




































In ternationa l
Scholars
Journa ls

 

African Journal of Pig Farming ISSN 2375-0731 Vol. 4 (6), pp. 001-009, June, 2016. Available online at 
www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 
 

Review 
 

Energy and protein requirements of pigs and the 
utilization of fibrous feedstuffs in Nigeria 

 
Adesehinwa, A. O. K. 

 
Swine Research Unit, Livestock Improvement Programme, Institute of Agricultural Research and Training, 

Obafemi Awolowo University, P.M.B. 5029, Moor Plantation, Ibadan. Nigeria. E-mail: 
aokadesehinwa@yahoo.com. 

 
Accepted 11 December, 2015 

 
A sound nutrition programme, which allows the understanding of the interaction between nutrients and requirements 
for different levels of production, is essential for raising swine profitably. Nutrient requirement is that amount of each 
essential nutrient that will result in maximum production with a minimum of feeding. Hence, high quality feeds 
containing the essential nutrients in the amounts necessary to meet the animal’s requirements must be provided, in 
order to attain an optimal rate and efficiency of growth from birth to market. The formulation of balanced diets that 
provide the correct amounts and proportions of these nutrients is essential to support the requirements for 
maintenance, growth and reproduction of the animal. It is only then that the feeding programme can be said to have a 
major impact on the performance and the overall profitability of the swine herd. The scarcity of conventional feeds has 
hindered the growth and development of the livestock industry in Nigeria. The general shortage of energy and protein 
feeds appear to be more severe for non-ruminants that depend to a great extent on compounded feeds, especially 
pigs, which are bulk feeders. There are a number of agro-industrial by-products, farm waste or crop residues that have 
been exploited as alternative feed sources for the high energy cereals. This has made a substantial contribution 
towards better and more economic feeding of non-ruminants. However, fibrousness, a feature of most locally 
available agro-industrial by-products and wastes has limited their use. 

 

Key words: Feeding programme, balanced diets, fibrous feedstuffs. 

 
INTRODUCTION 

 
In recognition of the potential of pig as a prolific and fast 
growing animal, as well as a good converter of feed to 
meat, many Nigerian farmers have embarked upon 
intensive production of pigs. This is an effort geared 
towards increasing animal protein supply, at reduced cost 
for human consumption (Adesehinwa et al., 1998). Pig 
production represents the fastest means of correcting 
animal protein shortage in Africa. This is because, apart 
from their high rate of reproduction, poultry and pigs are 
characterized by the best efficiency of nutrient trans-
formation into high quality protein (meat), although the 
cost of the transformation is very high (Tewe and 
Egbunike, 1988). Therefore, nutrient supply has to be 
judiciously manipulated to ensure the production of meat 
at economic rates. There exists in country some agro-
industrial by-products and crop residues that can be used 
as total or partial replacements for the conventional 
ingredients in finished livestock feeds. Pigs are capable 
of converting these agro-industrial by-products or 

 
 
 

 
„wastes‟ of all kinds (which will normally be discarded by 
humans) into wholesome animal protein useful to the 
human being.  

The NRC (1988) recommendations of nutrient require-
ments, assumed to contain 90% dry matter and based on 
corn-soybean meal diet has been questioned in the 
tropics by the depressed feed intake, hence, depressed 
nutrient intake, resulting from the high ambient tempera-
ture and humidity prevalent in the tropical environment 
(Tewe and Adesehinwa, 1995a). Rao et al. (1976) con-
cluded that animals in the tropics performed better when 
fed on an energy level 10% lower than the NRC 
recommendations. Fetuga (1984) in a similar study on 
energy, protein and amino acids requirements of pigs 
raised in the humid tropic concluded that a higher dietary 
protein is required.  

