4. Discussion
4.1. The effect of starch
The recommended dietary starch concentration is 100–150 g/kg during the post-weaning period, but may exceed 150 g/kg only in the finishing period (De Blas and Mateos, 2010). In the last decade, with the spread of epizootic rabbit enteropathy (ERE), which severely increased mortality in farms, the negative role of starch on rabbit digestive health has been adversely felt in the field, and the practice to replace dietary starch with insoluble fibre has been extended also to the finishing phase to prevent digestive disorders in more mature rabbits (Gidenne and Licois, 2005 and Gidenne et al., 2010). This feeding system has resulted in a worsening of overall farm rabbit efficiency because of a decrease in dietary energy concentration and the consequent increase of feed intake (Gidenne and Lebas, 2006).
In presence of ERE, a higher mortality level was observed when the dietary starch (120–180 g/kg) and the starch to ADF ratio (0.71–1.16) were increased (Carraro et al., 2007).
In absence of ERE, however, Blas and Gidenne (2010) failed to find a direct relationship between the dietary starch level and mortality rate. In very young rabbits (until 35 d), some authors found a lower mortality level when dietary starch (110–170 g/kg) and the starch to ADF ratio (0.68–1.01) were increased (Debray et al., 2002 and Feugier et al., 2006).