Production efficiency and
the stature of dairy cows
Dr Carel Muller
Research Associate, Faculty of Animal Sciences, University of Stellenbosch
T
he economic efficiency of dairy cows
is becoming an important issue
mainly due to economic pressure.
Presently, the breeding objective
for dairy farming is changing towards cows
producing more milk from a lower feed intake.
Low milk yields and high cost inputs like
concentrates contribute to the vulnerability
of dairy farming. Breeding and selection
programmes in dairy herds have focused
mainly on the improvement of milk yield and
conformation traits. This, in combination with
better housing, feeding and management,
has resulted in a substantial increase in the
milk yield of dairy cows over the last 30 years.
However, a higher milk yield is also associated
with a higher feed intake. Generally, this is
because of a positive, albeit low (~20% and
not always statistically significant) genetic
correlation between milk yield and live weight
(LW). Increasing milk yield levels may result in
higher LWs and feed intake in dairy cows.
Breeders have always put a strong emphasis
on larger cows for better showring
performances. As the maintenance
requirements of dairy cows depend largely
on LW and milk yield, heavier cows producing
more milk would require more feed. Efficiency
of production could be improved by a
reduction in the maintenance requirements
of dairy cows. This would require a different
breeding objective than currently being
employed by dairy farmers.
Factors affecting lifetime profit
Factors affecting the lifetime profit of dairy
cows mainly include milk income and feed
costs. The lifetime profit of a dairy cow is
described by the following equation:
AgriKultuur |AgriCulture
Lifetime profit = (lifetime milk income + value
of calves born + cow’s own salvage value) –
(rearing cost to first calving + lactation and dry
period feed costs + health costs + breeding
costs)
This follows that for higher profit margins,
generally, cows should produce more milk
in their lifetime while reducing feed costs.
Although this is an anomaly as milk yield is
affected by feed intake, management factors
such as age at first calving, calving interval,
cow cull rates, also affect overall feed cost.
Another way to reduce feed cost would be a
reduction in the LW of dairy cows reducing
maintenance cost and daily feed intake.
Production efficiency is described as a ratio
function, i.e. milk yield/feed intake. Therefore,
efficiency may be improved in two ways,
i.e. increasing milk yield while maintaining
feed intake or maintaining milk yield while
decreasing feed intake. As feed intake is
difficult to determine, it was suggested that
LW should be used as an indicator trait. For
this reason, a ratio of 4% fat corrected milk
yield divided by the average live weight of
cows is commonly used.
Dairy breeding research
A simulation study published in 1996
suggested that South African Holstein-
Friesian farmers should select for cows
with an increased potential for milk yield
combined with a lower LW. This strategy
has not been tested in practice. Genetic
research on dairy cattle is very limited with
no structured breeding research projects
like the comparison of different sire
selection strategies, breed comparisons and
crossbreeding. This is because of a lack of
28