Feed Conversion Efficiency in Beef Production Systems
Professor Stephen T. Morris
Management of Pastoral Animal Production and Health
Institute of Veterinary, Animal & Biomedical
Sciences, Massey University
(Paper for Angus Cattle Breeders Canterbury
16 May 2003)
Providing feed to animals is a major cost in most animal production
systems. This has been recognised by the pig and poultry industries,
where the cost of feed is easily quantified. These industries have
made significant improvements in feed efficiency through genetic
and non-genetic means. The cost of providing feed is more difficult
to quantify in grazing systems. It includes the capital cost of
land, costs of pasture improvement, irrigation, supplementary feed,
operating and capital cost of plant, machinery and labour.
Traditionally, and still today beef producers have improved their
herds by selection for growth. Growth is an easy and economical
trait to measure and is moderately heritable. Selection for growth
traits has resulted in faster growing cattle, however it has also
resulted in the introduction of some correlated undesirable traits
such as increased birth weights leading to calving difficulties,
delayed sexual maturity and increased herd maintenance requirements
associated with the feed costs of larger animals.
In most beef cattle production systems, researchers have established
that 65-85% of total feed intake is required by the breeding cow
herd and that half of that total feed intake is required just to
maintain cow liveweight. In contrast to beef cattle, pigs and poultry
breeding feed costs represent only around 10% of the total feed
costs. Therefore the costs of maintaining the breeding cowherd
is clearly an important factor determining the efficiency of beef
Despite its economic importance farmers in New Zealand do not
usually assess the cost of feed for their farming operation. The
complimentary roles of beef cattle on sheep farms complicate the
economic assessment of feed efficiency in New Zealand’s mixed
livestock farming systems. However as profitability is a function
of both inputs and outputs, there is a need to consider avenues
for reducing inputs in order to improve efficiency of production
and increase profits.
Selecting to improve the efficiency of feed conversion in a herd
has been proposed as an alternative to selecting for growth rate.
Here the producer is striving to improve the efficiency of converting
feed to gain, rather than concentrating on growth alone. Different
measures of the efficiency of growth have evolved over the years
because of the complex nature of feed use in the animal. The most
commonly used definitions to describe the efficiency of growth
Feed Conversion Ratio (FCR)
Feed conversion ratio (FCR) is a measure of the amount of feed
eaten per unit of bodyweight gain or carcass weight gain. Since
feed is the numerator, FCR should be minimised. Common values
for growing ruminants grazing pasture are around 7-10 whereas
pigs and poultry aim for values less than 2. For a production
system some people measure the feed conversion ratio for the
system as output of beef (kg liveweight or carcass weight) per
tonne of dry matter consumed. The term Feed Conversion Efficiency
(FCE) is also often used but the more correct term is FCR as
it is a ratio (i.e. feed eaten per unit of gain)
Efficiency of Feed Utilisation
Efficiency of feed utilisation is simply the reciprocal of Feed
Conversion Ratio and since feed is the denominator, it should be
maximised. The important point to remember is that more efficient
cattle will have a lower FCR and a higher efficiency of feed utilisation.
When comparing efficiency from different studies, farms or calculations
it is important to not only be clear about which term is being
used, but to be also clear about the measures (units) of inputs
and outputs used.
Intensive Finishing Systems and Feed Conversion Ratio
In theory intensive finishing systems should utilize cattle that
are capable of efficiently converting pasture to liveweight or
carcass weight. There are a number of factors that influence feed
conversion ratio or the efficiency of feed use such as liveweight,
sex, liveweight gain and breed of the animal.
Liveweight affects FCR through its effect on maintenance requirement.
The heavier the animal the greater its maintenance requirements
and, all other things being equal, the lower its FCR. For example,
a rising two-year-old steer at 350 kg liveweight has a maintenance
requirement of around 4.4 kg DM per day while a rising one-year
old steer at 200 kg LW requires around 3.1 kg DM per day for maintenance.
On a given feed supply, such as a 4-hectare (ha) paddock with
600 kg/ha of available dry matter, only 180 rising two year old
steers can be provided with a maintenance ration for three days
compared with 260 rising one year steers.
Heavier animals also require more feed above their maintenance
requirements to grow at the same rate as lighter animals, i.e.
their production requirements are higher.
To grow at a rate of 1 kg liveweight gain per day, a 350 kg steer
requires 8.6 kg DM/day of which 4.4 kg DM is the maintenance requirement
and 4.2 kg DM the production requirement. However, a 200 kg steer
requires 5.9 kg DM/day of which 3.1 kg DM is required for maintenance
and 2.8 kg DM to produce 1 kg of growth.
Therefore, lighter animals with lower maintenance and production
requirements need less feed to grow at the same rate as heavier
animals; i.e. they use feed more efficiently.
So, on the same 4 ha. paddock with 600 kg DM/ha available, 136
rising one year steers can gain 1 kg/head/day over three days while
only 93 rising two year steers can be grown at the same rate because
they cannot match the efficiency of the lighter animals.
