Friesian bull calves, 2 weeks old, were given an experimental diet of cow's milk supplemented with phosphorus to provide three rates of P intake: adequate, high, and very high. After 1 week's preliminary feeding, studies of absorption, endogenous secretion, urinary excretion, serum concentration, retention and kinetics of Ca and P metabolism were made by a balance and dualradioisotope technique with 32P and 45Ca.

The efficiency of P absorption decreased significantly as the P intake increased and the highest absorption efficiency was 96% on the unsupplemented milk diet. Endogenous faecal excretion of P was low on all treatments. Urinary P excretion was substantial even on the milk-only diet and increased further with supplementation of P. The efficiency of absorption of Ca remained constant, and urinary Ca excretion was low in all the groups. Serum P and Ca concentrations did not vary significantly but there was a significant decrease in the retention of P and Ca as the P intake increased.

Although urinary excretion appears to be the main process responsible for P homoeostasis in preruminant milk-fed calves, some regulation of the efficiency of absorption of P according to the P intake may also occur.

Twelve sheep were fed semisynthetic roughage diets at three rates to study the effects of intake of dry matter, concentration of phosphorus and the physical form of two low-P barley straws upon the faecal losses of P. The sheep were in negative P balance throughout the experiement. The absorption of dietary P increased with P intake and was unaffected by differences in the physical form of the roughage. For each barley straw diet, endogenous faecal P increased with dry matter intake, and was higher when the roughage was ground than chopped. Over the whole experiment, daily endogenous faecal P ranged from 8·5 to 31·5 mg/kg live weight. Endogenous faecal P was related to P intake or to dry matter intake and plasma inorganic P. The concentration of faecal endogenous P was negatively related to the intake of each diet. It is concluded that the concentration of inorganic plasma P and the rate of salivary secretion are responsible for the endogenous faecal excretion of P and the regulation of P balance in sheep fed low-P diets.

In a 2 × 4 factorial experiment, the laying performance of hens given diets with or without blood meal and four concentrations (0, 5·71, 11·43 and 17·14 g/kg) of added magnesium chloride was measured for 280 days. The inclusion of 50 g/kg blood meal in the laying diet reduced the rate of laying (P < 0·05), egg weight (P < 0·01), egg output (P < 0·01), food intake (P < 0·01), body weight gain (P < 0·01) and body weight at 457 days (P < 0·05). It increased the height of albumen (P < 0·05), Haugh unit score (P < 0·01) and shell colour intensity (P < 0·05) of fresh eggs. The inclusion of increasing dietary concentrations of magnesium chloride reduced (P < 0·01) the specific gravity of eggs but had no significant effect on any of the other egg quality or production characteristics. The dietary treatments had no significant effect on Haugh units of stored eggs.

Three pot experiments were performed in unheated glasshouses at the University College of North Wales College Farm, Aber, Gwynedd in 1980–1983. Two experiments tested the effects of sowing date and N supply, the third sowing density and nitrogen supply. Extension growth of main-stem leaves was measured by ruler and expressed in thermal time units to allow comparisons between sowing dates. Rate and duration of leaf extension were determined from linear regressions of leaf length against thermal time.

Increasing N supply increased leaf extension rate but had no significant effects on leaf extension duration. Leaf extension rate increased with leaf position on the main shoot, but decreased slightly in leaves extending at the time of stem elongation. Leaf extension duration also increased with leaf position on the main shoot and was related to mean temperature during the leaf extension phase. Plants sown in September were able to compensate for lower radiation receipts by having a faster rate and longer duration of leaf extension, by producing larger leaves with a greater specific lamina area and by partitioning a greater proportion of extension growth into lamina and less into sheaths. In plants sown in June, the largest leaf occurred at a lower stem node and leaves emerging later showed a strong response to N. It is suggested that this is attributable to earlier onset of internal competition for assimilates. Variation in leaf extension rate was the main factor influencing variation in final leaf area. There was a strong positive relationship between leaf extension rate and leaf N content.

Increasing sowing density increased the area of the first four leaves on the main shoot and decreased that of later leaves, changes mainly associated with changes in leaf extension duration. It is concluded that progress in the modelling of leaf area expansion, light interception and dry matter production requires more information about how sowing date, sowing density and N supply interact to influence crop development and leaf growth.

Effects of inflorescence removal under different plant densities and degrees of shading on seed yield of field beans (Vicia faba L.) were investigated. Two indeterminate cultivars were used in field experiments for two seasons (1985 and 1986). The hierarchy within the generative storage system of field bean plants was manipulated by removal of inflorescences at various growth stages and nodes.

