EFFECT OF DIGESTIBLE FIBRE/STARCH RATIO AND ANIMAL FAT LEVEL IN DIETS AROUND WEANING ON MORTALITY RATE OF RABBITS

Ten experimental diets were formulated according a factorial design with 5 digestible fibre/starch ratios (0.75-0.84, 1.07-1.17, 1.57-1.66, 2.47-2.50 or 4.59-4.27, by replacing mainly wheat with beet pulp) and 2 levels of animal fat (3% or 6%). Four hundred young rabbits were fed on each diet from 17 to 42-day old and then switched to a commercial feed until 63-day old. Mortality rate along the trial was very high (40.7%) and dietdependent. The digestible fibre/starch ratio had an effect on mortality rate: it decreased (45.8%, 45.4%, 39.4%, 38.0% and 35.0%, P<0.001) as digestible fibre/starch ratio increased; this effect originates in 4 th to 6 th week period, when differences in mortality rate were much important (36.4%, 29.3%, 24.8%, 19.0% and 13.6%, P<0.001). Moreover, the level of animal fat seems not affect total mortality rate but its distribution in the two considered periods: in 4 th to 6 th week period mortality rate was greater with the high-fat diets (26.5% vs. 22.8%, P<0.01), the opposite occurring in 7 th to 9 th week period (19.4% vs. 23.2%, P<0.05). According these results, in order to reduce the mortality rate, it seems advisable the inclusion of digestible fibre instead starch and not a noteworthy increase of the animal fat content in diets for rabbits around weaning, but further research is necessary to develop adequate feeding programs to maintain the reduction on mortality during the rest of growing period.