Ewes with newborn lambs. Picture – Craig Hinchliffe.

ANIMAL activists’ annual campaign against winter lambing has been blunted by new Australian research proving that dystocia or birth difficulty, not cold conditions, is the main cause of lamb mortality.

The annual anti-farming pitch by the Farm Transparency Project, timed to coincide with lambing season, has been countered by new CSIRO-backed findings that show primary exposure accounts for less than half the deaths caused by difficult or still births.

Calling themselves investigators, the activists spent a day in the Adelaide Hills in June to witness lambing. In a video, a woman is seen trespassing onto a property to handle a new-born lamb, carrying it to a pile of hay while rubbing it.

The group claimed: “Winter lambing is a widespread industry practice in Australia. It leaves little lambs like this one, completely vulnerable.

“Their mother still had blood and afterbirth hanging from the back of them. The lamb had just been born. They were covered in mud, exposed to the rain.

“The mother ran away as we approached,” the protestors wrote on social media. “A investigator cleaned off the mud and placed the baby lamb within a pile of hay. We hoped that it would be warm enough to prevent them from dying.”

Elsewhere the activists reported seeing ‘the bodies of lambs that succumbed to the harsh conditions, dying from hypothermia, starvation and neglect’.

But research released in the last week of June has proven their assumption is incorrect.

In fact, dystocia is more of a killer than the combination of starvation-mismothering-exposure (SME).

Over the five-year study period, dystocia averaged nearly 40 percent of recorded lamb deaths while various SME factors averaged 30pc – and primary exposure accounted for only half of that percentage.

Jennifer Smith from CSIRO Agriculture and Food led the research that focused on a  New England flock of the 1350 Merino ewes, recording birth, neonatal mortality and lamb necropsy examination over five years, covering 5475 lambing events and 7798 lambs. The lambing paddocks had shade cloth along fencelines and grass tussocks offering shelter. Two of the years reported well-above long-term average rainfall and one drought year. Lamb survival was calculated from birth to marking.

The researchers explained: “In this study, predicted mortality was used to extrapolate lamb survival outcomes from an intensively monitored research setting to lower-input systems typical of commercial Australian sheep production.

“The proportional mortality for cause of death observed in this study, including dystocia was broadly consistent with other Australian and New Zealand studies.”

The study revealed factors other than exposure that increased the risk of lamb mortalities. Lambs of extreme birthweights – very light or very heavy, were more likely to die, as were male lambs and multiple-birth lambs. Lambs born to two-three year-old ewes had lower odds for predicted mortality than did lambs born to four year-old ewes.

Wind chill was measured and the researchers noted that each 1 kJ/m².h increase in chill index at birth increased the odds for predicted lamb mortality by 2pc.

Disease such as listeriosis was also pinpointed as a prominent cause of death in several seasons.

The team suggested that strategies aimed at improving lamb survival in two year-old ewes should focus on twin and triplet-bearing ewes. They also highlighted the value of veterinary diagnostics in identifying infectious disease outbreaks.

Other researchers in the team were CSIRO’s Heather Brewer and Caroline Jacobsen, Emmanuelle Haslin and Bronwyn Clarke, all from Murdoch University.

The research article can be found at https://doi.org/10.1071/AN26070