1. INTRODUCTION
The livestock population in Ethiopia is
considered to be the largest in Africa. It was reported that the country owns about 60 million cattle,
33.5 million sheep, 32.06 million goats, 1.91 million horses, 6.75 million
donkeys, 0.35 million mules, 1 million camels and 60.38 millions of poultry (1). This livestock sector has been contributing considerable portion to
the economy of the country both at the household and national levels and have
in the past provided significant export earnings. But not to the extent it has
to contribute to the development of the economy of the country. This is due to
different constraints from which feed inadequacies (huge gap between demand and
supply of nutrients) are reported to be all-encompassing and persistent
constraints affecting the production and reproductive performance of different
classes of livestock (2), (3), (4).The focus of feed resources and their utilization represents possibly
the most exciting task facing planners and animal scientists in developing
countries (5) which is the same catastrophe in Ethiopia. The most devastating
factor diminishing of feed for animals
is due to rapid increment in the expansion of arable land that reduce the
grazing land which is the major source of conventional animal feeds. Due to the
shortage of traditional feeds, non-conventional feeds may be the other
alternative feeds.
Limited feed
supply and poor quality of the available feeds are the major constraints for
optimal livestock productivity in tropical and sub-tropical countries (6). These regions are characterized by irregular rainfall and thus
livestock have to survive on persistent shortage of feed resources of low
nutritional value for most part of the year (7). Non-conventional feed resources (NCFR) generally refer to all those
feeds that have not been traditionally used for feeding livestock and are not
commercially used in the production of livestock feeds(8). Several known examples include palm leaf meals, palm press fiber,
cassava foliage, spent brewers grains, sugar cane bagasse, rubber seed meal
and some aquatic plants.
Defined in this manner non-conventional feed
resources can be looked at as covering a wide diversity of feeds and their
nutrient contents. A common feature about feeds is that the traditional feeds
of tropical origin tend to be mainly from annual crops and feeds of animal and
industrial origin. In this sense, the term NCFR could really be more
appropriately referred to as new feeds, and this term is increasingly being
used. Thus the term NCFR has been frequently used to describe sources such as
oil palm by-products, single-cell proteins and feed materials derived from
agro-industrial by-products of plant and animal origin, poor-quality cellulosic
roughages from farm residues and other agro-industrial by-products such as
slaughter-house byproducts and those from the processing of sugar, cereal
grains, citrus fruits and vegetables from the processing of food for human
consumption.
This list can
be extended to include derivatives from chemical or microbial processes as in
the production of single cell proteins. However it is sometimes difficult to
draw a distinct line between traditional feeds and NCFR. In some countries such
as India and Pakistan, what may now be classified as NCFR may in fact be
conventional/traditional owing to the fact that it may have been in use as
livestock feed over a long time, an example is wheat straw which is very widely
used in these two countries, in addition, the availability of NCFR, especially
of plant origin, is dependent to a large extent on the type of crops being
cultivated and the prevailing degree of application of the crop technology (9). Therefore, this paper aims to review the major non-conventional feed
resources with the overall objectives listed
below,
1. To highlight information on the
nutritional value of various nonconventional feedstuffs on livestock
2. To review the best options of
using non-conventional feeds as alternative sources of feed
3. To review the effects of ammoniation (feed processing methods) on the nutritional
value of high fiber containing feed stuffs on the performance of livestock
2. LITERATURE REVIEW
2.1. Non-Conventional Feeds
A major gap exists between the demand and
supply of concentrates and green and dry fodders for feeding livestock in the
world. To overcome this shortage, it is essential to increase the availability
of feed and fodder for the different productions and functions of the animals.
One of the solutions is also to exploit the use of NCFR in the animal feeding
system. Some of the potentially available NCFR are rubber seed cake, Sal seed
meal, tapioca waste, tea waste, babul seeds, slaughter house byproducts, mango
seed kernels, nizger seed cake, karanj
cake, guar meal, Prosopis juliflora
pods and cassava leaf meal, Sea buckthorn leaves, cake and pomace, and animal
organic wastes (bovine and poultry excreta) etc. Many of these feed materials
are low in energy, protein, minerals and contain high amounts of lignin, silica
and other nutritionally incriminating substances.
The main
constraints to the use of non-conventional feed resources are collection,
dehydration for high moisture content and detoxification processes. Processing
technologies that are economic and practical are urgently required. Some of the
materials like Sal seed meal; neem seed cake, mahua seed cake, and galas seed cake are available in large
quantities but due to the presence of potent toxic substances, have limited
value as animal feeds. Many of the forest tree seeds contain 15-35% oil and are
used for the extraction of oil, after which the cake is valuable as animal
feeds. Animal organic wastes such as dung and poultry excreta are also
potentially available as a part of animal feeds. During the dry periods, poor
quality feeds and inadequate nutrition has been reported to be one of the most
important constraints for livestock production in Ethiopia across all
ecological zones. In addition, degradation of lands due to uncontrolled and
excessive use of communal grazing lands of undulated topography in the
highlands and erratic rainfall in semi-arid areas has further reduced the
availability of feed resources (7).
