The use of alternative feed ingredients in poultry diets can be an interesting choice from an economically standpoint. But the nutritional value of the alternative ingredients should be kept in mind. Particularly the presence of anti-nutritive factors.
The poultry industry relies on a few major ingredients for feed formulation. Cereal grains are the principal sources of energy in poultry diets, whereas grain legumes and oilseed cakes are the main sources of protein. Wheat, barley, triticale and sorghum are the key cereal grains and soybean meal, canola meal, peas, lupin and beans are important protein sources. The industry has always been inclined to use the cheapest ingredients to maximise profit. As such ingredients do not always support optimum productivity, they are included in small amounts or efforts are made to improve their nutritive value. Despite these limitations, the use of alternative feed ingredients is increasing due to a variety of factors. Conventional feed ingredients are more expensive and are not readily available to all producers at all locations. Adverse climatic conditions and the use of feed ingredients in the biofuel industry have stimulated the search for alternative feed ingredients for poultry. The biofuel industry generates by-products such as distillers dried grains and solubles (DDGS), that not only need to be disposed of but are becoming core feed ingredients due to the shortage and cost of conventional ingredients. All over the world, but more so in areas experiencing feed shortage, alternative ingredients are investigated with the aim of replacing all or some conventional ingredients. With alternative diets, poultry productivity is often poor due to deficiencies in nutrients such as amino acids and minerals, imbalances in energy to protein ratios or anti-nutritive factors like non-starch polysaccharides (NSPs), polyphenols or phytic acid. Researchers at the University of New England (UNE), Australia, have conducted research in recent years to find out how to improve the quality of those ingredients.
Cassava and cassava by-products
The use of cassava roots and other parts of the plant as an animal feed is traditional in Africa and Asia. Recently, cassava production began on a large scale in northern Queensland to support feedlots. There is a possibility that this industry could diversify into non-ruminant feed production in the future. In Thailand, the third largest producer of cassava, almost all cassava is used for animal feed and starch production. The latter industry yields a fibrous by-product, cassava pulp, which has been used for feeding cattle and pigs. Researchers at UNE tested this product as a replacement for maize in diets for layers and established that 15% cassava pulp can be included in layer diets without detrimental effects on egg production and egg quality, except yolk colour, which was paler for diets containing cassava pulp. Supplementation with products with xylanase and phytase activities (Danisco Animal Nutrition, UK) enabled an increase in cassava pulp inclusion to 20% in diets for layers and maintained egg production at the same level as the maize control diet. In another study, the metabolisable energy (ME), net energy of production (NEp) and heat production of broiler chickens raised on starter diets containing cassava pulp and microbial enzymes was measured. The ME content of the diets and the intake of ME and protein were reduced by increasing levels of the by-product in the diet but were improved by the enzyme supplements. NEp and heat production were reduced by cassava pulp but were increased by supplementation with microbial enzymes. The efficiency of utilisation of ME for energy and fat retention was reduced by cassava pulp but the efficiency of utilisation of ME for protein retention was increased. Enzyme supplementation had no effect on these values. Feed intake to 35 days of age was reduced (P<0.05) by inclusion of 10% cassava pulp but feed intake recovered as inclusion level rose to 15%; it was not affected by microbial enzyme supplementation at either level. Overall, there is scope for the use of cassava pulp in diets for layers and broiler chickens at low levels, but this would require supplementation with microbial enzymes and yolk pigments. It is likely that the Australian poultry industry will use more cassava chips and pellets in future and less cassava pulp.
