Estimating dry matter digestibility and intake in wapiti (Cervus elaphus canadensis) using the double n-alkane ratio technique

We estimated dry matter digestibility and intake (DMI) in wapiti hinds using the double n-alkane method. We also assessed intra-ruminal controlled-release devices (CRD) for administering n-alkane markers C32 and C36. Nine wapiti hinds were offered alfalfa-based compounded diet for ad libitum consumption and actual DMI was measured daily (mean: 9.2 1.6 kg DM/day). The DMI estimate for C33:C32 (9.4 1.6 kg DM/day, ‡2%) was slightly more accurate (P > 0.05) than that for C31:C32 (9.8 1.8 kg DM/day, ‡6%), whereas C31:C32 was slightly more precise (P > 0.05) than C33:C32 in predicting intake (C31:C32 Ð R 2 ˆ 0.84; C33:C32 Ð R ˆ 0.71). Feed digestibility, estimated using dosed C36, was 63%. Level of intake did not signi®cantly affect n-alkane marker excretion rate, feed digestibility, nor n-alkane fecal recovery (P > 0.05). This offers the advantage of concurrent use of the same CRD for predicting DMI in animals over a range of intakes. The manufacturer's in vitro release rate (58.5 mg/day) was slightly higher than estimates of C32 (52 6) (P < 0.01) and C36 (50 6) (P > 0.05) based on fecal output. There was more variation among days than among animals in excretion rates of C32, but not C36. The double n-alkane ratio technique provides reliable assessment of DMI in wapiti feeding on alfalfa-cubes and may prove useful for determining intake of free-ranging ruminants. Furthermore, CRD eliminate daily dosing, thus minimizing disturbance of normal grazing patterns. # 2000 Elsevier Science B.V. All rights reserved.