Essential or
indispensable amino acids (EAAs) cannot be synthesized by fish and often remain
inadequate but are needed for growth and tissue development (10). Fishmeal is known to contain complete EAA profile that is needed to
meet the protein requirement of most fish species. Since fishmeal is expensive
as a feed ingredient, the use of non-conventional feedstuffs has been reported
with good growth and better cost benefit values. The utilization of
non-conventional feedstuffs of plant origin had been limited as a result of the
presence of alkaloids, glycosides, oxalic acids, phytates,
protease inhibitors, haematoglutinin, saponegin, momosine, cyanoglycosides, linamarin to
mention a few despite their nutrient values and low cost implications (11) (12).
These
anti-nutritional factors negate growth and other physiological activities at
higher inclusion levels (13). NCFRs are credited for being noncompetitive in terms of human
consumption, very cheap to purchase, by-products or waste products from
agriculture, farm made feeds and processing industries and are able to serve as
a form of waste management in enhancing good sanitation. These include all
types of feedstuffs from animal (silkworm, maggot, termite, grub, earthworm, snail,
tadpoles etc.), plant wastes (jack bean, cottonseed meal, soybean meal, cajanus, chaya, duckweed, maize
bran, rice bran, palm kernel cake, groundnut cake, brewers waste etc.) and
wastes from animal sources and processing of food for human consumption such as
animal dung, offal, visceral, feathers, fish silage, bone, blood) (14) (15) (16)(17). All these can be recycled to improve their value if there are
economically justifiable and technological means for converting them into
useable products.
2.2 Need of Non-conventional feed resources:
There are serious
shortages in animal feeds of the conventional type. The grains are required almost exclusively for human consumption. With increasing demand for livestock products as a result of rapid growth in the world economies and shrinking land area, future hopes of feeding the animals and safeguarding their food security will depend on the better utilization of unconventional feed resources which do not compete with human food. The availability of feed resources and their rational utilization for livestock represents possibly the most compelling task facing planners and animal scientists in the world. The situation is acute in numerous developing countries where chronic annual feed deficits and increasing animal populations are common, thus making the problem a continuing saga.
Thus non-conventional
feeds could partly fill the gap in the feed supply, decrease competition for food between humans and animals, reduce feed cost, and contribute to self-sufficiency in nutrients from locally available feed sources. It is therefore imperative to examine for cheaper non-conventional feed resources that can improve intake and digestibility of low quality forages. Feedstuffs such as fish offal, duckweed and kitchen leftovers (i.e., potato peel, carrot peel, onion peel, and cabbage leftover), poultry litter, algae/Spirulina, Leucaena leaf, local brewery
and distillery by-products, sisal waste, cactus,
coffee parchment and coffee pulp are commonly
used in India, and could be invaluable feed
resources for small and medium size holders of
livestock.
2.3 Advantages of Non-conventional feed resources
a) These are end
products of production and consumption that have not been used. b) They are mainly organic and can be in a solid, slurry or liquid form. Their economic value is often very less. c)
Fruit wastes such as banana rejects and pineapple
pulp by comparison have sugars which are
energetically very beneficial. d) The feed
crops which generate valuable NCFR are
excellent sources of fermentable carbohydrates
eg. Cassava and sweet potato and this are an advantage to ruminants because of their ability to utilize inorganic nitrogen. e) Concerning the feeds of crop origin, the majority are bulky poor-quality cellulosic roughages with a high crude fibre
and low nitrogen contents, suitable for
feeding to ruminants. f) They have considerable potential as feed materials and their value can be increased if they are converted into some usable products.
2.4. Sources of non-conventional feeds
The generation of non-conventional feed
resources is essentially from agriculture and various agro based industries and
is a function of many factors. Such factors include the quantity and quality of
the materials produced which is dependent on the prevailing agro-climatic
conditions and cropping patterns, the type of raw materials, the production
process, the production rate, the type of inputs used, the regulations
affecting product quality use and the constraints imposed upon effluent
discharge (18). Most non-conventional resources are usually regarded as waste which
is an inaccurate description of this group of materials. They can be regarded
as waste when they have not been shown to have economic value. When such waste
can be utilized and can be converted by livestock to valuable products which
are beneficial to man, they become new feed materials of importance. In
addition, they can be used to supplement the existing limited feed resources.
Recycling, reprocessing and utilization of all or a portion of the wastes,
offers the possibility of returning these materials to beneficial use as
opposed to the traditional methods of disposal and relocation of the same
residues. Defined in this manner the NCFR embrace a wide diversity of feeds and
its nutrients contents.
