A total of 25 steer carcasses from a wide range of breeds and carcass weight and fatness were used to examine the relationship between a range of fat thickness measurements and the dissected fat content of beef carcasses. Fat thickness measurements included those on the hot carcass suitable for ‘commercial’ use and others on the cold carcass commonly used in research.

The mean of the measurements of fat thickness from the two sides of the hot carcass between the 12th and 13th ribs (12H) gave the most accurate prediction of carcass fat content (FPCT). The relationship was described by the equation FPCT = 14·61 + 1·85 (12H) (R2 = 0·92; S.E. of prediction of individual FPCT at the mean= ±2·17%).

The mean of four fat thickness measurements made on the quartered surface between the 10th and 11th ribs of the cold carcass was the next most accurate predictor (S.E. = 2·28%) of fat content. Fat thickness measurements made on the hot carcass between the 10th and 11th ribs were the least satisfactory.

Although the hot carcass measurements between the 12th and 13th ribs were made under commercial conditions and included a wide range of types of cattle the prediction of fat content from these measurements had a marginally lower standard error than the prediction based on measurements made under experimental conditions.

Sheep were grazed for 2 years at stocking rates of 7, 14, 21 and 28/ha on a pasture comprising Lotononis bainesii and Digitaria decumbens cv. Pangola at Mt Cotton, south–east Queensland. There were six replicates of each treatment grazed in rotation with 3 days' grazing followed by 15 days' rest.

The initial dominance of lotononis was lost after 6 months of grazing and lotononis failed to persist satisfactorily at any stocking rate. Demographic studies showed that lotononis behaved as a short-lived plant, predominantly annual, with some vegetative perennation as stolon-rooted units under heavy grazing. Soil seed reserves varied from 5800 to 400 m2 at the lightest and heaviest stocking rates respectively. Lotononis failed to regenerate under Pangola shading or inopportune high grazing pressure. Soil bulk density (0–7 cm) increased from 1·2 to 1·4 g/cm3 according to stocking rate.

The body composition of 18 each of Mashona, Afrikaner and Hereford heifers was measured at the beginning and after 16 and 32 weeks of the experiment. The heifers not slaughtered at the beginning of the experiment were fed a complete diet containing 132 g crude protein and 12·0 MJ metabolizable energy/kg dry matter. Before slaughter, the animals were deprived of food and water for 24 h. Each animal was infused with 1 mCi of tritiated water (TOH) in order to measure total body water (TBW) and to estimate body fat.

The growth rate of the three breeds of heifers was similar despite differences in age and initial live weight. Both TBW and fat proportions, however, differed significantly (P < 0·01) between slaughter stages for each breed and between breeds at each slaughter stage. At the first, second and final slaughter stages the proportions of TBW were: 68·0, 59·4 and 54·5% for Mashona; 70·;5, 64·3 and 58·3% for Afrikaner and 65·3, 57·6 and 46·2% for Hereford heifers respectively. The corresponding proportions of body fat were: 10·2, 18·4 and 24·2% for Mashona; 6·6, 12·0 and 20·0% for Afrikaner and 13·7, 20·8 and 25·8% for Hereford heifers respectively.

There was a close relation between empty body weight and live weight at slaughter which was not influenced by breed. Both TBW and fat were estimated more accurately when TOH space and live weight were used jointly. However, the slopes of the prediction equations for each breed were significantly different (P < 0·05) in the case of both total body water and fat. It was necessary to use separate equations for each breed in order to predict either body water or fat. The significance of these findings for the estimation of body fat in live cattle is discussed.

A pasture of Lotononis bainesii and Digitaria decumbens cv. Pangola at Mt Cotton, south-east Queensland was mown on six occasions at intervals of ca. 3 months and after each mowing was subjected in 1 day to the treading intensity expected from sheep grazing at 0, 7, 14, 21 and 28/ha. A movable corridor and folds were employed to walk the sheep the required number of times on eight replicates of each treatment.

Lotononis regrowth was negatively related to sheep treading intensity, whereas Pangola was highly resistant to treading and grew vigorously from underground buds on rhizomes and from persisting stolons. Young lotononis seedlings were more vulnerable than older seedlings which had branched; plants developed from autonomous nodal roots were more resistant than seedlings. Attention is drawn to the contractile growth of the hypocotyl following epigeal germination which leads to a buried crown.

