Effects Of Vitamin A Levels On The Carcass Composition And Meat Quality In Steers

Two experiments were included in this study. Experiment one: The objective of experiment one was to determine the influence of short-time feeding (3 months) different vitamin A levels diets on carcass composition and meat quality in 12 month-old and 24 month-old Limosin×Luxi Crosses steers. The trial had adopted one-factor completely random design where sixteen 12 month-old finishing steers were equally divided into 4 treatments with 12-A,12-B,12-C,12-D respectively, that was 12 month group, and sixteen 24 month-old finishing steers were equally divided into 4 treatments with 24-A,24-B,24-C,24-D respectively, that was 24 month group. 4 vitamin A levels were added into the same basal diet, and the experiment lasted 90 days. Four dietary treatments consisted of the basal diet (Treatment A), basal diet + 50% of VA nutrient requirement (2200 IU/kg of DM, equivalent to 5.5 mg β-carotene) (Treatment B), basal diet + 100% of VA nutrient requirement (Treatment C) and basal die + 200% of VA nutrient requirement (Treatment D). The result showed that vitamin A levels had no significant effect on carcass quality characteristics in 12 month group (P>0.05); and had no significant effect on GM (gluteus medius) and LL (longissimus dorsi) haem pigment concentration in 12 month group during ageing (P>0.05) while B treatment of LL haem pigment concentration was highest; Vitamin A levels had significant effect on GM and LL TBARS in 12 month group during ageing (P<0.05) while B treatment TBARS was lowest. Vitamin A levels had no significant effect on carcass quality characteristics except spleen weight/body weight and subcutaneous fat thickness in 24 month group (P>0.05); and had significant effect on GM and LL haem pigment concentration and TBARS in 24 month group during ageing (P<0.05) while D treatment of LL and GM haem pigment concentration was highest, but its TBARS was lowest. Vitamin A levels had no significant effect on marbling score and shear value in 12 month group and 24 month group; and also had no significant effect on GM and LL pH in the two month groups (P>0.05) while GM pH1 was higher than that of LL; vitamin A levels had significant effect on GM and LL nutrient value and the ratio of water loss of both month groups (P<0.05) while the ratio of water loss of A treatment was lowest, and the ratio of water loss of GM was lower than that of LL; EE content of A treatment of the two month groups was higher than that of other three treatments of the same month group; meanwhile, EE content was decreased with the growth of vitamin A while a little growth when VA of 200% nutrient requirement was added into basal diet (that is D treatment). Experiment two: The objective of experiment two was to determine the influence of long-time feeding (6 months) different vitamin A levels diets on carcass composition and meat quality in 12 month-old Limosin×Luxi Crosses steers. The trial had adopted one-factor completely random design where sixteen 12 month-old finishing steers were equally divided into 4 treatments with A,B,C,D, respectively. And 4 vitamin A levels were added into the same basal diet. the experiment lasted 180 days. Four dietary treatments consisted of the basal diet (Treatment A), basal diet + 50% VA nutrient requirement (2200 IU/kg of DM, equivalent to 55mg β-carotene) (Treatment B), basal diet + 100% VA nutrient requirement (Treatment C), basal diet + 200% VA nutrient requirement (Treatment D). The result showed that vitamin A levels had no significant effect on marbling score and carcass quality characteristics except for back fat thickness (P>0.05); and had no significant effect on GM and LL nutrient value except for DM and protein (P>0.05). Vitamin A levels had significant effect on shear value, drip loss, the ratio of water loss, haem pigment concentration and TBARS (P<0.05) while drip loss of treatment B was lower than that of other three treatments. The ratio of loss water of A treatment was lowest, then B treatment. The shear value of B treatment was lowest, then C treatment. The haem pigment concentration of B treatment was highest, but its TBARS was lowest.