Evaluation of growth characteristics of parental, F₁, F₂ and backcross chickens from broiler and Black Australorp stocks in Tanzania

W G Munisi, S H Mbaga¹ and A M Katule¹

Tanzania Livestock Research Institute - Mpwapwa, P.O.Box 202 Dodoma, Tanzania
wilfredmunisi@yahoo.com
¹ Department of Animal Science and Production, Sokoine University of Agriculture,
PO Box 3014, Morogoro, Tanzania

Abstract

This study was done in central Tanzania to evaluate growth performance of parental, F₁, F₂ and backcrosses of Broiler (BB) and Black Australorp (AA) stocks. The parental stocks (BB and AA) and the F1 which performed better in phase one of the study (i.e. Single cross between Black Australorp and broiler, AB and its reciprocal, BA) were used in the crossing to produce 11 genetic stocks totaling 396 birds. Birds were fed on nutritionally balanced diets to meet their requirements as per age and physiological stage. Body weights at day old, 4, 8, 12 weeks of age and body weight at sexual maturity (BWSM) as well as livability from day old to 12 weeks were evaluated. The data on growth traits were recorded on individual bird basis and analyzed using general linear models, while frequency was used for livability analysis.

 

Genetic stocks differed in body weight at different weighing periods in both males and females. The broiler parental stocks (BB) were heavier than all other genetic stocks at all stages of growth and sex except at hatching in females. From fourth to 12 weeks of age, the genetic stocks with 75% broiler and 25% Black Australorp (¼A¾B) inheritance were heavier than the genetic stocks with 75% Black Australorp and 25% broiler (¾A¼B). The genetic stocks with 75% broiler and 25% Black Australorp (¼A¾B) inheritance were also heavier than other crosses in body weight at sexual maturity. There were no differences among genetic stocks with respect to livability in both sexes. It is concluded that the backcrosses of broiler performed better than the backcrosses of Black Australorp, F₁ and F₂ with regard to body weight at different stages of growth including body weight at sexual maturity as well as livability.

Key words: backcross, body weight, crossbreeding, crossbred, genetic stocks, livability

Introduction

Indigenous chickens in Tanzania supply most of the poultry meat and eggs consumed in rural areas as well as 20% of meat and eggs in per urban and urban areas (Melewas 1989; Minga et al 1996). Despite their availability in almost every household in rural areas and their social economic as well as nutritional roles, indigenous chickens of Tanzania are small in size and grow slowly. The adult body weight ranges from 1300 to 2010 g (Katule 1990).

 

Many attempts have been done to improve growth performance of indigenous chickens mostly by crossing cockerels of exotic breeds with indigenous chicken pullets (Masawe et al 2009). Currently, such improvements, though uncoordinated have been widely promoted through Local Government Authorities (LGAs) under the Agriculture Sector Development Program (ASDP) with funds from Tanzania Social Action Fund (TASAF) and councils own sources through District Agriculture Development Plans (DADPs). However, lack of recorded data on the productive performance of chickens in the field makes it difficult to evaluate the contribution of these efforts as well as its sustainability. Katule (1990) conducted a study to improve the performance of the indigenous chickens by crossbreeding and found that crossbreeding tends to improve growth and production. However, the study lacked information on reciprocal effect which is considered to be an important determinant of chicken’s performance. Munisi et al (2015) also demonstrated that crossing broiler and indigenous chickens produced crossbreds with heavy body weights. Despite the fact that crossbred birds performed well with respect to growth performance, they showed rather poor performance in livability. The authors observed that the F₁ cross between broiler and Black Australorp stocks had the best combined (overall) performance which included growth and livability. However it remains to be seen whether or not the observed overall superiority observed in the F₁ cross between broiler and Black Australorp stocks would be carried out to F₂ and subsequent generations.

 

In view of the above scenario the current study was conducted to evaluate growth performance of F₂ and backcrosses derived from crossing Broiler and Black Australorp chickens. The information would be useful in an attempt to produce superior genetic stocks that would suit Tanzanian production environment.

Materials and Methods

Experimental site and study layout

 

The study was conducted at the Tanzania Livestock Research Institute, Mpwapwa (TALIRI) as described by Munisi et al (2015). In this study 11 genetic stocks totaling 396 birds (parental meat and Black Australorp stocks as well as F₁, F₂ and backcrosses) were obtained by crossing the genetic stocks which had the best overall performance in growth and livability in the first phase of study (Reciprocal crosses AB and BA of Broiler and Black Australorp stocks). These genetic groups with the overall performance were selected using independent culling by considering growth, egg production at 180 days after attainment of sexual maturity (EN180) as well as livability traits. The broiler and Black Australorp stocks (BB and AA) as well as the F_1’s were included in the second phase to provide the basis for evaluating the genetic effects in the F₂ and backcross progeny.The mating arrangement for production of experimental birds was as shown in Table 1. With this mating arrangement it was possible to produce progeny groups with graded levels of inheritance from both the broiler and Black Australorp stocks ranging from 0 to 100%. 

Management of experimental animals

 

Chicks were wing banded at day old and brooded on the floor. The birds were transferred to floor rearing pens after two months of age. The experimental birds were intermingled by sex. The birds of each genetic group were raised in more than one pen. Details of feeding and disease prevention measures were described by Munisi et al (2015).

 

Data collection

 

Individual birds were weighed at day old and at four week intervals up to the age of 12 weeks using an electronic balance. Data on livability were obtained from the record book maintained on daily basis. The average number of birds of each genetic stock alive in a given period was obtained by summing up the number of birds alive each day during the respective period and dividing by the number of days in that period. The livability was recorded from day old to 12 weeks of age. Data for body weight at sexual maturity (BWSM) were also recorded on individual bird basis. Age at sexual maturity was considered as the age at which the first egg was laid.