Nutrient requirement was however reported (Conrad, 
1984) to be such that it gives an account of the amount of 
each essential nutrient that will result in maximum pro- 



 
 
 

 

duction with a minimum of over-feeding. He observed that 
these requirements must include a factor of safety so that 
normal variation in the composition and nutritive value of 
feeds and in the functional capacities of animals will 
never result in under feeding. It should be noted that the 
safety cannot be introduced until minimum requirements 
have been established. The minimum requirements of the 
essential nutrients have been report-ed for all classes of 
pigs both in the temperate regions (Cooke et al., 1972; 
Wylie and Owen, 1978) and the tropical areas of the 
world (Devendra and Parris, 1970; Fetuga, 1972, 1984; 
Babatunde et al., 1972; Dividich and Canope, 1978). 
 
 
 
ENERGY REQUIREMENTS 

 

The energy requirements of pigs are very variable. They 
are higher with increasing body weight, as basal meta-
bolism and maintenance requirements are proportional to 
live weight as well as to growth rate (Serres, 1992). The 
more the animal grows, the more it requires energy to 
sustain this growth. From weaning until 20 kg, 1 kg of live 
weight represents about 3000 calories while at 90 kg, it is 
5000 calories and it is beyond 6000 calories for fat pigs 
(Serres, 1992).  

Energy supplied to the animals may be measured as 
gross, digestible or metabolizable. The gross being that 
amount of energy liberated during complete combustion 
of the diet, which is of little practical value as a measure-
ment. The digestible energy (DE) is that proportion 
remaining after digestion and may be estimated from the 
difference between energy of food ingested and energy of 
faeces voided. While, the metabolizable energy (ME) is 
the digestible less energy lost in the urine (Serres, 1992). 
Farrell (1978), Agricultural Research Council (1981), and 
Morgan and Whittemore (1982) suggested that DE is 
preferable in describing the energy content of swine 
feeds because DE is more easily and precisely deter-
mined than ME. The gaseous loss of energy in the 
digestive tract of swine is usually between 0.5 and 1.0% 
DE (Verstegen, 1971; Fuller and Boyne, 1972). The 
values are small and not measured hence they are 
ignored (NRC, 1988). The quality and quantity of protein 
in the diet was reported (May and Bell, 1971; den Hartog 
and Verstegen, 1984) to affect the relationship between 
ME and DE.  

Metabolizable energy decreases if protein is of poor 
quality and with excess protein because the amino acids 
not used for protein synthesis are catabolized and used 
as a source of energy and the nitrogen is excreted as 
urea (NRC, 1988). The energy level of the diet must be 
related to other components. Longe (1988) reported that 
good diet formulation required that a balance be attained 
between the percentage crude protein and the number of 
energy units in the diets. This view was supported by 
Fashina (1991) who reported the existence of a relation-
ship between the dietary energy and protein requirements 

 
  

 
 

 

of pigs. Energy : protein ratios that deviate from those 
that will make animals perform optimally will therefore 
result in marked difference in performance (Longe, 1988).  

The net energy (NE) is the best measure of energy 
available to an animal for maintenance and production 
(NRC, 1988), and it is lower than the ME because of 
losses associated with biochemical pathways within the 
animal (Serres, 1992). It defines the efficiency of 
utilization of the productive purposes. The NE value is 
influenced by the composition of the feedstuff, level of 
feed intake, balance of nutrients in the diet, age, breed, 
sex, body condition of the pigs, environmental conditions 
under which the animal is maintained, and percentage of 
energy retained as protein (Farrell, 1979; van der Honing 
et al., 1985).  

The DE requirement of the growing pig was described 
by NRC (1988) as the sum of its requirements for main-
tenance, protein retention, fat retention and cold thermo-
genesis. Maintenance energy requirements include 
needs for all body functions and moderate activity and it 
is expressed on a metabolic weight basis. Although the 
mean energy cost per kg of protein or fat deposited are 
approximately equal (Wenk et al., 1980), 1 kg of lean 
muscle tissue is only 20 to 22% protein. Therefore, the 
energy cost for muscle production is considerably less 
than that for fat production (NRC, 1988). The cold 
thermogensis influences energy requirements when the 
ambient temperature is below the critical temperature 
(which is the point below which an animal must increase 
heat production to stay warm).  

