increase inbreeding and slow genetic improvement. Furthermore, this study demonstrates how gene editing could be used to rapidly decrease the frequency of the HORNED allele in US dairy cattle populations while maintaining the rate of genetic gain, constraining inbreeding to acceptable levels, and simultaneously addressing an emerging animal welfare concern.

Regional management practices and prevalence of bovine respiratory disease in California's preweaned dairy calves.

The objective of this cross-sectional study was to estimate the prevalence of bovine respiratory disease (BRD) in California preweaned dairy calves and identify management practices that are associated with BRD. A convenience sample of 100 dairies in the 3 distinct dairy regions of California was surveyed. Regions evaluated were Northern California (NCA), northern San Joaquin Valley (NSJV), and greater Southern California (GSCA). A questionnaire on calf management practices and demographic information was administered via in-person interviews at each dairy and a random sample of preweaned calves was evaluated using the California BRD scoring system on the same day. Prevalence of BRD varied between the 3 dairy regions: 9.30% in NCA, 4.51% in NSJV, and 7.35% in GSCA. Breed was not associated with BRD prevalence at the statewide level, but differences in prevalence were observed between breeds across the regions with a higher prevalence in NCA for Jerseys and in GSCA for Holsteins, compared with NSJV. Prevalence of BRD was not different between organic and conventional dairies. Colostrum management practices, including heat treatment and feeding colostrum from multiparous cows, varied by region and were associated with lower BRD prevalence. Calves housed in group pens, a practice observed primarily in NCA, had a higher BRD prevalence than those in individual housing. Feeding salable milk was also more common in NCA and was associated with lower BRD prevalence. Ground and road surfaces adjacent to the calf raising area were also variable by region, and paved surfaces were associated with lower BRD prevalence. Management practices associated with BRD varied across the state and may be addressed to inform the adoption and implementation of potentially protective management decisions on California dairies and other regions with similar dairy systems.

The contribution of transgenic and genome-edited animals to agricultural and industrial applications.

For centuries, animal breeders have intentionally selected the parents of the next generation based on their concept of the 'ideal' animal. The dramatic differences seen in the appearance and productivity of different breeds show the power of such selection on DNA sequence variations. Unfortunately, the global furore over the use of modern biotechnologies to introduce desired genetic variations into animal breeding programmes, and the regulatory uncertainty associated with these recombinant DNA techniques, has effectively precluded the use of these technologies in food animal breeding programmes. Ironically, many of these early transgenic animal applications targeted traits that favoured sustainability, such as disease resistance and decreased environmental impact. As a consequence, transgenic animals have had little opportunity to affect global agriculture, and only a handful of pharmaceutical applications have been successfully commercialised. New developments in genome editing hold considerable promise for targeting traits that improve both animal health and welfare, and frequently involve no introduction of DNA sequences from other species. Nonetheless, future global regulation and public acceptance of such methods remain uncertain. Proposals to regulate genome-edited animals based solely on the process used to influence DNA sequence variations (i.e. intentional genome editing) and any potential attendant risks, with no counterbalancing consideration of the ensuing benefits or risks associated with conventional selection programmes, will potentially forestall the use of genome editing in animal breeding programmes. No activity can survive a risk-only evaluation, and there are considerable opportunity costs associated with preventing breeders' access to safe technologies in order to achieve genetic improvements in livestock populations.

