The effect of breeding for the absence of condensed tannins in the testa of Vicia faba L. on resistance to foot rot, Ascochyta blight and chocolate spot diseases was investigated in 1988–92 at Wageningen, The Netherlands. For this purpose the disease development in tannin-free and tannin-containing partners of six near-isogenic pairs was compared after exposure to causative pathogens. Except for one near-isogenic pair, in which both partner lines showed a relatively high resistance, the tannin-free lines were more susceptible to foot rot than the tannin-containing partners of the same pair. This observation indicates that the presence of condensed tannins in the testa prevents infection of the plant by the causative pathogens. Fusarium oxysporum and F. solani, isolated from faba bean tissues showing foot rot symptoms, were shown to be primary foot rot pathogens, while F. avenaceum caused wilting of young plantlets. No pathogenic isolates were obtained from F. tabacinum. Resistance to Botrytis fabae (chocolate spot disease), scored on leaves and stems under glasshouse and field conditions in 1992, was not influenced by selection for the absence of condensed tannins which occur in the testa of mature seeds. Under the same environmental conditions, leaves, stems, pods and seeds of tannin-free lines showed similar levels of damage due to Ascochyta fabae (Ascochyta blight) as the tannin-containing partner lines of the same near-isogenic pair. These results indicate that condensed tannins do not play a role in resistance to both B. fabae and A. fabae, probably because, except for the seeds, these polyphenols do not accumulate in the tissues affected by these pathogens.

The response of late-sown mustard (Brassica juncea L.) to four rates of irrigation (ratio of irrigation depth to cumulative pan evaporation, ID:CPE = 0·2, 0·4, 0·6 and 0·8) and nitrogen (0, 30, 60 and 90 kg/ha) was investigated at Haryana Agricultural University, India, in the winter seasons of 1986/87 and 1987/88. Increases in the amounts of water and N fertilizer applied increased leaf water potential, stomatal conductance, light absorption, leaf area index, seed yield and evapotranspiration and decreased canopy temperature. Water-use efficiency was highest for the 0·4 ID:CPE irrigation treatment in both seasons, and for the 60 kg N/ha N treatment in 1986/87 and the 90 kg N/ha treatment in 1987/88. The combination of 0·6 ID:CPE with 60 kg N/ha gave a significantly higher seed yield than lower rates and equalled that from the highest irrigation and N treatment combinations. The amount of water used by the mustard crop decreased with increasing soil depth irrespective of treatment. In the deeper soil layers, the percentage of total moisture use was greater under less irrigated than under more frequently irrigated plots. Leaf area index showed a significant positive linear relationship with evapotranspiration and light absorption and a negative linear relationship with canopy temperature. Seed yield was linearly related to leaf area index and light absorption coefficient.

A programme of forage legume evaluation was developed at the International Livestock Centre for Africa's (ILCA) subhumid research site in Nigeria from 1985 onwards. Evaluation included monitoring herbage and seed yields, incidence of diseases/pests, regeneration ability and persistence for three growing seasons. This was followed by an in situ bioassay to determine the direct effect of the sown legumes on maize (Zea mays L.) production in the absence of added nitrogen.

The results for selected accessions from introductions received in 1987 and 1988 are presented. Stylosanthes guianensis CIAT184 (ILCA164) and ILCA15557 and Aeschynomene histrix ILCA 12463 were promising both in terms of biomass production (up to 9·4, 3·4 and 9·6 t/ha respectively) and quality (all had crude protein values of 11% or more), and in terms of beneficial effects for maize production (all plots gave significantly more grain than those with no legume, reaching over 3 t/ha for maize grown on plots after S. guianensis ILCA15557). The use of such appropriate forage legumes to enhance both livestock and crop production in a sustainable farming system is recommended.

In 1991 and 1992, four sets of isogenic lines and eight released cultivars of pea (Pisum sativum L.) differing at the loci af (normal leaflets are converted to tendrils) and st (reduced stipule size) were grown in conventional plot stands at Göttingen, Germany. Crops were either supported by wire netting, to avoid the negative effects of lodging on yield, or were unsupported, thus permitting natural lodging, in order to study the effect of both genes on yield.

