The National Beef Quality Audit (NBQA)-2022 serves as a benchmark of the current market cow and bull sectors of the U.S. beef industry and allows comparison to previous audits as a method of monitoring industry progress. From September 2021 through May 2022, post-slaughter hide-on animals (n = 6,674), carcasses (n = 5,746), and offal items (heads and tongues: n = 7,282; lungs and hearts: n = 6,708; viscera, kidneys, and livers: n = 6,358) were surveyed at 20 commercial beef processing facilities across the United States. There were 37.8% of cattle with no visible mud contamination. Native (unbranded) hides were observed in 88.3% of cattle. Carcass bruising was observed on 66.7% of cow carcasses and 46.4% of bull carcasses, similar to percentages observed in the 2007 and 2016 audits. Nearly all cattle were free of knots (98.2%) or injection-site lesions (97.1%). Harvest-floor assessments found that 45.0% of livers, 22.2% of viscera, 19.3% of kidneys, 46.6% of lungs, 19.9% of hearts, 11.2% of heads, and 6.4% of tongues were condemned. The leading cause of condemnation for these offal items was contamination, aside from livers with the majority resulting in condemnation from the presence of an abscess. Of the cows surveyed, 25.4% carried a fetus, an 8% increase compared to those observed in 2016, and a 14.8% increase compared to cows surveyed in 2007. Findings from the NBQA-2022 identified areas of improvement and areas that required continued research and producer education to improve market cow and bull welfare, by-product quality, and offal value. This aspect of the National Beef Quality Audit-2022 focused on hide characteristics, defects visible on the carcass surface, and offal condemnations related to animal welfare and the value of beef and dairy market cows and bulls. This comprehensive survey provides detailed findings related to the types of defects observed on hides, the quantity and severity of bruises, visible injection-site presence, offal condemnations, and pregnancy status of cows at harvest. This aspect of the National Beef Quality Audit-2022 focused on hide characteristics, defects visible on the carcass surface, and offal condemnations related to animal welfare and the value of beef and dairy market cows and bulls. Fewer than half (37.8%) of the cattle were free of visible mud contamination on the hide at the time of harvest. Most hides observed (88.3%) were native or unbranded, which is an increase from the rate observed in the previous audit. Hide damage due to reasons other than branding was observed in 12.3% of all cattle surveyed. Only 3.3% of all cattle surveyed had heads or limbs drag on the harvest floor or equipment due to carcass size. The percent of carcasses with bruising was similar to those reported in the 2007 and 2016 audits with cows at 66.7% and bulls at 46.4%, respectively. Nearly all cattle were free of knots (98.2%) or injection-site lesions (97.1%). Harvest-floor condemnation rates were 11.2% of heads, 6.4% of tongues, 46.6% of lungs, 19.9% of hearts, 22.2% of viscera, 19.3% of kidneys, and 45.0% of livers with heads, tongues, and kidneys being condemned at a greater rate than observed in 2016. The leading cause of condemnation for these offal items was contamination, aside from livers with the majority resulting in condemnation from the presence of an abscess. Of the cows surveyed, 25.4% carried a fetus at the time of harvest, an 8% increase compared to those observed in 2016, and a 14.8% increase from those surveyed in 2007. Improvements were observed in the instances and location of branding as well as decreased instances of knots or injection-site lesions, which can be attributed to improvements in management practices and producer education. Further improvements can be made to decrease the amount of mud present on the hide at the time of harvest, decrease instances of carcass bruising, and improve animal health to minimize offal condemnations. These improvements can benefit both animal welfare as well as carcass and offal value.

