Page 15 - Te Mania Angus 2021 Catalogue eBook

calf, so keep it positive but keep in mind the implications of too much milk.

Scrotal Size (cm) This figure tells us about the scrotal circumference of an animal at 400 days of age.
We measure scrotal size because there is a strong positive correlation between scrotal size and fertility
in the male and female offspring. The larger the testicles, the more likely that bull will sire more fertile
daughters and get more females in calf. A higher positive value is better.
Days to Calving DC (Days) This tells us about female fertility. It is expressed as the number of days
from the start of the joining period until subsequent calving. A more fertile cow i.e. one that gets in calf
earlier is obviously more beneficial in a breeding program. A negative value here is better.
Carcase Weight (kg) Carcase weight provides us with an estimate of the variation in carcase weight
of a particular animal’s progeny at slaughter (this figure is adjusted to 750 days of age). The higher the
number the better.
Eye Muscle Area (cm2) Results from ultrasound scanning of cattle at 15-18months of age are used
to calculate the expected genetic differences between animals in eye muscle area at the 12th/13th rib
site, in a 400kg carcase. This figure gives us a good idea of the muscling ability of the animal. The more
muscling an animal possesses the better. Therefore a higher positive value is better.
Rib and Rump Fat (mm) Ultrasound scanning data is also used to calculate these figures which
estimate the genetic differences between animals in fat depth at the 12/13th rib site (Rib Fat) and P8
rump site (Rump Fat), in a 400kg carcase. Very fat cattle may produce less yield, however cattle that are
too lean may run into fertility problems, so these figures need to be monitored. The best way to monitor
yield and fertility is to keep an eye on those traits rather than concentrating on fat depths.

Retail Beef Yield % (RBY%) RBY% tells us the expected genetic differences between animals in
percentage retail beef yield in a 400kg carcase. A higher positive figure here is better.

Intra-muscular Fat % (IMF%) Marbling is very important for the premium markets. Ultrasound
scanning measurements for IMF (which are highly correlated to actual marble score) are used to provide
us with an EBV that estimates the genetic differences between animals in marbling at the 12/13th rib
site in a 400kg carcase. A higher positive value here is better.

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