Material and methods
Animals, housing and design
This study has been conducted at the Research Farm for organic pig production in Raalte, the Netherlands from July 2011 to January 2012. The experiment comprised two dietary treatments:
1) control, pigs fed compound feed only
2) silage, pigs fed a mixture of compound feed and grass silage.
Each treatment comprised 8 pens with 16 pigs each, females and castrates mixed, in total 256 pigs (Pietrain x (Dutch Landrace x GY)) from 26 to 119 kg body weight. At a mean age of 11 weeks and a mean body weight of 26 kg, the pigs were blocked on the basis of offspring litter, gender, age and body weight and allocated to the two treatments. The pigs were housed in two naturally ventilated rooms with 8 pens each. Pen dimensions were 4.4 x 4.7 m of which 4.4 x 1.6 m was concrete slatted floor. Straw was used as bedding material in the closed area. In addition, each pen was connected to an outdoor area of 4.7 x 3.2 m, half of which had concrete slatted floors.