Comparisons of egg production and quality traits of parental and crosses of broiler and Black Australorp chickens in Tanzania

W G Munisi, A M Katule¹ and S H Mbaga¹

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,P. O. Box 3014, Morogoro, Tanzania

Abstract

A study was conducted in Semi arid Central Tanzania to compare egg production and quality of parental and crosses of broiler and Black Australorp chickens. 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 experimental genetic stocks. Birds were fed on nutritionally balanced diets to meet their requirements as per age and physiological stage. Variables studied were egg weight at first egg (FEW), egg weight at 36 weeks of age (EWT36), Age at sexual maturity (ASM), egg shell thickness at 36 weeks of age (EST36), egg shape index at 36 weeks of age (ESI36) and egg number at 90 days after attainment of sexual maturity (EN90) and laying rate (LR). The data on egg production and quality were recorded on individual bird basis and analyzed using the General Linear Models procedure of SAS (2003).

The results revealed that genetic stocks differed in FEW, EWT36, EN90 and LR while no differences were observed among genetic stocks in ASM, EST36 and ESI36 traits. The backcross to broiler stocks (¼A¾B or AB/BB) had heavier FEW and EWT36 than F₁ and F₂ genetic stocks. With regard to EN90, the backcross to Black Australorp (¾A¼B or BA/AA) produced more eggs with better laying rate than other genetic stocks. It is concluded that the backcross to broiler stock (¼A¾B or AB/BB) and backcross to Black australorp (¾A¼B or BA/AA) could serve as stocks for production of heavier and more eggs respectively.

Key words: back cross, egg shape index, egg shell thickness, egg weight, genetic stock

Introduction

As a result of increasing human population there is increase in the demand of animal protein in many countries of Africa including Tanzania. It is also believed that as income rises people will spend big share in their food budget on animal protein such as meat and eggs. In Tanzania per capita consumption of eggs was 106, which is 35% of eggs per person per year recommended by FAO (MLFD, 2015). In 2002, Food and Agriculture Organization of the United Nations (FAO) projected overall chicken consumption in Tanzania to be 42.7 metric tons while consumption of poultry meat in 2030 is projected at 170.7 metric tons, of which 104.7 metric tons will be consumed in rural areas and 66 metric tons in urban areas (RIU, 2012). However, according to RIU (2012) growth rate of poultry sub sector is slow. This causes egg and poultry meat production to lag behind the demands as human population increase. Inadequate high yielding genetic stocks, poor disease control measures and feeds of inferior quality are among the causes of slow growth rate of the sector.

To cope with the increased demands, exotic breeds have been introduced in the country way back in 1937 with the intension of upgrading the productivity of indigenous chickens. Currently a number of breeds such as Rhode Island Red, Light Sussex, White leghorns, Brown Leghorns and Black Australorp are raised under different production systems (Goromela, 2009). The Black Australorp for example is used as layers in southern parts of Tanzania and it has a good scavenging ability. The commercial broilers on the other hand are used as meat strains in urban and per urban areas of the country. Research attempts have been done to cross indigenous and exotic breeds in order to produce crossbreds that yielded more meat and eggs or with superiority in livability. For example in Malawi, a cross between Black Australorp and Rhode Island Red, popularly known as Hyblack (HB) was found to exhibit lower mortality compared to the parental stocks (Mata and Mwakifuna, 2012), whilst Patrick and Phakedi, (2013) reported that Black Australorp and Tswana crossbred showed superior growth performance than Tswana parental stocks. However, Timothy and Clemens (2003) compared productivity of Black Australorp and indigenous chickens under scavenging environment where by they reported higher mortalities for parental Black Australorp had higher mortality rate than indigenous chicken strains.

Munisi et al (2015a) recently reported that a cross between Black Australorp and broiler stocks produced F₁ crossbreds that had better performance in growth and livability.

In the rural areas farmers are interested in dual dual purpose breeds that can attain higher growth rate, be able to survive but also have the ability to produce appreciable number of eggs and of good quality. Thus the objective of this study was to compare egg production and quality for F₂ and backcrosses chickens derived from crossing broiler and Black Australorp chickens.

Material and methods

Experimental site

Experimental site for this study was as described by Munisi et al (2015b).

Study layout and procedures

This was second phase of the study on prospects of developing a high performing dual purpose stock of chickens for Tanzania through synthetic breeding. In this phase, eleven genetic stocks were obtained by crossing the genetic stocks which performed better than other stocks (i.e The cross between broiler and Black Australorp and its reciprocal) and the parental stocks constituting them (i.e broiler and Black Australorp) in the mating arrangement shown in Table 1 below. The proportion of both the BB and AA parental breeds in the progeny genotypes varied from 0 to 100% at increment of 25 percent units.

Management of experimental animals

Chicks were wing banded at day old and the chickens were transferred to floor rearing pens after two months of age. The female chickens were raised until they reached 36 weeks of age. Feeding and disease prevention were as described by Munisi et al (2015a).

Data collection

The variables recorded included age at sexual maturity (ASM), egg weight at sexual maturity or first egg weight (FEW), average egg weight at 36 weeks of age (EWT36), egg shell thickness at 36 weeks of age (EST36), egg shape index at 36 weeks of age (ESI36), number of eggs in 90 days of laying after attainment of sexual maturity (EN90) and laying rate (LR). All studied variables were recorded on individual bird basis.

ASM was considered as the age at which the first egg was laid. FEW and EWT36 were taken by an electronic balance which could weigh to the nearest 0.1g. EST36 was recorded as the average of three readings taken from different sides of an egg shell, the equator (middle), narrow and broad end using a digital caliper. ESI36 was recorded by taking the ratio of distance across (width) to length of an egg and multiplying by 100. Laying rate was computed from total egg number divide by laying period in days.

