Qualitative mutant genes within the local chicken population in Ghana: their influence on growth performance and egg production

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A cross sectional survey was carried out to find out the qualitative mutant traits within the indigenous chicken population and their influence on egg and growth performance in the three ecological zones of Ghana. Four hundred and five (405) households were randomly selected across the Guinea Savannah, Semi-deciduous Rain Forest and Coastal Savannah. Structured questionnaires and on-site interviews were used to obtain information from the local chicken keepers. The individual birds were phenotypically observed for the presence of the following phenotypes; frizzle (F), naked neck (Na), silkiness (h), polydactyl (Po), ptilopody (Pti), crest feathered (Cr) and flightless (Fl). Data on flightless chicken were not available except their gene frequencies since the respondents do not keep them for economic purposes. The frequency of the genes responsible for mutant traits were obtained from a count of the proportion of recessive in the population using the Hardy-Weinberg equation. The calculated gene frequencies for the mutant traits were low with naked neck (0.04), frizzle (0.04), crest (0.05), silky (0.02), polydactyl (0.01), ptilopody (0.01) and flightless (0.01) which differed significantly (P<0.05) from the expected Mendelian values of 0.75 making these phenotypes prone to extinction. Average clutch size per year, number of eggs set for natural incubation and number of chicks hatched were not significantly different (p>0.05) between the three ecological zones. The percentage hatchability for Guinea Savannah and Coastal Savannah were relatively higher (p<0.05) compared to Semi-deciduous Rain Forest. Polydactyl phenotypes had better (p<0.05) average eggs per clutch per bird, number of eggs set for natural incubation and number of chicks hatched compared with their normal counterparts. Results obtained from mutant traits and zone interaction indicate that, silky and polydactyl birds had superior (p<0.05) performance in percentage hatchability within Guinea Savannah and Coastal Savannah than Semi-deciduous Rain Forest. Again, body weight and linear body measurements of the individual birds were measured using weighing scale (kg) and tape measure (cm) respectively. The average body weight for both cocks and hens in Semi-deciduous Rain Forest were significantly higher (p<0.05) compared to those in Guinea Savannah and Coastal Savannah zones. The average body length and toe length for adult male chickens were 46.82cm and 5.61cm respectively for Semi-deciduous Rain Forest which were significantly (p<0.05) longer than those of Guinea Savannah and Coastal Savannah birds. Polydactyl and ptilopody cocks recorded a longer shank length (p<0.05) compared to their recessive counterparts. Again, ptilopody cocks were superior (p<0.05) to all the mutant traits in terms of body weight, shank length, body length, wing length, keel length and toe length except body girth which recorded shorter length (p>0.05) as compared to their respective counterparts. The correlation coefficients for polydactyl and ptilopody male phenotypes between live body weight and keel length, wing length were positive and significant (p<0.05). The highest and positive (p<0.01) correlation were recorded between live body weight and body girth (0.978) as well as live body weight and body length (0.905) in polydactyl male phenotypes. There were positive and highly significant differences (p<0.01) between live body weight and other traits measured (shank length, body length, wing length, body girth, keel length and toe length) in naked neck phenotypes. The correlation between body weight and body length (0.813) in male silky phenotypes were positive (p<0.01). Correlation analysis indicated that, live body weight could best be determined by shank length, body length, body girth and keel length. The results obtained from the study showed that, naked neck, frizzle, silky, crest, ptilopody, polydactyl and flightless mutant traits were present within the local chicken population. The gene frequency for these mutant traits were very low but they had unique potential in egg laying. Therefore the live body weight and other linear body parts can be improved by enhancing village chicken management systems.
A thesis submitted to The School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of Master of Philosophy Degree in Animal Breeding and Genetics.