Different protein-energy ratios in feedlot diets may effect several combinations of amounts of amino acids and glucose available for absorption in the small intestine. ln this regard, the effect of protein concentration and degradation, and energy content of the diet were studied in two 4 x 4 Latin Square trials with ruminal and duodenally fistulated steers. In the first trial, steers were fed diets containing 10.0 MJ ME/kg DM at two protein concentrations (105and 125 g CP/kg DM), each attwo

more »

... en degradation levels (60 and 70% RDP). In the second, the dietary energy contentwas 12.5 MJ ME/kg DM, thetwo protein concentrationswere 135 and 155 g CP/kg DM and the two RDP levels were also 60 and70o/o. Theprotein-energy ratio was the same for both energy levels. All diets were fed at a level of 100 g air dry feed/kg \ P/c/d. An increase in N intake increased NAN passage and apparent absorption in the lower digestive tract. RDP level did not have a significant effect on NAN passage. The percentage OM that apparently fermented in the rumen (OMDR) was negatively associated with NAN passage. OMDR was lower on the higher energy diet; the difference being mainly due to the difference in starch digestion. Proportionally less starch was digested in the rumen and more in the lower digestive tract with the higher energy diet, i.e. the higher starch diet. Results indicate that ratios of amino acids and glucose available for absorption from the small intestine vary independently of the dietary protein-energy ratio. Voerkraaldi€te met verskillende proteien-energieverhoudings kan lei tot verskillende kombinasies van aminosure en glukose in die dunderm. Omstandighede wat tot gunstige verhoudings lei behoort ondersoek te word, en gevolglik is in hierdie studie proteieninhoud en -degradering tesame met energie-inhoud van die dieet gevarieer. Rumen-en duodenaal gefistuleerde osse is gebruik in 'n eksperimentele ontwerp van twee 4 x 4 Latynse Vierkante. In die eerste proef is 'n energie-inhoud van 10.0 MJ ME/kg DM teen twee proteienkonsentrasies (105 en 125 g RP/kg DM), elk teen twee rumendegradeerbaarheidspeile (60 en 70% RDP) gevoer. ln die tweede proef is die energie-inhoud verhoog na 12.5 MJ ME/kg DM, die proteTenkonsentrasie na 135 en 155 g RP/kg DM, tenrvyl die RDP-waarde gehou is op 60 enTOo/o. Dit het beteken dat die proteien-energieverhouding in die twee proewe dieselfde was. Alle di6te is gevoer teen'n peil van 100 g lugdro€ voer/kg \ p75ld.'n Toename in N-inname het NAN-vloei en skynbare absorpsie uit die laer spysverteringskanaal verhoog, maar RDP-peil het nie'n betekenisvolle invloed op NAN-vloei gehad nie. Die persentasie OM wat skynbaar in die rumen verteer het (OMV*) was negatief gekorreleerd met NAN-vloei. Dit was ook laer op die hod energiedieet, hoofsaaklik as gevolg van 'n verskil in styselvertering. Verhoudelik is minder stysel in die rumen en meer in die laer spysverteringskanaal in die geval van die hod energiedieet, dit is die ho€r styseldieet, verteer. Die resultate dui daarop dat die verhouding tussen aminosure en glukose in die dunderm onafhankik van die dieetproteTen-energieverhouding varieer.