In order to establish the main composition factors of a series of protein sources (beans, sunflower cake, corn gluten feed and cottonseed), affecting the milk protein production in goats, the ruminal degradation of these feeds was studied. Four diets were designed differing in that 20 per cent of their protein was supplied by each of the different sources. Four groups of five Granadina breed goats were used to study the utilization of these diets for milk production. No significant differences were observed between dry matter intake rates and amounts of milk produced. The milk produced with the sunflower cake diet had the lowest protein concentration while the highest milk protein concentration corresponded to the corn gluten diet. By means of a multivariate analysis different and independent patterns for behaviour were observed for the rumen undegradable protein, quick rumen degradable protein and slow rumen degradable protein for the protein sources.