Lotononis plants were short-lived, and seedling regeneration of ca. 27 and 47 plants/m2 occurred in the late summer of the 2nd and 3rd year after sowing. Soil seed reserves averaged 16900/m2. Studies might be undertaken of management systems directed to favouring lotononis plant replacement through accretion to seed reserves, seedling regeneration through the creation of ‘gaps’, and seedling survival through judicious timing of grazing.

Experiments with spring barley in 1975–7 tested fungicides applied to control powdery mildew (tridemorph) or brown rust (benodanil) in factorial combination with six amounts of fertilizer N, applied either to the seed bed soon after sowing, as a later top dressing or half at each time.

Powdery mildew was the principal leaf disease in all three years. It tended to be increased by increments of N and by applying the N late but much less consistently in the first two years, when soils were very dry for much of the growing period, than in 1977 when amounts of rain were much closer to the long-term mean. Tridemorph significantly increased the number of ears in 1975, mean number of grains per ear in 1976 and 1000-grain weight in all three years; it gave net increases in grain yield of 0·55, 0·68 and 0·41 t/ha, respectively, in 1975–7. Yield response to increasing amounts of applied N was greatly increased where mildew had been controlled by the use of tridemorph, and was better where the N had been divided into two dressings than where it had been applied as a single dose. In 1975 and 1977 the biggest responses to tridemorph were obtained with late N but in 1976 yield was increased most by tridemorph where the N had been applied to the seed bed.

Analyses of samples taken in 1977 showed no significant effect of tridemorph sprays on concentrations of either N, P or K in the green crop. By contrast, analyses of grain samples in 1976 and 1977 showed that amounts of N in grain (mg N/grain) were affected by amounts of applied N and by tridemorph, and that there were interactions between these two factors. Concentrations of N in the grain (% D.M.) were also determined by the effects which these factors had on grain size. At small N rates tridemorph mostly increased grain size so that N concentrations were decreased by the fungicide. At large N rates increases in grain size where tridemorph had been applied were accompanied by increases in the N content of the grain (mg N/grain) so that N concentrations were either unaffected (1976) or were increased (1977) by the fungicide. With 90 kg/ha of applied N the fungicide increased the amount of N/ha removed in grain by over 21 % in each year. The apparent recoveries of N in these plots were increased from 66 to 81 % and from 87 to 105%, respectively, in the two years. Tridemorph had no significant effect on concentrations of P or K in the harvested grain but increased average amounts of these nutrients removed in the grain by 17 and 14%, respectively, in 1976 and by 14 and 7% respectively, in 1977.

Examination of black and white, infra-red aerial photographs of the experiments showed that, in each year, the brightness of individual plot images was significantly correlated with grain yield.

Complex designs without division into blocks are especially vulnerable to positional variation. Alternative methods of adjusting for such positional variation were compared in analyses of grain yields. The potential improvements in precision which might be achieved by the appropriate use of such analyses, and the difficulties of ensuring that unacceptable subjectivity and bias are not thereby introduced into the analyses, are discussed.

The activities of glutamine synthetase, phosphate-dependent glutaminase, phosphate-independent glutaminase, glutamate dehydrogenase, γ-glutamyl transferase and glutamine-oxo-acid aminotransferase were assayed in liver, kidney cortex, brain (cerebral hemispheres), spleen, skeletal muscle and ileum obtained from lambs of 100–260 days conceptual age. A curve was fitted to each set of data relating enzyme activity and conceptual age.

In the ileum, glutaminase and γ-glutamyl transferase activities declined during development. Glutamine synthetase activity in the spleen increased markedly after birth, whereas glutamate dehydrogenase activity declined as rumen function was established. In the liver, glutamate dehydrogenase and glutamine synthetase activities were highest in suckling lambs and there was a gradual increase in hepatic γ-glutamyl transferase activity throughout the period studied. The activity of phosphate-dependent glutaminase was lowest in the kidney cortex of ruminating lambs but renal activities of glutamate dehydrogenase, phosphate-independent glutaminase, glutamine synthetase and γ-glutamyl transferase were highest in ruminating lambs. In skeletal muscle, a gradual increase in glutamine synthetase activity occurred after 180 days conceptual age, whereas there was no detectable glutaminase activity in ruminating lambs. In the brain, there was an increase in glutamate dehydrogenase, phosphatedependent glutaminase and glutamine synthetase activities during the foetal and early suckling periods, whereas γ-glutamyl transferase activity increased throughout the period studied.

