1. The effects of vitamin D3 (D3) on serum levels of 1, 25-dihydroxyvitamin D3 (1, 25(OH)2D3), ionic calcium, total Ca and phosphorus in chicks were studied from the time of hatching until sexual maturity.

2. Chicks fed on a diet low in D3 showed a serum level of 1, 25(OH)2D3 higher than that in chicks on a normal-D3 diet, for both sexes and at any given age.

3. A dramatic increase in the serum level of 1, 25(OH)2D3 occurred in female birds approaching sexual maturity and in laying hens raised on the low-D3 diet the level was five times that of their counterparts raised on a normal-D3 diet.

4. Theserum 1, 25(OH)2D3levelin adultmalesin thelow-D3groups wasseven timesthatofthoseon thenormal-D3 diet.

5. The serum level of 25-hydroxyvitamin D3 remained relatively unchanged at weeks 2 and 15 in birds on a low D3 intake as well as in those fed on a normal-D3 diet. Nevertheless, the levels of 25-hydroxyvitamin D3 were different between the two groups.

6. No significant change was observed in the level of ionized serum Ca in relation to dietary regimen, but there was an increase in total Ca concentration in females with the onset of reproduction.

7. The serum P level decreased gradually with age, reaching a minimum value 3 and 8 weeks before laying commenced in the groups on low- and normal-D3 diets respectively. An increase was observed when the hens began laying.

8. Chicks adapted to a low-D3 diet by elevation of their plasma level of 1, 25(OH)2D3. The mechanism by which this is achieved is not known, but the results suggest that parathyroid hormone, Ca and P are unlikely to play roles in the adaptive increase in the level of 1, 25(OH)2D3 in the blood of chicks given a minimal amount of D3. The possibility that the rate of degradation of 1, 25(OH)2D3 is greatly reduced under these conditions cannot be excluded and this could account for the level of this metabolite in those birds.

1. Groups of rainbow trout (Salmo gairdneri; mean weight 5 g) were given diets containing 10, 12, 14, 17, 21, 24 and 26 g lysine/kg diet for 12 weeks.

2. By analysis of the growth values the dietary requirement of lysine in this experiment was found to be 19 g/kg diet. A similar requirement value was obtained from a dose-response curve of expired 14CO2 (following an intraperitoneal injection of L-[U-14C]lysine) v. dietary lysine concentration.

3. Liver concentrations of total lipid and carnitine and activities of lysine-α-ketoglutarate reductase (saccharopine dehydrogenase (NADP+, lysine-forming), EC 1. 5. 1. 8 ) in the liver were not significantly different in fish from the different dietary treatments. Hepatosomatic index, however, was higher in those fish given low levels of dietary lysine.

1. Investigations were carried out to establish the total biopotency of the natural vitamin E isomers in barley compared with that of DL-α-tocopheryl acetate.

2. The chick was used as an experimental animal. Prevention of nutritional encephalomalacia (NE) and chick liver-storage and plasma-storage assays of vitamin E were the methods used in the study. The individual tocopherols and tocotrienols, both in the tissue samples and in the grain and barley oil, were analysed using high-pressure liquid chromatography (HPLC) with fluorescence detection. The diagnosis of NE was based on careful clinical and histopathological observations.

3. It can be concluded from the results that full protection against NE in the chicks was obtained with a supplementation level of 7.5 mg DL-α-tocopheryl acetate/kg diet (i.e. a total vitamin E content of 11.20 mg/kg diet) or with a supplement of 8.7 g barley oil/kg diet (i.e. a total vitamin E content of 22.99 mg from barley oil/kg diet). This gave a biopotency factor of 0.49 for barley for prevention of NE of the chicks, as compared to that of DL-α-tocopheryl acetate.

4. Using regression analysis a statistically linear relationship could be observed between the total dietary vitamin E level and the response, as measured by the total vitamin E content in the liver and plasma, both in the groups supplemented with DL-a-tocopheryl acetate and in the groups supplemented with corresponding amounts of vitamin E in barley oil. The liver and plasma responses to the total vitamin E in the barley-oil diet compared with those of the DL-a-tocopheryl acetate reference diet gave identical values for the regression coefficients, i.e. in both liver-storage and plasma-storage assays the value for slopes of dose-response lines was 0.37. This means that the biopotency of the total vitamin E in barley was 37% of that of dietary DL-a-tocopheryl acetate. Thus, barley is not as rich a source of vitamin E as could be supposed on the basis of the chemical determination of its total vitamin E content.

