Showing papers in "The Journal of Agricultural Science in 1995"
TL;DR: It is demonstrated that the performance of lambs infected with nematode parasites can vary substantially when given feeds of a similar chemical composition.
Abstract: Two grazing experiments were undertaken to evaluate the effects of sulla (Hedysarum coronarium) which contains condensed tannins (CT) and lucerne (Medicago sativa), which does not contain CT, on the performance of parasitized and non-parasitized lambs. The work was carried out near Palmerston North, New Zealand in 1992 and 1993.Experiment 1 used lambs which were either genetically ‘conventional’ or ‘resistant’ to gastrointestinal nematodes and which had a naturally acquired heavy parasite burden (faecal egg count (FEC) 1300–2500 eggs per gram faeces (epg)). They were either drenched to remove all the parasites or remained undrenched when allocated to pure swards of either sulla or lucerne for the 28-day experimental period. Liveweight gains of drenched lambs were higher with sulla (mean 302 g/day) than with lucerne (mean 245 g/day; P < 0·02) and rates of gain were not reduced (P = 0·10) by genetic resistance to nematodes. Undrenched lambs had mean faecal egg counts of 1090–2220 epg after 28 days, with higher counts in lambs grazing lucerne than in those grazing sulla (P < 0·05). Lambs grazing lucerne also had a much lower average daily gain (ADG) (mean 50 g/day) than those grazing sulla (mean 206 g/day; P < 0·0001). Resistant lambs had reduced (P = 0·07) ADG in the sulla treatment only.In Expt 2, lambs with a relatively low worm burden (average FEC 250 epg) were either drenched to remove all worms or dosed with 20 000 Trichostrongylus colubriformis infective larvae and grazed on pure sulla or lucerne swards for 42 days. Drenched lambs had a similar liveweight gain (mean 190 g/day) and wool growth when grazing either sulla or lucerne. Undrenched lambs grazing sulla had a greater ADG (mean 129 g/day) than those grazing lucerne (mean −39 g/day; P < 0·0001) and a higher rate of wool growth from mid-side patches (P < 0·009) and larger wool fibre diameter (P < 0·05) than those grazing lucerne. Undrenched lambs grazing sulla had lower FECs (P < 0·05) on days 14, 21, 35 and 42 than those grazing lucerne and lower (P < 0·05) Trichostrongylus colubriformis worm burdens at slaughter. Undrenched lambs had less perineal faecal contamination when grazing sulla rather than lucerne. Parasite-induced anorexia was evident in the lambs grazing lucerne but not in those grazing sulla.These findings demonstrate that the performance of lambs infected with nematode parasites can vary substantially when given feeds of a similar chemical composition. The superior performance of lambs grazing sulla was probably caused by condensed tannins, which decrease protein degradation in the rumen and can increase post-ruminal protein availability.
342 citations
TL;DR: In this article, the composition of 17 different Danish cattle, pig and biogas plant-digested slurries was studied and the results were used to describe the main buffer components in the slurries, and to discover the most important chemical components necessary for modelling slurry pH.
Abstract: Slurry pH is of great importance for the regulation of ammonia volatilization from livestock slurry, and therefore more knowledge of the buffer system controlling pH is urgently needed for modelling ammonia losses from stored and surface-applied slurry. The composition of 17 different Danish cattle, pig and biogas plant-digested slurries was studied. The results were used to describe the main buffer components in the slurries, and to discover the most important chemical components necessary for modelling slurry pH. The results showed that the pH of slurry was mainly controlled by the species NH 4 +/NH 3 , CO 2 /HCO 3 - /CO 3 2- and CH 3 COOH/CH 3 COO - , and that ion pair formation did not change the ionic balance significantly. There were only trace amounts of Ca 2+ , Mg 2+ and inorganic phosphates in solution due to precipitation of CaCO 3 (calcite) and MgNH 4 PO 4 .6H 2 O (struvite). Measured electrical conductivities were found to be strongly correlated with the calculated ionic strength.
227 citations
TL;DR: Current models for determining yield and number of grains/m2, based on crop growth, are not adequate when N is deficient, because less radiation was intercepted and because radiation-use efficiency was lowered.