The energy content of the diet therefore generally 
controls the amount of feed consumed AD LIBITUM daily 
(ARC, 1981; Cole, 1984) and pigs will compensate for 
decrease or increase in the nutrient density of the diet by 
increasing or decreasing their feed intake. This com-
pensation normalizes energy intake within limits (NRC, 
1988). However, voluntary feed intake varies con-
siderably from day to day and among individual pigs 
(Frank et al., 1983).  

The metabolic utilization of the metabolizable energy or 
heat increment was reported by Noblet et al. (1994) to 
vary according to the diet‟s chemical characteristics and 
type of production (maintenance, growth, milk secretion, 
protein and fat deposition etc). The average efficiencies 
of utilization of the ME for these different purposes have 
been shown to differ markedly in swine: approximately 
80% for fat gain (kg) or maintenance; 60% for protein 
deposition; 75% for weight gain (kg) during growth and 
70% for milk (ARC, 1981; Noblet et al., 1990, 1991 and 
1993). 
 
 

PROTEIN REQUIREMENTS 

 

In swine nutrition, a good quality protein is one that 
provides the ten essential amino acids required for the 
normal body function in the amounts and proportions 
necessary for the particular need of the pig (Adesehinwa 



 
 
 

 

and Ogunmodede, 1995). Traditionally, swine diets are 
formulated on the basis of crude protein. This refers to 
the nitrogen content of the feedstuff x 6.25 (NRC, 1988). 
Amino acids are critical nutrients required by all classes 
of swine for the physiological processes of maintenance, 
growth, gestation and lactation (Fashina, 1991). Hence 
protein levels are established for the various weight 
classes of pigs so that the most limiting amino acid 
(lysine) will be present in adequate amounts (Adesehinwa 
and Ogunmodede, 1995).  

Amino acids are reported to be the chemical 
components of protein and are generally supplied to the 
pig from the crude protein in the diet (Fashina, 1991). 
Failure to supplement a low protein diet or feedstuff with 
sufficient amounts of high quality protein source was 
reported by Adesehinwa and Ogunmodede (1995) to 
result in poor growth, inefficient feed utilization, increased 
carcass fatness, general unthriftiness and or reduced 
reproductive performance. The capacity of the diet or 
feedstuff to provide sufficient indispensable (essential) 
amino acids and nitrogen for the synthesis of dispensable 
(non essential) amino acids determines the adequacy of 
the dietary protein level (NRC, 1988). Hence, the need for 
a nutritionally balanced ration in an economically viable 
pig production system (Adesehinwa, 1992).  

Lower levels of dietary protein are required to maximize 
growth and efficiency of gain for a protein source with 
well balanced amino acid profile (Bender, 1975) in con-
trast to a protein source with poor amino acid pattern 
where more is required, to be efficiently utilized 
(Adesehinwa, 1992). Protein quality therefore becomes 
synonymous with amino acid balance. The amino acid 
requirements expressed as a percentage of the diet 
decrease as the pig becomes heavier, that is, the re-
quirements are greatest during the rapidly growing stages 
of the young animal (Conrad, 1984).  

The young animal was reported as not only growing at 
a more rapid rate as indicated by the percentage increase 
in the weight but that the proportion of the protein in the 
entire body weight is higher than during the finishing 
period. These changes in the rate of growth and body 
composition are the basis for recommending diffe-rent 
dietary protein levels to meet the amino acid 
requirements during the life of the pig (Fanimo, 1991). 
Fetuga (1984) reported the protein and amino acid 
requirements for the tropics to be higher than those 
recommended by NRC (1979) for the temperature zones. 
This view was also reported in an earlier work by 
Babatunde et al. (1972). The variation in the recommend-
ed protein and amino acid allowances for different 
classes of pigs was attributed in part to variations that 
exist in the protein sources or protein qualities used. 
 

