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

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

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**

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.

a.Pressure to substitute indigenous types with exotic breeds

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 genetic resources [23, 24].

b.Introgression of exotic genes into native animal genetic base

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

*Landraces - Traditional Variety and Natural Breed*

FE) controlled by three co-dominant alleles (TfA, TfB

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

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

.

, and TfC at frequencies 0.35,

**152**

diverged.

genetic resources [111]. Following the adoption of backyard or family poultry that employs exotic breeds, the family local chicken was substantially eliminated [121]. In addition, native chickens have attracted poor economic appeal because only direct use commercial products (without adaptive potentials) have been used in economic assessment of chicken genetic resources [23, 24].
