THE CHEMICAL-COMPOSITION, DIGESTIBILITY, METABOLIZABLE ENERGY CONTENT AND NITROGEN DEGRADABILITY OF SOME PROTEIN-CONCENTRATES

One sample of copra expeller products, 11 of linseed meal, five of maize germ meal, one of whole maize germ, eight of malt culms, 11 of palm kernel meal, six of rapeseed meal, four of soyabean meal, five of soyabean meal (Brazilian), five of soyabean meal (high protein), two of whole soyabeans and nine of sunflower seed meal were evaluated by energy balance using wether sheep. Nitrogen degradability of a subpopulation of these samples (excluding maize germ, palm kernel and sunflower) was also measured. The crude protein contents of the feedstuffs ranged from 109 to 506 g kg-1 dry matter (DM). The digestible organic matter in the DM (DOMD) measured in vivo were all within the range 721-887 g kg-1, with the exception of sunflower seed meal (586 g kg-1). Crude protein digestibility was highest for the soyabean by-products (0.93-1.00) and lowest for maize germ meal and palm kernel meal (0.72 and 0.75 respectively). Metabolisable energy (ME, MJ kg-1 DM) content of feedstuffs was predicted from a relationship with neutral detergent cellulase (NCD, g kg-1 OM) and acid ether extract (AEE, g kg-1 DM) as independent variables: ME=0.0146NCD+0.0232AEE (RSD=1.51) The residual standard deviation (RSD) was reduced when the palm kernel meal samples were excluded: ME=0.0148NCD+0.0166AEE (RSD=0.86) Nitrogen degradability at an estimated rumen outflow of 0.08 h-1 ranged from 48% to 75% with the soyabean by-products having the lowest values and rapeseed meal the highest values.