Location: Meat Safety and Quality
2022 Annual Report
Objectives
Objective 1: Develop strategies to manage and improve variation in meat quality, composition, and healthfulness traits.
Sub-objective 1.A: Identification of genetic markers for myoglobin content of pork muscles to increase redness of pork products.
Sub-objective 1.B: Estimate effects of three maternal lines and two mating systems on lamb carcass merit.
Sub-objective 1.C: Genomic control of dark cutting and other beef quality traits.
Sub-objective 1.D: Genomic control of pork fat quality and fatty acid profile.
Sub-objective 1.E: Identify and validate novel single-nucleotide polymorphisms (SNP) for beef lean color stability.
Sub-objective 1.F: Determine the effect of VQG' pork loin grading camera tenderness class on optimal aging time of boneless pork loins.
Sub-objective 1.G: Impact of backgrounding strategies on beef carcass merit.
Sub-objective 1.H: To determine the effects of replacing tylosin phosphate (Tylan®) with an essential oil containing limonene in the diet of finishing beef cattle on carcass characteristics.
Objective 2: Characterize biological variation in meat quality, composition, and healthfulness traits.
Sub-objective 2.A: Determine the impact of sire line on the meat quality defect characterized by a band of very pale, almost white, muscle tissue on the superficial portion of ham muscles (halo).
Sub-objective 2.B: Characterize the effect of muscle metabolic efficiency, particularly in mitochondrial efficiency on beef tenderness and lean color stability attributes across varying pH classes in beef carcasses exhibiting normal lean color.
Sub-objective 2.C: Determine if there are metabolomic differences between tender and tough beef across postmortem aging times.
Sub-objective 2.D: Identification of differentially expressed proteins in beef longissimus steaks classified as tender with stable lean color during simulated retail display compared to steaks classified as tough with labile lean color during simulated retail display.
Sub-objective 2.E: Develop technologies for measuring and predicting important traits relating to meat product quality and consistency and the biological mechanisms that control these traits.
Approach
The overall goal of this project is to develop approaches to improve quality and healthfulness while reducing the variation in meat products. This will be accomplished by providing the red meat industries with the information and tools necessary to facilitate equitable valuation of carcasses and meat, improve the quality and consistency of meat, and optimize carcass and meat composition of beef, pork, and lamb. The two objectives of this project address needs in improving consistency of quality, composition, and healthfulness of red meat products by developing strategies and instrumentation to manage and improve these traits using basic and applied research approaches. Genetic and genomic strategies will be developed that may be combined with animal and meat management strategies to optimize quality and composition traits. Research will be conducted using proteomics and other biochemical tools to characterize variation in quality and composition as well as to evaluate and facilitate implementation of instrumentation for measuring or predicting value determining traits such as carcass grade traits, tenderness, lean color stability, and fat quality.
Progress Report
This is the final report for 3040-31430-006-000D “Strategies to Optimize Meat Quality and Composition of Red Meat Animals” which was replaced with project 3040-31430-007-000D “Approaches for Improving and Measuring Red Meat Quality and Composition”.
Objective 1. Beef lean color is a primary determinant of consumer purchasing decisions. Cuts produced from the carcasses of some animals do not possess sufficient color life for commercial case-ready programs. Genome analysis of lean color stability on steaks from a large population of cattle representing the 18 most prevalent breeds in the U.S. beef herd identified 417 genes associated with variation in lean color stability. These genes indicate the importance of energy metabolism, which suggest mechanisms requiring further investigation. Follow-up efforts include additional DNA sequencing to identify the specific gene alterations with the greatest effects on color as well as investigating protein and metabolite profiles to further understand the role of these genes in regulating lean color stability.
Dark cutting beef results in an annual loss of potential revenue for the U.S. beef industry in excess of $70 million. Dark cutting beef has long been understood to be caused by the animal having a negative energy balance before slaughter, which results in depletion of the animal’s muscle energy stores. However, it was not understood why a group of cattle could all be exposed to identical conditions resulting in some carcasses exhibiting the dark-cutting condition and others exhibiting “normal”, bright, cherry-red lean color. A naturally-occurring genetic mutation in cattle decreases the susceptibility of cattle to the dark-cutting condition. The mutation discovered in this work helps to account for much of the unexplained variation in susceptibility to dark cutting. The normal sequence is highly-conserved across all mammals and increases susceptibility to the dark-cutting condition. Thus, the mutant, which appears to have originated in British breeds of cattle, confers the desired bright, cherry-red lean. The frequency of the favorable allele ranges from 0 to 0.7 in beef breeds and the frequency of the favorable allele is very low in Holstein steers, which are the primary source of dairy beef. Selection for the favorable allele in this gene should significantly reduce the costly occurrence of dark-cutting beef.