The National Beef Quality Audit (NBQA)-2022 systematically evaluated quality characteristics of cattle, carcasses, and by products generated from the fed steer and heifer sectors. This audit was conducted from September 2021 through November 2022 in 22 beef processing facilities across 11 states. Approximately 7800 live animals were evaluated exiting the trailer and in holding pens, and about 23,200 carcasses were evaluated on the harvest floor for multiple characteristics. Cattle were transported on average 245.3 km for a travel time of 2.9 h, averaging 36 animals per load. On average, trailers had 41.3 m2 of floor surface area, and cattle were housed in 3.7 compartments, allotting 1.2 m2 per animal. Cattle received 91.7% mobility score 1 (walks easily, no stiffness). Cattle identification was observed on 93.3% of the those evaluated with the following frequencies: lot visual tags (61.3%), individual visual tags (58.1%), electronic tags (29.4%), low frequency electronic tags (28.9%), and metal clip tags (11.0%). For hide color/apparent breed type, most were black hided (62.3%), followed by Holstein (12.3%), red (11.3%), tan (4.9%), yellow (2.6%), gray (2.0%), brown (2.0%), non-Holstein dairy (1.7%), and white (1.1%). Most cattle were not branded (70.5%), followed by presence of butt brands (22.4%), side brands (7.0%), and shoulder brands (1.1%). For mud/manure on the hide, 49.6% had none that was visible; when observed, the most common areas were on the legs (38.7%) and belly (31.1%). Most cattle had no horns (84.1%); for those with horns, 4.6% were <2.54 cm in length, 7.9% were 2.54 to 12.7 cm in length (7.9%), and 3.3% were > 12.7 cm in length. For bruises, 47.7% of the carcasses had none, and for those with bruises, the loin (30.0%), rib (23.7%), chuck (19.7%), and round (19.3%) were the most common locations. For dentition, 95.4% had 2 or fewer permanent incisors deemed as less than 30 mo of age. Offal/byproducts condemnations occurred for liver (28.5%), lung (20.9%), viscera (12.5%), head (4.5%), and tongue (1.8%). Compared numerically to NBQA (2016), although we observed an increased area allotted per animal, travel time to the harvest facility was longer and mobility scores were lower (less mobile) exiting the trailer. Fewer cattle were identified via ear tagging, however, there was an increase in the use of electronic tags. Numerically, the percentage of black-hided cattle increased, and percentage of Holsteins declined, branding increased, mud/manure amount found on the hide declined, cattle without horns increased, and cattle 30 mo of age or older increased. Carcasses found with 1 or more bruises increased drastically (13.4% increase compared the NBQA-2016). Metrics observed in this study provide industry updates on improvements and deficiencies found in the fed beef cattle system.

The instrument grading assessment portion of the National Beef Quality Audit (NBQA)-2022 allowed for the evaluation of beef carcass traits over a 12-mo period. One week of instrument grading data was collected each month from 6 major beef processing companies from July 2021 to June 2022 (n = 4,418,768 carcasses). The sample pool was composed of 58.0% steer carcasses and 42.0% heifer carcasses, and the breed type distribution was 98.0% native, 1.6% dairy, and 0.3% Bos indicus. Means for USDA Yield Grade (YG) and YG factors were YG, 3.26, adjusted fat thickness, 1.55 cm, HCW, 400.6 kg, ribeye area, 91.6 cm2, and KPH, 2.1%. Frequency distribution of USDA YG was YG 1 = 7.87%, YG 2 = 31.70%, YG 3 = 40.03%, YG 4 = 17.07%, and YG 5 = 3.35%. Mean marbling score was Modest16, and the distribution of USDA quality grades was Prime = 8.19%, Choice = 74.84%, Select = 15.68%, and other = 1.31%. Frequency of carcasses grading Prime on Monday (10.89%), a 3.27%-point increase compared to the Prime average for the other days of the week (7.72%), demonstrates the potential advantage of additional postmortem chilling over the weekend from Friday and/or Saturday slaughter days. Comparisons of breed type and sex class revealed differences (P < 0.05) in marbling with dairy heifers (Modest55) > native heifers (Modest31) > dairy steers (Modest12) > native steers (Modest03), and ribeye area with native steers (93.3 cm2) > native heifers (90.9 cm2) > dairy steers (81.8 cm2) > dairy heifers (80.3 cm2). Month-to-month frequency distributions in beef carcass traits revealed numerical differences in marbling, USDA quality grade distribution, HCW, and adjusted fat thicknesses. Percentage distribution of dark cutting carcasses revealed numerically higher incidences during the summer and fall seasons compared to winter and spring. Findings from the instrument grading assessment of the NBQA-2022 provide the beef industry with the most comprehensive and current beef carcass quality and yield information available.

