**5. Genetic diversity and distance within and between ecotypes, and genotypes**

Studies to evaluate genetic diversity and distance within and between NICs involved phenotypic and molecular evaluation of different ecotypes, genotypes and populations [19–21]. Ige [100] using correlation and regression models estimated genetic parameters of BW and linear body traits to evaluate genetic distance between Yoruba (YE) (light) and Fulani (FE) (heavy) IC ecotypes. Correlation coefficients ranged from 0.30 to 0.89 and 0.40 to 0.99 in male and female FE, respectively and from 0.20 to 0.88 and 0.15 to 0.85 in female and male YE, respectively. Coefficient of determination (R<sup>2</sup> ) ranged from 0.20 to 0.91, 0.10 to 0.76, and 0.22 to 0.94 for linear, quadratic and cubic functions, respectively in YE and 0.55 to 0.94, 0.64 to 0.81, and 0.55 to 0.86, respectively in FE. The IC ecotypes showed strong discriminatory power (98.29%) but low genetic distance (Euclidean genetic distance = 11.2) indicating close relationship. Using canonical discriminant analysis [19] evaluated the diversity among NIC genotypes and reported highest discriminatory power in Body weight, thigh length, and body width. Mahalanobis distance measure indicated closer relationship between normal feathered and naked neck (3.371) compared to normal feathered and frizzle genotype (4.626). Gwaza et al. [101] however reported wide genetic diversity in body dimensions among isolated populations of Tiv chickens. Ukwu et al. [102] evaluated within ecotype genetic

*Landraces - Traditional Variety and Natural Breed*

reported by [69].

Reported heritability (h<sup>2</sup>

tively. Oluyemi [90] had reported h<sup>2</sup>

while 2–3 locus parental epistasis involving complementary genes were responsible for heterosis observed in exotic backcrosses. Udeh [87] reported significant differences in age at first egg (AFE), BWFE and WFE among native X exotic inbred chicken groups. Inheritance of AFE and WFE was attributed to additive (e.g., sire) and non-additive (e.g., dam) genetic effects while dominance effect was responsible for inheritance of BWFE. Udeh [88] showed that crossing IC with inbred progenies of H and N brown nick, and Black Olympia, improved BW and BWG from hatch to 20 weeks of age relative to IC due to significant direct additive, maternal additive and direct heterotic effects. Significant genotype effect on fertility, and hatchability and improved BW and EW in LE x Isa Brown progenies compared to LE was

local chickens and exotic breeds vary widely being specific for populations, point of estimation, and age of birds. Akinokun and Dettmers [89] reported values of 0.15, 0.02 and 0.25 for age at sexual maturity (ASM), 4 months, and 8 months egg production, respectively; 0.20 to 0.54 for egg weight to 7 months of lay; 0.51, 0.41 and 0.27 for 4, 12, and 20 week body weight, respectively; and realized heritability of 0.27 and 0.24 for 4 months egg production in 2nd and 3rd generation, respec-

[91] reported values of 0.35 to 0.74, 0.31 to 0.89, and 0.27 to 0.49 for body weight from sire, dam, and sire + dam variance components in progenies of crosses involving ICs, Yaffa and Goldlink. The same authors reported heritability of 0.46 ± 0.24

for egg weight and 0.36 ± 0.18 for shell thickness. Udeh [92] reported h2

respectively among BW, SL, and WL at different ages in NICs.

of 0.08 to 0.80, 0.03 to 0.69, and 0.22 to 0.47 for BW, shank length, and wing length, respectively, and positive genetic correlation (except for SL and WL) and phenotypic correlation coefficients that ranged from 0.18 to 0.96 and 0.10 to 0.91,

