Mensurations viscérales chez le lapin. 4. Effets de divers modes de restriction alimentaire sur la croissance corporelle et viscérale

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Abstract
Two groups of 48 Californian rabbits of both sexes, 5 and 8 wk of age, respectively, at the beginning of the experiment, were fed a complete balanced diet for 3 wk. They were allotted into 4 groups according to a factorial pattern corresponding to 2 levels of feeding (ad lib. or restricted at 71%) and 2 frequencies of access to the manger, either 7 days out of 7, or only 5 days out of 7, i.e., 71% of the time. In the latter case rabbits were subjected to the following sequence: 2-day feeding, 1-day fast, 3-day feeding, 1-day fast. Animals were sacrificed at the end of the trial. Carcasses and abdominal viscera were measured. Both types of feed restriction had similar effects on the performances. Growth rates were identical (25 g/d [day] on average) for both age groups, but the carcass weight gain was higher in older animals: 20.1 g/day vs. 18.1 g/day in the younger. Feed conversion ratio, either on a live weight or carcass weight basis, decreased as rabbits grew older. Reduction of the feeding time at 5 days/wk led, in rabbits fed ad lib, to a decrease of 78.9% in the amount of feed ingested. Both types of feed restriction (amount and time) led to a proportional decrease in weight gain expressed in carcass weight gain. They did not affect the feeding cost of this carcass weight gain: 6.00 .+-. 0.18 kg feed/kg carcass weight gain. Both types of feed restriction did not lead to a real morphological adaptation of the digestive tract; there was no noticeable increase in the tissue length or weight per unit of length. An atrophy of the colon was observed. With each type of feed restriction an increase in the weight of the digestive content was observed, despite the live weight decrease: 7% for the time restriction and + 31% for the quantitative restriction. The liver weight, expressed in percent of live weight emptied of digestive content, increased with the time restriction, especially in rabbits receiving only a restricted amount of feed (+ 28% as compared to the control fed ad lib). In rabbits with free access to the manger every day, the quantitative restriction led to a reduction of the liver relative weight (- 7%).