During skeletal muscle growth, metabolic processes regulating muscle tissue exhibit remarkable adaptability. The objective of this study was to determine the involvement of mitochondria function in the shift of metabolism in porcine skeletal muscle. To alter metabolism, we utilized β-adrenergic agonists (BAA) supplementation known to increase the proportion of fast-twitch fibers. To assess the role of the mitochondria in this process, we utilized a naturally occurring mutation in domestic pigs containing a constitutively active adenosine monophosphate activated protein kinase (AMPKγ3R200Q) that results in greater tissue oxidative capacity. Mature pigs with or without AMPK mutation (control and AMPKγ3R200Q) were fed BAA (0 and 9 ppm) for 1 wk, then were euthanized and longissimus lumborum muscle samples were collected and mitochondria were isolated. Mitochondria from muscle of AMPKγ3R200Q pigs had higher (P < 0.05) oxygen consumption rates (OCR) than that of control pigs when using pyruvate/malate substrates under ADP-stimulated conditions. When provided succinate/rotenone substrates, an interaction (P < 0.05) was noted for basal respiration, where mitochondria from muscle of control pigs fed 0 ppm BAA had lower OCR compared to that of AMPKγ3R200Q pigs and that of those fed 9 ppm BAA. These data show that BAA have more pronounced effects on control pigs than AMPKγ3R200Q pigs which may be due to the inherently greater oxidative capacity of mutant pig muscle. After 1 wk of feeding BAA, there was an increase in β1-adrenergic receptor gene expression in pigs fed BAA (Treatment, P = 0.06; Interaction P = 0.08). Oxidative protein abundance increased for succinate dehydrogenase (P < 0.01) and citrate synthase (CS, P < 0.001) in AMPKγ3R200Q muscle. Additionally, CS activity in isolated mitochondria from muscle of AMPKγ3R200Q pigs was lower (P = 0.08), but whole muscle of AMPKγ3R200Q pigs had overall higher CS activity (P < 0.01). There were no differences in glycolytic enzyme protein abundances, however, there was increased lactate dehydrogenase (P < 0.001) activity in muscle of control pigs and that of muscle from pigs fed BAA (P < 0.05). Together, these data indicate that mitochondria function is altered in porcine skeletal muscle when pigs are supplemented with BAA and suggest part of the mechanism by which BAA supplementation augments muscle growth in pigs potentially lies within the regulation of β1-adrenergic receptors and changes in mitochondrial function.

The fat composition and mineral content of beef influences both its taste and nutritional value. This study seeks to understand the relationship between meat quality and the nutritional value of beef from Brangus cattle. Animals varied greatly in their levels of essential omega-6 and monounsaturated fat. Higher levels of these fatty acids have been shown to improve the flavor of beef in addition to having a beneficial impact on cholesterol levels. Brangus cattle also exhibited a unique relationship between monounsaturated fat and meat quality, where higher levels of monounsaturated fat were associated with desirable traits such as increased marbling. Regarding mineral content, iron and zinc showed weak negative correlations with monounsaturated fat and moderate positive correlations with polyunsaturated fat. This study sheds light on the complex relations between fat profiles, mineral content, and meat quality. This understanding can inform breeding and management strategies to promote the production of meat that is not only palatable but also beneficial for consumer's health.

Beef consumption is expected to increase worldwide, which necessitates the use of Bos indicus cattle that are well-adapted to harsher climates, like the tropics. Yet, beef from these cattle is considered inferior to that of Bos taurus breeds, primarily due to lowered tenderness values and reduced intramuscular fat content. However, the benefits of using Bos indicus genetics are numerous and undeniable. Herein, we explore how decreases in meat quality in these cattle may be offset by increases in livability. Further, we review the knowledge surrounding beef tenderness and explore the processes occurring during the early events of the transformation of muscle to meat that are different in this biological type and may be altered by stress. Growth rate, calpastatin activity and mitochondrial function will be discussed as they relate to tenderness. The opportunities of using Bos indicus cattle are of great interest to the beef industry worldwide, especially given the pressures for enhancing the overall sustainability and carbon footprint of this sector. Delivering a consistently high-quality product for consumers by exploiting Bos indicus genetics in a more sustainable manner will be proposed. Information on novel factors that influence the conversion of muscle to meat is explored to provide insights into opportunities for maximizing beef tenderization and maturation across all cattle. Exploring the use of Bos indicus cattle in modern production schemes, while addressing the mechanisms undergirding meat tenderness should provide the industry with a path forward for building greater demand through producing higher quality beef.