A feature
about feeds is that the traditional feeds of tropical origin tend to be mainly
from annual crops whereas, the NCFR include commonly, a variety of feeds from
perennial crops and feeds of animal and industrial origin. In this sense, the
NCFR could really be more appropriately termed "new feeds", and this
term is being increasingly used. Thus, the term NCFR has been frequently used
to describe such new sources of feedstuffs as palm oil mill effluent and palm
press fiber (oil palm by-products), single cell proteins, and feed material
derived from agro-industrial by-products of plant and animal origin,
poor-quality cellulosic roughages from farm residues such as stubbles, haulms,
vines and from other agro-industrial by-products such as slaughterhouse
by-products and those from the processing of sugar, cereal grains, citrus
fruits and vegetables from the processing of food for human consumption.
2.5 By-products as feedstuffs and nutritional
quality
Appropriate use of
relatively inexpensive agricultural
and industrial by-products is of paramount
importance for profitable livestock production.
However, high cost and low availability of
conventional livestock feedstuffs frequently
demand consideration of by-products even if
efficiency of utilization is low. Efficient use
of by-products relies on their chemical and physical
properties, which influence production system
outputs. In developing countries, grain, which
forms the bulk of concentrate feeds for livestock,
is both in short supply and expensive due to
direct competition with human food uses.
The agro-industrial by-products like
brewery waste, cashew apple waste, cashew nut shell, rice kani
(broken rice), alternative cereals like ragi, bajra and green fodder like cowpea leaves, are available in
plenty locally. Presently these by-products are not exploited to full extent
for inclusion in the poultry feed. These by-products and fodder leaves have
good nutrient composition and reported to contribute to the productive value
for egg and meat with reduction in cost of production. Hence, based on chemical
compositions and potential feeding value, these by-products can be incorporated
in the poultry feed formulations to economize the feed cost and to increase the
profit margin for the poultry farmers.
Natural pasture that is
estimated to contribute to 8090%
of livestock feeds and whose quality is
seasonally variable is the main source of feed in
arid and semi-arid pastoral areas, while crop residues
contribute up to 50% of the feed supply in
mixed-farming system. Grazing lands are steadily
shrinking by conversion to arable lands, and
natural pastures are also restricted to areas that
are marginal and have little farming potential.
The reduction in natural pasture has led to
overutilization and domination by undesirable
forage species resulting in partial dependence
on crop residues by most ruminants, which has
reduced livestock productivity.
The increasing human demands for several foods (i.e. olive oil,
vegetables, wine, fruit juices, etc.) led to a
considerable increase of lands occupied by
crops producing these feeds. Consequently,
huge amounts of agro- industrial by-products
are available in numerous developing countries
(e.g. molasses, olive cake, winery marc,
etc.), which are still not fully utilized in
livestock feeding.
2.6 Agro-industrial by-products and utilization
2.6.1 Cottonseed Meal
The first record of crushing
cotton seed for oil or cake (meal) is associated with the Hindus, where it is
believed, the oil was used as a medication for external application. The use of
cottonseed oil had earlier been documented in other parts of the world, but it
was not until 1768 that extraction of oil was reported in the US. However it
was not until fifteen years after the report that a greater interest was
developed in this area for oil extraction and (cake) meal production for animal
feed (19). Since then, improvements have been made on method of
processing for oil and the meal. Presently, commercial processing of cotton is
carried out by any one of the four methods; (1) hydraulic pressing; (2) screw
pressing; (3) prepress solvent extraction; (4) direct solvent extract (20). The primary objective of any of these methods is to
extract oil and to bind the free gossypol pigment in the meal thereby
preventing the pigment (unbound gossypol) from being extracted into the oil.
Cottonseed meal contains high levels of crude protein (about 40-45%). Its use
in animals diets is limited due to the presence of gossypol.
Gossypol
is a yellow phenolic compound containing aromatic (benzene) rings with hydroxyl
(OH) groups attached. The pigment is found primarily in cotton seeds, but has
also been isolated in other parts of the plant, (roots, bark, stem, leaves and
taproots) of Gossypium species. Gossypol constitutes
about 0.4-1.7% of a cottonseed and is structurally shown to be
(2,2'-binaphthalene)-8,8' dicarboxaldehyde - 1,1,
'6,6, '7,7'-hexahydroxy 5, 5' diisopropyl 3, 3'
dimethyl with a molecular weight of 518.54 and molecular formula or C30H3008 .
Among all the constituents of cottonseed, the pigments have been the subject of
numerous studies because of the impact it has had on the oil and the meal
relative to its biochemical, physiological and economic influence on livestock
feeding and nutrition. (20), indicated that the yellow
gossypol derivative (C30H3008) is the major naturally occurring pigment. The
gossypol pigment was first isolated by an English chemist Longmore, in 1866;
and a Polish chemist (Marchlewski), crystallized the
acetic acid derivative and named it gossypol, designating its genus, (Gossypium), and chemical nature, (phenol). In 1915, Withers
and Carruth established that gossypol was the toxic
factor in cottonseed meal ((21), (22)).
2.6.1.1
Cottonseed meal and gossypol effect on livestock.
