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 chickenecotype (NHLCE) through selection for body weight and egg production traits. Progenies (G0generation) generated from breeding parents randomly selected from the parent stock of theNHLCE formed the materials for the research. On hatching, the chicks were grouped accordingto 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 2800Kcal/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 layingcages for short-term (16 weeks) egg production. From then the birds were fed layers mashcontaining 16.5% crude protein and 2600Kcal/kgME. Data were collected on body weight, eggweight and egg number. A control population was maintained for each generation and was usedto measure environmental effects. At the end of the 16 weeks egg production period, hens weresubjected 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 traitsand their heritabilities were used to weight the phenotypic values of each trait in the index. Theindex score of each bird became a univariate character, which enabled the hens to be ranked forpurposes of selection. Males were selected based on their individual body weight performancesat 39 weeks of age using mass selection. Selected parents from G0 generation were used togenerate the G1 generation which in turn yielded the parents of the G2 generation. Data on bodyweight, BWFE, egg weight and egg number were subjected to statistical analysis to obtainmeans, 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 geneticheritabilities of the traits were calculated. Genetic, phenotypic and environmental correlationsbetween 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 weightperformances (sexes combined) increased across the age periods (0 – 20 weeks) from the startingmean values in G0 generation to the final values in G2 generation. The body weight at hatchincreased from a mean of 30.30g in G0 generation to 33.48g in G2 generation. Body weights at4th, 8th, 12th, 16th and 20th week of age also showed similar increases. Body weight of males andfemales were similarly significantly improved. Mean body weight of males at 12, 16, 20 and 39weeks 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 and2000.00 ± 31.34g, respectively for G2 generation. For females, body weights at 12, 16 and 20weeks 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 increasedfrom 75.60 eggs and 41.27g, respectively in G0 generation to 79.38 eggs and 43.18g, respectivelyin G2 generation. Selection differential values were positive and high for 39 weeks body weightin 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 theaverage 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….