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Maximising lamb growth rates through pasture quality and quantity

Thursday, 24 March 2005
Tectra's Otago Regional Manager, Robert Pattison investigates the effect of pasture quality on lamb growth rates.

Robert has looked at pasture quantity and quality as well as weaning. Maximising lamb growth rates after weaning is important because it allows lambs to be drafted for slaughter as early as possible.

High quality pasture is paramount for maximum growth rates. Ideally pastures should be clover-dominant and grasses should be mainly new green leaf with few stems or dead leaf material present. Such pastures have high protein and ME levels, which quantifies digestibility and metabolisable energy, the major determinant of lamb growth. 

Tectra's Otago Regional Manager, Robert Pattison

According to Robert quality pasture must be teamed with adequate quantity.

"If insufficient pasture is offered - no matter how good it is - lamb growth rates will be sub-optimum. Conversely, if feed quality is low it won't matter how much is offered as lambs will only gain weight if ME values are above a certain rate."

Mechanical topping can be useful for maintaining pasture quality and silage or hay aftermath is also ideal for weaned lambs. As summer advances pasture quality will deteriorate. Forage crops such as chicory, red clover, trefoil, sulla or summer brassicas will provide plenty of high quality feed to keep lambs growing at near maximum potential.

Weaning is also an important factor in maximising growth rates. There is no set time for when to wean as each property will be different. Generally weaning should be considered when lambs begin to compete with their mothers for feed. This is also variable but will usually occur when the average pasture height falls below 3 cm.

If feed is not limiting lambs can be successfully weaned at about 10-12 weeks of age when ewe production has declined. 

Weaning paddocks should be prepared in advance for the lambs. They may have been grazed by the ewes and lambs or with cattle. Cattle grazers can reduce sheep parasite levels on the pasture.

Robert believes a key management strategy is to keep fresh paddocks ahead of the lambs to ensure maximum growth rates continue. In spring a spell of 2-3 weeks is usually sufficient to have a good fresh, leafy sward.

"The lambs are the priority of the mob at this time of the year - use the ewes to clean up behind them."