Therefore, intensive beef production systems that start with lighter
(younger age) animals have a potential advantage over those that
start with heavier and older cattle. Another important point is
that the greater the liveweight gain, the quicker the animal reaches
slaughter weight and less time required to maintain that animal.
There is also greater output over which the maintenance costs can
be spread and hence the higher the FCR.
Sex of animal and FCR
The sex of an animal can influence FCR through
the higher (about 15%) maintenance requirement of bulls than that
of steers, with
little difference between steers and heifers. At maintenance or
at low liveweight gains (below about 0.3 kg/day) the feed requirement
of bulls is actually greater than that of steers of the same liveweight.
Note also that the feed intake of bulls and steers of the same
liveweight is often not very different. For an intake of 60 MJ
ME or 5 kg DM, bulls will grow at 0.80 kg/day and steers at 0.60
kg/day. This difference is not much more than the 15-20% extra
liveweight gain expected from the entire male over the castrate.
A second way in which sex has an effect on FCR is through the
composition of liveweight gain. The liveweight gain of bulls contains
more protein and less fat than that of steers and a similar difference
exists between steers and heifers. The cost of depositing lean
is much less than that of fat. Consequently, on this basis, the
FCR of bulls, at higher liveweight gain, will be better (less feed
per kg of gain than that of steers).
The third difference between the sexes is their potential for
liveweight gain, with entire males having a greater potential than
castrates or females. Much of this difference is really due to
the composition of gain effect and mature body weight.
Breeds and Feed Conversion Ratio
Faster growing breeds have leaner
gain and therefore a higher FCR although some claim they may pay
a slight penalty in terms
of a higher maintenance requirement, somewhat like bulls. On the
other hand, faster growing breeds also become heavier and this
counts against FCR.
In summary it can be said that lighter cattle of the same breed
and sex, growing at the same rate, as heavier ones will require
less feed per kg gain. Similarly, if animals are of the same weight,
the faster growing ones will be the more efficient.
Efficiency of feed use on a herd basis
There is however a need
to go a step further and look at feed efficiency across the whole
production system. To compare the feed
conversion efficiency of systems of beef production, the total
feed required over the entire finishing period needs to be divided
by the total beef output of the system.
Although FCR is an important component of intensive beef production,
the seasonal pattern of the feed demand is also of significance.
The lower the winter feed demand and the higher the spring demand,
the lower the need for expensive pasture conservation as silage
or hay or for winter feed crops. Systems buying calves in November
have the advantage of doubling the number of stock over the late
spring-early summer period when herbage growth usually increases.
Selecting animals that are more efficient in their Feed Utilisation
The major disadvantage of selection for FCR is that it increases mature weight
and this is a highly undesirable correlated response in the breeding cowherd.
In response to this other measures of the efficiency of feed use have been
An issue that is of considerable practical interest is the extent to which
individual animals are more or less efficient than would be expected for an
animal of their weight and growth rate. This trait has been termed the net
feed conversion efficiency or the residual feed intake. More efficient cattle
can theoretically be found within any desired cattle weight range, and selection
for improved net feed conversion efficiency (hereafter referred to, as Net
Feed Efficiency) will not increase mature size.
Net Feed Efficiency (NFE)
Net feed efficiency (NFE) refers to variation in feed
intake between animals beyond that related to differences in growth and liveweight.
Consequently it is expected that selection for improved NFE may
reduce herd feed costs with little or no adverse changes in growth
performance. Ranking animals on NFE requires measuring differences
in their feed intake, liveweight and growth rate over a defined
test period. A high NFE bull will consume less feed than expected
over the test period and have a lower (negative) net feed intake.
A low NFE bull will consume more feed than expected over the test
period and have a higher (positive) net feed intake. An animal’s
expected feed intake is predicted from the test groups’ average
feed requirements for a particular growth (say 1 kg/head/day) and
liveweight maintained (say 300 kg). An animals net feed intake
is simply the difference between its predicted feed intake and
its actual feed intake.
An example of how feed intake is a function of liveweight is shown
in the following conceptual data (Figure 1). In figure 1, as expected,
feed intake increases with animal liveweight so that bigger animals
eat more. However, there is variation and although heavier animals
eat more, there are some that are eating much less than expected
(shown below the line). Also small animals may eat more or less
than expected. This difference from expectation is termed residual
feed intake and used as the net feed efficiency term. The units
are kg feed per day, the values are likely to be normally distributed,
and by definition the mean is zero.
What is happening here is that feed intake is effectively partitioned
into two components 1) the fed intake expected for the given level
of production; and 2) a residual portion. The residual portion
can then be used to identify those animals, which deviate from
their expected level of feed intake, and they can be classified
as high efficiency (negative residual intake) or
lower efficiency (positive residual feed intake). Since “residual” is
a statistical term which may be confusing, the term Net Feed Efficiency
||Figure 1. Example of net feed efficiency (residual
If genetic improvement for net feed efficiency is
undertaken in New Zealand then it will generate profit when steers
for slaughter sooner or at heavier liveweights when slaughtered
at the same time, however, greater gains may come from the improvement
in NFE when it is applied to beef breeding cows.