Triticale for poultry
The UNE has conducted research on triticale for several years. A major limitation to increased exploitation of triticale for poultry feeding in Australia is a dearth of published data. The energy value of triticale was assessed as part of a larger project, the Premium Grains for Livestock programme, which included a wide range of grains. Ravindran and others (2005) reported lower amino acid digestibility for triticale than for wheat and maize. In another study, Hughes and Van Barneveld reported that pre-germination of triticale, wheat and sorghum did not improve the apparent ME (AME) of triticale, wheat or sorghum. Triticale holds promise as a replacement for wheat due to its tolerance of drought and poor soils. This advantage would be extended if the nutritive value of the crop were equal to or better than that of wheat. Most of the triticale varieties developed at the UNE are higher in crude protein than wheat, ranging from 123.91 to 138.64 g/ kg DM. The in vitro digestibility of triticale starch and protein varies between 41.1% and 87.8%. A feeding experiment was concluded to define the AME of diets containing 72–75% triticale and the NEp and HP of broiler chickens raised on diets in which triticale completely replaced wheat. The ME intake and NEp from 1 to 22 days were lower (P < 0.05) on the wheat-based diet than on the Bogong-, Jackie-, Tobrukand maize-based diets, and diets containing the other two varieties of triticale (Canobolas and Endeavour) did not differ from the wheat-based diet. Chickens fed triticale-based diets retained more (P<0.05) energy in the form of protein and fat than those fed the wheat based diet. These diets may promote protein accretion and growth on the one hand while increasing meat fat content on the other hand. The results of the study show that the utilisation of energy in triticale is not poorer than that in conventional ingredients such as wheat and maize. This study also shows that energy deposition as protein is greater than energy deposition as fat for triticale-based diets. This may affect the quality of meat produced using such diets.
Sorghum distillers dried grains
DDGS will remain in the forefront of nutrition research for some time as the major cereal producers, particularly those in the US, intensify efforts to reduce dependence on petroleum. Most research on DDGS has focused on maize DDGS produced in North America. In Australia, most DDGS is derived from sorghum or wheat and has not been used to a large extent by poultry producers. The UNE initiated a project aimed at improving the nutritive value of sorghum DDGS for poultry. In preliminary tests, six DDGS samples were obtained from the Shoalhaven Starches Plant in New South Wales to investigate variability between batches. The samples generally contained appropriate amounts of essential amino acids and had a high content of threonine (10.1–11.4 g/kg). Two feeding trials were conducted in which microbial enzymes were supplemented. In the first experiment, 42 day-old male broiler chicks were used in a 4×2 factorial design. Four levels of DDGS inclusion (0, 100, 200 or 300 g/kg) with or without a xylanase enzyme (Ronozyme WX, 1,000 fungal Xylanase units per gramme, DSM, Heerlen, the Netherlands) were fed for 21 days in starter diets and then from 21 days to 35 days of age in finisher diets. Compared with the control diet, feed intake was increased (P<0.001) by DDGS during the first three weeks and during the entire period of the study. Body weight gain was not affected by DDGS or xylanase. Feed conversion ratio (FCR) deteriorated (P 0.05) as the level of DDGS increased during the first three weeks of feeding. Analysis of total NSPs showed that increasing the level of DDGS to 30% reduced the concentrations of rhamnose and fucose in ileal digesta. The concentrations of arabinose, ribose and total NSP in ileal digesta were not affected by DDGS level, whereas levels of glucose and xylose in ileal digesta rose as DDGS level rose to 30%. Xylanase supplementation increased xylose concentration in the digesta, but only at the 30% DDGS level.
More than 817 million tonnes of maize were produced worldwide in 2009, compared with 682 million tonnes of wheat. The production of maize is increasing in non-tropical areas of the world, in southern Europe and parts of temperate South America. This necessitates early harvest at a relatively high moisture content and artificial drying. Artificial drying of high-moisture grain is fraught with problems. The starch quality, particularly the ratio of amylopectin to amylose, may be affected, reducing the nutritive value of the grain. Amylopectin is the most digestible starch fraction. Recently, the UNE investigated changes in the physical quality and nutrient composition of high-moisture maize grain subjected to artificial drying. This was followed by a feeding trial in which microbial enzymes (carbohydrase, protease and phytase) were included in the diet. Maize cobs with the grain attached were harvested at relatively high moisture content (23%) from in northern New South Wales and dried in the sun or in a forced-draught oven at 80, 90 or 100°C for 24 hours. The in vitro digestibility of DM, starch and crude protein were determined according to the method of Babinszky (1990) and the structure of grain was assessed using electron microscopy and nuclear magnetic resonance techniques. The scanning electron microscope showed some shrinkage of starch granules as a consequence of drying temperature. The in vitro digestibility of DM was improved by artificial drying but starch digestibility was reduced.