Pendant des siècles, les éleveurs ont exercé une sélection des reproducteurs au sein de leurs troupeaux afin de donner naissance à de nouvelles générations d'animaux correspondant à leur conception de l'animal d'élevage « idéal ¼. Les différences d'aspect et de productivité constatées entre les différentes races démontrent l'importance des effets de cette sélection sur les mutations des séquences d'ADN. Malheureusement, l'indignation planétaire suscitée par le recours aux biotechnologies modernes pour introduire des traits d'amélioration génétique chez les animaux d'élevage et les incertitudes sur la réglementation applicable aux techniques de l'ADN recombiné ont eu pour effet d'exclure l'utilisation de ces technologies dans les programmes d'élevage d'animaux destinés à la consommation humaine. L'ironie de la chose est que la plupart des premières applications recourant aux animaux transgéniques visaient à introduire des traits favorisant un élevage durable, par exemple des traits induisant une résistance contre certaines maladies ou permettant de diminuer l'impact environnemental des élevages. En conséquence, les conditions n'étaient guère réunies pour que les animaux transgéniques contribuent à transformer l'agriculture mondiale et seules quelques rares applications pharmaceutiques, ont pu être mises au point et commercialisées avec succès. Les récents développements de l'édition génomique ouvrent des voies extrêmement prometteuses pour cibler des traits permettant d'améliorer la santé et le bien-être des animaux, très souvent sans qu'il soit nécessaire d'introduire des séquences d'ADN provenant d'autres espèces. Néanmoins, des incertitudes subsistent sur l'évolution de la réglementation mondiale en la matière et sur l'acceptation sociale de ces méthodes à l'avenir. On peut donc s'attendre à ce que l'utilisation de l'édition génomique dans les programmes de sélection animale sera devancée par des propositions visant à la réglementer ; ces propositions ne prendront en compte que le processus induisant une modification ciblée de séquences d'ADN et les risques potentiels qui lui sont associés, sans les contrebalancer par un examen des bénéfices apportés ni des risques inhérents aux programmes de sélection classiques. Aucune activité ne peut survivre à une évaluation basée exclusivement sur les risques ; par ailleurs, les coûts d'opportunité induits par le fait d'empêcher les éleveurs d'accéder à des technologies sûres pour améliorer le patrimoine génétique des populations d'animaux d'élevage sont considérables.

Durante siglos, los criadores de animales han seleccionado intencionadamente a los progenitores de la siguiente generación en función de su concepción de animal «idóneo¼. Las espectaculares diferencias de aspecto externo y productividad que se observan entre las distintas razas ponen de manifiesto el poder de esta selección ejercida sobre las variaciones de secuencias de ADN. Lamentablemente, el clamor mundial contra el empleo de las modernas biotecnologías para introducir las variaciones genéticas deseadas en los programas de producción animal, sumado a las incertidumbres reglamentarias existentes en torno a esas técnicas de ADN recombinante, han obstaculizado el uso eficaz de estas tecnologías en programas de cría selectiva de animales destinados a la producción alimentaria. Irónicamente, muchas de esas primeras aplicaciones de animales transgénicos tenían que ver con rasgos que favorecían la sostenibilidad, como la resistencia a enfermedades o la reducción del impacto ambiental. Como consecuencia, apenas ha habido ocasión de que los animales transgénicos influyan en la agricultura mundial y solo se han comercializado con éxito un puñado de aplicaciones farmacéuticas. Las últimas novedades surgidas en la edición genómica parecen bastante prometedoras para actuar sobre rasgos que mejoren tanto la salud como el bienestar de los animales, a menudo sin que ello requiera la introducción de secuencias de ADN de otras especies. Sin embargo, sigue reinando la incertidumbre acerca del grado de aceptación pública y la futura reglamentación de tales métodos a escala mundial. Lo más probable es que las propuestas de reglamentar la cuestión de los animales obtenidos por edición genómica atendiendo únicamente al proceso empleado para obtener variantes de secuencias de ADN (esto es, la edición genómica deliberada) y a los eventuales riesgos conexos (sin tener en cuenta, en contrapartida, los consiguientes beneficios o riesgos asociados a los programas de selección convencionales) desemboquen en la imposibilidad de aplicar la edición genómica a programas de cría selectiva de animales. No hay actividad alguna que pueda superar el filtro de una evaluación basada únicamente en el riesgo, y el hecho de impedir que los criadores accedan a tecnologías seguras para lograr la mejora genética de sus poblaciones de ganado entraña importantes costos de oportunidad.

