ORIGINAL A RTICLE Evaluation of fasting metabolism of growing water buffalo (Bubalus, Bubalis)

The objectives of the present study were to evaluate fasting metabolism (FM) of water buffalo (Bubalus, Bubalis) at three stages of growth (12, 18 and 24 months) in Guangxi, China. Five female water buffalo were used for each age group and their live weight was on average 254, 326 and 338 kg, respectively. All animals were of average body condition, healthy and de-wormed before start of the study. Prior to a 6-day fasting period, buffalo were offered a mixed diet of forage and concentrates (70% and 30%, dry matter basis) on a restricted nutritional level (419 kJ/kg 0.75 of metabolizable energy, ME) for 15 days. Gas exchanges for each animal were determined for 3 days from day 4 of starvation, using open-circuit respiratory head hoods. Fasting body weight was 0.918 of live weight (P < 0.001, r 2 = 0.99). Both fasting heat production (FHP) and FM (MJ/day) increased significantly with increased age of animals (P < 0.05). Linear regression analysis indicated a positive relationship between fasting body weight (kg 0.75 ) and FHP (MJ/day, P < 0.01, r 2 = 0.49) or FM (MJ/day P < 0.01, r 2 = 0.52) when using individual animal data across three groups. However, when expressed as kJ/kg 0.75 of fasting body weight, the differences in FHP or FM between three groups of animals were not significant. The present average FHP and FM (322 and 347 kJ/kg 0.75 of fasting body weight) were compatible to those published in the literature for water buffalo, beef and dairy cattle. The present FM data were also used to estimate net energy (NEm) and ME (MEm) requirements for maintenance for water buffalo. The results for these two parameters were similar to those for FHP and FM. There was no significant difference between three groups of buffalo in NEm or MEm when expressed as kJ/kg 0.75 of live weight. The present average NEm and MEm values (347 and 506 kJ/kg 0.75 of live weight) are close to those proposed by the Agricultural and Food Research Council adopted in UK for beef and dairy cattle. The results indicate that the present FM data can be used as a basis for rationing water buffalo in China.