Untersuchungen an Degus (Octodon degus) zur Futter- und Wasseraufnahme sowie zur Verdaulichkeit von Nährstoffen bei Angebot unterschiedlicher Futtermittel

The rather incomplete knowledge of the nutritional and digestive physiology of degus, as well as requests from pet owners and veterinarians on species-appropriate or on needs-based supply of feed and water, on the species-typical digestive capacity for crude fibre, on the possible disposition for urolithiasis or diabetes mellitus in sugar-rich feeding caused to the present studies on degus (Octodon degus). Therefore, basic data on feed and water intake, nutrient digestibility (partly compared to that of dwarf rabbit) as well as on the calcium balance were collected in different trial phases while offering different feedstuffs. Furthermore, there was the question whether offering the usual sugar-rich feedstuffs could be expected to have adverse effects on the health of degus (diabetes mellitus). To generate basic data on feed and water intake (trial phase A) adult degus (n/group = 3 - 4) were offered six different feeds (hay, commercial rabbit feed, carrot pulp, husked oat, pears and white cabbage) ad libitum with free access to drinking water (nipple drinkers) on at least five days after a corresponding adaptation period. Collecting data on the nutrient digestibility (trial phase B) eight adult degus in three groups of two or three animals were offered six diets containing rising crude fibre contents (CF) in digestibility trials for five days. For a better evaluation (i. e. comparing the ability of crude fibre digestibility) three dwarf rabbits were also offered simultaneously the same diets over five days. To examine the calcium balance (trial phase C) trials with eight degus took place in special balance cages for a corresponding analysis of the volume and composition of urine. The feed supply consisted of a low-calcium and calcium-rich diet, respectively (for over eight days after a five-day-adaptation). Again aqua dest. was available as drinking water for the animals ad libitum. Furthermore, investigations on volume, composition and quality of urine were carried out by feeding the six diets have already been used in the digestibility trials (trial phase D). Testing the tolerance of sugar-rich feedstuffs, a group of six degus were fed carrots and sugar beets [sugar content: 55 or 75 % on dry matter basis (DM)] over a period of eight weeks as well as giving them water ad libitum. The general condition of the animals was controlled daily and the eyes of each animal were checked continuously for a potential clouding of the lenses. The freshly passed urine was tested for a possible glucosuria over a period of no more than seven days. The main findings are listed below: Basic data on the feed and water intake of degus (trial phase A): · The daily DM intake varied between 2.5 and 5.6 g DM/100 g body weight (bw) or even 6.7 g /100 g bw (hay: 24.5 % CF in DM) offered ad libitum. · When daily DE intake was in the range of ~ 55 - 65 kJ/100 g bw the adult degus could maintain their body weight. · The daily intake of drinking water varied between 1.39 ml/g DM (hay) and 1.92 ml/g DM (husked oat). The intake of fresh feed (pears/white cabbage) was connected to a much higher water intake (8 - 9 ml/g DM). Nutrient digestibility of degus in comparison to dwarf rabbits (trial phase B): · Only from a CF content of > 16 % in DM differences in the digestibility of organic matter between degus and rabbits occurred. · The degus showed a significantly higher digestibility of crude fibre (between 6 - 18 percentage points higher values) than the dwarf rabbits. · The following regression formula can be used to estimate the apparent digestibility of organic matter (app. dig.OM) which depends on the content of the CF in DM: app. dig.OM = 92.7 - 1.64 × (%) (x = CF content in % DM of feed) Mineral balance in degus (trial phase C and D): · At low Ca content in feed apparent Ca digestibility varied by 3.4 %, while values of 66 % were observed at high Ca intake. · At higher values regarding the apparent digestibility of calcium and magnesium, the elimination of surplus quantities was predominantly renal (massive increase of Ca concentration in the urine up to 21.6 mg/ml). · Neither at low nor at high Ca intakes significant quantities of P were excreted via urine (however a generally low P supply existed in an improper Ca : P - ratio). · As known of other animals the elimination of sodium, potassium and chloride happened almost completely renal. · "High concentrated" feed rations resulted in rather lower urinary pH values (O 6.2), while at greater K contents in the feed pH levels increased up to 8.8. · Specific gravity in urine of degus varied from 1028 to 1082. Influence of sugar-rich rations on the health of degus (trial phase E): · A sugar-rich feeding (553 to 753 g sugar/kg DM of feed) of degus over a period of ≤ 8 weeks led neither to the clouding of lenses nor to glucosuria. Conclusions: Compared to the rabbit degus showed a remarkable ability of CF digestibility, which should be seen in the context of the coprophagy (according to older studies up to 38 % of the daily produced amount of feces should be reingested! ). In addition, feeding exclusively hay at moderate CF levels is assumed to be possible. As regards the Ca balance, degus are similar to the rabbit and guinea pig (disposition for Ca containing urinary concrements at high Ca intakes). A sugar-rich feeding over a period of eight weeks had no negative effects in terms of often discussed disposition to nutritional diabetes mellitus in the degu.