Effects of feed particle sixe on caecal activity and growth performances in fattening rabbits

Aim of this work was to investigate the effects of particle size of feeds forfattening rabbits on growth performances, slaughtering data and, particularly,on their caecal fibrolytic activity and caecal content characteristics. 72hybrid commercial rabbits 40 days old, divided in two experimentalgroups, were fed to slaughter (88 days) two pelletted diets (F – fine; C –coarse) of similar composition differing only in the grinding level of dehydratedlucerne meal and wheat bran. 42.3% of diet F was composed byparticles with Æ<0.315 mm, while these particles were only 31.7% of dietC (P<0.001). The smallest particle class (Æ<0.315 mm) showed 58.6% ofNDF and 33.0% of ADF in diet F, while NDF was 53.0% and ADF26.2% in C diet (P<0.001). Mortality rate, growth performances, feed consumption,and feed/gain ratio never differed between the two diets. No effectcould be registered concerning carcass weight, dressing out percentage,full gastrointestinal weight and caecum weight. As for the caecal chemicalcomposition, volatile fatty acids concentration and their proportion, no significantdifferences were registered between F and C diets, and pH averagedvery similar values in both groups (6.24 vs 6.30 for F and C respectively).Also enzymatic activity into the caecum, as fibrolytic and amyloliticresponse, was the same. So, a minute milling of different raw materials,does not appear a reliable way to significantly modify gut conditions andsubsequent rabbit performances.[...]