IMPROVEMENT IN EGG PRODUCTION TRAITS IN THE LIGHT LOCAL CHICKEN ECOTYPE USING A SELECTION INDEX

ABSTRACT

Fifty hens and five cocks from a random mating population of light local chicken ecotype (LLCE) were mated and the fertile eggs hatched to obtain the parent generation (G0) used for this study aimed at improving egg production traits in the LLCE using a selection index.  The hens were monitored  for short-term  (90-days  from first day of  lay) egg production  traits namely: Body Weight at First Egg (BWFE), Average Egg  Weight (AEW) and Total Egg Number (TEN).  Data obtained were subjected to statistical analysis using SPSS (2001) and paternal  half-sib  model  with Harvey  (1990)  to estimate  descriptive  statistics  and genetic parameters respectively.  These were employed in constructing the selection index.  Selection for all the selection criteria (BWFE, AEW and TEN) was in the positive direction.  Selected parents  were  mated  to  produce  next  generations  –  G1   and  G2.    Selection  differentials, selection intensities  and genetic response due to selection were also estimated.   A control population  which  spanned  for  three  generations  (each  generation  had  its  own  control population) was used to monitor environmental changes and to estimate the genetic changes due to selection.  There were significant increases (P<0.05) in BWFE, AEW, and TEN in the selected populations over the three generations of study such significant increases (P<0.05) were  not  observed  in  the  control  population.    Heritability  estimates  for  all  traits  in  all generations and populations were moderate to high.  The heritability of the index was also moderate.    Such  moderate  to  high  heritability  estimates  indicate  high  additive  genetic variances, implying that these traits were most passed on from the parents to their offspring. Low to high positive genetic and phenotypic correlations was observed between BWFE and AEW in all populations of study.  The genetic correlation and phenotypic correlation between BWFE  and  EN,  and  between  AEW  and  EN,  was  moderate  to  highly  negative  for  all generations and populations of study.  A positive genetic correlation was observed between AEW  and  TEN in G2  of the selected  population.    A cumulative  selection  differential  of

269.38g,  1.58g  and  3.88  eggs  were  obtained  for  BWFE,  AEW  and  TEN  respectively.

Selection  response  for  traits  increased  over  the  generations  in  a  fairly  linear  manner. Realized response per generation was estimated to be 94.22g, 0.84g and 4.85eggs for BWFE, AEW and TEN respectively.   It is evident that the simultaneous inclusion of BWFE, AEW, and TEN in a selection index generally improved the performance of selected birds over the generations in the Light Local Chicken Ecotype.

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF STUDY

The report of the 4th Food and Agriculture Organization (1973) expert consultation on Animal Genetic Resources presented two important objections concerning the endeavour to improve and conserve the local chicken.   The first was as to whether the local strains still possess genes, which are useful to the vastly improved exotic strains given the centuries of genetic screening, which the latter have undergone.  The second objection pointed to the fact that the process of further screening of the local chicken  will be long, laborious and very expensive.   However, the results of recent research using local chicken (Ikeobi and Peters,

1996; Ayorinde  et al., 2001; Udeh and Omeje, 2001) indicate that the local chicken  is a repository  of advantageous  genes.   Secondly,  with molecular  genetic  techniques,  genetic improvement  of  the  local  chicken  is  fast  and  less  expensive.    Incidentally,  third  world countries,  which  established  breeding  programmes  based  on  the  dilution  of  indigenous germplasm  by extensive  crossbreeding  programme,  suffered  failures.  Those  failed efforts have made livestock breeders aware of the importance of indigenous breeds in overall food production systems – because of their adaptation to the environmental stress of the tropics.

In spite of the large number of livestock and poultry in the nation, the animal protein intake per caput per day still falls below the minimum requirement level recommended by UN/FAO (Ayodele and Ajani, 1999).  This has been traced to the low production of animals, which could be due to genetic and/or environmental constraints.  The above underscores the need to improve the level of animal protein production in Nigeria.  Of greater importance is the improvement of the poultry sector since it has a number of advantages – including short generation  interval,  and  production  of  large  number  of  offspring,  due  to  its  peculiar reproductive  traits  (Ibe,  2001).    Furthermore,  poultry  meat  is  generally  accepted  by  all religions and societies.

In  many  countries  the  development  of  agriculture  and  breeding  programmes  has resulted  in  serious  changes  in  poultry  breeding  stocks  during  the  last  decades.     The establishment of breeding institutions has led to a pronounced supra-regional propagation of certain chicken breeds due to improvements  in performance.   As a  consequence  the local breeds have decreased continuously  to the same extent as the  preferred high performance breeds  have  expanded.    For  instance,  it  was  in  a  bid  to  satisfy  the  need  for  increased production and profitability in intensive production systems to meet the increase in demand for animal protein by the populace that new high yielding and fast growing poultry breeds

were introduced into the existing poultry production systems in Nigeria since the late 1950’s (Obioha, 1992).   Incidentally, such introduction has resulted in non-integration of the local breeds considered as ‘low producers’ into large-scale poultry production.

Nigeria  has  rich  chicken  genetic  resources.    A  good  number  of  workers  have documented the characteristics of the local chicken, in terms of morphological, physiological, behavioral and production attributes.  Nwosu (1990) gave a review of these.  Ibe (1990a, b) identified  some  major  genes of tropical  relevance  in Nigerian  local  chicken  populations. Perhaps, the most distinguishing feature for physical characterization at present is the body weight of the local chicken found in the various ecological zones of the country (Olori and Soniaya  1992).    Observations  have  shown  that  local  chicken  found  within  the  swampy rainforest  and  guinea  savanna  regions  are lighter  in weight  than  those  found  within  the highlands and sudan savanna regions (Nwosu, 1979).  Such differences in body weight can be used to categorize the local chicken broadly as Light Ecotype – those with lighter weight and Heavy Ecotype – those with heavier weight.

