A total of five studies were conducted to determine the nutritional value of co-products of bioethanol production for poultry and pigs. The objective in the first study was to evaluate the relationship between the chemical components of maize- and wheat distillers dried grains with solubles (DDGS) as well as develop prediction equations for indispensable amino acids (IAA), total indispensable amino acid (TIAA) and total amino acid (TAA) contents using nutrient composition data available in literature. The relationship between the chemical constituents of maize- and wheat-DDGS and associated probability values were determined by correlation analysis. Prediction models for determining the IAA, TIAA and TAA contents of maize- and wheat-DDGS from their crude protein (CP) and amino acids (AA) contents were developed using step-wise multiple regression analyses. Maximum improvement in adjusted r2 (adj r2) and reduction in Mallows Cp were the model selection criteria. The chemical composition of maize- and wheat-DDGS varied among sources with coefficient of variation (CV) ranging from 8.5% to 53.5% for total P and Ca respectively in maize-DDGS and 10.5% to 36.1% for CP and acid detergent fibre (ADF) in wheat-DDGS respectively. Of the IAA, Lys, Met and Trp were most variable in maize-DDGS with CV of 13.1%, 12.0%, 10.3%, respectively, whereas Lys, Phe and Met were the most variable IAA in wheat-DDGS with CV of 20.2%, 17.3%, and 16.9%, respectively. For maize-DDGS, there were positive correlations (P < 0.05) between CP and CF, NDF, Ca, ash (r ranged from 0.45 and 0.61). Adjusted r2 ranged from 0.57 to 0.99 in the best models for predicting the IAA in maize- and wheat-DDGS from CP and AA. Except for Trp and Lys, the IAA contents of maize- and wheat-DDGS can be predicted from their CP content alone. The best models for predicting TIAA and TAA in maize-DDGS included Arg, His and Leu (adj r2= 0.98) and His, Leu and Trp (adj r2= 0.90) respectively, the regression equations being TIAA (% DM) = 0.77 + 1.36 (Arg) + 3.87 (His) + 1.99 (Val) and TAA = -3.03 + 14.1 (His) + 3.79 (Leu) + 23.4 (Trp) respectively. For wheat-DDGS, the best three variables for predicting TIAA were Arg, Leu and Val (adj r2=0.99), the regression equation being TIAA (% DM) = -0.07 + 1.11 (Arg) + 0.99 (Leu) + 5.02 (Val). Predicted values were close to actual values in the prediction models for IAA, TIAA and TAA. It was concluded that the IAA, TIAA and TAA contents of both maize- and wheat-DDGS can be predicted from their CP contents with high accuracy. In the second study, the nutritional value of wheat-DDGS without- or with exogenous enzymes for broiler was determined using three experiments. The N-corrected- and apparent metabolisable energy contents (AMEn and AME, respectively) without- or with added admixture of xylanase, amylase and protease (XAP) was determined in experiment 1, true P digestibility without- or with supplemental phytase was determined in experiment 2, whereas the apparent- or standardised ileal digestibility (AID and SID, respectively) of AA without- or with added protease was determined in experiment 3. Birds were fed a nutrient adequate pre-experimental diet from d 1 to 14 post-hatch followed by the dietary treatments from d 14 to 21 in experiment 1 and 2, or from d 25 to 28 in experiment 3, respectively. Each of the 3 experiments was arranged as a randomised complete block design consisting of 7 replicate pens and 3 birds per pen. Six dietary treatments consisting of 3 levels of wheat-DDGS (0, 300 or 600 g/kg of diet) and 2 levels of XAP (0 or 0.25 g/kg) were used in experiment 1. Six diets consisting of 3 levels of wheat-DDGS (200, 400 or 600 g/kg of diet) and 2 levels of phytase (0 or 1000 FTU/kg) were used in experiment 2, whereas four treatments consisting of a nitrogen-free diet (NFD) and an assay diet, both diets without- or with supplemental protease were used in experiment 3. In experiment 1, increasing the level of wheat-DDGS in the basal diet decreased linearly (P < 