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.

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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.

The change in muscle-weight distribution from birth to maturity was examined in rams and ewes from strains of Australian Merino sheep which had been selected for high or low weaning weight, and from a randomly bred control flock. The proportional distribution of total muscle weight among nine anatomically standardized muscle groups was determined for 34 mature animals. The growth of each group was then assessed relative to the growth of the total musculature, using data from 106 immature animals. Maturity coefficients were calculated separately for pre- and post-weaning growth. Several muscle groups exhibited a diphasic growth pattern.Selection for high and low weaning weight resulted in an increase and decrease respectively in total muscle weight in mature animals, but had no effect on mature muscle-weight distribution. There were no significant strain effects on maturing patterns of muscle groups, except during the pre-weaning growth of muscles around the spinal column and those connecting the thorax to the forelimb. When compared at the same stage of maturity there was little difference between the strains in muscle-weight distribution. However, at the same weight the larger mature-size strain had a more immature pattern of muscle-weight distribution.The total muscle weight of mature rams was greater than that of mature ewes. Sex also had an effect on muscle-weight distribution at maturity for seven of the nine muscle groups. At maturity rams had a higher proportion of their muscle weight in those muscle groups associated with the neck and thorax, and a lower proportion in those associated with the limbs. Sex affected the pre-weaning maturing pattern of the muscles of the spinal column, and the post-weaning maturing pattern of all muscle groups, with the exception of those muscles associated with the distal hindlimb, the spinal column, and those attaching the thorax to the forelimb.

Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight 6. Muscle-weight distribution

Genome analysis to identify QTL and genes affecting carcass traits in Hanwoo ('Korean cattle')

Skeletal muscles from eastern grey kangaroos (Macropus giganteus) were assessed for myofibre contractile and metabolic characteristics using immunocytochemical and histological staining of serial sections. Myofibre classification using monoclonal antibodies that typically bind to mammalian slow (clone WB-MHC), fast (clone MY-32) and Types 1, 2X and 2B (clone S5 8H2) myosin heavy chains was validated using acid- and alkali-preincubated myofibrillar ATPase, NADH and α-glycerophosphate dehydrogenase stains. Myofibres were classified as Type 1 (slow oxidative), Type 2A (fast oxidative-glycolytic), Type 2X/2B (fast glycolytic) or intermediate or transitional myofibre Types 2C (Type 1–Type 2A intermediate) and 2AX/B (Type 2A–Type 2X/2B intermediate). The Type 2 (fast) antibody (clone MY-32) used in the present study did not bind to a subset of fast myofibres in any of the eight kangaroo muscles investigated. These myofibres were identified as Type 2A using clone S5 8H2 and on the basis of the histochemical staining profile. Hence, a simplified immunostaining system using only clones WB-MHC (anti-Type 1) and MY-32 (anti-Type 2X/2B) allowed five myofibre types to be identified based on the staining pattern and intensity of staining for the two antibodies. It is concluded that the myofibres of muscles from kangaroos can be quickly classified into five types using two commercially available antibodies. This method is directly applicable for routine investigations into the myofibre properties of commercially important muscles from the kangaroo musculature and, when combined with enzymatic assays for oxidative and glycolytic activity, will allow for a better understanding of factors influencing the quality of meat from kangaroos.

Eastern grey kangaroo (Macropus giganteus) myofibres. 1. A simplified classification method using two commercially available antibodies.