Abstract: The possible interacting effects of shading and N supply on number of grains of Triticum aestivum L. (cv. Buck Nandu) were investigated at Balcarce, Argentina, during the 1988/89 and 1989/90 growing seasons. Shading was imposed from c. 13 days before anthesis to 6 days after, and four rates of N fertilization were supplied within each shading treatment around the date of terminal spikelet formation. Water and other nutrients were not limiting. Total grain yield was strongly correlated with grain number/m 2 , regardless of shading or N supply. At the highest N rates, grain number and dry weight of spikes at anthesis were linearly related to a photothermal quotient, i.e. the ratio of intercepted photosynthetically active radiation (PAR) to mean temperature minus 4-5 °C, during the period from 20 days before anthesis to 10 days after. The response of grain number to the photothermal quotient was interpreted in terms of the supply of assimilates to the spike at anthesis, which determined flower survival. The response of dry weight of spikes to photothermal quotient was interpreted in terms of crop growth rate since there was a linear relationship between crop growth rate and intercepted radiation. The lowest N rates reduced the number of grains/m 2 , at any given photothermal quotient. Since the reduction in grain number also occurred at any given dry weight of spikes, it cannot be explained by a reduced supply of assimilates to the spikes. Groin number responded directly to the supply of N to the spike, probably through the survival of differentiated flowers. The relationship between spike growth rate and crop growth rate was not affected by N supply. Crop growth rate was reduced by reduced N supply, because less radiation was intercepted and because radiation-use efficiency was lowered. These results indicate that current models for determining yield and number of grains/m 2 , based on crop growth, are not adequate when N is deficient
203 citations
TL;DR: It is concluded that microbial N production was more efficient when dietary energy and N supply were synchronized and the efficiency of microbial protein synthesis was 11–20% greater in animals fed the synchronous diet than the asynchronous diet.
Abstract: The effects of synchronizing dietary energy and nitrogen supply in diets with a similar carbohydrate composition on microbial protein synthesis and rumen fermentation were examined in sheep. Two diets were formulated to be either synchronous (diet S) or asynchronous (diet A) for the hourly release of nitrogen (N) and energy to the rumen. Diet S contained (g/kg) 425 g wheat straw, 400 g winter barley, 150 grapeseed meal and 25 g minerals/vitamins and diet A contained 505 g wheat straw, 458.5 g winter barley, 11·5 g urea and 25 g minerals/vitamins. Both diets were fed at the rate of 1 kg/day in four equal portions, to four cannulated sheep, in two periods in a change-over design. Rumen ammonia concentrations followed the predicted hourly trend in N degradation with a peak 1 h after feeding of 10 mM for diet S and 16 mM for diet A before falling within 3 h of feeding to 4 ITIM in animals fed either diet. Rumen volatile fatty acid (VFA) concentrations followed the cyclical trend predicted by stoichiometric equations, whilst rumen VFA ratios were more stable than predicted in animals fed either diet. The observed content of rumen degradable protein and organic matter truly degraded in the rumen was similar for both diets. The increase in total CHO digested in the rumen observed with diet A (427 g/kg DM) compared with diet S (364 g/kg DM) can be attributed to the greater content of starch in the asynchronous diet, which had a high degradability. The efficiency of microbial protein synthesis (g N/kg OM truly degraded in the rumen) was 11–20% greater in animals fed the synchronous diet (S) than the asynchronous diet (A). It is concluded that microbial N production was more efficient when dietary energy and N supply were synchronized.
179 citations
TL;DR: In this paper, the authors examined whether PD concentrations in spot urine or plasma samples vary diurnally during a given feeding regime and if they reflect differences in daily PD excretion induced by varying feed intake.
