Cattle - Raising Small Animals - page 428

• Buying off-farm replacement heifers: Though many farmers use heifers born on their
farm for breeding stock, you could give yourself genetic flexibility by buying replace-
ment heifers from someone else's farm. This allows you to introduce traits from breeds
not found on your farm. For example, you could buy crossbred replacement heifers to
breed with your purebred bull. Or, if you only keep one bull, you could use him for three
or four years and then switch to a sire of a different breed. AI also gives you flexibility
in switching sire breeds.
EPD — Expected Progeny Differences
Genetics play a large part in the development of each animal and its usefulness in a beef or
dairy production system. This is why selecting the right bull is critical, because genetics are
big determinants in growth potential and meat tenderness. If you use only one bull, his traits
will be passed on to all the calves born on your farm; if you choose your bull poorly, such as
one that is not fertile or one that produces substandard offspring, it can be crippling to your
farm's earning potential.
One tool many farmers use to select their herd sire — the bull that contributes most of the ge-
netics to the calves born on a farm — is called Expected Progeny Differences (EPDs). EPDs
are scores based on individual traits that give you an idea of how future offspring, or progeny ,
are expected to perform compared to the offspring of other animals. EPD scores are based on
the performance of the animal's parents and on the performance of the individual animal.
Breeders from around the country report this data to breed associations that maintain a data-
base so buyers can make comparisons of potential bulls. For example, farmers would weigh a
particular bull at birth, at weaning, and at 1 year old and report these scores to the association,
which would then calculate the bull's EPD scores against the expected performance of other
bulls in the breed.
These scores are useful in comparing animals within a specific breed. Breeders will provide
you the scores for their bulls, which are shown as comparisons to the breed average. For ex-
ample, if an animal's birth weight score is +10, that means its offspring are expected to weigh
10 pounds more than the breed average. For an animal whose offspring perform at the breed
average, its birth weight score would be 0.0. You can look at the scores for one or more bulls
and decide which one is most likely to produce the types of calves you want.
Common categories EPDs predict include growth, maternal, carcass, and ultrasound. Each is
discussed below.