Effect of dietary level of maize-and rye distiller dried grains with solubles on nutrient utilization and digesta viscosity in laying hens S . Ś

An experiment on 55 Lohman Brown hens examined the effect of different dietary levels of maizeand rye distillers dried grains with solubles (mDDGS and rDDGS, respectively) on nutrient digestibility, content of metabolizable energy in the diet and balance of nitrogen, calcium, phosphorus, and zinc. Experimental diets were isocaloric and isonitrogenous and contained 0, 5, 10, 15, or 20% mDDGS or rDDGS. Diets with 20% mDDGS or rDDGS were also supplemented with NSPhydrolysing enzymes. It was found that 5, 10 or 15% mDDGS in a diet had no effect on apparent digestibility of nutrients, dietary metabolizable energy content, or balance of N, Ca and Zn; 20% mDDGS decreased the digestibility of crude fat and lowered the level of metabolizable energy in the diet, whereas 15 or 20% rDDGS negatively affected organic matter and crude fat digestibility and the dietary metabolizable energy level. A 15 or 20% inclusion of mDDGS or rDDGS had, however, a positive effect on phosphorus balance. Addition of feed enzymes increased nutrient utilization in diets containing 20% DDGS.


INTRODUCTION
Distillers dried grains with solubles (DDGS) is a by-product of ethanol production.Growing interest in fuel ethanol production will lead to increases in the amounts of DDGS available to the feed industry.In our previous studies it was concluded that maize-and rye DDGS (mDDGS and rDDGS) are useful feed ingredients for laying hens (Świątkiewicz and Koreleski, 2006a,b).Dietary levels up to 15% mDDGS and 10% rDDGS did not unfavourably affect laying performance, egg quality, and fl avour of boiled eggs when were used in hens from 26 to 68 weeks of age.Inclusion of mDDGS in the diet positively infl uenced egg yolk colour.High dietary levels of DDGS (15% rDDGS and 20% mDDGS) did, however, negatively affect laying rate and feed conversion.Similar conclusions on the use of maize DDGS in laying hen diets were drawn by Lumkins et al. (2005) and Roberson et al. (2005).
During fermentation, cereal starch is converted to ethanol and CO 2 and the concentration of the remaining nutrients in DDGS increases 2-3-fold, so DDGS contains high levels of non-starch polysaccharides (NSP).For this reason, performance reduction in hens fed diets with high DDGS contents could be a result of decreased nutrient utilization.The aim of our experiment was to determine the effect of different levels of mDDGS or rDDGS in diets for laying hens on nutrient digestibility, metabolizable energy content, balance of nitrogen, calcium, phosphorus, zinc, and on digesta viscosity.