Abstract: In ruminants, the urinary excretion of purine derivatives (PD) reflects the absorption of microbial purines and can be used as an index of microbial protein supply. The objective of this study, carried out in Aberdeen, 1992, was to examine whether PD concentrations in spot urine or plasma samples vary diurnally during a given feeding regime and if they reflect differences in daily PD excretion induced by varying feed intake. Sixteen sheep were offered ad libitum one of four diets (fresh weight basis, the rest of each diet being minerals and vitamins): (1) 99.9 % lucerne (pelleted); (2) 50 % hay, 30% barley, 9% fishmeal and 10% molasses; (3) 72% straw, 7% molasses and 20% molassed sugarbeet pulp; and (4) 97 % barley. Measurements were made for 1 week after a 2-week adaptation period. Urine was collected daily on days 1-4 and hourly on days 5-7. Hourly urine collection was achieved using a fraction collector. Plasma samples were collected hourly from 09.00 to 17.00 h on day 4. Feed intake varied considerably (347-1718 g DM/day) between diets and between animals. Daily excretion of PD (7.1-22.6 mmol/day) was linearly related to DM intake (r = 0.85, n = 16), and so was the microbial N supply (3.9-19.5 g N/day) estimated from daily PD excretion (r = 0.87). In hourly urine samples, the ratio of PD:creatinine concentrations showed no significant difference between sampling times, and was linearly correlated with the daily PD excretion (r = 0.92). Similarly, plasma PD concentration also showed little diurnal fluctuation. Glomerular filtration rate (GFR) increased with feed intake. Plasma PD was not well correlated with daily PD excretion in urine (r = 0.57). The tubular load of PD (plasma PD x GFR) was better correlated with the daily excretion (r = 0.80). It appears that when sheep are fed ad libitum, PD in spot urine may provide a practical indicator of microbial protein supply status.
142 citations
TL;DR: In this paper, the authors used a wind tunnel system to measure ammonia losses from surface-applied pig and cattle slurry on grass, stubble (wheat and maize) and arable land.
Abstract: Field experiments were carried out in Brittany (Western France) in 1993 to measure ammonia losses from surface-applied pig and cattle slurry. Experiments were conducted on grass, stubble (wheat and maize) and arable land using a wind tunnel system. Ammonia losses were followed during periods ranging from 20 to 96 h after slurry application. Rates of slurry applied varied from 40 to 200 m 3 /ha. In two experiments, losses from cattle slurry were respectively 75 and 54% of the ammoniacal nitrogen applied in the slurry. Ammonia emissions from pig slurry applied at a rate of 40 m 3 /ha, during spring and summer experiments, were higher on grass (45-63% of the total ammoniacal nitrogen applied) than on wheat stubble (37-45%). On average, 75% of the total loss in all experiments occurred within the first 15 h after spreading. Significant correlations were found between ammonia losses (kg N/ha) and mean soil temperature and slurry dry matter content (%) using simple linear regressions and stepwise procedures. The time of application was also found to influence the magnitude of ammonia loss: 83 % of the total loss occurred within 6 h when the slurry was applied at midday compared with 42 % when it was applied in the evening.
98 citations
TL;DR: The aim of this review is to illustrate how resistance problems have developed in four major fungicide classes.
Abstract: Until the early 1960s, the majority of available fungicides were what are now regarded as low resistance risk molecules e.g. dithiocarbamates, copper and sulphur preparations. Cases of resistance e.g. to organomercurial seed treatments by Pyrenophora graminea (Noble et al. 1966) and to sodium orthophenylphenate by Penicillium digitatum causing postharvest rot of lemons (Harding 1962) were known but were maybe not treated with the degree of seriousness they deserved. It was only when fungicide research introduced more active molecules with more specific modes of action that the problems escalated. The aim of this review is to illustrate how resistance problems have developed in four major fungicide classes.
91 citations
TL;DR: The severity of Septoria post-anthesis increased with increasing rate of fertilizer N by an average of 11·1% per 100 kg/ha N, but was unaffected by its timing of application, while dry matter production up to and including anthesis was unaffected.
