| In order to study the effects of different degrees of cold stress on growth performance,blood biochemical indexes,serum hormone level,immunoglobulin content,muscle quality of longissimus dorsi,muscle fiber characteristics,antioxidant enzyme activity and My HC gene expression in finishing pigs.In this experiment,54 healthy three way fattening pigs with similar age(120 ± 7 days)and body weight were randomly divided into three groups,each group had six replicates,each replicate had three pigs.Three temperature treatments were carried out: 8 ± 2 ?,13 ± 2 ?,20 ± 2 ?.Group A(low temperature group)represents 6-10 ?,group B(moderate temperature group)represents 11-15 ?,and group C(moderate temperature group)represents 18-22 ?.The pre feeding period was 7 days,and the experimental period was 28 days.During the experimental period,0,14 and 28 days were selected for the determination of related indexes.The present study showed that:(1)Effects of cold stress on growth performance and blood biochemical indexes of finishing pigs(1)ADG of group A was significantly higher than that of the other two groups(P.In this experiment,the feed weight ratio of cold stress group decreased significantly,daily gain increased significantly;(2)GH content decreased significantly with the decrease of feeding temperature(P < 0.05).LEP in group B was significantly higher than that in the other two groups(P < 0.05),and ACTH in group A and B was significantly higher than that in group C(P < 0.05).There was no significant difference between group A and group B(P > 0.05).The results showed that cold stress could significantly increase the bun content in the serum of fattening pigs,decrease the TG and TP content,increase the TC content first and then decrease;(3)the bun content decreased significantly with the increase of feeding temperature(P < 0.05);the TG and TP content increased significantly with the increase of feeding temperature(P < 0.05);the TC content of group A was significantly lower than the other two groups(P < 0.05).The results showed that cold stress could significantly reduce the concentrations of GH and LEP,and significantly increase the content of ACTH.(2)Effects of cold stress on muscle quality and fiber characteristics of finishing pigs(1)In terms of meat color,L * in group A was significantly higher(P < 0.05),a * was significantly lower(P < 0.05);cold stress could significantly reduce the pH value and shear force in group A(P < 0.05),and group A was significantly lower than group B and C(P < 0.05).The drip loss of group a increased significantly(P < 0.05).The content of intramuscular fat in group A was significantly lower than that in group C(P < 0.05).It can be concluded from this experiment that cold stress will lead to a decrease in the color score of the longest muscle on the back of finishing pigs,a significant decrease in the shear force and the content of intramuscular fat,and a significant increase in the water loss.(2)The diameter and area of muscle fibers in group A were significantly smaller than those in the other two groups.The muscle fiber density of group A was significantly higher than that of the other two groups.The results showed that cold stress significantly reduced the diameter and cross-sectional area of muscle fibers,and increased the density of muscle fibers.(3)Effect of cold stress on antioxidant enzyme activity and immunoglobulin content in finishing pigs(1)The content of SOD and cat increased significantly with the increase of feeding temperature(P < 0.05).On the 28 th day,the content of SOD in group B was significantly higher than that in group A and C(P < 0.05);cat in group C was significantly higher than that in other groups,and there was no significant difference between group A and group B(P > 0.05).There was no significant difference in GSH PX content between groups a,B and C on the 14 th and 28 th day(P > 0.05).The results showed that cold stress significantly reduced cat and SOD activities,but no significant change in GSH PX activity.(2)The content of Ig G in group A and B was significantly lower than that in group C(P < 0.05),and there was no significant difference between group A and group B(P > 0.05).The results showed that cold stress could significantly reduce the content of Ig G and Ig M in serum and the immunity of finishing pigs.(4)Effect of cold stress on the expression of related genes in finishing pigsThe expression of My HC IIa gene was not significantly different among the three groups(P > 0.05);the expression of My HC IIB gene in group C was significantly lower than that in groups A and B(P < 0.05);the expression of My HC IIX gene was not significantly different.The effect of cold stress can increase the proportion of type IImuscle fiber and decrease the proportion of type I muscle fiber,which has a bad effect on the quality of the muscle.In conclusion,cold stress can significantly reduce the growth performance of finishing pigs;it has a significant impact on the serum lipid index of finishing pigs,and the atch content is significantly increased,the GH content is significantly reduced.Cold stress has a significant adverse effect on muscle quality,which leads to the decrease of water power and flesh color,the decrease of diameter and cross-sectional area of muscle fiber,and the increase of muscle fiber density.Under the condition of this experiment,the content of cat and SOD in finishing pigs decreased significantly,indicating that the pigs in the low temperature group were in the state of cold stress;in addition,the content of Ig A in the serum of the low temperature group and the middle temperature group was significantly lower than that of the warm group,indicating that the cold stress reduced the immunity of finishing pigs.Under the condition of this experiment,the expression of My HC ? gene was significantly increased and the expression of My HC ?gene was significantly decreased in the middle cold stress group of the longissimus dorsi muscle of finishing pigs. |
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