The conventional, normal-leafed plant type (AFAF STST) exhibited the highest yield potential, but also the largest yield reduction due to natural lodging. Yield potential of the ‘semi-leafless’ plant type (afaf STST) was less than that of the conventional type but, due to its better standing ability, the yield of the unsupported, ‘semi-leafless’ crop, on average, was less reduced by lodging than was the yield of the conventional one. With the additional reduction in stipule size by the gene st, the decrease in yield potential was too large to be counterbalanced by the positive effects of an improved standing ability. For the released cultivars, the effects of both genes on crop performance were smaller than for the isogenic lines.

Summary Between 1985 and 1988, 14 field experiments at different sites in the UK assessed the effect of applying P, K, Na and Mg in autumn, early spring, late spring or as a split application in both autumn and late spring on the growth, yield and processing quality of sugarbeet. Supplementary experiments compared Kaynitro and Chilean nitrate of soda. None of the treatments had any effect on plant population densities, and any differences in sugar yield could be explained by the leaching of Na. The effects on processing quality were inconsistent and unlikely to be of agronomic or economic significance. Generally, Kaynitro and Chilean nitrate of soda performed no better than the other fertilizers so it is unlikely that their extra cost would be justified. Apart from Na, the timing of nutrient application appeared to be unimportant, even on soils of low fertility. However, Na, being very mobile, was best applied in spring.

The ability of 12 Scottish Blackface ewes to discriminate and concentrate grazing activity in nitrogenfertilized heather patches was determined. The nitrogen content of a stand of heather (Calluna vulgaris) was increased and the fibre content decreased by adding ammonium nitrate fertilizer (7·5 g N/m2) 3 months prior to grazing, in Scotland during August 1991, to selected areas within a patchwork array. The sheep were offered either a high protein (300 g soyabean meal) or low protein (285 g ground barley) supplement daily before being allowed to graze within the heather mosaic during November 1991. The proportion of time spent grazing in fertilized and control patches (patch selection) and the proportion of daylight hours spent grazing (proportion of time spent grazing) was estimated for individual sheep for 6 days. Rumen ammonia concentrations were determined at the end of the grazing period. All animals spent approximately twice as much time grazing in fertilized as in control patches. About half of the daylight hours were spent grazing. The nature of the supplement did not influence patch selection, the proportion of time spent grazing or rumen ammonia concentrations. It was concluded that sheep are able to discern differences in the chemical composition of heather on a fine scale and that their foraging behaviour is not influenced by the type of supplement offered.

The effects of inoculation by Ascochyta fabae Speg. on growth and light interception in field bean (Vicia faba L.) were studied. Measurements were made in a field trial using cv. Ticol, a cultivar vulnerable to this disease during early vegetative growth and at the beginning of the flowering stage. Infection reduced leaf area duration, light interception and dry matter yield of energy (light use efficiency) and, consequently, the dry matter production of the crop. Reductions in seed yield ranged from 12 to 30% compared with a prophylactic fungicide treatment.

Substrates for mushroom cultivation were prepared, following a 2 day mixing and blending process, in bulk tunnels under a controlled temperature regime using forced ventilation. The temperature regime was based on a conventional bulk tunnel composting process, i.e. pasteurization at 60 °C for 6 h, followed by a conditioning phase at 47 °C until the substrate was clear of ammonia. With the exception of ammonia, which increased with increasing compost nitrogen content, this process did not result in strong odours. The substrates were ready for inoculation with mushroom ‘spawn’ 7–12 days after the initial mixing of the compost ingredients. Increasing the compost nitrogen content from 1·1 to 2·5% of the dry matter by increasing the quantity of deep litter poultry manure added to straw in the ingredients resulted in a greater subsequent yield of mushrooms. Further increases in the substrate nitrogen content resulted in prolonged tunnel processing times, substrate desiccation, incomplete clearance of ammonia from the substrate and subsequently low or no mushroom yields. Substrate bulk density at the time of spawning decreased with increasing nitrogen content, but was increased by chopping the straw ingredient. Mushroom yields from composts prepared with barley straw were significantly lower than those from wheat straw composts, at equivalent nitrogen contents. Supplementation of prepared substrates with the proprietary protein-rich ingredient, Betamyl 1000, increased yields by 13·6%.

