ENERGY AND PROTEIN-UTILIZATION FOR MAINTENANCE AND GROWTH OF THAI-NATIVE AND ANGLO-NUBIAN X THAI-NATIVE MALE WEANER GOATS

Twenty-four Thai native (TN), 25% Anglo-Nubian (AN),50% (AN) entire male weaner kids (each eight) (15.7 +/- 0.45 kg BW) were used to compare growth and feed utilisation of these three goat genotypes at four levels of intake (maintenance (M), 1.2 M, 1.4 M and ad libitum). TN kids had lower (P < 0.05) DM and OM digestibility coefficients than did 25 and 50% AN kids. Kids fed ad libitum had higher (P < 0.05) DM, OM, NDF and ADF digestibility coefficients than did kids fed 1.2 M and M intakes. There was no significant main effect of genotype on goat growth rates (g/d and g/kg(0.75)/d), although 50% AN goats fed ad libitum had higher (P < 0.05) growth rates (g/d) than did 25% AN and TN goats given the same level of intake. As expected, growth rates increased as feed intakes increased from maintenance (1.3 g/kg(0.75)/d) to ad libitum (10.0 g/kg(0.75)/d). Linear regression equations combined across genotypes were used to calculate maintenance and growth requirements for energy and protein for these goats. Maintenance energy requirement was 376 +/- 18.5 kJ ME/kg(0.75)/d and the ME requirement for BW gain was 25.9 +/- 2.4 kJ ME/g. Minimum N requirements for maintenance of BW was 4.4 +/- 0.24 g DCP/kg(0.75)/d and requirements for BW gain was 0.204 +/- 0.033 g DCP/kg gain. Results from the present experiment suggest that Thai native and ANXThai native goats have similar protein and energy requirements for growth, and that these values are similar to those reported for other breeds of goats. It is also suggested that the comparatively poor growth of all goats at the highest intake was related to low voluntary feed intakes and probably associated with high environmental temperatures and humidity.