Removal of the inflorescences of nodes 1–3 (counted from the base upwards) caused about 30% loss of seed yield potential compared with the control but compensatory increases in seed yield were found, differing with plant density and duration of shading. Under favourable growing conditions (no shading, 20 plants/m2), overcompensation occurred, giving a mean seed yield up to 40% more than in controls.

Removal of all inflorescences above the ninth flowering node did not significantly reduce seed yield as plants completely compensated for the restriction on yield imposed.

Using closely related inbred lines, the effects of selecting for two contrasting seed types (desi and kabuli) and colours (brown and white) were determined for a number of agronomic and seed characters in chickpea. Plant establishment was 53% higher in desi types than in kabuli types, and 20% higher in brown-seeded lines than in white-seeded lines. Increased contents of tannins in testas of brown seeds were associated with the seed colour response, whereas the difference in establishment between desi and kabuli types was probably a function of the thicker desi testa. Differences in yield due to seed type and colour reflected differences in establishment, but were smaller in magnitude.

Seed type was clearly associated with testa fraction and fibre content. Desi seeds averaged 15·7% testa and 13·2% acid detergent fibre, but kabuli seeds contained only 6·7% testa and 5·6% fibre. In contrast, the crude protein content of kabuli seeds was 1·4 percentage points higher than that of desi seeds. Testa and fibre contents of brown kabuli seeds were significantly greater than those of white kabuli seeds, although the differences were smaller than those between desi and kabuli types.

Decortication was satisfactory for white desi seeds, but for white kabuli seeds it gave rise to highly fragmented cotyledons which were often contaminated with attached testa. Brown kabuli seeds produced a sample of intermediate quality. It is suggested that, with some genetic improvements and processing refinements, brown kabuli genotypes could be developed as dual-purpose chickpeas, having both culinary and stockfeed uses.

A field study in India in 1987 evaluated the effects of flooding at either tillering (25 days after sowing) or flowering (50 days after sowing) or at both on growth, yield and mineral composition of Pennisetum americanum L. Leeke in a moderately sodic soil (pH 8·5, exchangeable Na 18%).

Flooding for 1, 2, 4 or 6 days at tillering or flowering significantly reduced tillering, plant height, dry matter content, ear length and 1000-grain weight and resulted in a 6·3, 150, 21·6 or 26·6% reduction in grain yield, respectively. Flooding decreased oxygen diffusion rate, restricted root growth and decreased ion uptake, especially of N, P, K and Zn, and led to higher absorption of Na, Fe and Mn. The detrimental effects were greater when the crop was flooded at both stages.

Responses of cultivars of Lolium perenne with contrasting winter hardiness to hardening and dehardening at different temperatures were studied in controlled-environment experiments in 1984/85. After hardening at 2 °C, the hardy cultivars Premo and S23 had faster initial rates of change of LT50 (lethal temperature at which 50% of plants were killed), measured on seedlings in an artificial freezing test, and achieved a greater degree of cold tolerance than the susceptible cultivar Grasslands Ruanui. When acclimated at higher temperatures (4–10 °C), the hardier cultivars were better able to develop increased cold tolerance than Grasslands Ruanui. Plants of Premo and S23, previously hardened at 2 °C, maintained their cold tolerance when transferred to warmer temperatures (4–12 °C) better than Grasslands Ruanui, which dehardened even at 4 °C.

The responses of the cultivars to hardening and dehardening temperatures under controlled-environment conditions were reflected in seasonal changes in hardiness, measured as cold tolerance of tillers sampled during fluctuating temperatures of a typical maritime winter (1977/78) at Aberystwyth, UK.

Various measures of skeletal size were made on five or six occasions on 30 Dorset Horn and 30 Corriedale sheep (10 entire males, 10 females and 10 castrated males) commencing at 1 month of age (live weight 10 kg) and then at increments of 10 kg until 55 kg. After weaning at 6–7 weeks, they were fed ad libitumon a high-quality diet. The data sets for each sheep were analysed separately and, where appropriate, pooled equations for sex and breed were generated. Within both breeds, males had the widest shoulders at any given age and, within the Corriedales, males had the deepest chests. Dorset Horns grew faster than Corriedales and, except for leg length, were larger and heavier at corresponding ages.

At any given live weight, there was no difference between sexes within breeds and the breeds had similar chest depths. The Corriedales had longer legs and smaller shoulders than the Dorset Horns at all weights and, when heavier than 30 kg, were also larger in other body dimensions.