Bos indicus cattle are important to beef production in hot, humid climates, but they have a reputation for producing tougher beef with more variability. Reduced and delayed degradation of muscle proteins postmortem is a major reason underlying these tenderness challenges. Inherent muscle metabolic characteristics and processing conditions shape the early dynamics of postmortem metabolism and protein degradation after harvest, which impacts subsequent tenderization. Skeletal muscles exhibit diverse metabolic and contractile properties, and metabolic pathways are coordinated to regulate flux under variable working conditions. Considering how living muscles respond and adapt to cellular stress may enhance our understanding of muscle death and quality development. The aim of this review is to examine how muscle properties influence metabolism and cellular response in the context of early postmortem muscle to meat conversion, and specifically, their potential contribution to variation in proteolysis in Bos indicus beef.

Mitochondria function and integrity may impact postmortem metabolism and meat quality development. Adaptations in heat tolerant Brahman may persist to limit cellular stress postmortem. Our objective was to evaluate glycolysis, pH decline, and mitochondria function in longissimus lumborum (LL) from Angus and Brahman steers (N = 28) early postmortem (1 to 6 h) and after rigor (24 h). We evaluated metabolites of anaerobic glycolysis, ATP, pH, and temperature, and determined mitochondria oxygen consumption rate (OCR) in permeabilized fibers. The main effects of breed (b) and time (t) and the interaction were tested. Brahman LL contained greater ATP during the first 6 h postmortem; Brahman also tended to exhibit a slower pH decline (b x t, P = 0.07) and more rapid temperature decline (b x t, P < 0.001), but metabolites of anaerobic glycolysis were not different. Mitochondria in Brahman and Angus LL were well-coupled and respired at 1 h postmortem. However, outer membrane integrity became increasingly compromised postmortem (t, P < 0.001). Brahman tended to exhibit greater electron transport system capacity (b, P < 0.1) and had greater capacity for oxidative phosphorylation (complex I and II substrates) at 6 h compared with Angus (P < 0.001). In totality, greater ATP, slower pH decline, and enhanced mitochondria capacity indicate that Brahman possess mitochondrial properties or cellular adaptations that help protect the cell during energy stress postmortem. Slower pH and more rapid temperature decline in LL from Brahman may also help preserve mitochondria function postmortem.

Choline is a vital micronutrient. In this study, we aimed to confirm, and expand on previous findings, how choline impacts embryos from the first 7 days of development to affect postnatal phenotype. Bos indicus embryos were cultured in a choline-free medium (termed vehicle) or medium supplemented with 1.8 mM choline. Blastocyst-stage embryos were transferred into crossbred recipients. Once born, calves were evaluated at birth, 94 days, 178 days, and at weaning (average age = 239 days). Following weaning, all calves were enrolled into a feed efficiency trial before being separated by sex, with males being slaughtered at ~580 days of age. Results confirm that exposure of 1.8 mM choline chloride during the first 7 days of development alters postnatal characteristics of the resultant calves. Calves of both sexes from choline-treated embryos were consistently heavier through weaning and males had heavier testes at 3 months of age. There were sex-dependent alterations in DNA methylation in whole blood caused by choline treatment. After weaning, feed efficiency was affected by an interaction with sex, with choline calves being more efficient for females and less efficient for males. Calves from choline-treated embryos were heavier, or tended to be heavier, than calves from vehicle embryos at all observations after weaning. Carcass weight was heavier for choline calves and the cross-sectional area of the longissimus thoracis muscle was increased by choline.

