Previous experiments indicated that protein level in the diet might affect intake and apparent digestibility of diets containing high levels of unmolassed sugarbeet pulp (SBP). As utilisation of dietary fibre depends on fermentation by the microflora in the gastro-intestinal tract, availability of nitrogen to the microflora could be important. It is generally assumed that most fermentation occurs in the hlndgut, although with SBP, fermentation does occur in the ileum. Therefore the source as well as level of dietary nitrogen might be important.
Four maize based diets were formulated to contain the same amount (600g/kg) of SBP (Table 1). The control diet (C) contained no added nitrogen rich material (dietary N 15 g/kg). In the other diets the N concentration was doubled by adding either soyabean meal (S), white fishmeal (F), or urea (U).
In a pre-trial period, voluntary food intake (VFI) of 17 individually housed gilts fed ad libitum on diet C was determined. The gilts were allocated to the treatments on the basis of this VFI, 5 gilts on diet C, 4 on each of S, F, and U. The diets were fed ad libitum from a hopper during a 3 week period in late gestation. After one week of adaptation, VFI was measured daily. On the last 5 days of the period, faecal samples were collected for overall apparent digestibility measurements using chromic oxide as inert marker (5 g/kg diet). Liveweight and backfat thickness of the gilts were determined at the beginning and at the end of the experiment.