Showing papers by "Steven D. Shackelford published in 2022"
TL;DR: In this article , the mtDNA copy number (mtDNA CN) is heritable and easily obtained from low-pass sequencing (LPS) and mtDNA sequence reads are estimated as the ratio of mtDNA to nuDNA coverages.
Abstract: Mitochondrial DNA copy number (mtDNA CN) is heritable and easily obtained from low-pass sequencing (LPS). This study investigated the genetic correlation of mtDNA CN with growth and carcass traits in a multi-breed and crossbred beef cattle population. Blood, leucocyte, and semen samples were obtained from 2,371 animals and subjected to LPS that resulted in nuclear DNA (nuDNA) and mtDNA sequence reads. Mitochondrial DNA CN was estimated as the ratio of mtDNA to nuDNA coverages. Variant calling was performed from mtDNA, and 11 single nucleotide polymorphisms (SNP) were identified in the population. Samples were classified in taurine haplogroups. Haplogroup and mtDNA type were further classified based on the 11 segregating SNP. Growth and carcass traits were available for between 7,249 and 60,989 individuals. Associations of mtDNA CN, mtDNA haplogroups, mtDNA types, and mtDNA SNP with growth and carcass traits were estimated with univariate animal models, and genetic correlations were estimated with a bivariate animal model based on pedigree. Mitochondrial DNA CN tended (P-value ≤ 0.08) to be associated with birth weight and weaning weight. There was no association (P-value > 0.10) between mtDNA SNP, haplogroups, or types with growth and carcass traits. Genetic correlation estimates of mtDNA CN were -0.30±0.16 with birth weight, -0.31±0.16 with weaning weight, -0.15±0.14 with post-weaning gain, -0.11±0.19 with average daily dry-matter intake, -0.04±0.22 with average daily gain, -0.29±0.13 with mature cow weight, -0.11±0.13 with slaughter weight, -0.14±0.13 with carcass weight, -0.07±0.14 with carcass backfat, 0.14±0.14 with carcass marbling, and -0.06±0.14 with ribeye area. In conclusion, mtDNA CN was negatively correlated with most traits investigated, and the genetic correlation was stronger with growth traits than with carcass traits.
1 citations
TL;DR: Untargeted metabolomic investigations have suggested novel mechanisms influencing meat tenderness, lean color stability, and flavor, and future work should integrate metabolomic data with genomic, transcriptomic, and proteomic data to fully understand the biological basis of meat quality phenotypes.
Abstract:
Failure to meet consumer expectations for meat quality attributes such as color, tenderness, and flavor leads to loss of customer satisfaction and market share. Thus, much effort has been dedicated to understanding the biological variation in these traits. However, traditional approaches explained only a limited amount of biological variation. Investigations of the genome, transcriptome, proteome, and metabolome of meat animals has greatly increased the understanding of biochemical processes affecting meat quality attributes. Gene expression in response to environmental factors results in protein production. These proteins, which vary in functionality, are involved in cellular processes which produce metabolites. Thus, the proteome comprises the machinery of cellular functions and provides a great deal of information about genomic expression resulting in the phenotype. However, quantifying the metabolome provides additional information about the functionality of the machinery, and thus, even greater information about the phenotype. Untargeted metabolomic investigations have suggested novel mechanisms influencing meat tenderness, lean color stability, and flavor. Future work with targeted metabolomic approaches should focus on validating these mechanisms and studying these mechanisms under variable production systems. Moreover, future work should integrate metabolomic data with genomic, transcriptomic, and proteomic data to fully understand the biological basis of meat quality phenotypes.
TL;DR: In this paper , the effects of pork hot carcass weights, ranging from 90 to 145 kg with an average of 119 kg, on slice shear force and sensory traits of Longissimus dorsi chops when cooked to 63°C or 71°C, and assess if differences in chilling rate can explain differences in sensory traits.
Abstract: Pork hot carcass weights (HCW) have been increasing 0.6 kg per year, and if they continue to increase at this rate, are projected to reach an average weight of 118 kg by the year 2050. This projection in weight is a concern for pork packers and processors given the challenges in product quality from heavier carcasses of broiler chickens. However, previous work demonstrated that pork chops from heavier carcasses were more tender than those from lighter carcasses. Therefore, the objective was to determine the effects of pork hot carcass weights, ranging from 90 to 145 kg with an average of 119 kg, on slice shear force and sensory traits of Longissimus dorsi chops when cooked to 63°C or 71°C, and to assess if differences in chilling rate can explain differences in sensory traits. Carcasses were categorized retrospectively into fast, medium, or slow chilling-rates based on their chilling rate during the first 17 h postmortem. Loin chops cut from 95 boneless loins were cooked to either 63°C or 71°C and evaluated for slice shear force and trained sensory panel traits (tenderness, juiciness, and flavor) using two different research laboratories. Slopes of regression lines and coefficients of determination between HCW and sensory traits were calculated using the REG procedure in SAS and considered different from 0 at P ≤ 0.05. As hot carcass weight increased, chops became more tender as evidenced by a decrease in SSF (63°C ß = -0.0412, P = 0.01; 71°C ß = -0.1005, P < 0.001). Further, HCW explained 25% (R 2 = 0.2536) of the variation in chilling rate during the first 5 h of chilling and 32% (R 2 = 0.3205) of the variation in chilling rate from 5 h to 13 h postmortem. Slow and medium-rate chilling carcasses were approximately 12 kg heavier (P < 0.05) than fast chilling carcasses. Slice shear force of chops cooked to 63° and 71°C was reduced in slow and medium chilling compared with fast chilling carcasses. Carcass temperature at 5 h postmortem explained the greatest portion of variation (R 2 = 0.071) in slice shear force of chops cooked to 63°C. These results suggest that carcasses tend to chill slower as weight increases, which resulted in slight improvements in sensory traits of boneless pork chops regardless of final degree of doneness cooking temperature.
TL;DR: In this paper , the authors assess the impact of feeding systems on the change in microbial counts, color, and lipid oxidation of steaks during retail display, and on their sensory attributes.
Abstract: Consumer interest in grass-fed beef has been steadily rising due to consumer perception of its potential benefits. This interest has led to a growing demand for niche market beef, particularly in the western United States. Therefore, the objective of this study was to assess the impact of feeding systems on the change in microbial counts, color, and lipid oxidation of steaks during retail display, and on their sensory attributes. The systems included: conventional grain-fed (CON), 20 months-grass-fed (20GF), 25-months-grass-fed (25GF) and 20-months-grass-fed + 45-day-grain-fed (45GR). The results indicate that steaks in the 20GF group displayed a darker lean and fat color, and a lower oxidation state than those in the 25GF group. However, the feeding system did not have an impact on pH or objective tenderness of beef steaks. In addition, consumers and trained panelist did not detect a difference in taste or flavor between the 20GF or 25GF steaks but expressed a preference for the CON and 45GR steaks, indicating that an increased grazing period may improve the color and oxidative stability of beef, while a short supplementation with grain may improve eating quality.