| Two experiments were conducted to assess the effect of stocking density of broilers during simulation transportation, duration and anti-stress feed additive on physiological and biochemical parameters, heat stress protein HSP70 expression and meat quality.In experiment 1, total of 48 male broilers at 49d were divided into 5 groups, with 8 in treatment 1,3,5 (low stocking density, 8 male broilers/0.64m2), and 12 in treatment 2,4 (high stocking density, 12 male broilers/0.64m2). The transportation was applied by using simulating transportation mode. Treatment1 and 2 were standing for 2h, treatments 2 and 4 were transported for 2h, treatments3 and 5 were transported for 4h. The results showed that transportation stress decreased the level of the serum T3(P<0.05)and T4 (P>0.05), but did not influence COR. With the transportation time being prolonged and stocking density being increased, serum INS gradually decreased numerically. with the high density/transport 4h being the most affected group. Meanwhile transportation increased the muscle glycogen content(P<0.05), but did not affect blood glucose. Transportation treatment significantly affect the activity of Serum AST(P<0.05), and tende to improve CK,GGT and LDH(P>0.05). Transportation stress resulted in an increase of breast muscle and leg muscle MDA. MDA was increased with high stocking density and decreased with the prolonged trasportation time. Transporation stress also increased the activity of muscle NOS and SOD, and the activity of SOD was increased with the increase in tranportation time and stocking density. For the treatment of 4h transportation, high stocking density resulted in a high SOD content in breast muscle than the low stocking density. The treatment of 4h transportation at a high stocking density had a higher SOD content in leg muscle than the 2h transportation at a low stocking density. Transportation for 2h improved HSP70 mRNA Abundance(P<0.05), but transportation for 4h, HSP70 mRNA Abundance reduced back to the normal level. Transportation stress reduced drip loss of breast muscle and leg muscle at 24h , breast muscle pH and lactate level, increased the drip loss of breast muscle and leg muscle at 1h, pH and level in the leg muscle. This result indicated while transportation stress can induce tissue peroxidation injury, broilers had the capacity of adapting to the transportation stress. And HSP70mRNA expression of the relative rise on Short-term transport stress.In experiment 2, forty male broilers at 49d were divided into 5 groups with 8 broilers per group. Treatment 1 and 2 were fed with basic diets while treatments 3,4,5 were fed diets supplemented with MgCl2 , chromium picolinate and VC, respectively. After continuously feeding for 1w, diet and water were removed and chikens were loaded to the transporter at 8 male broilers/0.64m2. Treatment1 was standing without stransportation, and treatments 2,3,4,5 were transported for 2h at a speed of 60km/h on the country road. The result showed that broilers fed the diets contained MgCl2 , chromium picolinate and VC for 1w had a better the capacity to cope with transportation stress. Feeding diet with VC significantly decreased muscle MDA content and improved gene expression level of HSP70 and activity of GSH-Px,NOS and SOD(P<0.05),,slowed down Cortisol reduction caused by transportation stress. In addition, feeding diet with VC significantly improved 1h drip loss of breast muscle and 1h and 24h drip loss of leg muscle, decreased breast muscle LD content, slowed down reduction of breast muscle pH and increased of leg muscle glycogen content resulted from transportation stress. Supplementing chromium picolinate to diet decreased MDA level of breast muscle,but had no effect on the activity of SOD,NOS and GSH-Px. However, broilers fed on diet containing chromium picolinate had a lower breast muscle Lactic Acid content, leg muscle glycogen and pH(P<0.05)and . a high gene expression level of HSP70 and 1h drip loss. The addition of high dose magnesium chloride in the diets improved the activity of SOD in breast muscle and leg muscle,, decreased muscle MDA content(P<0.05),, improved 1h and 24h drip loss of breast muscle and leg muscl(eP<0.05). These results suggest that the three additives had significant difference in anti stress mechanism, with magnesium chloridebeing more effective in protecting broilers from transportation stress. |
