Two steers (Bos indicus and Bos indicus x Bos taurus) were acclimatized to an ambient temperature of 30 °C before working at this temperature on two treadmills (gradients 0 and 6°) for 2 h (one on each treadmill) whilst carrying a load equivalent to 10% of body weight. The study was then repeated at an ambient temperature of 15 °C. The effect of variation between animals, ambient temperature and rate of energy expenditure were tested on the linear regression model EEw = A PHR + B (where EEw is the energy expenditure (w/kg0·75) and PHR is the percentage increase of working heart rate over resting heart rate).

Animal and ambient temperature had no significant effect on the model. The gradient of the regression line was significantly greater (P < 0·01) when the animals were expending energy at the higher rate (about 30 W/kg live weight0·75) than when they were expending energy at the lower rate (about 14 W/kg live weight0·75).

To quantify changes in rates of metabolism and nutrient uptake of gravid uteiine, foetal and utero-placental tissues throughout gestation, mature Hereford cows received surgery at 132 ± 0·6 (n = 12), 176 ± 0·5 (n = 8), 220 ±0·4 (n = 11) and 245 ±1·5 (n = 7) days after mating. Indwelling catheters were implanted into a uterine artery and vein of all cows. Foetal catheters also were implanted into an umbilical vein and foetal femoral artery and vein (days 176 and 220) or into a placental artery and two placental veins (days 132 and 245). Approximately 5 days after surgery, deuterium oxide was infused into a foetal femoral venous or placental venous catheter during a 3 h period to quantify uterine and umbilical blood flows by steady-state diffusion methods. Oxygen, glucose, lactate and α-amino acid nitrogen concentrations were determined for uterine and foetal blood samples collected during this procedure.

Uterine blood flow increased 4·5-fold (2·92–13·181/min) and umbilical blood flow increased 21-fold (0·28–5·861–min) during the interval of gestation studied. The relative rate of increase of umbilical blood flow was about twice as great as that of uterine blood flow. Uterine arterial and umbilical venous concentrations as well as uterine arterial-venous and umbilical venous-arterial concentration differences in metabolites changed little with stage of gestation. However, because rates of blood flow increased, uptakes of O2, glucose and α-amino N by the gravid uterus and foetus increased as gestation advanced. The proportion of gravid uterine uptakes utilized by the foetus increased from day 137 to 226 for O2 (24–58%) and from day 137 to 180 for glucose (4–19%), then remained relatively constant. The proportion of gravid uterine α-amino N uptake utilized by the foetus remained relatively constant and averaged 60%. A net secretion of lactate from the utero-placenta to the uterine and foetal circulations was observed and increased as gestation advanced. These data indicate that increased rates of uptake or secretion of metabolites by tissues of the gravid uterus can be explained primarily by increased rates of uterine and umbilical blood flows.

Two experiments were carried out to test the effects of ryegrass maturity on rumen lipid metabolism. In the first experiment the effect of stage of maturity of perennial ryegrass on lipid metabolism in the rumen was studied with grazing sheep fitted with rumen cannulae. The pasture was either immature (13·8% crude protein), mature (8·1% crude protein) or senescent (5·5% crude protein).

The rates in vitro of triacyl glycerol lipolysis and linoleic acid (18: 2w6) hydrogenation were found to decrease with increasing age of the ryegrass.

In the second experiment the sheep were dosed with emulsified linseed oil (30 g) via rumen cannulae while grazing immature or senescent ryegrass and the rumen digesta and blood plasma sampled at 0, 4 and 8 h after dosing.

The proportions of linseed oil retained in the rumen were greater and blood plasma linoleic (18:2w6) and linolenic (18:3w3) acid concentrations higher when senescent ryegrass was fed.

It was concluded that the rates of rumen lipolysis and hydrogenation decreased with the age of pasture and that after dosing with linseed oil the polyunsaturated fatty acid concentrations in blood plasma increased.

