A procedure that mimics washing in the in situ incubation technique, combined with an in vitro gas and volatile fatty acids (VFAs) production technique, was used to verify the assumption that rumen degradation behaviour of material washed out of nylon bags is instantaneous and complete. In a 6 x 4 factorial arrangement of treatments with three replicates, fractions of maize, barley, milo, yellow peas, lupins (a mixture of white and spotted lupins) and round-seeded brown faba beans were subjected to an in vitro incubation technique. Fractions were whole (WHO), non-washable (NWF), insoluble washable (ISWF) and soluble washable (SWF). In a manually operated in vitro fermentation system, another 24 samples of the same substrates were fermented for VFA and ammonia analysis. Except in lupins, ISWF in the concentrate ingredients was very rich in starch. SWF was relatively rich in ash, crude protein, soluble sugars, and a residual unknown fraction but contained only a negligible quantity of starch. Thus, the fermentation characteristics of ISWF were more like WHO and NWF than SWF. Total gas production of SWF was considerably lower than the other fractions. A very rapidly degradable fraction was seen in the first phase of degradation of SWF. The pattern of fermentation end-product formation for SWF differed from that of the other fractions. (C) 2007 Society of Chemical Industry.

The effects of washing procedure, particle size and dilution on the distribution of non-washable (NWF), insoluble washable (ISWF) and soluble washable (SWF) fractions were studied. The effects of three washing procedures (Yang (Y), Melin (M) and in situ (IS)) on the size of NWF, ISWF and SWF in six concentrate ingredients (maize, barley, milo, peas, lupins and faba beans), ground at two different particle sizes, were compared. Method M was further developed (method SM) by reducing the dilution ratio; its effect on NWF, ISWF and SWF was compared. A new washing method was developed (method AA) which involved continuous washing of nylon bags in a centrifuge beaker; its effect on NWF, ISWF and SWF at different dilutions with water was compared with the IS, M, SM and Y methods. The effects of different dilutions on SWF and soluble true protein (STP) in six concentrate ingredients were studied. The effects of grain, washing method and particle size on the size of NWF and ISWF were significant, with significant interactions between grain and particle size, grain and washing method, particle size and washing method, but no interaction between grain type, washing method and particle size. In method Y the size of NWF was smaller than in the other methods. The results showed that, except in lupins, NWF in grains was significantly higher than in legume seeds. Increasing the particle size significantly increased NWF, whereas ISWF was decreased. The size of SWF in legume seeds was higher than in the grains. Increasing the dilution, increased STP in legume seeds, but not in grains. (C) 2007 Society of Chemical Industry.

The N-isotope dilution technique (N-IDT), with either pulse-dose oral administration or continuous i.v. administration of [N]-L-leucine (carotid artery), both at 5 mg/(kg body weight d), was used to measure ileal (postvalve T-cecum cannula) endogenous nitrogen recovery (ENR) in pigs (9 0.6 kg). Diets were cornstarch, enzyme-hydrolyzed casein with no (control) or high (4%) content of quebracho extract (Schinopsis spp.) rich in condensed tannins. Blood was sampled from a catheter in the external jugular vein. Mean plasma N-enrichment at d 8–10 was higher (P 0.0009) after i.v. than after oral administration [0.0356 vs. 0.0379 atom% excess (APE)]. Plasma N-enrichment for i.v. infused pigs was 0.01117 APE higher (P 0.0001) and for orally dosed pigs 0.0081 APE lower (P 0.0001) at 11 h postprandial compared with 1 h postprandial. Apparent ileal N digestibility was higher (P 0.0001) for the control (85.5%) than for the quebracho diet (69.5%). ENR was calculated from the ratio of N-enrichment of plasma and digesta. The ENR for the quebracho diet was 300% higher than for the control diet (6.03 vs. 1.94 g/kg dry matter intake, P 0.001). The real N digestibility (92.2 0.4%) was equal for both diets (P 0.1030) and both tracer methods (P 0.9730). We concluded that oral administration of [N]leucine provides reasonable estimates of ENR in pigs fed semipurified diets with high or low content of tannins; however, one must be careful in extrapolating this conclusion to studies with other protein sources or feeding frequencies. J. Nutr. 134: 3068–3075, 2004.

3 paginas, 2 tablas.-- Trabajo presentado en las IX Jornadas sobre Produccion Animal (AIDA) (Zaragoza, 25 a 27 de abril de 2001). Publicado en un numero especial de la revista ITEA.