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Report no. 426

Abstract
The effect of expanded and pelleted feed for finishers has been tested in one herd.

The effect was measured by the Salmonella prevalence, production results and gastro-intestinal health and by the feed’s contents of phytase and three vitamins (A, K and B1). The test was carried out in cooperation with the Danish feedstuff industry.

The test comprised the following groups where +/- heat treatment alone expresses whether or not the grain part was expanded. The protein part was expanded and pelleted in all six groups. The fine grinding was finer and the coarse grinding more coarse than normally:

The vitamin content of the feed was not reduced significantly as a consequence of expanding and pelleting. Furthermore, there was no significant reduction in the vitamin content when measured after 2 months of storage.

There was a significant difference in the amount of bacteria in the feed between the different types of feed. The largest population of bacteria was found in the meal feed followed by the partly heat-treated feed, while the occurrence of bacteria in the other four mixes was relatively low.

The microbial eco-system in the pig’s gastro-intestinal tract was better in the pigs given meal feed (group 5) whereas the finely ground pellets affect the microbial eco-system negatively. The expanded feed (group 4) resulted in the best microbial eco-system within the mixes that were heat-treated and/or pelleted.

Pigs fed finely ground feed had a significantly higher Salmonella prevalence compared to pigs fed coarsely ground feed. The use of pelleted feed resulted in a higher prevalence of Salmonella-positive pigs compared to the pigs fed not pelleted feed. No significant difference was found on the occurrence of Salmonella when using different degrees of heat-treatment of the grain part.

The average score for gastric lesions in the pars proventricularis was significantly higher for the pigs fed the finely ground pellets. The pigs fed expanded feed and meal feed experienced the fewest lesions. There was no difference in the degree of lesions with the pigs fed the coarsely ground pellets and the coldly pressed pellets, and both groups experienced significantly fewer lesions than the pigs fed the finely ground pellets.

The production value which expresses the achieved production results calculated by using the same feed price for all mixes, was significantly higher for the group fed the finely ground pellets. There was no significant difference in the production value between the groups fed the coarsely ground pellets and the coldly pressed pellets. The pigs fed one of the three types of feed that was not given as pellets (groups 4, 5 and 6) did significantly poorer and there was no difference in the achieved production value between the three groups. The lower production value in groups 4, 5 and 6 is primarily due to a poorer feed conversion, and in these three groups there was furthermore found a considerable content of starch in the manure. However, there was not registered any significant difference in the feed wastage between the groups.

The test showed that the feed processing affects the microbial eco-system in the pig’s gastro-intestinal tract, the Salmonella prevalence and the production results. The feed mixes that reduced the Salmonella prevalence and/or had a positive effect on the microbial eco-system affected the production results negatively. Thus, on the basis of this test it is not possible to lay down unambiguous guidelines for a production process that benefits both the pig’s microbial eco-system and the production economy.

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