The Digestible Lysine Requirement Of Ideal Amino Acid Pattern In Growing And Finishing Pigs

Currently, most of amino acid nutrition research focused on the ideal amino acid pattern, while the study on the appropriate dietary lysine level under ideal amino acid pattern was very limited. This single factorial designed experiment was conducted to establish the appropriate dietary digestible lysine levels of growing pigs (40～70kg) and finishing pigs (70～100kg). The true digestibility of lysine in feedstuff was estimated by enzyme-hydrolyzed casein.The first experiment was conducted to establish the proper digestible lysine levels for 40～70kg growing pigs. A total of eighty Duroc×(Landrace×Yorkshire) growing pigs with 40 kg of body weight were randomly allocated into five groups(4 replications per group,4 pigs per replication, half male and half female) .The digestible lysine concentrations in five diets were 0.59%, 0.67%, 0.75%, 0.83%, 0.91%. The experimental diets were based on corn-soybean meal with isoenergy (14.21MJ/kg) and same amino acids pattern. The crude protein concentrations in the diets were 11.80%,13.40%,15.00%,16.60%,18.20%. The results showed that average daily gain and feed/gain changed with the elevated digestible lysine levels quadratically. The established digestible lysine requirement of growing pigs was not the same when using different evaluation index. The optimal digestible lysine level was 0.78% for highest average daily gain (791.42g/d), but the optimal digestible lysine level was 0.80% for lowest feed/gain (2.92). The glutamic oxaloacetic transaminase activity were maximized (P<0.05), the feed/gain was minimal (P<0.05), the serum urea nitrogen concentration was minimal (P<0.01) at 0.75% of digestible lysine levels compared with the other groups. The concentrations of T3, insulin, growth hormone and insulin-like growth factor-I at 0.75% of digestible lysine levels were higher (P< 0.05) compared with the other groups. The dressing percentage (P<0.05), lean meat percentage (P>0.05), longissimus muscle area (P<0.01), average backfat thickness (P<0.01), tenth rib fat depth (P<0.01) of barrows first increased and then decreased (P<0.05) with dietary digestible lysine levels, and reached the maximum value in 0.75% digestible lysine treatment group. The carcass components (except for water and lipid content) of the muscle samples (except for the quadriceps muscle) were influenced (P<0.05) by the digestible lysine level. These findings suggest that the optimal digestible lysine levels in growing pigs with 40～70 kg of body weight were 0.78%The second experiment was conducted to establish the proper digestible lysine levels for 70～100kg finishing pigs. A total of sixty Duroc×(Landrace×Yorkshire) finishing pigs with 70 kg of body weight were randomly allocated into five groups (3 replications per group, 4 pigs per replication, half male and half female) .The digestible lysine concentrations in five diets were 0.47%, 0.53%, 0.59%, 0.64%, 0.71%. The experimental diets were based on corn-soybean-wheat bran meal with isoenergy (13.60MJ/kg) and same amino acids pattern. The crude protein concentrations in the diets were 10.46%, 11.78%, 13.12%, 14.40% and 15.78%. The results showed that average daily gain and feed/gain changed with the elevated digestible lysine levels quadratically. The established digestible lysine requirement of fishing pigs was not the same when using different evaluation index. The optimal digestible lysine level was 0.61% for hightest average daily gain (778.37g/d) and lowest feed/gain (3.24). Fat free lean index was highest at 0.59% digestible lysine group (P<0.01). The concentration of serum urea nitrogen increased with increasing digestible lysine levels(P<0.05); The concentrations of grow hormone (P<0.05) and insulin-like growth factor-I (P<0.05) first increased and then decreased with dietary digestible lysine levels, and reached the maximum value in 0.59% digestible lysine level. The longissimus muscle area (P<0.05) increased with increasing digestible lysine levels, while tenth rib fat depth (P>0.05) and average backfat thickness (P>0.05) decreased. The carcass components (except for water and lipid content) of the muscle samples (except for the biceps femoris and quadriceps muscle) were influenced (P< 0.05) by the digestible lysine levels. These findings suggest that the optimal digestible lysine levels in finishing pigs with 70～100 kg of body weight were 0.61%.