The effects of feeding diets containing sundried or artificially dried high-moisture maize grain supplemented with microbial enzymes on growth performance, visceral organ mass, tissue protein content, enzyme activity and gut development were investigated in a broiler growth trial. Feed intake up to 21 days of age was decreased by oven drying whereas microbial enzymes increased feed intake compared with non-enzyme diets (881.1 vs 817.2 g). Feed intake was highest for sundried grain. There was no effect of drying temperature or enzymes on feed intake at seven days of age. Up to 21 days of age, body weight decreased as grain drying temperature increased and supplementation with enzymes improved weight only for diets containing sundried grains and grains dried at 90 °C. Body weight was higher (P<0.01) for the enzyme-supplemented diets than for diets that did not contain enzymes (638 vs 547 g). FCR at this age improved as grain drying temperature increased and was improved by enzyme supplementation (1.48 vs 1.62). There was an increase in the relative weight of the small intestine and liver with an increase in grain drying temperature at 21 days of age enzyme supplementation did not change the relative weights of these organs. Grain drying treatment, but not enzyme supplementation, increased the activities of alkaline phosphatase (on day seven) and maltase and sucrase (on day seven and day 21, respectively). The ileal digestibilities of gross energy, protein and starch were not changed by grain drying temperature or enzyme supplementation. This contradicts the report of Iji and others, (2004) in which similar enzymes improved the body weight of broiler chicks fed diets based on sundried maize. The enzymes were also more effective with sundried maize than with artificially dried maize. No clear reason could be adduced for this disparity, but changes in starch quality as a result of heating could have reduced the overall quality of the grain and its response to enzyme supplementation.The concentrations of formic and acetic acids in the ileum and propionic and valeric acids in the caeca were significantly increased by an increase in grain drying temperature but there was no effect of enzyme supplementation on the concentrations of these acids. The populations of lactic acid bacteria and lactobacilli in ileal digesta were decreased by enzyme supplementation but were not affected by drying temperature. The total anaerobic bacteria count in caecal digesta was increased by microbial enzymes (8.1 vs 7.8 log10 colony-forming units per gram of digesta). The number of lactic acid bacteria was increased by increased grain drying temperature. The response of microbial populations to changes in the quality of grain in the diet has not been studied previously. Concentrations of short-chain fatty acids in the upper small intestine of broiler chickens were increased by diets high in low-AME wheat. This may be indicative of an increase in microbial populations responsible for the fermentation of fibre. In the current study, diets based on sundried maize or maize dried at 90°C gave better responses than maize that was artificially dried at other temperatures. There was a positive response to microbial enzymes.
The increased use of alternative ingredients has increased the demand for microbial enzyme supplements. The results of a series of studies recently completed or ongoing at the University of New England, Australia, suggest that the nutritive value of such ingredients can be improved through supplementation with microbial enzymes. As it is likely that such ingredients will be increasingly used with enzyme supplementation and other treatments, it is important to identify the anti-nutritive factors in alternative ingredients and develop the best enzyme combinations for diets that contain these ingredients. AAF References are available on request.This article has been edited from the paper ‘Improving the nutritive value of alternative feed ingredients for poultry’, by P.A. Iji, M.M. Bhuiyan, N. Chauynarong, M.R. Barekatain and A.P. Widodo (University of New England). It was presented at the 2011 symposium ‘Recent Advances in Animal Nutrition’ in Australia.
Article issued in AllAboutFeed 21.1
This article has been edited from the paper ‘Improving the nutritive value of alternative feed ingredients for poultry’, by P.A. Iji, M.M. Bhuiyan, N. Chauynarong, M.R. Barekatain and A.P. Widodo (University of New England). It was presented at the 2011 symposium ‘Recent Advances in Animal Nutrition’ in Australia.
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