**4.3 Genetic improvement of Nigerian indigenous chickens through selection**

Relatively few studies that are far in between have been undertaken to evaluate selection response in NICs. The earliest report on genetic selection [80] observed poor selection response in body weight in NICs over 7 generations while [93] reported genetic gain of 2.20 and 2.48 eggs for first and second generations, respectively. Recently, a number of studies demonstrated significant improvement of growth and egg production traits. In light ecotype (LE) IC, [63] reported improvement in BWFE, EN, EW, and WFE but increased AFE following three generations of index selection (G0 to G2). Values reported for selected vs. control groups ranged from 962.50 ± 23.33 to 1062.90 ± 18.06 vs. 880.14 ± 16.72 to 892.10 ± 18.85 for BWFE, 33.40 ± 1.23 to 47.18 ± 2.36 vs. 34.04 ± 1.15 to 37.38 ± 2.21 eggs for EN, 36.51 ± 0.55 to 38.64 ± 0.49 vs. 35.27 ± 0.31 to 35.73 ± 0.59 g for EW, 30.62 ± 0.92 to 31.92 ± 0.63 vs. 29.44 ± 0.37 to 29.99 ± 0.66 g for WFE, and 159.47 ± 1.97 to 164.78 ± 2.40 vs. 158.40 ± 1.13 to 159.48 ± 1.47 d for AFE. From the same population cumulative selection differential (CumΔs) of 269.38 g, 1.58 g, and 3.88 eggs and realized genetic gain per generation of 94.22 g, 0.84 g, and 4.85 eggs, for BWFE, EW, and EN, respectively were reported [94]. Pooled heritability estimates over the three generations was 0.56, 0.44, and 0.28 for BWFE, EN, and EW, respectively while genetic correlation values were 0.41 for BWTE and EW, −0.18 for BWFE and EN, and − 0.23 for EN and EW [95]. Ogbu et al. [96] estimated the economic, and relative economic weights of BW, EW and EN to 16 weeks of lay in heavy ecotype IC (HE) over three generations (G0 to G2) for use in construction of selection indices and reported values of 7.47 and 3.15, 13.67

) estimates of production traits in crosses between

value of 0.31 for 12 week body weight while

values

**150**

diversity at the hemoglobin (Hb) locus in Tiv chickens and observed three Hb genotypes (HbAA, HbAB, and HbBB) at frequencies 0.40, 0.32, and 0.24, respectively resulting from two Hb alleles at frequencies 0.60 for HbA and 0.40 for HbB . Tiv chickens showed moderate Hb heterozygosity of 0.48. Adenaike et al. [20] investigated genetic diversity in NIC genotypes and Nera Black chickens based on variation in *zyxin* and TNFRSF1A genes. Highest nucleotide substitution per site (Dxy = 0.081) was reported for TNFRSF1A gene sequences in normal feathered and naked neck chickens while frizzle and Nera Black chickens had the lowest value of Dxy = 0.065. For *zyxin* gene sequences, normal and frizzle feathered chickens had highest Dxy value of 0.6551 vs. 0.0739 for Nera Black and naked neck. Mean haplotype diversity and average number of nucleotide difference in TNFRSF1A gene sequences was highest in Nera Black (0.923 and 3.967, respectively) while frizzle chickens had the corresponding lowest values (0.00489 and 3.143, respectively). The authors inferred high nucleotide divergence, haplotype diversity and restricted gene flow among the chicken genotypes. Gambo et al. [21] studied diversity and genetic distance within and between Tiv (TE) and Fulani (FE) ecotypes based on blood proteins (Hb, albumin, transferrin and carbonic anhydrase) electrophoresis. Two Hb genotypes (HbAA and HbAB at frequencies 0.125 and 0.875, respectively in TE, and 0.538 and 0.462, respectively in FE), three albumin genotypes (AB, and AC at frequencies 0.026 and 0.974, respectively in TE, and AA and AC at frequencies 0.077 and 0.923, respectively in FE), six transferrin genotypes (AA, AB, AD, BB, BD, and DD at frequencies 0.054, 0.027, 0.297, 0.162, 0.378, and 0.082, respectively in TE and AA, AD, and DD at frequencies 0.568, 0.243, and 0.189, respectively in FE), and four carbonic anhydrase genotypes (AA, AB, AC, and BB at frequencies 0.20, 0.175, 0.525, and 0.100, respectively in TE and AA, AB, and AC at frequencies 0.263, 0.026, and 0.711, respectively in FE) were reported. Thus HbAA and HbAB were most abundant in TE and FE (0.875 and 0.538, respectively). Genotype AC for albumin, BD and AA for transferin and AC for carbonic anhydrase were the most frequent in the two ecotypes while albumin genotypes AA and AB were absent in TE and FE, respectively. The authors inferred a common origin for the two ecotypes but positive genetic distance between them attributable to divergence from one locality to another. Ige and Salako [103] employed direct gene counting and dendogram following cellulose acetate electrophoresis to evaluate genetic variation at the transferrin locus and established genetic relationships within and between FE and YE chickens. The authors reported six phenotypes (AA, AB, AC, BB, BC, and CC at genotypic frequencies 12.5, 10.0, 7.5, 35.0, 17.5, and 15.0%, respectively in YE, and 11.19, 16.6, 2.8, 22.2, and 27.7%, respectively in FE) controlled by three co-dominant alleles (TfA, TfB , and TfC at frequencies 0.35, 0.20, and 0.43, respectively in YE and 0.21, 0.32, and 0.44, respectively in FE). Dendogram clustering analysis indicated 72% genetic similarity within FE, 58% within YE, 70% between the two ecotypes, and no genetic relationship between transferrin locus and phenotypic traits such as sex, plumage color, and comb type of chicken. Ige et al. [22] considered the variation at globulin (95SKDa), transferrin (66KDa), albumin (36KDa), and post albumin (29KDa) loci using sodiumdodecylsulphate polyacrylamide gel electrophoresis to evaluate the genetic similarity of YE ICs. Similarity indices for transferrin, albumin, globulin, and post albumin were 58, 19, 18, and 40%, respectively indicating genetic similarity at the transferrin locus but wide variation at the other blood protein loci. The authors also inferred that the YE IC populations were still under natural selection. Adeleke et al. [104] had reported mean genetic similarity index of 55% between normal feathered, frizzle feathered and naked neck IC genotypes using blood protein polymorphisms and inferred clearly separated genotypes with naked neck genotype being the most diverged.

