Diallel crossing analysis for livability data involving two standard and two native Egyptian chicken breeds

M M Iraqi, E A Afifi, A M Abdel-Ghany^* and M Afram^**

Animal Production Department, Faculty of Agriculture at Moshtohor, Zagazig University, Benha Branch, Egypt
^* Animal Production Department, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt
^**Animal Production Research Institute, Ministry of Agriculture, Dokki, Cairo, Egypt
iraqi@yalla.com

Abstract

Two local breeds, namely Fayoumi (FA) and Dandarawi (DA) and two exotic ones named Rhode Island Red (RIR) and White Leghorn (WL) were used in 4x4 diallel cross mating system. Thirty-two breeding pens were used. Two sires were mated to 16 dams in each breeding pen. Progeny of F₁ of all breed groups (16 groups) were produced in three hatches within two years. Records of 7285 chicks were used to estimate purebreds, heterosis, general (GCA) and specific (SCA) combining abilities, maternal ability (MA) and reciprocal or sex-linked (SL) effects on livability traits. A simple additive genetic model was used to analyze adjusted livability records (expressed as numbers alive counted from hatch up to 12 weeks of age) to determine the crossbreeding effects responsible for the differences among breeding groups.

Results showed that WL chicks had superiority in livability percentage over all purebreds during all the studied periods, followed by RIR. Differences between means of livability of exotic and native breeds were significant (P<0.05). Most of crossbreds had higher livability than purebreds. Heterotic effect was highly significant (P<0.01) on livability traits during all the studied periods. Crossbreds of FAxDA gave the highest heterotic effect for livability percentage during all the studied periods, except at 12 weeks of age. Crossbreds of RIRxFA, WLxFA and WLxDA, respectively ranked as the first, second and third for economic heterosis of complementary traits (livability and body weight). They were 37.6, 31.2 and 25.0%, respectively. Significant (P<0.01) differences among purebreds for the effects of MA, GCA, SCA and SL were obtained on all livability traits. The DA breed gave the highest and positive effect of GCA on all livability traits. The FA had superior estimates for MA in all studied traits. Clearly, the RIRxFA and WLxDA crosses gave the highest and positive estimates of SCA for most traits of livability traits compared to the other crossbreds. The WLxDA cross had superior SL effects for traits at 8 and 12 weeks of age.

From the previous results, it could be concluded that RIR sires (as an exotic breed) and FA dams (as a native breed) would be selected to produce broilers with higher viability in Egypt through crossbreeding programs.

Key words: Economic heterosis, general and specific combining abilities, maternal effect, purebreds, sex-linked effect and livability traits.

Introduction

Crossbreeding is one of the tools for exploiting genetic variation. The main purpose of crossing in chicken is to produce superior crosses (i.e. make use of hybrid vigor), to improve fitness and fertility traits and to combine different characteristics in which the crossed breeds were valuable (Willham and Pollak 1985; Hanafi and Iraqi 200 1). Crossbreeding uses pure- or line-breeding to improve economic traits through the use of complementarity traits or economic heterosis. Complementarity is often very important to success the crossbreeding programs. Often positive complementarity arises because of a multiplier trait, e.g., reproduction and viability traits. Moreover, as with single trait heterosis, however, economic heterosis may be negative (Van Vleck 1993). Heterosis caused by dominance is proportional to heterozygosity and dominance was broadly believed to be the sole cause of heterosis in animals. However, epistasis was shown to be a major mechanism of heterosis in chicken (Sheridan 1981). For the most part, heterosis resulting from epistasis is complicated or hardly attainable to predict because of the number and type of interactions are usually unknown and it could also be affected by dominance. Likewise, diallel crossing schemes makes accessible the assessment of general and specific combining abilities as well as maternal and sex-linked consequences (Griffing 1956a and b).

Livability is a composite character concerns the question of the adaptive value for the organism. Furthermore, it relates to all physiological steps leading from genotype to the resultant phenotype. Livability shows less overall genetic variation weighted against other economic traits (Hill and Nordskog 1958, Khalil et al 1999). Heterosis for livability results from a complex interaction of the specific effects of several diseases and stresses. The productivity and economics of chicken farming depends, among many aspects, upon their livability. However, few studies have been published on the genetic comparison between purebred and crossbred chicken breed groups for livability traits and no reports are available on complementary traits. Therefore, this study was conducted to evaluate genetically livability traits the age intervals of hatch-2, 2-4, 4-6, 6-8 and 8-12 weeks of age using two exotic breeds (Rhode Island Red, RIR and White Leghorn, WL) and two indigenous ones (Fayoumi, FA and Dandarawi, DA) as well as their reciprocal crosses to evaluate the potential of additive and non-additive effects for improving livability traits during the growing period through estimating some inheritance effects (mating group, general and specific combining abilities as well as maternal and sex linkage consequences) besides individual, direct and economic heterotic effects on livability traits.

