Centre for Genetic Improvement of Livestock
Update 2000

Counting Sheep ... Year-Round
by
Kelly Crowe and Jenny Tye

"If Ontario wants to compete globally against Britain and New Zealand in the fresh lamb market, we have to be intensive to be more efficient"

Dr. Jane Tosh, a research associate with the Centre for Genetic Improvement of Livestock (CGIL), is working with sheep genetics specialist Delma Kennedy, Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) to evaluate the potential of sheep to lamb year-round. Their goal is to make genetic evaluations of sheep available to farmers to help them select for animals with shorter intervals between lambing, and for those most capable of lambing outside the traditional season.

"If Ontario wants to compete globally against Britain and New Zealand in the fresh lamb market, we have to be more intensive to be more efficient," says Kennedy.

A Consistent Supply

The researchers are generating numbers called Expected Progeny Differences (EPDs) for those specific reproductive traits in sheep that will help lead to a more consistent supply of lamb. EPDs are used in many livestock industries including the beef and lamb industries and are used to predict how an animal's progeny will compare genetically to an average animal for certain traits.

Currently used by sheep producers, EPDs help select those individuals in a flock that are genetically superior for traits related to meat production such as market weight, rate of gain and ultrasonic measurements of loin fat cover and muscle depth. However, EPDs are not available to help producers identify animals with shorter lambing intervals or animals that breed outside of the spring breeding season.

"Until now, genetic evaluations focused mainly on meat and weight characteristics of lambs," says Tosh. "We're now looking at other characteristics that are more difficult to genetically evaluate, such as those ewe traits that could lead to the year-round supply of lamb."

The problem is tough to tackle. Both genetic and environmental factors can greatly influence reproductive traits in all species, including sheep. To determine whether EPDs can be generated for these traits, the researchers must determine the role of genetics.

Kennedy and Tosh are analyzing data from a private flock of over 400 Rideau-Arcott ewes near Grand Valley, Ontario. Meticulous records have been kept on these animals. Mathematical models, which take into consideration the genetic and environmental factors that may influence when and how often an ewe lambs, are now being applied to the data by the researchers.

This study will help the researchers separate genetic and environmental factors and look at how genetics alone, influences these reproductive traits. Kennedy and Tosh hope to determine a reliable method to calculate EPDs for reproductive traits that may help farmers supply a fresh product outside of the traditional season.

"We know EPDs are useful to producers for making better selection decisions, because they're objective measures of genetics, free of environmental influences," says Tosh.

The difference made by the decisions based on reliable EPD values can appear negligible in a flock at first; farmers may only see a 10 per cent increase in the number of lambs born per year. But in commercial-size flocks with 300-400 ewes, the increase could translate into substantial profit.

This research is sponsored by OMAFRA.