Detection of dietary DNA, protein, and glyphosate in meat, milk, and eggs.

Products such as meat, milk, and eggs from animals that have consumed genetically engineered (GE) feed are not currently subject to mandatory GE labeling requirements. Some voluntary "non-genetically modified organism" labeling has been associated with such products, indicating that the animals were not fed GE crops, as there are no commercialized GE food animals. This review summarizes the available scientific literature on the detection of dietary DNA and protein in animal products and briefly discusses the implications of mandatory GE labeling for products from animals that have consumed GE feed. Because glyphosate is used on some GE crops, the available studies on glyphosate residues in animal products are also reviewed. In GE crops, recombinant DNA (rDNA) makes up a small percentage of the plant's total DNA. The final amount of DNA in food/feed depends on many factors including the variable number and density of cells in the edible parts, the DNA-containing matrix, environmental conditions, and the specific transgenic event. Processing treatments and animals' digestive systems degrade DNA into small fragments. Available reports conclude that endogenous DNA and rDNA are processed in exactly the same way in the gastrointestinal tract and that they account for a very small proportion of food intake by weight. Small pieces of high copy number endogenous plant genes have occasionally been detected in meat and milk. Similarly sized pieces of rDNA have also been identified in meat, primarily fish, although detection is inconsistent. Dietary rDNA fragments have not been detected in chicken or quail eggs or in fresh milk from cows or goats. Collectively, studies have failed to identify full-length endogenous or rDNA transcripts or recombinant proteins in meat, milk, or eggs. Similarly, because mammals do not bioaccumulate glyphosate and it is rapidly excreted, negligible levels of glyphosate in cattle, pig and poultry meat, milk, and eggs have been reported. Despite consumer concern about the presence of trace concentrations of glyphosate that might have been applied to feed crops and/or the presence of rDNA or recombinant proteins in meat, milk, and eggs, the available data do not provide evidence to suggest that products from animals that have consumed approved GE feed crops differ in any distinguishable way from those derived from animals fed conventional feed or that products from animals fed GE feedstuffs pose novel health risks.

Rapid Communication: Variance component estimates for Charolais-sired fed cattle and relative economic impact of bovine respiratory disease.

Variance components were estimated and relative economic importance of bovine respiratory disease (BRD) was derived from 3 yr of performance, morbidity, and mortality data collected from a single beef cattle finishing operation. One thousand one hundred eighty nine of 12,812 Charolais-sired calves were treated for BRD during the finishing period. Weaning weight (WW), DMI, days to harvest (D2H), HCW, yield grade (YG), and marbling score determined by image analysis (MARB) were collected to quantify the economic impact associated with treatment for BRD. Observed means and (co)variances for carcass and production traits were used to simulate populations of 10,000 healthy and 10,000 BRD treated calves. A bio-economic model was developed to derive the economic value associated with the incidence and number of treatments for BRD during the finishing period. Carcasses from healthy calves were worth $58.28 more on average compared to calves treated at least once for BRD. Heritability estimates for BRD were 0.15 when the trait was measured as number of treatments (0 to 4), and 0.14 when measured as incidence (0 or 1). The model indicated that D2H had the lowest relative economic importance in this system, with a cost of $1.91 per head for each additional day on feed. Furthermore, the relative economic value of BRD morbidity was approximately 10.65 greater than D2H when recording the BRD phenotype as the number of BRD treatments. The economic values of HCW, WW, and DMI were 11.47, 5.15, and 3.61 times more important than D2H, respectively. This indicates BRD morbidity has the second greatest relative economic value in this system, with a one percent increase in morbidity associated with an average loss of $2.08 per head. These results indicate that BRD morbidity can have an equal or greater economic importance when compared to carcass and production traits during the finishing period. Further, this indicates the opportunity exists to increase the genetic merit for profitability during the finishing period by incorporating BRD incidence into terminal-sire selection indexes.