In field studies of two varieties in Cambridge, UK, in 1985 and 1986, the percentage of total incident radiation intercepted by potato canopies with complete ground cover was as low as 80% for some plots but approached 100% in dense canopies. Although percentage ground cover is useful for assessing canopy growth, it is not wholly suitable for estimating light interception and may lead to serious errors in calculation of efficiency of conversion into dry matter.

Effect of timing of pregnant mares's serum gonadotrophin (PMSG) injection combined with a progestagen-impregnated vaginal sponge on fixed-time artificial insemination with fresh, undiluted semen during the nonbreeding season was investigated. PMSG injection 2 days before sponge removal (group A) caused significantly earlier oestrus than injection at the time of sponge removal (group B). Lambing percentages in a total of 320 ewes after fixed-time insemination at 36 h (64·1%) and 48 h (47·2%) in group A, and 48 h (59·5%) and 60 h (39·5%) in group B were not significantly different from those resulting from ‘at oestrus’ insemination (500% and 511% in groups A and B, respectively). The present results indicate that the optimum time for fixed insemination may depend upon the time of PMSG injection associated with progestagen treatment.

Experiments in 1986–88 compared the spring field bean cultivars Alfred, Minden, Ticol and Troy, grown on clay-with-flints soil at Rothamsted, at row spacings of 12 and 48 cm, and compared two pest and pathogen control programmes based on (i) ‘standard’ control of Ascochyta fabae, Ditylenchus dipsaci and seed-borne viruses and (ii) ‘enhanced’ control of Sitona lineatus, bean leaf roll virus via the vector Acyrthosiphon pisum, Botrytis fabae and Uromyces viciae-fabae in addition to the pests and pathogens in the ‘standard’ control.

With standard control, Minden had the largest mean seed yield of 4·6 t/ha; with enhanced control, Alfred was best with 6·1 t/ha.

The yield benefits of enhanced control ranged from 0·2 t/ha on Ticol in 1986 to 2·4 t/ha on Alfred in 1988. They were related to the control of weevils (S. lineatus), chocolate spot (B. fabae) and rust (U. viciae-fabae). At 1989 prices, the cost of materials used for enhanced control would be repaid by a yield increase of 0·3 t/ha.

The closer row spacing increased yields by 0·15 t/ha on average but effects differed greatly between years. Benefits were largest in 1986 when plants were shortest and in that year were largest for the shorter cultivars.

It is suggested that trials of field bean cultivars should always include a test of pest and pathogen control.

Signal grass (Brachiaria decumbens Stapf.) given 100, 200, 300 and 400 kg N/ha and protected from defoliation by growing in cages was evaluated for tiller height, tiller density and dry matter (DM) yield in 1979 and 1980.

Nitrogen rate had highly significant linear effects on tiller height and density and DM yield of the grass at each age of pasture regrowth and at all the ages of pasture regrowth combined in 1979 and 1980. The quadratic effect of N rate was not significant in either year.

The positive linear responses shown by the growth of tillers and the overall yield of the grass at N rates up to 400 kg/ha suggest that further work, using N rates above 400 kg/ha, is needed to ascertain the optimum N requirement of this grass.

The effects of chlormequat chloride on grain yield and its components in spring barley (Hordeum vulgare)cultivars were studied in five field experiments conducted at two sites near Belfast over 3 years (1982–84). Grain yield was significantly increased by chlormequat chloride treatment in only one experiment, where ear loss was less in the treated plots. Number of ears per plant was increased by treatment in another experiment but yield was unaffected. It was concluded that chlormequat chloride applications are unlikely to produce consistent yield increases in field crops of spring barley.

The rumen anaerobic fungus Neocallimastix sp. LM1 was specifically labelled in batch culture with either [14C]lysine, [14C]lysine + [3H] tyrosine, [14C] methionine, or [35S] sulphide. Fractionation of acid hydrolysates of fungal biomass on an amino acid analyser showed that the labelled amino acids were directly incorporated into fungal protein with little or no degradation. [35S] Sulphide was incorporated into cysteine and methionine.

Absorption of amino acids from the small intestine was measured in sheep with permanent fistulae in the abomasum and terminal ileum, by introducing radiolabelled fungal biomass into the abomasum together with Cr-EDTA as the marker for digesta flow. The proportions of [14C] lysine (Expt 1), [14C] lysine + [3H] tyrosine (Expt 2), [14C] methionine (Expt 3) and the sulphur amino acids from [35S] sulphide (Expt 4) which appeared unabsorbed at the terminal ileum averaged 0·13, 0·07 + 0·08, 0·13 and 0·02, respectively. These proportions reflect the high digestibility of certain essential amino acids and the sulphur amino acids of fungal proteins. The results indicate that the true fractional digestibility of fungal proteins is c. 0·9. Consequently, a large biomass of anaerobic fungi in rumen digesta would be expected to provide a valuable source of digestible amino acids to ruminants.