0.001) dry matter (DM) and energy retention, AME and AMEn. Supplemental XAP tended to improve both the dietary AME (P = 0.059) and AMEn (P = 0.085) values of the diet. The AME value of wheat-DDGS without- or with supplemental XAP was determined to be 15.0 or 15.5 MJ/kg, respectively. Corresponding values for AMEn were 14.0 and 14.5 MJ/kg, respectively. Supplemental XAP did not improve the energy value of wheat-DDGS for broilers. In experiment 2, increasing the level of wheat-DDGS in the diet decreased linearly (P < 0.05) ileal DM digestibility, DM retention and apparent P retention but there was no difference in apparent ileal P digestibility. Except for Fe and Zn at the ileal, and Mn and Zn at the total tract level, increasing the level of wheat-DDGS in the diet increased linearly (P < 0.05) the flow of all other minerals. Flow of minerals at the ileal and total tract level were not different with phytase supplementation. True ileal P digestibility in the wheat-DDGS for broilers was 93.6 or 96% without- or with added phytase, respectively. Corresponding values at the total tract level were 92.4 and 93.5%, respectively. Phytase addition did not improve P utilisation at the ileal or total tract level. In experiment 3, AID ranged from 33% (Asp) to 75% (Pro) without added protease whereas the range was 31% (Asp) to 82% (Pro) with protease supplementation. The AID of Lys was nil regardless of protease supplementation. Supplemental protease improved (P < 0.05) the AID of Arg and Pro and tended to improve (P < 0.10) the AID of Met. Without protease supplementation, SID ranged from 43% (Asp) to 84% (Pro) whereas the range was from 54% (Asp) to 93% (Pro) with added protease. Supplemental protease improved (P < 0.05) the SID of Arg, Leu, Phe, Met, Val and Pro by 21, 14, 13, 26, 13 and 10 percentage points, respectively. It was concluded that wheat-DDGS is a good dietary source of metabolisable energy and P for broilers. The ileal AA digestibility of wheat-DDGS for broilers is quite variable and generally low. Further, the ileal digestibility of some AA in the wheat-DDGS improved with protease supplementation. Using three experiments the third study determined the metabolisable energy content, true P digestibility and retention and AIAAD and SIAAD of wheat-DDGS for turkey. The AMEn and AME content of wheat-DDGS without- or with XAP was determined in experiment 1, the true P digestibility and retention without- or with supplemental phytase was determined in experiment 2, whereas the AIAAD and SIAAD of wheat-DDGS without- or with a protease were determined in experiment 3. Experiment 1 and 2 lasted for 21 days whereas experiment 3 lasted for 28 days. Experimental diets were fed for 7, 5 or 3 d in experiment 1, 2 or 3, respectively. Each of the 3 experiments was arranged as a randomised complete block design consisting of 7 replicate pens and 3 birds per pen. Six dietary treatments consisting of 3 levels of wheat-DDGS (0, 300 or 600 g/kg of diet) and 2 levels of XAP (0 or 0.25 g/kg) were used in experiment 1. Six diets consisting of 3 levels of wheat-DDGS (200, 400 or 600 g/kg of diet) and 2 levels of phytase (0 or 1000 FTU/kg) were used in experiment 2, whereas four diets consisting of a NFD and an assay diet, both diets without- or with supplemental protease were used in experiment 3. In experiment 1, increasing the dietary inclusion of wheat-DDGS from 0 to 600 g/kg decreased linearly (P < 0.05) DM and energy retention. There was wheat-DDGS × XAP interaction (P < 0.05) for dietary AME and AMEn. Dietary AME and AMEn values decreased linearly (P < 0.001) as the level of wheat-DDGS increased in the diets without XAP, whereas there was no effect of increasing wheat-DDGS level on dietary AME or AMEn for the XAP-supplemented diets.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:616468 |
| Date | January 2014 |
| Creators | Adebiyi, Adekunle Olalekan |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/5432/ |
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