The medical community has long been critical of the fatty acid profile of beef products. Thus, there have been countless attempts to modify the fatty acid profile of beef products. However, saturation of fatty acids by rumen microorganisms makes it difficult to modify the fatty acid profile of beef products with changes to cattle diets. Naturally-occurring genetic variation in cattle affect the level of saturated fat in beef. The favorable form of this gene, results in a lower proportion of saturated fat and a higher proportion of monounsaturated fat. It is likely that marketing of products with the favorable gene form will increase beef consumption by consumers concerned about saturated fat intake, while potentially increasing the healthfulness of beef.
Sheep production is very labor intensive, and producers need lower cost, lower input production systems to be profitable. Three breed-types of ewes (Katahdin, Polypay, and Composite IV) in two breeding systems: a purebred system, in which each maternal line was mated with rams of the same genetic line, and a terminal mating system in which ewes were mated with Texel rams were evaluated. The increased number of lambs born to Composite IV ewes relative to Polypay and Katahdin, resulted in more pounds of saleable meat produced per ewe exposed, despite the reduction in growth rate and leanness of Composite IV lambs. Use of Texel rams in a terminal mating system improved growth rate and pounds of lean meat of lambs from Composite IV ewes. Thus, Composite IV ewes bred to meat-type rams can be used effectively by producers in a low-input production system with reduced labor costs and improved profitability.
Historical trends indicate the size of U.S. hogs is likely to continue to increase. Collaboration with the University of Illinois and Kansas State University determined the effect of increased carcass weights on pork quality. The heaviest group of carcasses weighed 36% more than the industry average and represent the expected average carcass weight by 2050. The increased carcass weight resulted in slower rates of loin muscle chilling. This resulted in loin chops that retained more moisture during cooking and were more tender and juicy. Carcass weight had minimal effect on other pork quality traits including lean color and marbling. These results show that continued improvement in production efficiency through selection for growth in pigs resulting in heavier market weights will improve eating quality of pork chops.
Objective 2. Beef flavor is the most important factor in determining consumer eating satisfaction of beef products. The role of beef processing strategies and cookery in flavor development has been the subject of extensive research. However, little attention has been paid to the role of inherent animal-to-animal variation in muscle metabolism in the development of beef flavor. Variation in muscle metabolites is associated with both positive and negative flavor attributes in beef strip loin steaks. These findings provide greater understanding of the mechanisms responsible for variation in beef flavor as well as selection strategies to improve overall beef flavor and consistency, which will increase consumer satisfaction and repeat purchases for beef. These results may add millions of dollars in revenue to the U.S. beef industry through increased demand for high quality beef products.
The newest (7L) version of the VBG2000 grading camera was developed to more clearly quantify errors in operation of the grading camera during online application. Beef packing companies are anxious to adopt the 7L camera to improve the ability of plant employees in both camera operation and the proper presentation of the beef carcass for grading camera operation. At the request of USDA-Agricultural Marketing Service (AMS), the new 7L camera was compared to the currently approved VBG2000-LED grading camera and demonstrated to provide equivalent results with enhanced capacity to identify operational errors. The 7L camera has since been approved by AMS, and will improve employee training, will result in more accurate grade data, and is being adopted by all large North American beef packing plants for evaluation of marbling score and yield grade traits for USDA grading and certification activities.
Human sensory evaluation for meat quality traits, such as tenderness, is the gold standard but is time consuming and expensive to conduct. Alternatively, shear force tests of cooked meat can be used to provide an accurate measure of meat tenderness. Historically, shear force tests were conducted parallel to the meat fiber direction, but for some meat cuts this is technically very challenging. To overcome this limitation, a method was developed and evaluated to conduct shear force perpendicular to the cut surface of the steak rather than parallel to the meat fiber direction. Shearing perpendicular to the cut surface of the steak provided similar mean shear force values and improved repeatability of the measurement. This new research tool will improve the accuracy of meat tenderness measurement and will provide an additional tool for the meat industries to evaluate and market meat products at higher value and with improved overall consumer eating satisfaction.
Cured ham color is of great importance in meeting consumer expectations for ham products. Recently the pork industry identified a color defect in ham muscles that caused a high level of consumer dissatisfaction with cured ham products. Collaboration with pork processors determined the color defect occurs in almost all pigs regardless of production system or management practices. Sire lines differed significantly in traits that affect muscle color, thus, genetic selection could be utilized to minimize or eliminate the occurrence of the ham color defect and increase consumer satisfaction and the value of ham products.