Survey of management practices related to bovine respiratory disease in preweaned calves on California dairies.

In the spring of 2013, a survey of California (CA) dairies was performed to characterize management practices related to bovine respiratory disease in preweaned calves, compare these practices across geographic regions of the state, and determine the principal components that explain the variability in management between herds. The questionnaire consisted of 53 questions divided into 6 sections to assess management practices affecting dairy calves from precalving to weaning. The questionnaire was mailed to 1,523 grade A licensed dairies in CA and 224 responses (14.7%) were collected. Survey response rates were similar over the 3 defined regions of CA: northern CA, northern San Joaquin Valley, and the greater southern CA region. The mean size of respondent herds was 1,423 milking cows. Most dairies reported raising preweaned calves on-site (59.7%). In 93.3% of dairies, preweaned calves were raised in some form of individual housing. Nonsaleable milk was the most frequent liquid diet fed to preweaned heifers (75.2%). Several important differences were identified between calf-raising practices in CA and practices reported in recent nationwide studies, including herd sizes, housing practices, and sources of milk fed to heifers. The differences between the CA and nationwide studies may be explained by differences in herd size. Regional differences within CA were also identified. Compared with the 2 other regions, northern CA dairies were found to have smaller herds, less Holstein cattle, calves remained with dams for longer periods of time after calving, were more likely to be certified organic dairies, and raised their own calves more often. Principal component analysis was performed and identified 11 components composed of 28 variables (questions) that explained 66.5% of the variability in the data. The identified components and questions will contribute to developing a risk assessment tool for bovine respiratory disease in preweaned dairy calves.

Prevalence and impacts of genetically engineered feedstuffs on livestock populations.

Globally, food-producing animals consume 70 to 90% of genetically engineered (GE) crop biomass. This review briefly summarizes the scientific literature on performance and health of animals consuming feed containing GE ingredients and composition of products derived from them. It also discusses the field experience of feeding GE feed sources to commercial livestock populations and summarizes the suppliers of GE and non-GE animal feed in global trade. Numerous experimental studies have consistently revealed that the performance and health of GE-fed animals are comparable with those fed isogenic non-GE crop lines. United States animal agriculture produces over 9 billion food-producing animals annually, and more than 95% of these animals consume feed containing GE ingredients. Data on livestock productivity and health were collated from publicly available sources from 1983, before the introduction of GE crops in 1996, and subsequently through 2011, a period with high levels of predominately GE animal feed. These field data sets, representing over 100 billion animals following the introduction of GE crops, did not reveal unfavorable or perturbed trends in livestock health and productivity. No study has revealed any differences in the nutritional profile of animal products derived from GE-fed animals. Because DNA and protein are normal components of the diet that are digested, there are no detectable or reliably quantifiable traces of GE components in milk, meat, and eggs following consumption of GE feed. Globally, countries that are cultivating GE corn and soy are the major livestock feed exporters. Asynchronous regulatory approvals (i.e., cultivation approvals of GE varieties in exporting countries occurring before food and feed approvals in importing countries) have resulted in trade disruptions. This is likely to be increasingly problematic in the future as there are a large number of "second generation" GE crops with altered output traits for improved livestock feed in the developmental and regulatory pipelines. Additionally, advanced techniques to affect targeted genome modifications are emerging, and it is not clear whether these will be encompassed by the current GE process-based trigger for regulatory oversight. There is a pressing need for international harmonization of both regulatory frameworks for GE crops and governance of advanced breeding techniques to prevent widespread disruptions in international trade of livestock feedstuffs in the future.

Evaluation of bull prolificacy on commercial beef cattle ranches using DNA paternity analysis.

