The better a lamb is fed the quicker it grows. Supplementary feeding is one approach, it depends on:
• Grass quality
• Lamb quality
• Lamb growth potential
Autumn grass quality depends on how it is managed through the summer. Also the intended market date for your lambs has a big influence on the quantity of supplementary feeding that should be given. Cattle grazed land will be high quality as lambs will graze the fresh grass around cattle dung pats. Re-seeded ground will have the best ME and protein values helping store lambs growth potential and weight gain to be maximised. Grass supply falls from 50 kg/dm/ha/day in mid-September to around 5-10/kg/dm/ha/day in September.
With favourable weather conditions lambs can achieve 1kg of weight gain a week. If lambs are not within 5 – 7 kg f finishing weight at the start of the intended finishing period there is no justification in intensive feeding until the lamb has completed its maximum growth period.
The key to effective supplementary feeding is to feed a low protein, high ME feed such as cereal grain or sugar beet pulp while grass is still of high quality. This must be fed at a level that does not interfere with grass digestibility, typically 0.25 kg/day is fine and up to 0.45 kg/day is the limit for cereal intake. Above this the supplement starts to substitute for grass in the diet. Lambs fed in a group from troughs tend to start eating at the same time and therefore finish together. Expected live weight gains for every 6-8 kg of supplement fed will give a live weight gain of 1 kg. The alternative is the low labour ad lib feed from hoppers.
Typical compounds are 16 % cp and will adequately finish lambs. Unless there are trace elements deficiencies on the ground there is no benefit in extra minerals at grass. Lambs which are supplementary fed must always have access to clean drinking water.
Selection of lambs at slaughter is critical so that lambs are not fed into unsuitable weights/ fat class therefore increasing the cost of the supplementary feeding and decreasing the profit margin.