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FORA
GE AND NUTRITION

Guide 20
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7
FORAGE AND NUTRITION
Guide 2017
34
Claire Fitzsimons, David Kenny and Mark McGee
Teagasc, Grange Animal & Grassland Research and Innovation Centre, Dunsany, Co. Meath
In beef production systems, feed provision accounts for approximately 75 per cent of total variable costs. Relative to
concentrates or conserved forages, grazed grass is generally the cheapest feed source available on Irish beef farms.
Consequently, animal output from grazed grass should be maximised
Nevertheless, primary feed costs on beef farms relate to indoor
(winter) feeding periods and, particularly, feeding of finishing
cattle. An annual feed budget for the grass-based, suckler calf-
to-beef steer/heifer production system at Grange is presented
in Figure 1. The graph demonstrates that although grass silage
and concentrates account for only approximately one third
of the total feed consumed, the combined cost of both these
feeds accounts for over half the annual total feed cost.
This means that even small improvements in feed (cost)
e ciency during indoor/winter feeding periods has a relatively
large influence on farm profitability. Economic sustainability of
beef production systems, therefore, depends on optimising the
contribution of grazed grass to the lifetime intake of feed and
on providing silage and concentrate as e ciently and at as low
a cost as feasible.
Measures of feed efficiency
There are many di erent contexts, approaches and
measurements of feed conversion e ciency in beef cattle
production ranging from the individual animal to the production
system operated. Traditionally, feed conversion ratio (FCR [ie
feed: gain]) was the measurement of choice. However, the
use of FCR in cattle-breeding programmes generally leads to
selection of faster-growing animals that have a larger mature
size and, thus, a higher feed requirement. This has negative
ramifications, particularly for the cow component of suckler
beef production systems because of the proportionately higher
(overhead) costs associated with it. In essence, if an increase
in feed requirements of the breeding cow herd o sets gains
in growth e ciency of the progeny, there will be no change
in overall production system e ciency. As a result, there has
been much interest, worldwide, in examining alternative feed
e ciency traits such as residual feed intake (RFI).
Factors affecting feed efficiency
Live weight
In finishing-beef cattle, up to two-thirds of feed consumed
is used for body maintenance. As maintenance is largely a
function of weight, a heavier animal requires more feed to
maintain itself, and furthermore, for a fixed rate of live weight
gain, the feed energy required is higher for heavier animals.
Consequently, feed e ciency is better with lighter, fast-
growing animals. For example, the daily energy requirements
of a 650kg bull gaining 1.4kg live weight per day is about 15
per cent more than that of a 550kg bull gaining 1.4kg live
weight per day.
Figure 1. Annual feed budget for a grass-based suckler calf-to-
beef steer/heifer production system.
66
44
27
39
7
17
Feed intake (DM, % total)
Grazed grass
100
90
80
70
60
50
40
30
20
10
0
Grass silage
Concentrates
Feed cost (, % total)
Feed-efficient beef cattle