EBV’s for net feed efficiency have been developed by Breedplan
and are available for industry use. The Australians have some industry
guidelines for conducting NFE tests. These tests are either conducted
on-farm or at central locations where animals from different properties
are tested together in uniform conditions. A feeding system that
gives accurate measurement of individual animal feed intake is
required. The test usually lasts for 70 days and uses automated
self feeders (with a ration of grain and hay) and cattle with electronic
We need to be sure this is cost effective for our New Zealand
grass-fed conditions and that is the purpose of a MeatNZ funded
trial at Massey University. Firstly evaluating if selection for
NFE using Australian derived EBV’s is valid under our grazing
conditions and secondly if it is to then devise systems of testing.
We are using the n-alkane method and the before and after grazing
pasture measurements to estimate animal intakes The difference
in EBV’s between the high NFE and low NFE bulls used in our
2001 matings translated to an expected 13% difference when there
progeny weighed 300kg, grew at 1.0 kg/day and consumed 8 kg of
dry matter per day.
Selection for improved NFE needs to be assessed in conjunction
with improvement in other traits such as liveweight gain (for example
600 day weight EBV) and maternal traits (for example 200 day milk
EBV). At the same time as NFE is being assessed selection for high
and low 600-day liveweight EBV and 200 day milk EBV are being evaluated.
Although not part of the original objectives of the trial we will
be able to make an estimation of the value of using high 600 day
EBV bulls (i.e. bulls in the top 10% for that particular trait)
over commercial cows and then recording the performance of steer
and heifer progeny under normal farming conditions.
In year one only the high and low 600 day and 200 day milk EBV
lines were generated and in the second year (calving 2002) the
high and low Net Feed Efficiency progeny (and the appropriate link
bulls with year one) were generated and will be moved to Massey
in May 2003.
The 2001 born steers arrived at an average liveweight of 255 kg
and the heifers weighed 244 kg. The steers have been split into
two - one group to be finished at 20 months and the other at 30
months of age. The liveweight gain of the 20-month group of steers
has averaged 0.85 – kg/head /day from arrival until 25 February
2003 when they weighed 511 Kg. The 30-month groups liveweight gains
have been 0.60 kg/head/day since arrival and they weighed 433 kg
on 25 February 2003. We have been measuring intakes on these animals
but the laboratory analyses of these intakes have yet to be processed.
The heifers are being run together and have been monitored for
onset of puberty with tailpainting and weekly blood sampling to
assess progesterone levels, an indication of when first oestrus
occurs. Onset of oestrus was quite slow last spring and some animals
had not cycled (as indicated by progesterone assay) when the bull
went in on 25 November. There was no difference in onset of puberty
between the selection lines (i.e. high or low 600 day or milk EBV’s).
The heifers were mated to four yearling Angus bulls all of which
had similar EBV figures for growth and all were fewer than 3.5
for birthweight EBV. Pregnancy rates were 90% in these heifers
over three cycles of mating with no difference between selection
The first feed intake measurements on the heifers were made in
late June and a second measurement was made in October. We are
using two techniques here, n- alkanes an indirect marker technique
and a before and after grazing technique. The latter involves splitting
the selection lines so that each group and placing them into individual
lanes within a paddock and then allocating each line the same daily
allowance per kg of liveweight (i.e. daily break size is dependent
on liveweight of group) to grow at the planned liveweight gain
(in this case 1 kg/head/day). Early results indicate no differences
in intake between selection lines.
If we accept that an objective of breeding programs might be to
increase the efficiency of production and irrespective of how efficiency
is defined; the efficiency of feed utilisation will form a major
component of the breeding program objective. Feed conversion ratio
although important in a beef systems context (i.e. more efficient
systems have lower FCR) when we select for animals on FCR or efficiency
of feed use we may be increasing mature size, which is detrimental
to a cow-calf system. Selection programmes might be better to use
Net Feed Efficiency to select for efficient animals however this
has yet to be evaluated under New Zealand pasture conditions.
Nicol, A.M. 1999. Principles of Intensive Beef Finishing. New
Zealand Beef Council Publication BC4. Intensive Beef Production,
McRae, A.F. 1999. Beef Finishing – some profitability issues.
A paper presented to Central Districts/Wairarapa Beef Council.
New Zealand Beef Council Publication, BC 31
Smeaton, D.C. 2003. Profitable Beef Production. A New Zealand Beef
Institute of Veterinary, Animal & Biomedical Sciences (IVABS)
Mail Code 411
Private Bag 11-222
Phone: 06 350 5364
Fax: 06 350 5616
Web: www.beef.org.nz or