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An experiment was conducted to investigate the effects of using two different enzyme substrates on the performance of broilers fed peeled cassava root meal (PCRM), in a 3 x 3 factorial arrangement in a completely randomized design experiment. One hundred and eighty-nine broiler chicks aged 14 days were assigned to nine experimental diets where PCRM replaced maize at 0, 50 and 75 percent levels. The diets were formulated to be roughly isonitrogenous and isoenergetic containing starter (15-36 days; 24% CP, 2800 Kcal/kg-1 ME) and finisher (37-58 days; 21% CP, 2800 Kcal/kg-1 ME) and 200ppm of enzyme (Nutrase xyla and Roxazyme G) were added to the diets. Results indicated that Nutrase xyla and Roxazyme G supplementation increased ADFI in the starter and finisher phases at all levels of PCRM
inclusion (P<0.05).

The effect of nutrase xyla and roxazyme G supplementation on FCR was positvely significant in the finisher phase (P<0.05). Roxazyme G supplemented diet at 50% PCRM had the best least cost value in terms of feed cost per kg weight gain. There was an increase in dressed weight percentage in nutrase xyla and roxazyme G supplemented diets at 50% PCRM (P<0.05). Nutrase xyla supplemented diet had increase
significant effect (P<0.05) on dry matter and metabolizable energy retention.

Nutrase xyla and roxazyme G supplemented diets had no significant effect (P>0.05) on edible organs (heart and gizzard). It is concluded that enzyme supplementation on PCRM-based diet had tremendous beneficial effect on production parameters.




A serious competition exists between the feed industry and other channels in the food chain (especially man) over conventional feed ingredients such as maize and soyabean. This has resulted in the high cost and scarcity of these conventional feedstuffs. Poultry feed producers are thus faced with the task of finding alternative feedstuffs that will not compromise quality.

The search for such alternatives has exercised Animal Nutritionists in Nigeria for over a decade (Onyimonyi and Okeke, 2002; Onyimonyi and
Onukwufor, 2003; Oke et al., 2005; Onyimonyi and Okeke, 2005; Tuleun et al., 2005). Cassava, has been used as an alternative energy source and its inclusion in diets for poultry has been extensively studied (Tewe and Egbunike 1992, Eruvbetine 1995, Adegbola, 1977). Nigerian cassava production is by far the largest in the world; a third more than production in Brazil and almost double the production of Indonesia and Thailand.

The Food and Agriculture Organization of the United Nations estimated 2002 cassava production in Nigeria to be approximately 34 million tonnes(FAO, 2004). The trend of cassava production reported by the Central Bank of Nigeria put the highest estimate of production at 37 million tonnes in 2000 (FMANR, 1997). The third series provided by (PCU, 2003) had the most conservative estimate of production at 28 million tonnes in 2002.

Nigeria’s production was targeted at 40 million tonnes by 2005 and 60 million tonnes by 2020 (IITA, 2002). Nigeria, being the world’s largest producer of cassava should be able to utilize its vast potential to provide enough of the tuber, not only for human consumption, but also for animal feed, industrial use and export. In animal feed, it can be used as flour after being peeled or chipped with the peels and ground before use. Studies have shown that levels as high as 20% could be used in diets for layers (Tewe and Egbunike 1992) and 40% in broilers (Eruvbetine and Afolami, 1992) and 10% in replacement pullets (Eruvbetine et al., 2002). Onyimonyi and Okeke (2005) reported that 20
percent of the maize content of the diets of grower pigs can be replaced by cassava peelmeal without any deleterious effect on the carcass, organ characteristics and no pathological effects was observed.

The greatest limitation to the use of cassava for livestock feeds is its content of cyanogenic glucosides, linamarin and lotaustralin. Toxicity of cassava is caused by hydrocyanic acid (HCN) which is liberated when the glucoside is hydrolysed by the action of linamarase enzyme. The degree of toxicity depends upon the variety, ecological conditions for growth of the plant., the form of the product being fed and its processing technology (Coursey, 1973). The normal range of HCN in fresh cassava root is 15-400ppm (Rogers, 1963).

It has long been established that the peel contains 5-10times the prussic acid content of the pulp (Oyenuga and Amazigo, 1957). Maner (1974) observed that pigs can tolerate 150-200ppm HCN on a fresh basis or 102 on a dry matter basis. Tewe and Iyayi (1989) reported that
hydrocyanic content of sundried pulp and oven-dried pulp was 17.3-26.7ppm and 23.7-31.3ppm respectively. Where the HCN is below 100ppm, as in cassava flour or chips, cassava can be safely incorporated into rations as is allowed in the EEC(Delange and Ahluwalia, 1983) The advent of enzymes as feed additive in livestock feed has shown a lot of prospects as a way of improving the utilization of fiber feedstuffs by monogastric animals.

