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The effect of three different feather genotypes on the laying performance of two lines of layer parents

D Addison, O S Olympio1, K Adomako1, G Aryee2 and J A Hamidu1

Department of Animal production and health, School of Agriculture and Technology, University of Energy and Natural Resources, Sunyani, Ghana
1 Department of Animal Science, Faculty of Agriculture, College of Agriculture and Natural Resources, KNUST, Kumasi, Ghana
2 Council for Scientific and Industrial Research, Animal Research Institute, Accra, Ghana


The experiment was conducted to assess the effects of the naked neck (Nanaff), frizzle (nanaFf) and normal feathered ( nanaff) genotypes, and also gold (s-) and silver (S-) plumage colours on the performance of local-exotic crossbred pullets. Three hundred and sixty pullets of 24 weeks of age were studied in a 3X2 factorial experiment for 40 weeks. There were 120 pullets within each of the three genotypic groups(Nanaff, nanaFf and nanaff); there were two plumage colours (s- and S-) in each genotypic group with three replications in each plumage colour. There were 18 pens with 20 pullets in each pen. Nanaff pullets had higher values (p<0.05) in hen-day egg production, feed intake,age at 50% production, body weight and hen-house egg production than their nanaFf and nanaff counterparts, but the nanaFf pullets were superior (p<0.05) to the nanaff in terms of age at 50% production. Egg mass was not different (p>0.05) between genotypes, except Nanaff vs nanaff. No difference (p>0.05) were recorded among the genotypes in terms of FCR and egg weight. The S- pullets performed better (p<0.05) in hen-day egg production, egg mass, hen-housed egg production and age at 50% production than their s-counterparts whilst no difference (p>0.05) were recorded between the two plumage colour genotypes in terms of egg weight, feed intake and body weight. The naked neck genotype and silver plumage colour improve egg laying performance in layer parents.

Key words: crossbred, naked neck, plumage colour, pullets


The harmful effects of high temperature on the performance of laying hens have been well studied. Under warm conditions, birds do not reach their full genetic potentials for growth, body weight and egg production because dissipation of their excessively produced internal heat is hindered by the feathers (Cahaner et al 2008). Feed intake, egg production, egg weight and shell quality are decreased in heat-stressed birds (Merat, 1986). Balnave (1996) reported that high environmental temperatures are the most important inhibiting factors to poultry production in hot regions.There is therefore an urgent need for producing birds that can adapt to hot environment. Galal and Fathi (2007) advocated the use of heat- tolerant genes like naked-neck (Na) and frizzle (F). Gowe and Fairfull (1995) stated that the naked neck gene improves heat tolerance as indicated by higher egg production, better feed efficiency, early sexual maturity, larger eggs with possibly fewer cracks and fewer mortality when compared to the normally feathered with similar genetic background.The main objective of this work was todetermine the effects of three genotypes Nanaff, nanaFf and nanaff as well as the plumage genotypes s and S colours on egg production performance of two lines of improved local layer breeder parents.

Materials and methods

The experiment was conducted from 9th February, 2012 to 30 thNovember, 2012 at Akate Farms and Trading Company Limited in the Ashanti Region of Ghana.

Three hundred and sixty, 24 week-old pullets made up of 120 heterozygous naked neck (Nanaff), 120 heterozygous frizzles (nanaFf) and 120 normally feathered (nanaff) birds were housed in a deep-litter pen partitioned into 18 compartments with 20 pullets per compartment. The birds were fed layer breeder mash containing 17.43% crude protein and 2,700 kcal/kg metabolizable energy from the 24th week of age to the end of the experiment (64th week). Feed and water were supplied ad libitum. A minimum and maximum thermometer was used to measure daily temperature of the experimental unit. The ambient temperature values were read at 3:00pm daily. Data on daily egg production were kept throughout the laying period on replicate basis. This was summed up every week and expressed as weekly hen-day egg production. Mean egg weight was obtained by weighing samples of eggs from each of the genotypic groups. The eggs were weighed from 24 weeks - of - age and every week thereafter. The feed conversion was calculated as the amount of feed consumed (kg) to produce a dozen of eggs. Hen-housed egg production was measured by calculating the number of eggs produced divided by the number of birds housed.

Rectal temperature was measure monthly with the use a multi-purpose thermometer. The experiment was a 3X2 factorial (3 genotypes – Nanaff, nanaFf, and nanaff and two lines – silver and gold birds) arranged in completely randomized design.

Data were analyzed using the MIXED procedure of SAS (SAS Institute, 2002-2003) at p≤ 0.05, where significant differences were observed, the least squares means were separated by the pdiff procedure of SAS (SAS Institute, 2002-2003).


Table1 shows the effects of genotype and plumage colour on hen-day egg production, egg mass, egg weight and feed intake. The Nanaff pullets had significantly higher (p<0.05) hen-day egg production and feed intake values than their nanaFf and nanaff counterparts. In terms of egg mass, the Nanaff pullets were significantly better (p<0.05) than the nanaff pullets but the difference between Nanaff and nanaFf was not statistically different (p>0.05). No significant difference was recorded among the genotypes in terms of egg weight.Hen-day egg production and egg mass were significantly better (p>0.05) in S- birds than their s- counterparts (Table 1).

Table 1. Effects of genotype and feather colour treatments on egg production traits in chickens


Feather colour

Nanaff (a)1

nanaFf (Ff)2

nanaff (na)3

















EM (g)






























a-b Indicates significant difference between mean within the same column at 5% significant level. 1 Naked neck birds, 2Frizzle birds; 3Normally feathered birds; 4 Standard error mean; 5White birds; 6Gold birds, HDEP= Hen day egg production, EM= egg mass, EW= Egg Weight, FI=Feed intake

The Nanaff pullets had significantly higher values (p<0.05) for hen-day egg production and feed intake than the nanaFf andnanaff counterparts (Table 1). In terms of egg mass theNanaff pullets were significantly better (p<0.05) than the nanaff pullets but were not significantly different (p>0.05) from the nanaFf birds. No significant differences were recorded among the genotypes in terms of egg weight. Hen-day egg production and egg mass were significantly better (p<0.05) in S- birds than their s- counterparts (Table 1).