The National Beef Quality Audit (NBQA)-2022 serves as a benchmark of the current market cow and bull sectors of the U.S. beef industry and allows comparison to previous audits as a method of monitoring industry progress. From September 2021 through May 2022, livestock trailers (n = 125), live animals (n = 5,430), and post-slaughter hide-on animals (n = 6,674) were surveyed at 20 commercial beef processing facilities across the U.S. Cattle were transported in a variety of trailer types for an average distance of 490.6 km and a mean transport time of 6.3 h. During transit, cattle averaged 2.3 m2 of trailer space per animal indicating sufficient space was provided according to industry guidelines. Of all trailers surveyed, 55.3% transported cattle from an auction barn to a processing facility. When surveyed, 63.6% of all truck drivers reported to be Beef Quality Assurance certified. The majority (77.0%) of cattle were sound when evaluated for mobility. Mean body condition scores (9-point scale) for beef cows and bulls were 3.8 and 4.4, respectively, whereas mean body condition scores (5-point scale) for dairy cows and bulls were 2.3 and 2.6, respectively. Of the cattle surveyed, 45.1% had no visible live animal defects, and 37.9% had only a single defect. Of defects present in cows, 64.6% were attributed to an udder problem. Full udders were observed in 47.5% of all cows. Nearly all cattle were free of visible abscesses and knots (97.9% and 98.2%, respectively). No horns were observed in 89.4% of all cattle surveyed. Beef cattle were predominantly black-hided (68.9% and 67.4% of cows and bulls, respectively). Holstein was the predominant dairy animal observed and accounted for 85.7% of the cows and 98.0% of the bulls. Only 3.1% of all animals had no form of identification. Findings from the NBQA-2022 show improvements within the industry and identify areas that require continued education and research to improve market cow and bull welfare and beef quality. This aspect of the National Beef Quality Audit-2022 focused on transportation, mobility, and live animal conditions related to animal welfare and value of beef and dairy market cows and bulls. This comprehensive survey provides detailed findings related to the types of transportation and space allocated to animals, how mobile animals were upon arrival, the types of defects observed in cattle, hide color and patterns, and the forms of animal identification used. This aspect of the National Beef Quality Audit-2022 focused on transportation, mobility, and live animal conditions related to animal welfare and value of beef and dairy market cows and bulls. Cattle were transported, on average, 490.6 km, for 6.3 h, with 2.3 m2 space per animal in a variety of trailer types. Upon unloading, most cattle walked normally (77.0%) or with minor stiffness or shortness of stride (18.0%) with only 5.0% having difficulties taking steps. Body Condition Scores indicated less condition (lower fatness) than the previous audit. The most common defects for both dairy and beef cows were udder problems, whereas, for bulls, it was swollen joints. Beef cattle were predominately black-hided (68.9% and 67.4% of cows and bulls, respectively), whereas dairy cattle were predominately Holstein (85.7% of the cows and 98.0% of the bulls). Most of the cattle (89.4%) had no horns. Only 3.1% of all cattle had no form of animal identification with most having one or more forms of identification. Improvements were observed in transportation, animal identification, and limited percentages of management-related defects. Timelier marketing of market cows and bulls assuring adequate muscling and finish may benefit both animal welfare and value.

