title: Evaluation of available energy and total tract digestibility of acid-hydrolyzed ether extract of cottonseed oil for growing pigs by the difference and regression methods.
abstract: OBJECTIVE
  The objective of this study was to determine the effect of inclusion level on the digestible energy (DE), metabolizable energy (ME), and total tract digestibility of acid-hydrolyzed ether extract (AEE) of cottonseed oil when fed to growing pigs.
  
  
  METHODS
  Forty-two barrows (initial body weight = 35.51±2.01 kg) were randomly allotted to a completely randomized design with a corn-soybean meal basal diet, five levels of cottonseed oil (2%, 4%, 6%, 8%, and 10%) and a 10% soybean oil diet. Each diet was replicated six times with one pig per replicate. The experiment lasted 19 days, 7 d for cage adaptation, 7 d for diets adaptation and last 5 d for feces and urine collection. The energy values and apparent total tract digestibility (ATTD) of cottonseed oil and soybean oil were calculated by the difference method, and regression equations were established to predict the energy values of cottonseed oil. The apparent digested fat of the entire intestinal tract was also regressed against dietary fat intake to determine the true total tract digestibility (TTTD) and endogenous loss of fat for cottonseed oil.
  
  
  RESULTS
  The results showed that the DE and ME contents of cottonseed oil were not different as the inclusion level increased. The DE and ME values determined by the regression equation were 36.28 MJ/kg and 34.96 MJ/kg, respectively, and the values were similar to the mean DE and ME values calculated by the difference method (36.18 and 35.56 MJ/kg, respectively). The ATTD of cottonseed oil was also not affected by the inclusion level of cottonseed oil, and the TTTD and EFL determined by the regression method were 92.40% and 13.83 g/kg of dry matter intake for corn-soybean basal diet. The DE, ME, and ATTD of AEE in soybean oil determined by the difference method were 35.70 MJ/kg, 35.20 MJ/kg and 92.31%, respectively. There were no differences in the DE, ME, and ATTD between cottonseed oil and soybean oil, although the ratio of unsaturated to saturated fatty acids for soybean oil was higher than for cottonseed oil.
  
  
  CONCLUSIONS
  The DE, ME, and ATTD values of cottonseed oil were not affected by its dietary inclusion level. The energy values of cottonseed oil determined by the difference and regression methods were similar. Furthermore, the ratio of unsaturated to saturated fatty acid for oils was not the decisive factor to influence the energy values and ATTD of oils.
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China.
authors.forename: Jinbiao
authors.initials: J
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China.
authors.forename: Zhongchao
authors.initials: Z
authors.lastname: Li
authors.affiliation: New Hope Liuhe Co., Ltd, Beijing 100102, China.
authors.forename: Mingbin
authors.initials: M
authors.lastname: Lyu
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China.
authors.forename: Xiangshu
authors.initials: X
authors.lastname: Piao
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China.
authors.forename: Defa
authors.initials: D
authors.lastname: Li
keywords: Cottonseed Oil; Digestibility; Digestible Energy; Growing Pigs; Metabolizable Energy; Soybean Oil