5. It was possible to verify this experimentally established biopotency of 0.37 for the total vitamin E in barley by converting the chemically determined amounts of the vitamin E isomers in barley into DL-α-tocopheryl acetate equivalents by multiplying them with internationally accepted potency factors for the individual natural isomers (DL-α-tocopheryl acetate 1.00, D-α-tocopherol 1.49, D-β-tocopherol 0.60, D-gamma;-tocopherol 0.1 5, D-α-tocotrienol 0.37).

6. In spite of the high proportion of α- and β-tocotrienols in the barley-oil diets (about 60% of the total vitamin E content), only traces of these isomers could be detected in the plasma and none could be detected in the liver. On the other hand, calculation of the individual hiopotencies for the different isomers in the barley-oil diet by comparing the dose responses, diet: liver, separately for each isomer with those of DL-α-tocopheryl acetate, resulted in biopotency values for α- and β-tocopherol which were twice as high as the internationally accepted conversion factors. These results of the present study tempted the authors to draw the conclusion that there may have been a chemical reduction of the α- and β-tocotrienols to the corresponding tocopherols before entering the liver.

1. In search of other provitamins A, the metabolism of cryptoxanthin was studied in several species of freshwater fish, i.e. Chunna gachua, Labeo boga (retinol-rich) and Heteropneustes fossilis (dehydroretinol-rich). The fish were either allowed to starve for 20–25 d to make their intestines free from carotenoids and vitamin A or kept on a vitamin-A-deficient diet for 140–150 d to deplete the initial reserve of vitamin A in the livers.

2. Retinol-rich freshwater fish such as C. gachua and L. boga converted cryptoxanthin into retinol and no 3-dehydroretinol or 3-hydroxyretinol could be isolated from those fish that received cryptoxanthin.

3. 3-Hydroxyretinol and 3-dehydroretinol were isolated from the vitamin-A-deficient H. fossilis, a 3-dehydro-retinol-rich freshwater siluroid, after the administration of cryptoxanthin.

1. In sheep, provided with re-entrant cannulas in the caudal duodenum and with an infusion tube into the abomasal fundus, emptying of the liquid phase of the abomasal contents was studied with [57Co]EDTA. Radioactivity was measured continuously with Geiger-Müller counters placed along the re-entrant cannulas.

2. It appeared that first-order kinetics could be applied to the elimination of [57Co]EDTA from the abomasum. Mean retention time of this label in the abomasum was 40–50 min.

3. Infusion of a suspension of soya-bean protein in saline (9 g sodium chloride/l) caused an initially decreased rate of abomasal emptying, but after 48 h an adaptation had occurred to the original rate of emptying producing an increased volume of abomasal contents and increased flow-rate of digesta into the duodenum.

1. The effect of feeding casein, lactalbumin, soya-bean protein, gluten or gelatin on hepatic lipogenesis and the levels of hepatic fatty acid synthetase (FAS), glucose-6-phosphate dehydrogenase (EC 1. 1. 1.49; G6PD), malic enzyme (EC 1. 1. 1.40; ME) ATP-citrate lyase (EC 4. 1. 3. 8; CL), acetyl CoA carboxylase (EC 6.4.1.2; ACCx) and glucokinase (EC 2. 7. 1. 2; GK) was examined in young growing rats.

2. The total activities of ACCx, FAS, CL, GK, G6PD, GK, ME and fatty acid synthesis in vivo were positively correlated with protein quality.

3. The specific activities of ACCx, FAS, CL, G6PD and fatty acid synthesis in vivo were positively correlated with protein quality.

4. The specific activities of GK and ME were unrelated to protein quality.

5. The results demonstrate a dissociation between ME and hepatic lipogenesis and suggest a role for the NADPH generated by ME which is not related to the needs of fatty acid synthesis.

1. Sheep offered a roughage diet for 4 h daily were injected intravenously with glucose before and at various times after feeding. The insulin secretory response to glucose and the rate of disappearance of injected glucose were determined.

2. While the basal concentration of plasma insulin was unchanged, the base-line plasma glucose concentration tended to decrease during the meal.

3. The glucose load brought about an increase in the plasma insulin concentration at each injection, but the insulin response to glucose and the rate of glucose disposal were increased during the meal.