 
UTILIZATION OF ALTERNATIVE FEEDSTUFFS BY 
PIGS 

 

Livestock production in Nigeria which had its boom in the 

 
 
 
 

 

late 70s is now taking a downward trend because of the 
high cost of production. Commercial production takes two 
distinct forms or levels. There are large scale and small 
scale producers, each having its operational characte-
ristics. However, for the successful take-off of either of 
the two scales of production, availability of feedstuffs in 
the right quality, quantity and price are very important.  

The astronomic rise in the price of livestock feeds has 
recently reached an alarming proportion. Scarcity and 
outright non-availability of raw materials for feeds has 
hampered production and expansion of the livestock 
industry. Stock population decrease is being embarked 
on by some farmers in order to meet the increasing feed 
bills and in most cases terminating in outright withdrawal 
from production. This upward trend in feed cost is due 
largely to steep prices of and diversified use of maize, 
increasing prices of guinea corn, groundnut cake, 
soybean products and fish meal. These shortages have 
either kept most feed mills in the country idle or ope-
rating, well below production capacity. These increases in 
prices over the years have also resulted in increased 
prices of some livestock products.  

Apart from the high prices, other factors include, 
astronomical and uncontrollable shortage of basal feed 
ingredient, the cereal grains; growing shortage of oil seed 
cakes which Nigeria used to produce and export in large 
qualities; adulteration of feed ingredients (particularly 
common with fish meal and groundnut cake, which 
suppliers now blend with brown sand and saw dust); lack 
of quality control body or the inefficiency of such body to 
monitor ingredient and finished feed composition and 
quality, and the seeming lack of government incentive to 
feed manufacturers or producers.  

While the shortages of raw materials for livestock feeds 
production, particularly poultry and pigs are numerous, 
however, the emphasis seems to be on the shortage of 
grains (basal energy feed) and protein supplements 
which together constitute about 70-80% of finished 
products (Noblet et al., 1994). With the ban on their 
importation and the increasing demand for maize for 
industrial use as livestock feeds, beer production, baby 
foods, local consumption and staple food, the need to find 
substitutes to these items becomes urgent. Such 
substitutes must be readily available or should be pro-
duced in commercial quantities at lower cost. This in 
essence means shifting to ingredients for which there is 
less competition by other secondary industrial users and 
producers. 
 
 
ALTERNATIVE ENERGY SOURCES 

 

Maize is a major grain crop grown in Nigeria and is used 
mainly in human foods as well as energy feed ingredient 
in animal production. Its use in the brewing industry and 
production of composite flours for confectioneries has 
robbed the livestock industry of its fair share of the total 
maize available in the country (Longe, 1988). This is re- 



 
 
 

 

flected in the high prices of the finished feeds containing 
maize. Since the feed crisis of 1983, efforts have been 
made to seek alternative energy sources to maize, and 
some other conventional feed ingredients.  

These alternative energy sources must be locally 
available, cheap and be able to replace a certain 
proportion, if not all of maize normally incorporated in 
diets of pigs without adverse effect on performance and 
product. Most of these energy sources, if not all, are 
agro-industrial by-products that are low in energy, high in 
fibre and bulky in nature. They were hitherto used as 
energy diluents in swine ration (Tegbe et al., 1995). 
Generally, except for rice offal and cassava peel meal, 
the crude protein content of most of the agro-industrial 
by-products are higher that that of maize. Their essential 
amino acid profiles also compare favourably with that of 
maize, thus showing that they could serve as sources of 
some essential amino acid in livestock feed (Tegbe et al., 
1995).  

Feed ingredients which have been successfully 
incorporated into the diets of pigs as alternative energy 
sources include wheat offal (Tegbe et al., 1984; Tegbe et 
al., 1986), brewers dried grains (Tegbe, 1983 and Tegbe, 
1985a), rice offal (Tegbe et al., 1984 and Tegbe, 1985b), 
rice mill by-product (Attah et al., 1991), sorghum offal 
(Adesehinwa, 1992; Tegbe et al., 1995), cassava peel 
meal (Tewe and Oke, 1983; Nghi, 1986; Tewe et al., 
1987; Iyayi and Tewe, 1988; Tewe and Egbunike, 1988; 
Tegbe et al., 1992a; Tewe and Adesehinwa, 1995a), 
palm kernel cake (Tegbe and Jegede, 1988; Tegbe et al., 
1992b; Jegede et al., 1994; Tegbe et al., 1995) and 
maize offal (Tewe, 1988a; Longe and Fagbenro-Byron, 
1990; Ande, 1992). 
 

