New research conducted in a remote environment suggests a link between reproduction and parasite loads in semi-domesticated sheep.
Sheep living in Scotland's remote St. Kilda islands were found to be more susceptible to internal parasite infection if they had recently given birth to lambs, according to new research involving the University of Stirling in the U.K.
Furthermore, the study — published in Ecology Letters — found that, during lambing season, ewes that had a lamb suffered from more gut worm infections compared to those sheep that did not reproduce.
The research team found that those ewes that successfully suckled their lamb through to weaning had higher parasite counts than those whose lamb died soon after birth, the university said in an announcement.
Jessica Leivesley led the study while an undergraduate student at the University of Stirling.
“Our results also suggest that lactation is particularly costly, because females that weaned their lamb had even more parasites than those whose lambs died and, therefore, didn’t need to lactate,” said Leivesley, who is currently a doctoral researcher at the University of Toronto in Canada.
The research also revealed that the higher worm counts in reproducing females in spring led to the animals having lower bodyweight in summer, and ultimately, they were less likely to survive over the winter to breed again in the future.
Dr. Adam Hayward, a former impact research fellow at the University of Stirling and now a research fellow at the Moredun Research Institute, was senior author on the study.
He said, “We’ve known for a long time that reproduction can affect survival. Our new study provides an explanation for why this might be the case: We’ve discovered a complex but clear pathway linking reproduction to increased infections and reduced survival.”