4. On varying the time of feeding between 08.00 and 16.00 hours, the increase in the insulin response to glucose and in the rate of glucose disposal always appeared to be related to the giving of food, independent of the time food was offered.

5. It is concluded that feeding increases the insulin response to an intravenous glucose load even when the increase in the basal level of plasma insulin on feeding is very modest in sheep given a roughage diet. The increased insulin response and glucose disposal rate following feeding did not appear to be related to diurnal rhythms in insulin secretory activity or glucose metabolism.

1. The degradation of a swede (Brussica nupus L., cv. Danestone) diet anterior to the terminal ileum was studied in two pigs fitted with T-shaped cannulas 150 mm before the ileo-caecal junction. Digestibility was calculated with reference to chromic oxide and polyethylene glycol.

2. In addition to the total loss of free glucose and fructose, there were substantial modifications to cell-wall material recovered in digesta. These included the apparent loss of 46–50% of uronic acid residues, 72–78% of phenolic material and 10–24% of cellulose initially present in the feed, and a partial solubilization of some hemicellulose components.

3. Since ‘fibre’ recovered at the terminal ileum differed in a number of important respects from ingested fibre, a number of methods for the analysis of dietary fibre were examined to establish (1) the extent to which analysis of feed represented material recovered at the terminal ileum and (2) whether such methods could be applied directly to digesta samples. Results were compared with a complete analysis of water-soluble (620 g/kg dry matter) and water-insoluble (380 g/kg dry matter) fractions of feed.

4. Chemical fractionation techniques gave more reliable quantitative estimates of fibre than in vitro enzymic digestion methods which overestimated fibre. Acid- and neutral-detergent methods both gave too low an estimate of fibre. As none of the methods could allow for the loss of components (particularly pectic polysaccharides) found by sampling at the terminal ileum, none gave an accurate qualitative or quantitative representation of fibre at this point in the gut.

5. It is suggested that, as vegetable fibre recovered at the terminal ileum has already undergone partial hydrolysis, a more dynamic model of dietary fibre, in which the action of gut micro-organisms is considered, may be required to establish possible physiological roles of fibre or fibre components in the digestive tract. Recovery of digesta from sites of interest may be the only way of reliably estimating fibre or specific fibre components at different levels of the gut. This approach to dietary fibre may be impractical when applied directly to humans but the digestive tract of the pig may be a suitable alternative model.

1. In separate experiments the isoleucine and leucine requirements of the kitten were determined on the basis of growth and nitrogen retention. The dietary concentrations of isoleucine tested were (g/kg diet) 1.4, 2.2, 3.0, 3.8, 4.6 and 9.0 with adequate (12.0 g/kg diet) leucine. The levels of leucine tested were (g/kg diet) 5.0, 7.5, 9.0, 10.5, 12.0 and 20.0 in diets containing adequate (9.0 g/kg diet) isoleucine. In both experiments six male and six female kittens received each dietary level of isoleucine or leucine for periods of 10 d in a balanced 6 x 6 Latin-square experimental design.

2. Asymptotic curves were fitted to the response relationships and the minimal dietary requirements for maximal response were estimated from the values at 0.95 of the asymptote. On this basis, the requirements for maximal growth were 6.2 g isoleucine/kg and 7.8 g leucine/kg diet. The requirements for maximal N retention were higher; 8.4 g isoleucine and 10.6 g leucine/kg diet. The isoleucine requirements suggested by this method are probably overestimations and might be slightly above 4.6 g/kg diet.

3. Plasma isoleucine and leucine concentrations were not useful in estimating the requirements. Plasma leucine increased rectilinearly with increasing dietary leucine while the response of plasma isoleucine to increasing dietary isoleucine was non-rectilinear. Neither response relationship exhibited a breakpoint at the level of requirement. Below the suggested minimal requirement for leucine there were significant increases in the concentrations of isoleucine and valine in the plasma. Dietary isoleucine below the level of requirement had no effect on plasma valine and leucine. Dietary leucine had no effect on the plasma concentrations of methionine, phenylalanine and threonine, suggesting that the effect of decreasing dietary leucine on plasma isoleucine and valine is a result of decreased oxidation rather than decreased protein anabolism.