Gossypol causes three main
problems in the livestock industry: (1) tissue pathology and physiological
effects. (2) binding of the epsilon amino group of
lysine, resulting in a reduction in lysine availability. (3) discoloration
of the egg yolk after storage of eggs from layers fed cottonseed meal. There
are marked species differences in terms of response to the toxic effect of
gossypol in cottonseed meal (20).
Ruminants
Ruminants are less susceptible
than non-ruminants to gossypol toxicity. The mechanism is thought to involve
the toxic free gossypol becoming bound to soluble proteins in the rumen and to
the epsilon amino group of lysine forming a permanent bond, thereby preventing
gossypol absorption. The bond is not easily broken by proteolytic enzymes
secreted in the lower gut. The rumen microbes may have a role in this process (23). If the rumen detoxification process is by passed for
some reason, toxicity can occur with varying toxicity signs and symptoms. Young
calves with functionally undeveloped rumens are more susceptible to gossypol
toxicity than adult bovines ((24),(25)).
Gossypol
toxicosis in sheep can be caused by ingestion of
large amounts of gossypol-containing diets or injection of gossypol acetic acid
(GAA) (26). The situation in sheep production is the need for
earlier weaned lambs (6-8 weeks of age) during which its rumen has three stages
of development: (1) nonruminant phase, from birth to
three weeks old; (2) transitional phase from three weeks to eight, and (3) a
functioning ruminant phase, from eight weeks onward. In young lambs, an intake
of gossypol-containing diet may result in similar toxicity symptoms, hence
young sheep (lamb) of less than eight weeks can be treated as nonruminants ( (24), (27), and (28) ).
Poultry
Utilization of cottonseed meal in
poultry diets is limited by the constituents of the meal that affect or limit
its efficient utilization. These include oil, gossypol, fiber, lack of
available amino acids (lysine) and total protein. Detrimental effects in
poultry include reduced feed intake, efficiency of feed utilization, growth
rates, fertility and or hatchability, egg production, physiological and
biochemical findings as well as increased mortality rates, especially if the
dietary levels of free gossypol exceed 0.04% ( (29), (30), (31), (32)). Although gossypol causes discoloration of egg yolks and
whites, iron salts such as ferrous sulfate (FeSO4 .7H20) inactivate gossypol,
hence reducing effects on egg yolk and white yolk ( (33) (34)).
Swine
Deleterious effects of gossypol
have limited the efficient use of cottonseed meal in the diets of swine. Signs
of gossypol toxicity in swine include labored breathing, (dyspnea), decreased
growth rate and anorexia. Postmortem findings can include fluid accumulation in
the peritoneal cavities, edema, and congestion in the liver and lungs (35).
2.6.1.2
Antifertility effects of cottonseed meal or gossypol
Cottonseed meal and other
cottonseed products have long been used to supplement other protein sources or
protein deficient diets for both human and animals. Antifertility effects were
identified during the 1950s due to lack of child birth for a period of over ten
years in the Habethi province of China, where
cottonseed oil had been used in the people's diet. Several investigations were
initiated in the 1960's on both animals and a human, leading to the discovery
that gossypol is capable of inhibiting male fertility(36). About 4,000 men placed on a 20 mg gossypol pill per day
for more than six months became infertile with an antifertility efficacy of
99.9%. This was evaluated by sperm examination which showed decreased motility
and malformed spermatozoa, followed by gradual drop in sperm count until
azoospermia was achieved. The process by which gossypol exerts its effect on
spermatozoa is that the gossypol first damages the spermatids, and then with
increase in dosage, spermatocytes are damaged, subsequently, the spermatids and
spermatocytes are exfoliated with numerous dead spermatozoa, with dead heads
and separated tails causing a decreased count in sperm and azoospermia (37). (38) Has reviewed literature on the effects on gossypol and
cottonseed products on the fertility of various species of animals.
2.6.2 Sunflower oilcake
It is the residual cake remains
after the expression of oil from sunflower seed and used chiefly as a livestock
feed. It is a concentrated feed rich in
protein and fats. In amino acid content and biochemical value oil cake proteins
are superior to those of cereals; they contain more lysine, methionine, cystine, and tryptophan. Soybean oil cake is rich in amino
acid lysine. The calcium and phosphorus contents are also higher. Like cereal
feeds, oil cakes are poor in carotene but rich in vitamins of the B complex.
Sunflower oil cake (SOC) is deficient in amino acid lysine but rich in sulphur containing amino acid methionine.
3. CHARACTERISTICS OF NON-CONVENTIONAL FEEDS
According to reports (67), non-conventional feed resources like conventional feed resources
have several characteristics worthy of note. ‒ They
are the end products of production processes and consumption that have not been
used, recycled or salvaged. ‒ They are mostly of
organic origin and can be obtained either in a solid, slurry or liquid form.