An experiment was conducted to investigate the effects of planting pigeonpea in May, June or July at Mokwa and June or July at Shika and Kano, Nigeria at population densities of 18·5×103, 27·8×103, 55·5×103, 111×103, 222×103 and 444×103 plants/ha on dry matter (DM) and seed yields of cultivars Local, UQ50, 3D8103, 3D8104, 3D8111 and 3D8112 in the 1974/75 season. Planting in May had no above-ground DM yield advantage over planting in June at Mokwa. Planting in June gave higher yields than planting in July irrespective of site, except for the short, early maturing, soya-type cultivar 3D8103 at Shika. Cultivar responses to density were inconsistent between sites and also between dates at Shika and Kano. Cultivars Local, UQ50 and 3D8104 showed the highest DM yield at all sites. Leaf DM yield tended to decline as planting was delayed but was highest at densities of 111×103 or 222×103 plants/ha for May and June-planted cultivars Local, UQ50, 3D8104 and 3D8112, which showed potential as feed supplements for poultry. Reasons were advanced for the variability in pod yield responses to planting date and density between the different pigeonpea cultivars. Root DM yields were proportional to above-ground DM yield but, over all cultivars, root yield was unaffected by planting date at Shika.

Seed yield was highest from the June sowing, cv. 3D8104 was the most productive and the optimum densities were 27·8×103 plants/ha for the larger-sized cultivars Local and UQ50, 55·5×103 plants/ha for the medium-sized cultivars 3D8104, 3D8111 and 3D8112, and 444×10 3 for cv. 3D8103. A complementary study over 13 years showed that the seed yield of intermediate and late maturing pigeonpeas was strongly and linearly related to total annual rainfall.

Fine wool in China is characterized by severe dust contamination and substantial tip weathering. In an attempt to improve wool quality, synthetic rugs were fitted to ewes and a range of raw wool characteristics was monitored. Two trials were carried out in successive years: a pilot trial (June 1985 to June 1986) involving 100 ewes wearing rugs and 75 controls, and a main trial (June 1986 to June 1987) involving 250 ewes with rugs and 250 controls. The rugs were fitted to ewes after shearing and remained on until shearing the following year. Wool from ewes with rugs was significantly better in almost all the characteristics measured (P <0·05) than wool from sheep without rugs. Clean fleece weight was improved by 15% over the two trials, yield and wax content were increased, and dust content and dust penetration were substantially reduced. Staple length and strength were increased, and dust content and dust penetration were substantially reduced in the main trial. Several style characteristics were measured using a prototype image analysis system and these also showed wool from sheep wearing rugs as being of better quality than wool from sheep in the control group. The only negative result was an increase in yellowness, in the greasy state only, due to the higher wax content in the sheep wearing rugs and the yellow nature of the wax of Gansu Alpine Finewool sheep – probably due to their genetic background. Wool from sheep wearing rugs would be expected to perform better in processing than wool from unrugged sheep.

Ferrous iron is oxidized and precipitated as iron ochre in field drains. In drainage waters taken from an ochre-producing site near Aberdeen, Scotland in 1987, iron deposition was inhibited by the addition of humic and fulvic acids, which form complexes with Fe(II). The inhibition was dependent on the concentrations of soluble humic materials and the proportion of Fe complexed. Iron deposition in the presence of humic substances is discussed in relation to the amount of the cation which is complexed and its oxidation state.

