In the competitive agricultural landscape, the intensive management of your sheep production system may mean the difference between simply surviving and earning money. The following series of articles are based on the Sheep Facilities Manual of the ARC Institute for Agricultural Engineering in South Africa. In this issue we discuss the choice of breed depending on your lambing system.

Existing production systems for mutton production in Southern Africa can be divided into two main groups, namely extensive and intensive systems. In an extensive production system sheep live off the veld. Structures for this type of production therefore consist of overnight facilities and a handling complex.

An intensive sheep production system usually refers to a closed system, or a system which exists in a feeding pen or a production system from pastures or a combination thereof. The final choice between the systems will largely depend on the owner and will therefore depend on preference, management level, existing facilities, and the area where he is farming. With intensive production systems, there are two types of lambing seasons, namely the in-phase and accelerated lambing season.

In-phase lambing season

In this system each ewe lambs only once a year. The group is, however, divided into two, so that the ewes from different groups will lamb at different times of the year. Risks are diminished this way, and lambing pens and feeding pens can be used more effectively. An existing system can be utilised to its maximum by extending the size of the herd.

Accelerated lambing season

The accelerated lambing season system is beginning to become a possibility as the production system is refined. Costs and risks of the system are usually high, but the potential in income is also higher. In this system, sheep breeds with a long breeding season is used. The lambs are weaned early (6 to 8 weeks or on approximately 20 kg) and the ewes are tupped again immediately. Three lamb harvests in two years are obtained this way. A typical lay-out of an intensive production system for both in-phase and accelerated lambing season systems shown in figure 1.

A number of variations can occur, depending on the how planted grazing is integrated in the system and the facilities. A schematic lay-out of a system, which uses plenty of planted grazing and where the ewes lamb on the grazing, is shown in Figure 2. This lay-out could be used where ewes lamb in the spring and/or autumn, but will be dependent on the climate of the relevant region. Regions with a reasonably dry, warm climate will be suitable for this type of lay-out.

Choice of breed

Under the item, accelerated lambing season production system, mention was made of breeds with a long breeding season. The specific breed to be used will therefore also have an influence on the system to be used. The objective of any intensive production system is maximising profit. It is therefor important that the choice of a breed will also be made with maximised profits in mind. The term, profit maximising, refers to striving towards maximum income per ewe per year, including maximum mutton and/or wool production per year. Factors such as a personal preference for a certain breed are therefore consequintly excluded from this discussion.

In line with the profit maximising objective, the following factors pertaining to choice of breed are important:

• Adaptation of a breed in the specific region
• A long breeding season
• An acceptable carcass
• Growth potential
• High reproduction tempo
• Good maternal characteristics

If a certain herd size is accepted, the above factors can be evaluated according to three basic factors for the increase of mutton production, namely:

• Herd structure
• Age structure
• Weaning percentage

Herd structure

The herd structure pertains to the percentage of breeding ewes, she-lambs, young ewes and wethers. An analysis of the herd structure showed that an increase in breeding ewes has a very important influence on the future mutton production of a herd. Factors such as marketing age, mating age and number of breeding seasons per year – which are directly dependent on the breed – determine the percentage of breeding ewes in the herd. The greatest percentage breeding ewes in the herd – and consequently the highest mutton production – is possible with breeds such as mutton, mutton/wool and fur sheep.

Age structure

Mutton production consists of the number of lambs and number of ewes marketed annually. An extension of the period that breeding ewes can be used in the herd means a reduction in the replacement tempo, that is the number of lambs to be retained in the herd per year to replace productive ewes. A reduction in the replacement tempo will inevitably ensure an increase in the number of marketable lambs per year, and hence an increase in income.

Factors which influence the production period of breeding ewes are:

• The number of lambs weaned, increasing to the ewe’s age of 5 years, after which it decreases as the ewe gets older;
• The survival age of the ewes remains constant to the age of 7 years after which it decreases.

An early mating age and longevity of ewes are therefore very important factors to consider when choosing a breed.

Weaning percentage

The weaning percentage directly determines the mutton production and can be increased by:

• An increase in the lamb percentage: That is the number of lambs born per mated ewe.
• An increase in fecundity: Under fecundity (fertility) we understand the number of lambs born per ewe. The occurrence of multiple births therefore has a positive influence on the meat production. There is, however, a notable weaker growth with multiples compared to single lambs. An increase in fertility must therefore be coupled with selection for better growth potential to be significant. Fecundity can be increased by selection within a breed or by crossbreeding. An improvement in the covering: That is the percentage ewes lambed per ewes mated. The fertility of the ewes and rams are very important here.
• An improvement in survival: That is the number of lambs born per number of lambs weaned. As far as the choice of a breed is concerned, the maternal characteristics are important here.
• An increase in lambing frequencies: That is that higher coverings be done, three times in every two years instead of the normal annual lambing. The above factors determine the number of marketable lambs per annum. It is, however, also important to look at the factors that influence the total mass of lamb produced per year.

These factors are as follows:

• Milk production of the ewes: This feature largely determines the preweaning lamb growth and is especially important with a high fecundity characteristic.
• Growth potential of the lambs: The growth potential of the lambs is to an extent influenced by the heredity of this feature and varies from breed to breed.
• The “type” and carcass quality: has an anticipatory value to predict the percentage fat and percentage good meat cuts of a carcass.

The variation of the factors influencing the choice of a breed is sometimes greater within a breed than between different breeds. This means that no universal breed can be recommended for intensive systems.

Fundamentally, factors such as adaptation potential, fast growth and longevity of ewes determine the choice of the breed. If the current wool price is considered, a further determining factor, namely the wool production potential, is also important. Table 1 below quantifies some of the most important differences between the various breeds.

We thank the ARC-Institute for Agricultural Engineering in South Africa for the use of their Sheep Facilities Manual. Next time we shall look at the design of an intensive production system.