Study On Prediction Models Of Body Protein Retention And Amino Acid Requirement For Landrace × Rongchang Growing-Finishing Pigs

This experiment was designed to study the growth laws of pig performance, carcass quality and body protein retention related to body weight (BW) in order to establish requirement model of amino acids for growing-finishing pigs. Forty-eight Landrace X Rongchang pigs with 20 + 1kg of initial bodyweight were distributed randomly into 6 pens of half for males and half for females. Pigs were fed a diet with DE 3.4MJ/kg from 20kg through 100kg. 3 males and 3 females were slaughtered respectively when pigs reached 20kg, 35kg, 50kg, 80kg and 100kg BW for determining protein retention rate.The results showed that the average daily gain (ADG), average daily feed intake (ADF1) and feed /gain for 20-100kg period were 762g, 2153g and 2.79 respectively. There was no significant difference in performance between males and females. The regression equation between ADG and BW was.- ADG (g/d) =293.03 + 15.1 BW-0.1034BW2 (R2=0.9988, P<0.01) .The dressing rate (DR) was linearly related to BW, as DR (%)=0.1759BW+ 56.275 (R2=0.9616 P<0.05). Sex had no significant effect on DR (p>0.05) . Backfat thickness (BFT) and the loin eye area (LEA) increased as BW enhanced up to 80 kg. The growth of LEA and BFT was fastest at the stage of 50-80kg. There was a trend that BFT of females was larger ,and LEA. Lean percentage decreased gradually as BW increased. The difference of lean percentage between males and females was not significant.The growth model of protein retention (y, g/d) , based on the data of fat-free muscle growth determined in this experiment and coefficients from NRC (1998) ,was.- y = 72.211 -1.5275BW + 0.0648 BW2-0.0005BW3 (R2=0.955P=0.067) .The true digestible lysine requirement model was : Y (mg/d) =8665.41-183.3BW+7.7788BW2 -0.0612BW3 4- 36 BW075. It was calculated from this equation that total lysine requirement was 11.18, 15.76 and I3.43g/d, true digestible lysine requirement was 9.67, 13.63 and 11.61g/d for LandraceX Rongchang pigs at stage of 20-50kg, 50-80kg and 80-100kg respectively. The dietary total or true digestible lysine requirement was 0.71%, 0.64% and 0.47%, or 0.63, 0.58 and 0.44% respectively for 20-50kg, 50-80kg and 80-100kg stage. Based on the ideal protein model recommended by NRC (1998) , otheressential amino acid requirements were able to be calculated.