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.
TABLE OF CONTENTS
CONTENTS PAGES
Title page — — — — — — — — — i
Certification — — — — — — — — — ii
Dedication — — — — — — — — — iii
Acknowledgement — — — — — — — — iv
Abstract — — — — — — — — — v
Table of Contents — — — — — — — — vi
List of Tables– — — — — — — — — viii
CHAPTER ONE:INTRODUCTION
1.1 Study objectives — — — — — — — 5
1.2 Justification of the study — — — — — — 5
CHAPTER TWO: LITERATURE REVIEW — — — — 6
2.1 Utilization of cassava in Poultry feeding — — — 6
2.1.1 Nutritive status of Peeled Cassava Root Meal — — 9
2.1.2 Limitations to the use of cassava in poultry feeds — — 10
2.1.3 Overcoming the Limitations — — — — — 12
2.1.4 Peeled cassava root meal in broiler nutrition — — 15
2.2 Commercial enzymes supplementation in Broiler Nutrition 17
2.2.1 Economic impacts of commercial enzymes — — — 19
2.2.2 Flexibility of low cost diets formulation — — — 19
2.2.3 Higher nutrient digestibility and better poultry performance
of commercial enzymes — — — — — 21
2.2.4 Improvement on litter quality — — — — — 22
2.2.5 Commercial enzymes’ improvement on birds’ health — 23
2.2.6 Environmental impacts of exogenous enzymes utilization on
poultry feeding — — — — — — — 23
CHAPTER THREE:MATERIALS AND METHODS
3.1 Location — — — — — — — — 27
3.2 Materials — — — — — — — — 27
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3.3 Experimental Birds and Management — — — — 27
3.4 Data collection — — — — — — — 29
3.5 Parameter determined — — — — — — 29
3.6 Statistical Analysis — — — — — — 32
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Average daily feed intake (ADFI) of broilers fed different levels of
PCRM diets with different enzyme substrates — — — 33
4.2 Average daily weight gain (ADWG) of broilers fed different
levels of PCRM diets with different enzyme substrates — 36
4.3 Feed conversion ratio (FCR) of broilers fed different levels of
PCRM diets with different enzyme substrates — — — 39
4.4 Feed cost per kg weight gain (FC/kgWG) of broilers fed different
levels of PCRM diets with different enzyme substrates — 42
4.5 Carcass quality of broilers fed different levels of PCRM
diets with different enzyme substrates — — — — 45
4.6 Nutrient retention of broilers fed different levels of PCRM diets with
Different enzyme substrates — — — — — 48
4.7 Discussion — — — — — — — — 51
4.7.1 Average daily feed intake — — — — — — 51
4.7.2 Average daily weight gain– — — — — — 52
4.7.3 Feed conversion ratio — — — — — — 53
4.7.4 Feed cost per kg weight gain — — — — — 53
4.7.5 Carcass quality — — — — — — — 54
4.7.6 Nutrient retention — — — — — — — 54
CHAPTER FIVE: SUMMARY AND CONCLUSION
5.1 Summary — — — — — — — — 56
5.2 Conclusion — — — — — — — — 57
5.3 Recommendation — — — — — — — 57
References — — — — — — — — 58
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
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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)
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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,
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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
5
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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