Abstract: Field experiments were undertaken at the University of Wales, Aberystwyth over two seasons to investigate the effects of N fertilizer rate and timing on the development of Septoria diseases (principally Septoria tritici) in winter wheat and its subsequent effect on crop growth. Rates of 100, 200 and 300 kg/ha N were applied at GS23, GS30, or split (GS23/30/38) in 1985/86 and 100 and 250 kg/ha N at GS23, GS30, GS23/30, or GS23/30/37 in 1987/88. Foliar diseases were allowed to develop or were controlled with fungicide. Early disease levels were temporarily enhanced soon after N application and were greater at the higher rates of N. In April and June a significant correlation between disease infection and concentration of N in leaf tissue was shown. Despite differences in the level of early infection, dry matter production up to and including anthesis was unaffected by disease. Infection during grain filling caused premature senescence of the flag leaf which significantly reduced grain yield, primarily through a reduction in grain size. Loss of yield was directly related to severity of disease on the flag leaf in early July, with a yield loss of 0·45% for every 1% increase in disease infection. The severity of Septoria post-anthesis increased with increasing rate of fertilizer N by an average of 11·1% per 100 kg/ha N (translating to a potential yield loss of 5% for each 100 kg/ha N given as fertilizer), but was unaffected by its timing of application.
82 citations
TL;DR: In this paper, the authors investigated the effect of the timing of ploughing a 4-year-old ryegrass/white clover pasture and two winter cover crops on subsequent mineralization, nitrate leaching and growth and N uptake of the following wheat crops.
Abstract: Two field experiments at Canterbury, New Zealand during 1991–93 investigated the effect of the timing of ploughing a 4-year-old ryegrass/white clover pasture and the effect of two winter cover crops on subsequent N mineralization, nitrate leaching and growth and N uptake of the following wheat crops.Net N mineralization of organic N (of plant and soil origin) increased with increased fallow period between ploughing and leaching. The total amount of N accumulated in the profile by the start of winter ranged from 107 to 131 and from 42 to 45 kg N/ha for fallow treatments started in March and May respectively. Winter wheat (planted in May) had no effect on mineral N contents by the start of winter, whereas greenfeed (GF) oats (planted in March) significantly reduced the mineral N content in one year.Cumulative leaching losses over the first winter after ploughing-in pasture varied markedly between years in relation to rainfall amount and distribution. Leaching losses were greater from the March fallow (72–106 kg N/ha) than the May fallow treatments (8–52 kg N/ha). Winter wheat did not reduce leaching losses in either year. GF oats did not reduce losses in 1991/92, but losses in 1992/93, when major drainage events occurred late in the winter, were only c. 40% of those under fallow.Incorporation of a large amount (> 7 t/ha dry matter) of pasture or GF oat residue in spring depressed yield and total N uptake of the following spring wheat, largely due to net N immobilization which could be overcome by the application of fertilizer N.First-year treatments had very little residual effect in the second year. Leaching losses over the second winter (mean 142 kg N/ha) were largely unaffected by the extent of first year leaching losses. Second year leaching losses were greater than first year losses, probably due to the greater amount of mineral N at depth in the soil before the start of the second winter.
76 citations
TL;DR: In this paper, electrical conductivity was evaluated for estimating the nutrient content of cattle and pig slurries, and the relationship between EC and nutrient content was examined by correlation and linear regression analyses.
Abstract: Electrical conductivity was evaluated for estimating the nutrient content of cattle and pig slurries. Slurry samples were collected in 1991 from the storage tanks of 48 cattle and 10 pig units on commercial farms in Ireland. Samples were analysed for NH 4 + and total concentrations of Na, K, Ca, Mg and P. Electrical conductivity (EC) was measured on raw slurries (EC raw ) and on slurries diluted by 10 with water (EC dilute ). Relationships between EC and nutrient content were examined by correlation and linear regression analyses. In both slurry types, NH 4 + was the dominant cation with K + second in importance on a molar basis. Within each slurry type, the concentration of each of these cations was significantly correlated with EC. Using EC dilute gave more accurate predictions of concentrations than EC raw , but even EC raw was a better predictor than dry matter (DM) content. The linear relationships between NH 4 + or K + and EC dilute explained > 82 % of the variance within each slurry type. The P content in slurries was related better to DM than to EC. Since EC measurement could be by cheap, robust meters, its potential for on-farm use deserves further investigation.
67 citations
TL;DR: In this paper, a simple iterative model was developed to predict pH changes in slurry and validated by titrating 17 slurry samples collected from four cattle farms, seven pig farms and three biogas plants.