MATERIAL AND METHODS
The experiment was carried out on 55 Lohman Brown laying hens at 39 weeks of age.The experimental design consisted of 11 treatments with 5 replicates (birds) each.Hens were offered water and feed ad libitum and were exposed to a 14 L:10 D lighting schedule, with the dark period at night.
All experimental diets were isocaloric and isonitrogenous and contained different levels (0, 5, 10, 15 or 20 %) of mDDGS or rDDGS.The diets with the highest level of mDDGS or rDDGS were also supplemented with NSP-hydrolysing enzymes (Table 1).The experimental diets were fed to hens before the beginning of the balance study (from 26 weeks of age).
At 39 weeks of age the hens were divided into individual balance cages.After a one-week adaptation period, total collection of excreta was carried out during 5 days and feed consumption for each hen was recorded.Excreta were stored in plastic bags at -20ºC for three weeks and after thawing were dried at 50ºC to a constant weight, weighed, and fi nely ground.The proximate composition of diets and excreta was analysed by standard procedures (AOAC, 1990), gross energy, by   Ronozyme WX (endo-1,4-β-xylanase activity of 1000 FXU/g) and Ronozyme VP (endo-1,3(4) -β-glucanase activity of 50 FBG/g and also pentozanase, hemicellulase and pectinase activity).Each preparation was added to the diet in amount of 200 mg • kg -1 ; 3 calculated according to European Table (1989) as a sum of ME content of components; 4 calculated according to the chemical composition of feed components; 5 analysed using an adiabatic oxygen bomb calorimeter, total phosphorus, calorimetrically by the molibdeno-vanadate method (AOAC, 1990), Ca and Zn, by fl ame atomic absorption spectrophotometry (AOAC, 1990).The total tract apparent digestibility of organic matter, crude fat and nitrogen-free extractives, metabolizity coeffi cient for apparent metabolizable energy corrected for nitrogen retention, and balances of nitrogen, calcium, phosphorus and zinc were calculated using the obtained data.
After completion of the balance trial, 3 hens each from groups I, III, IV, V, VI, VIII, X and XI were killed by cervical dislocation.Whole intestines were removed and total intestinal contents from the upper parts of the intestines (between the gizzard and Meckel's diverticulum) were collected and centrifuged at 5000 g for 10 min.Viscosity of the supernatant was measured on a capillary viscometer at 37ºC.
In DDGS samples the contents of simple sugars (arabinose, xylose, mannose, galactose and glucose) in NSP were determined using a gas HP 5890 chromatograph (Englyst and Cummings, 1984).Total and insoluble β-glucans were analysed using the Aman and Graham procedure (1987).
Data were subjected to one-way analysis of variance.The signifi cance of differences between means was determined by Duncan's multiple range test with the use of the Statistica 5.0 PL software package.Two statistical analyses were performed separately for evaluation of the effects of mDDGS and rDDGS on the studied parameters.
The average laying rate during the balance assay was 96.5%, daily mass of eggs, 59.5 g/hen/day, feed conversion for 1 kg of eggs, 1.97 kg, and feed conversion for 1 egg, 121 g of feed (Table 2).Dietary inclusion levels of mDDGS had no effect on these parameters, but in hens fed the diet with 20% rDDGS, worsening of laying performance and feed conversion was noted (P≤0.05).The results of our previous experiments (Świątkiewicz and Koreleski, 2006 a,b), obtained for  the whole laying cycle (26-68 weeks of age) show that the decrease in laying performance could also have been caused by 20% mDDGS and 15% rDDGS in the diet, especially in the second phase of the laying cycle.Lumpkins et al. (2005) found no signifi cant difference in laying performance when hens were fed diets containing 0 or 15% mDDGS.
The results from the balance assay are summarized in Table 3.There was no difference between treatments in apparent digestibility of nitrogen-free extractives in total digestive tract.The dietary inclusion level of mDDGS had no effect on organic matter digestibility, but in the treatment with 20% mDDGS, a decrease in crude fat digestibility and metabolizable energy of the diet in comparison with the control group was found (P≤0.05).In contrast with our fi ndings, Spiehs et al. (1999) reported an increase in metabolizable energy when 10 or 20% mDDGS was included in a pig diet, but in a later experiment (Spiehs et al., 2000), a dietary level of 20% mDDGS had no effect on energy utilization in pigs.
In hens fed the diet with 20% rDDGS, the digestibility of organic matter was signifi cantly reduced as compared with the control group (Table 3).A decrease in fat digestibility and in the percentage of AME N in gross energy was observed when the diet contained 15 or 20% rDDGS (P≤0.05).In an experiment on growing pigs, Nyachoti et al. (2005) showed that wheat DDGS had a signifi cantly lower digestibility of dry matter, gross energy and crude protein as compared with wheat.This may correspond with the decrease in nutrient digestibility in treatments with a high dietary level of rDDGS observed in our experiment.
