The use of feed additives in the Poultry Industry
By Rick Kleyn, SPESFEED (Pty) Ltd
In
broad terms feed additives could be classified as non-nutrient additives that
are added to the diet in relatively small quantities, often at considerable
cost. Feed additives such as
anti-biotic growth promoters (AGP’s) and coccidiostats have been widely used
in the poultry industry for many years. However,
as producers and nutritionists, we are being forced to rethink our approach to
what we are doing in terms of feed additive inclusion in our diets for a number
of reasons. Firstly,
the use of AGP’s is being questioned, if not already banned, in both
Europe and the USA, and this has led to a plethora of new products which purport
to fill the gap left by the removal of AGP’s. Secondly, we have become
increasingly aware of the threat of mycotoxins, how we should best react to them
and what additives, if any we should use to combat them.
Thirdly, there has been a dramatic increase relating to the use of
enzymes in animal feed and any nutritionist would be foolish not to consider
their use in some way. Lastly, and
somewhat cynically, all of the companies that market additives employ
professional marketers who are capable of being very persuasive.
Prof Nick Dale of the University of Georgia summarises the situation most
eloquently - “Much like the evolution of the species, many feed additives at one time
or another have made an appearance, and either gained a significant market
share, maintained themselves in a modest but consistent role, or languished and
finally disappeared. New additives
are introduced each year, frequently with considerable public relations effort.
Over time, the nutritionist tends to become a bit cynical about new
products, having seen so many rise and fall.
However, we also know that it would be foolish to blind ourselves to the
possibility that a new and innovative additive might well be of significant
importance in our feeding programs. As
a result, many nutritionists have developed a mental balancing act, anxious to
incorporate real innovations but suspecting (probably correctly) that the
majority will be of little value.”
There
are a number of steps that one needs to go through when evaluating any additive.
I like to think of these as the five R’s of
additives. I have listed these in
what I deem to be the order of importance and it is hoped that by giving some
structure to the process of evaluation the mental balancing act will be
simplified.
Research
It is essential that in the development
of any feed additive the scientific process has been followed.
This
is best illustrated by figure 1. Firstly, we need to make astute observations.
We all ‘observe’ all the time. For
example, we observe how an animal grows, that food intake increases in cold
weather or that certain ingredients lead to better performance.
In addition, by reading the scientific and popular press, many
observations are made. Over time
these accumulate, leading us to make assumptions, have ideas or even develop
theories. These theories need to be
tested, and a hypothesis is then formed to test the ‘logical or empirical
consequences’ of our theory. It is at this point that experimentation begins.
For example, we could feed different levels of an ingredient in the diet,
or use a range of different feed additives.
In order to generate valid trial data an
experiment needs to be properly designed and then managed. Experimental
design is a complex topic and beyond the scope of this article.
However, there are two things that commercial practitioners need to be
aware of. Firstly, accurate
experimentation can only be carried out if sufficient replications (the number
of pens) of each treatment were used. Secondly,
all hypotheses, in this case the use of an additive, need to be compared to a
control or standard treatment. Normally
this control would be a “negative” control in which the product to be tested
has been omitted. The inclusion of a
“positive” control in the form of an alternative product may also be very
useful.
Figure 1.
An outline of the scientific process.
We need to be sure that the differences that are claimed are “real” and not
simply the result of chance (numerically different).
A simple comparison of two houses or sites tells us little as there is
simply no way of knowing if any differences occurred as a result of chance or as
a result of the treatment applied. In
short, there is a 50% probability that any treatment applied will have a
positive result.
A comparison of averages of large numbers of birds or animals under commercial
conditions is generally unlikely be meaningful.
If this comparison is between birds kept in different geographic regions
it is probably not valid at all. It
is also questionable to compare results between two different time periods
(cycles) because apart from climate differences there may also have been a
number of other management and/or disease status changes.
All too often the feed additives are developed and marketed based on a
hypothesis without any experimentation to verify the underlying theory. Much
misinformation and unfounded speculation about nutrition is disseminated through
the popular press, with the worst culprits probably being advertisers.
This often clouds the issue. Fortunately
for those of us involved in animal agriculture this happens far less than it
does in human nutrition, where nothing prevents people from bringing ideas
(hypothesis) to market.
From a practical point of view, it is important to determine if the experiments
were designed and conducted under conditions that are similar to those that are
experienced in practice. For
example, is the stocking density used in the experimental design the same is as
used on your farm, and if not does it matter?
Another major distinction that needs to be made is to determine whether
data was generated using an in vitro
(in a test tube) or an in vivo (in the
animal’s body) method. In vitro work can be very useful, but the method used must be proven
to be a reasonable model of what occurs in vivo, before it can generally be accepted.
There is a final point about any scientific research.
Science has moved forward by means of peer review.
This means that before an article is published in a recognised journal,
fellow scientists review all aspects of the scientific process.
What this means is that all articles published in journals such as
Poultry Science and British Poultry are as sound as is humanly possible.
