Genetics and analysis of quantitative traits

Assessment of positive emotions in animals to improve their welfare.

http://www2.kobe-u.ac.jp/~toyoda/beef/BEEF/Ref/beef%20production_fat.pdf

Innovations in beef production systems that enhance the nutritional and health value of beef lipids and their relationship with meat quality.

The imprints of domestication and breed development on the genomes of livestock likely differ from those of companion animals. A deep draft sequence assembly of shotgun reads from a single Hereford female and comparative sequences sampled from six additional breeds were used to develop probes to interrogate 37,470 single-nucleotide polymorphisms (SNPs) in 497 cattle from 19 geographically and biologically diverse breeds. These data show that cattle have undergone a rapid recent decrease in effective population size from a very large ancestral population, possibly due to bottlenecks associated with domestication, selection, and breed formation. Domestication and artificial selection appear to have left detectable signatures of selection within the cattle genome, yet the current levels of diversity within breeds are at least as great as exists within humans.

/pdf/genome-wide-survey-of-snp-variation-uncovers-the-genetic-1cyjfj0k19.pdf

Genome-Wide Survey of SNP Variation Uncovers the Genetic Structure of Cattle Breeds

Consumer preference, behavior and perception about meat and meat products: an overview.

Managing meat tenderness.

Meat standards and grading: a world view.

Yearling Angus steer progeny of parents selected for low residual feed intake (RFI; high efficiency) or high RFI (low efficiency) were evaluated for feed intake, growth and differences in body composition. RFI is the difference between actual feed intake and expected feed intake based on an animal’s size and growth over a test period. Individual intakes of a high grain content ration and growth rates were recorded for 140 days and then the steers were slaughtered for measurement of body composition. All internal organs and non-carcass fat depots were removed, weighed and ground for chemical analysis. Carcasses were kept overnight in the chiller and the left half of every carcass physically dissected into retail cuts, and then into total fat, lean and bone. Carcass fat and lean were then combined and ground for chemical analysis. Steers from low RFI parents ate less (P<0.05) than the steers from high RFI parents, for similar rates of growth. Improvement in RFI was accompanied by small changes in body composition towards greater lean and less fat in the progeny of low RFI parents. Correlations of sire estimated breeding values for RFI with end of test whole body chemical protein, chemical fat and a principal component that condensed information on fat and lean body composition at the end of the test, were statistically significant. These confirmed there was a genetic association between body composition and RFI, with fatness being associated with higher RFI (i.e. lower efficiency). However, the correlations were small and suggested that less than 5% of the variation in sire RFI was explained by variation in body composition of their steer progeny. There was no evidence that a difference in the chemical composition of gain over the test explained the greater intake of metabolisable energy (ME) by the high RFI steers. The results suggest that the difference in ME intake following a single generation of divergent selection for RFI was due to metabolic processes rather than to changes in body composition.

/pdf/body-composition-and-implications-for-heat-production-of-4t9rze4fsd.pdf

Body composition and implications for heat production of Angus steer progeny of parents selected for and against residual feed intake

Relationship between consumer sensory scores and intramuscular fat percentage were examined using data from 3613 striploin (M. longissimus dorsi) samples. These samples were sensory tested, using consumer taste panels, after 14 days ageing. There were curvilinear relationships between sensory scores for tenderness, juiciness, like flavour and overall liking and intramuscular fat percentage, showing that these relationships plateaued between 15 and 17% intramuscular fat. High correlations (r > 0.86) between sensory scores meant that the individual scores were confounded. In an attempt to minimise this confounding, flavour and juiciness scores were adjusted for an independent measure of tenderness, namely peak force. There were curvilinear relationships between flavour and juiciness scores, with peak force indicating that the relationship plateaued at the higher shear forces. After adjustment for peak force, the relationships between the flavour and juiciness scores and the intramuscular fat percentage (after adjustment for peak force) also showed positive curvilinear relationships. These plateaued at the higher levels of intramuscular fat percentage (14 and 20%, for flavour and juiciness scores, respectively). These results show that if young animals are processed in a manner where myofibrillar toughness is controlled, flavour and juiciness scores for beef samples that are served as grilled steaks to Australian consumers will tend to plateau at the higher intramuscular fat percentage.

The effects of marbling on flavour and juiciness scores of cooked beef, after adjusting to a constant tenderness

The interaction between pH and temperature decline early postmortem on the calpain system and objective tenderness in electrically stimulated beef longissimus dorsi muscle.

John Mitchell Thompson

Papers

Managing meat tenderness.

Meat standards and grading: a world view.

Body composition and implications for heat production of Angus steer progeny of parents selected for and against residual feed intake

The effects of marbling on flavour and juiciness scores of cooked beef, after adjusting to a constant tenderness

The interaction between pH and temperature decline early postmortem on the calpain system and objective tenderness in electrically stimulated beef longissimus dorsi muscle.