Addition of NSP hydrolyzing enzymes to the diet positively affected nutrient utilization and there was no difference in nutrient digestibility and metabolizability coeffi cients between the control treatment and hens fed diets with 20% mDDGS or rDDGS supplemented with the enzyme preparation (Table 3).Dietary inclusion levels of mDDGS or rDDGS did not signifi cantly affect intestinal digesta viscosity, however, viscosity was numerically higher in treatments with 20% DDGS than in the control group.Supplementation of 20% DDGS diets with enzymes numerically decreased digesta viscosity, but this effect was not confi rmed statistically (Table 3).
The results of chemical analysis of NSP fractions in DDGS and the positive effect of enzymes could suggest that the main reason for reduced nutrient digestibility of diets with high levels of DDGS is the considerable amount of non-starch polysaccharides in this by-product.Similar results were obtained by Pan et al. (1998) andLazaro et al. (2003), who reported that supplementation of diets containing high levels of cereals rich in NSP with NSP-hydrolysing enzymes had a positive infl uence on dry matter and fat digestibility, dietary AME N content and digesta viscosity.Jaroni et al. (1999) found, however, no benefi cial effect on digesta viscosity or protein and fat digestibility in hens when diets containing 8 or 16% of wheat middlings were supplemented with xylanase.Smulikowska et al.N -for apparent metabolizable energy corrected for nitrogen retention (1997) found that NSP-hydrolysing enzymes decreased intestinal digesta viscosity of hens fed a diet with 30% whole rye, but the enzyme was not effective when ground rye was used.Supplementation of a diet containing 30% brewer's dried grains with xylanase positively affected performance and nutrient utilization in broilers (Iyayi and Davies, 2005).
The results of the balance study did not show any signifi cant effect of dietary inclusion level of DDGS or supplementation of the diet containing 20% DDGS with NSP-hydrolizing enzymes on retention (as % of intake) and excretion of N, Ca and Zn (Table 3).In diets with 0, 5, 10, 15 and 20% DDGS, the balances of N, Ca and Zn were similar.In contrast with our results, Spiehs et al. (1999) reported that inclusion of 10 or 20% mDDGS in diets for growing and fi nishing swine tended to increase N excretion.In another study, these authors showed that inclusion of 20% mDDGS in the diet had no effect on nitrogen retention (as % of N intake), but increased N excretion (Spiehs et al., 2000).
There was a signifi cant infl uence of dietary treatment on P balance (Table 3).Dietary inclusion levels of 15 and 20% mDDGS or 20% rDDGS decreased P excretion and positively affected P retention (P≤0.05).It could be speculated, based on literature data, that fermentation increases P availability in DDGS, possibly through synthesis of microbial phytase (Lumpkins and Batal, 2005).The higher P availability of diets with 15 and 20% DDGS could be important due to environmental concerns and for economic reasons (phosphorus is an expensive component of poultry diets).Our results correspond with data from experiments on pigs (Spiehs et al., 1999), where inclusion of 10 or 20% DDGS in a maize-soyabean based diet increased P retention (as % of P intake) and decreased P excretion.In a later experiment by Spiehs et al. (2000), inclusion of DDGS into a diet had no effect on P retention, but urinary P excretion in pigs fed a diet with 20% mDDGS tended to decrease as compared with a control group (P≤0.15).Apparent total tract digestibility of P in DDGS fed to growing pigs amounted to 59.1% and was signifi cantly greater than in maize (Pedersen et al., 2007).Whitney et al. (2001) suggested that DDGS could be an excellent source of available P for growing swine.They showed in slope-ratio analysis, that P availability in mDGGS was 87.5 and 92.2%, based on P excretion and P retention, respectively, as compared with P availability from dicalcium phosphate.In a study with broiler chickens, Martinez-Amezcua et al. (2004) reported that relative P availability in DDGS was higher than the value estimated from NRC (1994), but there was substantial variability in P availability among different DDGS samples.In a later study, Martinez-Amezcua and Parsons (2007) showed that P bioavailability in DDGS (relative to P in KH 2 PO 4 ) increases with the duration of heating DDGS.
Composition and nutrient content of experimental diets, g • kg - fed diets with mDDGS and rDDGS values in the same rows with different letters differ signifi cantly at P≤0.05

Table 3 .
Effect of maize distillers dried grains with solubles (mDDGS) and rye distillers dried grains with solubles (rDDGS) on nutrient digestibility, metabolizable energy of diet, viscosity of intestinal content and balance of N, Ca,

Table 2 .
Effect of maize distillers dried grains with solubles (mDDGS) and rye distillers dried grains with solubles (rDDGS) on performance indi-