Investing wisely in on-farm
An on-farm trial is an investment in your business, so before starting
a trial it is important to truly understand the question you are
trying to answer. Most on-farm feed trials will never give the result
they were set up to provide. In many cases they could have easily
been decided by a coin toss, saving a lot of time, labour and expense.
The most practical feed trials for pork producers are those involving
nursery or finishing pigs. In the breeding herd, feed trials are
often not feasible to conduct because it is difficult to get adequate
replication (i.e. to accurately detect 0.5 pigs per litter difference
between two sow feeds you will need 388 sows per feed type).
There are two main considerations when conducting a meaningful
1) minimize differences in pig performance that could be caused
by factors other than feed and,
2) provide a basis for concluding the results are statistically
sound and valid for making a business decision.
So what is required to set up a statistically valid on-farm feed
trial? Take the example of a producer who wants to look at two different
grow-finish programs. One feed program is the control (currently
in use), and the other is the test program. To be statistically
valid the following items must be able to be measured and controlled:
- Weighing pigs and feed
- It is essential to use a reliable set of scales to weigh pigs
and feed. Estimating pig weight by sight and feed by volume gives
an estimate but is unreliable.
- Use the same set of scales for the entire trial and ensure they
are calibrated before each use. A 25 kg bag of commercially prepared
feed or premix can serve as a practical check weight.
- At minimum pigs should be weighed at the start and end of the
trial or ideally at the end of each phase.
- Feed usage can be calculated in a number of different ways.
At minimum the total amount of feed used during the trial should
be recorded and any feed left over in feeders and feed bins subtracted
from the total.
- Having adequate replications
- Replication is important to minimize mistakes and to ensure
correct conclusions are made. A replication means observing at
least two pens of pigs per feed type.
- In this case it means having four pens, with their own feeders,
two for the control program and two for the test program. Suppose
only two pens of pigs were available to conduct the feed trial.
If the test program outperforms the control program can you conclude
that the new feed is better? No, you cannot be certain that the
difference in pig performance was due to feed. It could have been
due to other factors, such as a malfunctioning water nipple or
simply chance variation.
- Table 1 provides guidelines for the number of pens per feed
program needed to detect a difference between two feed programs
with a 95% degree of confidence.
Table 1: Required Number of Pens Per Feed Program for Nursery
and Grow-Finish Feed Trialsabc
|Percent improvement in daily gain or feed/gain
||Number of pens/feed type
a Reese et al. 2000
b CV=7% and alpha = 0.05
c Applicable to >5 but <30 pigs/pen
- Repeat the trial if you cannot get enough pens at one time for
adequate replication. Ensure that the trial is set up the same
way each time.
- Selecting Pen Location
- To reduce variation all pens used in the trial need to be the
same size and contain identical equipment (i.e. flooring, feeders,
water nipples, etc.).
- Trial pen location within the building should be randomized
so location does not influence the outcome of the trial (i.e.
provide a better/worse environment).
- Use adjacent pens (with separate feeders) to create a block
of pens where both the test and control program can be evaluated
under the same conditions.
- Minimizing Pig Differences
- The effects of variation in weight, genotype and sex should
be equalized across pens.
- Initial pig weight is considered the same between pens if the
difference between control and test pig weights is less than 5%
of the average weight of all pigs in the trial. For example, the
average initial weights of the control and test pigs are 25.2
kg and 25.8 kg, respectively. The average weight of all pigs in
the trial is 25.3 kg. Therefore, the difference in average initial
weight of both groups is 2.4% of the average weight of all the
pigs in the trial. If the difference had been greater than 5%
then pigs would have to be reallocated to reduce the weight variation.
- The number of barrows to gilts does not need to be the same
in each pen. However the ratio of barrows to gilts and the total
number of pigs must be the same in each pen.
- Starting with Suitable Animals
- Start with healthy animals that have received the same vaccination
and pre-trial treatments.
- In the event a pig dies before the trial is completed, record
its weight and the date it died so the feed and growth data can
- Controlling the Timing and Duration
- Pigs fed the control and test program must begin the trial on
the same day.
- Determine where the end point of the trial will be. Ideally,
for grow-finish pigs feed trials should be terminated when the
pigs achieve a predetermined market weight.
Once the data has been collected it needs to be tabulated and analyzed
statistically to help make valid conclusions. There are a number
of programs, including Excel® that can simplify the analysis.
Enlisting the assistance of your feed representative or nutrition
consultant can also help to make the whole process easier.
On-farm trials involve a lot of time, effort and dedication but
designed properly they help you make sound business decisions. As
an added incentive, certain types of scientific research that you
do to improve your business may qualify for the Canada Revenue Agency's
Scientific Research and Experimental Development (SR&ED) tax
incentive (www.cra-arc.gc.ca/sred/) making on-farm trials well worth
Reese, D.E and Stroup, W.W. 2000. Conducting Pig Feed Trials on
the Farm. University of Nebraska Cooperative Extension.