 

ALTERNATIVE ANIMAL AND PLANT PROTEIN 
SOURCES 

 

The alternative animal protein sources are animal by-
products obtained primarily from slaughter houses, 
surplus milk products and aquatic sources or wastes 
arising from animal production (Sonaiya, 1988). Virtually 
all these by-products can be used in the formulation of 
livestock feeds to supply protein or amino acids and 
minerals, in appreciable amount. They include meat and 
bone meal, blood meal, chicken offal meal, snail meal, 
prawn dust, shrimp meal, insect and fly larvae meal. 
Other animal protein sources available for livestock feeds 
include meat scrap, hatchery by-product meal and, 
feather and hair meal. The sources of plant origin include 
soybean meal, groundnut cake sunflower meal and 
rapeseed meal. Soybean meal is usually the most 
economical source of high quality plant protein available 
(Adesehinwa and Ogunmodede, 1995) because in terms 
of quality of amino acid content and ratio, it compares 
favourably with animal protein sources in most swine 
diets.  

Most pig diets in the temperate countries have been al- 

 
  

 
 

 

most exclusively based on maize and soybean meal, 
while in Nigeria, the diets have been largely based on 
maize and groundnut meal or cake. It is only in recent 
times that the extensive use of soybean meal became 
prominent in pig feeding. The depletion of a large number 
of commercial pig and poultry stock has be reported to be 
due to the scarcity and high cost of groundnut cake, 
soyabean and fish meals (Tewe, 1988b). 
 
 
UTILIZATION OF FIBROUS FEEDSTUFF IN PIG 
NUTRITION 

 

Various studies suggest that the pigs can utilize fibre for 
their growth, since fibre can be degraded by microbial 
fermentation. However, this process is reported to be 
confined to the lower part of the gastrointestinal tract and 
the products are volatile fatty acids, which can contribute 
significantly (5-30%) to the net energy requirements of 
pigs (Kass et al., 1980; Ehle et al., 1982; Rerat et al., 
1987).  

Fibrousness of feedstuffs (mostly of by-products of 
plant origin) is important in relation to their feeding value 
to pigs. The fibrous components of plant materials are 
cellulose, hemicellulose and lignin. The influence of crude 
fibre on organic matter digestibility varies from feed to 
feed, depending on the special characteristics of the 
crude fibre in individual feeds (Kidder and Manners, 
1978). The fibrous portion of feed, being fairly indigestible 
to pigs, influences the digestibility of the other consti-
tuents by excreting a protective action, encasing these 
constituents in a digestion-proof shield, as it were. 
However, for efficient pig feeding, some form of physical 
treatment of cereal grains is essential to the breaking 
down of the fibre encapsulating the more soluble consti-
tuents so that digestive secretions can penetrate more 
completely (Kidder and Manners, 1978).  

The addition of fibre to swine diets decreases the 
digestible energy (DE) and metabolizable energy (ME) 
concentration of the diet (Kennelly et al., 1998; Kennelly 
and Aherne, 1980) and often results in bulk feeds. In-
creased feed intake generally results as the pig attempts 
to maintain DE intake (Baird et al., 1975; Agricultural 
Research Council, 1981; Low, 1985). This could increase 
the length and weight of gastro-intestinal tract even when 
the fibre is eventually fermented (Stanogias and Pearce, 
1985a and b). This change has been associated with 
physical properties of fibrous feeds such as its bulk 
(Longe and Fagbenro-Byron, 1990).  