The effects of infection with T. vivax in mid- or late pregnancy on food intake and utilization, liveweight changes, abortion rate and lamb growth rate were investigated in West African Dwarf ewes at lbadan, Nigeria in 1990. Rate of liveweight gain by ewes infected during mid-pregnancy (IMH) was16 g/day compared with 33 and 37 g/day for the uninfected ewes offered medium (CM) or high (CH) plane diets. Although digestibility coefficients were not affected, intake of digestible organic matter was higher in CH ewes than in IMH and CM ewes. Nitrogen retention at mid-pregnancy on a metabolic size basis was higher in CH ewes than in CM and IMH ewes.

Lamb birth weight and survival rate were lower in infected ewes. Ewes infected in mid-pregnancy (IMH) and in late pregnancy (ILH) had mean birth weights of 1·4 and 1·0 kg compared with CM and CH ewes, which had mean birth weights of 1·9 and 2·0 kg respectively. Observed survival rates were 63, 15, 75 and 80% for lambs nursed by IMH, ILH, CM and CH ewes respectively. During the first 6 weeks postpartum, lamb growth rate in all groups did not differ. However, during weeks 7–12 postpartum, lambs nursed by IMH ewes had significantly lower growth rates. Weaning weight was also lower in lambs from IMH (5·0 kg) dams than in lambs from CM and CH dams (7·1 kg). Infection during late pregnancy was more severe and all infected ewes lost weight due to reduced feed intake and fever. T. vivax infection in sheep is responsible for reproductive wastage, abortion, poor lamb growth and ewe mortality.

A field experiment was conducted in Canterbury, New Zealand to investigate the effect of six leguminous and non-leguminous grain crops on soil N fertility over a 12 month period (March 1989 to March 1990). All crops had an overall negative N balance during their growing season. A greater amount of soil N was removed by barley, rape and lupins (104–119 kg N/ha) than by field beans, field peas or lentils (50–74 kg N/ha).

Net N mineralization was measured in all treatments between residue incorporation and the start of winter. With the exception of the lupins, accumulation of mineral N in the soil profile before the start of winter drainage was greater following leguminous (mean 124 kg N/ha) than non-leguminous crops (mean 80 kg N/ha).

Cumulative apparent leaching losses over the autumn/winter were largely a reflection of the mineral N content of the profile before the start of drainage. Excluding lupins, leaching losses declined in the order fallow > legumes > non-legumes (110 > 72 > 37 kg N/ha respectively). The anomalous results for the lupins were attributed to the incorporation of a large amount of woody residues after harvest which may well have resulted in extensive net N mineralization occurring later in the autumn.

Over a 12 month period, all treatments showed a decline in N fertility (110–160 kg N/ha), although compared with barley, the total loss of soil N was 10–40 kg N/ha less following leguminous crops.

Growth of the following spring wheat test crop was affected by the preceding crop. Grain yield, grain N yield and total N yield were significantly related to the mineral N content of the soil at the end of leaching, and to a measure of net N mineralization during the growing season of the test crop.

Artificially reared sambar (tropical) deer and red (temperate) deer were confined indoors in metabolism cages and fed chaffed lucerne hay ad libitum for 4-week periods during summer and winter at Flock House Agricultural Centre, New Zealand, during 1992. Measurements were made of voluntary feed intake (VFI), apparent digestibility, faeces particle size distribution, eating and ruminating time and the rate of chewing during eating and ruminating. Red deer reduced VFI (kg DMI/day) markedly from summer to winter, associated with a reduction in the duration of each eating bout. Sambar deer slightly increased VFI over this time, associated with an increase in chewing frequency. Digestive efficiency was similar in both species, and the critical particle size for leaving the rumen was passage through a 1 mm sieve for both species. Time spent eating/g DMI was greater for sambar deer than for red deer during summer, but there was no difference during winter. Relative to red deer, sambar deer consistently spent more time ruminating/g DMI, and spent a greater proportion of total ruminating time as daytime ruminating and had more daytime ruminating bouts. Duration of each ruminating bout (min) was similar for the two deer species, but sambar deer had less chews/bolus ruminated but more rumination boli/h than red deer. Differences between sambar deer and red deer were more pronounced in ruminating than in eating behaviour, and sambar deer may have evolved a different rumination pattern to break down low-quality tropical forages more effectively.