‒ The economic value of these non-conventional
feed resources is usually less than the cost of their collection and
transformation for use and consequently, they are discharged as wastes. ‒
Feed crops which generate valuable NCFR are usually excellent sources of
fermentable nutrient molecules such as cassava and sweet potato and this is an
advantage to livestock especially ruminants due to their ability to utilize
inorganic nitrogen and non-protein nitrogenous sources. ‒ Fruit wastes
such as banana rejects and pineapple pulp by comparison have sugars which are
energetically beneficial. ‒ The majority of
feeds of crop origin are bulky poor-quality cellulosic roughages with high
crude fiber and low nitrogenous content which are suitable for feeding mostly
ruminants. ‒ Some of these feeds contain
anti-nutritional components which have deleterious effects on the animals and
not enough is known about the nature of the activity of these components and
ways of alleviating their effects. ‒ Non-conventional feed resources have
considerable potential as feed materials and for some; their value can be
increased if there were economically viable technological means for converting
them into some useable products.‒ Substantial information is required on
chemical composition, nutritive value, the presence of anti-nutritional
components and value in feeding systems.
3.1. Anti- nutritional factors
One major constraint in the use of
non-conventional feedstuffs is the anti-nutritional factors contained in them.
Anti-nutritional factors may be defined as the chemical constituent of a
feedstuff, which interferes in the normal digestion, absorption and metabolism
of feeds, some of which may have deleterious effects on the animals digestive
system. Some inherent chemical constituents present in different kinds of
feedstuffs interfere in the optimum utilization of nutrients and some are also toxic
in high concentrations. Although anti-nutritional factors are present in many
conventional feeds, these are more common in most of the non-conventional feeds
(68).
These
anti-nutritional factors need to be removed or inactivated by various
procedures before the use of the ingredients in the diet. Many seeds, which
were once used in traditional human and animal diets, have now fallen into
disuse as agricultural and nutritional needs are re-assessed (69). Seeds often contain factors such as lectins, which are deleterious
or toxic to animal or man (8). Seed lectins present major problems as they are resistant to heat
treatment and some seeds such as kidney bean, have to be heated for several
hours at temperatures above 80ΊC or boiled for 10-20 minutes to ensure the
elimination of their lectin activity. Great caution should therefore be taken
in the use of these seeds as dietary materials. This is particularly important
since recent studies suggest that long-term exposure to relatively low levels
of some anti-nutritional or toxic factors may have deleterious effects on body
metabolism (70).
4. FEED PROCESSING METHODS
There is an abundance of
by-products and other non-conventional feedstuffs in the world that can be used
as alternative sources of energy and protein feedstuff for livestock
production, but often the techniques for making them more profitable for animal
feeding systems are unknown or too difficult to implement for efficient
livestock production. As a result, millions of tons of potentially valuable
feed are either discarded or underutilized on annual basis, and in many
instances, they have become environmental or pollution problems (55). As a result of economic and ecological pressures on the
environment, the need for efficient disposal of such products has become of
paramount importance. A possible effective disposal method is by way of
converting these products of various sources (agricultural by products,
forestry products, animal wastes, municipal refuse and crop residues) into
energy sources for livestock feeds (56). Such sources can be effectively converted into livestock
feeds through different feed processing methods. One such method is ammoniation; others may include hydrolysis, composting,
dehydration, cooking, grinding and extrusion.
4.1 Ammoniation
Ammoniation is one of the feed processing methods that can be
employed in treatment of fibrous feedstuff, crop residues, and other types of
by-products to improve their utilization in livestock feeding. It was first
studied in Germany many years ago after a marked improvement was achieved by
treatment of straw with caustic soda (NaOH) (57). Ammoniation can be
accomplished by either the use of ammonia hydroxide (NH3OH) or gaseous ammonia,
both of which are effective in dissolving lignin, solubilizing hemicellulose,
causing swelling of cellulose and providing supplemental nitrogen that can
utilized by microbes for protein synthesis (57).
Ammonia
(NH3) is a colorless gas with penetrating odor under standard conditions, and
has a molecular weight of 17.03. Under laboratory conditions ammonia may be
formed as the product of a number of chemical reactions which may include the
following:
1. Ammonia salts with a strong
base
2. Hydrolysis of urea
3. Nitrogen with hydrogen in the
presence of a catalyst(58).
Although urea can be used as a
source of ammonia for treatment of straw, it may be less effective than
anhydrous ammonia because of the formation of a carbonate which decreases the Ph of the straw, hence reducing the alkalinity effect of
the conformational changes in fiber. Ammonia can also be generated from other
nitrogenous materials such as poultry manure, and human and animal urine. The
use of the latter has been researched in Bangladesh; however, they are
relatively new techniques currently being developed (59).
The
beneficial effects of treating straw with ammonia under different conditions
have been reviewed (57). It was also reported that ammoniation
of straw increased crude protein, cell wall constituents, rumen ammonia and dry
matter. They also indicated that ammoniation improved
feed intake and dry matter digestibility. Dry matter intake, daily gain, and
feed to gain ratio were improved as a result of treating low quality forage (limpograss and straw) with ammonia(60).
