Effects of digestible lysine on growth performance and serum biochemical parameters in growing-finishing pigs

A total of eighty Duroc(Landrace×Yorkshire)growing-finishing pigs with 40 kg of average body weight were used in this study to evaluate the effects of different digestible lysine(DLys)levels(0.59%,0.67%,0.75%,0.83%,0.91%)on growth performance and serum biochemical parameters in order to determine the optimal DLys levels in growing-finishing pigs.The experimental diets were based on corn-soybean meal with isoenergy and the same amino acid pattern.The results showed that average daily gain(ADG)and feed/gain(F/G)changed with the elevated DLys levels quadratically.The established DLys requirement of growing-finishing pigs was not the same when using different evaluation index.The optimal DLys level was 0.78% for hightest ADG(791.42 g),and 0.80% for lowest F/G(2.92).The concentrations of glucagon,insulin,thyroxine T3 and T4 at 0.75% of DLys level were higher,while glucose concentration was lower compared with the other groups(P 0.05).These findings suggested that the optimal DLys and crude protein levels in growing-finishing pigs with 40-70 kg of body weight were 0.78%,15.66%,respectively.