In field drainage waters, Fe(II) can be oxidized to Fe(III), which is precipitated as iron ochre. At a farm near Aberdeen, Scotland, ochre is precipitated both chemically and biologically. The precipitation was delayed using the antibiotic D-threo-chloramphenicol and Cu(II) ions. Iron deposition was delayed on glass slides coated with copper filings. It is suggested that the incorporation and slow release of substances which inhibit ochre formation, from drainage pipe material, would be a valuable method of controlling the ochre problem.

The effects of trypanosomiasis on digestible organic matter intake, milk yield and composition, dam liveweight changes during lactation and lamb growth rates were investigated at Ibadan, Nigeria 1991/92, using 20 West African Dwarf sheep nursing single lambs. Although digestibility coefficients were neither affected by infection nor by level of feed intake, organic matter intake during early and late lactation was significantly lower in infected dams. Nitrogen retained in late lactation was lower in infected animals due to reduced feed intake. Mean daily milk yields were not affected by the infection during early lactation; however, during the second half of lactation, average daily milk yields were significantly lower in infected animals than in uninfected controls. Variations in milk component concentrations between experimental groups did not attain statistical significance throughout lactation. While control ewes on a high plane of nutrition (CH) gained 12·1 g/day, infected ewes (IH) and uninfected control ewes on a medium plane of nutrition (CM) lost 45 and 5·4 g/day respectively during lactation. Liveweight gain in the lambs was not affected by infection in the dams.

This study demonstrated reduction in feed intake, late lactation milk yield and dam liveweight gain with no adverse effect on digestibility coefficients, milk composition, early lactation milk yield and lamb weight gain during T. vivaxinfection of lactating ewes.

Lotus pedunculatus was grown under high fertility conditions and its nutritive value was determined in a feeding trial with sheep at Palmerston North, New Zealand in 1989. The condensed tannins (CT) accounted for 5·5 % of lotus dry matter (DM) and its effect on digestion was evaluated by giving an intraruminal infusion of polyethylene glycol (PEG) to six of the sheep (PEG group). PEG preferentially binds with CT so that the lotus becomes essentially CT-free.

The experiment was carried out with 14 sheep (six PEG and eight ‘Tannin’) held in metabolism crates indoors and given freshly cut lotus hourly, for 32 days. This paper presents data relating to carbohydrate and mineral digestion, together with aspects of rumen function.

Digestibility of lotus DM was 68%, and the digestibility of fibre was not affected by CT. Infusion of PEG increased rumen concentrations of NH3 and volatile fatty acids (P < 0·001) but effects on molar ratios of VFA were inconsistent with time. CT reduced rumen degradation and absorption of sulphur and increased net absorption of both phosphorus and zinc, but other effects on mineral digestion were small.

Although the lotus was offered at c. 90% of ad libitum, intakes of the tannin sheep began to decline after c. 15 days of feeding and were c. 12% lower than those of the PEG sheep at the end of the trial (P < 0·05). At slaughter, rumen pool sizes were similar for the two treatments but the Tannin sheep had a lower fractional outflow rate, which suggests a slower rate of digestion in the rumen. Growth rate and wool production were similar for sheep on both treatments. It is concluded that the CT in Lotus pedunculatus grown under high fertility conditions had little effect on fibre and mineral digestion but the depression in DM intake reduced its nutritive value for sheep.

In three separate experiments, groups of four, three and six mature, rumen-cannulated Simmental cows were fed diets designed to supply different quantities of energy (E) and nitrogen (N) to the rumen microbes. Experiment 1 (straw plus concentrate plus urea) had balanced E and N supplies; Expt 2 (hay and four levels of soyabean meal) had different sub-optimum N levels at the same intake as Expt 1; and Expt 3 (hay plus maize plus two levels of urea) reproduced the N shortage in Expt 2 at a higher level of intake.