Tenderness is a primary driver of customer satisfaction of beef products. However, despite substantial research efforts, a large portion of the variation in tenderness cannot be explained by known factors influencing tenderness. In collaboration with scientists from Colorado State University, we characterized all compounds found in beef related to tenderness and identified more than 2,500 compounds that were associated with differences in tenderness. Of these, 28 were known compounds and the three most related to tenderness differences could be used to predict loin steak tenderness and facilitate marketing of a guaranteed tender brand of beef, which will improve consumer demand for beef products.
The recent development of tenderness claims certification standards has given the beef industry added impetus to implement a tenderness-based marketing system. To effectively execute a tenderness-based marketing strategy, retailers need to be able to market all loin and rib cuts from a qualifying carcass as certified tender. Yet, at present, the certification protocols do not favor inclusion of top sirloins, which represent a substantial retail meat cut feature. Tenderness classes based on the VBG2000 beef grading camera allowed for identification of carcasses with more favorable top sirloin tenderness. This work showed that tenderness testing with the beef grading camera in combination with refrigerated aging for 28 days can be used to produce consistently tender top sirloin steaks that qualify for a guaranteed tender marketing claim.
Accomplishments
1. Validated biomarkers for beef quality. A majority of the variation in lean color, tenderness, and flavor cannot be explained. Recently, novel biomarkers associated with intermediates of muscle metabolism and cellular stress response have been identified that explain much more of the variation in meat quality traits than previously possible. However, these needed to be validated in more comprehensive studies. USDA-ARS scientists at Clay Center, Nebraska, verified that these candidate biomarkers are predictive of variation in beef tenderness, flavor, and color and explain variation in these traits not previously accounted for. Implementation of these findings provide greater understanding of the mechanisms responsible for variation in meat quality and lead to selection strategies to improve quality, increase consumer satisfaction, and repeat purchases of beef. These outcomes will add millions of dollars in revenue to the U.S. beef industry through increased demand for high quality beef products.
2. Determined mechanisms for high pH, dark colored beef. High pH beef is heavily discounted because they have dark color and are undesirable to consumers. Although occurrence is seasonal, on average 3% of beef is dark enough to be discounted. Previous research determined that muscles with high pH had increased mitochondrial content and less efficient mitochondrial function than normal pH muscles. USDA-ARS scientists at Clay Center, Nebraska, determined mitochondrial abundance and function across the range of meat pH observed in the industry to provide insight into the role of mitochondrial function in determining muscle pH. These results provide clarity in some of these relationships among metabolic function and meat quality traits, such as more completely explaining animal-to-animal variation in meat tenderness, flavor, and lean color. These results will lead to strategies to improve quality, increase consumer satisfaction, and repeat purchases of beef by decreasing the occurence of undesirable high pH beef. These outcomes will add millions of dollars in revenue to the U.S. beef industry through increased consumer satisfaction and demand for high quality beef products.
3. Confirming accuracy of beef grades. In the U.S., beef quality grading is based on the visible flecks of fat in the rib/loin muscle (marbling score) determined by an instrument grading camera. Consumers and meat marketers sometimes complain about some steaks appearing to have less marbling than they expect for a specific quality grade program. There is significant biological variation in marbling score among carcass sides and among steaks within the ribeye and loin that has never been quantified. USDA-ARS scientists at Clay Center, Nebraska, determined the level of variation in beef grading camera marbling score and ribeye fat among ribeye and loin steaks from both sides of beef carcasses. There are significant differences among ribeye and loin steaks in both instrument marbling score and fat content. These data explain observed discrepancies in steak marbling level and quality grade category and provide scientific data to alleviate concerns of inaccurate grading or deceptive marketing.
Review Publications
Warner, R.D., Wheeler, T.L., Ha, M., Li, X., Bekhit, A., Morton, J., Vaskoska, R., Dunshea, F.R., Liu, R., Purslow, P., Zhang, W. 2021. Meat tenderness: Advances in biology, biochemistry, molecular mechanisms and new technologies. Meat Science. 185. Article 108657. https://doi.org/10.1016/j.meatsci.2021.108657.
Nonneman, D.J., Keel-Mercer, B.N., Lindholm-Perry, A.K., Rohrer, G.A., Wheeler, T.L., Shackelford, S.D., King, D.A. 2022. Transcriptomic analysis for pork color – The ham halo effect in biceps femoris. Meat and Muscle Biology. 6(1):1-8. Article 13050. https://doi.org/10.22175/mmb.13050.
Artegoitia, V.M., Newman, J.W., Foote, A.P., Shackelford, S.D., King, D.A., Wheeler, T.L., Lewis, R.M., Freetly, H.C. 2022. Non-invasive metabolomics biomarkers of production efficiency and beef carcass quality traits. Scientific Reports. 12. Article 231. https://doi.org/10.1038/s41598-021-04049-2.