They
also indicated that the apparent digestion coefficients of organic matter,
neutral detergent fiber, acid detergent fiber and hemicellulose were improved,
and concluded that ammoniation could provide an
opportunity for improving the feeding value of low quality forages by providing
an option to the traditional winter feeding programs. Other beneficial effects
of ammoniating low quality forages and by-products on beef cattle and buffalo
calves have been reported (61). However, although the digestibility of organic matter,
crude protein and feed intake were improved as a result of treating corn straw
with urea, weight gain was not influenced.
Treating
wheat straw with anhydrous ammonia and ammonium hydroxide (NH4OH) improved
utilization of nutrients such as dry matter, organic matter, and acid detergent
fiber in sheep(62). Lambs fed
ammoniated wheat straw consumed 34% more, and the nutrient digestibility, ruminal Ph and plasma urea
concentration were higher when compared to those fed untreated wheat straw(63).
Ammoniation of sweet
clover hay increased the nitrogen content and reduced dicourmarol
levels and prevented the bleeding disease associated with sweet clover hay when
fed to livestock ammoniation of endophyte-infected
tall fescue hay reduced its toxicity to steers. They concluded that ammoniation may be a practical solution to some of the
fescue related economic problems in cattle(64).
The
toxic constituents of plants have different types of biological impact on
different species of livestock. Pyrrolizidine alkaloids (PA's), found in plants
like tansy ragwort, (Senecio jacobaea), Crotalaria (Crotalaria spectabilis),
tall fescue (Festuca arundinacea)
and various other species (Heliotropium, Echium and Amsinckia) are usually
bitter in taste and function primarily as the chemical defense mechanism of
plants. The PA's are not poisonous until metabolized by liver tissue to hepatoxic metabolites (pyrroles)
causing irreversible liver damage. The PA's are hepatoxic
to many animals and are responsible for losses of large numbers of livestock
throughout the world (43).
Feeding
chicks and pigs varying levels of crotalaria seeds caused decreased weight gain
and high rate of mortality(65). Crotalaria is not only hepatoxic, it can also
damage pulmonary, renal organs and cause fetal death and malformations in
animals. Feeding tansy ragwort to lactating and kid goats resulted in mortality
with obvious signs of alkaloid toxicosis. indicated that cattle and horses are more
susceptible than goats, sheep and other non-ruminant herbivores (rabbits,
gerbils, guinea pigs,and hamsters) to alkaloid toxicosis(43).
The toxicity of tall fescue is due to the
infection of the plant by the endophytic fungus (Epichlore typhia) which upon
parental administration or ingestion can result in symptoms of convulsion,
muscular incoordination, increased pulse and respiration rates, mild
photosensitization and coma.
The
ergot peptide alkaloids (ergovaline) produced by the
endophyte in tall fescue also causes fescue toxicosis,
causing decreased prolactin, increased body temperature, and powerful
vasoconstrictive effects. The tall fescue alkaloids can also cause prolonged
gestation, thickened placentas, large weak foals, dystocia, agalactia
in pregnant mares, neurohormonal imbalances of
prolactin and melatonin, restricted blood flow to internal organs, aberrant
reproduction, decreased growth, slow maturation and a general decrease in
livestock performance particularly cattle and sheep (43).
Apart
from the major oil seeds like soybean and cottonseed meals which are
traditionally used as protein sources in animal feeds, there are also many
others that could as well be utilized for the same purpose. Some of these are
in the brassica families which include cabbage, brussels sprouts, kohlrabi, kale, meadow foam,
rapeseed, broccoli, radish, mustard and turnips. The brassica family plants are
known to contain glucosinolates (glycosides of B-D- thioglucose) that yield isothiocyanates,
nitrile, and thiocyanates on hydrolysis by an enzyme system producing varying
adverse effects on livestock consuming them. The major effects of glucosinolates products in animal production include goiter
(enlarged thyroid gland), decreased feed intake, liver and kidney lesions, and
poor performance in animals consuming them (43).
However,
it has been reported that the deleterious effects of glucosinolate
can be lowered by ammoniation. Canola seeds
containing high levels of glucosinolates, treated with
lime or ammonia, resulted in a lowered tainting potential by reducing the progoitrin, soluble tannin, sinapine
contents and improved feed intake in pigs, but the treatment effects were not
sufficient to prevent the trimethylamine effects on eggs(66). Another glucosinolate
containing seed, meadowfoam has been evaluated as a
feed for nonruminants, rabbits and chickens, and a
satisfactory performance observed in lambs that were fed raw meadowfoam. (43) Indicated that up to 25% of meadowfoam
could be fed to beef cattle without adverse effects on performance. The effects
of other classes of toxicant containing seeds and forages like kohlrabi, whole
cottonseed, vetch seeds, leucaena leaves, pinto and
kidney beans, bracken fern and raw soybean on the performance of livestock have
been documented ((43); (66)). It is clear that some of these toxic containing forages
and seeds cannot be effectively utilized for livestock production without
processing to achieve good performance.
