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.

Comparison of Antioxidant Capacity and Muscle Amino Acid and Fatty Acid Composition of Nervous and Calm Hu Sheep.

This study determined the effect of temperament on antioxidant capacity and the relationship between antioxidant capacity and the contents of amino acids (AA) and fatty acids (FA) in muscle of Hu sheep. Organ and muscle samples of five calm and five nervous Hu sheep were collected to determine the antioxidant capacity and the contents of AA and FA in muscle tissue. The concentrations of malondialdehyde (MDA) and superoxide excretion enzyme (SOD) in muscle and intestinal tissue of calm Hu sheep were lower than those of nervous Hu sheep (p < 0.01), and the activity of glutathione peroxidase (GSH-Px) in liver of calm Hu sheep was significantly higher than that of nervous Hu sheep (p = 0.050). The content of AA of calm Hu sheep was higher than that of nervous Hu sheep, especially the content of reductive amino acids, which was significantly higher than that of nervous Hu sheep (p = 0.029). Fatty acid content of nervous Hu sheep was higher than that of calm type, and saturated fatty acid content was significantly higher than that of calm type (p = 0.001). The SOD content in muscle tissue was positively correlated with the contents of aspartic acid (Asp), alanine (Ala) and lysine (Lys). Catalase (CAT) activity was positively correlated with Ala content. There was a significant positive correlation between total antioxidants (T-AOC) and glutamate (Glu) (p < 0.05). MDA concentration was positively correlated with lauric acid (C12:0), triseconic acid (C13:0), myristic acid (C14:0) content (p < 0.01), and ginkgo acid (C15:0) content. The total antioxidants (T-AOC) was negatively correlated with stearic acid (C18:0) (p < 0.05). Our conclusion is that the antioxidant capacity of calm Hu sheep is superior to that of nervous Hu sheep, which may be due to the higher AA (especially reductive amino acids (Arg, Lys, Ala and Glu)) content in the muscle and the lower FA (especially SFA) content, which improve the antioxidant capacity of the organism and allow for further exploration of the mechanisms by which animal temperament affects antioxidant performance.

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.