SNP-based DNA testing was used to assign paternity to 5,052 calves conceived in natural service multisire breeding pastures from 3 commercial ranches in northern California representing 15 calf crops over 3 yr. Bulls present for 60 to 120 d at a 25:1 cow to bull ratio in both fall and spring breeding seasons in ∼40 ha or smaller fenced breeding pastures sired a highly variable (P < 0.001) number of calves (Ncalf), ranging from 0 (4.4% of bulls present in any given breeding season) to 64 calves per bull per breeding season, with an average of 18.9 ± 13.1. There was little variation in Ncalf among ranches (P = 0.90), years (P = 0.96), and seasons (P = 0.94). Bulls varied widely (P < 0.01) in the average individual 205-d adjusted weaning weight (I205) of progeny, and I205 varied between years (P < 0.01) and seasons (P < 0.01) but not ranches (P = 0.29). The pattern for cumulative total 205-d adjusted weaning weight of all progeny sired by a bull (T205) was highly correlated to Ncalf, with small differences between ranches (P = 0.35), years (P = 0.66), and seasons (P = 0.20) but large differences (P < 0.01) between bulls, ranging from an average of 676 to 8,838 kg per bull per calf crop. The peak Ncalf occurred at about 5 yr of age for bulls ranging from 2 to 11 yr of age. Weekly conception rates as assessed by date of calving varied significantly and peaked at wk 3 of the calving season. The distribution of calves born early in the calving season was disproportionately skewed toward the highly prolific bulls. The DNA paternity testing of the subset of those calves born in wk 3 of the calving season was highly predictive of overall bull prolificacy and may offer a reduced-cost DNA-based option for assessing prolificacy. Prolificacy of young bulls in their first breeding season was positively linearly related (P < 0.05) to subsequent breeding seasons, explaining about 20% of the subsequent variation. Prolificacy was also positively linearly related (P < 0.05) to scrotal circumference (SC) EPD for Angus bulls that had SC EPD Beef Improvement Federation accuracies greater than 0.05. Varying prolificacy of herd bulls has implications for the genetic composition of replacement heifers, with the genetics of those bulls siring an increased number of calves being disproportionately represented in the early-born replacement heifer pool.

Genome-wide association study of concentrations of iron and other minerals in longissimus muscle of Angus cattle.

The objective of this study was to characterize variation and identify SNP and chromosomal regions associated with mineral concentrations in LM of Angus beef cattle. Samples of LM from 2,285 Angus cattle were obtained, and concentrations of 7 minerals, including iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc, were quantified. Genomic DNA extracted from the ground beef sample used for mineral composition was genotyped with the Bovine SNP50 Infinium II BeadChip, and effects of SNP on each trait were estimated using the Bayes-Cπ module of GenSel software. Pedigree-based estimates of heritabilities and corresponding genetic variances indicate iron was the only mineral concentration that could be considered a good candidate for manipulation by genomic selection. The amount of variation that could be accounted for by SNP genotypes was concordant with pedigree-based heritabilities and varied from very low for potassium and sodium (<0.09) to medium high (0.37) for iron. Although significant chromosomal regions were identified for all minerals analyzed in this study, further study focused on iron. Seven regions on 6 chromosomes (1, 2, 7, 10, 15, and 28) were identified to have a major effect on the iron content of LM in Angus cattle. The accuracy of direct genomic values (DGV) for iron concentration was estimated using a 5-fold cross-validation strategy. The accuracy of DGV estimated as the genetic correlation between DGV and the phenotype (iron concentration) adjusted for contemporary groups was 0.59. A bivariate animal model was used to estimate genetic correlations between iron concentrations and a reduced set of economically important carcass traits: HCW, rib eye area, calculated USDA yield grade, percent KPH, and marbling score. The genetic correlations between iron concentration and HCW, percentage KPH, marbling score, and rib eye area were small (-0.19 to 0.15) and nonsignificant. Although still weak (0.22), a positive significant genetic correlation was identified between iron content and USDA calculated yield grade. Beef is a major contributor of iron and zinc in the human diet, and this study found that iron content might be effectively manipulated through marker-assisted selection programs, without compromising other carcass and palatability traits.

