EWE UDDER ASSESSMENTS DRIVE LAMB SURVIVAL
Weaning percentage is one of the most important drivers of profitability for sheep breeders. Not only does increasing the number of lambs reared lead to increased sales, but it also allows greater selection pressure to be applied when selecting replacements. This will increase the rate of genetic improvement in the breeding flock. Recent industry extension efforts have targeted improving management, particularly reproductive management, through nutrition, stocking density and animal health. However, one of the most important elements and often overlooked aspect, is the ewe herself. Either a poor maternal instinct or faulty udder, can significantly reduce lamb survivability. Improved management has little impact on these factors.
Traditionally, culling/selecting on reproductive performance has relied solely on removing ewes scanned as dry during early pregnancy. However, this only targets a small proportion of factors involved in reproductive loss, i.e. those ewes who fail to conceive or suffer from early embryo loss. After 4-5 years of scanning and removing dry ewes, there is very little additional genetic improvement to be made in a conventionally managed enterprise.
Dr Gordon Refshauge, Senior Research Scientist at NSW DPIRD, has been studying reproductive performance in sheep flocks. He has implemented best management practices on the Cowra DPIRD Research Station flock of 1,000 dual purpose Merino ewes. In 2024, the research flock achieved a marking rate of 133% from ewes joined, continuing the trend of high marking rates from previous seasons. These recent reproductive achievements have shown what is achievable when management and genetics are optimised.
Dr Refshauge states that the first priority for increasing reproductive rates in a sheep flock, is to focus on increasing rearing ability, before attempting to increase the rate of multiple births. Simply, if a ewe is not capable of raising multiple lambs, there is no point trying to breed for multiple births. According to Dr Refshauge, assessing udder characteristics is the most important trait to focus on when improving rearing ability.
Udder assessments conducted during lamb marking can establish whether the ewe has:
Successfully raised at least one lamb – udder is warm, enlarged, and full of milk.
Lambed and lost - udder has been lactating, but lamb(s) have died
Did not give birth to a live lamb – ewe scanned in lamb but no udder development present (foetus aborted post scanning but before udder development)
Udder damage and deformities can impair milk production and the ability for the lamb to suckle, contributing to the number of ewes which fail to rear their lambs. These issues include:
Mastitis and lumps
Bottle teats
Blind teats – Blocked teat canals, mostly due to shearing cuts
Secondary conformation characteristics which can affect milk production include:
Small udder – The udder doesn’t have the milking capacity to support multiple lambs
Large or low udder – udder is predisposed to other issues, such as Mastitis, bottle teats
In flocks which have not been previously assessed for udder conformation, 1-2 seasons of culling ewes with unsound udders, will lead to significant gains in the rearing ability of the flock. Subsequent assessments should lead to a lower culling rate, as the assessment will only need to identify changes which have occurred in the previous season.
The main impediment to udder assessments is that they should be conducted at lamb marking, to achieve the greatest accuracy. As most producers use lamb marking contractors, who are attempting to mark >1,000 lambs per day, the logistics of marking is often very complicated in itself, let alone adding another task which adds significantly to the workload. Additionally, assessments are required to be done in a drenching race or sheep handler, therefore portable yards or small marking yards are less suitable.
For smaller growers, lamb marking themselves or on a co-operative basis with neighbouring growers at a slower pace, lamb marking may be a suitable time to udder score.
Larger producers will still need to use marking contractors; however, the contractor may be able to supply the labour to conduct the assessment or prioritise key age groups to assess, such as maidens and the oldest age groups being retained. Ideally, the contractor could bring less labour and mark at a slower rate.
Dr. Refshauge asserts that with optimal management practices, plus genetic improvements aimed at enhancing maternal capabilities and increasing litter size, commercial Merino breeders situated in medium-to-high rainfall regions, should be capable of achieving average weaning rates of approximately 120% of ewes joined. The results achieved at the Cowra Research Station demonstrate that this increase in reproductive rate is very achievable.
Other than an increase in time and potentially better nutrition, both optimal management and more balanced genetics focused on improved reproductive efficiency, can lead to significant productivity increases which boost profitability, for little additional cost. An increased weaning rate of 20-30% from the current average of 90-100% in Merino systems, is a massive improvement. Rarely is it possible to achieve a productivity increase of this magnitude within a single enterprise.