The amount of total N excreted in the urine (TUN) was 574 mg/kg LW0·75 in Expt 1 and 420 mg/kg LW0·75 of this N was excreted as total purine nitrogen (TPN). In Expt 2, TUN increased significantly (P < 0·05) with increasing soyabean levels; TPN also increased, reaching the level observed in Expt 1 when soyabean meal supplementation was highest. In Expt 3, TUN and TPN increased with increasing dietary urea concentrations; TUN and TPN were always higher than in Expts 1 and 2.

Estimated microbial nitrogen supply (EMNS, based on TPN) was always considerably lower than estimates based on fermentable non-protein OM and crude protein (EMNR-EN) or an assumed yield of microbial N per kg OM apparently digested in the rumen (EMNR-OM). Regression analyses of EMNS on EMNR-EN, EMNR-OM or OM intake had moderate r2 values (0·76, 0·65 and 0·62 respectively) but the constant terms were significantly different from zero. The regressions of EMNR-EN and EMNR-OM on TPN gave angular coefficients of 15·81 and 11·47 respectively.

The correlation between rumen liquid parameters (total count, bacterial DM, ATP and nitrogen) and OM intake, EMNS or EMNR increased with sampling time (from 09.00 to 16.00 h). The EMNR-OM produced correlation coefficients similar to those obtained with OM intake; these correlations were numerically higher than those obtained with EMNS or EMNR-EN.

Three experiments were conducted in Mérida, Mexico, between 1987 and 1990 in which jack beans, treated in various ways, were included in chick diets at the rate of 300 g/kg diet. The diets were balanced by appropriate supplementation to provide the same concentrations of energy, minerals, vitamins and principal essential amino acids as control diets based on maize or sorghum and soyabean meal. Boiling jack beans or soaking and shaking them and the combination of boiling with soaking and shaking were studied with a view to removing or inactivating toxic factors and enhancing the utilization of the beans as a livestock feed. A fourth experiment was conducted to evaluate the contribution of canavanine to the deleterious effect observed when broiler chicks are fed diets containing treated jack beans and to examine the effect of canavanine on the efficiency of protein retention of broiler chicks.

Boiling for 1 or 2 h reduced the toxicity of jack beans, but chick growth rate was only half that of controls. The combination of boiling, followed by soaking and shaking, removed most of the jack beans’ anti-nutritional factors, but some toxic effects were left in the beans, causing a depression of c. 10% in feed intake and growth rate. Growth, feed intake and protein utilization of chicks were not affected when canavanine was added to a sorghum-soyabean diet at a level (3·5 g/kg diet) which matched the canavanine present in a diet containing 300 g/kg boiled jack beans.

It was concluded that boiling was a satisfactory procedure for the inactivation of the heat-labile lectins in jack beans and that soaking and shaking was an effective method of reducing canavanine and the haemolytic activity of the saponins in jack beans. However, canavanine was found not to be the main toxic or anti-nutritional factor present in jack beans.

Four experiments were conducted in the Yucatán, Mexico, in 1991 and 1992 to study feed intake in 24 h trials with chicks and pigs fed diets containing either raw or treated jack beans or conventional diets with added canavanine.

Feed intake of chicks in the first hour was markedly reduced and feed intake of pigs was severely reduced when raw jack beans (300 g/kg for chicks, 250 g/kg for pigs) were included in their diets. Feed intake of pigs diminished to a greater extent than that of chicks when treated beans (300 g/kg) were included in the diet. Short-term feed intake of chicks was not affected when canavanine (3·5 g/kg) was added to a sorghum-soyabean diet. However, pigs showed a large drop in feed intake when canavanine was added to a maize-soya diet at only 0·8 g/kg. It was concluded that in both species the anti-nutritional factors in jack beans cause a rapid reduction in feed intake which precedes a depression in growth rate. The initial feed intake depression in pigs could be partly attributed to canavanine remaining in the jack beans after treatment. In the chicks' case, however, rejection of a diet containing treated jack bean was due to anti-nutritional factor(s) other than residual canavanine.