The relative uptake of phosphate, introduced as radioactive 32P into an Agrostis-Festuca hill land association in mid-Wales, was examined under two contrasting methods of cultivation: (i) complete cultivation, (ii) slot-seeding. Seedling plants of Lolium perenne S. 23 and Trifolium repens S. 184 were grown as pure stands and as binary mixtures with plants either 4 or 6 cm apart.

Relative uptake of phosphate was higher under complete cultivation and, in the binary mixtures, clover accounted for 26% of the uptake only. The percentage of phosphate removed by each of the species when grown in mixtures remained constant over cultivation treatments. The significance of the results to agronomic practice is discussed.

Two experiments were carried out to study the effects of five agronomic variables on the marketable yield of transplanted leeks. In the first experiment two cultivars were used, cvs Splendid and Winterreuzen, and the treatments compared three plantraising systems, two ages of transplant when planted, and two plant population densities, two row spacings and two levels of nitrogen nutrition in the field. In this experiment some treatment interactions were confounded with each other.

In the later experiment only cv. Splendid was grown. There were two plant-raising systems, two plant-raising temperatures, two plant-raising nutrition levels, two times of transplanting (63 or 84 days from sowing) and four different sowings (7 and 28 February, 20 March and 10 April 1984). The duration of the growth period in the field was standardized by harvesting each treatment combination on two occasions, 168 and 189 days after transplanting.

The results from the first experiment showed that plants raised in modules at high temperature, planted early at a high plant density with higher than normal levels of nitrogen gave high marketable (> 12·5 mm in diameter) yields of 7·31 kg/m2, greater than that from any other treatment combination. The second experiment confirmed these general trends but also showed that the date of transplanting was of critical importance with the earliest plantings in the year giving the highest yields and with later plantings resulting in progressively lower yields irrespective of the way in which the transplants were raised. Comparisons with meteorological data showed that decreasing yields were associated with decreasing values of accumulated solar radiation and accumulated day-degrees during field growth.

These results are discussed in relation to other published data. They do not support some of the current recommendations for growing the crop but suggest that much more work needs to be done on production systems for this crop because of the potential for increasing marketable yields.

The effect of six intervals between harvests and three levels of N application on the concentration of nitrate-N and total N in total herbage, green leaf and ‘stem’ was studied in two varieties of perennial ryegrass during 30-week periods in each of the first two harvest years of a field experiment. The effect of two intervals between harvests on the concentration of nitrate-N in Italian ryegrass total herbage was studied in the same experiment. The effect of two intervals between harvests and three levels of N application on the concentrations of nitrate-N and total N in total herbage was studied in five grasses during a 32-week period in a second field experiment.

Increasing the interval between harvests tended to increase the concentration of nitrate-N in herbage; however, this seemed due mainly to the average date of harvest being later in the year with the longer intervals. The concentration of nitrate-N in herbage increased from June to September. Italian and hybrid ryegrass and tall fescue were much higher than perennial ryegrass in nitrate-N concentration at the highest level of applied N (525 kgN/ha per year). Apart from the species and time of year effects, the nitrate-N concentration seemed to be determined mainly by the amount of N applied divided by the number of days between the date of application and the date of sampling. The ‘stem’ of perennial ryegrasa tended to be slightly higher in nitrate-N concentration than green leaf. The proportion of nitrate-N in total N was increased by increasing the interval between harvests and by applying N and was nearly twice as high in ‘stem’ as in green leaf. Both the nitrate-N and the total N concentration of herbage, particularly the latter, seemed to be inversely related to solar radiation receipt.

Two trials were carried out to compare the milk yield, milk composition and the rate of growth of naturally or artificially reared kids and lambs of Damascus goats and Chios sheep.

Milk yield until weaning was similar in sheep and goats, but goats produced significantly more milk after weaning. Sheep milk was higher in total solids, fat, protein, lactose, ash and calorific value.

