Evidence for multiple alleles effecting muscling and fatness at the Ovine GDF8 locus

<p>Abstract</p> <p>Background</p> <p>The current investigation surveyed genetic polymorphism at the ovine <it>GDF8 </it>locus and determined its contribution to variation in muscling and fatness in sheep.</p> <p>Results</p> <p>Re-sequencing 2988 bp from a panel of 15 sires revealed a total of six SNP, none of which were located within exons of the gene. One of the identified SNP, <it>g+6723G>A</it>, is known to increase muscularity within the Belgian Texel. A genetic survey of 326 animals revealed that the mutation is near fixation within Australian Texels and present in additional breeds including White Suffolk, Poll Dorset and Lincoln. Using a resource population comprising 15 sires and 1191 half-sib progeny with genotypic data, the effect of this and other SNP was tested against a set of 50 traits describing growth, muscling, fatness, yield, meat and eating quality. The loss of function allele (<it>g+6723A</it>) showed significant effects on slaughter measurements of muscling and fatness. No effect was detected on objectively assessed meat quality however evidence was found for an association between <it>g+6723G>A</it>, decreased intramuscular fat and reduced eating quality. Haplotype analysis using flanking microsatellites was performed to search for evidence of currently unidentified mutations which might affect production traits. Four haplotypes were identified that do not carry <it>g+6723A </it>but which showed significant associations with muscling and fatness.</p> <p>Conclusion</p> <p>The finding that <it>g+6723G>A </it>is present within Australian sheep facilitated an independent evaluation into its phenotypic consequence. Testing was conducted using a separate genetic background and animals raised in different environments to the Belgian Texel in which it was first identified. The observation that the direction and size of effects for <it>g+6723A </it>is approximately consistent represented a robust validation of the effects of the mutation. Based on observed allele frequencies within breeds, selection for <it>g+6723A </it>will have the largest impact within the White Suffolk. <it>GDF8 </it>may harbour additional mutations which serve to influence economically important traits in sheep.</p

The effect of stocking density in transit on the carcass quality and welfare of slaughter pigs: 2. Results from the analysis of blood and meat samples

In a trial involving 2496 pigs, the influences on blood profile and pork quality of stocking densities ranging from 201 to 321 kg m−2 were examined. The pigs came from four different farms and were killed in 16 weekly batches. They were transported for on average 3 hr and held in lairage for 1 hr. Higher stocking densities resulted in more physical stress to the pigs based on the activity of the enzyme CPK in the blood. Stocking density did not apparently affect psychological stress and high densities did not result in dehydration. The colour, water holding capacity and instrumentally-determined texture of the pork from the carcasses of the pigs were not affected by stocking density. The experimental design and precision of the measurements were sufficient to detect numerous differences in blood profile and pork quality between pigs from the four source farms. These differences probably related to different degrees of stress-susceptibility. The results suggest that the highest stocking density examined (321 kg m−2) is unacceptable for the transport of pigs. The second highest density (281 kg m−2) produced relatively little evidence of an adverse effect on the welfare of pigs. It may be scientifically acceptable for short journeys (≤3 hr) but not for longer ones where pigs need more space to lie down

Health beneficial long chain omega-3 fatty acid levels in Australian lamb managed under extensive finishing systems

The variation in levels of the health claimable long chain omega-3 fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) plus docosahexaenoic acid (DHA, 22:6n-3) across production regions of Australia was studied in 5726 lambs over 3. years completed in 87 slaughter groups. The median level of EPA plus DHA differed dramatically between locations and sometimes between slaughters from the same location. The ratio of EPA plus DHA from lambs with high values (97.5% quantile) to lambs with low values (2.5% quantile) also differed dramatically between locations, and between slaughters from the same location. Consistency between years, at a location, was less for the high to low value ratio of EPA plus DHA than for the median value of EPA plus DHA. To consistently obtain high levels of omega-3 fatty acids in Australian lamb, there must be a focus on lamb finishing diets which are likely to need a supply of α-linolenic acid (18:3n-3), the precursor for EPA and DHA

Genetic correlations between meat quality traits and growth and carcass traits in Merino sheep

Genetic correlations between 16 meat quality and nutritional value traits and live weight at various ages, live ultrasound fat and muscle depth, carcass measures, and carcass dissection traits were estimated for Merino sheep in the Information Nucleus (IN). Genetic correlations between live weight at various ages and the carcass traits are also reported. The IN comprised 8 genetically linked flocks managed across a range of Australian sheep environments. Meat quality traits included between 1,200 and 1,300 records for progeny from over 170 sires for intramuscular fat (IMF), lean meat yield (LMY), shear force (SF5), pH, meat color, and meat nutritional value traits including iron and zinc levels and long-chain omega-3 and omega-6 polyunsaturated fatty acid levels. The genetic correlations indicated that selection of Merino sheep to either reduce fat or increase muscle using ultrasound assessments will result in little change in IMF and SF5. Myoglobin levels would tend to be reduced following selection for reduced ultrasound fat depth (0.35 ± 0.21, 0.43 ± 0.14), whereas increases in myoglobin levels would occur due to selection for increased ultrasound muscle depth (0.25 ± 0.24, 0.38 ± 0.15). Selection for increased live weight will result in favorable correlated responses in hot carcass weight (0.76 to 0.97), dressing percentage (0.13 to 0.47), and carcass muscle (0.37 to 0.95), but unfavorable responses of increases in carcass fatness (0.13 to 0.65) and possible small reductions in muscle oxidative activity (−0.13 ± 0.14 to −0.73 ± 0.33) and iron content (−0.14 ± 0.15 to −0.38 ± 0.16), and a possible deterioration of shear force from selection at later ages (0.15 ± 0.26, 0.27 ± 0.24). Negligible changes are generally expected for LMY and meat color traits following selection for increased live weight (most genetic correlations less than 0.20 in size). Selection for increased LMY would tend to result in unfavorable changes in several aspects of meat quality, including reduced IMF (−0.27 ± 0.18), meat tenderness (0.53 ± 0.26), and meat redness (−0.69 ± 0.40), as well as reduced iron levels (−0.25 ± 0.22). These genetic correlations are a first step in assisting the development of breeding values for new traits to be incorporated into genetic evaluation programs to improve meat production from Merino sheep and other dual-purpose sheep breeds