Effect Of Dietary Protein Level On The Growing Performance And Meat Quality In The Tri-crossbreeding Pigs From Duroc×Yorkshire×Bamei

The tri-crossbreeding pigs from Duroc×Yorkshire×Baimei is as the main production methods exerting hybrid odds, taking advantage of local breeds and foreign breeds of lean,whose characteristic is in fast growing, higher lean rate, better meat quality and greater capacity to accumulate fat. The aim of this study was to investigate the effect of dietary protein levels on the fattening performance, carcass trait, meat quality and related gene expression in the Duroc×Yorkshire×Baimei pig. Twenty-seven healthy fattening pigs with a similar genetic background and body weight(25 Kg) were randomly allotted into three groups.There are nine pigs in each group with three replicates, three pigs were used in per replicate. each group fed diet containing different protein levels. The dietary protein levels were low protein(L.cp:12%), medium protein(M.cp:14%),high protein(H.cp:16%)respectively. The trail lasted 122 days. The results are as follows:1、 Fattening performance: the average daily gain of 14% and 16% protein group are 512 g and 502 g, feed conversion ratio are 3.53 and 3.51 during the period of fattening. They are significantly better than the 12% protein group(P<0.05).2、 Carcass Traits: the diet protein levels have no obvious difference on slaughtering performance of pig(P>0.05). However, with the increase of dietary protein levels, the back fat thickness and fat rate showing a declining trend. The body weight and lean meat rate of the pigs fed with 14% and 16% protein diet are higher than 12% protein group.3、 Meat Quality: The diet protein levels had no significant effect on the meat quality index of pig(P>0.05). 14% and 16% protein diets group have a good p H value and better ability to retain water in muscle, but the meat tenderness is not good enough. There were no significant effects of dietary protein levels on amino acid composition in vivo, suggesting that the meat nutritional value was comparable in these three groups of different crude protein. Muscle unsaturated fatty acids compositions were regulated by dietary protein levels, 14% protein group have better intramuscular fat content of longissimus dorsi muscle.in pigs4、 Tissue morphological characteristics: The pigs fed with 16% protein diets had significant effect on fiber cross-sectional area of longissimus dorsi muscle(P<0.05),which is higher than 12% protein group, demonstrating that high level of dietary protein results in more coarse of muscle fibers and the worse of tenderness. Adipose cell diamter of 14% and16% protein groups pig are significantly lower than 12% protein group(P<0.05),suggesting the higher protein levels are, the less fat cells diameter.5、 Meat quality related gene expression: Real-time PCR showed the high dietary protein level expression lead to increase relative expression of SCD, PEPCK, MC4 R, ADRB3 in longissimus muscle, and the trend is similar with intramuscular fat content. The results showed that dietary protein level regulate intramuscular fat content by influencing its related gene expression.In summary, These pigs fed with 14% and 16% protein diet had a better performance on fattening index and ideal Carcass Traits. 14% protein group have better intramuscular fat content and more tender meat. So, 14% protein diet is more suitable for actual production.