Glutamine-oxo-acid aminotransferase activity was not detected in any of the tissues studied. Phosphate-independent glutaminase activity was always less than 10% of phosphate-dependent glutaminase activity and therefore must have a minor role in the metabolism of glutamine in lambs.

A consideration of the relative activities of the enzymes at different stages of development indicated that the ileum, spleen, liver, kidney cortex and brain have a substantial potential for glutamine utilization during foetal life. As a lamb matures after birth, there are changes in the metabolism of glutamate and glutamine which indicate that there is a greater potential for net glutamine synthesis in older lambs. This could be associated with the need for detoxification of ammonia in ruminating lambs.

Studies were conducted to elucidate the nature and cause of the drastic losses of live weight of cattle grazing buffel grass pastures after first rains at the end of the dry season in northern Australia. This paper examines trends in weight and body composition during the dry and early wet seasons; it shows that although most of the loss in fasted live weight occurred just after first rain, most of the loss of body solids, mainly fat, had already occurred by this time. Losses of body solids in the dry season were not fully reflected in live-weight losses because of increases in total body water and in gut ‘fill’. The greatly accelerated weight loss in the period following first rain appears to have been due mainly to a large reduction in gut contents. Empty-body weight actually increased during this period owing to increases in tissue water. Continuation of this trend in tissue water into the early wet season resulted in the rate of live-weight gain greatly exceeding that of body solids.

The concentration of glutamate and of glutamine was measured in whole blood obtained from a maternal artery, a uterine vein, a foetal artery and an umbilical vein of chronically catherized ewes and foetuses from 100 to 140 days after conception. The activities of glutamate dehydrogenase, phosphate-dependent glutaminase, phosphateindependent glutaminase, glutamine synthetase, γ-glutamyl transferase and glutamine-oxo-acid aminotransferase were measured in placentomes obtained from ewes during a similar period of gestation.

The concentrations of glutamate in blood from maternal vessels remained constant, whereas there was a significant decline (P < 0·001) in the concentration of glutamate in foetal blood. Glutamine concentrations declined significantly (P < 0·05) in maternal blood and in foetal arterial blood (P < 0·001), whereas the concentration of glutamine in umbilical venous blood remained constant.

Mean arterio-venous differences for glutamate indicated that there was no net uptake from or release into maternal blood by the uterus. However, there was a significant (P < 0·02) uptake of glutamate by the placenta from the foetal circulation. Glutamine release from the placenta into the foetal circulation increased as the foetus matured.

Significant activities of glutamate dehydrogenase, γ-glutamyl transferase, glutamine synthetase and phosphate-dependent glutaminase were found in the placenta but there was no significant relationship between the activities of these enzymes and the gestational age of the foetus. The enzyme profile indicated that the placenta has a substantial potential for net glutamine synthesis.

It is concluded that, for a 140-day foetus, the release of glutamine from the placenta accounts for more than half of its nitrogen requirement. Direct placental transfer of glutamine from maternal blood accounts for only one-third of the glutamine released by the placenta into the foetal circulation of a 140-day foetus. Therefore, the remainder of the glutamine is synthesized in the placenta from glutamate. Only one-third of the glutamate required for this placental glutamine synthesis is from the glutamate released by the foetus. The remainder must be derived either from 2-oxoglutarate, as the result of aminotransferase or glutamate dehydrogenase activities, or from glutathione by the action of γ-glutamyl transferase.

In a field experiment, the influence of different forms and methods of application of urea nitrogen on the rice rhizosphere soil nitrogenase was evaluated under simulated intermediate deep water situations. Nitrogenase was high when the soil received small amounts of nitrogen and phosphorus with a water level of 20–25 cm. Moreover, during and after the flash floods the nitrogenase activity was considerably increased. There was a significant reduction in the nitrogenase activity when the nitrogen was applied to the shallow water through urea briquettes, but when it was applied either behind the plough or between the rows, the activity was stimulated. Increased water level of about 50 cm for prolonged periods considerably reduced the nitrogenase activity. Results indicate that the method of application of urea nitrogen and the water level influenced the rhizosphere soil nitrogenase activity under intermediate deep water situations.