Articles in the popular press, the web and even papers presented at
conferences often are not peer reviewed. This
is not to say that these articles are inferior, but it does mean that the
practitioner needs be a little more cautious when using data from these sources.
Response
The response
observed during experimentation is related to the performance changes the user
could expect when a feed additive is included in the diet.
For example, higher peak production in layers, or an improved feed
conversion ratio in broilers.
It is important that we recognize that the response to
any additive will vary and, by extension, that pen studies carried out in
experimental facilities may not necessarily give an indication of the full
potential benefit of the additive. In
many cases it is known that the maximum benefit from an additive is only gained
when on farm conditions are poor. The
AGP, Zinc Bacitracin, is just such an example, where it is now well known that
the best response to it is achieved under poor farming conditions.
The method by which response data is analysed has a direct bearing on not only
the measurement of the “response” but also on the manner in which the
response is interpreted. This is a
highly technical topic and goes beyond the realm of this article.
However, it is important that nutritionists be aware that there are a
number of different ways of doing this and that they use the correct approach.
Finally, it is sometimes difficult to measure response.
It has been calculated that in order to measure a 1% response in broiler
with any degree of statistical confidence, a trial with 400 replications of each
treatment need to be carried out. This
may be of little relevance for aspects such as feed conversion or growth but any
researcher will tell you that it is very rare to measure any statistical
difference in mortality – simply because not enough experimental replications
are used.
Returns
The return reflects the profitability of using a selected additive.
For example, if an improvement in growth is measurable then a breakeven
point can be calculated. For
example, an additive may cost R 50.00 per ton (5 cents per kg) of feed.
Assuming that a live broiler is valued at R 10.00 per kg and that it
consumes 3.2 kg of feed in its lifetime, then the additive would cost would be
16 cents per bird. In order to break
even the bird will need to weigh 16 grams more at 40 days of age.
From a slightly different perspective, if a medication regime were to
cost R 200 per ton then the cost is 64 cents per bird.
In order to break even the mortality rate would need to drop by 3.5%.
A guideline often used is that an additive should return two rand or more for
each rand invested. This would build
in a safety margin into the calculations to cover non-responsive flocks and
field conditions which could minimize the anticipated response.
In complex integrated operations the expertise of
accounting personnel may well be needed for any calculation of cost/benefit of
using an additive. A modest
benefit in growth or feed conversion may not be enough to justify use of the
product. In addition to product
cost, there are hidden costs such as purchasing, warehousing, accidental
spillage, and possible confusion by mill personnel.
As a matter of procedure one should take the statistical analysis into
consideration when evaluating an additive from an economic perspective.
Often there may be a numerical difference between two treatments but
there is no statistically significant difference between them.
Any financial calculation should then be based on the average of the two
figures and not the numerical difference, as no proven difference exists between
the two and we can not
be sure that the differences measured arose through chance or the treatment
effect. In cases where no
significant difference is shown, unless repeatability of the results has been
shown, then extra attention should be paid to these types of calculations.
Results
Regardless of what the research benefits are, or how cost effective an additives
use is in theory, they are of little benefit if we do not see measurable results
on farm. Nick Dale contends that feed can become
like an attic, full of forgotten odds and ends.
Once we leave the relative comfort of essential nutrients behind,
vigilance is essential. Many
additives will have greater or lesser impact in different seasons of the year
and at different ages in the life of the bird.
In short, there must be a continued economic payoff on individual farms.
As such, managers and nutritionists need accurate records (a database) in
order to compare and measure responses on farm.
Weight for age, FCR, hen housed production and PER are the measures that
need to be considered, and then these figures should be used in order to carry
out critical economic evaluation of a selected additive.
Regulation
The regulations that have covered the use of non medicated feed additives have
possibly not been as stringent as they could have been.
For example, the safety and efficacy data required for an AGP is simply
not required for many of the other classes of feed additive.
This is a situation that is fast changing in
Wraping up
You may well ask why I have gone into this detail about something that would
appear to be very scientific. The
reality is that each one of us has to make decisions, which often have large
financial implications, based on data derived from the literature, the suppliers
of the various additives and most importantly from our own farms.
Using some of the points made above it can be shown just how difficult it is to
make the right decision. I have
shown that if an additive costs R 50.00 per ton of feed, the birds need to weigh
16 grams more to break even. Applying
the ‘two times’ rule, we would expect to measure a 32 gram improvement per
bird if we were to use the product.
This represents a 1.8% increase in the weight of a 1.8 kg broiler.
As pointed out, this type of difference is difficult to measure in a test
house and almost impossible to measure on farm.
Remember too, that holding an additional ingredient in the feed mill ties
up capital and there is always the risk of shrinkage.
We should all be wary, possibly even cynical, of the results of product trials
that have not been properly designed or submitted to proper (valid) statistical
analysis. Yet having said this, we
need to be equally careful not to discount an additive that may have significant
financial advantages, even if the data on it is scant.