**4.2 Crossbreeding of Nigerian indigenous chicken ecotypes, and genotypes with exotic breeds**

Crossbreeding NICs with exotic breeds/strains is advocated to exploit the high genetic distance and variation between ICs and exotic strains believed to enhance hybrid vigor, heterosis, and breed complementarity. Omeje and Nwosu [58] evaluated progenies of crosses between NIC (LC) and Gold link (GL, an exotic breed) and reported reduced age at first egg (AFE) in LC x GL progenies compared to LC, GL, and GL x LC (155.4 ± 1.49 vs. 157.8 ± 3.21, 169.2 ± 1.65, and 169.7 ± 3.74 d, respectively). Authors also reported superior egg weight for GL, GL x LC, and LC x GL compared to LC (53.44, 47.74, and 47.02 vs. 38.63 g, respectively). The corresponding values for egg mass was 12.12, 10.18, and 8.89 vs. 5.64 kg, respectively. An improvement in annual egg production from 146 eggs/hen for LC to 213 eggs/ hen for GL x LC was reported by [77]. Fewer but longer pauses and shorter but more pauses were observed in LC and LC x GL; and GL and GL x LC, respectively. It was also observed that hybrids of crosses involving LC, Yaffa (Y) and GL exotic chickens [LC(Y x GL), GL (Y x LC), and Y x GL] were superior to LC in egg weight (51.91, 52.07, and 54.22 vs. 40.36 g, respectively), and egg mass (5.40, 5.37, and 6.10 vs. 3.32 kg, respectively) [78] while [79] reported superior body weights for GL, GL x LC, and [GL(GL x LC)] in growth and egg production compared to LC attributed to dominance, epistasis, and/or maternal effects. Oluyemi [80] reported heterosis of 12 week body weight in progenies of LC x White Rock and LC x Rhode Island Red (RIR) to range from 4.0 to 12.4% while significant improvement in BWFE, WFE, ASM, egg production (EN90) and egg weight (EW90) to 90 d was observed in LC x RIR males backcrossed to RIR dams [81]. Ukpong [82] observed improved meat yield in crosses of LC x Abor acre (AA) broiler chickens relative to LC while [49] reported improved growth performance and feed conversion in F2 (main and reciprocal backcross groups) compared to F1 counterparts in crosses of Abor Acre broiler breeder and native chicken genotypes (**Table 2**). Nwachukwu et al. [18] had shown that main crossbred progenies of AA x LC genotypes were inferior in body weight at first egg to their reciprocal crossbred counterparts (960.00, 812.50 and 1030.00 vs. 1891.67, 1576.50 and 2072.00 g, respectively). The latter group also had higher values for WFE, EN90, egg length, yolk index, albumen weight, and Haugh unit and crosses involving the frizzle genotype were superior to crosses involving other IC genotypes. Adeleke et al. [83] crossed complete feathered, frizzle and naked neck ICs to Anak titan (AT) broilers and reported significant effect of sire, dam, and progeny genotype on growth traits. Anak titan sire significantly improved 8 to 20 week body weight compared to IC sires. Significant sire genotype effect on fertility and percent dead in shell was also reported in IC genotypes crossed to AT [84]. Frizzled sire had highest fertility (90.5%) and produced eggs with highest hatchability (91.4%) and least embryo mortality (7.5%) while AT dams produced eggs with highest fertility and hatchability (88.2 and 94.6%, respectively). Main and reciprocal crosses involving the frizzle genotype were also better in the traits studied [84]. Ayorinde et al. [85] observed superior body weight in Fulani ecotype X Dominant black (FE x DB) progenies compared to FE, DB, and DB x FE at 21 weeks of age (1408.50 ± 3.5 vs. 1350.60 ± 4.5, 1388.60 ± 3.2, and 1375.00 ± 3.2 g, respectively). All crossbred genotypes were superior in early (0 to 13 weeks) body weight to FE. Udeh and Omeje [86] reported heterosis of body weight in native and exotic inbred chicken crosses with native X exotic being higher than exotic X native, and native backcrosses being higher than exotic backcrosses. The authors concluded that body weight heterosis resulted from complete dominance in native backcrosses

*Landraces - Traditional Variety and Natural Breed*

**chickens**

selection within ecotypes.

