Studies On The Application Of Different Net Energy Levels In Low Crude Protein Diets On Growing-Finishing Pigs

The experiment was conducted to investigate the effects of net energy(NE) levels in low crude protein diets supplemented with crystalline amino acids of the growing-finishing pigs on the growth performance,and carcass characteristics.216 pigs(Duroc×Landrace×Large white) with average BW of 37 kg were randomly allotted to 6 treatments by weight with six replicates per treatment and six pigs per replicate.In the growing phase(37 to 70 kg) and finishing phase(70 to 95 kg),pigs were fed with a 18%or 15.5%crude protein(CP) and 2450 Kcal/kg NE diet as control as well as five low-protein diets(14%or 11.5%) in which the dietary protein content was reduced by approximately 4.0 percentage units with the diets supplemented with crystalline lysine(Lys),methionine(Met),threonine(Thr) and tryptophan(Trp) to meet NRC requirements.Five levels of NE(2520,2450,2380,2 300,and 2250 Kcal/kg) were formulated by altering the levels of wheat bran and soybean oil in the diets.The results indicated that no significant difference was found in growth performance,carcass characteristics,serum amino acids(SAA)(besides arginine(Arg)) and serum urea-N(SUN)(P＞0.05) among six treatments.The average daily gain(ADG) and feed efficiency(G/F) of the groupⅣ,Ⅴwere significantly higher than those of the groupⅡ(P＜0.05) among different stages.No significant difference was found in ADG(P=0.31),average daily feed intake(ADFI) (P=0.91) and G/F(P=0.40) among the trials in the growing phase(37 to 70 kg).In the finishing phase(70～95 kg),as dietary NE levels decreased among the trials,the ADG(P=0.02) and the percentage fat-free lean(PFFLEAN)(P=0.01) increased significantly.Furthermore,the G/F showed a decreasing tendency(P=0.06) as well as the percentage total fat(PTOFAT) decreased significantly(P=0.03).The longissimus muscle area(LMA),and PFFLEAN of the control and the groupⅤwere significantly higher than those of the groupⅡ(P＜0.05),while the PTOFAT were significantly lower than that of the groupⅡ(P＜0.05).In the all trial period(37～95 kg),as dietary NE levels decreased,the ADG increased significantly(P=0.04) and G/F decreased significantly(P=0.05),but the ADFI had no significant difference(P =0.94).In conclusion,compared of growth performance and carcass characteristics, the NE level of 2 250 Kcal/kg was suitable for pigs fed low protein diet.