Background

In Germany, about 27 million tons of grains are used for animal feed per year. Due to the high content of starch grains are a very important energy source in rations for livestock. Compared with high-protein feedstuff, the content of crude protein in grain is with about 9 to 14% not high, but still covers a very large proportion of the demand on amino acids due to its high level in the ration. Also regarding the supply of phosphorus grain is quantitatively very important.

A comprehensive chemical and analytical characterization of feed regarding the level of positive and undesired components is essential for the optimization of compound feed and animal nutrition, but so far insufficiently documented in many cases. The feed value also depends largely on factors that influence the digestibility and utilization of nutrients by the animal, and that cannot be described by chemical analysis alone. Standardized methods for prediction of the digestibility have long been an indispensable tool of the energetic feed evaluation for all major farm animals, and they have been supplemented in recent years by a variety of innovative scientific approaches.

The increased use of ceraeals for producing ethanol is associated with the production of large amounts of protein-rich by-products that can be put to good use in animal feeding. A future-increasing competition for grains is just as likely as there will be changes in the feeding value of grains caused by climate change and the increase of CO2 concentration in the air.

Starch is the dominant fraction in the cereal grain. While the level of the digestibility is overall high the quality of the starch varies. This is very important for feeding and feed evaluation, because thereby the energy efficiency of feed utilization is essentially determined. For pig and, increasingly, for poultry it is known that the preceacal (pc) digestibility of starch from cereal differ between grain species and varieties. Differences in pc digestibility are extremely large in horses. In ruminants, the microbial degradation in the rumen, in particular its kinetic, is important for ration planning and for maintaining a physiologically favorable environment in the rumen. Because of its high fermentation starch is also an important substrate for the formation of microbial protein in the rumen.

Regarding the evaluation of protein quality of feed considerable scientific progress has been made in the precedingyears for almost all farm animals. For ruminant nutrition, the kinetics of protein degradation in the rumen and the synthesis of microbial protein are the important pillars of the protein evaluation. For pig and poultry - and for horse perspectively – this is the preceacal digestibility of amino acids. By consistent application of appropriate protein evaluation systems a higher efficiency of protein utilization is achieved, since different protein sources may be combined more precisely and supplemented with free amino acids in order to meet demand. This leads to the reduction of dietary protein and reduces the need for the import of protein-containing feed.

Phosphorus occurs in seed of grain as phytin predominantly. In this form phosphorus is available for pigs and poultry only to a limited extent. In addition, the availability varies greatly depending on the activity of plant phytase in the feed or the use of microbial phytase as a feed additive. With the evaluation on the basis of available phosphorus (dP) this variation in the pig is taken into account. For poultry an evaluation system is in the stage of scientific development.

For efficient utilization of grain as feed, the grain processing (type and intensity of grinding and other technological processes with varying levels of energy input) is of considerable importance. The particle sizes and their distribution in the diet take particular influence on the extent and location of the digestive processes, with corresponding consequences for the energy benefit to the animal. Finally, the physical structure of the compound feed, which is significantly determined by the grinding intensity of the grain, also influences the compatibility of the compound feed (e.g. gastric ulcers in pigs) and the susceptibility to infections in the gastrointestinal tract (e.g. Salmonella prevention). Regarding and estimating the comprehensive process chain, not only the effects which improve the nutrient digestibility or feed conversion per kg should be considered. Furthermore the type and degree of grain processing as well as the downstream processes in the production of compound feed must be assessed as important components in consideration of the efficiency (cost, while possible additional income).