Effect on Growth Performance

The inclusion of maize-DDGS in poultry diets is not new (Matterson et al., 1966; Morrison, 1954; Waldroup et al., 1981; Parson et al., 1983), however, majority of the DDGS described in growth performance and digestibility studies in poultry and swine before the last decade were mostly from the brewing industry. The DDGS produced by the brewing industry may however be different in chemical composition to the DDGS produced by modern bioethanol facilities due to improved fermentation techniques. Morrison (1954) observed that up to 8%

maize-DDGS may be included in practical broiler chick diet without detrimental effects on

38 body weight. In addition, the author also reported that including 10% maize-DDGS in layer hen diets did not cause a reduction in egg production. In another study, up-to 25% maize-DDGS was included in nutritionally-adequate broiler diets without causing a reduction in body weight or feed intake (Waldroup et al., 1981). Further studies using maize-DDGS by Parsons et al. (1983), proposed that up-to 40% of SBM protein can be replaced by maize-DDGS as long as the dietary Lys content is adequate.

There is a general trend that growth performance is depressed as the quantity of DDGS in the diet is increased. The decline in growth performance as the level of maize-DDGS in the diet is increased may be due to the inefficiency of poultry at utilising dietary fibre. Stated differently, along with other nutrients the crude fibre composition of DDGS is increased about 3-folds by fermentation. As such, high inclusion levels of DDGS may increase dietary fibre content which in turn may impede nutrient digestibility. Thacker and Widyaratne (2007) evaluated the inclusion of wheat-DDGS in broiler chick diets at a rate of 0, 5, 10, 15 and 20%. In that study, there were no differences in body weight gain (BWG), feed intake and feed conversion ratio (FCR) in all the dietary treatments compared with the controls. However, because there was a high mortality at 20% DDGS inclusion, the authors recommended that wheat-DDGS be incorporated at 15% provided that the low energy and Lys contents of wheat-DDGS are compensated for during diet formulation. Similarly, Loar et al. (2010) reported no differences in the final body weight (FBW), feed intake and FCR of broilers fed 0 or 8% maize-DDGS in their diets during the starter period.

Wang et al. (2007a) observed that broilers fed 15% maize-DDGS did not differ from control in body weight, feed intake, and FCR at 42 days of age; however, 30% inclusion of maize-DDGS reduced feed efficiency without any effect on feed intake or BWG. In another study by the same authors (Wang et al., 2007b) it was noted that 15 to 20% maize-DDGS may be incorporated into broiler diets formulated on digestible AA without detrimental effects on bird performance. Shim et al. (2011) observed greater BWG in the starter period of broilers fed 24% maize-DDGS against the control.

Lumpkins et al. (2004) recommended an optimum inclusion rate of maize-DDGS at 9% in broiler starter diets and 12 to 15% in the grower to finisher period because above these levels, maize-DDGS depressed growth performance. In Hoskova et al. (2010) study, including 0 or 25% wheat-DDGS in broiler diets from 12 to 35 days of age produced similar feed intake and FCR but the treatment containing 0% wheat-DDGS produced superior growth performance.

Vilarino et al. (2007) observed improvement in FCR for broilers fed either 10 or 20% wheat-DDGS from day old to 10 days of age compared with controls (0% wheat-wheat-DDGS), but feed

39 intake and final body weight at 37 days of age reduced as the level of wheat-DDGS increased.

Similarly, Richer et al. (2006) observed a reduction in BWG and feed intake of broilers at the finisher phase as the level of wheat-DDGS increased to 20% in the diet. Lukasiewicz et al.

(2009) observed improvement in FCR for broilers receiving 7%, 9.5% and 9.5% wheat-DDGS during the starter, grower and finisher periods respectively, however mean BWG was consistently higher in the control groups (0% DDGS) and also in males fed wheat-DDGS compared to females. Lukasiewicz et al. (2009) further noted that the inclusion of wheat-DDGS in the diet for broilers increased the number of beneficial micro-organisms in the gut (there was a decline in caecal population of Enterobacteriaceae).

According to Potter (1966), if Lys and ME content of feed are appropriately balanced, up to 20% maize-DDGS could be fed to turkey without any detrimental effect on body weight or FCR. Roberson (2003) fed diets formulated on digestible AA basis and including between 0 and 27% maize-DDGS to female turkey, the authors observed a linear decrease in body weight as the level of maize-DDGS increased in the diet as well as a linear increase in FCR.

Because there was an increase in the incidence of pendulous crop as the level of maize-DDGS increased (with incidence highest at 18 to 27% inclusion levels) in that study, the authors recommended that maize-DDGS be used at no more than 10% during the grower/finishing period in female turkey.

Extensive feeding trials by Noll et al. (2002; 2003ab) in turkey investigated the possibility of using maize-DDGS in grower/finishing diets of heavy toms receiving diets formulated on digestible AA basis. In those studies there were no differences observed in live performance of turkey relative to body weight and FCR at 10% inclusion rate of maize-DDGS. In another study, 15 and 20% levels of maize-DDGS in turkey diets resulted in performance similar to the control (Noll, 2004), however 20% inclusion of maize-DDGS depressed FBW at 19 weeks of age in a similar but subsequent study by the same authors (Noll et al., 2005). Further studies by Noll et al. (2009) showed that body weight was greater at 5 weeks of age in turkey fed on diets containing 10, 20 and 30% maize-DDGS compared with turkey fed diets with no maize-DDGS.

Because exogenous enzymes in poultry diets can help promote growth, efficiency of nutrient utilisation, and nutrient excretion, some authors have assessed their benefits in poultry diets containing DDGS. Slominski (2010) observed growth performance response of broilers to feeding a blend of maize-DDGS and wheat-DDGS with or without enzyme supplementation.

The authors noted that 10% inclusion of the maize-/wheat-DDGS blend supported growth performance similar to the control diet (0% DDGS) in the absence of enzyme and that in the

40 presence of enzyme, 15% DDGS level supported growth similar to the control. In Olukosi et al. (2010) study, inclusion of 10% maize-DDGS in broiler diets supplemented with an admixture of phytase, xylanase, amylase and protease enzymes produced superior BWG, feed intake and feed efficiency at 3 weeks of age compared with diets without maize-DDGS or supplemental enzymes.

Due to the potential anti-nutritive effects of NSP in DDGS, some authors have studied the effect of processing techniques to reduce the NSP level. Oryschak et al. (2010) examined the use of extruded (physical disruption of cell wall and reduction in molecular weight of substrate) and non-extruded maize-DDGS and wheat-DDGS between 0 to 30% in broiler diet.

The authors recommended an inclusion rate of no more than 10% for either maize-DDGS or wheat-DDGS with or without extrusion because above this level growth performance responses were depressed. Overall, it was generally consistent in the literature that increasing the inclusion level of maize- or wheat-DDGS in broiler and turkey diets compromised growth performance. It was also noted that the maize- or wheat-DDGS inclusion rates at which a decline in growth performance was noted also varied among studies. Although differences in the nutritional quality of the DDGS used may be responsible for the variations in growth performance response reported among studies, factors such as the chemical characteristics of the diet used, breed and age of bird and enviromental conditions may also affect bird performance. On the other hand, there is possibility that a diet containing DDGS that is formulated using digestible nutrient values will support growth performance and further benefits may be derived by supplementing such diet with exogenous enzymes.