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Castell, Johanna (2005): Untersuchungen zu Fütterung und Verdauungsphysiologie am Spitzmaulnashorn (Diceros bicornis). Dissertation, LMU München: Faculty of Veterinary Medicine
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Abstract

In this study, food intake and apparent digestibility coefficients of eight adult black rhinoceroses from three zoos were investigated. In every zoo the regular zoo diet, a diet with added quebracho, and a diet with added tannic acid were fed. In one zoo, two additional diets with added browse were used. One animal received a diet with low proportion of roughage because of chewing problems due to an abscess in the oral cavity. Every adaptation period lasted two months. Feeds offered and refused and faeces were collected in toto. Additionally, the concentration of volatile fatty acids, lactate and the antioxidative activity were measured in the faeces, as well as faecal particle size distribution, water intake and the calcium:creatinine-ratio in sporadically sampled urine. Three animals were actually weighed; the body weight of the other animals was estimated. The following results were obtained: 1. Daily dry matter intake was in a range of 1.0 - 2.2 % body weight (average 0.7; ± 0.1), and intake of digestible energy in a range of 0.5 - 1.0 MJ/kg0.75 metabolic body weight (average 0.8; ± 0.9). Results on apparent digestibility coefficients are as follows: dry matter: 36 - 73 [%] (average 58; ± 8); organic matter: 36 - 74 [%] (average 59; ± 9); crude protein: 40 - 79 [%] (average 60; ± 9); crude fibre: 36 - 48 [%] (average 35; ± 8); calcium: 65 - 90 [%] (average 79; ± 5); phosphorus: 3 - 50 [%] (average 25; ± 10); sodium: -71 - 72 [%] (average 15; ± 36). 2. The concentration of lactate in faeces was on average 1.72 ± 0.4 mmol/l faecal water (n = 32); the concentration of volatile fatty acids in faeces was on average 73.8 ± 15 mmol/l faecal water (n = 32). The ratio of acetate to propionate was on average 3.5 ± 0.8 (n = 32). 3. Faecale particle size distribution decreased with decreasing proportion of roughage. On average, 47.6 % ± 17.2 (n = 22) of all particles retained on the sieves was of a size > 4 mm. 4. The average total water intake was 5.8 kg/100kg body weight ± 1.3 (n = 20). 5. The calcium:creatinine-ration in urine increased with increasing calcium intake. 6. The antioxidative activity increased with added tannin. It was on average 630 ± 162 mmol Trolox Eq/l faecal water for the rations without tannin, 721 ± 159 mmol Trolox Eq/l faecal water for the rations with tannic acid and 1259 ± 193 mmol Trolox Eq/l faecal water for the rations with quebracho. The results on parameters of microbial fermentation, the water intake, the calcium metabolism suggest that black rhinos resemble horses in these aspects of digestive physiology. Differences were evident when apparent digestibility coefficients of crude fibre were compared, which decrease faster in black rhinoceroses with increasing amounts of crude fibre in the ration than in horses. This could be due to a less thorough comminution of ingesta particles and to shorter ingesta retention times in black rhinoceroses. Another difference to the horse concerns sodium metabolism: black rhinoceroses seem to have high faecal losses of sodium. In conclusion, the horse appears to be only to some extent a suitable model animal for black rhinoceros ration evaluation.