printBy Tiffany Bennett, PIRSA Rural Solutions SA
Whilst some SA producers are experiencing ongoing impacts of the drought, it is still important to consider future recovery strategies, particularly given the likelihood of low available sheep numbers and the potential high cost of restockers.
Retaining older ewes that would normally be culled may be a good strategy to rebuild flocks that have been reduced due to drought.
Most producers cull ewes around five or six years of age. Research undertaken in 2012 by NSW Department of Primary Industries, supported by Sheep CRC, has shown that some older ewes can outperform younger ewes and overall ewe production can be higher in older ewes up to seven years of age.
Identification and selection of productive older ewes to remain in the breeding flock should be based on a high reproductive potential. Actively managing the body condition of older ewes during pregnancy to industry targets for twin bearing ewes (as litter size tends to increase with age) will allow the older ewes to realise their potential.
The key body condition targets for productive older ewes are: Weaning –2.7; Joining –3.3; Early to mid-pregnancy – 3.0; Late pregnancy – 3.3; Lambing - 3.3; Lactation - 3.0
Adequate nutrition of older ewes is vital during the later stages of pregnancy. Twin bearing ewes are predisposed to developing metabolic disorders late in pregnancy (commonly three weeks prior to lambing). This can result in high rates of ewe mortality if ewe nutrition is inadequate at this time.
Survival rates of progeny, particularly twins which will be more common among the older ewes, can fall to below 50% if the ewes lose condition during late pregnancy. It is worth offering additional feed (pasture or supplements) to older ewes from mid-pregnancy onwards to allow them to improve condition as they approach lambing.
Pasture benchmarks recommended for twin bearing ewes during pregnancy should be used for productive older ewes. If these pasture targets are not able to be met, older ewes should be appropriately supplemented with a balanced ration particularly in late pregnancy to avoid pregnancy toxaemia.
Older ewes to be kept in the flock should also be selected on the soundness of their teeth, udder and feet. Wool production quality and any fleece or structural faults should also be considered.
As a sheep ages teeth will start to wear, spread and eventually break off. Sheep that become broken mouthed are not as efficient at grazing. These ewes can still perform under good nutritional management but are at more risk of not performing.
Udder abnormalities increase with the age of the ewe and identifying abnormalities should be used as a selection criteria when retaining older ewes.
Ewes with unsound udders regardless of the abnormality are less likely to rear a lamb as effectively as those ewes with sound udders.
Udder abnormalities may include abnormally shaped teats or udders, teat damage as a result of shearing, udder damage or the loss of half the udder as a result of mastitis, a lumpy texture to the udder.
Ewes with unsound udders have reduced milk yield leading to lower lamb growth rates and lower lamb survival.
The condition of a ewe’s feet and legs will impact on her ability to graze throughout a paddock and seek water. Ewes should not be lame or limping and hooves should be free of defects such as cracks or abnormal or excessive hoof growth.
Clean fleece weight can decline in as ewes become older. This is a result of the number of wool producing follicles decreasing, with ewes peaking at 3-4 years of age, and then, decreasing by up to 20% up to eight years of age.
Identifying the best performing ewes is helpful if retaining older ewes to ensure you are investing in your most productive ewes.
Electronic identification can provide an opportunity to capture lifetime scanning and wet/dry data to determine which ewes are performing reproductively. Twice dry ewes can be culled to ensure the older ewes you are retaining are the most productive.
For further details contact your local Livestock Consultant (www.salivestockconsultants.com.au).
(Information for this article was sourced from AWI)