Paengkoum et al., 2006. Asian-Aust. J. Anim. Sci., 19 (9): 1305-1313

This study was conducted to determine the effects of varying amounts of urea supplementation on performance and feed utilization on growing dairy goats fed with steamed oil palm fronds (OPF). Five male dairy goats (Saanen), 4.6 month old with a body weight of 21.4 (SD1.6) kg, were used to examine 5 dietary urea treatments in a 5*5 Latin Square experimental design. The five levels of urea were 10, 20, 30, 40 and 50 g urea/kg DM of OPF and dry matter intake tended (p>0.05) to increase with increasing urea supplementation up to 30 g/kg OPF (77.7 g/kg BW 0.75), but decreased (p<0.05) with 40 and 50 g urea/kg OPF (67.4 and 63.7 g/kg BW 0.75, respectively) supplementation. Similarly, dry matter, organic matter, crude protein, neutral detergent fibre and hemicellulose digestibilities increased (p<0.05) with the addition of urea to 30 g/kg OPF but thereafter, decreased (p<0.05) with 40 and 50 g/kg OPF. Rumen pH, rumen NH 3-N concentration and plasma urea concentration increased linearly (p<0.01) and quadratically (p<0.01) as a consequence of addition of urea to the diet. Excretion of total purine derivatives (PD) by goats fed 30 g of urea/kg OPF was highest (p<0.05) followed by goats fed with 20, 40, 10 and 50 g of urea/kg OPF. Microbial N (g N/day) and efficiency of microbial N supply expressed as g N/kg organic matter apparently digested in the rumen were higher (p<0.05) in goats fed 30 g of urea/kg OPF (5.5 g N/day and 22.0 g N/kg DOMR, respectively) than in goats on 10 and 50 g of urea/kg OPF treatments. However, the former did not differ from goats fed 20 g of urea/kg OPF (3.9 g N/day and 16.6 g N/kg DMOR, respectively). Rumen VFA concentration, protein/energy ratio, N absorption and N retention increased (p<0.05) with the addition of urea to the diet up to 30 g/kg OPF but decreased (p<0.05) with 40 and 50 g/kg OPF. It is concluded that the optimum level of urea supplementation in an OPF based diet is ~30 g urea/kg OPF.