DIY research: a guide
19 November 2018
It seems there is always someone trying to sell producers a mineral additive, an injection, a drench, a supplement or even a vaccine that we really can’t afford not to use – or can we?
There are even case studies or testimonials from producers who have used the product with "outstanding results'. However, before buying into the marketing the first question that should be asked is “do I have a problem?.”
What works in one area may not work somewhere else. Similarly some strategies always improve productivity but did they improve the bottom line? Laboratory tests are a good guide but sometimes findings are inconclusive and the decision making becomes problematic in marginal cases.
An alternate solution is to consider doing your own trials at home – “But I don’t have the skills?” you may well argue.
If you’re looking at trialling different supplements and monitoring weight gains or comparing growth rates for castrated weaner bucks vs not, have a think about what you should monitor and what should you measure.
By adopting the KISS principle (keep it simple stupid), on-farm research could be more rewarding and easier than you think. Most research is performed at the 95% level of confidence i.e. the results found are more than 95% likely to be due to the treatment that was implemented and not solely due to chance.
Factors such as the selection of the animals, the paddocks used, the season, genotype etc. can all bias the results so some simple rules need to be observed:-
- Impartiality in selection of the animals – select every second animal or an “odds and evens” ear tag for treatment versus controls
- Always use the same curfew rules when processing/weighing the animals as gut fill is a major variable
- Ensure the treatments and controls are handled exactly the same.
The number of animals needed to be 95% sure that your results are sound will depend entirely on the difference expected and perhaps the simplest way to understand this is to consider a practical working example. Suppose you are testing whether drenching with a product will result in 1kg extra liveweight difference between the treated and untreated animals, then the formula for the number of animals required is:-
Where n = sample size
z = 1.96 for 95% probability
Ợ = Standard deviation in the trait being measured
L = The weight difference between groups
The Ợ (standard deviation) figure is the hardest to grasp and it is simply a measure of how much each individual animal varies from the mean. It is easy to calculate in Excel once all weights are recorded. So if the standard deviation is 2.5 Kgs,
Next you will want to know was it cost effective. If in doubt, again do your own trial. Value the animals at the commencement of the trial, calculate the extra costs required to achieve the desired outcome at the end of the trial and value the animal at the completion. Often there are hidden costs such as labour, additional equipment and infrastructure which need to be considered but if the exercise was not economical without including these costs, than it most certainly will not be cost effective on a bigger scale.
Suppose you have 20kg animals worth $60/head and you wish to feed them for 50 days with a ration that costs $0.60/day to obtain a final weight of 30kgs. The animal must return at least $90 when sold before you would even consider embarking on this in a bigger scale.
The calculations are quite easy; ($60 + $0.60 x 50 days = $90) but it is often the performance of the animals and the response to the ration that is the big unknown so test it in a small trial first up. Simply have a go!
Geoff Niethe - Goat Industry Technical Officer
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