Impacts of Body Condition Score on Reproductive Success

Key Points

  • Condition scoring management tool to assess nutritional status of flock
  • Ewes in CS 3+ at joining, increase reproductive success
  • Preferential feed ewes less than CS 2.5 after weaning
  • Increased lamb birth weights of twins, from ewes in CS greater than 3

NUTRITION and body condition score have the most influence on reproductive success with secondary impacts from genetics, breed, time of year, and length of joining period. Physically feeling the back bone of the ewe is the only way of assessing body condition and this will allow you to determine an average nutritional status of your flock. Condition scoring your flock, conducted at key times during handling, is an effective management tool which will maximise reproductive success.

Condition scoring is a quick and easy assessment of the body reserves of all your sheep; and in ewes can be used as a management tool to help reach condition targets for mating and lambing, or can be used to monitor body condition during pregnancy and lactation. By assessing body condition, nutritional requirements can be altered to ensure feed requirements are being met or to give an indication if you are overfeeding.

Condition scoring is an assessment of the fat and muscle covering the backbone and short ribs (loin area) and is best conducted in a race, when the animal is standing and is relaxed. It can be conducted during other husbandry activities so shouldn’t be seen to be an extra job. Putting your hand over your sheep will provide a more accurate assessment of condition, than just looking at them through the ute window. For further information on how to condition score, go to the Lifetimewool website, and view the "How to condition score" YouTube video.

The Condition Score (CS) of the ewe at the time of joining has the largest impact on reproductive success. Research conducted by Lifetime Ewe, suggests that the higher the condition score at joining, the higher the conception rate. Ewes in CS 3+ at the time of joining will have a greater chance of conceiving due to the rate of ovulation being strongly correlated with body condition of the ewe at joining. An increase in production can be attributed to a lesser number of drys within the mob and more ewes conceiving twins.

To enable the ewe to reach a CS of at least 3 at joining, preparation for joining needs to occur as soon as lambs are weaned. At weaning, condition scoring can be used to separate ewes in to management groups and allocate better pasture resources to ewes with lower condition scores (below 2.5). This is most cost effective way of increasing body condition, though if inadequate pasture or stubble feed is not available, then supplementary feeding will need to occur. Skinny ewes are likely to be the most productive, often loosing condition through raising twins or producing large quantities of milk.

Maintaining body condition in ewes from joining to lambing increases lamb survival. The optimum birth weight of a lamb to maximise survival is between 4.5 and 5.5 kg. A decrease in ewe body condition during pregnancy can influence the placental development and reduce lamb birth weight by 0.4 to 0.5 kg in both single and twin lambs. Ideally, single bearing ewes should be in CS 2.8 to 3 and twin bearing ewes in CS 3 to 3.3 to optimise lamb birth weights and survival.

Ewes in these CS ranges produce adequate quantities of milk to support lamb development. Poor ewe body condition at lambing can have a detrimental impact on maternal behaviour, with the ewe often leaving the birth site to feed rather than nuture, resulting in lamb loss. Ewes in CS 4 and above may encounter lambing difficulties resulting in the loss of the lamb and even the ewe during the birthing process.

Condition scoring is an easy and effective management tool to monitor and maintain body condition score of ewes throughout their production cycle. It enables you to make management decisions to ensure feed resources are allocated accordingly and reproduction success is maximised.

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