APSS 2013 Proceedings - The University of Sydney

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Aust. Poult. Sci. Symp. 2013.....24 DOES PELLETING IMPROVE NUTRIENT DIGESTIBILITY AND ENERGY UTILISATION IN BROILERS? M.R. ABDOLLAHI 1 and V. RAVINDRAN 1 Summary The true impact of pelleting on the utilisation of nutrients in broiler diets has not been clearly delineated due to the pronounced effect of pelleting on broiler performance. It appears that the better growth responses achieved by pellet feeding, compared to mash diets, are obtained at the expense of utilisation of nutrients and energy. Possible negative effects on nutrient utilisation are compensated by increased feed intake and the resultant high nutrient intake in pellet-fed broilers. I. INTRODUCTION It is well accepted that offering feed to broilers in pellet form enhances the economics of production by enhancing growth performance and feed efficiency. Although it is generally believed that pelleting improves nutrient digestibility, there is little published evidence to support this belief. On the contrary, some reports suggest that pelleting may decrease nutrient utilisation under some conditions. Limited published data available on the effect of pelleting on nutrient utilisation is reviewed in this paper. II. EFFECTS ON STARCH DIGESTIBILITY Since gelatinisation increases the access of starch to enzymatic degradation, starch digestibility may be expected to be increased in pelleted diets. However, the extent of starch gelatinisation that occurs during pelleting is generally small and is probably of modest importance (Svihus et al., 2004; Zimonja et al., 2008). Svihus (2001) reported that high starch digestibility usually coincides with mash feeding, whereas low starch digestibility is associated with feeding cold-pelleted diets. In this study, apparent ileal starch digestibility coefficients of cold-pelleted diets containing high levels of four varieties of wheat was of less than 0.83. It was suggested that starch digestibility of wheat-based diets is negatively correlated to feed intake. Based on a significant increase in starch digestibility when a wheatbased diet was diluted with cellulose, Svihus and Hetland (2001) speculated that an overload of wheat starch in the small intestine, due to feed over-consumption, is the major cause of low starch digestibility. Significant decreases in starch digestibility of wheat-based diets, from 0.959 in mash diets to 0.842 and 0.834 in diets pelleted at 60 and 90 ºC, respectively, in broilers due to pelleting have been reported by Abdollahi et al. (2011). Selle et al. (2012) found that pelleting had no effect on the ileal starch digestibility of sorghum-based diets (Table 1). These limited data suggest that pelleting is not beneficial for starch digestibility and may even decrease starch digestibility as a result of high feed intake, at least in wheatbased diets. III. EFFECTS ON PROTEIN DIGESTIBILITY Limited feed-processing experiments have been conducted to assess whether proteins may become more digestible as a consequence of feed processing. Carré et al. (1991) did not find any increase in protein digestibility in broiler chickens as a result of pelleting. Duodu et al. 1 Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North 4442, New Zealand. M.Abdollahi@massey.ac.nz 126
Aust. Poult. Sci. Symp. 2013.....24 (2002) reported that cooking (10 min at approximately 95 ºC) reduced in vitro protein digestibility of sorghum, but not of maize. The poorer protein digestibility of cooked sorghum was explained by the formation of enzyme-resistant disulphide-bonded oligomeric proteins that occur to a greater extent in sorghum than in maize. It was also suggested that pericarp components, germ, endosperm cell walls, and gelatinised starch could be possible factors limiting protein digestibility in sorghum. Selle et al. (2010) suggested that steampelleting of sorghum-based diets at temperatures above 90 ºC may provide sufficient ‘moistheat’ to form disulphide linkages in kafirin and, compromise protein and starch digestibility in sorghum. Abdollahi et al. (2011) reported lower nitrogen digestibility in wheat-based pellet diets (0.836 and 0.822 in diets pelleted at 60 and 90 ºC, respectively) compared to mash diets (0.847) (Table 1). Thus, it is reasonable to assume even if pelleting influences protein digestibility, it may not be a positive effect. However, Selle et al. (2012) showed that pelleting of sorghum-based diets had no effect on nitrogen digestibility, but depressed nitrogen retention coefficient in broilers by an average of 9.1% from 0.606 in mash diets to 0.551 in intact pellets (Table 1). The depression in nitrogen retention was partly attributed to the pelleting inducing the formation of disulfide linkages. These researchers suggested further studies to investigate the possibility of the compromising effect of pelleting on the utilisation of protein after digestion and absorption. IV. EFFECTS ON ENERGY UTILISATION It has been reported by Svihus et al. (2004) that pelleting increased the apparent metabolisable energy (AME) of wheat-based diets from 11.6 to 11.8 MJ/kg. However, the increase in AME was not associated with improvements in starch digestibility. In contrast, Amerah et al. (2007) reported negative effect of pelleting on nitrogen-corrected AME (AMEn) of a wheat-based diet. In their study, pelleting reduced the AMEn of the diet from 12.5 to 11.8 MJ/kg (Table 1). Abdollahi et al. (2011) also reported a decrease in AME of wheat-based diets from 14.10 to 13.75 and 13.42 MJ/kg due to pelleting at 60 and 90 ºC, respectively (Table 1). The positive effect of pelleting on feed efficiency has been consistently observed (Jensen et al., 1962; Latshaw and Moritz, 2009) and is due partly to the reduction in feed energy used for maintenance. McKinney and Teeter (2004) reported that pelleting contributed 0.78 MJ MEn/kg diet at 100% pellets (no fines), with this value decreasing with increasing proportions of fines to pellets, but still contributing 0.32 MJ MEn/kg for 20% pellets. Skinner-Noble et al. (2005) reported a contribution of 0.63 MJ MEn/kg diet from pellets compared to a mash diet. A recent study by Latshaw and Moritz (2009) showed that broilers fed pellets had lower heat increment and utilised feed energy more efficiently for productive purposes than those fed mash. V. NUTRIENT INTAKE OF PELLET-FED BIRDS A number of factors are considered as motivations behind the pelleting of broiler feeds. Feed intake is the major factor driving body weight gain and an increased feed intake is the primary motivation for pelleting broiler diets (Svihus et al., 2004). Nutrient and energy intakes calculated from some of the previously discussed data on nutrient digestibility and energy utilisation are also presented in Table 1. In general, increased feed intake resulted in higher intakes of digestible protein, digestible starch and AME, and retained more protein in pellet-fed birds compared to mash-fed birds. It is noteworthy that the higher nutrient and energy intakes in pellet diets have been achieved while having lower nutrient digestibility and AME content than mash diets. This highlights the importance of feed intake when broilers are fed pellet diets. 127
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24 th ANNUAL AUSTRALIAN POULTRY SCI
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AUSTRALIAN POULTRY SCIENCE SYMPOSIU
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AUSTRALIAN POULTRY AWARD The Austra
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CONTENTS THE IMPORTANCE OF THE POUL
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SHORT COMMUNICATION SESSION # 1: (c
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HOT TOPIC 2: EMERGING DISEASES AND
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AUTHOR INDEX Name Page(s) Email Add
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Klein-Hessling, H 207 hkleinhesslin
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Van de Wouw, A 247 nnet.vandewouw@w
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