The objective of this trial was to determine the intestinal digestibility of nutrients using an in vitro three-step enzymatic procedure. Eight concentrate feeds were evaluated: whole sunflower (WSF), mechanically pressed sunflower cake (SFC1x; one press extraction), mechanically pressed sunflower cake (SFC2x; two press extractions), whole soybean (WSB), partially degreased soybean (DSB), soybean meal (SBM), degreased corn germ meal (CGM), and a commercial concentrate with 36% of CP (CC). Feeds were incubated in the rumen of bovines for 33, 20 and 12 hours corresponding approximately to the rates of passage of 3, 5 and 8%/h, respectively. The ruminal undegradable residues were digested with a 1.9 pH-pepsin solution for one hour at 38ºC followed by a second digestion with a 7.8 pH-pancreatin solution for 24 hours also at 38ºC. The residues were then analyzed for total nitrogen, dry matter, and organic matter. The in vitro intestinal digestibilities of ruminal undegradable DM, protein, and organic matter assuming a rate of passage of 5%/h ranged from 7.88 to 37.72%, 13.67 to 81.76%, and 7.93 to 37.14%, respectively. Commercial concentrate and WSB showed the greatest dry matter and organic matter digestibilities. Crude protein digestibility was highest on CC and SBM and lowest on WSF. Organic matter digestibility also was lowest on WSF. The lowest values of digestible ruminal undegradable protein (RUP D) were observed on both sunflower cakes (SFC1x and SFC2x) suggesting that these feeds should not be used in diets of animals with high requirements of RUP D.
concentrate; corn germ meal; soybean meal; sunflower; whole soybean; sunflower cake