Lambs and kids grew similarly during the ad libitum milk feeding period but lambs grew faster during the restricted milk feeding period. Solid feed intake of lambs until weaning was higher than that of kids and the results indicated that the rumen develops later in kids than in lambs. During the post-weaning period lambs consumed more feed, grew faster and utilized feed more efficiently than kids. Lambs were more sensitive to high copper supply than kids.

The variability revealed in a half-diallel cross between nine diverse genotypes of winged bean (Psophocarpus tetragonolobus (L.) D.C.) in regard to yield and yield components was studied in the F1 generation. The results indicated that high genetic variability existed for all traits. With respect to seed size, general combining ability effects alone were adequate to predict the performance of hybrids. For numbers of pods per plant and seeds per pod, both general and specific combining ability effects were of equal importance, while the performance of hybrids for grain yield was mainly dependent on specific combining ability effects. Heterosis was clearly evident for number of seeds per pod and grain yield. Of the yield components, number of pods per plant exhibited a positive genotypic association of appreciable magnitude with grain yield, showing its usefulness as an indicator of yield in selection.

Triple test cross progenies arising from F2 of three crosses, namely, C164 x EB1556 BG25 x NP21 and BH15 x RD103, were used for investigating their interactions with macro- and micro-environments for number of days to heading, plant height, number of tillers per plant, ear length, number of grains per ear, 100-grain weight and yield per plant in barley. The analysis indicated, in general, that the additive component of genetic variance was more sensitive to macro-environment than non-additive components. In order to have a more precise estimate of this component, an experiment repeated over a larger number of locations and years would be desirable. The ‘j and l’type of epistasis showed sensitivity equal to the dominance components in response to the change of soil conditions. Covariances between family means and variances were used to detect the interactions of genetic components with the micro-environmental differences. The additive and the dominance components showed sensitivity to microenvironmental changes and were not differentially affected by the adverse soil condition compared with normal soil. The additive gene effects were relatively more sensitive, indicating the probable superiority of heterozygotes over the corresponding homozygotes with regard to stability.

Amongst the three populations, the population resulting from BH15 x RD103 was found to be most sensitive. Although the genotype x environment interaction for a character was population-specific, number of grains per ear and yield per plant were invariably the most sensitive.

Experiments on winter wheat were made from 1980 to 1982 to test fungicide and aphicide sprays in factorial combination with four amounts of nitrogen fertilizer, applied in either one or two dressings in spring. The wheat was grown on three farms with contrasting calcareous clay soils from three soil series; each year it followed a 2-year break on one farm, a cereal rotation on the second and continuous wheat on the third. Soils were sampled to a depth of 0·9 m at seedling emergence in autumn, and again in February and April, to determine the NO3-N and NH4-N in each 0·3 m horizon. Crops were sampled for growth analysis at monthly intervals from March onwards and analysed for nitrogen content. Measurements of stem sap NO3-N concentration were also made at 2-weekly intervals from February or March to late June.

Measurements of soil mineral N were used to calculate the fertilizer nitrogen dressings used in the experiments. The concentration of NO3-N in the stem sap was related to NO3-N in soil; concentiations remained high until most of the soil NO3-N had been removed by the crop. The time at which stem sap NO3-N concentration declined therefore acted as an index of soil N supply, and the data showed that fertilizer-N was needed when the NO3-N concentration fell below a 200 μg/ml threshold. Yields benefited from N applied in February or March only when stem sap NO3-N concentration fell below the threshold at this time.

Apparent fertilizer nitrogen efficiency exceeded 70 % where yields were very large, but ranged between 53 and 64% where yields were smaller because either soil physical problems or disease restraints were present.

A severe attack by take-all (Gaeumannomyces cerealis) caused premature senescence at one centre in 1980; this apparently prevented previously assimilated nitrogen from moving into the grain.

