Fermentation of liquid diets for pigs

In the last 30 years major changes occurred in pig nutrition. With the increasing size of the pig farms, manual feeding was replaced by automatic feeding systems. Most pigs were fed on dry diets, but during last the 15 years a clear tendency towards liquid feeding systems was observed. In the early 80's the use of liquid co-products from the human food industry was introduced into pig nutrition. In the Netherlands, nowadays about 20% of the slaughter pigs and about 10% of the sows is fed a liquid diet with one or more liquid co-products. On a yearly base 2.8 million tonnes of liquid co-products are re-used in Dutch pig nutrition. About ¾ of these liquid co-products can be classified as carbohydrate rich, which ferment during storage. Several data sources showed that pigs fed fermented liquid co-products had increased daily gain, better feed to gain ratio and lower mortality rate compared to pigs fed a non-fermented diet. In addition, research with fermented completely compound diets (compound feed mixed with water and soaked for several hours to days) showed favourable results. In general, a higher feed intake and higher daily gain was observed when piglets were fed fermented compound diets compared with non-fermented compound diets. However, feed to gain ratio was affected negatively by feeding fermented compound diets. In conclusion, fermentation of liquid diets for pigs seems to improve growth performance and animal health. Fermentation of liquid diets for pigs might be a new feeding concept, especially because they might be an alternative for the prophylactic use of anti-microbial growth promoters in pig diets. However, at the time the present research started, hardly any information was available on the fermentation of liquid pig feedstuffs and the effects of fermentation on diet composition and energy value, and the effect of fermented diets on the gastrointestinal characteristics and growth performance traits of pigs. The major objective of this thesis was to elucidate these gaps in our knowledge