When dietary crude fibre exceeds 10-15% of the diet, 
feed intake may be depressed because of excessive bulk 
or reduced palatability (Braude, 1967). Low energy (as 
obtains for most high fibre diets) will support growth rates 
equal to those of pigs fed higher-energy diets at low 
temperature but usually depress the growth rate during 
periods of high temperatures (Coffey et al., 1982; Stahly, 
1984).  

Several researchers have tried to establish a relationship 



 
 
 

 

between DE and the fibrous components of the diet 
(Drennan and Maguire, 1970; King and Taverner, 1975; 
Henry, 1977). Longe and Fagbenro-Byron (1990) later 
reported the apparent digestible energy to be influenced 
by the level of dietary neutral detergent fibre (NDF), while 
Henry (1977) showed it to have an inverse relationship to 
the fibre content, the former decreasing as the latter 
increases. However, the extent of the decrease in DE 
varied with the feedstuffs, depending on the composition 
of the cell wall constituents, particularly the ADF : NDF 
ratio (Pond, 1987).  

Utilization of crude fibre by non-ruminant has been 
shown to vary considerably depending on the fibre source 
(Laplace and Lebas, 1981), degree of lignification 
(Forbes and Hamilton, 1952), level of inclusion (Farrell 
and Johnson, 1970; Just, 1979) and extent of processing 
(Saunders et al., 1969; McNab, 1975). The level of the 
fibrous feedstuff used in pig diets varies with the 
proportion of the cell wall constituents and it is generally 
thought that high fibre diet (>25% cell wall contents) will 
decrease growth efficiency in pigs (Longe and Fagbenro-
Byron, 1990). Stahly and Cromwell (1986) reported that 
the digestibility of NDF is optimized in pigs fed diets 
containing 15% or less NDF.  

Fibre utilization is also influenced by the physical and 
chemical composition of the total diet (Myer et al., 1975), 
level of feeding (Cunningham et al., 1962) age and 
weight of animal (Zivkovic and Bowland, 1970), adapta-
tion to the fibre source (Pollman et al., 1979) and 
individual differences among pigs (Keys et al., 1970 and 
Farrell, 1973). When these factors are considered, it is 
not surprising that the digestibility of crude fibre has been 
shown to vary between 0 and 97% (Rerat, 1978) and that 
the literature contains conflicting reports about effects of 
crude fibre on the digestibility of nutrients (NRC, 1988).  

There is disagreement concerning the influence of 
crude fibre on protein digestibility (NRC, 1988). Several 
reports suggest that when the source of crude fibre does 
not contribute significant amounts of protein in the diet, 
then an increase in the level of fibre does not affect 
protein digestibility significantly (Eggum, 1973; Kennelly 
and Aherne, 1980). Other researchers have observed, 
however, that an increase in the dietary level of fibre 
decreases protein digestibility (Kass et al., 1980; Frank et 
al., 1983). Just (1982) reported that an increase in dietary 
fibre by 11% depressed digestibility of gross energy by 
approximately 3.5%.  

Longe and Fagbenro-Byron (1990) in their studies on 
fibrous waste and by-products for pig feeds in Nigeria 
concluded that fibre sources in general, may be best 
suitable for adult pigs. This, they attributed to their 
requirement for lower dietary energy to obtain a desirable 
carcass lean: fat at slaughter. This agreed with the 
significant potential for fibre degradation in the pig large 
intenstine (Varel, 1987). The appreciable contribution to the 

total digestible energy (Rerat et al., 1987) encourages giving 

serious consideration to these fibrous materials and their 
potential as feed resources in pig production. Though, 

 
 
 
 

 

Longe and Fagbenro-Byron (1990) did not fail to add that 
the economics of production will need to be considered 
also in determining the suitability of fibrous materials as 
feed ingredients. However, high fibre diets were reported 
to be associated with some cardiovascular risks such as 
low density lipoprotein and total cholesterol (Ande, 1992) 
and reduction in blood glucose and serum insulin 
concentrations (Dodson et al., 1981). 

