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Wednesday, 08 October 2008 12:39

Variety gives boost to lamb growth

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Ever eaten Weetbix for breakfast, lunch and dinner? Maybe lambs face a similar dilemma when they get the same paddock of grass served up three times a day.

Lincoln University’s Alastair Nicol has been putting lamb diets to the test in some eight week grazing trials with five different sward mixes to discover what provides the best diet for growth.

Dr Nicol says there is no one pasture that is best for all situations, though short-term studies show lambs prefer to eat 70 per cent clover and 30 per cent grass.

“Sometimes you want a good hard-wearing, persistent grass-dominant sward. Other times a short-term finishing pasture with a high-legume content is required,” he says.

As part of the three-year research programme funded by WoolPro, he found that lambs grazing on swards with 40 per cent clover strips grew 14 per cent faster than those with no extra clover. However, there was little difference in lamb growth on pure lucerne pastures and lucerne with 20 and 40 per cent grass.

“Farmers using lucerne for finishing lambs need not worry too much about these paddocks being invaded by grass - it won’t affect growth rates.”

He says farmers will know if they’ve achieved the ‘ideal pasture’, because its composition will be only slightly different after grazing than it was before. This indicates the lambs didn’t have to make choices or select out the more nutritious parts as it was just what they wanted. It will also regenerate quickly to a good pre-grazing condition.

A lamb’s growth can be hindered if it has to spend time selectively grazing, a fact Dr Nicol says is hard to test in the field. “Young animals generally select a higher quality diet than older ones, and pregnant ewes and lambs with parasites prefer more clover in their diet.”

He says farmers can make extra clover available in paddocks grazed by lambs by spraying about a third of the paddock to remove or suppress grass.

The next stage of the research will ‘count the cost’ of preparing swards with extra clover, compared with the dollar benefits.