Yield calibration of soil tests in western Nigeria savannah has been difficult owing to low response to P and response to only low P rates despite low available P in the soils. A study on the distribution of P forms in 60 surface soils of the savannah derived from igneous and metamorphic rocks and grouped into 11 classes was made. Average total P was 0·018% and organic P, which varied between 44 and 114 mg/kg, constituted 41% of total P. Active P components made up 40% of total inorganic P, the bulk of which was in the Fe-P fraction. All P forms except non-extractable P correlated significantly with organic matter.

The amounts of P needed to increase available P by 1 mg/kg in the soils, an index of P fixation, was correlated with pH and the free oxides of Fe and Al. The direct role of Fe-oxides and probable indirect effect of organic matter were indicated by regression analysis.

There was minimal maize yield response to P application and this was obtained only at low P rates from which an optimum rate of 20 kg P/ha was suggested. An attempt to use phosphorus sorption capacity (PSC) for P recommendation was not successful probably because of the low PSC values. A quick P recommendation based on available P status, fertilizer factor of 3·0 mg/1 and an optimum available P level derived from the relative yield v. soil P calibration curve was therefore suggested.

The C and N in the biomass of soils from eight grassland field experiments where lime had been applied was determined by the chloroform fumigation method. Lime application increased C and N in the biomass by approximately 30% overall, although there was no effect at two sites. In the unlimed plots basal CO2 production, biomass C, and flush of mineral N production (FN) increased with soil pH. Biomass C and FN were correlated with total N content but not with organic C.

Differences in the apparent C/N ratio of the biomass were found in unlimed soils of pH ≤ 4·5 and in those of pH > 4·5, the ratios being 4·2 and 5·8 respectively. For limed soils the ratio was 5·2. It is probable that the chloroform fumigation method is not suited to soils of very low pH, and that the C/N ratio obtained in soils of pH < 4·5 is artificially low.

Cattle grazing buffel grass pastures during the dry season at Katherine lose large amounts of live weight during a short period following first rain. In Part 1 we showed that these losses were due mainly to reduction in gut contents. Part 2 examines the changes in pasture, diet and grazing behaviour to assess the probable change in nutritional status of cattle following rain.

During the dry season the most valuable pasture component, green leaf, was very scarce and had a nitrogen concentration of about 1%. Diets of oesophageally-fistulated cattle contained less than 0·5% N. Shortly after first rain diet N doubled owing both to rapidly increasing amounts of green leaf and to the increase in N concentration in young leaf to over 3%. Although intake was not measured, literature is cited to show that this increase in dietary N would be expected to increase rumen digestion rates with a resultant marked increase in D.M. intake and a reduction in gut contents.

Although availability of high quality herbage increased very rapidly following first rain, a period of increased nutritional stress immediately following rain could not be ruled out. However, any such decline in nutrition appears to be short-lived.

Number of nodules and leghaemoglobin content of nodules increased with increasing Zn application up to 7·5 μg/g soil. Dry-matter yield and N fixation increased with Zn up to 10 μg/g soil. Both nodulation and N fixation decreased at higher levels. Soil N content showed an initial depletion but increased during the late season. Critical lower and upper levels for maximum N fixation were 1·75–2·5, and 10–14 μg of DTPA extractable Zn/g soil, respectively. In the present studies 5–10 μg Zn/g soil was sufficient for maximum N fixation in chickpea.

Growth and development of young mammals have been investigated in relation to environmental temperature and energy intake. The experimental design and statistical analysis have allowed an evaluation of the separate and combined effects of two environmental variables and the time it takes for these effects to develop. Piglets aged 14 days lived at either 35 or 10 °C, on a high or low energy intake (the energy content of the former was twice that of the latter). The influence of each of the four treatment combinations was assessed up to 64 days of age.

At 64 days of age the piglets at 35 °C on the high intake (35H) were twice as heavy as those at 10 °C on the low intake (10L). The other two groups (35L and 10H) had similar body weights, and these were between the 35H and 10L. Ambient temperature had a rapid influence on appearance and morphology: animals in the cold were shorter and squatter than those in the warm. In general, energy intake influenced the absolute size of the internal organs whereas temperature affected their size relative to body weight. Skeletal growth was faster in the warm than the cold, and on the high than the low intake. No statistically significant interactions were generally found between temperature and intake, indicating that their effects were exerted independently. Most of the effects were established after only 17 days.

