Effects of feeding level on nutrient digestibility and enteric methane production in growing goats (Capra hircus hircus) and Sika deer (Cervus nippon hortulorum).

OBJECTIVE: Two experiments were conducted to determine the effects of feeding level on nutrient digestibility and enteric methane (CH4) emissions in growing goats and Sika deer. METHODS: Three growing male goats (initial body weight [BW] of 22.4±0.9 kg) and three growing male deer (initial BW of 20.2±4.8 kg) were each allotted to a respiration-metabolism chamber for an adaptation period of 7 d and a data collection period of 3 d. An experimental diet was offered to each animal at one of three feeding levels (1.5%, 2.0%, and 2.5% of BW) in a 3×3 Latin square design. The chambers were used for measuring enteric CH4 emission. RESULTS: Nutrient digestibility decreased linearly in goats as feeding level increased, whereas Sika deer digestibility was not affected by feeding level. The enteric production of CH4 expressed as g/kg dry matter intake (DMI), g/kg organic matter intake, and % of gross energy intake decreased linearly with increased feeding level in goats; however, that of Sika deer was not affected by feeding level. Six equations were estimated for predicting the enteric CH4 emission from goats and Sika deer. For goat, equation 1 was found to be of the highest accuracy: CH4 (g/d) = 6.2 (±14.1)+10.2 (±7.01)×DMI (kg/d)+0.0048 (±0.0275)×dry matter digestibility (DMD, g/kg)-0.0070 (±0.0187)×neutral detergent fiber digestibility (NDFD; g/kg). For Sika deer, equation 4 was found to be of the highest accuracy: CH4 (g/d) = -13.0 (±30.8)+29.4 (±3.93)×DMI (kg/d)+0.046 (0.094)×DMD (g/kg)-0.0363 (±0.0636)×NDFD (g/kg). CONCLUSION: Increasing the feeding level increased CH4 production in both goats and Sika deer, and predictive models of enteric CH4 production by goats and Sika deer were estimated.