The
purposes of processing any feedstuff and by-product for animal feeding are
mainly to eliminate their negative effects, hence bringing about improvement in
digestibility, palatability, acceptability as well as alteration of particle
size, extension of shelf life, increase in nutrient make up, and detoxification
of toxic constituents.
4.2 Feed additives
Feed additives are defined as
non-nutritive substances that can be added to feeds to improve the efficiency
of feed utilization, feed acceptance, health and metabolism of the animal in
one way or the other. There are many different types feed additives, however (43) classified feed additives into four broad classes based
on either their principal biological or economic effects:
I. Additives that influence feed
stability of feed manufacturing and feed properties.
II. Additives that modify growth,
feed efficiency, metabolism and Performance
III Additives that modify animal
health.
IV. Additives that modify consumer
acceptance.
It was stated that another class
of additive is that which is used to potentiate the disease-curing effects of
antibiotics(44). Certain naturally occurring substances of plant origin
like pectins, tannins, polysaccharides, cellulose,
and beta-glucans are sometimes found in feedstuffs that nonruminant
animals cannot digest, because they do not synthesize the required enzymes.
However, commercially produced enzymes such as cellulases
and beta-glucanase are used to aid digestion in nonruminants fed feedstuffs containing such substances as
barley, triticale and rye.
Barley
Barley (Hordeum
vulgare) is widely grown in the northern areas of
North America (US and Canada), Europe, China, and the Soviet Union. It ranks
fourth among the grains of the world after corn, wheat and rice, and it is also
a source of energy used as a livestock as a feedstuff. Although barley is lower
in digestible energy than corn and sorghum, it is higher in protein content and
quality than corn. Its lower energy value is associated with its high fiber,
lower starch and the high contents of poorly digested water-soluble
carbohydrates called B-glucans ((45), (46)).
Beta-glucans
are a part of the hemicellulose component of the plant cell structure that
contain a polymerized B-glucose linked together by a chemical bond known as
(1-->3)(1-->4) B-D-glucan. They are viscous, hygroscopic, gummy and are
different from those found in starch (a-->1-->4 and a-1>6). The
hygroscopic and gummy material causes wet and sticky feces and is responsible
for wet litter problems in poultry. Glucans can also impede nutrient absorption
resulting in plugging of the vent, particularly in chicks (pasty vents). The
viscous content is responsible for preventing the formation of micelles, thus
inhibiting the absorption of fat and other nutrients. On the average, some
varieties of barley, particularly those grown in the Pacific Northwest, are
known to contain up to 1.5 8% B-D glucan ((47), (48)).
The
deleterious effects of the B-glucan content of barley can be overcome either by
soaking or steeping in water, and by additions of commercially prepared enzymes
(B-glucanase) to diets containing the grains. Soaking
or steeping is believed to activate the B-glucanase
enzyme already present in barley seeds, hence reducing the glucan effects. The
commercially prepared enzyme (B-glucanase) and other
complex carbohydrate digesting enzymes aid nonruminant
animals in digestion of the grains and improve the utilization of Beta glucan
containing diets ((46);(43);(48)).
4.3 Utilization of barley in poultry and turkeys
It was indicated that when B- glucanase was added to barley, it resulted in the cleavage
of the B-glucan chain and reduction of the viscosity effect, thereby
eliminating the encapsulating effect of the B-glucan and exposing the
intracellular starch and protein to the endogenous enzymes for proper digestion
(48). Inclusion of enzyme preparation (B glucanase)
in the diets of chickens containing barley and rye resulted in improved body
weight gain, feed intake, feed efficiency and energy digestibility (46). Enzyme supplementation can also reduce the incidence of
pasted vent (49) indicated that apart from improvement in general
performance and reduction in fecal moisture, enzyme supplementation also
resulted in improved cage cleanliness. (50) Indicated that addition of enzyme increased fat and
starch absorption in chicks fed diets containing hull-less barley.
Layers
have a lower energy requirement than broilers, so a lower energy feedstuff like
barley seems to be a more suitable ingredient for layers than for broilers.
However, it has been suggested that one of the periods of concern in feeding
barley to layers is between the ages of 20-40 weeks. During this time the
layers have higher energy needs and begin to increase their feed consumption to
meet both egg production and body tissues demands, but cannot adequately
increase the consumption of low energy density feedstuffs. Another problem of
feeding barley containing diets to layers during this time is that it can increase
the high moisture content of the excreta resulting in dirty eggs(48).
However,
(51) reported that feeding layers of 20-36 weeks of age on
varying levels of barley, (17, 33, 50, 67, 83 and 100%) did not affect egg
production and egg weights. However, following a reduction of the metabolizable energy, crude protein, lysine and methionine
in the diets of the same layers at 36-64 weeks of age, egg production, egg
weights and body weights were significantly decreased.
