In this article, CAFRE’s Nigel Gould discusses lamb performance, drafting and blue-fly control.
Take advantage of the current positive lamb prices and draft lambs as they become fit. Early in the season, young lambs can have adequate fat cover for slaughter from as low as 40 kg. This will increase to 45 kg and higher later in the season.
Bear in mind, the upper carcase weight limits factories impose and aim to reduce the number of lambs going overweight and out-of-spec.
Kill out percentages can vary significantly – ranging from 50% for well conformed, young, creep-fed lambs early in the season to 42-44% for poorer conformation lambs finished off grass-only as the season progresses.
Monitor lamb performance to avoid lambs going overweight and identify any performance issues.
Target average pre-weaning daily live weight gain for lambs on a grass-only diet of 270 g and 320 g for twin and single lambs, respectively.
If performance is below these targets, consider the possible causes:
- Ewe milk yield;
- Grass yield/quality;
- Mineral deficiency;
- Possible worm burdens.
In the case of the latter, faecal egg tests are useful for identifying worm burdens during the summer and indicate a need to treat. This approach should reduce anthelmintic requirement and the incidence of resistance.
To maintain quality in subsequent rotations, post-grazing sward height should ideally be 3.5-4 cm where possible.
However, grazing below 5-6 cm means that poorer quality material is being consumed.
Ideally, lambs should be moved on at the higher sward height and dry ewes, for example, used to graze down to 3.5-4 cm.
Although this requires extra management, it could result in additional weight gain, which otherwise would only be achieved by offering creep feed.
Warm, damp conditions provide an ideal environment for blue-fly activity and maggot strike.
Pour-ons, dipping and showering are the most popular control options. However, pay close attention to withdrawal periods as these can be quite long for certain products, making them unsuitable for lambs nearing slaughter.
Darkening of the wool in the affected area, with visible signs of distress from the itching and pain, followed by wool loss, are all characteristic signs. Timely identification and treatment with an appropriate product usually results in a successful outcome.
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