In order to achieve maximum economic returns, the finished-lamb producer needs to plan his production system to meet the requirements of his chosen market. These requirements are now becoming more specific as consumer demands for a quality product increase and new markets (e.g. Europe) become available. With the diversity of genetic and environmental backgrounds of lambs destined for slaughter, together with the seasonality of breeding in sheep, it is not surprising that a range of finishing systems exists. This paper highlights recent developments in the nutrition of the finishing lamb and examines their potential.
In the early lambing flock, where fast growth rates are essential, lambs are often weaned when they are 4 to 6 weeks old. Similarly, in flocks lambing more than once per year, early weaning is necessary to allow the ewe to recover body condition before the next mating. Cereals are rich sources of energy and highly palatable to young lambs. Their rapid rate of fermentation in the rumen makes intensive finishing on cereal-based diets a relatively easy process, with growth rates of 350 to 400 g/day allowing lambs to reach slaughter weight at 12 to 14 weeks of age. To avoid the production of soft fat, which arises from high levels of propionic acid in the rumen, cereals should be offered as whole grains. Considerable benefits in terms of growth rate may be achieved by the inclusion of high quality protein sources of low rumen degradability, such as fish meal, in the diet.
The use of fodder crops grazed in situ for finishing store lambs has declined in recent years with the result that interest in indoor finishing systems has increased. These systems based on concentrate foods result in rapid growth rates. Alternatively, silage-based diets with appropriate supplements may be used to produce more modest growth rates, allowing lambs to be taken to heavier weights. Maintenance feeding during the store period has a major influence on the response of these lambs to improved nutrition, particularly to protein of low rumen degradability. Environmental limitations such as shortening daylength may also be an important consideration.
Lamb carcass quality is becoming increasingly important in market specifications and the ability of lambs to produce more lean and less fat has been demonstrated in experiments involving pharmacological manipulation. While these techniques may not be acceptable to the consumer, the potential to enhance carcass composition by dietary means clearly still exists.