Growth promoters were those ‘things’ put in pig feed to make them grow faster and as vets we did not really have to think too much about them; they were the nutritionist’s or feed company’s responsibility. We have seen the withdrawal of a number of antimicrobial acting growth promoters in the nineties but there were still others remaining that could do the job. Then at the beginning of the year, the use of copper was restricted to 170ppm in grower feed (upto the age of 12 weeks) and nutritional levels of 25ppm in finishing feed. Slowly producers are seeing and reporting a drop off in performance of about 5% in growth rates and feed conversion efficiency (FCE) and in some cases an increase in those grumbling diarrhoeas in the finishers in spite of the presence of the other growth promoters and even these products are going at the end of 2005. There is a quiet but steady revolution going on, in the way we produce pigs in Europe and we have not got long to come to terms with it.
So what was copper doing as a growth promoter? The use of copper in pigs was described back in the fifties and UKASTA (Cooke, 1977) reviewed all the data (159 references) in the seventies to apply for an EU registration for copper as a growth promoter and the overall response to copper is shown in Graph 1.
Graph 1. Effects of copper in feed (ppm) on growth rate and FCE - improvements (%) (Cooke, 1977)
Optimum growth and FCE results were achieved between 200-250ppm copper demonstrating clearly a dose/response effect of 6.5 and 4.5% respectively. Levels above 300ppm caused a marked fall in performance thought to be associated with copper toxicity, as liver changes were noted.
Growth promoters often give a better response in young pigs and pigs with a background level of disease. The current ones are the same, but these antibiotic-based growth promoters such as salinomycin, avilamycin and flavophospholipol will be withdrawn after 31st December 2005, so now is the time to start evaluating the new non-antibiotic in-feed additives to replace the old ones and ensure a smooth production transition into 2006.
Formi® (potassium diformate – Frank Wright/BASF) a salt based on formic acid, is one of the new generation of additives that has recently been approved in the EU for growth promotion.
A battery of five studies carried out in Europe in young weaned piglets clearly demonstrates the dose/response to the product (see Graph 2). A very linear response is observed, ie the more you put in the better the response. This is the age when they are also very susceptible to E. coli infections.
Graph 2. Effect of Formi (potassium diformate) in feed (%) of young pigs on growth rate and FCE - improvements (%) (Overjeld and Kjeldsen, undated)
In grower/finisher pigs a more characteristic dose/response curve was reported.
Graph 3. Effect of Formi (potassium diformate) in feed (%) of grower/finisher pigs on growth rate and FCE - improvements (%) (Roth and others, 1996)
Based on their trial data, the company recommends for optimum results, 1.8% Formi in pre-starter feed, 1.2% in starter and 0.6% in grower and finisher rations.
A recent example (Dennis and Blanchard, 2004) showed in a UK trial on a 2000 place, straw based, finishing unit, that the inclusion of Formi at 0.6% (6kg/tonne) in the grower and finisher feed for 2 months had a remarkable effect on improving growth rate by 7.7% in comparison with previous batches. At the same time the herd mortality dropped from 4.25% to 2.53% (40% reduction) as well as the meat juice ELISA scores for salmonella from 59% to 27.3% (54% reduction). Prior to the study 82% of pigs were shown to be serologically positive to salmonella.
The new growth promoters or performance enhancers are different from the older antibiotic-based ones and act in a different, possibly more natural way, by assisting the pig’s own defence mechanisms against infection as well as improving digestibility of the feed. Formi is one product that can fit in very well and solve some of our current production problems and smooth out the transition period into the future, beyond 2005.
Copyright © Octagon Services Ltd December 2004
Pig technical papers on-line: index
~ www.octagon-services.co.uk ~