4. In a separate experiment six kittens, presented a diet containing 2.2 g isoleucine/kg, developed crusty exudates around their eyes within 27 d and six kittens, presented diets containing 3.8 g isoleucine/kg, showed this clinical sign but with less severity within 47 d. Cultures of conjunctival swabs taken from the most severely affected kittens showed the presence of staphylococcal species, suggesting that in isoleucine-deficient kittens there was impaired resistance to these dermal microbes.

1. Whole-body and tissue fractional protein synthesis rates were determined in chronically-catheterized ovine fetuses at 120–130 d of gestation following an 8 h continuous infusion of L-[U-14C]-or L-[2, 3, 5, 6-3H]tyrosine.

2. From the net utilization of tyrosine by the fetus, corrected for apparent oxidation, and tyrosine concentration in the fetal carcass protein, whole-body protein synthesis was estimated to be 63 g/d per kg.

3. Following 8 h of infusion of labelled tyrosine the ewes were killed and fetal tissues were removed for the determination of tyrosine specific activity. The fractional rate of protein synthesis (k3) was calculated from the specific activity ratio, protein bound: intracellular free tyrosine. Tissue k, values for the liver, kidney, lungs, brain, skeletal muscle and small intestine were 78, 45, 65, 37, 26 and 93% /d respectively.

4. The absolute rate of synthesis was calculated by multiplying the tissue protein content by k2. Muscles, gastrointestinal tract, liver and lungs contributed approximately 20.5, 20.5, 14.4 and 9.4% respectively to whole- body protein synthesis.

5. The efficiency of protein synthesis as expressed by the RNA activity was higher in liver, lung and brain followed by kidney, skeletal and cardiac muscle.

1. The confounding effects of undernourishment and body cooling, resulting from maternal separation, were investigated by separating food and warmth deprivation. Rat pups aged 3–16 d were deprived of food for alternate 24-h periods by removal from the lactating mother. Some of the pups were placed with a foster mother, who kept them warm, whereas others were put in an empty cage at 22° which resulted in a sharp drop in body temperature.

2. Pups which were kept warm showed great fluctuations in weight between periods of starvation and feeding. The cooled pups lost less weight during deprivation but also recovered less on refeeding.

3. The resultant growth rate was much lower in non-fostered (i.e. cooled) than in fostered pups.

4. Up to the age of 8 d, cooled pups failed to raise their body temperature above that of the surroundings and did not digest the milk in their stomachs. Although, thereafter, they were able to raise their temperature to 26° and to digest stomach contents, the extra energy expended resulted in more severe growth restriction.

5. One-third of the pups died at 16 d but the rest were quickly rehabilitated by ad lib. feeding and showed a normal growth rate, although they remained smaller than the controls.

6. The development of nipples, hair, eye opening and vaginal opening was related more to chronological age than to weight.

7. A side effect of cooling was an almost complete abolition of active (REM) sleep, which is normally very high in infants; a slight rebound increase in active sleep was seen at 21 d. Direct as well as side effects of cooling may thus be responsible for some of the observed consequences of maternal separation.

1. Lambs were given a diet of oaten chaff-sucrose-fishmeal(48:48:4, w/w) and either 60 (diet A) or 120 (diet B) g urea/kg sucrose in the diet. All animals were defaunated and half were refaunated. Each group of lambs (faunated and defaunated) was then divided into two groups and given diet A or diet B. Feed intake, wool growth and live-weight change were monitored over a 182 d period.

2. The level of urea supplementation had no effect on wool growth or live-weight gain.

3. Defaunated lambs gained live weight at a higher rate (9%, P < 0.06) and grew 37% more wool (P < 0.01) than the lambs with large populations of protozoa in their rumens.

1. Sheep were infused intravenously with 88Mo- and 35S-labelled tri- and tetrathiomolybdates (1–2 mg Mo).

2. Most of the plasma radioactivity was trichloroacetic acid (TCA)-insoluble after infusion, but the stability of this fraction was reduced by pre-infusion or subsequent infusion with unlabelled thiomolybdates. Most of the 88Mo and 35S was shown to be associated with albumin.

3. It was concluded that compounds bound to albumin were relatively stable, but displaced or unbound thiomolybdates were rapidly hydrolysed to molybdate and sulphate.

4. There was no evidence of an irreversible interaction of either 35S or 88Mo with copper in plasma, despite the appearance of a TCA-insoluble Cu fraction. Increased dietary Cu did not increase the retention of 35S in plasma or affect the exchangeability of 35S-labelled thiomolybdates bound to albumin.