Four factorial experiments made in 1982 and 1983 tested the effect of 10 t CaCO3/ha, applied either in autumn 1981 or spring 1982, on the response of established grassland to 360 kg N/ha per year applied either as ammonium sulphate, calcium nitrate, urea or a mixture of ammonium nitrate and calcium carbonate.

Lime did not increase yield in the short term. It also reduced herbage Mn and, to a lesser extent, herbage N, P and Mg. The mixture of ammonium nitrate and calcium carbonate gave about 0·5 t D.M./ha per year more herbage than did the other forms of N.

Lime had no effect on the recovery in the herbage of N from calcium nitrate, but it reduced N recovery from the other three fertilizers in 1982, and from urea also in 1983. Soil pH, which initially ranged from 4·9 to 5·7 at the four sites, was raised by lime to almost 7·0 in the top 5 cm soil. This pH is probably not high enough to cause serious losses due to NH3-volatilization.

Application of fertilizer prone to loss from NH3-volatilization is not recommended soon after liming. However, the practice is not likely to cause detectable yield loss in established grassland in Northern Ireland.

Prilled urea, with or without a nitrification inhibitor (dicyandiamide, DCD) or urease inhibitor (hydroquinone), was compared with ‘Nitro-Chalk’ as a nitrogen fertilizer for winter oil-seed rape in field experiments on a clay loam soil at Rothamsted in 1984 and 1985. Each was tested when supplying 50 kg N/ha to the seed bed; each was also broadcast in early spring to supply 150 kg N/ha as either a single dressing or two equal dressings, the form of nitrogen being the same as that applied in the seed bed.

Seed-bed nitrogen increased plant growth during autumn and winter in both years but increased yield only in 1985.

Scorching of plant leaves was severe in spring after application of urea or urea plus DCD given as a single dressing, but was much less with urea plus hydroquinone or when the dressings were divided. DCD inhibited nitrification of fertilizer nitrogen but had little effect on yield compared with urea alone. Ammonia volatilization losses were reduced by urea plus hydroquinone but, irrespective of the type of fertilizer applied, loss was always less than 3% of the nitrogen applied. Soil pH rose rapidly after urea application and thereafter fell slowly, whereas pH fell immediately after application of ‘Nitro-Chalk’. Neither dicyandiamide nor hydroquinone affected the pH changes after urea application. Overall, grain yields from urea were 90%, whereas those from urea plus hydroquinone were 97%, of those obtained from ‘Nitro-Chalk’. Dividing the spring dressings of urea-nitrogen increased yield in 1985 compared with a single dressing, but not in 1984. Yields from divided and single dressings of ‘Nitro-Chalk’ were similar. Oil and protein yields generally showed the same patterns of response to the fertilizer treatments as were shown by grain yields.

Batcombe series soils readily break down to good tilths, Beccles series soils form cloddy seed beds that are resistant to weathering, and Stackyard series soils form unstable tilths that readily break down. The soils differ in their particle-size distribution. The proposition that such differences contributed to the differences in field behaviour was examined by forming artificial soils, each of which was made up from particles of one of the soils, but redistributed with respect to size in the proportion in which they occurred in one of the other soils.

As a measure of the relevant physical properties, breaking strengths and bulk densities of cylindrical ‘clods’ moulded from the artificial soils were determined. To aid interpretation of the observed soil properties, similar measurements were made on individual fractions, on various other mixtures and on the parent soils.

The breaking strengths of the soils made up to a given particle-size distribution from particles from the different parent soils were reasonably close to each other, with those for the Beccles distribution being more variable. There was a significant difference between the two. The strength of the reconstituted Batcombe soil was markedly greater than that of its parent soil, whereas that for Beccles soil was markedly less. There was little difference for the Stackyard soil.

