Flight speed and agitation in weaned lambs: Genetic and non-genetic effects and relationships with carcass quality

Tryptophan improves antioxidant capability and meat quality by reducing responses to stress in nervous Hu sheep

In sheep, the effect of tryptophan (Trp) on behavioural traits that are associated with temperament and any effects on production traits is unknown. The hypothesis of this study is that the supplementation of Trp would improve temperament by enhancing serotonin production, which is beneficial to meat production subsequently in sheep. Twelve ewes that had the lowest and 12 ewes that had the highest behavioural responses to human contact were selected into the calm and the nervous groups respectively. Then, the ewes from each group were equally assigned into two treatments that were treated with the basal diet and the diet with extra 90 mg/kg/d Trp for 30 d. The temperament traits, the growth performance, the biochemicals that are related to health the slaughter performance and meat quality were measured at the end of feeding experiment. The findings in this study suggested the Hu sheep with calm temperament would experience less stress during production, resulting in less oxidative stress, better growth performance, slaughter traits and carcass traits, compared to the nervous sheep. Meanwhile, the dietary supplementation of Trp reduced stress responses by enhancing production of 5-HT in sheep from the nervous group which is beneficial to improve the production traits that mentioned above.

Microbial spoilage mechanisms of vacuum-packed lamb meat: A review

Lamb meat is an important export commodity, however chilled vacuum-packed (VP) lamb has approximately half the shelf-life of beef under the same storage conditions. This makes the industry more vulnerable to financial losses due to long shipping times and unexpected spoilage. Understanding the spoilage mechanisms of chilled VP lamb in relation to VP beef is important for developing effective strategies to extend the shelf-life of lamb. This review has discussed various key factors (i.e., pH, fat, and presence of bone) that have effects on microbial spoilage of VP lamb contributing to its shorter shelf-life relative to VP beef. A range of bacterial organisms and their metabolisms in relevance to lamb spoilage are also discussed. The data gap in the literature regarding the potential mechanisms of spoilage in VP red meat is highlighted. This review has provided the current understanding of key factors affecting the shelf-life of VP lamb relative to VP beef. It has also identified key areas of research to further understand the spoilage mechanisms of VP lamb. These include investigating the potential influence of fat and bone (including bone marrow) on the shelf-life, as well as assessing changes in the meat metabolome as the spoilage microbial community is developing using an integrated approach. Such new knowledge would aid the development of effective approaches to extend the shelf-life of VP lamb.

Calm Hu ram lambs assigned by temperament classification are healthier and have better meat quality than nervous Hu ram lambs

The objective of this study was to evaluate the effects of temperament classification (assessed using an arena test) on health and productivity of Hu ram lambs. In experiment one, eight ram lambs classified as calm and eight classified as nervous (selected from 100 ram lambs) were fed individually for 60-days to compare food intake, food digestibility, weight gain, and biochemical indices of health. In experiment two, nine ram lambs classified as calm and nine classified as nervous (selected from 150 ram lambs) were fed in a group and slaughter traits, meat quality, and muscle histology were compared. Calm lambs had higher dry matter digestibility, lower serum TNF-α, higher total antioxidant capacity, higher total superoxide dismutase activity, higher dressing percentage, higher cross-sectional area of loin, higher myofibre density, lower ultimate pH of the meat, and higher meat redness, than nervous lambs. Selection for calm temperament could be beneficial to health, slaughter, and carcass traits in Hu ram lambs.

Genetic evaluation of maternal behaviour and temperament in Australian sheep

The temperament of ewes and maternal behaviour at lambing has been implicated as contributing factors to lamb survival. Some 14 054 records of maternal behaviour score (MBS, 1 = good, 5 = poor) were collected at lamb tagging from 32 breeds of sheep over several years in a variety of environments. Records for two objectively scored temperament traits, flight time from a weighing crate (FT) and agitation score in an isolation box test (IBT) were available on 19 151 and 17 159 animals, respectively. These data were pooled from three sources, which included research and commercial ram breeding flocks. The combined data were also split into three subsets based on breed groups (Merino, Maternal and Terminal) for analyses. Records of weights and number of lambs weaned (NLW), as well as pedigree information was available from the national genetic evaluation database. The heritability estimates from the combined analyses were 0.20 ± 0.02 for MBS, 0.18 ± 0.02 for FT and 0.26 ± 0.02 for IBT, with a repeatability of 0.24 ± 0.01 for MBS. There were some small differences between the breed groups in the heritability estimates. The genetic correlations between FT and MBS were negative (favourable) and consistent across the datasets (–0.47 ± 0.12, combined analysis). The genetic correlations between IBT and MBS were positive (favourable) but not significant (0.12 ± 0.11, combined analysis). The genetic correlations between IBT and FT were also favourable, but small and generally not significant. There were small favourable genetic correlations between MBS and various bodyweights (–0.17 ± 0.07, yearling) and NLW (–0.25 ± 0.07). However, there were no significant genetic relationships between the temperament and production traits. The moderate heritability and repeatability of MBS indicate maternal behaviour could be improved by selection, and that it could be a useful additional trait in breeding programs for improved reproduction.