Abstract: Ammonia volatilization from stored slurry or surface-applied slurry in the field is strongly affected by pH. Thus a simple, iterative model was developed to predict pH changes in slurry. Concentrations of NH4+/NH3, CO2/HCO3-/CO32- and volatile fatty acids were input data to the model. The model was validated by titrating 17 slurry samples collected from four cattle farms, seven pig farms and three biogas plants. Predictions of pH agreed well for 14 slurries with titration data in the pH interval from 4 to 10. Simulations indicated that microbial degradation of VFA to methane and carbon dioxide resulted in a pH increase if the carbon dioxide produced was lost to the atmosphere. There was little change in pH if the produced carbon dioxide dissolved in the slurry.
TL;DR: The growth of sugarbeet (Beta vulgaris L.) seedlings was investigated under laboratory conditions in 1990 and 1991 and three phases were identified during heterotrophic growth in the dark, based on the changes in dry weight, carbon and nitrogen contents.
Abstract: The growth of sugarbeet (Beta vulgaris L.) seedlings was investigated under laboratory conditions in 1990 and 1991. Three phases were identified during heterotrophic growth in the dark, based on the changes in dry weight, carbon and nitrogen contents. The perispermic reserves were first transferred to the young seedling. All the components of the seedling (cotyledons, hypocotyl, radicle) began to elongate and their dry weights increased. The seedling separated from the seed at the end of this first period, 4 days after imbibition had started at 20 °C. During the second period, there was a major redistribution of material between organs, mainly from cotyledons to the hypocotyl. The different organs elongated rapidly. From the start of the third period, 6 days after sowing at 20 °C, the organs began to lose weight and gradually ceased to elongate. The dry weights of the whole seedlings and of each organ were proportional to the initial seed weights. The elongations and changes in dry weights obtained at different temperatures coincided when time was expressed as thermal time using a base temperature of 3·5 °C. The growth of the seedling after illumination depended on the heterotrophic growth duration. If emergence occurred after 100 °Cd, the relative growth rate of the seedling decreased. In field conditions, plant variability at the end of sugarbeet establishment is due not only to variations in seed weights but also to environmental conditions that control emergence delay.
ADAS1
TL;DR: In this article, the results confirm that S deficiency is starting to appear in cereal crops in England and Wales and that ammonium sulphate was the more effective Sfertilizer source.
Abstract: In order to determine whether cereal crops require fertilizer sulphur (S) in areas estimated as receiving 10 kg/ha of S as gypsum at these sites. Yield responses were best predicted by a nitrogen: S concentration ratio ≥ 17:1 in leaf tissue at anthesis and a S concentration of ≤ 0·1% in the grain dry matter at harvest.Significant increases in total S and sulphate-S concentrations in leaf tissue at anthesis were obtained from increasing the rates of gypsum applied at ten of the sites, but a significant increase in the concentration of S in the grain at harvest was obtained at only one site. There was no difference in effectiveness between gypsum and foliar-applied elemental sulphur when compared at a single rate of 10 kg S/ha. Comparison of the increases in leaf-S status from maximum application rates of ammonium sulphate and gypsum suggested that ammonium sulphate was the more effective Sfertilizer source. The results confirm that S deficiency is starting to appear in cereal crops in England and Wales.
TL;DR: In this article, the authors measured the nitrate leaching in three pastures under three ley types: perennial ryegrass and white clover, a herbal ley comprising a mixture of legumes, non-aggressive grasses and deep rooting herbs, and perennial rhymes, with 400 kg N/ha per year as urea.
