Previous PageTable Of ContentsNext Page

POULTRY BREEDING IN ZIMBABWE


SUMMARY

INTRODUCTION

BREEDING IN INDIGENOUS FLOCKS

BREEDING IN COMMERCIAL POULTRY BREEDS AND STRAINS

THE FUTURE

REFERENCES


A. T. Faranisi
Irvine's Day Old Chicks, P 0 Box 815, Harare, Zlmbabwe.

SUMMARY

The poultry industry in Zimbabwe is based on both indigenous and imported poultry strains. Commercial production is dominated by imported strains and indigenous strains have remained insignificant due to lack of genetic improvement in all commercially important traits. This paper presents a brief account of commercial poultry breeding and traits which are considered important in Zimbabwe.

INTRODUCTION

Poultry breeding in Zimbabwe is based on commercial strains produced by the four main breeders and thousands of indigenous flocks in the communal farming sector and backyard flocks in urban areas. Trends in broiler, egg and day old chick production are given in Table 1.

Table 1. Trends in production of broilers, table eggs and day old chicks 1985 - 1994

Year

Sales by volume from commercial producers

 

Table broilers

(Millions)

Day old

Broilers

(millions)

    Sexed

    pullets

    (millions)

Eggs

(millions of dozens)

1985

7.2

6.3

0.7

11.7

1986

7.1

8.2

1.6

11.5

1987

8.4

9.5

1.5

12.0

1988

10.5

11.9

1.5

14.1

1989

11.5

15.2

1.9

17.8

1990

13.0

16.1

1.6

18.7

1991

13.7

23.5

2.3

19.4

1992

13.2

15.1

1.3

19.6

1993

11.4

15.6

2.1

17.5

Source: C.S.O. (1994)

Although the production of commercial poultry strains is ever increasing as shown in Table 1, the indigenous flocks still contribute significantly to meat and egg requirements in Zimbabwe, but statistics are not available.

BREEDING IN INDIGENOUS FLOCKS

Breeding and selection in indigenous poultry has been largely left to nature and to date no differentiation into broiler or layer strains has occurred. Consequently, production in both meat and egg production has remained very low when compared with commercial strains. Field observations for egg production, for example, show that in a laying cycle indigenous hens will produce 10 - 50 eggs with an average weight not exceeding 52 grammes. Commercial strains on the other hand can produce up to 300 eggs with an average weight of 63 - 65g. While some of the difference in productivity may be due to non-genetic factors such as feeding regime and management system, most of it is a result of genetic differences.

BREEDING IN COMMERCIAL POULTRY BREEDS AND STRAINS

As mentioned earlier, commercial poultry breeding is conducted by a few companies in Zimbabwe. Each of the companies produces its own broiler or layer stock from either greatgrandparents (GGP) or grandparents (GP) and parents, imported from primary breeders in Europe. Greatgrandparents are essentially purelines. The progeny of the great grandparents that are selected to produce parents are referred to as grandparents and their offspring are called parents. Eggs from parents then hatch to give broiler or layer chicks for commercial production.

The breeding companies generally use three line or four line crosses in their breeding programmes. A three line cross involves crossing two strains with different qualities and then crossing their progeny with the third line. In a four line cross, two of the four lines are crossed and the remaining two are also crossed. The male offspring of the one cross are then mated to the female offspring of the other to produce parent stock. Parent stock is retained by the breeders and only commercial day old chicks are sold to producers, but the breeders remain the largest producers of commercial poultry. The poultry industry can therefore be described as shown in Figure 1.

Figure 1. Structure Of Commercial Poultry Breeding in Zimbabwe

GP' S

GP'S

(From Europe)

Local breeders

Commercial farms

Small scale producers

EGG LAYING STRAINS

Nearly all the genetic improvement in commercial layer chickens is undertaken by primary breeders. Local breeders then choose from the primary breeders genetic stock that will best meet their local market demands. Traits that receive most attention are ease of sexing chicks, feed conversion, egg productions, egg size and quality of eggs.

CHICK SEXING

Layer chick producers depend on colour and feather sexing to separate cocks and pullets at day old. Plumage colour in local brown egg layers is controlled by sex linked genes which produce the gold/brown or silver/white plumage. At the parent level males are brown coloured and the pullets are white coloured. Mating these parents produces pullets with a golden down and males with a silver down. Sexing day old chicks, which all have the same colour, is achieved by use of sex linked fast feathering and slow feathering genes. These genes on some strains, for example, will produce fast feathering pullets in the female line pullets and slow feathering males.

This ability to sex layer pullets at day old significantly reduces the cost of raising layer pullets.

EGG PRODUCTION

Egg production is made up of several associated characteristics such as age at onset of lay, higher peak rate and persistence of lay. Selection or higher egg production is normally directed at these traits (Flock, 1994). Of the above traits, emphasis or selection pressure on age at onset of lay will be reduced as most egg producers feel that genetically early maturing pullets are difficult to bring into lay and manage.

BODYWEIGHT AND FEED CONVERSION

Local breeders continually import strains with lower bodyweights as this reduces pullet maintenance costs. With the ever increasing costs of stockfeeds, strains with the best feed conversion ratios (FCR) are preferred. Over the years, improvements in FCR have occurred as a correlated response to selection for greater egg mass production and lower bodyweight by primary breeders.

