Dairy Sheep Symposium - the Department of Animal Sciences ...

Fall Lambing Percentage
100
90
80
70
60
50
40
30
20
10
0
69
12/15/99
Production
Group
2000 Light Treatment Results
55
1/15/00
Production
Group
8
1/15/00
Elite Group
81
2/15/00
Production
Group
30
2/15/00
Elite Group
• The 2/15/2000 Production Group: 81 percent of the 73 ewes lambed in the fall of 2000.
• The 2/15/2000 Elite Group: 30 percent of the 24 ewes lambed.
Discussion:
In looking over these results, it is quite clear that our success rate in the Elite Groups was
much lower than for the Production Groups. There are two different variables for the Elite
Groups when compared to the Production Groups. The Elite Groups were comprised mostly of
replacement ewes, and while the ewe to ram ratio was never more than 10 to 1 in any of the
groups, there was only one ram each in the Elite Groups. The production Groups had ten or more
rams each.
It is not clear which of the variables contributed more to the lower success rate in the Elite
Groups, but we suspect it was the lowered ram effect of having only one ram per group. For
2002 we plan to try a group of Elite replacement ewes that will be exposed to a number of rams
simultaneously.
As this paper was prepared in late September, our 2001 Fall lambing results were not complete.
However, judging from the pregnancy checking we did in August, and the ewes that have
lambed so far, we are expecting that about 68 percent of the 125 production ewes that were in
light treatment will lamb. It also seems clear that about 66 percent of the ewes which left the
parlor between February 1 st and June 1 st this year, will also lamb this Fall. Unfortunately, only
about 30 percent of the 75 elite light treatment ewes have scanned pregnant or have lambed.
Having completed our third year of using light control, we are now confident that we can
consistently get between 60 and 70 percent of ewes exposed to the protocol to lamb in the Fall if
we can expose them to a group of rams. As mentioned earlier, these light treatment results are
better, more consistent, and considerably less expensive in time and money than those we
achieved with the hormone treatments we experimented with over the years.
However, there are downsides. To start light control groups in January, February and March,
ewes have to be held out of the normal breeding season. So even with a 70 percent success rate,
we still have 30 percent of the ewes that don’t lamb in the fall, and so we miss a season of
production from those ewes. Because it is so important for us to have adequate fresh milk in the
Fall, when demand for our products is the highest, we have accepted this downside.