The present investigation has helped in interpreting earlier studies on growth which concentrated on the effects of only one of the two environmental variables of temperature and nutrition. It emphasizes the key roles of nutrition in adaptation to environmental temperature, and of ambient temperature to nutritional studies.

An emulsion of [3H]triglycerides was used to investigate how circulating triglycerides are partitioned between milk fat, body fat and use as an energy source in lactating sheep. Immediately after intravenous injection of the emulsion the radioactivity in the blood was predominantly associated with the triglycerides of the fraction that contained chylomicrons and very low density lipoproteins. The radioactive triglyceride was used both as a precursor of milk fat and as a source of energy. The proportions utilized for these two purposes were determined experimentally and the amount retained in the carcass lipids was found by difference. In separate control experiments with nonlactating sheep the total radioactivity in the body lipids was determined by carcass analysis. This total together with that accounted for by oxidation amounted to 98% of the total radioactivity injected. These results established that the emulsion was a reliable model for the purpose intended.

The proportion of the labelled triglyceride that appeared in milk fat declined from 45% at 17 days after lambing to 8–10% at 73 days after lambing. The proportion that was oxidized was also lower in late lactation so that retention in carcass lipids was substantially increased at that time.

The extent and possible mechanism by which spring-sown oil-seed rape plants can compensate for insect or artificial injury to flower buds and pods were investigated by examination of the yield, and its components, of plants collected from commercial fields and those grown in field cages and glasshouses. Plants were able to compensate and in some instances overcompensate for all observed levels of M. aeneus injury or artificial bud removal by the production of more axillary racemes, which may be due to the loss of apical dominance. Artificial injury to the pods or infestation by C. assimilis larvae did not result in a significant reduction in the yield of seed and was compensated for partly by a slight increase in the number of axillary racemes and by slight increases in the number of pods on each axillary raceme and in the 1000-seed weight, and resulted mainly from the diversion of nutrients to other yield-bearing organs. Injury by D. brassicae larvae was partly compensated for in 1975 and at lower injury levels in 1974 and involved a similar mechanism to compensation for C. assimilis injury. These results are discussed in relation to the observed infestation levels in field surveys and current control practices.

The grain weights of normal and high-lysine cultivars were compared in field and pot experiments in which the supply of assimilate per grain was adjusted by a variety of treatments involving application of fertilizer, thinning, degraining or defoliation. The results of these experiments indicated that in normal cultivars, grain weight was affected both by the supply of assimilate from the green tissues and by internal factors in the grain which limited the accumulation of this assimilate. Some evidence suggested that physical constriction of the expanding endosperm by the surrounding husk could be one of these factors; the effects of the husk on growth of the caryopsis was not clear.

The development of grain weight in the high lysine cv. Riso 1508 was initially similar to that of normal cultivars, but the cessation of growth as maturity approached was more abrupt. Increased assimilate availability resulting from the application of fertilizer, thinning or degraining treatments effectively increased grain weight in this cultivar, but to a lesser extent than in low-lysine cultivars. Conversely, decreased assimilate supply as a result of defoliation produced less marked reductions in grain weight in the high-lysine type, suggesting that the reduced starch accumulation associated with the high lysine characteristic rendered superfluous some of the photosynthetic capacity in these types.

Hypocuprosis has been diagnosed for 4 years in calves of a beef suckler herd at Warren Farm, Berkshire. The copper (Cu) contents and distribution in the soil at that site, as well as changes in herbage Cu throughout the 1979 grazing season, were examined. The herbage Cu concentration was always less than 7·5 μg/g and decreased markedly to 3·0 μg/g during July. Serum Cu contents of both untreated cows and untreated calves also decreased markedly, but at a much earlier stage than the decrease in herbage concentration. One untreated calf developed severe anaemia, but recovered when treated with Cu Ca EDTA. Although changes in the coefficient of absorption of dietary Cu were caused by changes in S and Mo contents, the calculated availability of Cu was dominated by the Cu content per se. Thus the calculated availability remained relatively high during the period when serum concentration decreased.

