Addition of probiotic to feeds with different energy and adf content in rabbits. 2. Effect on microbial metabolism in the caecum.
Effects of feed composition, addition of the probiotic Acid-Pak 4-Way (AP4W), sex, age at slaughtering (53 or 67 d.) and interactions between feed and the addition of AP4W, age and feed, age and AP4W and age and sex on the fermentation pattem in the caecum of 84 weaned New Zealand Whlte rabbits were studied. Three complete feed mixtures with different levels of digestible energy (DE, in MJ/kg of feed) and ADF content (in g/kg dry matterDM) were tested (feed I had recommended DE and hIgh ADF content: 9.22 MJ and 299 g ADF; feed II had 11.60 MJ and 254 g ADF; feed III had high DE and recommended ADF content: 13.14 MJ and 187 g ADF), each with and without the addltion of 0.5 % AP4W. High-energy/recommended-ADF diet (feed III) significantly (P≤0.05) decreased the pH value (I : 6.39a , II : 6.21b, III : 6.09b increased, the molar proportion of n-butyric acid (I : 10.3a, II : 11. 2ab, III : 12.6b %) and decreased molar % of propionic acid (I : 7.0a, II : 6.2ab, III : 5.7b %) in the caecum contents. A decreased DM content (I: 226.1a, II: 212.2b, III: 207.9b g/kg and an increased ammonia level (I: 13.3a, II: 13.8ab, III: 16.6b mmol/kg) had no negative influences on zootechnical parameters. The addition of AP4W had no influence on the parameters tested. Age at slaughter influenced the dry matter caecum content (53 days: 210.9A, 67 d.: 219.9B g/kg, P≤0.10). In older animals (67 days) differences in the proportions of VFA between female and male rabbltis were significant (mol% of acetic acid: females 78.3ª , males 81.0b %; mol% of propionic acid: f. 7.3a , m. 5.6b %), indicating that there were some differences in the microbial fermentation pattern of the caecum between females and males.
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