 

Statistical data analysis

 

The data on weights of birds were analyzed using the General Linear Models (GLM) procedure of SAS (2003) using the following statistical model.

Y_ijk = µ + G_i + P (G)_ij+ e_ijk…………………………………………………………(1).

Where:

Y_ijk = observation from the k^th bird in thej^th pen of the i^th genetic stock,

µ = general mean common to all birds in the experiment,

G_i= the fixed effect of the i^thgenetic stock

P (G)_ij = effect of the j^th pen within the genetic stock,

e_ijk = random effects peculiar to each individual bird.  

 

Data on livability were analysed using the frequencies and Chi-square option of SAS (2003) to test associations between genetic stocks and livability.

Results and discussions

Variation among genetic stocks with respect to body weights

 

Results in Table 2 show the least squares means for body weight at hatch day (0), 4, 8, 12 weeks of age in both sexes and body weight at sexual maturity (BWSM) for female birds. The genetic stocks differed in body weight at all stages of growth and sex except at 4^th week of age in males. With exception of age at hatching in female birds, the broiler stocks were heavier than other genetic stocks in both sexes and different stages of growth. However, difference between broiler and other genetic stocks was observed at 4^th and12^th weeks for female birds while in male birds, the differences were observed at 4,8 and 12^th weeks of age. The better performance of broiler than other stocks with regard to body weight was expected. This is because broilers have been selected for rapid growth and heavy body weight. This is also in agreement with Katule (1992) observations that, the highest performance is expected in the breed which had been developed purposely for higher performance in that trait.

 

Comparison of crossbreds revealed that backcrosses to the broiler stocks were heavier than the backcrosses to the Black Australorp stocks at all stages of growth and sex except at hatching in males. The observed heavy body weight for genetic stock with high proportion of inheritance drawn from broiler was expected since body size is influenced largely by additive gene effects (Katule, 1990). The author also revealed that the backcrosses to meat breed were heavier than the backcross to the egg type birds. Furthermore, the findings from this study are in agreement with those of Siwendu et al (2013) and Munisi et al (2015) who observed that crossbreds resulting from crossing broiler with other genetic stocks had heavier body weights than other crossbreds.

 

With respect to body weight at sexual maturity, several salient features were observed. First, the genetic stock with 75% inheritance from the broiler and 25% from the Black Australorp (¼A¾B or ABBB) were heavier than all other crossbreds. The crossbreds (ABBB) were also heavier than their reciprocals (BBAB). This probably due to the fact that these reciprocal crosses may have similar heterosis and additive breed effects; the differences between them may be caused by the influence of broiler which was used as dam parent. The findings agree with that reported by Nwachukwu and Ogbu (2015) who revealed heavy body weight at first egg for reciprocal backcross individuals when broiler was used as dam parent. Similar report (Katule 1990) has shown that heavy breeds are more favorable as dams than light breeds. However, the obtained body weight at first egg for ABBB in the current study is not very far from the range of 3300 to 3700g reported by Bornstein et al (1984) for broiler breeder hen.

 

 Secondly, the genetic stock with 75% inheritance from the broiler and 25% from the Black Australorp were heavier than the F₁ cross between Black Australorp and broiler stocks. This may be due to the result of increased broiler blood to 75 % compared to 50% in the F₁ cross between Black Australorp and broiler stocks and their reciprocals.

 

The third observation demonstrated that F₁ cross between Black Australorp and broiler stocks (AABB) were significantly heavier than the F₂ crossbreds (i.e. ABAB, BAAB and ABBA). This contradicts the findings of Nwachukwu and Ogbu (2015) who observed that F₂ crossbreds resulting from Abor Acre broiler breederand indigenous chickens were superior to F₁ crossbreds in body weight at first egg.

Variation among genetic stocks with respect to livability

 

The livability performance of the genetic stocks during juvenile stage of growth is shown in Table 3. There were no differences in livability amongst genetic stocks in both sexes. However, the backcross to the broiler genetic stock and its reciprocal followed by F₁ cross between Black Australorp and broiler stock survived rather better than other genetic stocks in females. In males, the F₁ cross between broiler and Black Australorp stocks followed by the genetic stocks with 75% inheritance from the broiler and 25% from Black Australorp stocks showed rather better performance in this trait than other genetic stocks. The Black Australorp (AA) recorded lower livability than other genetic stocks. However, in this phase of study there was an outbreak of Salmonella and coccidiosis which caused mortality and to some extent affected the performance of some genetic stocks. Apart from these diseases, there were few incidences of death caused by ascites specifically in broiler stocks. Nonetheless, the observed better livability for genetic stocks with 75% inheritance from the broiler and 25% from Black Australorp stocks than its reciprocal in both sexes was probably due to broiler background maternal effects when used as dams. The results are in agreement to the findings of Custodio (2000) who revealed that maternal effects contributed to a higher viability of the progeny from the White Leghorn dams compared to Rubronegra (Black Australorp x New Hampshire) dams. The results also agree with those of Fairfull et al (1983) who observed reciprocal effects in the crosses of laying hens for viability trait. According to Fairfull (1990) cited by Tuiskula-Haavisto et al (2004) reciprocal effects may be due to sex-linked effects and or maternal effects. The observed higher livability for the F1 cross between broiler and Black Australorp stocks is in agreement with Mata and Mwakifuna (2012) who reported that Hyblack (Black Australorp X Rhode Island Red) chickens had lower mortality than other stocks.