• Animal Bioscience
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• v.34 no.11
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• pp.1849-1858
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• 2021

Objective: Tenderness is a very complex feature, and the process of its formation is very complicated and not fully understood. Its diversification is one of the most important problems of beef production, as a result beef aging is widely used to improve tenderness as it is believed to provide a homogeneous product to consumers. While few studies have evaluated the muscle structure properties in relation to tenderness from early post-mortem, there little to no information available on how the muscle nanostructure of beef carcasses changes during post-mortem ageing to determine the appropriate aging time for acceptable tenderness. Methods: Muscle nanostructure (myofibril diameter [MYD], myofibril spacing [MYS], muscle fibre diameter [MFD], muscle fibre spacing [MFS], and sarcomere length [SL]), meat tenderness and cooking loss [CL]) were measured on 20 A2 longissimus muscles of Bonsmara, Beefmaster, Hereford, and Simbra at 45_mins, 1, 3, and 7 days post-slaughter. Muscle nanostructure was measured using a scanning electron microscope, while tenderness was measured using Warner Bratzler shear force. Results: At 45 minutes post-slaughter, breed affected MYD and MYS only, while at 24_hrs it also affected MFD and MFS. On day 3 breed effected MFS and SL, while on day 7 breed effected tenderness only. As the muscles matured, both MYD and MYS decreased while CL increased, and the muscles became tender. There was no uniformity on muscle texture features (surface structure, fibre separation, muscle contraction, and relaxation) throughout the ageing period. Conclusion: Meat tenderness can be directly linked to breed related myofibril structure changes during aging in particular the MYD, spacing between myofibrils and their interaction; while the MFD, spacing between muscle fibres, SL, and CL explain the non-uniformity in beef tenderness.

• Animal Bioscience
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• v.34 no.11
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• pp.1829-1838
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• 2021

Objective: The effects of maternal dietary energy levels on breast muscle fibre development in offspring of broiler breeders were investigated. Methods: A total of 480 20-week-old Arbor Acres (AA) healthy female broiler breeders, with an average body weight of 2.33±0.01 kg, were randomly divided into 4 treatment groups with 6 replicates and 20 broiler breeders for each replicate and fed a corn and soybean meal diet with 100%, 80%, 70%, and 50% energy levels, respectively. Approximately 300 eggs per treatment were collected for incubation for 6 days. Then, 120 0-day-old female broilers at each energy level were randomly selected and divided into 6 replicates with 20 broilers for each replicate, with this experimental phase with the offspring lasting for 49 days. Results: Compared with the 100% energy group, the breast muscle fibre diameter at embryonic day 21 in the 80% energy group was significantly reduced (p<0.05). In the 80% energy group, the muscle fibre density of the breast increased significantly (p<0.05) at embryonic days 15 and 21. The breast muscle fibre diameter of the offspring in each group was significantly decreased (p<0.05) on the 1st day. The breast muscle sarcomere length of the embryos in the 80% energy group was significantly higher (p<0.05) than those in the 70% and 50% energy groups. Compared with the 100% energy group, the expression of the myostatin gene in the offspring was significantly decreased (p<0.05). Conclusion: In conclusion, the effects of a maternal dietary energy level of 80% in this study were found to be optimal for breast muscle fibre development in offspring, which indicated that the metabolic energy level of AA broilers of 9.36 MJ/kg for the mid-term diet for laying eggs has a more practical significance.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.1
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• pp.26-33
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• 2002

In order to assess the effect of feeding raw or processed cotton (Gossypium) seed meal (CSM) on meat and wool production, 30 male crossbred lambs (3-4 months) of uniform body weight were assigned equally to five dietary treatments in a completely randomised design. The CSM was processed by three different methods i.e., cooking the meal at $100^{\circ}C$ for 45 minutes, treatment with 1% calcium hydroxide ($Ca(OH)_2$) for 24 h and iron treatment in the ratio of 1 part free gossypol (FG) to 0.3 parts of iron for 30 minutes. The lambs were fed isonitrogenous and isocaloric concentrate mixtures, containing 30% deoiled peanut meal (reference diet) and 40% of either raw, cooked, $Ca(OH)_2$ or iron treated CSM for 180 days. The raw and variously processed CSM replaced about 50% nitrogen of reference concentrate mixture. The concentrate mixtures were fed to meet 80% of the protein requirements (NRC, 1985) along with ad libitum chopped maize (Zea mays) hay. The slaughter weight, empty body weight and carcass weight was higher ($p{\leq}0.01$) in lambs fed cooked CSM incorporated diets, compared to diets containing deoiled peanut meal (DPNM). These parameters were not influenced by feeding diets containing either raw, $Ca(OH)_2$ or iron treated CSM in comparison DPNM diets. The carcass length, loin eye area and edible and inedible portion of carcass and the meat: bone ratio in whole carcass were also not affected by feeding CSM based diets. Among various primal cuts, the yield of legs was lower ($p{\leq}0.05$) from raw CSM fed lambs in comparison to DPNM fed lambs. The fat content in the Longissimus dorsi muscle was reduced ($p{\leq}0.05$) in lambs fed processed CSM based diets compared to those fed DPNM diet. Replacing DPNM with either raw or processed CSM based diets did not influence the sensory attributes and overall acceptability of meat. The wool yield was higher ($p{\leq}0.05$) in iron treated CSM fed lambs. The fibre length and fibre diameter were comparable among lambs on various dietary regimes. Among lambs fed variously processed CSM diets, the feed cost per kg of edible meat production was lower ($p{\leq}0.05$) on $Ca(OH)_2$ treated CSM, followed by cooked CSM diet and then on raw CSM based diets compared to DPNM diet. The CSM after 1% $Ca(OH)_2$ treatment or cooking for 45 minutes appears to be a satisfactory protein supplement in lamb diets for meat and wool production to replace at least 50% nitrogen of scarce and costly peanut meal.