Materials and methods

Breeding plan and management

This study was carried out at El-Qanater Poultry Research Station, Animal Production Research Institute, Ministry of Agriculture, Egypt. Two local breeds namely Fayoumi (FA) and Dandarawi (DA) and two exotic ones named Rhode Island Red (RIR) and White Leghorn (WL) were used in 4x4 diallel mating system. Breeds of RIR and WL are the most well spread and adapted to the condition of Egypt, while FA and DA might be regarded as the principal well characterized local breeds of chicken.

All possible purebreds (4 groups) and crossbreds (12 groups) were made among the four breeds. A total number of 16 sires and 128 dams randomly chosen from each breed were used as parents. Thirty-two breeding pens were used. In each breeding pen, two sires were mated to 16 dams to constitute a particular cross which was repeated twice. Each sire was represented in the three hatches. All eggs produced from each breeding pen were individually recorded according to breed group and collected daily for a ten days period. Progeny of F₁ of all breed groups (16 groups) were produced in three hatches within two years. On day of hatch, all chicks were wings banded to keep their breed groups. The chicks were brooded and reared from hatch up to 12 weeks of age at the floor which heated by kerosene. Chicks were fed ad libitum using ration contained 22.4 % crude protein, 4.8 % fat and 6.8 % fibers. All chicks were vaccinated, medicated and subjected to the same managerial conditions.

Data and statistical analysis

Livability data of 7285 chicks were individually recorded during the intervals of hatch-2 (L2), 2-4 (L4), 4-6 (L6), 6-8 (L8) and 8-12 (L12) weeks of age. Birds were given the code 1 or 0 to represent their situation if they were alive or dead at a specific age, respectively. Data of livability traits were analyzed using SAS program under Windows (SAS 1996) according to the following linear model:

Where:
y_ijklm= the m^th observation on the bird hatched in the l^th year of the k^th sex in the j^th hatch of the i^th breed group,
μ= the overall mean,
G_i= the fixed effect of the i^th breed group,
H_j= the fixed of the j^th hatch,
S_k= the fixed effect of the k^th sex,
Y_l= the fixed effect of the l^th year,
(GH)_ij= the fixed effect of interaction between i^th breed group and j^th hatch,
(GS)_ik= the fixed effect of interaction between i^th breed group and k^th sex,
(HS)_jk= the fixed effect of interaction between j^th hatch and k^th sex, and
(GHS)_ijk= the fixed effect of interaction among i^th breed group, j^th hatch and k^th sex, and

 

Genetic analysis

Data adjusted for the fixed effects were analyzed using the following model suggested by Kidwell et al (1960):

Where:
y_hijk= the k^th observation on the individual bird produced from the i^th breed of sire and the j^th breed of dam in the h^th type of breeding (purebred or crossbred),
μ= the overall mean,
a_h= an effect common to progeny of the h^th type of breeding,
P_ii= the effect common to all progeny of a mating between of the i^th breed of sire and the i^th breed of dam,
g_i(g_j)= the effect of general combining ability (GCA) of the i^th(j^th) breed,
m_j= the effect of maternal ability (MA) for the j^th breed of dam,

This model was used to test the significance and to estimate the effects of heterosis, purebreds, maternal, GCA, SCA and SL by applying the restrictions suggested by Harvey (1979).

Results and discussion

Means of genetic groups

Least squares means presented in Table 1 show that White Leghorn (WL) chicks had superiority over all pure breeds livability during all the studied periods, followed (in most cases) by Rhode Island Red (RIR) with no signifivant difference between the two standard breeds till the 6^th week of age.

However, when considering the native breeds, it was obvious that Dandarawi chicks (DA) significantly surpassed Fayoumi (FA) ones in their livability during all periods under consideration. In this respect, livability differences among purebred shown in Table 2, were highly significant (P<0.01). On the other hand, Khalil et al (1999) found non-significant differences between White Leghorn and Baladi Saudi chickens. Also, Custodio (2000) revealed that the differences among breeding types were not statistically significant.

When compared between purebred and crossbred chicks, results show that crossbreds gave higher livability percentage at all the studied periods. Results in Table 3 showed that crosses increased the general mean by 1.25, 1.96, 2.69, 1.75 and 2.14 % for L2, L4, L6, L8 and L12, respectively. These results could constitute an encouraging factor for poultry producers in Egypt to cross their native breeds with the exotic ones. Conversely, Khalil et al (1999) found that livability traits in purebreds were higher than crossbreds of White Leghorn with Saudi Arabia chickens.