1. Immature male Wistar rats were given a zinc-depleted semi-synthetic diet (2 mg Zn/kg diet) for 4 weeks. Control groups received a similar diet containing 60 mg Zn/kg diet, either ad lib. or in amounts matched to the consumption of the Zn-deficient group. Rates of growth and food conversion efficiency were markedly lower in the Zn-deficient group compared to controls.

2. The phloridzin-sensitive uptake of galactose and 3-0-methyl glucose by everted jejunal rings from each group was measured over a range of concentrations. Kinetic analysis revealed that the maximum transport rate (Vmax)for the uptake of both sugars was significantly higher in the Zn-deficient group than in the control groups.

3. The villi, microdissected from samples of proximal jejunum, were significantly shorter and narrower across the base in the Zn-deficient group than those of the control groups, but were present in greater numbers per unit serosal area.

4. The present study shows that Zn deficiency leads to significant morphological changes in rat small intestine, which are accompanied by an increase in the capacity of the tissue to take up sugars across the mucosal membrane.

1. The intake by growing pigs of a diet containing British rapeseed meal (Brsm) extracted once with water was greater than that of a similar diet containing untreated Brsm, and a diet containing Brsm extracted twice with water was eaten more readily than one containing Brsm extracted once with water. Treatment of Brsm with slaked lime increased slightly its acceptability by growing pigs.

2. The addition of a water extract of Brsm to a soya-bean meal (Sbm) diet reduced voluntary intake compared with the voluntary intake of the same Sbm diet with water added. Addition to the diet of a water extract passed through an anion exchange column increased food intake but if a cation exchange column was used there was no effect on intake.

3. Treated rapeseed meals and extracts were analysed for glucosinolates, sinapine and tannins; the results indicated that glucosinolates rather than sinapine or tannin were associated with low feed intake.

1. Four experiments were carried out to identify and quantify the limiting amino acids (AA) in rumen microbial protein (RMP).

2. A method was developed which involved first, an assessment of the efficiency of utilization of absorbed AA-nitrogen (U) of RMP, defined as the retention of AA-N from RMP absorbed from the small intestine, and second, addition of a mixture of AA similar to the absorbed AA profile in a quantity defined by the U of RMP and equal to (1 – U)/U. Third, it involved removal of each AA in turn and measurement of the resultant N retention. Using this approach it was possible to calculate both the order and extent of AA limitations in RMP.

3. Apart from methionine which was found to be the most limiting AA, only lysine, arginine and histidine reduced N retention when omitted, and accordingly only these AA were limiting in RMP.

4. The method is discussed in detail and the amount of supplementary AA required to utilize RMP fully is calculated.

1. Sheep were fed once daily with 300 or 600 g dried perennial ryegrass (Lolium perenne) or white clover (Trifolium repens). Total rumen contents were sampled once daily at various intervals up to 24 h after feeding for 6 d.

2. Total weight of fresh rumen contents and dry matter (DM), organic matter and particulate matter concentrations were measured and the particle size distribution of rumen contents was analysed using a wet sieving technique.

3. There was a similar exponential loss of DM from the rumen with time after feeding for both perennial ryegrass and white clover. The rate of DM disappearance during the first 3 h after feeding was ten times greater for the higher intake and seven times greater for the lower intake than during the subsequent 21 h. The percentage of particulate material disappearingduring the first 3 h was greater for white clover (57% )than for perennial ryegrass (49%).

4. Particle size distribution analysis of rumen contents showed that the most rapid rate of particle size reduction occurred during the first 3 h after feeding. Despite a rapid rate of breakdown there was no increase in the total weight of small particles in the rumen.

5. The rate of reduction in particle size during this period was greater for white clover than perennial ryegrass.

6. Microscopic examination of rumen particles showed a difference in particle geometry between white clover and perennial ryegrass which appeared to be related to anatomical features of the plant.

1. A mathematical model is described, which simulates the metabolism of absorbed nutrients (amino acids, acetic acid, butyric acid, glucose, lipid and propionic acid) in growing sheep.

2. The basic assumption of the model is that each nutrient is partitioned between synthetic, oxidative or intermediate reactions with rates of reaction which are described using enzyme kinetics. These rates depend on the relationship between maximum reaction rates, constants of affinity and inhibition and the concentrations of metabolites as determined by the model.

