In 2003 Kerslake, Everett-Hincks and Campbell found dystocia (birthing damage) accounted for 57% of dead singles, 46% of dead twins and 48% of dead triplets.
Starvation-exposure was the second highest killer, at 20% of single-lambs’ deaths, 29% of twins, and 27% of triplets. No other cause of death in the lambs’ first three days topped 10%.
AgResearch’s David Stevens says while the work hasn’t been repeated, the same study today would likely find a similar pattern.
“Dystocia is certainly the most common cause of early lamb death, though it’s quite often confused with starvation or exposure.”
Top of his list to cut losses at lambing is body condition scoring ewes at key times of year, then feeding accordingly.
However, a detailed survey* of 23 high-performing Southland farms in 2011 found only 9% condition scoring and despite widespread publicity on the benefits, Stevens estimates still fewer than 15% of farms do it today.
Possible reasons for that low uptake are unfamiliarity with how to do it, concerns over time or living in hope, he says.
“Some farmers are eternal optimists and always think their ewes are in better condition than they are.”
Ewes in a race for other management practices can be scored in a couple of seconds with a hand on the back just behind the ribs and a decision made about whether they are too light, about right, or too heavy made.
“You don’t have to worry about the actual score, though you do need to be calibrated properly,” Stevens says.
At scanning minimum condition should be 2.5 (see diagram How-to-body-condition-score-sheep-diagram.pdf). Any ewes below that should get preferential treatment.
“You won’t improve their condition much due to the demands of pregnancy but you should prevent it getting any worse and you will increase lamb weight and vigour which will transfer into increased survival.
“But the most critical time to condition score is at weaning. If you put your ewes into cohorts (mobs) based on condition then and treat them accordingly you will create a better outcome come lambing next year.”
'The most critical time to condition score is at weaning. If you put your ewes into cohorts based on condition then and treat them accordingly you will create a better outcome come lambing next year.'
Before mating, mobs should be condition-checked again and ewes that failed to respond to preferential feeding culled.
“You don’t want to cull them at weaning because they might just be light because they’ve put a lot of energy into milking and produced a couple of great lambs.
“That’s only a problem if they then fail to respond to feeding and go to the ram too light. They’ll probably stay light all winter and struggle to rear their lambs the next year.”
Weighing samples of mobs is useful too, so weights can be compared from one time of year to another, but without identification of individual animals it is no substitute for condition scoring because of natural variation in ewe size, he says.
“A big ewe that’s skinny may still weigh more than a small ewe that’s in good condition and doesn’t need to be any fatter.”
*Casey et al, 2013 Proceedings of the 22nd International Grassland Congress.
Paddock factor
Record lambing losses by the paddock, either as they happen or at tailing, to build a record of your farm’s best and worst lambing sites to fine-tune future management, AgResearch’s David Stevens says.
“Identify your best paddocks and put your triplet-ewes in them.”
As an example of the difference it can make, Stevens cites a King Country vitamin trial where a 20% difference in survival between paddocks was identified. “That’s a lot of lambs.”
Slopes increase losses so keep triplets off steep ground and use sunny parts of the farm if possible.
Shelter is good provided it doesn’t induce camping and birthing in areas that become havens for bacterial infections such as navel-ill or slobbery mouth.
“Reduced wind speed is really important to reduce the chill effect on wet lambs and increase ambient temperature.”
Ground prone to waterlogging is a death-trap because of lambs’ rapid heat loss to the cold wet ground and increased risk of infection.
Conducting post-mortems is good practice to check causes are what they appear to be.