Genetic parameters for concentrations of minerals in longissimus muscle and their associations with palatability traits in Angus cattle.

The objective of this study was to estimate genetic parameters for concentrations of minerals in LM and to evaluate their associations with beef palatability traits. Samples of LM from 2,285 Angus cattle were obtained and fabricated into steaks for analysis of mineral concentrations and for trained sensory panel assessments. Nine minerals, including calcium, copper, iron, magnesium, manganese, phosphorus, potassium, sodium, and zinc, were quantified. Restricted maximum likelihood procedures were used to obtain estimates of variance and covariance components under a multiple-trait animal model. Estimates of heritability for mineral concentrations in LM varied from 0.01 to 0.54. Iron and sodium were highly and moderately heritable, respectively, whereas the other minerals were lowly heritable except for calcium, copper, and manganese, which exhibited no genetic variation. Strong positive genetic correlations existed between iron and zinc (0.49, P < 0.05), between magnesium and phosphorus (0.88, P < 0.05), between magnesium and sodium (0.68, P < 0.05), and between phosphorus and potassium (0.69, P < 0.05). Overall tenderness assessed by trained sensory panelists was positively associated with manganese, potassium, and sodium and negatively associated with phosphorus and zinc concentrations (P < 0.05). Juiciness assessed by trained sensory panelists was negatively associated with magnesium and positively associated with manganese and sodium concentrations (P < 0.05). Livery or metallic flavor was not associated with any of the minerals (P > 0.05). Beefy flavor was positively associated with calcium, iron, and zinc and negatively associated with sodium concentration, whereas a painty or fishy flavor was positively associated with sodium and negatively associated with calcium and potassium concentrations (P < 0.05). Beef is a major contributor of iron and zinc in the human diet, and these results demonstrate sufficient genetic variation for these traits to be improved through marker-assisted selection programs without compromising beef palatability.

Genetic parameters for carnitine, creatine, creatinine, carnosine, and anserine concentration in longissimus muscle and their association with palatability traits in Angus cattle.

The objective of this study was to estimate genetic parameters for carnitine, creatine, creatinine, carnosine, and anserine concentration in LM and to evaluate their associations with Warner-Bratzler shear force (WBSF) and beef palatability traits. Longissimus muscle samples from 2,285 Angus cattle were obtained and fabricated into steaks for analysis of carnitine, creatine, creatinine, carnosine, anserine, and other nutrients, and for trained sensory panel and WBSF assessments. Restricted maximum likelihood procedures were used to obtain estimates of variance and covariance components under a multiple-trait animal model. Estimates of heritability for carnitine, creatine, creatinine, carnosine, and anserine concentrations in LM from Angus cattle were 0.015, 0.434, 0.070, 0.383, and 0.531, respectively. Creatine, carnosine, and anserine were found to be moderately heritable, whereas almost no genetic variation was observed in carnitine and creatinine. Moderate positive genetic (0.25, P < 0.05) and phenotypic correlations (0.25, P < 0.05) were identified between carnosine and anserine. Medium negative genetic correlations were identified between creatine and both carnosine (-0.53, P < 0.05) and anserine (-0.46, P < 0.05). Beef and livery/metallic flavor were not associated with any of the 5 compounds analyzed (P > 0.10), and carnitine concentrations were not associated (P > 0.10) with any of the meat palatability traits analyzed. Carnosine was negatively associated with overall tenderness as assessed by trained sensory panelists. Similar negative associations with overall tenderness were identified for creatinine and anserine. Painty/fishy was the only flavor significantly and negatively associated with creatinine and carnosine. These results provide information regarding the concentration of these compounds, the amount of genetic variation, and evidence for negligible associations with beef palatability traits in LM of beef cattle.

The accuracies of DNA-based estimates of genetic merit derived from Angus or multibreed beef cattle training populations.

