Oktober 2013
98
Focus on livestock
Due to the differing growth and maturity rates of bone, muscle and
fat, the percentages will also depend on the total maturity age of the
specific animal.
Classification or grading systems depending on fat cover (subcuta-
neous fat) will therefore award the same class or grade at differing
body weights in those cases where individuals differ in reaching the
desired fat cover.
Both figures depict an example of the growth curve and pattern for
an individual animal. Figure 2 indicate three important growth points,
namely weaning, puberty and maturity. The last two points espe-
cially will be later in life and at higher weights. Late maturing cattle
will therefore have less body fat at the same body weight compared
to early maturing cattle.
Later versus early maturing cattle finished in feedlots therefore impli-
cate for example:
At the same fat cover (subcutaneous fat thickness); the later ma-
turing cattle will yield larger carcasses.
At the same weight, later maturing cattle will yield carcasses with
relatively more muscle and less fat.
Later maturing cattle will generally grow faster and will generally
be better converters of high energy feed to carcass weight. This
is the result of a leaner (less fat) carcass during the feedlot period
and depositing fat at a later chronological age.
Later maturing cattle will spend a longer time in the feedlot to
reach the same carcass fat cover (as required by the classification
and price) system.
The profitability of feeding late versus early maturing cattle will
depend on the price margin and the feed margin respectively.
Generally a favourable feed margin (low grain price and high beef
price) will favour later maturing cattle. The objective is to maxim-
ise the gain (total kilograms) during the feeding stage.
An unfavourable feed margin can sometimes lead to a favourable
price margin, that is a big difference between the per kilogram
value of the weaner carcass versus the same value for the finished
carcass. In these cases the objective is to maximise the turnover
without having to put on too much gain per carcass. These condi-
tions will favour earlier maturing cattle.
The optimum carcass weight for a specific market is also very impor-
tant. The South African market is a prime example of where carcass
weights need to be within a relatively narrow weight range to secure
maximum prices per kilogram. This is generally in contradiction with
many global markets where bigger carcasses are favoured due to the
lower per unit costs (per carcass costs) in meat processing plants.
Due to the preference of an optimum carcass weight range, linked to
an optimum (mm) fat cover and age restriction (A or A/B classifica-
tion) there is also a limit on the range of maturity types suitable.
Other perspectives
The largest majority of the breeding cattle are dependant on natural graz-
ing or planted pasture. This also places more perspective on the value of
maintenance requirements of cattle under conditions of limited feeding,
both in terms of quantity and many times also quality.
It is also a known fact that the first very important function to suffer from
low levels of energy and protein feeding will be reproduction.
Figure 4
illustrates the priority in nutritional needs and the impact of nutritional
state on the allocation of nutrients in cattle.
Figure 4 indicates that, in order for an animal to survive, there will be
priorities in the allocating of nutrients to different bodily functions. Obvi-
ously, the most important will be the maintenance of crucial bodily func-
tions (such as the brain, liver, heart, etc.).
Due to the order of development, as illustrated in Figures 2 and 3, the
order of allocation will follow the developmental path of bone, muscle
and fat. In cases where the maintenance requirements are high, the other
bodily functions will suffer or will not function properly.
It can generally be stated that later maturing animals, due to bigger body
sizes, will have bigger maintenance requirements. Furthermore, in cas-
es of lower grass cover (droughts, for example) more energy is needed
to ensure rumen fill (animals need to walk longer distances to take in
enough grass) needing more energy and therefore elevating metabolism
and subsequently maintenance, even more.
Cattle that are ill adapted (the anatomical and physiological process is not
in tune with environmental constraints such as high/low temperatures,
humidity, external/internal parasites, etc.) will result in the animal to
suffer even more, often elevating the maintenance requirements further.
The reproductive rate in females (heifers and cows) is influenced by the
energy levels in the body, as dictated by the total body fat. In these ex-
treme cases where the animal is unable to take in enough or the quality of
feed is inadequate, the reproduction process will be halted.
It is therefore important for primary producers to take the maintenance
requirements of breeding females into consideration, while at the same
time producing an acceptable product to the feedlots or other finishing
units.
The genetic selection focus of primary producers should still, in order of
importance, be:
Reproduction efficiency (including ease of calving).
Continued from page 97
Making sense out of maturity
types in beef cattle
Figure 2: Total (cumulative) body weight changes and relative weight
contribution in skin, bones, muscles and body fat over time for indi-
vidual growing cattle.