Statistical data analysis

The data on egg production and quality traits of birds were analyzed using the SAS General Linear Models (GLM) procedure using the following statistical model 1.

Y_ijk = µ + G_i + P(G) _ij + e_{ijk                                         (1)}

Where:

Y_ijk is an observation from the k^th bird in the j^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^th genetic stock

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

e_ijk = random effects peculiar to each individual bird.

Results and discussions

Performance of genetic stocks with respect to age at sexual maturity and egg weights

Data summarized in Table 2 shows that the broiler parental stocks had heaviest first egg and egg at 36 weeks compared to other genetic stocks. With respect to crosses, it was observed that the genetic stocks with 75% inheritance from the broiler and 25% from Black Australorp stocks (¼A¾B or AB/BB) had the heaviest eggs at maturity (FEW) and 36 weeks of age (EWT36) compared to F₁ and F₂ genetic stocks. The 54.9g eggs for ¼A¾B observed in the current study are closer to the egg size of 56 to 58 g for improved breeds (Katule 1990). Heavy eggs laid by this genetic stock (¼A¾B) may probably be due to the fact that they had heavy body weight at first egg (Munisi et al 2015b). According to Udeh (2010) the heavier a bird is at start of lay the bigger would be eggs laid. Ayorinde and Sado (1988) reported that body weight is among the factors influencing egg size. Furthermore, other research works (Oni et al 1991; Adenowo et al 1995; Agaviezor et al 2011) revealed positive genetic correlation between body weight at first egg and egg weight. Like wise egg weight tends to increase as body weight increase (Summers and Leeson 1983; Lacin et al 2008). This is due to the fact that high body weight results in large egg length, width and mass, the parameters which affect egg weight as well (Harms et al 1982; Leeson and Summers 1987; Du Plessis and Erasmus 1972).

There were no differences among genetic stocks with respect to age at sexual maturity. However, the genetic stocks with 75% inheritance from the Black Australorp and 25% from broiler stocks (¾A¼B or BA/AA) tends to have lower ASM (174 days), whilst broiler parental stocks matured late (198 days). The small size of ¾A¼B or BA/AA as reported by Munisi et al (2015b) might be the cause of early attainment of sexual maturity. This is supported by other works (Katule 1990; Yeasmin et al 2003; Zaman et al (2004) who reported sexual maturity to be attained late in heavy breeds. This trait is also influenced by other environmental factors like temperature, day length and nutrition.

Performances of genetic stocks with respect to egg production and quality traits

Information on the egg production and laying rate of different genetic groups is presented in Table 3. There were differences among the genetic groups with respect to egg numbers at 90 days after sexual maturity (EN90) and laying rate (LR). The genetic stock with 75% inheritance from the Black Australorp and 25% from broiler stocks (¾A¼B or BA/AA) laid higher numbers of eggs (29.6) than other genetic stocks. The results also revealed that no differences were revealed between the F₁ and F₂ genetic stocks in EN90. The observed higher number of eggs from BA/AA than from other genetic stocks in the present study may have been due to its early age at sexual maturity. According to El-Dlebshany (2008) early maturing genetic groups produced more eggs during 90 days after sexual maturity. Another factor which might have contributed to the high performance of this genetic group could be its low body weight (Munisi et al 2015b). This is supported by the findings by Ayorinde and Oke (1995) who reported that lighter birds lay more eggs than heavy birds.

There were differences among genetic groups for laying rate. The genetic stock with 75% inheritance from the Black Australorp and 25% from broiler stocks (¾A¼B or BA/AA) showed better laying rate than other genetic stocks, followed by Black Australorps (AA), while the broiler stock had the lowest laying rate. However, the laying rate for all the genetic stocks was not satisfactory probably due to the fact that the parental breeds constituting the genetic groups are developed for meat (broiler) and dual purposes (Black Australorp). The laying rate of 35% for BA/AA is however, higher than that of 32% for the cross between Rhode Island Red and Fayoumi obtained by Zaman et al (2004).

Table 4 represents performance of different genetic groups for egg quality traits. The results reveal that genetic groups did not differ in egg shell thickness at 36 weeks of age. However, the backcross to Black Australorp (¾A¼B or AA/BA) tended to have thicker egg shells than other genetic stocks.

The results also show that egg shape indices did not differ among genetic stocks. However, the Black Australorp parental stocks (AA) followed by F ₁ cross between Black Australorp and broiler as well as F₂ crossbreds (½A½B or AB/AB) tended to have higher egg shape indices than other genetic group although the values were slightly lower than those reported for the cross between Red Broiler and White Plymouth rock mini (77.8) as well as that of the cross between Red broiler x Labelle (76.2) reported by Ralcheva et al (2009). According to the Authors, egg shape index of 76-78 is considered to be regular and fit for incubation.

Conclusions

• The results of this study revealed that the backcross to broiler stocks (¼A¾B or AB/BB) had heavier eggs than F₁ and F₂ genetic stocks.
  
  
• The backcross to Black Australorp (¾A¼B or BA/AA) laid more eggs and showed better laying rate than both F₁ and F₂ genetic stocks.
  
  
• The genetic stocks did not differ in egg shell thickness, age at sexual maturity and egg shell index.
  
  
• Thus, the present findings suggest that the backcross to broiler stock (¼A¾B or AB/BB) and backcross to Black australorp (¾A¼B or BA/AA) could be serve as stocks for production of heavier and more eggs respectively.

Acknowledgements

The authors acknowledge the Commission of Science and Technology (COSTECH) for the financial support and National Livestock Research Institute (TALIRI-Mpwapwa) for providing infrastructures.

References

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Received 12 April 2016; Accepted 16 April 2016; Published 2 June 2016

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