3. Synthetic reactions calculate fat and protein deposition while intermediate reactions involve the production of ATP and NADPH. There is a total of twelve state variables and the model, programmed in CSMP and ACSL, is solved by integration of twelve differential equations.

4. The model calculates the efficiency of utilization of metabolizable energy for different nutrient inputs and the results may be interpreted in terns of fluxes through the metabolite pools. Simulations using inputs representing forage- and concentrate-based diets indicated decreased efficiency for the forage at high levels of intake and possible reasons for this were further studied in simulations where the inputs of protein and glucose were varied.

1. The primary growth of lucerne (Medicago sativa) was ensiled after treatment with either formic acid alone (4.1 litres/t; silage F) or with formic acid and either formaldehyde (30.5 g/kg crude protein (nitrogen x 6.25; CP); silage FF), glutaraldehyde (44.2 g/kg CP; silage FG) or a mixture of the two aldehydes at approximately half their individual application rates (silage FFG).

2. Compared with formic acid alone, both formaldehyde and glutaraldehyde reduced protein breakdown and carbohydrate fermentation during ensiling. The extent of protein protection afforded within the silo was similar for the two aldehydes, whereas formaldehyde was more effective in restricting carbohydrate fermentation. The effect of treatment FFG on silage fermentation was confounded by the silo bag bursting and the development of a clostridial-type fermentation. All aldehyde treatments reduced silage soluble-N content but N disappearance when the silages were incubated in polyester bags in the rumen was high for all silages and reductions due to the aldehydes were small.

3. Silage digestion was studied in four mature sheep each fitted with a rumen cannula and re-entrant cannulas in the proximal duodenum and distal ileum.

4. The apparent digestibility of organic matter (OM) in the whole tract was reduced (P < 0.05) to a similar extent by both aldehydes, whereas rumen OM digestion was reduced (P < 0.05) more by glutaraldehyde than by formaldehyde. The effects on digestion appeared to be due to the action of the aldehydes on the foods rather than to any adverse influences of the aldehydes on the metabolism of the rumen microbes because, although rumen ammonia levels were lower (P < 0.05) when the aldehyde-treated silages were given, rumen casein-degrading activity, the degradation of different feedstuffs when incubated in polyester bags in the rumen and microbial N flow at the duodenum did not differ (P < 0.05) between silages.

5. All aldehyde treatments decreased (P < 0.05) the apparent digestibility of N in the whole tract. Silage N degradability in the rumen was also decreased (P < 0.05) from 0.82 for silage F to 0.67, 0.60 and 0.62 for silages FF, FG and FFG respectively, and consequently non-ammonia-N (NAN) flow at the duodenum increased (P < 0.05). The aldehydes did not adversely affect the apparent digestibility of NAN in the small intestine, and net NAN absorption from the small intestine increased from 8.8 g/d with silage F to 11.4, 15.3 and 14.2 g/d with silages FF, FG and FFG respectively. Both the decrease in N degradability in the rumen and the increase in net NAN absorption from the small intestine were greater (P < 0.05) with glutaraldehyde than with formaldehyde.

1. The hydrogenation of a range of double-bond positional and configurational octadecenoic acid isomers (cis (δ2 and δ4 to δ13) and trans (δ2 and δ5 to δ13)) to stearic acid by a rumen Fusocillus sp. were examined.

2. The cis and trans δS to δ13 isomers were all hydrogenated to some extent by late-log-phase cultures added to suspensions of individual isomers and incubated for a further 3 h. Of the cis-isomers, δ5 to δll (79–73% conversion to stearic acid) were the preferred substrates. δ24s- (30%) and δ13-cis-isomers ( 5 % ) were poorly hydrogenated. Of the trans-isomers, δ8, δ9 and δ10 were 45% converted to stearic acid, the other isomers were poorly hydrogenated. These results are in agreement with less extensive studies using sheep rumen micro-organisms.

3. When cultures were grown from small inocula in media containing individual isomers more extensive hydrogenation was found than with late-log-phase cultures. At 24 h, cis δ2, δ4 and δ5 gave the highest conversions to stearic acid (90%) followed by the cis δ6 to δ12 and trans δ8 to δ10 isomers (approximately 75%), although at 6 and 12 h δ9-trans gave higher yields of stearic acid than δ9-cis, probably because the growth of the cis cultures showed a longer log-phase.