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The importance of measuring birth weight and lambing ease

Taking time to record lambing ease and lamb birthweights may not seem the highest priority in a busy lambing shed, but both can play a vital role in the genetic progress of the breed, explains Signet breeding consultant Sion Parry.

In sheep production systems, optimising the number of live lambs born is a key component of flock performance and profitability. Two major determinants of lamb mortality during the lambing period are the ease with which lambs are born (lambing ease) and lamb birth weight.

Low birth weight lambs experience higher levels of postnatal mortality, due to problems associated with low milk intake and hypothermia.  Conversely lambs with high birth weights are associated with lambing difficulties (dystocia) which can lead to the death of the lamb, the ewe or both.

Both birth weight and lambing ease are influenced by environmental factors and genetic ones. The genetic elements can be influenced through selective breeding and EBVs are available for both lambing ease and birth weight.

However, for these tools to be useful measurements must be obtained. Fortunately, birth weight is a simple weight measurement taken around the time of birth (usually by placing each lamb in a bucket suspended from a spring balance) and lambing ease is a simple classification system based on a sliding scale from one to six as in the table below.

Importantly commercial buyers want rams whose progeny are lively at birth and are born easily, selecting for optimal birth weight and lambing ease can have a significant impact on both of these traits.

While measuring both birth weight and lambing ease may seem a chore, submitting this important data when inputting lambing information is a vital part of the Texel breed development programme.

Lambing Ease Scores

Score   Lambing Ease
1           No assistance
2           Slight assistance by hand
3           Severe assistance
4           Non-surgical vet assistance
5           Vet assistance, surgery required
6           Elective caesarean

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