The bulk densities of saturated soils reconstituted from all nine fractions could be estimated reasonably accurately from the properties of the separate components. The structure of each of these soils in the air-dry state was inferred from comparisons between measured and calculated bulk densities. The breaking strengths of air-dry reconstituted soils were estimated from the properties of the separate components, and agreed reasonably well with the measured values for soils in which the clay and fine silt fractions predominated.

Whereas it was generally possible to predict various physical properties of the reconstituted soils from those of the separate fractions, it was not possible to extrapolate the results to explain field behaviour.

Seven experiments on winter barley, made during 1979–81, measured the effects of several amounts of nitrogen, applied at different times in spring, on grain yield and nitrogen content. All of these experiments also tested a growth regulator applied in spring, and five of them tested fungicide sprays. In 1980 the experiment at Rothamsted also tested sowing dates, and an eighth experiment, also at Rothamsted in 1980, tested sowing dates and mildew fungicides applied in autumn or spring. In all the experiments treatments were tested in factorial combination.

N applied in February was less effective than N applied in March and both were less effective, in terms of grain yield, than N applied in April. Divided dressings were best applied in February and April or March and April; effects on % N in grain followed the same pattern and so, therefore, did the efficiency of uptake of fertilizer N. The growth regulator consistently reduced the length of the straw and diminished lodging; it increased yields in five of the seven experiments in which it was tested.

Responses to fungicides were inconsistent from year to year. Sowing in September rather than in October 1979 increased yield in both of the experiments at Rothamsted in 1980, especially of the 6-row variety Hoppel.

Multifactorial experiments on winter barley cv. Igri grown after potatoes were made from 1981 to 1983 on silty clay loam soils at Rothamsted. All tested combinations of seven factors, each at two levels: with and without autumn pesticide (aldicarb), two sowing dates (September or October), with and without a fungicidal seed treatment (‘Baytan’), with and without spring and summer fungicides, two amounts of nitrogen, two times of applying nitrogen and with and without a growth regulator (‘Terpal’). Growth, development, yield, nitrogen uptake, pests and diseases were monitored. Sowing in September, fungicide sprays in spring and summer, and the growth regulator had the largest mean benefits on grain yield (+0·80, +0·56 and +0·34 t/ha respectively). Some factors interacted with sowing date; thus aldicarb, the fungicide sprays in spring and summer and the later timing of N all increased yield more on the September-than on the October-sown barley. The larger yields on the September-sown plots were associated with more ears/m2 (978 v. 744) and, in spite of fewer grains per ear (17·8 v. 20·1), more grains per m2 (17·6 v. 14·7 × 103), but lighter grains (39·2 v. 42·3 mg). The largest yields each year (ca. 8.0–8.5 t/ha) were obtained from September-sown barley fully protected from pests and from pathogens in spring and summer and given N in April rather than in March.

The aphid vectors of barley yellow dwarf virus were sufficiently common and infective in two of the three autumns to infect the September-sown barley sufficiently that their control by aldicar b enhanced yield. Nematodes, slugs and dipterous stem borers were not numerous enough to be damaging in any year. Mildew in autumn was controlled by the seed treatment, but effects on yield were inconsistent. Mildew in spring and summer was more abundant on the October-than on the September-sown barley; it was controlled by fungicide sprays, which increased yield significantly each year. Leaf blotch was more abundant on the September-sown barley.

When given access to water once every 4 days, black Bedouin goats that were fed dry lucerne hay required, on average, only half the water and 60% of the gross energy they consumed when water was offered to them once daily. Digestibility of the feed in these goats was increased by 4%. The outflow of fluid from the rumen slowed down during the water deprivation period. A flow rate of 1080 ml/kg0.75. day was recorded during the 1st day of the period and only 350 ml/kg0.75. day during the last day. While being offered water once daily the outflow from the rumen amounted to 1243 ml/kg0.75.day.

Following the subjection of black Bedouin goats to infrequent drinking the mean retention time of the digesta in the rumen was extended by 33 % and in the entire gastrointestinal tract by 43 %. It is suggested that the slowing down of the ruminal flow that followed the subjection of the goats to infrequent drinking enabled the particulate matter to stay longer in the digestive tract despite their smaller size.

