Abstract
This study was designed to optimize the diet composition and nutrient uptake of common marmosets (Callithrix jacchus) at the animal husbandry unit, F. Hoffmann-La Roche in Basel, Switzerland, with a particular emphasis on bone health protection. The additional influence of UVB-irradiation on vitamin D status was also examined.
Four groups of animals (n=12/group) each consisting of evenly distributed male and female marmosets between 1 and 4 years old, were subjected to either a standard diet (SD), a SD and UVB-irradiation, a trial diet (TD), or a TD and UVB-irradiation. The SD consisted of marmoset pellets (Kliba 3450, Provimi Kliba AG, Kaiseraugst, Switzerland) and Hill’s Prescription Diet Canine I/d™ (Hill’s Pet Nutrition Inc., Topeka, KS, USA). The TD contained ssniff® Mar meal for marmosets (ssniff Spezialdiäten GmbH, Soest, Germany) supplemented with 17.5% gum arabic (GA) (10% in the basal feed, the rest given in fluid form as a separate meal). Both diets were supplemented with eggs, carrots, raisins, bananas, or apples. Food items were provided in three portions throughout the day. The diets contained comparable nutrient amounts in accordance with the National Research Council3 and vitamin D3 concentrations of 2500 IU/kg (SD) and 2800 IU/kg (TD), respectively. Weight gain, food intake, biochemical markers of bone turnover (bone formation: serum osteocalcin [sOC], serum N-terminal pro-peptide of human pro-collagen type I [sP1NP], bone-specific alkaline phosphatase [bALP]; bone resorption: urinary pyridinoline [uPYD], urinary deoxypyridinolone [uDPD], serum C-terminal crosslinks of human collagen type I (C-telopeptide) [sCTX]), vitamin D3 metabolites (25(OH)D3 and 1,25(OH)2D3), intact serum parathyroid hormone (iPTH), and routine blood biochemistry for general health monitoring were determined at the beginning of the study and then in monthly intervals for a duration of 6 months. Bone mineral density (BMD) was determined by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DEXA) at the beginning and the end of the study. Groups receiving UVB irradiation were exposed to a light source (Ultra-Vitalux® UV-Strahler, Osram AG, Winterthur, Switzerland), claiming to produce UVB wavelengths, for 30 minutes each day.
When compared with the SD groups, the TD groups had significant weight gains and reduced food intakes, sufficient to maintain their significantly higher body weights. Possible nutrient deficiencies due to the reduced food intake of the TD group could be excluded based on the measured serum parameters. All groups showed a decrease in bone turnover rate (with a lower rate for the TD than the SD groups) and decreasing iPTH values. The significant weight gain and lower bone turnover of the TD groups may have been due to better digestion, absorption, and utilization of the diet as a result of the GA supplement. The addition of GA to the diet has been shown to lengthen transit time (allowing for better digestion and absorption of dietary nutrients) in marmosets4 and to increase absorption of volatile fatty acids, increase mineral absorption, and have a trophic effect on large intestinal mucosa in rats2,5. The lack of significant differences in bone turnover between the SD and TD groups can be explained with the two diets evidently fulfilling the nutrient requirements of marmosets. The food fractionation over the course of the day is an important contributing factor as well, underlining the importance of the feeding regimen for bone metabolism. Serum 25(OH)D3 levels showed a rise in all groups and like the 1,25(OH)2D3 values, a decrease in variation in the course of the study. A vitamin D3 intake of 87–55 IU/kg body weight appears sufficient to maintain serum 25(OH)D3 and 1,25(OH)2D3 values in the physiologic range. The role of artificial UV irradiation seemed to be of secondary importance, as no significant differences between groups could be detected. This can be the result of either a too-short exposure to and/or insufficient irradiation in the desired UVB wavelengths. The DEXA and pQCT measurements indicated the TD had a positive influence on BMD. An overlap with growth effects in single animals could not be completely excluded, however, as peak bone density in marmosets is reached at approximately 2 years of age.1
The TD was considered well suited to replace the SD and had a positive influence on bone metabolism and health. Gum arabic appears to be an essential dietary fiber for marmosets and should constitute at least 10% of the provided diet. Particular attention should be paid to food fractionation with a minimum of three meals per day and the basal feed always given as the first food in the morning to secure sufficient nutrient uptake.
Acknowledgments
The authors wish to thank Mr. W. Stamm, Mr. H. Brunner, and Mrs. U. Gerwert for technical assistance and data processing. This study was conducted as part of the thesis of A. Angeliewa currently in progress, toward a doctorate in Veterinary Medicine at the Free University of Berlin, Germany.
Literature Cited
1. Angeliewa, A. 2004. Optimizing the diet of the common marmoset (Callithrix jacchus) with particular emphasis on bone turnover and its monitoring by biochemical and densitometrical means. Doctoral thesis. Free University Berlin, Germany, in press.
2. Annison, G., R.P. Trimble and D.L. Topping. 1995. Feeding Australian acacia gums and gum arabic leads to non-starch polysaccharide accumulation in the cecum of rats. J. Nutr. 125: 283–292.
3. National Research Council, USA. 2003. Nutrient Requirements of Nonhuman Primates. The National Academies Press, Washington, D.C.
4. Power, M.L. and O.T. Oftedal. 1996. Differences among captive callitrichids in the digestive responses to dietary gum. Am. J. Primatol. 40: 131–144.
5. Tulung, B., C. Remesy and C. Demigne. 1987. Specific effect of guar gum or gum arabic on adaptation of cecal digestion to high fiber diets in the rat. J. Nutr. 117: 1556–1561.