**and genotypes**

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

number, pause number, and pause length), h<sup>2</sup>

HE, LE, HE x LE, and LE x HE populations and reported h<sup>2</sup>

**4. Genetic improvement of productivity of Nigerian indigenous** 

**4.1 Crossbreeding between Nigerian indigenous chicken ecotypes,** 

Genetic improvement of NICs in growth traits, egg production, fertility and hatchability has been the objective of numerous studies. These studies involve crossbreeding between ecotypes, and genotypes; ICs with exotic breeds/strains; and

The extensive genetic diversity between IC ecotypes as well as within and between population variations in productive traits provide opportunity for improvement of performance through within and between population selective breeding. Ogbu and Omeje [26] reported high within population variation in growth traits in NICs which could be exploited for genetic improvement while [73] recorded improved growth performance following positive assortative mating in NIC populations. Egahi et al. [48] evaluated the effect of crossbreeding between NIC genotypes and reported the body weight of progenies of crosses between normal feathered, frizzle, and naked neck ICs to range from 25.48 ± 0.40 to 28.95 ± 0.45 g for hatch weight, 80.91 ± 0.87 to 91.87 ± 0.78 g, 257.16 ± 3.01 to 283.50 ± 2.41 g, 500.53 ± 7.11 to 639.49 ± 7.94 g, 734.41 ± 7.38 to 842.29 ± 5.88 g, and 1017.63 ± 10.79 to 1121.78 ± 9.94 g, for 4, 8, 12, 16, and 20 weeks of age, respectively (**Table 2**) while [67] observed significant effect of sire, dam, and ecotype on AFE and BWFE of Fulani and Tiv ICs and positive genetic correlations between AFE, BWFE, and EW; and EW, egg length (EL), and egg diameter (ED). Additive

were 0.358 and 0.438, 0.420 and 0.398, 0.482 and 0.642, 0.182 and 0.000, and 0.051 and 0.309, respectively. For egg production pattern (clutch size, clutch

0.036, respectively in Fulani chickens and 0.428, 0.391, 0.063, and 0.048, respectively in Tiv chickens [74]. High positive genetic correlations (range: 0.78 to 0.88) were reported between BWFE and AFE, BWFE and EW, EW and EL, and EW and ED. Agu et al. [75] reported significant effect of sire on AFE, weight of first egg (WFE), egg production (EN), egg mass (EM), egg weight (EW), thigh length, back width, and neck length in HE ICs of Southeastern Nigeria. Heritability values for EW, EN, and EM was 0.31 ± 0.30, 0.16 ± 0.13, and 0.28 ± 0.24, respectively and ranged from 0.13 ± 0.23 to 0.52 ± 0.24 from 4 to 20 weeks of age for thigh length, 0.23 ± 0.23 to 0.41 ± 0.29 for back width, and 0.10 ± 0.18 to 0.52 ± 0.44 for neck length. Momoh et al. [46] showed that main (HE x LE) and reciprocal (LE x HE) crossbred progenies were similar in body weight to the HE chickens but superior to the LE chickens. Momoh and Nwosu [76] evaluated the genetic parameters of body weight (BW), body weight gain (BWG), and feed conversion ratio (FCR) in

0.08 ± 0.10, and 0.19 ± 0.22 for BW at hatch, respectively. The corresponding values for BW from week 4 to week 20 of age ranged from 0.16 ± 0.18 to 0.43 ± 0.26, 0.16 ± 0.13 to 0.25 ± 0.17, and 0.20 ± 0.21 to 0.36 ± 0.28, respectively. For daily gain from 4 to 20 weeks, 0.03 ± 0.11 to 0.12 ± 0.14, 0.21 ± 0.15 to 0.89 ± 0.50, and 0.10 ± 0.16 to 0.80 ± 0.14, respectively were reported while 0.13 ± 0.16 to 0.41 ± 0.25, 0.10 ± 0.10 to 0.46 ± 0.24, and 0.11 ± 0.16 to 0.24 ± 0.23, respectively

) of AFE, BWFE, EW, EL, and ED for Fulani and Tiv ICs

values were 0.358, 0.412, 0.045, and

values of 0.17 ± 0.19,

**148**

were reported for FCR.

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 reported by [69].

Reported heritability (h<sup>2</sup> ) estimates of production traits in crosses between 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, respectively. Oluyemi [90] had reported h<sup>2</sup> value of 0.31 for 12 week body weight while [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 values 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, respectively among BW, SL, and WL at different ages in NICs.

#### **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

**151**

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

and 5.77, and − 2.37 and − 1.00, respectively in G0,; 13.07 and 3.82, 23.69 and 6.93, and − 3.42 and − 1.00, respectively in G1; and 16.80 and 2.89, 30.75 and 5.28, and − 5.82 and − 1.00, respectively in G2 generation. Using an index of weighted breeding values that considered the heritability, relative economic weight, and standardized trait values, [97] reported expected average direct genetic gain per generation for short term (16 weeks) egg production of 12.58 eggs, 1.98 g, and 25.04 g for EN, EW, and BWFE, respectively; realized genetic gain of 2.19 and 1.59 eggs for EN, 1.65 and 0.26 g for EW, and − 25.60 and 123.64 g for BWFE for G0 and G1, respectively; and corresponding values for ratio of realized to expected genetic gain of 2.27 and 1.22, 3.15 and 0.24, and 0.95 and 2.21, respectively. The

