Last update: March 29, 2012 10:46:33 AM E-mail Print

 

Why are Afrinos not shown?

JJ Olivier 

 

The Afrino is South Africa's youngest sheep breed and therefore has the advantage that it can learn from the experience of older breeds. Problems can be avoided and aspects providing favourable results can be applied.

The majority of sheep breeds participate in shows and regard it as very good opportunities for breed promotion. Undoubtedly, the Afrino will derive much benefit from showing in that greater awareness of the breed will be created, resulting in an increase in numbers. It has also been experienced at shows, however, that only the good-looking, well-treated animals catch the eye and not necessarily outstanding breeding material. Breeders also utilise shows to advertise their studs and the breeding animals are cared for very well. In order to produce visually attractive animals, they are reared under artificial conditions, which frequently differ significantly from the natural environment. This practice has had the effect that the breeding ideals of the stud breeder and the commercial breeder are not the same. The stud breeder wants to breed show animals to become well known, thus achieving better prices for commercial rams. The commercial farmer is interested in a ram that, for instance, will produce fast-growing, marketable lambs. Commercial rams that are to serve ewes under natural conditions are being reared under artificial conditions, giving rise to problems with adaptability. One can hardly expect to breed a hardy, extensive sheep in artificial surroundings where walking distance is limited, concentrates are freely available and wind and sun have no influence.

The external appearance of an animal (its phenotype) is the sum of its genotype (inherent genetic traits), the environment and the inter-action between the latter two aspects. According to Hammond (1947), an animal requires optimum conditions in order to develop its full genetic potential.

Animals that develop best in an optimum environment should be selected as breeding animals, according to Hammond (1947). A number of research workers have questioned Hammond's recommendation and Wilson (1974) has summarised various researchers' results on the best environment in which breeding animals should be selected. His recommendation was that breeding, animals should be selected in the same environment in which they are to produce and reproduce. In other words, the best ram in a very good environment will not necessarily be the best in a less favourable environment. According to Dunlop & Young (1966), who have worked with Merino's in Australia, the environment where selection takes place becomes more important as environmental differences increase.

In Australia, Hereford and Shorthorn cattle have been selected for post-weaning growth at 24 months since 1966. A control group has also been maintained and here no selection has taken place (Frisch, 1981). In 1976, bulls of the selection and control groups were compared. The average corrected weaning mass of the bulls in the selection group was 10% higher than that of the bulls in the control group. The average fasting mass of the bulls selected for the environmental study was 119,3 kg for the selection group bulls and 99,3 kg for the control group bulls. The selection group bulls were, therefore approximately 20% heavier than the control group bulls in a tropical (natural) environment.

After dipping and dosing, the same group of bulls were placed in feeding pens and their growth rates were compared. At the completion of the growth test, the control group bulls showed a 7% faster growth rate than the selection group bulls and they weighed significantly more. According to Frisch (1981) the differences were the result of a larger feed-intake by the control bulls while no difference in feed conversion efficiency occurred between the two lines. Prior to commencement of the experiment, however, the selection group bulls were heavier and their growth rates faster than those of the control group bulls. According to Frisch (1981) this inconstituency can be ascribed to the fact that pre-weaning mass gain was a reflection of the animal's resistance to stress factors rather than its inherent growth potential.

The same bulls have further been tested in varying temperatures, in the absence or presence of external parasites and other environmental inhibiting factors. For example, the growth rate of the two groups of bulls has been tested after they had been dosed against internal parasites. In this case, the control group bulls grew 7% faster than the selection group bulls. The growth rates of the bulls were subsequently measured without having been dosed against internal parasites. In this trial, however, the selection group bulls grew 27% faster than the control group.

On the strength of this trial, Frisch arrived at the following conclusions:

(i) Sustained selection in an unfavourable environment resulted in the elimination of genes that are sensitive to unfavourable conditions. However, should selection have taken place in a favourable environment, these genes would have been preserved.

(ii) The probable result of selection for growth in different environments was that different 'types' were being selected. For example, in a favourable environment the animals with the poorer adaptability, but higher growth potential, were superior, while in an unfavourable environment the more adaptable animals with genetically inferior growth potential flourished.

(iii) Selection in fluctuating environments will, therefore, alternatively be for growth rate or resistance against environmental inhibiting factors.

 

These results once again support Wilson's (1974) recommendations that breeding animals must be selected in the environment in which they are to produce and reproduce. However, be careful not to view the environment too literally. According to Dunlop & Young (1966), the environmental differences among various regions, such as the South Western Districts and the Karoo, are too negligible to be of any real significance. The most important differences occur where the environmental influences are being eliminated, for instance ram stables, blankets, ad lib concentrate rations, etc.

Shows are and will remain the venue that can afford a breed the best opportunity to advertise itself - and the Afrino will have to advertise itself. The main reason why competition among members at shows is not permitted is to avoid the problems of breeding 'artificial animals'. The Afrino must remain a well-adapted, hardy breed for extensive conditions and not a fancy breed.

 

LITERATURE:

Dunlop, A.A. & Young, 5.5. Y., 1966. Interaction between heredity and environment in the Australian Merino. Ast. J. Agric. Res. 17, 227.

Frisch, J.E., 1981. Changes occurring in cattle as a consequence of selection for growth rate in a stressful environment. J. Agric. Sci., Comb. 96, 23-38.

Hammond, J., 1947. Animal breeding in relation to nutrition and environmental conditions Bioi. Rev. 22, 195.

Wilson, S.P., 1974. Genotype by environmental interaction in the context of Animal Breeding. 1st World Congress on Genetics applied to livestock production, 7-11 Oct. 1974. Vol. 1, 393. Editorial Garsi, Spain.

 

Published

Afrino Manual 2