With corn and soybean meal prices rising (and falling) as much as the CBT limit on any given day, producers are once again becoming worried about the impact of feed ingredient costs on their bottom line. It’s no fun trying to manage expenses when a single day’s move in the grain markets changes you break even up to $5 per pig. Risk management this year is a really big challenge for many.
With the return of higher grain prices after a summer expecting lower fall prices, many producers are once again asking about the use of growth promoting additives in their diets. Even a 2% improvement in feed conversion is worth quite a bit when feed costs are $0.30 per pound of gain or higher.
There are many potential products that can be added to swine diets that may lower the cost of gain. The challenge is how to identify the one that is right for your operation. This is where on-farm testing comes in. Done correctly, on-farm testing can give you confidence in the decision process. Done wrong, on-farm testing can lead you down the road to higher expenses.
The University of Nebraska is getting set to re-release an excellent publication for those considering on-farm testing. The original publication was released many years ago and provided valuable guidance for doing on-farm testing correctly. The upcoming revision will also be an excellent guide. Written by Duane Reese, extension swine specialist and Walt Stroup and Kent Eskridge, professors of statistics, it outlines step by step how to set up a on-farm feed trial, and how to apply statistic principles to interpretation of the results.
Dr Reese shared a copy of the text with me this past week as I prepare for talks in Australia in coming weeks and I want to share some of the key points for your consideration.
Replication and attention to detail are the keys to a valid on-farm test. The more observations you can obtain of a treatment the better the estimate of the variation associated with application of that treatment in your production system.
Replication in feed trials means how many times can you capture feed weights. If 2 pens share a feeder, and you only weigh feed into the feeder, this is one replication, not two, because you have one observation for feed addition. The results of both pens of pigs is dependent on 1 feeder, thus the pens are not independent observations of feed usage. The same rule applies if you are measuring feed to a bulk bin that supplies feed to 24 pens of pigs. This becomes 1 measure of feed usage, not 24 measures of usage.
The more times you repeat treatments in an on-farm test (more replication), the smaller the difference between treatments you will be able to detect. Generally, it takes a minimum of 4-5 pens on each diet treatment to be able to detect a difference in daily gain of 0.1 lb/d or a difference in feed/gain of 0.1 units.
Replication does not mean 5 pens of a barn on one side of the aisle get one diet and 5 pens on the other side of the aisle get the other diet. In this case, the results are confounded by location, meaning you can’t tell if a difference between the diets is due to the diets or due to pens being on the north or south side of the aisle.
The same confounding occurs if you give pigs weaned on Monday one diet and pigs weaned on Tuesday the other diet. You can’t tell if a difference or lack of difference in performance is due to wean day or to diet.