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Report no. 475

Abstract
The effect of grinding of the feed (2 mm versus 3.5 mm screen) and the shape of the feed (heat-treated and pelleted versus meal feed) were examined at two experimental stations.

The feed was used for pigs in the weight interval approx. 29-103 kg. At both experimental stations dry feeding was used ad libitum. At Experimental Station Grønhøj there were 456 pigs in the test divided into 4 groups with 114 pigs and 11 replicates (blocks) in each group. At Experimental Station Jylland there were 144 pigs in the test divided into two groups with 72 pigs and 24 replicates (blocks) in each group.

At Experimental Station Grønhøj, where both meal feed and pelleted feed ground on either a 2 mm screen or a 3.5 mm screen were used, the following discoveries were made: heat treatment and pelleting of the feed resulted in a significantly better production value compared to meal feed primarily due to a better feed conversion. However, there was no significant effect of a finer grinding on the production value. The content of starch in the manure was affected significantly by both the grinding and the shape of the feed as both a finer grinding and heat treatment and pelleting resulted in a lower content of starch in the manure. Both a finer grinding and heat treatment and pelleting caused significantly more changes in the white part of the stomach.

At Experimental Station Jylland only heat-treated, pelleted feed was used. Grinding on a 2 mm screen was compared to grinding on a 3.5 mm screen. There was no significant difference in the production value; however, a finer grinding resulted in a significantly lower content of starch in the manure.

It can be concluded that the best production value – using the same composition of ingredients and feed price – is achieved by using feed that is heat-treated and pelleted. Finely ground (2 mm screen) pelleted feed results in an unacceptably high frequency of stomach changes, and previous tests have shown that finely ground pelleted feed, in particular, increases the risk of a poorer microbial eco-system in the gastro-intestinal tract and thereby increases the risk of Salmonella. On the basis of this test with the composition of ingredients used here it is recommended that pre-mixed feed is ground so that the grain part of the feed has a particle distribution approx. as follows: below 1 mm: 50%, between 1 and 2 mm: 45%, between 2 and 3 mm: 5%, above 3 mm: 0%. In this test, this was achieved at grinding on a hammer mill using a 3.5 mm screen.

On the basis of this test it is not possible to give an unambiguous recommendation of how the particle distribution should be in meal feed.

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