The last 20 years have witnessed a substantial increase in use of supplementary enzymes to improve the nutritive value of hitherto neglected feedstuffs. A variety of enzymes, mostly of fungi or bacterial origin is now available to the livestock farmer. Exogenous enzymes supplementation on diets improves production efficiency, reduces nutrient loss through excreta, allowing the reduction of diets nutritional levels with likely economic advantages.

Enzymes are added to animal ration with the goal of increasing its digestibility, removing antinutritional factors, improving nutrient  availability, as well as for environmental issues. A large number of carbohydrases, proteases, phytases and lipases is used for this purpose (McCleary, 2001). According to Buchanan et al. (2007) exogenous enzymes hydrolyze nonstarch polysaccharides (NSPs) which might be potentially used by the animal, increasing the usage of feed energy. Moreover, the releasing of cell content occurs, becoming available to enzymatic digestion, therefore increasing the digestibility of all nutrients.

Another important consequence of this utilization is the reduction of such non-digestive residues negative impacts on digesta viscosity (Slominski et al., 2006). Vegetable ingredients used in poultry diets frequently have antinutritive factors, which reduce ingredient digestibility as well as nutrient availability of the entire diet. Among anti-nutritive factors, the most common are the non-starch polysaccharides (NSPs), which increase intestinal viscosity, impairing endogenous enzymes action and absorption and phytate, which turn minerals unavailable, mainly bivalent metals. In order to act on NSPs, there are several enzyme complexes with effects on arabinoxylans digestion, composed of pentosans and beta-glucans, others yet, have effects on galactosides and oligomannans.

Specific for phytates, the enzyme phytase has been very efficient on releasing P from the ring-shaped structure of phytate, as well as from such minerals as calcium, zinc, iron, manganese and others. According to Schang and Azcona (2003), the presence of pentosans in wheat, oligosaccharides in soybean and phytates in every vegetable ingredient limit energy, protein and phosphorus digestibility of diets. Using
specific enzymes allows the improvement of these compounds utilization and nutrient digestibility, by and large, which contributes to animal’s performance improvement (Dale, 2000; Vieira, 2003; Fernandes and Malaguido, 2004). In general, enzymes are used in animal feeding aiming at two welldefined purposes: to complement the enzymes insufficiently produced by the animal (amylases and proteases) and to provide animal those enzymes not synthesized by them (cellulases) (Fischer et al., 2002). Besides, researches performed by Choct (2004) and Ferket (2004) have demonstrated beneficial changes on microbial intestinal population by supplementing exogenous
enzymes in the diets.

Such benefits occur due to a higher starch, protein and fat digestion rate in the small intestine, therefore limiting substrate for pathogenic flora that eventually exists. Commercial preparations involving enzymes as amylase, xylanase, protease, galactosidase, pectinase, cellulase
and lipase have been used successfully on poultry performance improvement (Garcia et al., 2000). Soluble glucans and pentosans (xylose+ arabinose) are observed in several cereals and are capable of forming gels, when in touch with water, creating viscous solutions that delay nutrient absorption.

It is postulated that pentosans form complexes bonds with the albumen fraction of proteins. Pentosans, yet, raise the diet volume by water retention in the gastrointestinal tract, causing a decrease in feed intake. There are some mixed enzymes such as Natugrain, Nutra xyla, Roxazyme G, Biozyme, Mixagrain in the market. The present study was undertaken to determine the effect of Nutrase xyla and Roxazyme G in peeled cassava root meal based diets for broilers.




1.1 Study Objectives

The objectives of the study are as follows:
i. To evaluate the performance of broilers fed different enzyme substrates in peeled cassava root meal based diets.
ii. To investigate the carcass quality of broilers fed different enzyme substrates in peeled cassava root meal based diets
iii. To investigate the nutrient retention of broilers fed different enzyme substrates in peeled cassava root meal based diets.

1.2 Justification of the study

All the existing knowledge with respect to exogenous enzymes usage in poultry feeds, have been extracted from experiments carried out with rations which contain high amount of barley, wheat, rye and sunflower (which are mostly found in the temperate regions) with high cellulose.
There seems to be little or no information available on similar works with tropical feedstuffs. Hence, it became necessary to carry out this study to see how it will work with tropical feedstuffs (Peeled cassava root meal) compared with temperate feedstuffs.



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