The 2006 European ban on antibiotics as growth promoters is a well-accepted regulation, says Martin Verstegen, an animal nutrition professor at Wageningen University, the Netherlands.
Organic acids are considered the new generation of growth promoters, Verstegen told attendees of the Minnesota Nutrition Conference session on non-antibiotic alternatives available in Europe.
About 90% of pigs in the Netherlands receive organic acids as an alternative for growth promotion. Fed as a fermented ingredient, organic acids have been shown to improve protein digestibility and decrease gastric pH — resulting in increased enzyme activity and boost pepsin activity. The fermented feedstuff has the greatest effect in diets low in essential amino acids, he adds.
Organic acids have a preservative effect on feed, and are thought to influence gut microflora in two ways. First, a change in physical conditions occurs, which is less appropriate for pathogenic species growth, explains Verstegen. Second, the acids may be lethal to some pathogens.
New developments are expected regarding acid mixtures and protected acids that can affect microbials at specific locations in the intestine, the Dutch scientist says.
Another new development is the use of pre-fermented feeds in liquid nursery diets. About 20 to 30% of pigs are fed wet diets in the Netherlands to reduce drying costs. Lactic acid is a good acidifier, but the feed pH must not be too low (4.8 or higher), particularly for young pigs, or intake becomes a problem, says Verstegen.
Prebiotics are inexpensive and commonly used. Prebiotics belonging to the group of non-starch polysaccharides are a group of carbohydrate compounds that can affect gut fermentation and microbiology, the immune function and, ultimately, health of the intestinal tract. They seem to work best in poor conditions, and the most benefit may be in combination with specific probiotics. The most promising prebiotics have not been established.
Enzymes used widely in poultry and increasingly in pig diets hold much potential, he says. It has been suggested that enzymes can reduce viscosity in the gastrointestinal tract, increasing rate of passage and counteracting bacteria proliferation.
