Perirenal fat, carcass conformation, gain and feed efficiency of growing rabbits as affected by dietary protein and energy content
In three experiments, a total of 617 rabbits from weaning at 37 days until a live weight of approx. 2.5 kg at an avg. of 85 days were fed one of six different compound feeds with increasing protein/energy ratios (P/E). Experiment 1: 1. 79 and 1.96 % crude protein/MJDE per kg DM, experiment 2: 1.79, 2.28 and 2.46, and experiment 3: 1.79, 1.83 and 2.59. The rabbits were slaughtered at an average of 2.9 kg live weight at 99 days of age. An increase in P/E resulted in a significant decrease in the amount of perirenal fat, in experiment 2 from 49.4 g to 38. 7 g and in experiment 3 from 39.4 g to 28.4 g. A significant reduction of dressing out percentage was seen in experiment 2 and the same non-significant reduction was seen in experiments 1 and 3. A significant increase of feed conversion was found in experiment 2. For hind part as well as back, a subjective score for fleshiness showed a tendency to fall at the highest P/E-values and for the combined evaluation the effect was significant. lt is concluded that it is possible to affect the amount of perirenal fat by changing the P/E ratio of the feed. At high P/Evalues, this may, however, be expected to result in reduced daily gain and feed conversion, increased mortality and poorer fleshiness. lt should be considered to use other methods for adjusting the amount of perirenal fat at a given weight, for instance through breeding.
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