Effects of reducing the ratio of dietary lysine to net energy on performance and meat quality in finishing pigs.

This experiment was conducted to determine the effects of reducing the ratio of dietary lysine(Lys)to net energy(Lys/NE)on performance and meat quality in finishing pigs.One hundred and forty Yorkshire pigs with initial average body weight of(30.0±1.6)kg were randomly allotted to 5 treatments(4 replicates per treatment and 7 pigs per replicate)based on their body weight and sex.During the 30~61 kg phase,all pigs were fed the same diet.During the finishing phase,pigs in each treatment were randomly fed with one of five diets:control,low Lys-1,low Lys-2,low protein-1 and low protein-2(CP levels were 15.20%,15.02%,15.11%,12.73% and 10.10%,respectively;Lys/NE ratios were 0.72,0.58,0.46,0.58 and 0.46 g/MJ,respectively).The results showed that the low Lys-1 and low Lys-2 treatments had significantly increased average daily gain(ADG)and intramuscular fat(IMF)content of pork in finishing pigs(P0.05)compared with control,but simultaneous decrease of CP level had no significant difference on ADG and IMF of pork compared with control(P0.05).Different treatments had no significant effect on average daily feed intake,F/G,alive weight,dressing percentage,pH1 h,pH24 h,shear force and drip loss(P0.05).Low Lys-2 and low CP-2 treatments had lower meat color value than control diet(P0.05).No significant effects on plasma urea nitrogen(PUN)content were observed among other treatments(P0.05),except that plasma UN content in low protein-2 treatment was significantly lower than that in control(P0.05).Compared with control,pigs fed the low Lys-1 and low Lys-2 diets had lower plasma IGF-Ⅰ content(P0.05),while pigs fed low protein-1 and low protein-2 diets had higher plasma IGF-Ⅰ content(P0.05).The results indicated that Lys/NE in diet decrease from 0.72 to 0.46 g/MJ could improve IMF content of finishing pigs;Lys/NE in diet reaching 0.46 g/MJ with protein level being 10.1% could decrease feed conversion rate of finishing pigs.