Profiling weaners by their liveweight could help producers significantly improve the survival rates of young Merino sheep, NSW Department of Primary Industries research has found.

"Weaning weight has a significant influence on post-weaning growth and survival, with the first four to six weeks after weaning critically important for subsequent productivity," Orange-based research scientist Sue Hatcher said.

"While the lightest cohort of weaners within a mob clearly requires targeted feeding for survival, another sub-group of weaners may also be at high risk," she said.

Ms Hatcher said observations of post-weaning growth in the first four to eight weeks indicate the existence of four sub-groups that wean:

1. At or above the mob average and then have strong positive growth
2. Below the average and have strong compensatory growth
3. At or above the average and then have negative growth
4. Below average and never catch-up

"There were differences in death rates between the four liveweight profile groups," Ms Hatcher said.

"Those weaners classified into groups three and four were nearly five times more likely to die in both the Central Tablelands and Yass Rural Lands Protection Boards than those in groups one and two.

"There was no difference in survival between groups one and two or between groups three and four."

Ms Hatcher said the findings had important implications for the management of young Merino sheep.

"Weaners in groups one and two clearly require no specific management intervention post-weaning," she said.

"The relative low weaning weights of group two most likely reflect their dam’s milk production, for which they were able to compensate post weaning.

"The high proportion of deaths among group three weaners - who represented between six and 14 per cent of weaners from the 15 monitored mobs - indicates the inability of these young sheep to adapt to an independent existence post weaning.

"The economic benefit of feeding group four weaners who do not grow out to the average of the mob is questionable. Perhaps these individuals should be a priority for early sale."

Ms Hatcher said the challenge was to be able to differentiate early (i.e. at marking) for appropriate intervention, particularly for group three and four weaners.

Future research will quantify physiological differences between post-weaning liveweight profiles and identify appropriate management strategies for each, such as targeted feeding, cross-weaning or early sale.

Contact Sue Hatcher, Orange, (02) 6391 3861.