Protein and Mineral Digestibility of Three Pelleted Equine Feeds and Subsequent Nitrogen and Phosphorus Waste Excretion1

This experiment was designed to examine the digestibilities of 3 commercially available equine feeds when fed with Bermudagrass hay, and the N and P waste associated with these types of concentrate feeds. The feeds used were a 12% protein pelleted feed produced by 3 different manufacturers. Nine mature Quarter Horse geldings were used in a 3 × 3 Latin square design. The apparent digestibilities for Ca were 39.02%, 25.47%, and 39.00% for feeds A, B, and C , respectively, with apparent Ca digestibilities of feeds A and C significantly higher (P < .05) than feed B. Apparent digestibility of P was greater (P < .009) for feed A (28.65%, compared with feed B (15.63%) and C (16.08%). There were no differences for apparent CP digestibilities (feed A = 71.19%, feed B = 69.39%, and feed C = 68.37%). The apparent digestibilities for K and Mg were similar between feeds. The P and total kjeldahl N (TKN) in manure was similar among treatment groups. The mean urinary excretion of Ca, P, and TKN was similar among feeds. For feeds A, B, and C the TKN results were 1.08%, 1.13 % and 1.10%, respectively. The mean urinary excretion of K and Mg was greater for feed B compared with feeds A and C (P < .05). Data from this study suggest that similar types of equine pelleted feeds may vary slightly in apparent digestibility of nutrients but appear to produce similar amounts of waste products of environmental concern.