**153**

*Utilization and Conservation of Landrace Chickens of Nigeria: Physical and Performance…*

conserve the potential to react to future challenges [105–107].

**6. Conservation of Nigerian indigenous chicken genetic resources: issues** 

Nigerian ICs have evolved as homeostatic populations with adaptive and neutral diversity and capacity to respond to changing environmental conditions in diverse ways [6, 7, 16]. Experts believe that diverse unselected indigenous animal resources that harbor high proportions of neutral and adaptive diversity represent equivalent genetic resources in the absence of wild ancestors, and should be conserved with high national priority [105]. Emerging diseases, climate change, and changes in nutritional needs of humanity are unforeseeable. Consequently, overall genetic resources defined by adaptive and neutral diversity must be maintained in order to

There is dearth of data on the extinction risk status of NICs but commentators agree that IC genetic resources are the most endangered and under conserved animal genetic resources [6, 108, 109] with extinction risk of 33% [110] and about 40% of breeds with unknown extinction risk status [111]. Studies have shown the dwindling frequency or apparent loss of rare NIC phenotypes such as the crested head, feathered shank or ptylopody, polydactyl or 5 toed, short flight feathered, and dwarf types, naked neck, frizzle, and silky, and major genes such as naked neck (Na), frizzle (F), dwarf (Dw), ptylopody (Fsh), and polydactyl (Po) believed to

enhance survival and performance in tropical environments [6, 16, 112].

**6.1 Drivers of erosion and loss of indigenous chicken genetic resources**

a.Pressure to substitute indigenous types with exotic breeds

b.Introgression of exotic genes into native animal genetic base

genetic resources [23, 24].

The declining animal genetic resources in developing countries has been blamed on a number of factors defined by scholars to threaten production, utilization, and conservation of native animal populations including ICs [24, 113, 114]. A brief overview of these factors will provide the background for suggested mitigation strategies.

The notion within professionals, and policy makers that husbandry of landrace chickens is an economic waste put pressure on farmers to cull local strains in favor of exotic breeds [23] leading to loss, sometimes irretrievably, rare IC

To meet growing animal food demands due to increasing human population and rise in income, policy makers, researchers, and farmers advocate crossbreeding of local strains and exotic breeds without long-term breeding objectives [23, 98, 115]. These activities dilute and narrow indigenous animal genetic base and lead to loss of important traits for survival and production in scavenging husbandry system and harsh (disease endemic and high temperature) environments [23, 24, 115, 116]. Reduced fitness of resulting hybrids have been reported in chickens and other species [24, 117], and no commercial breed has resulted from decades of crossbreeding involving NICs and exotic breeds [98]. Similar scenario has been reported in other African countries [23, 24, 115, 118, 119].

c.Radical shift in production system and poor economic valuation of ICs

The shift from small scale, subsistence production to large scale, intensive holdings alienates indigenous strains [24, 120, 121], resulting in loss of IC

*DOI: http://dx.doi.org/10.5772/intechopen.96580*

**and concerns**

*Utilization and Conservation of Landrace Chickens of Nigeria: Physical and Performance… DOI: http://dx.doi.org/10.5772/intechopen.96580*