Pig and cow slurries were applied to bare soil surfaces in the laboratory. Volatilization of NH3 was measured using ventilated enclosures for 3·25 days after slurry application. Slurries were acidified to pH values between 7 and 4 with 5 M H2SO4. Lowering cow slurry pH to 5·5 decreased NH2 volatilization by 95%, while lowering pig slurry pH to 6·0 decreased NH3 volatilization by 82%. A field experiment, measuring the volatilization of NH3 for 2 h after application to grassland stubble of slurry acidified to pH values between 7·5 and 5, gave similar results to the laboratory study.

Titration curves were constructed within the pH range of 9 to 4 with cow and pig slurries. There was a significant (P < 0·05) positive correlation between the NH4+-N content of the slurries and the volume of acid required to attain a target pH of 6·0 for pig slurries and a pH of 5·5 for cow slurries. One litre of slurry containing 2 g of NH4+-N required c. 20 ml of 5 M H2SO4 for acidification.

Two field experiments, at Woolly Hills Farm, County Durham, UK, and a glasshouse experiment were carried out in 1977. Early in the growing season (May-July), a covering of bracken litter increased the number of ryegrass and clover seedlings which became established both in an area where bracken had been removed and where there were developing fronds. In a second experiment (August-October), bracken litter had no effect on seedling establishment in the open. Under the frond canopy, the absence of litter was beneficial to clover establishment. The frond canopy reduced the number of ryegrass seedlings by half compared with the numbers in the open. In the glasshouse, litter caused a small reduction in the numbers of ryegrass and clover seedlings becoming established.

The results suggest that litter may be either beneficial because of the prevention of desiccation in dry periods or detrimental, perhaps through allelopathic effects or shading. In terms of the successful establishment of a sown grass and clover sward, it would seem that litter removal by incorporation or burning is more justified in upland hill pastures because of the need to improve soil fertility than because of adverse effects of the litter itself.

The extent and rate of N release from nylon bags containing green panic (Panicum maximumvar.trichoglume)litter was measured for up to 319 days (long-term studies) in 1978/79 and 1979/80 in Gayndah, Australia. Dry matter (DM) decomposition rates were measured in 41 periods of 39 days and related to environmental variables and initial litter N concentrations (short-term study).

About half of litter DM decomposed during the long-term studies, while N concentration in the remaining litter increased from an initial average of 0–57 % N, to 0–95 % N. Net release of N from bags began when its concentration in the residue increased to c.0–65% N (or when the C:N ratio decreased to 75:1). Only a net 20–30 % of the initial N was released for potential plant uptake by the end of the study. The short-term study showed that DM decomposition was rapid and independent of pasture age. Decomposition rate increased with soil moisture and average daily temperature but was unaffected by initial litter N concentration. Release of N from decomposing litter was slow, despite rapid DM decomposition. It was concluded that a major cause of declining productivity in sown grass pastures is the immobilization of N in decomposing grass litter.

Chickpea is the most important pulse crop of the arid and semi-arid areas. In India, it is cultivated during winter, depending on soil moisture stored from the preceding summer rain, which is often inadequate to ensure a satisfactory crop.

In most such areas, saline ground water is the only source of supplementary irrigation to which chickpea, like other pulses, is highly sensitive (Maas & Hoffman 1977). Field observations indicate (Manchanda et al. 1981) that chickpea is more sensitive to chloridedominated than to sulphate-dominated saline water irrigation. Since most saline ground water and saline soils are dominated by chloride or sulphate salts, this study evaluated the effects of these salts on the yield and mineral composition of chickpea at different electrical conductivities. (ECe).

Shearing causes a rapid increase in plasma cortisol concentrations (Kilgour & de Langen 1970; Purchas 1973; Fulkerson & Jamieson 1982), indicating that acute physiological responses are associated with the procedure. Environmental stress before mating can result in a delay in the onset of oestrus (Doney et al. 1973) and a reduction in ovulation rates (Doney et al. 1976). Dobson (1988) demonstrated that shearing caused a reduction in the luteinizing hormone (LH) response to exogenous gonadotrophin releasing hormone (GnRH) in anoestrous ewes. Such a response to shearing could influence the incidence of oestrus and ovulation.