Digestibility and nutrient retention of perennial peanut and bermudagrass hays for mature horses

Mature horses were used to determine apparent DM, OM, NDF, and CP digestibility values of 2 bermudagrass (BG; Cynodon dactylon) hays, Coastal (CB) and Tifton 85 (T85), and Florigraze perennial peanut (PP; Arachis glabrata) hay. In addition, N, Ca, and P balances were determined in horses fed those hays. Five mature Thoroughbred geldings and 1 Quarter Horse gelding (mean initial BW = 542 +/- 37 kg) were used (5 horses for the last period) in a 3 x 3 repeated Latin square design, with 2 horses per hay and 3 adjustment and collection periods. Horses were randomly assigned to pairs and the initial hay to be fed. Each period consisted of a 10-d adjustment phase, followed by a 4-d total fecal and urine collection phase. Horses were fed at 1.5 (period 1), 1.7 (period 2), or 2% (period 3) of their BW daily (DM basis). The 2 BG were grown under similar conditions, with CB and T85 being cut at 4 and 5 wk of regrowth, respectively, and PP being of a late first cutting. The compositions (DM basis) of PP, CB, and T85, respectively, were 93, 94, and 93% DM; 92, 94, and 94% OM; 46, 73, and 77% NDF; 34, 37, and 42% ADF; 11, 10, and 8% CP; 1.10, 0.28, 0.27% Ca; and 0.19, 0.15, and 0.19% P, respectively. Least squares means (pooled SE) for apparent digestibility of PP, CB, and T85, respectively, were 65, 53, and 52% (1) DM digestibility; 67, 53, and 52% (1) OM digestibility; 44, 50, and 46% (4) NDF digestibility; and 66, 60, and 57% (1) CP digestibility. Digestibility values of DM and OM were greater (P < 0.001) for PP than for the BG. Digestibility of CP was greater (P = 0.001) for PP than for CB or T85, with no difference (P = 0.37) between PP and BG hays in NDF digestibility. There were no differences between CB and T85 for DM digestibility (P = 0.67), OM digestibility (P = 0.59), CP digestibility (P = 0.11), and NDF digestibility (P = 0.48). Nitrogen (P = 0.01) and P balances (P = 0.04) were greater for PP than BG hays, whereas N balance of CB was greater (P = 0.01) than that of T85. There were no differences among all hays in Ca balance (P = 0.54) and between the BG in P balance (P = 0.34). Results indicated that PP, CB, and T85 are suitable forages for horses.