Ewes that lambed as hoggets and are culled soon after represent a significant loss to the farmer. As well, the age range for two-tooth and older ewes that die or are culled, and the reason for death or culling in commercial flocks, is based on anecdotal data. The Massey research is gathering objective data as the first step in identifying the risk factors associated with ewe wastage.
This will allow farmers to minimise risk where possible. Senior lecturer Dr Anne Ridler heads the research, with lecturer and PhD student Kate Griffiths joining the project in 2014 to help with the mountain of data being generated.
The research began in 2011. A total of 12,000, 2010 and 2011-born ewe hoggets on Castlepoint Station on the Wairarapa coast and Limestone Downs at Port Waikato were electronically tagged, to be followed for their lifetime.
Weight, body condition score (BCS), scanning results, lambing performance, culling details and death are recorded for each ewe, allowing the relationship between these to be assessed, with the focus on mortality and premature culling.
Since 2012, similar data has been collected from Massey’s Tuapaka Farm and more recently Taratahi’s Mangarata Farm has become involved.
Most of these ewes are now four years old with the balance being five years old. Of the five-year-olds about 1100 of the original 4000 remain. This is fewer than most expected, making this work even more significant. Many of these ewes have been prematurely culled but a large number have gone missing, presumed dead.
“Most farmers would like to think their mortality is about 5% while for many farms it is more likely to be 7 to 12%,” Ridler said.
“Reducing this even by a small percentage gives significant benefits.”
One farm will cull all their 2010-born ewes at the end of this year, following their usual plan. The trial has another two years of data collection then some substantial number crunching before final recommendations can be made.
Analysing the data from 12,000 animals is no five-minute task and, like all good scientists, Ridler and Griffiths are reluctant to begin drawing conclusions before all the evidence is before them.
Hogget lambing is one area where the trends cannot be ignored.
Previous thinking has been that hogget mating doesn’t affect longevity. Many farmers put all their hoggets to the ram, or assess their size visually rather than by weighing, believing that weight will affect reproductive performance but without considering how it might affect longevity.
Dr Rene Corner-Thomas at Castlepoint Station condition scores one of the 12,000 ewes tagged for the longevity study. BCS is regarded as a better indicator of health status than liveweight.