The decrease in serum Cu may have occurred as the result of a differing availability of Cu in ensiled and grazed herbages. However, coincident with the decrease in serum Cu was a high concentration of Fe in the grazed herbage which was largely associated with the surfaces of the leaves. It is therefore possible that the development of Cu deficiency immediately after the animals started to graze was precipitated either through an interaction between Cu and Fe in the animal, or because of a reduced availability of Cu through an interaction with ingested soil.

Field experiments on the effect of moisture regimes and fertilizer application on fibre yield of two jute varieties showed that JRO 632 (Corchorus olitorius L.) produced significantly more fibre, utilized moisture more efficiently and extracted water from deeper layers than did JRC 212 (Corchorus capsularis L.). Scheduling of irrigation at 20% available soil moisture (ASM) gave the highest fibre yield in normal (1970) and drought (1972) years but unirrigated conditions (dry regime) gave highest yield in a year of excess rainfall (1971). The consumptive use (CU) increased from dry to wet regimes and the water use efficiency (WTJE) was greater in dry regimes in normal as well as in excess rainfall years. But the WUE was maximal when the crop was irrigated at 60% ASM in the drought year. The water requirement of the jute crop was 490 mm in the normal and excess rainfall years (20% ASM and dry regime respectively) while in the drought year it was 560 mm (20% ASM). The moisture extraction was more from deeper depths in the dry regime and only from shallower depths in wet regimes.

The fibre yield increased with increase in nitrogen application from 40 to 80 kg/ha. Application of 40 kg P2O5 and 40 kg K2O/ha did not improve the fibre yield in the excess rainfall and drought years. In the drought year (1972) irrigating at 20% ASM and 80 kg N/ha and in the excess rainfall year (1971) the dry regime with 40 kg N/ha produced highest fibre yields. There was not much variation in CU and WE of the crop due to different fertilizer levels. The WUE was increased by irrigating at 20% ASM with 80 kg N/ha in a crop rotation system where P and K were applied to preceding crop.

A total of 21 rumen-cannulated wether sheep and six rumen-cannulated Ayrshire cows were used in a series of experiments to investigate fermentation in the rumen in animals given silage diets and the nominal metabolism of silage lactic acid. Dietary experiments with sheep (three experiments) and cows (two experiments) given diets consisting of formic acid–preserved perennial ryegrass (Lolium perenne) silages, in some cases with supplements of rolled barley, were conducted to investigate the ruminal concentrations of lactic acid and of volatile fatty acids (VFA) after feeding. Ingestion of silage was followed by a short-lived peak in lactic acid concentration in the rumen and by a subsequent increase in the concentration of propionate or propionate and butyrate. Butyrate production was more evident in cattle than in sheep. Taken as an average over a 6 h period of sampling the proportions (m-mol/mol total VFA) of acetate, propionate and butyrate in the rumen in animals given silage alone were typically 590–600, 210–250 and 70–150 respectively. When silage was supplemented with barley, in both sheep and cattle, the proportion of propionate was reduced and the proportion of butyrate was increased. In one experiment with sheep these changes in fermentation pattern were shown to be accompanied by an increase in the number of rumen protozoa from 2·78×105/ml to 18·66·105/ml (P <0·01). However, in a subsequent experiment it was shown that defaunation led to an increase in the proportion of butyrate in the rumen.

Twelve estimates were also made with sheep of the metabolism of lactic acid infused into the rumen in a single dose of 20–50 g. These experiments showed that both (L+) and DL-lactio acid were metabolized equally rapidly with a half-life of approximately 25 min. In faunated animals the major products of fermentation were propionate with a small amount of butyrate. In defaunated animals lactate metabolism was slowed and the major product of fermentation was butyrate.

In vitro studies of lactate fermentation were carried out using strained liquor and isolated bacterial and protozoal fractions from the rumen of sheep receiving silage diets. The rates of lactate disappearance (μg/mg protein/h) were 50 and 22·2 for the rumen liquor and bacterial fraction, respectively, which were significantly (P <0·05, n = 5) less than the rate of 294·7 for the protozoal fraction. Rumen liquor, bacterial and protozoal fractions yielded a similar mixture of fermentation end-products, propionate accounting for approximately 60% of the VFA produced.

The results are discussed in relation to the metabolism of silage lactic acid in the rumen, the production of VFA and the yield of ATP for microbial cell synthesis. It is concluded that the pathways of lactate fermentation are regulated by the rumen microbial population and that protozoa may have an important role in the regulation of lactate fermentation.