Genetic Change In The Nigerian Heavy Local Chicken Ecotype Through Selection For Body Weight And Egg Production Traits

GENETIC CHANGE IN THE NIGERIAN HEAVY LOCAL CHICKEN ECOTYPE THROUGH SELECTION FOR BODY WEIGHT AND EGG PRODUCTION TRAITS

ABSTRACT
The study was carried out to determine the genetic change in the Nigerian heavy local chicken
ecotype (NHLCE) through selection for body weight and egg production traits. Progenies (G0
generation) generated from breeding parents randomly selected from the parent stock of the
NHLCE formed the materials for the research. On hatching, the chicks were grouped according
to sire families using colour markers. The chicks were brooded and reared according to standard
management practices.

They were fed a starter mash containing 18% crude protein and 2800
Kcal/kgME from 0 – 8 weeks and a growers mash containing 15% crude protein and 2670 Kcal/
kgME from 8 weeks to 20 weeks. At 20 weeks, all pullets were moved into individual laying
cages for short-term (16 weeks) egg production. From then the birds were fed layers mash
containing 16.5% crude protein and 2600Kcal/kgME. Data were collected on body weight, egg
weight and egg number. A control population was maintained for each generation and was used
to measure environmental effects. At the end of the 16 weeks egg production period, hens were
subjected to selection using a multiple trait selection index incorporating body weight at first egg
(BWFE), average egg weight and total egg number. The relative economic weights of the traits
and their heritabilities were used to weight the phenotypic values of each trait in the index. The
index score of each bird became a univariate character, which enabled the hens to be ranked for
purposes of selection. Males were selected based on their individual body weight performances
at 39 weeks of age using mass selection. Selected parents from G0 generation were used to
generate the G1 generation which in turn yielded the parents of the G2 generation. Data on body
weight, BWFE, egg weight and egg number were subjected to statistical analysis to obtain
means, standard error of means and standard deviation using the SPSS 2001 statistical package.
Analysis of variance yielded sire component of variance from which the additive genetic
heritabilities of the traits were calculated. Genetic, phenotypic and environmental correlations
between pairs of traits in the index were estimated. Indicators of selection response, namely,
selection differential, expected, predicted and realized genetic gains were determined for each
trait.

There were significant increases (P £ 0.05) in all the traits selected. Body weight
performances (sexes combined) increased across the age periods (0 – 20 weeks) from the starting
mean values in G0 generation to the final values in G2 generation. The body weight at hatch
increased from a mean of 30.30g in G0 generation to 33.48g in G2 generation. Body weights at
4th, 8th, 12th, 16th and 20th week of age also showed similar increases. Body weight of males and
females were similarly significantly improved. Mean body weight of males at 12, 16, 20 and 39
weeks of age were 791.40 ± 8.79g, 932.25 ± 7.83g, 1112.60 ± 11.98g and 1693.75 ± 19.91g,
respectively for G0 generation as against 825.28±7.54g, 1027.83 ± 9.90g, 1156.69 ± 11.74g and
2000.00 ± 31.34g, respectively for G2 generation. For females, body weights at 12, 16 and 20
weeks as well as BWFE were 667.98 ± 6.30g, 791.52 ± 6.24g, 911.59 ± 6.33g and 1330.44 ±
2.141g, respectively in G0 generation. The corresponding values for G2 generation were 673.94 ±
6.48g, 812.54 ± 7.72g, 939.64 ± 7.28g and 1428.48 ± 3.051g, respectively. For egg production,
significant improvements were also made. Total egg number and average egg weight increased
from 75.60 eggs and 41.27g, respectively in G0 generation to 79.38 eggs and 43.18g, respectively
in G2 generation. Selection differential values were positive and high for 39 weeks body weight
in males across the three generations (mean, 302.19g) as well as for total egg number (mean,
10.74eggs) and average egg weight (mean, 0.47g) in females. It was, however, negative on the
average for BWFE (-5.41g). Selection intensity values for mass selection in males were 2.11,
1.75 and 1.16 for G0, G1 and G2 generations, respectively. Mean selection intensity value….

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