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The effects of constant temperatures on growth, food efficiency, and physiological status were studied in four different batches of juvenile turbot. The growth responses were studied in three experiments lasting 70–85 days under 8–20° C thermal conditions. There was a positive correlation between growth and temperature from 8 to 17° C and a plateau was observed from 17 to 20° C. In fish fed to satiety, specific growth rate was positively correlated to the food intake, which was double at 20° C, compared with 8° C. Minor changes were observed in food efficiency. Body fat deposition decreased as temperature increased (25% lower at 20° C, compared with 8° C). Apparent food conversion, PER (protein efficiency ratio) and PUC (protein utilization coefficient) ranges were 0.8–0.9, 2.1–2.3 and 33–38% respectively. In 70–300 g fish, routine MO2 increased (2.5–6.5 μmol O2 h−1 g bw−1) with temperature up to 20° C, while larger turbot (500–600 g) appeared relatively thermo-independent, with a lower oxygen consumption (1.5 imol h−1 g−1). The average daily total ammonia nitrogen (TAN) and urea-N excretion per fish biomass was positively related to temperature. TAN was 30% lower at 8° C, compared with 20° C. Ingested nitrogen was mainly excreted under the final form of TAN, urea-N representing 26% of the total amount. A post-prandial peak in TAN and a delayed peak in urea-N nitrogen were observed. The hydromineral status [osmolarity, sodium, chloride and potassium blood plasma, gill (Na+-K+)-ATPase activity] of turbot was not affected by progressive changes in temperature during the acclimation period. Juvenile turbots show remarkable homeostatic capacities and so they have a relatively thermo-independent physiology within the range of temperature studied.

To assess the influence of clay minerals and soil pH on the degree of soil suppressiveness, 25% ( w w ) kaolinite, Ca-montmorillonite and illite were added to a fusarium wilt-conducive soil (loam, pH 4.0) and 3 values of soil pH (pH 4.0, 5.0 and 7.0) were obtained by liming. The soil-clay mixtures were sown with wheat; after 6 and 30 weeks, respectively, of wheat growth, soil samples were taken. Their levels of suppressiveness to fusarium wilt of flax were assessed and several characteristics of the soil microflora were determined. After 6 weeks of wheat growth, the addition of either montmorillonite or illite significantly increased the degree of soil suppressiveness to fusarium wilts, but only at pH 7. Neither liming alone nor the addition of kaolinite, with or without lime, had an effect. After another 6 months of wheat growth, the level of suppressiveness had increased in all amended soils. The strongest effect was obtained when kaolinite, montmorillonite or illite was added and the soil pH was raised to 7. The level of soil suppressiveness was correlated with physicochemical characteristics (texture, pH, exchangeable Ca and Mg and EDTA-extractable iron), and biological characteristics (population densities of bacteria, fluorescent pseudomonads and autochtonous Fusarium oxysporum, and the induced respiration of the soil microflora after glucose supply). The results are discussed in relation to the common hypotheses related to factors and mechanisms involved in soil suppressiveness to fusarium wilts.

Intestinal transport of nutrients coincides with their partial catabolism in the gut. The aim of the present study was to measure intestinal oxygen consumption and nutrient metabolism after a meal or during a short fast. Nutrient and oxygen balances across the small intestine were measured in conscious 50 kg (live wt) pigs. Jejunal enterocytes were also isolated from 1-hr postprandial, postabsorptive, or 3-day fasted pigs, in order to evaluate their capacities to metabolize 5 mM glucose and 2 mM glutamine. Whatever the nutritional state, intestinal oxygen consumption was high, since 26 +/- 2% (n = 6) of the oxygen arterial supply was extracted by the small intestine. Furthermore, the consumption of a mixed meal induced a rapid and transient rise in oxygen consumption. In the postabsorptive state, the intestinal uptake of glucose (0.31 +/- 0.08 mmole/min, n = 6) was twice higher than that of glutamine. The role of glucose as a fuel was also evidenced after a 3-day fast. During nutrient absorption, glutamine was highly utilized, and lactate was produced. The capacity of enterocytes isolated from fed pigs to metabolize glucose was dramatically reduced, as was 6-phosphofructo 1-kinase activity. In contrast, intestinal muscle presented a high glycolytic capacity from glucose, suggesting that the main site of intestinal lactate production during nutrient absorption would be the muscular rather than the epithelial layer.

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