Text in English / Cow size influences biological efficiency of individual animals, which influences herd composition and
stock flow. This in turn influences the economic efficiency of the herd. This research followed the
thread from animal size, to biological efficiency, to economic efficiency for beef cattle production under
a typical production system in semi-arid South Africa. Cattle were grouped into three groups namely
small, medium and large cattle, with mature weights of 300kg, 450kg and 600kg respectively. The net
energy requirements of individual cattle were calculated for maintenance, growth, lactation and foetal
production, for each of the three sizes. Growth rates, milk yield, reproduction rates, and management
practices were assumed from existing research. Next the stock flow for a herd of small, medium and
large cattle were calculated from the above. Income and expenses as commonly used in the research
area were calculated from the stock flow. Gross profit above allocated costs were subsequently
calculated for the three herds under the above-mentioned conditions.
When assuming similar reproduction and growth rates for small, medium and large mature cattle, the
following results were obtained: more heads of small cattle could be held on a set resource base, but the
total live weight of a herd of large cattle that could be held on the same resource base was greater. This
was mostly due to proportionately lower maintenance energy requirements in the herd of large cattle. In
the simulation in this study, maintenance energy requirements for the herd of large cattle was 71.2%,
compared to 72.0% for the herd of medium cattle and 73.1% for the herd of small cattle. Income from
the herd of small cattle was the lowest, as less kilograms of beef were available to sell. Allocated costs
for the herd of small cattle were the highest, due to a large number of expenses being charged per head
of cattle. As a result, the herd of large cattle were more economically efficient than their smaller
counterparts. Income above allocated costs for the herds of large, medium and small cattle were
R1,182,865, R1,085,116 and R946,012 respectively.
Larger cattle generally have a lower reproduction rate under similar conditions. No equation exists that
directly links size to reproduction rates, especially considering the vast number of variables that
influences reproduction rates. However, in the form of scenarios, it could be calculated that, given a
reproduction rate of 80% for mature small cattle, when reproduction rates of large cattle were 24.7%
lower than that of small cattle and the reproduction rates of medium cattle were 15.4% lower than that
of small cattle, the large and medium herds became less profitable than the small herd. Smaller cattle mature faster than larger cattle which provides the opportunity for early breeding. When
small cattle were bred early, at 15 months, at a calving rate of only 44.5% it was more profitable than
when the same cows were bred at 24 months. When medium cattle were bred at 15 months, a calving
rate of 37.0% was needed to be more profitable than when they were bred at 24 months. Even when the
herd of small cattle were bred at 15 months with a reproduction rate of 100%, it could still not match
the profitability of the herd of large cattle bred at 24 months given the reproduction rates of all other
classes of animals were similar. When the herd of medium cattle were bred at 15 months, at a calving
rate of 53.7%, it matched the profit of the herd of large cattle that were bred at 24 months, when the
reproduction rates of other classes were equal.
Scenarios were considered were feed intake was limited. When feed was limited to a specific amount,
smaller cattle were more biologically efficient and cattle with potential for small mature sizes would
grow to a larger size than cattle with potential for medium and large mature sizes. When feed was
limited by a factor of the calculated energy requirements of small, medium and large cattle, large cattle
were more effective. This is because large cattle use proportionately less energy for maintenance, which
allows more energy to be allocated to growth, lactation and foetal production. When energy was limited
to an amount per unit of metabolic weight, small cattle were more efficient than medium and larger
cattle in the growth and production phases. Small, medium and large cattle were equally efficient (or
inefficient) in the maintenance and lactation phases. Energy requirements of cattle in South Africa are
commonly calculated using the Large Stock Unit (LSU). The LSU typically overestimates energy
requirements for cattle, except in the lactation phase. When using the LSU to match small, medium or
large cattle to a resource base, the LSU overestimates energy requirements of large cattle
proportionately more than that of small and medium cattle. This is excluding the lactation phase, where
energy requirements for all three sizes are underestimated and that of large cattle underestimated
proportionately more.
There are more considerations when matching cow size to managerial practices. A smaller body size is a
natural adaptation to a semi-arid environment and this adaptation can be expressed in different ways.
The number of animals on a resource base has implications on management practices. Having more
heads of cattle on a resource base increases genetic variation of the herd, allowing for genetic progress
to be made faster than in herd of fewer cattle. / Agriculture and  Animal Health / M.Sc. (Agriculture)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/26004 |
| Date | January 2018 |
| Creators | Venter, Theo Muller |
| Contributors | Antwi, M. A. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resource (viii, 109 leaves), application/pdf |
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