The National Beef Quality Audit - 2022 serves as a benchmark of the current fed steer and heifer population of the U.S. beef industry and allows comparison to previous audits as a method of monitoring industry progress. In-plant cooler assessments and collections of beef carcass data took place from July 2021 to November 2022. During in-plant evaluations, 10% of 1-d production was surveyed for quality and yield indicating characteristics of fed beef carcasses (n = 9,746 beef carcasses). Distributions of sex classes among sampled carcasses were steer (65.0%) and heifer (35.0%), whereas distributions of breed type were native (87.7%), dairy (11.3%), and Bos indicus (0.9%). Mean values were observed for USDA Yield Grades (YG; 3.3), USDA Quality Grade (QG; Choice16), marbling score (Small98), ribeye area (91.0 cm2), adjusted fat thickness (1.49 cm), hot carcass weight (401.9 kg), and KPH (2.5%). Mean overall maturity was A66, with a mean lean maturity of A56 and mean skeletal maturity of A72. There were 28.1% of carcasses identified for use in a USDA-certified beef G-Schedule Program. Defects, such as dark cutting and blood splash, were observed at 1.8% and 0.5%, respectively. Distributions of USDA YG were YG 1 (8.2%), YG 2 (30.7%), YG 3 (40.2%), YG 4 (16.6%), and YG 5 (4.3%). USDA QGs were observed at 7.5% Prime, 69.2% Choice, 16.4% Select, and 6.8% other. The results of this study provide an updated look at the current grading trends of beef carcasses in the United States to drive progress in the fed beef industry. This aspect of the National Beef Quality Audit - 2022 focused on the in-plant carcass quality and yield characteristics from the fed steer and heifer population. Current USDA Quality and Yield Grade averages and distributions as well as comparisons to previous audits over the past 30 yr show trends that have evolved in important value-determining carcass traits. This phase of the National Beef Quality Audit - 2022 gathered quality- and yield-indicating characteristics of fed beef carcasses (n = 9,746 beef carcasses) representing 10% of 1-d production from 35 beef processing facilities from July 2021 to November 22, 2022. Distributions of sex classes among sampled carcasses were steer (65.0%) and heifer (35.0%), whereas distributions of breed type were native (87.7%), dairy (11.3%), and Bos indicus (0.9%). Mean values were observed for USDA YG (3.3), USDA QG (Choice16), marbling score (Small98), ribeye area (91.0 cm2), AFT (1.49 cm), HCW (401.9 kg), and KPH (2.5%). There were 28.1% of carcasses identified for use in a USDA-certified beef G-Schedule Program. Defects, such as dark cutting and blood splash, were observed at 1.8% and 0.5%, respectively. Distributions of USDA YG were YG 1 (8.2%), YG 2 (30.7%), YG 3 (40.2%), YG 4 (16.6%), and YG 5 (4.3%). USDA QGs were observed at 7.5% Prime, 69.2% Choice, 16.4% Select, and 6.8% other. Results of this study provide an updated look at the current grading trends of beef carcasses in the United States.

The quality grade system used in the United States to identify carcasses with superior eating satisfaction to consumers is based on the amount of marbling within the ribeye and the maturity of the carcass. However, the most important quality attribute for consumers is tenderness. The objective of this study was to investigate the phenotypic correlations between carcass and meat quality traits of strip loin steaks from Brangus steers, particularly the relation between the United States Department of Agriculture (USDA) quality grade and tenderness. Warner-Bratzler shear force (WBSF) values in this study averaged 5.10 ± 0.96 kg, slightly higher than the national average of 4.55 ± 1.14 kg. Average WBSF across all quality grades ranged from 4.90 to 5.27 kg with standard deviations ranging from 0.78 to 1.40 kg. In the present Brangus steer population, there was a weak negative (-0.13) but favorable correlation (P < 0.05) between marbling score and tenderness measured through WBSF. The USDA quality grade had a significant (P = 0.02) effect on WBSF. The WBSF least square means were significantly higher in the Select compared with the Choice¯, and Choiceº quality grades. The Choice⁺ and Prime quality grades were not significantly different from any quality grades regarding the WBSF. The standard quality grade did not have significantly different WBSF least square means from any other quality grade. The range of WBSF values was large, especially in the lower quality grade categories, indicating that there is considerable variation in tenderness, even within quality grade. The high level of variation in tenderness within USDA quality grades highlights the limitation of the USDA grading system to predict eating quality or tenderness.

The WNT inhibitory protein DKK1 has been shown to regulate the development of the preimplantation embryo to the blastocyst stage. In cattle, DKK1 increases the number of trophectoderm cells that are the precursor of the placenta. DKK1 can affect cells by blocking WNT signaling through its receptors KREMEN1 and KREMEN2. Here it was shown that the mRNA for KREMEN1 and KREMEN2 decline as the embryo advances in development. Nonetheless, immunoreactive KREMEN1 was identified in blastocysts using western blotting. DKK1 also decreased the amount of immunoreactive 8-catenin in blastocysts, as would be expected if DKK1 was signaling through a KREMEN-mediated pathway. Thus, it is likely that KREMEN1 functions as a receptor for DKK1 in the preimplantation bovine embryo.

