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 BW0.75, 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 BW0.75, 37.2 and 157 kJ/g (113 kcal/kg BW0.75, 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 BW0.75, 0.281 and 1.65 g/g, respectively.