 

NUTRIENT DIGESTIBILITY IN PIGS 

 

The pig is used to convert a variety of foods/feeds into 
meat for human consumption. The efficiency with which 
this conversion is carried out is of crucial importance to 
the pig industry. The efficiency of the conversion is 
dependent on the digestibility of the feeds and their 
constituents (Kidder and Manners, 1978). The proximate 
analysis of the feedstuffs provides vast amount of data on 
the crude composition of the feed (dry matter, ash, 
organic matter (dry matter minus ash), crude protein (N x 
6.25), ether extract, crude fibre and nitrogen free 
extractives) (Church, 1991). The measurement of the 
inputs and outputs of these components in feeds and 
faeces determine the extent of digestibility of the 
components.  

The concept of nutrients digestibility assumes that the 
feed residues found in feaces are merely the result of 
inefficient digestion and nothing else (Kidder and Manners, 
1978). However, they reported that the position is more 
complex, because faeces contain undigested feed residues, 
unabsorbed digestive secretions, intestinal cells which are 
continually being sloughed off, as well as dead micro-
organisms and the products of microbial fermentation. 
The unabsorbed residues of secretions and cellular 
debris, predominantly proteineous in nature are of endo-
genous nitrogen source.  

Generally, the digestibility measurements are reported 
in terms of apparent digestibility. This is so because, it is 
difficult to devise appropriate corrections for the amount 
of digestive secretions and other waste products which 
are irretrievably mixed with the undigested feed residues 
of which the faeces are largely composed (Kidder and 
Manners, 1978; Church, 1991). The coefficient of appa-
rent digestibility of dry matter provides a valuable index of 
the overall digestibility of the diet. However, a more 
complete picture of digestibility is obtained with the 
apparent digestion coefficients of the individual nutrient 
(crude protein, ether extract, crude fibre, ash and nitro-
gen free extractives) contained in the diet or feedstuffs. 

 

ENERGY PREDICTION IN PIG DIETS 

 

The cost of feed represents over 70% of the total cost of 
pig production (Frape and Tuck, 1977; Adesehinwa and 
Ogunbodede, 1995; Tewe and Adesehinwa., 1995), the 
energy component being the greatest proportion (Frape 
and Tuck, 1977; Noblet and Perez, 1993; Noblet et al., 



 
 
 

 

1994). Therefore, it is important to know precisely both 
the energy requirement of the pigs and the energy value 
of feeds. The types of pig feeds used in the tropics vary 
greatly, and since many by-products are used in place of 
cereals, the variation in nutritive values between and 
within feeds may be considerable (Lekule et al., 1990).  

The evaluation of the energy content of feeds is usually 
based on their digestible or metabolisable energy values 
(NRC, 1988; INRA, 1989; Noblet and Perez, 1993). The 
energy value of feed ingredients or feeds enables the 
predictability of the amount of pig meat produced from a 
given feed and allows the achievement of the least-cost 
formulation of diets of given energy densities (Frape and 
Tuck, 1977). This assists the pig producer to produce a 
uniform carcass quality at a feed cost commensurate with 
maximum profit.  

The determinations of the metabolisable energy values 
are time-consuming and expensive, and the chemicals 
required are not readily available in many laboratories in 
the developing countries (Lekule et al., 1990). Hence, the 
apparently digested energy of feeds may be assessed 
from faecal output by crude chemical analysis of feed and 
faeces for crude protein, ether extract, crude fibre and 
nitrogen free extractives. The summation of these values, 
each multiplied by its characteristic coefficient yields a 
value representing the heat of combustion of the 
apparently digested product of 1 kg dietary dry matter 
(Frape and Truck, 1977).  

