Milk Composition in Free-Ranging Polar Bears (Ursus maritimus) as a Model for Captive Rearing Milk Formula

The goals of this study were to have an improved understanding of milk composition and to help create a suitable milk formula for cubs raised in captivity. Milk samples were evaluated for fat, fatty acids, carbohydrate, vitamin D-3, 25(OH)D-3, vitamin A (retinol), vitamin E (alpha-tocopherol), protein, and amino acids. Total lipids in milk did not differ for cubs (mean +/- SEM = 26.60 +/- 1.88 g/100 ml vs. yearlings 27.80 +/- 2.20 g/100 ml). Milk lipids were of 23.6% saturated fatty acid for cubs and 22.4% for yearlings. Milk consumed by cubs and yearlings contained 43.8 and 42.0% mono-unsaturated fatty acids and 23.4 and 21.9% polyunsaturated fatty acids, respectively. Carbohydrate content was higher in milk for cubs (4.60 +/- 0.64 g/100 ml) than for yearlings (2.60 +/- 0.40 g/100 ml). Vitamin D-3 concentration of milk was 18.40 +/- 5.00 ng/ml in early lactation compared with 7.60 +/- 2.00 ng/ml for mid-lactation. 25(OH)D-3 was lower in milk consumed by cubs (162.00 +/- 6.70 pg/ml) than in milk consumed by yearlings (205.00 +/- 45.70 pg/ml). Vitamin A concentrations were 0.06 +/- 0.01 and 0.03 +/- 0.01 mg/ml for cubs and yearlings, respectively. Vitamin E was higher in milk consumed by cubs (20.16 +/- 4.46 mu g/ml) than by yearlings (7.30 +/- 1.50 mu g/ml). Protein content did not differ in milk available to cubs (11.40 +/- 0.80 g/100 ml compared with milk for yearlings 11.80 +/- 0.40 g/100 ml). Taurine was the most abundant free amino acid at 3,165.90 +/- 192.90 nmol/ml (0.04% as fed basis). Zoo Biol 30:550-565, 2011. (C) 2011 Wiley Periodicals, Inc.