The aim of the experiment was to study diurnal variation in water-soluble carbohydrate (WSC) concentrations in leaf and stem of tall fescue and lucerne in autumn and to determine the impact of these changes on the rate and the extent of in vitro fermentation. Vegetative herbage of lucerne and tall fescue were sampled at 0900, 1300 and 1700 h, following three consecutive regrowths between April and May. Whole plants, leaf and stem were analysed for chemical composition and in vitro gas production. There was a linear increase in WSC throughout the day for all plants and plant components (P < 0.001). In both fescue and lucerne, this rise resulted in an increased rate of gas production, although this relationship was more pronounced in fescue. Use of time of day to govern grazing management decisions to potentially improve the rumen supply of WSC and nitrogen in autumn can be achieved from tall fescue or lucerne pastures.

Fermentation kinetics, digestibility, faecal characteristics and bacterial populations (aerobes, anaerobes, lactobacilli, lactic acid bacteria, enterococci, coliforms and clostridia) of dog food mixed with citrus pulp and apple pomace were evaluated. The in vitro gas production of a pre-digested dog food mixed with 0, 30, 50 and 70 g/kg dry matter (DM) of citrus pulp or apple pomace was measured, and also an experiment with dogs fed the same dog food with or without the addition of 70 g/kg of either fresh citrus pulp or apple pomace was conducted. Gas production increased linearly (p < 0.001) and quadratically (p < 0.001) as fibre levels augmented. The inclusion of fibre sources in the diets resulted in higher faecal output (p =0.005) and defecation frequency (p < 0.001), and lower faecal pH (p < 0.001) and digestibility values (p < 0.01). Faecal consistencies and microbial populations did not differ among treatments. The addition of fresh citrus and apple was effective to stimulate the hindgut fermentation, but slightly depressed the digestion.

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-The aim of the present study was to compare the amount of microbial N entering the duodenum and the efficiency of N utilisation for microbial protein synthesis in normal (NP, 17.4 g N/d) and low protein (LP, 7.5 g N/d) fed Corriedale sheep. Renal functional tests for urea handling studies, and determination of urinary allantoin as an indirect method to estimate the microbial protein production were used. Although the N intake was 57% lower in LP sheep, the microbial N production was not very different between both diets (NP: 3.99 ± 0.01 vs. LP: 3.79 ± 0.02 g/d, P < 0.05). The efficiency of the microbial protein synthesis in the rumen, expressed as grams of microbial N per kg of digestible organic matter apparently digested in the rumen, was not statistically different for both diets. The urinary elimination of urea was reduced by 84% in LP sheep, essentially due to an important decrease in both renal plasma flow (-63%) and glomerular filtration rate (-71%). These haemodynamic changes would also reduce the filtered load and the urinary elimination of allantoin, thereby leading to an underestimation of the amount of microbial protein entering in the duodenum. Since the renal urea spared by the kidneys remains in the blood, it limits the drop of the available urea for ruminal recycling consecutive to a low nitrogen diet. (NP,17,4 g N/j) ou hypoprotéique (LP, 7,5 g N/j). Des tests de fonctionnement rénal pour étudier les transferts d'urée, et le dosage de l'allantoïne pour estimer la production de protéine microbienne ont été utilisés. Malgré une ingestion d'azote réduite de 57% chez les moutons LP, la production d'azote microbien n'a pas été très différente entre les deux régimes (NP: 3,99 ± 0,01 vs. LP: 3,79 ± 0,02 g/j, P < 0,05). L'efficacité de la synthèse protéique microbienne dans le rumen, exprimée en grammes d'azote microbien par kg de matière organique apparemment digérée dans le rumen, n'a pas été statistiquement différente dans les deux régimes. L'élimination urinaire d'urée a été réduite de 84% chez les moutons LP, grâce essentiellement à une importante diminution du débit plasmatique rénal (-63%) et de la filtration glomérulaire (-71%). Ces modifications hémodynamiques réduisant également la charge filtrée et la quantité d'allantoïne éliminée, peuvent être responsables d'une sous estimation de la quantité de protéine microbienne entrant dans le duodénum. L'urée épargnée au niveau rénal restant dans le sang, limite la baisse de l'urée disponible pour le recyclage dans le rumen, observée lors des régimes pauvres en azote.protéine microbienne / allantoïne / urée / mouton

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