Abstract: Nitrate leaching was measured under three pastures – perennial ryegrass and white clover, a herbal ley comprising a mixture of legumes, non-aggressive grasses and deep rooting herbs, and perennial ryegrass fertilized with 400 kg N/ha per year as urea – from 1989 to 1991 at Palmerston North, New Zealand (latitude 40° S). The pastures were regularly mob-grazed by sheep at a stocking rate which varied with the amount of feed available. Drainage was estimated from a daily soil water balance and accumulated over 10 day intervals. Nitrate concentrations in the drainage were measured as the volume-averaged concentrations in the soil solution between 30 and 45 cm depth during these intervals. Although the N applied as fertilizer to the grass was 2·5 times greater than the N estimated to have been fixed by the clover-based pastures, the leaching loss from the former was 6–7 times greater than from the latter. The stocking rate on the grass pasture averaged over each year was only 1·2–1·4 times that on the two clover-based pastures. Leaching from urine patches was estimated to account for 55% of the total N leached from the clover-based pastures, but only 25% of the total leached from the N-fertilized grass. The amount of NO 3 -N leached should be related to the cumulative drainage to determine whether the average nitrate concentration exceeds the environmental safety limit of 10 mg NO 3 -N/1. In 1989, when the total drainage was 215 mm, 21·5 kg N/ha would have had to be leached for the concentration to exceed the limit and none of the pastures did so. In 1990, when the total drainage was 270 mm, the critical amount to be leached was 27 kg N/ha which was exceeded by the Grass + N400, but not by either the Grass-clover (5.8 kg N/ha) or the Herbal ley (7·3 kg N/ha). The utilization of N was more conservative in the clover-based pastures than in the N-fertilized grass.
TL;DR: The nutritional potential of a number of raw tropical seeds was assessed in a series of feeding trials with rats as discussed by the authors, and lectin reactivity was also monitored, α-amylase and trypsin inhibitory activities were determined in some of the seeds.
Abstract: The nutritional potential of a number of raw tropical seeds was assessed in a series of feeding trials with rats. Seed lectin reactivity was also monitored, α-amylase and trypsin inhibitory activities were determined in some of the seeds.Abelmosclius esculentus, Chenopodium quinoa, Delonix regia, Macroptilium lathyroides, Papaver sonmiferum, Parkia biglandulosa, Sesbania arabica, Terminalia catappa, Vigna subterranea, Vigna umbellata and Vigna unguiculata seeds supported moderate rat growth. The seeds contained only low levels of essentially non-toxic lectin, moderate amounts of trypsin inhibitors and negligible quantities of a-amylase inhibitors and they have great potential as dietary protein sources for man and animals.Artocarpus altilis, Canavalia ensiformis, Canavalia maritima, Dioclea grandiflora, Phaseolus acutifolius, Phaseolus coccineus and Phaseolus vulgaris cv. Processor, cv. Rosinha G2 and cv. Carioca 80 seeds were toxic. These seeds contained high levels of potentially toxic lectins. Other antinutritional factors may also have contributed to the high oral toxicity of some of these seeds.Albizia adinocephala, Albizia lebbeck, Bauhinia violacea, Cassia nodosa, Cassia tora, Dioclea sclerocarpa, Entada phaseoloides, Enterolobium cyclocarpum, Leucaena leucocephala and Moringa oleifera seeds were also highly toxic but had only low levels of essentially non-toxic lectins suggesting that the toxicity was due to other anti-nutritional factors.Bauhinia reticulata, Macrotyloma uniflorum and Tamarindus indica proteins were poorly digested and utilized. The seeds contained low levels of lectins which agglutinated only rat and cattle erythrocytes which had been pre-treated with suitable proteases. Brownea macrophylla had a similar lectin reactivity.
TL;DR: In this paper, the effect of incorporating a mature cover crop on subsequent N transformations was examined in a field trial containing a winter cover crop of Merced rye and a fallow control in Salinas, California.
