THE EFFECT OF DIFFERENT ENZYME SUBSTRATES ON THE PERFORMANCE OF BROILERS FED PEELED CASSAVA ROOT MEAL (PCRM) BASED DIET

ABSTRACT

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 randomised 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.

CHAPTER ONE

INTRODUCTION

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   anti- nutritive  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  well- defined 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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