NITROGEN UTILIZATION AND THE REQUIREMENTS FOR MAINTENANCE OF KEDAH-KELANTAN CATTLE

C. DEVENDRA

SUMMARY

Nitrogen (N) utilization and the requirement for maintenance was studied in adult Kedah-Kelantan cattle, six to seven years of age with a mean live weight of 321 kilogrammes. Nine diets were fed consecutively to nine bulls in which dietary energy was held constant and 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20% and 22% dietary crude protein (CP) levels were included. A six per cent crude protein level was barely adequate to promote dry matter intake (DMI); increasing higher dietary crude protein levels increased DMI by between 30% and 59% significantly (P<0.01) . Associated with the increasing dietary crude protein levels and higher DMI , were statistically significant increased N balance ( P<0.01) . The positive nitrogen balances were,however,lower than that in similar studies in swamp buffaloes due to a lower urinary nitrogen output (UNO) in the latter. The true N digestibility was 89.3% while the mean biological value (BV) was 77.5 per cent. Correlation matrices between nitrogen intake (NI), faecal nitrogen output (FNO), urinary nitrogeno utput (UNO), apparently digestible N (ADNI), N balance (NB) and dietary N content (DNC) indicated that statistically significant correlations (P<0.01) only existed between all variables excepting FNO and UNO, ADNI and DNC and between NB and DNC; the highest correlation was r = 0.95 between NI and ADNI. The endogenous urinary N (EUN) was 39.1 mg/kg live weight/day and the metabolic faecal nitrogen (MFN) was 0.220 g/100g DMI. The digestible crude protein (DCP) requirement for maintenance calculated from the relationship between NB and ADNI as well as by the factorial method gave a mean value of 1.37 g DCP/W^0.75kg/day, this value is discussed in relation to other published reports in the tropics.

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