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Friday, 21 August 2015 11:00

Lamb productivity still depends on basics

Written by 
Paul Kenyon Paul Kenyon

Achieving high lamb survival and growth rates to weaning is about matching ewes to their correct lambing paddock.  

Using basic principles and knowledge farmers have of their farm, they can aim to maximise the performance of their flock to weaning.  This is very important in a year in which covers are low and many ewes are going into lambing in poor body condition.  

Most New Zealand farmers know whether their ewes are singleton or multiple bearing, based on pregnancy scanning. Further, going into set stocking they know which paddocks have the highest covers and traditionally which paddocks grow the most grass in early spring.  They also hopefully know which paddocks have in the past resulted in the highest lamb survival, based on previous pregnancy scanning and tailing data. Farmers could also identify ewes in very poor condition when giving pre-lamb vaccinations, if they have not identified these ewes earlier.   Using the above information farmers can make informed decisions.

Ewe intakes are not restricted at lambing, and in lactation, when covers don’t fall below 1200kgDM/ha (4cm sward height) further intakes do not increase at very high covers.  The further covers fall below 1200kgDM/ha the poorer ewe and lamb performance will be.  

Singleton bearing ewes and ewes with a condition score of 3.0 or above have some ability to buffer.  Therefore these ewes are the ones that can be set stocked on paddocks with lower covers while multiple bearing ewes, especially poor condition ewes, should be prioritised to paddocks with higher covers and into those paddocks that grow more grass.   Stocking rates with multiples are also important to ensure appropriate covers are maintained.  

There will be paddocks that have traditionally resulted in higher lamb survival, whether that’s due to shelter, slope or some other factor.  These are the paddocks that multiples, especially triplets, should be set stocked on.  

Some farmers are also in the position to have crops like lucerne and herb mixes such as plantain and/or chicory and clovers to lamb on.  Studies funded by Beef + Lamb NZ  have shown that these can improve ewe and lamb performance to weaning with singleton and multiple rearing mature ewes and singleton rearing hoggets.  However, cover on these crops should not be grazed too low if the aim is to maximise animal performance and longevity of the crops.   

Stocking rates are also important as ewes need to remain on these crops in lactation otherwise adverse health effects have been reported. In some environments these crops may not be ready at lambing.  

Studies have shown that ewes can be placed on herb clover mixes that contain a high level of clover post tailing and performance to weaning is also increased.   Recently studies at Massey University have also shown that lambs at 19kg can be weaned early onto herb clover mixes and their growth to a normal weaning age was greater than those left on their dam under unrestricted ryegrass white clover feeding conditions.  

Studies funded by BLNZ this spring at Massey University will include: 1) early weaning of lambs on herb clover mixes and lucerne under differing environments; 2) the impact of lambing twin bearing hoggets on herb clover and lucerne mixes, and; 3) can lambing singleton bearing ewes on herb clove mixes allow for early slaughter dates.  

The group is also examining the impact of singleton ewe stocking rate and is re-examining the role of milk in early lamb growth with the aim of designing strategies to allow for early weaning.   

• Professor Paul Kenyon is a sheep specialist who heads Massey University’s Institute of Veterinary, Animal, and Biomedical Sciences. 

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