The Nanaff genotypes had significantly higher (p<0.05) average hen-housed egg production compared to the frizzle and normally feathered birds(Table 2). With regard to rectal temperature, the nanaff birds had higher (p<0.05) values than the mutant genotypes.

The Nanaff pullets maintained their significantly superior (p<0.05) values in terms of body weight and age at 50% production compared to the nanaFf and nanaff pullets. However, the nanaFf birds were superior (p<0.05) to the nanaff birds in terms of age at 50% production. FCR was not different in all the genotypes.

The S- pullets produced more eggs (p<0.05) in terms of hen-housed egg production and reached the age at 50% production earlier than their s- groups while no significant difference was recorded with respect to FCR, rectal temperature and body weight (Table 2).

Table 2. Effects of genotype and feather colour treatments on egg production in chickens


Feather colour




















HHEP (%)










RT (oC)










BW (kg)




















a-c Indicates significant difference between mean within the same column at 5% significant level.1 Naked neck birds, 2Frizzle birds, 3Normally feathered birds, 4 Standard error mean; 5White birds, 6Gold birds. FCR= Feed conversion ratio, HHEP= Hen housed egg production, RT= Rectal temperature, BW= Body weight, AP= Age at 50% production


The better (p<0.05) performance in hen-day egg production of the Nanaff birds over the nanaFf and nanaff birds confirms the observation that under constant heat stress the heterozygous naked – neck (Nana) layers have significantly higher egg numbers, egg weight, egg mass, body weight and productivity index than the normal feathered (Mathur 2003).

Similarly, Bordas and Merat (1990) and Younis and Cahaner (1999) reported that at high ambient temperature, the heterozygous frizzle hens had a deterioration in egg productivity and quality comparable to that of normally feathered birds, suggesting that the frizzle gene in the heterozygous form may not be as well adapted to heat stress as the naked neck. One reason could be that unlike the naked neck, the overall feather mass of heterozygous frizzle birds is not significantly reduced when compared to the normally feathered ones. Cahaner et al (1993) indicated that the reduction of feather coverage provides relative heat tolerance and therefore, at high ambient temperature, heterozygous naked – neck chickens are superior to their normally feathered counterparts.

The naked neck pullets superiority in terms of egg mass, confirm the observations of Graces et al (2001) and Younis and Galal (2006) who found that the naked neck gene has been associated with increased laying rate, egg size and egg mass in hot environments. This might be due to the ability of the naked neck genotypes to perform creditably in terms of higher egg numbers and bigger egg weight as observed by Mathur (2003) and Haaren- Kiso et al (1991). Though the birds with the heat-tolerant genes were expected to have laid significantly bigger eggs than their normally feathered ones, the results showed otherwise. This might be due to the fact that the ambient temperature recorded (250C - 320C) was not stressful enough to elicit a significant difference in egg weight. The significantly higher (p<0.05) feed consumption of the naked neck genotypes than their counterparts supports the observation made by Galal and Fathi (2001) that birds with naked neck gene had higher feed intake compared to those normally feathered. However, feed conversion ratio was not significantly influenced byboth the genotypes, though previous findings by Abdel- Rahman (2000) showed that naked neck birds had a significantly better (p<0.05) feed conversion than the normally feathered genotypes. The higher (p<0.05) performance of the Nanaff genotypes than the nanaFf and nanaff genotypes (Table 2) in terms of hen housed egg production is in line with the findings of Hagan et al,(2010), Merat (1986) and Haaren- Kiso et al (1991) that the naked neck genotypes were superior in egg production under hot humid environment (temperature above 300C).

The nanaff pullets showing significantly higher (p<0.05) rectal temperature can be explained from the findings of Bordas et al (1978) that in terms of dominance, the homozygous (nana) birds tend to have full plumage cover as compared to their heterozygote (Nana) counterparts (41 and 27%) and (33 and 22%) for males and females respectively. This full plumage cover as well as internally generated heat might have warmed the normally feathered (nana) birds because the birds have poor dissipation of heat (Cahaner et al 2008).

The significantly bigger (p<0.05) body weight recorded by the Nanaff compared to the other two genotypes agrees with the findings of Yoshimura et al (1997) that among the indigenous chickens, the naked – neck was found to be superior in terms of egg production, egg size and body weight in a hot and humid environment. This can be ascribed to their ability to conserve protein for body development, which could have been used for feather growth (Adedeji et al 2006). The earlier (p<0.05) age at 50% production of the Nanaff groups followed by the nanaFf genotypes (Table 2) compared to the nanaff counterparts supports the findings of Njenga (2005) that the naked – neck birds reached sexual maturity (p < 0.05) earlier than the normally feathered birds by about 5 days.

The better (p<0.05) hen-day egg production, egg mass, hen-housed egg production and earlier age at 50% production in S- birds than their s- groups may be attributed to the ability of the S- birds to reflect sun beans with their white colour confirming the findings of Bright (2007) that white feathers reflect at a higher intensity than black or grey feathers. According to that author, white hens had less feather damage from feather pecking than birds with other plumage colours. These might have assisted the S- birds to perform significantly better than their s- counterparts sinceability to reflect at a higher intensity aids in avoidance of heat stress and less feather damage would permit the use of protein for other development instead of feather growth (Adedeji et al 2006).



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