Prediction of metabolizable energy and protein requirements for maintenance, gain and fiber growth of Angora goats

A database was constructed for growing and mature Angora goats to estimate metabolizable energy (ME) and protein (MP) requirements for maintenance, whole BW gain (ADG), non-fiber tissue gain (TG) and fiber growth (clean fiber growth rate; CFGR). MP intake (MPI) was calculated from CP degradability properties and dietary proportions of feedstuffs. Variables, scaled by BW^0.75, consisted of mean BW (kg), ME intake (MEI; kJ per day), MPI (g per day), ADG (g per day), TG (g per day; i.e., ADG corrected for grease fiber) and CFGR (g per day). For ME, the final simple regression equation for mature goats was MEI=533 (SE=18.8)+(43.2 (SE=4.77)×ADG) (n=77;R²=0.52). The final multiple regression equation for mature goats was MEI=473 (SE=49.85)+(37.2 (SE=6.97)×TG)+(157 (SE=52.5)×CFGR) (n=48;R²=0.53). For MP, the final simple regression equation with a development data set for growing and mature goats was MPI=4.30 (SE=0.286)+(0.318 (SE=0.0471)×ADG) (n=68;R²=0.41), which resulted in unbiased prediction of MPI in an evaluation data set. The final multiple regression equation for growing and mature goats was MPI=3.35 (SE=0.440)+(0.281 (SE=0.0486)×TG)+(1.65 (SE=0.394)×CFGR) (n=83;R²=0.46). In conclusion, ME requirements of mature Angora goats for maintenance, TG and CFGR were 473 kJ/kg BW ^0.75, 37.2 and 157 kJ/g (113 kcal/kg BW^0.75, 8.89 and 37.5 kcal/g), respectively. MP requirements of growing and mature Angora goats for maintenance, TG and CFGR were 3.35 g/kg BW^0.75, 0.281 and 1.65 g/g, respectively.