QUEBEC CITY – One of the biggest challenges facing the Canadian sheep industry is providing lamb to consumers on a year-round basis.
One small group of Quebec producers has been experimenting since 2001 with how to get sheep breeding out of season without using hormones.
Sheep are seasonal breeders and it has been known for some time that light cycles trigger their estrus periods.
Seven farm flocks with 2,600 ewes are under a supervised program that exposes ewes to short and long stretches of light with guidance from sheep reproductive specialist Francois Castonguay of Agriculture Canada at Lennoxville, Que.
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“Some breeds are extremely deseasonalized,” he told 500 people attending the World Sheep Congress in Quebec City July 19.
Breeds such as Dorset, Finn and Romanov are capable of lambing out of the traditional spring season.
While sheep can be stimulated with synthetic hormones, consumers may eventually resist that practice so alternatives such as photo periods are an alternative.
“Natural is always at the forefront,” Castonguay said.
Fall is the natural mating season for sheep so most lambs are born in the spring.
The goal in Quebec is to produce three crops of lambs in two years. It is possible to record productivity levels as high as 2.6 lambs weaned per ewe per year.
“Someone who does it well will have 90 percent fertility every year,” Castonguay said.
The sheep receive eight hours of light for four months. Light periods are then increased to 16 hours per day. Ewes need to be indoors to control the light, although some farmers turn them onto pasture during the long light periods.
Ewes in good physical condition are bred midway through the short light period. Lambs are weaned at about 55 days and ewes are rebred 55 days after weaning.
Rams are included in the light treatments, living in a two-month period of short light and two months of long light.
Out-of-season breeding requires specific management skills to make it work satisfactorily. The barns must be well ventilated and temperature controlled for ewe and ram comfort.
Many producers still rely on synthetic progesterone techniques such as vaginal sponges or the hormone MGA to control heat cycles. When these are withdrawn the animal goes into estrus.
The sponge is placed in the vagina while MGA is delivered through a special feed mix.
Sponges cost up to $9.50 per ewe while MGA is around $6.30 per ewe.
However, results are variable and Castonguay said farmers need to consider the number of live lambs at weaning when calculating costs.
