We want to breed for April lambs so we introduce our ram to the ewes’ pasture in early November. Prior to moving him to the girls’ field, we put a marking harness on the ram. This harness holds a rectangular crayon.
When the harness is strapped onto the ram’s body the crayon is held at his chest.
When the ram mates with a ewe, the crayon rubs against the ewe’s rump and leave a color on her wool.
When using a marking harness you need to change the crayon about every 2 weeks because a ewe’s estrus cycle can be last anywhere between 13-19 days, depending on the breed and individual sheep.
We have had a couple ewes that cycle every 14 days so we change the crayon on our ram’s marking harness every 14 days. The new crayon is always a shade darker than the crayon before, i.e., yellow is followed by orange then red. Changing the marking harness crayon to a darker color each cycle will indicate if any ewe is mated (or covered) during her second (or third) estrus cycle with the ram.
We leave the ram in with the ewes until there is a cycle where none of the ewes are mated again. Once the ewe is bred and the pregnancy takes, she will not ovulate (or cycle) again.
For example, on day 1 we put the harness with a yellow crayon on the ram and put him in with the ewes. On day 14 we change the crayon to orange. Say all 11 of our ewes are marked with the yellow crayon before we change colors on day 14. After we change to the orange crayon, we wait to see if any of the ewes are re-mated and marked with the orange crayon. If none of them have orange rumps after day 14, we would conclude that they were all bred and became pregnant during the first estrus cycle and it would be safe to separate the ram from the ewes.
If any of them end up with an orange rump (like the one above), we would change the crayon to red on day 28 (14 days after changing to orange) and wait to see if any ewes are bred once again.
By using the marking harness you not only know which ewes are pregnant, but you can also estimate due dates. As with estrus cycles, gestational periods vary by breed and can range from 144 days to 152 days. If you make note of each ewe’s breeding you can calculate her estimated due date and lessen your trips to the barn or field to check for signs of labor.