Several organizations have developed prediction models for molecular breeding values (MBV) for quantitative growth and carcass traits in beef cattle using Bovine SNP50 genotypes and phenotypic or EBV data. Molecular breeding values for Angus cattle have been developed by IGENITY, Pfizer Animal Genetics, and a collaboration between researchers from Iowa State University and the University of Missouri-Columbia (ISU/UMC). The U.S. Meat Animal Research Center (USMARC; Clay Center, NE) has also developed MBV for 16 cattle breeds using 2 multibreed populations, the Germplasm Evaluation (GPE) Program and the 2,000 Bull Project (2K(ALL)), and 2 single breed subpopulations of the 2,000 Bull Project, Angus (2K(AN)) and Hereford (2K(HH)). In this study, these MBV were assessed relative to commercial ranch EBV estimated from the progeny phenotypes of Angus bulls naturally mated in multisire breeding pastures to commercial cows: 121 for USMARC MBV, 99 for ISU/UMC MBV, and 29 for IGENITY and Pfizer MBV (selected based on number of progeny carcass records). Five traits were analyzed: weaning weight (WW), HCW, marbling score (MS), rib-eye muscle area (RE), and, for IGENITY and Pfizer only, feedlot ADG. The average accuracies of MBV across traits were 0.38 ± 0.05 for IGENITY, 0.61 ± 0.12 for Pfizer, 0.46 ± 0.12 for ISU/UMC, 0.16 ± 0.04 for GPE, 0.26 ± 0.05 for 2K(ALL), 0.24 ± 0.04 for 2K(AN), and 0.02 ± 0.12 for 2K(HH). Angus-based MBV (IGENITY, Pfizer, ISU/UMC, and 2K(AN)) explained larger proportions of genetic variance in this population than GPE, 2K(ALL), or 2K(HH) MBV for the same traits. In this data set, IGENITY, Pfizer, and ISU/UMC MBV were predictive of realized performance of progeny, and incorporation of that information into national genetic evaluations would be expected to improve EPD accuracy, particularly for young animals.

Accuracy of genomic breeding values in multibreed beef cattle populations derived from deregressed breeding values and phenotypes.

Genomic selection involves the assessment of genetic merit through prediction equations that allocate genetic variation with dense marker genotypes. It has the potential to provide accurate breeding values for selection candidates at an early age and facilitate selection for expensive or difficult to measure traits. Accurate across-breed prediction would allow genomic selection to be applied on a larger scale in the beef industry, but the limited availability of large populations for the development of prediction equations has delayed researchers from providing genomic predictions that are accurate across multiple beef breeds. In this study, the accuracy of genomic predictions for 6 growth and carcass traits were derived and evaluated using 2 multibreed beef cattle populations: 3,358 crossbred cattle of the U.S. Meat Animal Research Center Germplasm Evaluation Program (USMARC_GPE) and 1,834 high accuracy bull sires of the 2,000 Bull Project (2000_BULL) representing influential breeds in the U.S. beef cattle industry. The 2000_BULL EPD were deregressed, scaled, and weighted to adjust for between- and within-breed heterogeneous variance before use in training and validation. Molecular breeding values (MBV) trained in each multibreed population and in Angus and Hereford purebred sires of 2000_BULL were derived using the GenSel BayesCπ function (Fernando and Garrick, 2009) and cross-validated. Less than 10% of large effect loci were shared between prediction equations trained on (USMARC_GPE) relative to 2000_BULL although locus effects were moderately to highly correlated for most traits and the traits themselves were highly correlated between populations. Prediction of MBV accuracy was low and variable between populations. For growth traits, MBV accounted for up to 18% of genetic variation in a pooled, multibreed analysis and up to 28% in single breeds. For carcass traits, MBV explained up to 8% of genetic variation in a pooled, multibreed analysis and up to 42% in single breeds. Prediction equations trained in multibreed populations were more accurate for Angus and Hereford subpopulations because those were the breeds most highly represented in the training populations. Accuracies were less for prediction equations trained in a single breed due to the smaller number of records derived from a single breed in the training populations.