Research data on the local chicken in the past 50 years (Hill, 1954; Oluyemi, 1979; Omeje and Nwosu, 1982; Nwosu, 1987; Udeh and Omeje, 2001) indicate that the Nigerian local chicken has useful genetic attributes that can be harnessed in crossbreeding programmes for the development of egg-type and meat-type chickens.  However, there exist limitations to the realization of total heterosis in such crosses with the exotic because – the local chicken is unpedigreed, unselected and unsegregated (Omeje, 1985) hence, unlike the exotics the local chicken cannot be considered a purebred.   Furthermore, crossbreds from purebred parents show heterosis to the extent that their  gene frequencies differ unlike hybrids from similar lines that manifest total heterosis, (Pirchner, 1983).

In order to incorporate  the local  chicken  as a parent  breed  to produce  strains  of chicken that are adaptable to the local environment as well as achieving the much desired goal of making Nigeria self-sufficient in the sourcing of poultry breeding stock and boosting her poultry industry, there is need for selective breeding.  The practice of selective breeding among local strains has been found advantageous (El-Issawi, 1975).  The concept underlying selective breeding is variation.  For within a group of individuals there exist allelic variations that affect the outcomes of quantitative traits such as growth, egg production and egg quality traits.

1.2      STATEMENT OF PROBLEM

Not  much  study  has  been  done  on  selection  of  local  chicken  for  meat  or  egg production;  most of the studies  have been on crossbreeding  with exotic  birds.    Oluyemi

(1979) after seven generations of mass selection on 12-week body weight of the local chicken concluded that the local chicken is not a potential broiler strain.  Although the local chicken has been termed a low producer with regards to egg production (40-80 eggs /bird/year under extensive management system), studies relating to the development of the local chicken as a potential layer have shown appreciable  improvement  in egg  production traits of the birds under improved management system (Hill and Modebe,  1961; Nwosu et al, 1979, Omeje,

1985; Tule, 2005).   Nwosu and Omeje (1985) further noted that the local chicken  has  a genetic potential of producing 128 eggs /bird/year.  It should be noted that the results of these studies  were  from  random-bred  populations.    It  is quite  possible  that  the  local  chicken subjected  to selection  and improved  management  can do better.    This has prompted  the present selection study of the local chicken using a selection index approach.

1.3      OBJECTIVES OF STUDY

The objectives of this study are to:

1.        Estimate  genetic  parameters,  namely  heritability  of body weight  at first  egg,  egg number and egg weight, and genetic and phenotypic correlations between these traits in the Light Local Chicken Ecotype (LLCE);

2.        Develop  an appropriate  selection  index (I) for the selection  of LLCE  using  body weight at first egg, and short-term (90 days from first egg)  egg  production   and  egg weight;

3.        Evaluate  and summarize  selection  applied  and response  over three  generations  of selection.

1.4       JUSTIFICATION

Over  the last  decades,  poultry  management  techniques  in Nigeria  have  improved significantly,  with  rapidly  increasing  production.     However,  due  to  the  high  cost  of production inputs: such as feed and drugs, and the control of the market by the few livestock contract companies, many individuals and farmers could not compete with the companies and had to give up chicken meat/egg production.   For these  individual farmers, a streamlined production  of local chicken could be an option for  alternative  income generation and for diversification of the agricultural production base.

Akinwumi  (1979) reported that 92% of poultry production  in Nigeria was  derived from indigenous  poultry stock.   Similar reports though from Asian survey  carried out by Prawirokusmo (1988) stated that about 40% of the egg production and 30% meat production in Indonesia was a contribution  made by the local type of chicken.   Local chickens  may appear to produce less than highly specialized exotic breeds, but they are highly productive in their use of local resources and more sustainable over the long term.   Products from local poultry stocks are widely preferred because of pigmentation, taste and leanness (Haitook et al, 2003; Horst, 1988).  Local chicken can thrive with limited care and feeding and are often more tolerant or resistant to diseases.  They are also better able to cope with drastic changes in food and water  supplies  as well as harsh,  variable  and extreme  weather  and climatic condition.    By  neglecting  to  develop  locally  adapted  breeds  for  higher  productivity,  an opportunity is being missed to help the developing world feed its people.

Barker (1982) argued that there are large phenotypic and possibly genetic variations existing within the indigenous/local breeds and varieties.  He suggested that the application of genetics towards improving these stocks should be undertaken through proper evaluation and documentation  of these  breeds  on a suitable  selection  procedure  designed  to provide  an optimum genotype to the farmer.  This implies that a breeding strategy, which recognizes the introduction and development of pure breeds and selection within local breeds, is beneficial. Ahmed  and  Hasnath  (1983)  described  the  usefulness  of  such  strategy  in  native  Delish chicken.  Hence, continuous efforts to develop pure lines for meat and egg production locally may equal or excel in the future the best currently available in the country.

No detailed examination of genetic parameter estimates/variance components for egg production traits in Nigerian local chicken have been reported in literature.   Consequently, the little breeding experimental programmes on this bird rely heavily on estimates obtained from exotic populations.  For effective genetic improvement, knowledge of genetic parameter estimates of the particular breed or population to be improved is essential.  Thus this study is imperative to achieving the genetic improvement of the Nigerian light local chicken ecotype.

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