Net Energy Prediction Equations For Cereal Ingredients In Growing Pigs

Five experiments were conducted to determine the net energy(NE)of corn,naked oat,brown rice,sorghum,wheat,millet,barley,partial dehulling barley and dehulled millet in growing pigs using indirect calorimetry and to develop and validate the prediction equations for NE of cereal ingredients.In Exp,1,a total of 36 barrows with an average initial body weight of 41.4 ± 2.0 kg were allocated across six treatments in a 2 x 3 factorial arrangement that included 2 feeding levels(2,400 kJ ME/kg BW0.6 per day or ad libitum)and 3 dietary amino acids(AA)supplementation patterns(corn diet with no AA;corn+ 3AA diet with addition of lysine,threonine and tryptophan;corn + 5AA diet with greater levels of crystalline lysine,threonine and tryptophan supplementation than those in corn+3AA diet,and with crystalline methionine and isoleucine supplementation).The experiment was conducted in 6 consecutive periods.During each period,6 pigs were allotted to 1 of 6 treatments,and each treatment corresponded to 1 of 6 respiration chambers.In each period,pigs were individually housed in metabolism crates and fed their respective diets at two feeding levels for 13 d,including 7 d for adaptation to the feed,metabolism crate and environmental conditions.Total feces and urine samples were collected and heat production was measured from d 8 to 12.On the last day of each period,pigs were fasted for 24 h and fasting heat production was subsequently measured.The total heat production(THP)and retention of energy(RE)increased(P<0.05)and the fasting heat production(FHP)tended(P = 0.09)to increase with increased feeding level.Feeding level did not affect the DE,ME and NE in corn.The THP and FHP increased(P<0.05)with AA supplementation in the diet.Dietary AA supplementation did not influence the DE and ME values in the corn but tended(P = 0.07)to increase NE value in the corn.In Exp,2,NE for 6 different corn varieties were determined and the equations to predict the NE of corn were established.Thirty-six growing barrows(Initial BW = 47.6 ± 3.4 kg)were allotted into 6 diets containing 6 different corn varieties.The experiment was conducted in 6 consecutive periods(6 pigs per period).The experimental procedure was the same as that in Exp.1.No significant differences were observed for the THP(1,290 kJ/kg BW0.6/d on average)and FHP(781 kJ/kg BW0.6/d on average)among 6 treatments.The NE values of six corn varieties were 12.85,12.95,13.21,13.18,12.91 and 13.22 MJ/kg DM,respectively.Stepwise regression analysis was performed to predict the NE value using chemical compositons of six corns.The equations were NE = 18.16-0.58 CP(R2 = 0.85,P<0.01)and NE = 18.44-0.56 CP-0.25 ADF(R2 = 0.95,P = 0.01).The equations were validated using cross validation method.The results showed that the relative deviation between NE values from literature and the predicted NE values were less than 5%,which indicated that the predict equations for NE of corn were accurate.In Exp.3,the NE of corn,naked oat,brown rice,sorghum,wheat and millet were determined using indirect calorimetry.Thirty-six barrows(Initial BW = 39.8 ± 2.7 kg)were allotted to 1 of 6 diets which included 6 cereal grains diets.The experiment was conducted in 6 consecutive periods(6 pigs per period).The experimental procedure was the same as that in Exp.1.The THP tended(P =0.05)to differ when pigs were fed different diets,but the FHP was not different when pigs were fed 6 diets.The NE of com,naked oat,brown rice,sorghum,wheat and mille were 12.72,14.05,13.81,12.43,11.69 and 11.59 MJ/kg DM,respectively.In Exp.4,the NE of barley,partial dehulling barley and dehulled millet were determined and then equations to predict the NE of cereal ingredients were established according to the results of Exp.1,2 and 3.Eighteen barrows(Initial BW = 43.6 ± 2.4 kg)were allotted to 1 of 3 diets which included 3 cereal grains diets.The experiment was conducted in 3 consecutive periods(6 pigs per period).The experimental procedure was the same as that in Exp.1.No significant differences were observed for the THP and FHP among 3 treatments.The NE of barley,partial dehulling barley and dehulled millet were 11.37,12.67 and 14.63 MJ/kg DM,respectively.Stepwise regression was used to predict the NE value from DE,ME and chemical compositon of the 16 cereal ingredients.The equations were as following:NE = 0.85 DE-1.88(R2 = 0.96,P<0.01),NE =0.88 ME-1.33(R2 = 0.96,P<0.01),NE = 0.86 GE + 0.12 CP-0.27 ADF-3.68(R2 = 0.75,P<0.01)and NE= 12.15 + 0.14 CP-0.25 ADF(R2=0.64,P<0.01).In Exp.5,the prediction equations of cereal ingredients were validated using a repeated test method.Twelve barrows(Initial BW = 44.5 ± 3.1 kg)were allotted to 1 of 2 diets,including 50%corn + 50%barley mixed diet and barley + enzymes diet in order to determine the NE values of corn + barley and barley.The prediction equations for NE of cereal ingredients were validated by calculating the difference between the measured NE values via experiment and the predicted NE values via equation of the two ingredients.The results showed that the measured NE values were consistent with the predicted NE values when diet was not supplied with enzyme.The equation that NE = 0.88 ME-1.33 had a better accuracy when diet was supplied with enzyme.