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This study evaluated the differences in the gas produced by Sesbania accessions and related gas production to macro-constituents and tannin content of the browse species. Fresh samples were incubated in triplicate (about 200 mg per syringe) in a medium prepared from sieved rumen liquor harvested from two rumen-fistulated cows fed native pasture hay ad libitum and 2.0 kg cottonseed cake per head per day. Sesbania species had similar rates of gas production but differed (P < 0.001) in the volume of gas produced. The ranking order for gas production was S grandiJora > S sesban > S keniensis > S goetzei. There was little variation in the gas production parameters within S grandiyora and S goetzei. But the variation was large within S sesban. Regression analysis showed that the rate of gas production was negatively affected (P < 0.025) by the lignin content of the browses, but the volume of gas produced was negatively related to the neutral detergent fibre, hemicellulose, lignin and insoluble proanthocyanidins content of browses. Cluster analysis showed a broad agreement between gas production constants, macro-constituents and tannin contents in classifying accessions into high or low nutritive value groups.

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1992). Effect of feeding frequency on diurnal variation in plasma and urinary purine derivatives in steers. AbstractThe diurnal changes in plasma concentration and urinary excretion of purine derivatives (PD) were examined in four steers given their food in either one or two meals daily in two 18-day periods. In period 1, two steers were fed once daily (at 08.00 h) and the other two twice daily (at 08.00 and 16.00 h). In period 2, the treatments were switched. In the last 4 days of each period, plasma samples were taken from 08.00 to 24.00 h at 2 to 3 h intervals, and daily urine was collected in several 4 to 8h periods. With once daily feeding, allantoin concentration in plasma varied from 090 to 1-07 of the daily mean and with twice daily feeding, from 0-97 to 1-05 of mean. The coefficient of variation (CV) for total variation was 0-14. In urine, the concentration and hourly excretion of PD varied with sampling times (P < 0-05) but the ratio of PD to creatinine was relatively constant even for once-daily feeding (CV, 0-02 for measurements at different times). The CV for total variation in the ratio was 0-19. The results suggest that diurnal variation in plasma allantoin concentration and in the ratio of allantoin (or total PD) to creatinine are relatively small even for once daily feeding. It thus seems that these measurements in spot samples may be suitable for use as a simple index of microbial protein supply if they are correlated with the daily PD excretion. The results also indicate that measurements in samples of plasma and urine taken between 15.00 and 20.00 h tended to give a better representation of the daily mean.

1. Measurements were made of portal blood flow, heat production and oxygen consumption in the digestive tract of sheep either fasted or given the following diets: chopped, dried grass; pelleted, dried grass; chopped, dried lucerne; pelleted, dried lucerne; or a pelleted baley diet.2. For sheep that had been fasted for 48 h, portal blood flow was 1.84 1/min, total visceral heat production was 62.3 kJ/kg body-weight0.75 per 24 h and aerobic heat production, estimated from oxygen consumption, was 62.1 kJ/kg body-weight0.75 per 24 h.3. Portal blood flow was markedly influenced by food intake, increasing from 1.8 1/min for starved sheep to 2.4 and 4 1/min for sheep fed at maintenance and 2.5 × maintenance levels of intake respectively. Variations in the quality and physical form of the diets had no apparent effect on portal blood flow.4. There was a curvilinear relationship between total heat production in the gut and metabolizable energy (ME) intake. The increase obtained for levels of intake below maintenance was greatest with lucerne diets, and least with pelleted, dried grass or pelleted barley diets. Above maintenance levels of intake the rate of increase in heat production, with all diets, was about 150 kJ/MJ ME intake.5. The heat of fermentation, estimated from the difference between total visceral metabolism and the aerobic metabolism of the tissues of the gut wall, was 76, 60 and 22 kJ/MJ digestible energy intake for the dried grass, lucerne and barley diets respectively.6. The contribution of fermentation heat and the aerobic metabolism of the gut to the total heat increment of feeding in sheep was assessed. It was concluded that about half the heat increment must be derived from tissues outside the digestive tract.

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