Abstract: Winter non-leguminous cover crops are included in crop rotations to decrease nitrate (NO 3 -N) leaching and increase soil organic matter. This study examined the effect of incorporating a mature cover crop on subsequent N transformations. A field trial containing a winter cover crop of Merced rye and a fallow control was established in December 1991 in Salinas, California. The rye was grown for 16 weeks, so that plants had headed and were senescing, resulting in residue which was difficult to incorporate and slow to decompose. Frequent sampling of the surface soil (0-15 cm) showed that net mineralizable N (anaerobic incubation) rapidly increased, then decreased shortly after tillage in both treatments, but that sustained increases in net mineralizable N and microbial biomass N in the cover-cropped soils did not occur until after irrigation, 20 days after incorporation. Soil NO 3 -N was significantly reduced compared to winter-fallow soil at that time. A 15 N experiment examined the fate of N fertilizer, applied in cylinders at a rate of 12 kg 15 N/ha at lettuce planting, and measured in the soil, microbial biomass and lettuce plants after 32 days. In the cover-cropped soil, 59% of the 15 N was recovered in the microbial biomass, compared to 21 % in the winter-bare soil. The dry weight, total N and 15 N content of the lettuce in the cover-cropped cylinders were significantly lower; 28 v. 39% of applied 15 N was recovered in the lettuce in the cover-cropped and winter-bare soils, respectively. At harvest, the N content of the lettuce in the cover-cropped soil remained lower, and microbial biomass N was higher than in winter-bare soils. These data indicate that delayed cover crop incorporation resulted in net microbial immobilization which extended into the period of high crop demand and reduced N availability to the crop
TL;DR: The results suggest that N remobilization may be an important drought adaptation strategy under moderate or intermittent moisture deficits.
Abstract: Field and glasshouse studies were conducted in Durango, Mexico in 1987 and in East Lansing, Michigan, USA in 1989, respectively, to determine the effects of moisture deficits upon N-use efficiency (NUE), N partitioning and remobilization, and N harvest index (NHI) in edible beans (Phaseolus vulgaris L.). Four indeterminate, semi-prostrate genotypes adapted to the semi-arid high plains of Mexico, Pinto Nacional-1, Durango 222, L1213–2 and Bayo Madero, were used in the field study and Pinto Nacional-1 and Bayo Madero were used in the glasshouse study. A Xerosol Haplic soil was used in the field study and a Spinks loamy sand in the glasshouse study. A moisture deficit was induced by use of temporary rainshelters in the field and curtailment of water in the glasshouse. Plants were sampled periodically and subdivided into leaves, stems, pods and flowers, and roots (in the glasshouse study only) for determination of dry weight and total N content. Water-use efficiency was determined in the glasshouse study. A moderate moisture deficit (drought intensity index 0·41) reduced yield by 41% in comparison with non-stressed yield (from 134·3 down to 79·2 g/m2) and resulted in a greater percentage of seed-N derived from N that had been redistributed from the leaf, indicating that N partitioning was not impaired by this degree of stress. In contrast, N remobilization was greatly reduced by a more severe moisture deficit (drought intensity index 0·92), which resulted in yield losses of 92% (from 2·19 down to 0·17 g/pot). These results suggest that N remobilization may be an important drought adaptation strategy under moderate or intermittent moisture deficits. Severe moisture deficits reduced NHI, harvest index (HI), NUE and water-use efficiency (WUE) when WUE was expressed as seed dry weight per litre water used. Genotypic variability was observed for NHI, HI and NUE.
TL;DR: The principal finding was that CT in Lotus pedunculatus were able to affect the digestibility of both grass and lotus when fed together, and that as little as 1·8% of CT in the dietary DM had a substantial effect on rumen function.
Abstract: A feeding trial was undertaken in Palmerston North, New Zealand in 1991, to determine the extent to which condensed tannins (CT) in Lotus pedunculatus were able to affect the nutritive value of ryegrass (which does not contain CT) for sheep. The trial involved three groups of 11 male cryptorchid sheep held in metabolism crates so that intakes, digestibilities and nitrogen balances could be measured over a 42-day feeding period. One group was fed freshly cut ryegrass (Lolium perenne L.) as a sole diet (Grass group) and the other two groups were given a mixture of about one third freshly cut lotus and two thirds ryegrass (dry matter (DM) basis). This mixture contained c. 1·8% CT in the DM. One group given the mixed diet was drenched twice daily with polyethylene glycol (PEG; PEG group) to bind and remove the effects of the CT from the diet, whilst those not drenched were designated the ‘Tannin’ group. Intakes of all groups were constrained to that of the Grass group of sheep.Condensed tannins in the lotus had a major effect on the digestion of ryegrass. When the forages were immature, apparent digestibility of nitrogen (N) was substantially reduced in the Tannin sheep (65·3%)compared to the PEG (77·5%) and Grass (77·9%) groups (P < 0·001). With mature forages, the respective values were 48·8, 62·5 and 53·7% (P < 0·01). Rumen ammonia concentrations and plasma urea concentrations were also reduced by CT. Condensed tannins reduced DM digestibility by 3·7 percentage units (P < 0·05) mainly through the effects on N digestion. Concentrations of acetate, propionate and butyrate in rumen liquor were not affected by treatment, but CT reduced the proportions of the minor volatile fatty acids (VFA; isobutyrate, valerate and isovalerate). Treatment did not affect liveweight gain (131—164 g/day), or wool growth from mid-side patches, and N retention was not reduced by CT, so that the nutritive value of the forage was maintained despite the reduction in N digestibility. The principal finding was that CT in Lotus pedunculatus were able to affect the digestibility of both grass and lotus when fed together, and that as little as 1·8% of CT in the dietary DM had a substantial effect on rumen function.