EGG QUALITY

On egg quality, breeders are concerned mainly with optimum egg weights for local markets, good shell strength and internal quality factors such as albumen height and absence of inclusion such as blood spots. The Zimbabwean market places the highest demand on eggs that have an average weight of 60g or lower. Breeders therefore prefer strains that produce the largest proportion of eggs in this weight range.

Other important genetic traits considered are chick livability and hatchability which are both critical for reducing chick production costs. Table 3 gives a summary of progress in egg production traits in brown egg strains.

Table 3. Changes in key traits for brown egg strains 1981 to 1993

Strain

Years

Ending

Egg

Number

Egg Weight

(kg/henhoused)

Egg

Weight

(g)

FCR

(kg/kg)

Hisex

81-83

277

17.6

63.7

2.56

Brown

91-93

293

18.9

62.7

2.28

Lohmann

81-83

272

17.5

64.5

2.60

Brown

91-93

297

19.8

66.7

2.22

Source: Flock (1994).

BROILER BREEDING

Unlike in layer strains, some selections are done locally to improve productivity in broilers. The current targets for selection in broiler breeding and how they changed are given in Table 4.

Table 4. Targets for selection in broiler breeders

1960

1970

Targets for selection

1980

1990

Weight for age

Weight for age

Weight for age

Weight for age

Conformation

Conformation

Conformation

Conformation

Reproductive

Reproductive

Reproductive

Reproductive

performance

performance

performance

performance

Leg defects

Leg defects

Leg defects

Leg defects

 

Yield of parts

Yield of parts

Yield of parts

 

Livability

Livability

Livability

 

Feed conversion

Feed conversion

Feed conversion

 

ratio

ratio

ratio

Source: Barton (1994)

All the traits listed in Table 4 are determined between 5 and 6 weeks of age with the exception of reproductive performance which is measured over an entire laying cycle. Selection for reproductive traits is mainly applied to female line G.P's. They are selected to produce a fairly large number of eggs that hatch well and genetically they have good growth promoting characteristics. The other traits such as meat yield, FCR and weight for age are selected for in the male line G.P's. The male line G.P's typically have exceptionally heavy fleshing, good breast conformation, rapid growth rate and achieve good FCR. These traits have of course been improved at the expense of good egg production and fertility. The targets for selection in broiler breeders in Zimbabwe are primarily aimed at cost reduction and improving quality of broiler meat.

COST REDUCTION

Genetically improving liveweight gain, FCR, reducing mortality and reproductive performance will lead to a reduction in the cost of broiler meat production. It must also be noted that these improvements have given poultry meat a cost advantage over other meats.

QUALITY TRAITS

Selection here is for improved carcass conformation, absence of blisters, hockburn and lameness. These traits are really linked with growth rate and are considered at 5 - 6 week selections. Breeders also strive to keep their flocks free of vertically transmitted poultry and human pathogens such as mycoplasmas and salmonella.

In some faster growing strains it may be necessary to reduce growth rates genetically in order to reduce physiological disorders such as ascites or structural defects such as splayed legs. Some breeders achieve this by renewing stocks of female G.P's only and retaining the male line G.P's which would have adapted to local conditions.

THE VALUE OF 5 - 6 WEEK SELECTIONS

Selection for broiler traits in Zimbabwe are currently done at 5 - 6 weeks because the weight of G.P's at this age is highly correlated to the weight of broilers at the same age. As most of the selection targets are related to the male line, higher selection pressure is applied to this line. Table 5 gives a summary of genetic progress made in Cobb broilers.

Table 5. Genetic Progress in Broilers 1977-1993

Traits

1977

1985

1993

Liveweight (grammes)

     

28 days

720

1011

1204

42 days

1360

1793

2092

56 days

2068

2576

2978

FCR

1.6

1.6

1.51

Source: Cobb Breeding Company (unpublished).

THE FUTURE

The future of poultry breeding in Zimbabwe looks very promising, but there are a lot of non-genetic factors that need to be improved before we can fully utilise the genetic resources we have. In breeding operations, for example, introduction of separate sex feeding will enable better control of male body weight which is essential for maintaining good fertility levels.

At all levels of poultry breeding improvements can be made in feeds and feeding. Outbreaks of Newcastle Disease in 1994 decimated a lot of indigenous flocks which represent a vast genetic resource yet simple vaccination controls can prevent these outbreaks. Housing and management standards have also hampered full expression of genetic potential for all important traits. In open sided broiler sheds, for example, daytime temperatures can be as high as 25oc and drop to 5oc at night resulting in high mortality and poor growth rates.

Demands on primary breeders by markets in developed countries may result in some undesirable trait changes for our poultry producers. If the processed egg market, for example, starts demanding thinner shelled eggs, the resulting egg will probably not survive our local transport system. In broilers, developed countries may push for leaner carcasses which may be less acceptable to our local markets. It is hoped that primary breeders will continue to produce products that will fit into various world markets.

Information on genetic make-up and productivity in indigenous breeds is very scarce which makes it difficult to assess their genetic potential for meat and egg production. However, there is little doubt that even the absence of genetic improvement, better feeding and housing will improve productivity in the indigenous flocks.

REFERENCES

Barton, N.F. (1994) Proc. 9th European Poultry Conference, Glasgow, U.K.
C. S. 0. (1994) Central Statistics Office, Zimbabwe Government. Flock D. (1994) Proc. 9th European Poultry Conference, Glasgow, U.K.

Previous PageTop Of PageNext Page