Skeletal muscles exhibit considerable variation in their metabolic and contractile properties, which allows them to accomplish diverse functions in the living animal. Mitochondria content and function are key features driving oxidative capacity, and hence, the energy producing capacity of muscle fibers. In turn, these intrinsic muscle properties also influence postmortem muscle metabolism and the events that occur as living muscle becomes meat. This period is critical to the development of meat quality attributes. Yet, there is much that remains poorly understood regarding the conversion of muscle to meat. Considering that oxygen supply is removed at harvest, early efforts to understand postmortem metabolism primarily focused on glycolytic capacity. More recently, efforts have been redirected to mitochondria; not only are they critical for energy production, but mitochondria also influence calcium dynamics, apoptosis signaling, and reactive oxygen species production. These functions have been implicated in the development of meat quality attributes, including color variation, protein degradation, and tenderness. Defining the mitochondrial contributions to postmortem metabolism and meat quality is complex due to the heterogeneous nature of muscle fibers and the changes in cellular conditions (e.g., temperature, pH) that occur postmortem. Nonetheless, evidence supports that mitochondria retain at least some capacity for energy production early postmortem, indicating they are structurally intact and functional. Both inherent muscle characteristics as well as factors related to slaughter and processing appear to impact the subsequent decline in functional and structural integrity of mitochondria. Unraveling the structural and functional changes that occur in mitochondria postmortem will advance our understanding of early postmortem metabolism and meat quality development.

The objective of this study was to determine if ractopamine (RAC) impacts postmortem muscle metabolism and subsequent pork quality in Halothane (HAL) and Rendement Napole (RN) mutant pigs. All RAC fed pigs had increased (P < 0.04) L* values. HAL and RN mutants muscle had lower (P < 0.01) pH values but RAC feeding had no effect. RN mutants had higher and lower (P < 0.05) muscle pH and temperatures, respectfully at 15 min and RN mutant pigs had greater (P < 0.0001) glycogen initially but lactate levels similar to wild type (WT) pigs at 24 h. RAC lowered (P < 0.05) glycogen in RN mutants but not in HAL mutated or WT pig muscle. These data show RAC feeding changes postmortem energy metabolism but does not change pH and pork quality hallmark of two major pig gene mutations and supports our contention that ultimate meat quality traits and their biochemical drivers may be more complex than originally reasoned.

The objective of this study was to evaluate the potential of dual energy X-ray absorptiometry (DXA) to estimate the carcass composition of veal calves. A total of 15 newborn Holstein x Gyr male calves were randomly assigned to two dietary treatments: calves fed exclusively milk or fed milk + concentrate ad libitum. Calves were assigned to four slaughter groups (7, 28, 49 and 63 days of age) and after 24 h of chilling carcasses were analyzed by DXA using the enCORE software to obtain fat, lean tissue, and bone mineral content and density. Afterward, carcasses were dissected into lean, fat, and bone tissues that were ground and lyophilized to determine the carcasses chemical composition. The DXA predicted the protein (P < 0.0001, R2 = 0.7290), mineral (P = 0.002, R2 = 0.6119) contents, proportions of muscle (P < 0.001, R2 = 0.6986) and bone of veal carcasses (P < 0.0001, R2 = 0.6982), but not fat (P = 0.9557, R2 = 0.002). In conclusion, the DXA measured values were able to predict veal carcass protein, mineral contents, lean and bones amount but was not precise enough to detect the fat tissue on lean carcasses such as those from veal calves.

Bos indicus cattle are widely utilized in tropical and subtropical climates. Their heat tolerance and parasite resistance are integral for beef production in these regions; however, a reputation for excitable temperaments, slower growth, and variation in tenderness has limited their use in commercial beef production. This suggests that there is antagonism between heat tolerance and meat production traits. Meat quality characteristics are determined by the properties of skeletal muscle as well as conditions during slaughter and processing. Thus, it is possible that adaptations related to heat tolerance in the living animal affect tenderness and other meat quality attributes. Since muscle represents a large proportion of body mass, relatively small changes at the cellular level could impact overall heat production of the animal. Specifically, protein degradation and mitochondria function are aspects of organ and cellular metabolism that may help limit heat production and also have a connection to tenderness. Protein degradation postmortem is critical to structural changes that enhance tenderness whereas mitochondria may influence tenderness through their roles in energy metabolism, calcium regulation, cell death signaling, and oxidative stress. This review explores potential relationships between cellular metabolism in vivo and beef quality development in Bos indicus and Bos indicus influenced cattle.

