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Three experimental fattening diets were each fed ad libitum to 12 animals of 8-9 weeks of age (initial weight 2,257 ± 87 g). The diets contained 0% (Control), 2% oligofructose (OF) (Raftifeed ® OPS) or 2% inulin (Raftifeed ® IPS). After an adaptation period of 10 days, the individually caged rabbits received the same diets with Cr 2 O 3 as a marker. For the 24 h before they were euthanised (between 08:30 and 09:00), rabbits wore a plastic collar to prevent caecotrophy. Dietary treatment affected gut acidity only in the caecum where a tendency to a reduced pH in the inulin-fed rabbits was observed. The total caecal concentration of volatile fatty acids was similar among dietary treatments but a significant (P<0.05) change occurred in inulin-fed rabbits with an increase of butyrate proportion (17.6, 20.2 and 22.6% for control, OF and inulin rabbits, respectively) at the expense of acetate (75.0, 72.3 and 70.1%, respectively). Fructans were not detected in the ileum, caecum or faeces of control rabbits, indicating that both types of oligosaccharides originating from the raw materials were degraded quickly. Significant amounts of the β(2-1)-fructans were still present in the ileum content of both OF and inulin fed rabbits (1.78 and 1.63% DM). Apparent ileal digestibility of fructans was 100% in control rabbits but significantly lower (P<0.01) in OF (35.3%) and inulin (49.2%) fed rabbits. The absence of fructans from caecal and faecal samples confirms their complete fermentation by the caecal microbial flora. However, with the methodology used (which increased variability) and the limited number of replicates (4 pooled samples/ diet), no significant difference in the degradation due to the chain length of the inuline-type fructans was detected.

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Four groups of five non-lactating and non-pregnant Belgian Blue double-muscled (BBDM) cows were used to investigate the effect of energy level (E) on digestion, and blood and urine metabolites. The energy levels of the groups, applied indoors during a 140-day restriction period, were 100%, 90%, 80% or 70% of their energy requirements (E100, E90, E80, E70) respectively. Afterwards, animals grazed on the same swards for 203 days (re-alimentation period). Balance trials were conducted at the end of the restriction period (BT1) and at the end of the re-alimentation period (BT2). Blood was sampled at the end of these trials. Diets consisted of maize silage and straw (80/20 on a dry matter basis) and a mineral-vitamin premix, fed at the appropriate E during BT1, or maize silage and a mineral-vitamin premix, fed at 125% of the maintenance requirements, during BT2. Significant increases of the digestibility coefficients were found during BT1 when E decreased, resulting in a better net energy capture of 7% for E70 compared with E100 (p < 0.05). Slightly, but non-significantly higher digestibility coefficients were observed for decreasing E during BT2. Plasma concentrations of glucose and creatinine did not differ between treatments during BT1, while differences were found for triacylglycerols and alpha-amino nitrogen. A tendency for a linear increase was observed for non-esterified fatty acids with decreasing E. Differences in blood metabolite concentrations disappeared in BT2. Urinary creatinine excretion was not affected by E, while body nitrogen loss increased linearly with energy restriction in BT1. No differences were found during BT2, suggesting that non-lactating and non-pregnant BBDM cows are able to adapt to a cyclic change of body weight and body reserves. These data show that restricted cows mobilized body fat as well as body protein. It is concluded that the qualitative aspects of metabolism during energy restriction are comparable in double-muscled cows with those in non-double-muscled animals, although the magnitude of the effects may be different.