Supplementation
of hull-less barley with 13-glucanase significantly improved weight gains, feed
conversion, passage rate and fat digestibility in 0 - 4 weeks old short comb
white leghorn cockerels; but at 4-6 weeks of age, there was no significant
difference in all the parameters evaluated with or without enzyme supplementation
(52). The general performance was more related to age than
treatment. (47) Evaluated the use of enzyme supplementation in adult
roosters fed barley-containing diets, and reported that enzyme supplementation
increased the overall energy value of the barley grains by 3%, but the general
performance was not affected by supplementation.
Rye
Rye (Secale
cereale L) is believed to have originated from south
western Asia. It is a hardy plant and has the ability to grow in sandy soils of
low fertility; hence it is grown in areas not generally suitable for growing
other cereals. Rye grain is used for making bread, and can also be used as a
livestock feed. The green plant is often used for livestock forage. The protein
value of rye seeds (6.5% 14.5%) compares with that of other grains, and is
considered to be superior to that of wheat and most other cereals in biological
value. However, the availability of the protein is reduced due to the presence
of trypsin and chymotrypsin inhibitors and some constituents like alkyl resorcinols, pectins, pentosans, water soluble glucan, which are also known to
limit its efficient utilization in animal feeding ((53); (43)). Utilization of rye in poultry As
in barley, beneficial effects of enzyme supplementation of rye have been
reported. (54) Fed varying levels of ground rye grain (0, 5, 10, 15, 50
and 25 %) to layers and reported that egg production and feed efficiency were
lower in diets containing higher levels of rye, but other performance
parameters like egg specific gravity, egg weight and haugh
unit were not affected as a result of dietary treatments.
It was concluded that up to 25%
rye can be included in the diets of layers without any adverse effects on
specific gravity, egg weight and / or haugh unit
values. Diets containing more than 40% rye are known to cause depression in egg
production.(46) indicated that enzyme supplementation of rye, barley and
wheat-containing diets in layers diminished the high viscosity of the grains
and resulted in improvement of weight gain, egg production, starch
digestibility and sticky dropping incidence.
5. CONCLUSION AND RECOMMENDATION
The main reason for the
poor animal production is the
inadequate supply and low level of feeding due
to serious shortage of feedstuffs. A major gap
exists between the requirements and supplies
of nutrients for feeding of animal, the nonconventional
feeds could partly fill this gap. More
information is required on chemical composition,
nutritive value and their utilization. Farmers
are not aware of the nutritive value of some
feed sources and the way for their efficient
integration in livestock feeding. The involvement
of local extension agencies in technology
development for efficient use of NCFR,
assessment and transfer is equally important.
Several factors may account for their limited
use, among which is their low nutritive value,
Seasonal availability, high cost of handling
and transportation from the production site to
the farm, presence of anti-nutritional factors.
It is essential to increase feeds by growing
more fodders, propagating agro and social
forestry, improving the nutritive value of crop
residues and utilizing other NCFRs.
Non-conventional
feed resources (NCFR) generally refer to all those feeds that have not been
traditionally used for feeding livestock and are not commercially used in the
production of livestock feeds. The shortage of feed resources for livestock and
poultry feeding diverted majority of research in the field of animal nutrition
to look into all possibilities to overcome this nutritional crisis. The most
viable proposition could be the inclusion new NCFR in ration with suitable
complete feed technology, so as to utilize the feed resources with maximum
efficiency. A major gap exists between the demand and supply of concentrates
and green and dry fodders for feeding livestock in the world.
To overcome
this shortage, it is essential to increase the availability of feed and fodder
for the different productions and functions of the animals. One of the
solutions is also to exploit the use NCFR in the animal feeding system. Some of
the potentially available NCFR are rubber seed cake, Sal seed meal, tapioca
waste, tea waste, babul seeds, slaughter house byproducts, mango seed kernels, nizger seed cake, karanj cake,
guar meal, Prosopis juliflora
pods and cassava leaf meal, Sea buckthorn leaves, cake and pomace, and animal
organic wastes (bovine and poultry excreta) etc. Many of these feed materials
are low in energy, protein, minerals and contain high amounts of lignin, silica
and other nutritionally incriminating substances.
The main
constraints to the use of non-conventional feed resources are collection,
dehydration for high moisture content and detoxification processes. Processing
technologies that are economic and practical are urgently required. The utilization of non-conventional
feedstuffs of plant origin had been limited as a result of the presence of
alkaloids, glycosides, oxalic acids, phytates,
protease inhibitors, haematoglutinin, saponegin, momosine, cyanoglycosides, linamarin to
mention a few despite their nutrient values and low cost implications. These
anti-nutritional factors negate growth and other physiological activities at
higher inclusion levels. These
anti-nutritional factors need to be removed or inactivated by various
procedures before the use of the ingredients in the diet. Great caution should
therefore be taken in the use of these seeds as dietary materials. This is
particularly important since recent studies suggest that long-term exposure to
relatively low levels of some anti-nutritional or toxic factors may have
deleterious effects on body metabolism.
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