Class Roll no.
135 Exam Roll no. 387
The poultry industry in Nepal is developing at
a rapid rate in the present years in both numerical and economical terms.
Observing, comparing and contrasting the data from the past with that of the
present, it is clear that the most important traits of both broilers and
layers, which are also the most economically important, play a vital role not
only in poultry production but also in the genetic improvement of the species.
The traits that are of monetary value are generally known as economic traits.
Egg size, egg quality, age at maturity of the pullet, rate of lay are the major
economic traits of the layers whereas body size and confirmation, meat quality,
feed conversion rate, growth rate are
the major traits of economic importance in broilers. Literature review on the
data of these economic traits shows that average weight of broilers and average
numbers of eggs laid by layers are increasing at an increasing rate after the
shifting from older selection parameter (live weight) to the aforementioned
modern selection parameters of economic traits. Genetic and molecular research
on these economically important traits seems to be one of the most promising
sectors for the future of poultry industry.
Key words: economic traits; poultry; broilers; layers;
parameters of economic traits
Poultry is one of the most important sources
of income due to the high economic values of meat and eggs. Poultry production
also contributes a good share to the national GDP (Recent data shows that the
country has become self-sufficient in terms of eggs).
The poultry industry is a rapidly developing
economic sector, over 65,000 people are employed in commercial poultry farming.
The size of Nepal’s poultry market has grown by 30 percent in the last five
years to Rs.20 billion now, and the GDP contribution of the sector stands at
around 4 percent, according to the latest data compiled by poultry
entrepreneurs. The size of poultry population has significantly increased in
the recent years and the present population of the laying hens is 7290875
(statistical data from MOAC, 2009/2010), the meat production from poultry 17551
metric tonnes (MOAC, 2009/2010), the net egg production from laying hens 6,34,60,000
(MOAC, 2009/2010). According to the Nepal egg producers’ association, poultry
farming contributes around 4 percent to the GDP of the national economy.
Selection of economically important traits of
poultry by the breeders and farmers has played a major role in the rapid
development of this sector. Further understanding of such economic traits will
help maintain this development in poultry sector.
Economic traits are those
which have monetary value in the livestock and poultry production.
Generally, traits are of three categories, Qualitative, quantitative and
threshold traits. Most of the economic
traits are governed by many pairs of genes so known as quantitative traits
or polygenic traits. Quantitative traits have more economic importance than the
qualitative traits. The variations are observed among the individual fowl when they
are measured from most quantitative traits. If there is no variation among
individuals, there would be no need to select or cull animals for genetic
improvement. This is caused by genetic factors (VG), environmental
factors (VG) and the interactions between genetic and environmental
The genetic factor may also
be determined by the interaction among genes and alleles.
VA= variance due to additive effect
VD= variance due to dominance
VI= variance due to
interactions between genes
In the past, live weight of
chicken was considered the most economically important trait. But in the
present, selection is done on various parameters like feed conversion, eggs,
hatchability, weight, breast meat, meat quality, immune response, growth
profile, skeletal integrity, heart/lung fitness, fertility and so on. This
review article discusses these economic traits that are considered for the
selection of poultry for breeding and commercial purposes.
METHODS AND METHODOLOGY
Primary and secondary sources
of information were gathered by internet based research and internet literature
review of the past journals, papers and articles. The thematic area of review
ranged from the traits of poultry concerning economic importance, breeding importance
and socio-economic importance. These specific facts and data were studied
inside the periphery and context of Nepal.
The method for the selection
of the traits of economic importance was through thorough review of the past
and present criteria of selection of such traits which is shown below:
Past: Live weight
Present: Live weight,
hatchability, eggs, heart/lungs diseases, breast meat, meat quality, immune
response, feed conversion, lung fitness, skeletal integrity
The review was done under
these parameters each for broilers and for layers. Specific traits for either
type of chicken was studied which is elaborated under “Results and findings”
RESULTS AND FINDINGS
The review findings is
discussed under the two major headings: Economic traits of layers and Economic
traits of broilers
Economic traits of layers
The trait egg production is
polygenic in nature. It is a low heritable trait, while egg weight is
moderately heritable and influenced by the environment in which they were
grown. The components of egg production are as follows.
1. Age at maturity
It is the age of the bird at
which it lays the first egg. Early maturing hens lay more number of eggs, but smaller
in size compared to late maturing ones. Modern hen starts laying eggs at 2o
weeks. After 72 weeks, the laying hens are culled. Peak period of laying is 5-6
weeks after the laying of 1st eggs. Age at sexual maturity is
determined by both autosomal and sex linked genes.
2. Rate of lay
A hen is sexually mature when
she lays her first egg. The sooner it starts to lay more the number of eggs are
likely to be produced. Probably many genes are involved in its inheritance and
some of these are sex linked.. It is easier to improve the age at the sexual
maturity as it is moderately heritable. Too early maturity may not be desirable
in commercial laying flocks as it affects egg weight. After 1st laying
cycle, the laying rate is reduced.
Persistency refers to the
onset of molting at the end of the laying cycle. It is the measure of the
length of lying cycle. This factor is associated with egg production. The
laying cycle of a hen is terminated by molting. The longer the laying cycle
before the hen enters her laying cycle before the hen enters her molting period,
the better she is for egg production. The laying cycle should be about 300
Broodiness is the condition
in which females stop lying and show the tendency for nesting. It is an ideal
character for the propagation of species in wild conditions, but highly
undesirable for domesticated species for economic purpose. Broodiness is
determined by complementary genes; also it has a sex-linked basis.