WNT5A, one of the most abundant cell-signaling ligands expressed in the endometrium, is an important regulator of early development because it can act on the preimplantation bovine embryo to improve competence to develop to the blastocyst stage and increase the number of cells in inner cell mass. WNT signaling is important for regulation of embryonic development. The most abundant WNT gene expressed in the bovine endometrium during the preimplantation period is WNT5A. One objective was to determine whether WNT5A regulates competence of the bovine preimplantation embryo to become a blastocyst and alters the number of cells in the inner cell mass and trophectoderm. A second objective was to delineate features of the cell-signaling mechanisms involved in WNT5A actions. WNT5A caused a concentration-dependent increase in the proportion of embryos developing to the blastocyst stage and in the number of inner cell mass cells in the resultant blastocysts. A concentration of 200 ng/mL was most effective, and a higher concentration of 400 ng/mL was not stimulatory. Bovine serum albumin in culture reduced the magnitude of effects of WNT5A on development to the blastocyst stage. WNT5A affected expression of 173 genes at the morula stage; all were upregulated by WNT5A. Many of the upregulated genes were associated with cell signaling. Actions of WNT5A on development to the blastocyst stage were suppressed by a Rho-associated coiled-coil kinase (ROCK) signaling inhibitor, suggesting that WNT5A acts through Ras homology gene family member A (RhoA)/ROCK signaling. Other experiments indicated that actions of WNT5A are independent of the canonical beta-catenin signaling pathway and RAC1/c-Jun N-terminal kinase (JNK) signaling. This is the first report outlining the actions of WNT5A to alter the development of the mammalian embryo. These findings provide insights into how embryokines regulate maternal-embryonic communication.

Bos taurus indicus temperament is variable and affects beef tenderization. Our objective was to investigate temperament and performance of non-castrated Nellore and identify groups based on Longissimus lumborum (LL) pH decline as well as beef characteristics produced by those groups. We investigated 94 animals with a subset of carcasses (n = 24) selected based on LL pH at 24 h postmortem (pm) to represent two groups: resistant to pH decline (> 5.8 called pH-Res; n = 10) and normal (< 5.7 called pH-Nor; n = 14). Steaks were fabricated from the LL muscle and randomly assigned to aging (2, 7, 14, and 21 days). Sarcomere length, cooking loss, myofibrillar fragmentation index (MFI), and Warner-Bratzler shear force (WBSF) were determined. Data on temperament were investigated in a multivariate approach, while beef data were compared between groups using the analysis of variance. Rectal temperature at the beginning of the finishing phase and total weight gain were greater and related to animals in the pH-Res group (p < 0.01 and p = 0.03, respectively). Temperature and pH decline curves, sarcomere length, and cooking loss revealed that pH-Res produced beef with lower quality compared to the pH-Nor group. Results for MFI and WBSF did not show differences between groups within each time pm; however, overall steaks from pH-Res were tougher (p = 0.06). Incidence of LL pH between 5.8 and 5.9 at 24 h pm did not compromise the tenderization rate or extension; however, it affected the water holding capacity in this population of Nellore cattle.

There is a growing demand for high-quality meat across the globe. Quality attributes such as color, firmness, and texture are pivotal to consumers for making purchasing decisions. Therefore, understanding the underlying mechanisms responsible for controlling these fresh meat quality attributes is essential if the industry is going to provide consumers with high-quality uniform products that ensure a pleasant eating experience. In this chapter, we outline mechanisms undergirding the transformation of muscle to meat and those biochemical processes that regulate postmortem energy metabolism and subsequently drive ultimate fresh meat quality development. Variations in postmortem muscle metabolism, often due to stress caused by inappropriate management of animal welfare (Chapters 24 and 25Chapter 24Chapter 25), directly affect the oxidation (Chapter 6) color (Chapter 7), water-holding capacity (Chapter 10), proteolysis and maturation (Chapter 5) of meat, and thence its texture (Chapter 8) and eating pleasure. In addition to our traditional understanding of these anaerobic processes involved in this event, there is a growing appreciation for the potential role of mitochondria in postmortem metabolism, and these variations surrounding harvest are reflected in the proteomics (Chapter14) and metabolomics (Chapter 15) that form the basis of meat quality. Finally, this chapter will attempt to provide a brief overview of those management strategies and natural genetic mutations that influence the process of converting a living tissue to a highly desirable and nutritious source of protein for humans.