EW and 0.57 to 0.69 for BWFE. For males, improvement in 39 week body weight was observed with realized genetic gain of 284.22 and 111.87 g for G0 and G1, respectively and average expected gain of 508.50 g per generation following mass selection. Ogbu [98] had reported improvement in BW from hatch to 39 weeks following mass selection in male HE IC with final body weight increased from 1372.66 ± 16.46 g in G0 to 1768.75 ± 33.15 g in G2 implying a cumulative gain of

0.59 ± 0.45 and 0.13 ± 0.49 to 0.25 ± 0.31 across the three generations for BW from 12 to 20 and 39 weeks of age, respectively. Agbo [99] furthered the selection for improved growth and egg production in HE ICs from 4th to 6th generation and reported improvement in short term (16 weeks) EN and EW from 89.98 ± 0.81 eggs and 43.52 ± 0.08 g, respectively in G4 to 94.98 ± 0.51 eggs and 45.06 ± 0.12 g, respectively in G6, and mean realized genetic gain of 119.18 g for 39 week BW in

EN, and 0.23 to 0.69 for BWFE and relative economic weight of 2.02 to 2.24, 2.45 to 2.78, and − 1.00 for EW, EN, and BWFE, respectively. These studies indicate that NICs can be improved for commercial utility as layer or dual purpose bird (meat

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, respec-

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

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

925.76 g over three generations. The author reported h<sup>2</sup>

and egg production) using within ecotype selection.

estimates that ranged from 0.12 to 0.24 for EN, 0.34 to 0.43 for

values of range 0.28 to 0.52 for EW, 0.14 to 0.45 for

) ranged from 0.20 to 0.91, 0.10 to 0.76, and

estimate of 0.24 ± 0.27 to

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

authors reported h<sup>2</sup>

males. The author reported h<sup>2</sup>

**and genotypes**

tively. Coefficient of determination (R<sup>2</sup>

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

and 5.77, and − 2.37 and − 1.00, respectively in G0,; 13.07 and 3.82, 23.69 and 6.93, and − 3.42 and − 1.00, respectively in G1; and 16.80 and 2.89, 30.75 and 5.28, and − 5.82 and − 1.00, respectively in G2 generation. Using an index of weighted breeding values that considered the heritability, relative economic weight, and standardized trait values, [97] reported expected average direct genetic gain per generation for short term (16 weeks) egg production of 12.58 eggs, 1.98 g, and 25.04 g for EN, EW, and BWFE, respectively; realized genetic gain of 2.19 and 1.59 eggs for EN, 1.65 and 0.26 g for EW, and − 25.60 and 123.64 g for BWFE for G0 and G1, respectively; and corresponding values for ratio of realized to expected genetic gain of 2.27 and 1.22, 3.15 and 0.24, and 0.95 and 2.21, respectively. The authors reported h<sup>2</sup> estimates that ranged from 0.12 to 0.24 for EN, 0.34 to 0.43 for EW and 0.57 to 0.69 for BWFE. For males, improvement in 39 week body weight was observed with realized genetic gain of 284.22 and 111.87 g for G0 and G1, respectively and average expected gain of 508.50 g per generation following mass selection. Ogbu [98] had reported improvement in BW from hatch to 39 weeks following mass selection in male HE IC with final body weight increased from 1372.66 ± 16.46 g in G0 to 1768.75 ± 33.15 g in G2 implying a cumulative gain of 925.76 g over three generations. The author reported h<sup>2</sup> estimate of 0.24 ± 0.27 to 0.59 ± 0.45 and 0.13 ± 0.49 to 0.25 ± 0.31 across the three generations for BW from 12 to 20 and 39 weeks of age, respectively. Agbo [99] furthered the selection for improved growth and egg production in HE ICs from 4th to 6th generation and reported improvement in short term (16 weeks) EN and EW from 89.98 ± 0.81 eggs and 43.52 ± 0.08 g, respectively in G4 to 94.98 ± 0.51 eggs and 45.06 ± 0.12 g, respectively in G6, and mean realized genetic gain of 119.18 g for 39 week BW in males. The author reported h<sup>2</sup> values of range 0.28 to 0.52 for EW, 0.14 to 0.45 for EN, and 0.23 to 0.69 for BWFE and relative economic weight of 2.02 to 2.24, 2.45 to 2.78, and − 1.00 for EW, EN, and BWFE, respectively. These studies indicate that NICs can be improved for commercial utility as layer or dual purpose bird (meat and egg production) using within ecotype selection.
