Identifying Lamb Losses

Summary

The losses of lambs were much higher than the 15 percent expected by participating producers. The number of lambs unaccounted for was high considering the terrain and supervision of the lambing paddocks. Some ewes may have been incorrectly diagnosed as pregnant, or the test results incorrectly recorded. Some lambs may have escaped into adjacent paddocks of ewes and lambs. The most probable reason agreed by the participants was that lambs were taken by foxes. Some of these lambs may already have died of other causes before being taken by foxes. The number of lambs found scavenged, together with the number of lambs dead from predation indicates that foxes were active among these mobs.

The high loss of lambs as a result of exposure is not surprising given the adverse weather conditions. The producer with the highest losses was at the peak of lambing during the worst period of rain and wind. The paddocks selected to graze the trial mobs were based on proximity to the woolshed rather than the amount of shelter provided. Deaths as a result of dystocia were also significant. The two year old ewes had a higher loss, but the one mob of ewe hoggets lambing at 12 months old recorded only six dystocia deaths from the 495 lambs born. Many of these losses are probably the result of ewes with a small pelvis. This may be genetic, or the result of low growth rates as ewe weaners, which could compromise skeletal development. Starvation losses were also high. This occurred in all but two of the trial mobs. There appears to be little difference between the mobs with single lambs and those with twins. The mothering ability of ewes needs to be improved so they do not desert lambs. The selection of ewe replacements from ewe lambs that have been successfully reared as twins needs to be implemented to implant this behaviour in the ewe flock.