Two experiments were conducted, one with seven and the other with eight lactating cows, to measure the effect of supplementation with a cereal concentrate on the digestibility of fresh herbage and to provide equations relating digestibility of herbage to faecal indicators. Cattle were housed with free access to fresh herbage from individual Calan–Broadbent gates for recording feed intake, and faecal output was estimated by the use of chromic oxide. In both experiments a cereal supplement depressed herbage organic matter digestibility by 8 g/kg for each kg of fresh concentrate provided within the range 1–6 kg. The depression was associated with reduced digestibility of cellulose. Herbage digestibility was significantly related to faecal nitrogen and faecal cellulose. Herbage intake was depressed by concentrate supplementation and the response in milk yield to supplementation was small.

Two experiments were conducted with four lactating cows in a latin-square design. The rations were composed mainly of maize silage plus concentrates, supplemented with urea, Pruteen, or soya-bean meal supplying 25% of total dietary N. Nitrogen and energy balances were measured, and milk production recorded.

Dry-matter digestibility, intake of metabolizable energy (ME) and ME concentration in dietary dry matter were not significantly altered when Pruteen was substituted for soya-bean meal. However, mean nitrogen digestibility for all the treatments was significantly lower than expected from published relationships.

The substitution of Pruteen for soya-bean meal did not significantly affect the nitrogen balance of the animals or milk production, but the latter tended to be higher than that recorded with urea.

The responses to the different N supplements are discussed in relation to the feeding systems of the Agricultural Research Council and the French Protéines Digestibles dans l'lntestin Grêle, and are compared with predictions made from statistical relationships developed in our laboratory.

Stearoyl-CoA desaturase activity was determined in the subcutaneous and perirenal adipose tissue of pigs either fed ad libitum, or starved for up to 48 h. The effect of saturated fatty acids, as suet, or linoleic acid, as corn oil, on the enzyme activity was determined in pigs refed after starvation or fed 50% of the ad libitum intake.

Desaturase activity was similar in the outer and inner backfat and was twice as high as in perirenal adipose tissue. Starvation for 48 h decreased the activity by 70, 91 and 94 % in the outer and inner backfat and perirenal adipose tissue respectively. Lowering food intake to 50 % of normal decreased desaturase activity by 46% in the outer back-fat. There was no significant difference in the response of desaturase to 10% corn oil or suet added to the diet during refeeding after starvation or to the diet of underfed pigs. Although the enzyme thus appeared insensitive to dietary saturated fatty acids or linoleic acid, it was inhibited by linoleoyl-CoA in vitro.

Sheep were infused intraruminally with iso-osmotic solutions of saline, organic acids or lucerne silage extracts with or without additional acids and products of protein degradation found in silage. The post-ingestive effects of silage constituents on food intake were assessed by measuring the voluntary consumption of high dry matter silage over a 20 h period following feeding. In Expt 1, three different silage extracts each depressed food intake up to 4 h following feeding. In Expt 2, one of these extracts, to which 40 g of γ-amino butyric acid (GABA) was added, depressed intake up to 4 h following feeding; with the further addition cf 10 g α-amino butyric acid (AABA) and 28 g amines to this extract, intake was enhanced within 0·5 h but depressed from 4 to 8 h following feeding. In Expt 3, infusion of organic acids alone did not significantly depress food intake relative to saline, nor was there a discernible effect on food intake when graded levels of nitrogenous constituents from silage were added to the infusates. In Expt 4, infusion of an extract, to which only AABA and four other amines were added, depressed cumulative intake up to 8 h following feeding and had a more pronounced effect on food consumption than infusion of the extract with these constituents together with GABA. It was concluded that soluble constituents in silage can inhibit intake but no single constituent is primarily responsible.