Agriculture Reference
In-Depth Information
HERITABILITY AND PARASITES
One of the biggest challenges for shepherds is coping with inter-
nal parasites, but parasite problems are heritable, so by using
smart culling of parasite-prone animals from your fl ock, you can
drastically reduce the impacts of internal parasites. In fact, this
is probably one of the best internal-parasite-control strategies, as
80 percent of the problems in a fl ock tend to come from about
20 percent of the animals. Culling those 20 percent, and their
offspring, gets rid of so many internal parasite problems that
producers who use this strategy soon fi nd they really don't have
problems anymore. The one caveat: This type of program requires
careful record keeping. You need to keep track of which animals
need to be treated, and how often, so you can make appropriate
culling decisions.
Multiple Births
Although multiple births require more attention and care, the profi ts seem
well worth the effort. A 1987 University of Wisconsin analysis found that
5,721 ewes producing one lamb each generate the same profi t as 353 ewes
producing two lambs each. This may not sound feasible, but remember that
the amount of feed for the smaller number of ewes would be radically less,
and each ewe would produce twice as many lambs.
Of course, if it isn't possible for someone to be at home during the day
during lambing season, then ease of lambing is a much more important trait
to select for than high growth rate or even multiple births. In Minnesota we
raised Karakul sheep, which have a fairly low rate of multiple births (the fl ock
average was about 120 percent), but we were also milking cows at the time, so
we had little time to deal with the sheep. Despite their relatively low lambing
percentage, they were great, self-suffi cient mothers that never required any
assistance with lambing.
Undesirable Characteristics
When you are evaluating breed characteristics (and making culling deci-
sions), keep in mind that wool on the sheep's legs should be considered a dis-
advantage because it is unusable and makes shearing more time consuming.
Wool on the face, which is very heritable, is another disadvantage. Tests have