As consequence of the cost of biological determina-
tions and because of the inherent variability between 
samples of the same ingredients, a number of equations 
have been derived to predict the digestible and meta-
bolisable energies from easily determined chemical 
characteristics of the diets. It should however, be noted 
that these equations are based on some referenced 
sample feedstuffs. Morgan et al. (1975b) predicted the 
following equations: 
 

DE = 0.460CP + 0.625EE + 0.377NFE – 21.05 (R
2
 = 

0.95) 
 

ME = 0.416CP + 0.605EE + 0.367NFE – 20.06 (R
2
 = 

0.94) 

 

Where DE is the digestible energy, ME is the 
metabolisable energy, CP is the crude protein, EE is the 
ether extract and NFE is the nitrogen free extractives. 
However, it was reported that the starch content of the 
nitrogen free extract decreases as the fibre contents 
increase (Nielsen, 1970). In the contribution of Lekule et 
al. (1990), they showed the crude fibre to have the 
highest correlation to the ME content and the relationship 
was shown as: 
 

ME (MJkg
-1

 DM) = 16.81-0.031CF (gkg
-1

DM) (R
2
 = 0.68) 

 
Where CF is the crude fibre and DM is the dry matter. 

The high correlation has also been shown by Just et al. 

 
 
 
 

 

(1984), Fernandez and Jorgensen (1986) and Morgan et 
al. (1987), among others. The best equation with two 
variables was reported by Lekule et al. (1990) as: 
 

ME (MJkg
-1

DM) = 16.34 - 0.034CF (gkg
-1

DM) + 0.003CP 

(gkg-1DM0 (R
2
 =0.73) 

 
While they reported the best three-variable equation as: 
 

ME (Mjkg
-1

 DM) = 3.36 + 0.016CP + 0.029EE + 0.013SC 

(R
2
 =0.83) 

 
Where SC is soluble carbohydrate  
Noblet and Perez (1993), in their study later predicted 
thus: 
 

DE = 4151 – 12.2Ash + 2.3CP + 3.8EE – 6.4CF (R
2
 = 

0.89) 
 

ME = 4168 – 12.3Ash + 1.4CP + 4.1EE – 6.1CF (R
2
 

=0.88) 

 

The digestible energy of feed is by no means 
recoverable in useful animal products (Frape and Tuck, 
1977). Some workers, therefore, advocated the deter-
mination of metabolisable energy, which is that, available 
to the tissue for productive use. In pig, methane losses 
are small for normal diets, about 0.01 of the digestible 
energy (Bowland et al., 1970) and therefore, in practice, 
the metabolisable energy is simply assumed to be that 
portion of the digestible energy not lost in the urine 
(Frape and Tuck, 1977; Serres, 1992). Urinary nitrogen 
losses were reported to increase as dietary protein is 
raised, so that high protein ingredients are likely to incur a 
greater handicap than cereals in the computation of their 
metabolizability. Thus, metabolisable energy is affected 
by dietary protein level and by the way it is utilized and 
so, it is not a constant characteristic of an ingredient. 
 

Metabolisable energy may, therefore, be calculated 
from the proximate composition of digestible dietary 
components as in the equation above, or as a proportion 
of the digestible energy: approximately 0.98DE for 
cereals and 0.95DE for protein concentrates (Frape and 
Tuck, 1977). Morgan et al. (1975a) allowed for variation 
in protein intake, thus: 
 

ME =DE (0.997-1.88 x10
-4

CP1) (R
2
 =0.88) 

 

Where CP1  is crude protein in g/kg dietary dry matter. 
While, Lekule et al. (1990) predicted: 
 

ME (MJkg
-1

DM) = 0.08 + 0.96DE (MJkg
-1

DM) (R
2
 = 0.96). 

 
The relationship was found to be very close and of the 

same magnitude as that found by Just (1982). The 
energy value of the diet could then be used to predict the 
amount of pig meat (pork) to be produced from a given 



 
 
 

 

amount of feed (which is an inverse of the amount of feed 
consumed per kg liveweight gained) or to achieve the 
least-cost formulation of diets of given energy densities.  

This is the major determinant of the nutritive value of a 
feedstuff and its assessment is therefore of great 
importance for diet formulation. This is of special practical 
importance in the developing countries where deter-
mination of proximate components in feed and feces are 
relatively more feasible compared to the use of sophis-
ticated gadgets, required in other methods of energy 
value determinations, which are not available. 
 

 
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