5. Egg quality:
External quality of the egg
is judged from its color, shape, texture and breaking strength (or shell
thickness). The internal quality is assessed from the quality of albumen, yolk
and the presence or absence of blood and meat spots. Most of the egg-quality
traits, whether exterior or interior, are highly heritable and respond to
White and brown are the most common egg colors. Hens that lay rough or poorly
textured eggs with thin shells are usually not selected. Breaking strength is
measured by shell thickness. Thick albumen is preferred to thin albumen, so
also eggs with high proportion of yolk. Variation is noticed among strains,
among families and individuals within a family for blood and meat-spots.
6. Body size:
Small or intermediate body
weight is preferred in layers. Optimum body size is very essential in laying
chickens to obtain eggs of satisfactory size. Body weight at all ages is highly
heritable and can be improved by simple mass selection.
7. Feed efficiency:
Most of the improvement in feed efficiency has been achieved
as a correlated response to selection for high growth rate or egg production.
Feed efficiency in layers is measured either as amount of feed consumed in
kg/dozen eggs or as amount of feed consumed in kg/kg egg mass.
8. Fertility and hatchability
Fertility and hatchability for a flock are expressed as
percentage in relation to total eggs set. Hatchability can also be expressed in
percentage as a production of fertile eggs set. Breeds, strains, family as well
as individuals within a family differ with respect to fertility and
hatchability. Age of birds, season, nutritional status of flock, diseases and
management conditions affect both fertility and hatchability. To improve
fertility in a flock the ratio of males to females should be kept optimum.
Economic traits of broilers
1. Feed efficiency:
Feed efficiency is a ratio of feed consumption to weight gain
in broilers. Feed efficiency in broilers has improved considerably in recent
years as a correlated response to high growth rate. Better understanding about
the nutritional requirements and formulation of high energy rations have also
contributed significantly for improving feed efficiency.
2. Growth rate
Rapid juvenile growth is very essential in meat-type birds. It helps to
reduce the cost of production by saving labor through the
application of genetic principles and modern methods of feeding and management
it has been possible to develop rapid growing broilers which at 7-8 weeks weigh
almost the same as 12 week old broilers weighed about 20 years ago. This has
reduced the marketing age and in most cases they are now sold as early as 6
3. Body size and confirmation
Body size is usually
measured by weighing the birds. Large body weight is very important in
broilers. Conformation refers to body proportions and is more important if
broilers are not sold as whole birds. Conformation is determined both by bone
structure and fleshing.
4. Ascites resistance
The rapid growth of
modern broilers is associated with enhanced appetite and high metabolic rate
and, consequently, high O2 demand. The tendency of broilers to
develop Ascites is heritable, but efficacious selection against AS
susceptibility (without affecting the normal expression of other important
traits) requires identification of indirect selection criteria.
5. Heat resistance
production performance and feed conversion efficiency make today’s chickens
more susceptible to heat stress. Vitamins and minerals to satisfy the special
needs during heat stress have been proven advantageous.
6. Eviscerated yield
ratio, the skin-to-bone ratio are all considered an economically important
trait in the broilers. Higher the eviscerated yield, higher the value of the
7. Skin and meat color
The importance of
poultry skin and meat color (both absolute and variations in color) in the
market place has been well established. It has also been reported that these
colors change over time.
Further review of the economic traits showed that the most economically
important trait in broiler (average weight) and layer (average no. of eggs) are
increasing at an increasing rate, which is shown in the graph below:
It showed that the poultry
owners are becoming more and more informant about the economic traits of both
broilers and layers.
To conclude, the traits of
economic importance are those of the monetary values. The Growth in the average
weight of broilers and average number of eggs by layers from the past to the
present times indicate that the farmers and the poultry owners are being more
and more informed about the traits with most economic importance such as egg
size, body growth and confirmation, feed efficiency etc. The increasing
contribution of poultry industry in the national GDP also suggests the same.
However, the potential of
development of such economic traits still remains unexplored as the research at
genetic level and molecular level research are not being conducted at the rate
at which they need to be conducted for the full and optimum exploration of the
traits with economic importance.
S, Ben-David A, Cahaner A. Development of ascites-resistant and
ascites-susceptible broiler lines. Poult Sci. 2007 Jun;86(6), 1283
J. Lara, Marcos H. Rostagno. Impact of Heat Stress on Poultry Production. National
Center for Biotechnology Information, U.S. National Library of Medicine
P, William W. Marion. Eviscerated Yield, Component Parts, and Meat, Skin and
Bone Ratios in the Chicken Broiler. Poultry Science, Volume 52, Issue 2, 1
March 1973, 718–722
M, Fletcher DL. Broiler skin and meat color changes during storage, Poult
Sci. 2002 Oct;81(10): 1589-97
H.C. JIAO, J. BUYSE and E. DECUYPERE. Strategies for preventing heat stress in poultry.
6. Mishra B, Traits of economic
importance in poultry, bijeshmishra.wordpress.com/2013/01/27/traits-of-economic-importance-in-poultry/#more-1624
7. Dhakal S, Lamichhane S, et
al., Traits of economic importance in
poultry and its implication in genetic improvement programme, https://www.scribd.com/doc/48643480/Economic-Traits-of-Poultry
This review paper on the
topic “Economic traits of Poultry” is prepared as an assignment of course ANB
301, Principles and Practices of Animal breeding. The review discusses on the
economic traits of poultry (broilers and layers) and highlights its importance
in the poultry industry of the country and in animal breeding. During reviewing
and after the completion of the review paper, most of the things regarding
economic traits of poultry were understood, of which Asst. prof. Nirajan
Bhattarai, Department of Animal Breeding and Biotechnology is to be thanked
immensely. I also extend my gratitude
towards my respected seniors Achyut Acharya and Bimochan Paudel of B.VSc. and
A.H. 7th semester for guiding
me. Last but not the least, I am the most thankful to my batchmates Bishal
Modi, Kanti Thapa and Sushil Sapkota for helping me complete this review paper.