Improvements in production and qualiry can occur, without the need for increased inputs, through the use of Compensatory growth or by reducing the maintenance requirements during growth and at maturity. A series of studies were used to examine the changes in body composition that occurred during weight loss and realimentation in immature and mature sheep. The effect of variations in body composition, induced through manipulation of nutrition, on estimate; for equilibrium maintenance efficiency of mature sheep was examined. Statistical methods developed, tested for seasonal cycles in body composition in an attempt to det\~rmine~he impact that any endogenous pattern in tissue deposition has on estimates of efficiencie~;for growth and maintenance. Maintenance efficiency Differences in maintenance reqUirement~; between genotypes selected for variation in body composition when compared at the same weight were shown to be a function of response of body components to selection. No reduction in the true energetic costs of maintaining the various body tissues was achie\ ed through selection for changes in body fatness. These results indicate that differences in body composition do contribute to variation in maintenance requirements observed both within and between breeds. Improvements in biological efficiency gained by selection for proportionally fatter animals are diminished by a proportional reduction in the final product (muscle mass) from the dam/offspring unit. Sex differences in maintenance requirements at the same weight are not explained by differences in body composition. The implications of preVIOUS nutritional history on estimates for equilibrium maintenance efficiency were examined in mature sheep.. Utilisation of CT-scanning allowed estimates for maintenance efficiency to be adjusted for differences in retained energy over the test period. A period of severe weight loss resulted in higher maintenance requirements during a realimentation period relative to that recorded prior to the weight loss period, when expressed per kilogram of body weight. In contrast, less severe

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Changes in Body composition and Maintenance efficiency during periods of restricted and maintenance feeding in immature and mature sheep

This paper investigated whether a single Hormonal Growth Promotant (HGP) adjustment in the Meat Standards Australia (MSA) beef grading model adequately predicted consumer eating quality of beef from cattle treated with different HGP formulations. This paper used consumer sensory data from two experiments. In experiment one, a total of 300 steers were allocated to three treatments; control (CON-100-F), 100 day oestradiol only HGP (OES-100-F), or a combination of trenbolone acetate and oestradiol HGP (TBA+OES-100-F) and finished in a feedlot for 73 days. In experiment two, a total of 200 steers were allocated either control or 400 day oestradiol only HGP treatments and finished on pasture for 389 days. Steers were slaughtered by finishing regime and carcass traits recorded. The anterior and posterior portions of the m. longissimus lumborum (LL-A and LL-P, respectively) and m. gluteus medius (GM) were collected and aged for five or 35 days. Grilled meat samples were scored for tenderness, juiciness, liking of flavour and overall acceptability using untrained consumers. Sensory scores were weighted by 0.3. 0.1, 0.3 and 0.3, respectively and summed to calculate a meat quality (MQ4) score. Residual MQ4 scores were calculated (observed MQ4 minus the predicted MQ4 score). The MSA model accounts for varied impacts of different HGPs on eating quality through a single HGP adjustment, and indirect impacts on carcass traits. For the majority of the HGP treatment samples, the residual MQ4 scores were not different to zero (5/18), or were positive i.e. the MSA model under-predicted these samples (11/18). Under-prediction was predominately for 35 day aged (7/9) and GM HGP treatment samples (6/6) and was considered low, with the majority less than ±5 MQ4 units. Under-prediction could be considered as advantageous through providing an additional safeguard to protect the interests of the consumers, rather than if the model had over-predicted and resulted in a more negative eating quality experience than expected. Some over-prediction was observed in the CON-100-F and TBA+OES-100-F treatment samples, which may be due to factors such as genetic variation and/or production environment. Minimal bias was observed when residual MQ4 was regressed against predicted MQ4 for the range of feeding regimes, muscles, ageing periods and treatment groups. This study showed that a single HGP adjustment in the MSA beef grading model, combined with the indirect effects of the different HGP formulations on carcass traits, provided a reasonable prediction of meat eating quality for different HGP formulations.

John Mitchell Thompson

Papers

Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight 6. Muscle-weight distribution

Genome analysis to identify QTL and genes affecting carcass traits in Hanwoo ('Korean cattle')

Eastern grey kangaroo (Macropus giganteus) myofibres. 1. A simplified classification method using two commercially available antibodies.

Changes in Body composition and Maintenance efficiency during periods of restricted and maintenance feeding in immature and mature sheep

Does a single adjustment in the meat standards Australia beef grading model cater for different hormonal growth promotant formulations