TL;DR: It was concluded that the low rumination time may indicate rapid disintegration of chicory in the rumen to < 1 mm critical particle size, and that particle breakdown and rumen fractional outflow rate should be measured in future experiments with deer fed on chicory.
Abstract: Pure chicory (Cichorium intybus) and perennial ryegrass (Lolium perenne) forages were cut and fed fresh at Palmerston North, New Zealand, during March 1993 to castrated male red deer kept indoors in metabolism crates. Chicory contained lower levels of dry matter, higher levels of ash, and had a higher ratio of readily fermentable: structural carbohydrate than perennial ryegrass. Apparent digestibility of organic matter was highest for chicory (0·81 v. 0·72), but cellulose apparent digestibility was highest for perennial ryegrass (0·71 v. 0·59). Relative to perennial ryegrass, the rumen fluid of deer fed chicory contained higher concentrations of protozoa, ammonia and total volatile fatty acids (VFA) but had a lower pH at 15.00 h. Chicory-fed deer had higher rumen VFA molar proportions of n-butyrate and a higher acetate: propionate ratio. Total eating time and chews during feeding/g dry matter intake were similar for deer fed the two forages, but deer fed chicory spent much less time ruminating (33 v. 270 min/day) and had fewer rumination boluses (38 v. 305/day). It was concluded that the low rumination time may indicate rapid disintegration of chicory in the rumen to < 1 mm critical particle size, and that particle breakdown and rumen fractional outflow rate should be measured in future experiments with deer fed on chicory.
TL;DR: In this paper, the chlorophyll fluorescence parameters ΔF/Fm′ and Fv′/fm′, related respectively to the quantum yield of photosynthetic electron transport and to the efficiency of excitation capture by the open centres of photosystem II, have been evaluated as possible indicators of drought tolerance in durum wheat.
Abstract: The chlorophyll fluorescence parameters ΔF/Fm′ and Fv′/Fm′, related respectively to the quantum yield of photosynthetic electron transport and to the efficiency of excitation capture by the open centres of photosystem II, have been evaluated as possible indicators of drought tolerance in durum wheat. ΔF/Fm′ and Fv′/Fm′ measurements were carried out on excised leaves, both control and dehydrated, of 25 cultivars. ΔF/Fm′ and Fv′/Fm′ values were obtained at two times after the start of fluorescence measurement: at 14 s, i.e. during the induction curve (ΔF/Fm′14s and Fv′/Fm′14s) and at 200s, i.e. at steady state fluorescence (ΔF/Fm′200s and Fv′/Fm′200s).In dehydrated leaves a mean significant decrease of 20% (P < 0·001) was observed in ΔF/Fm′14s values. In contrast, no great differences were observed between control and dehydrated leaves with regard to ΔF/Fm′200s, Fv′/Fm′14s and Fv′/Fm′200s.The percentage decrease of ΔF/Fm′14s after dehydration was correlated with the drought susceptibility index (DSI) of the cultivars, evaluated on a yield basis and a significant correlation (r = 0·72, P < 0·001) was found.
TL;DR: The results suggest that stolon carbohydrate content is an important factor in the overwintering of white clover, there is a considerable amount of genetic variation in cold tolerance within white clovers, artificial freezing tests can provide a method of predicting the survival of clover stolons during winter and the cold hardiness ofwhite clover increases with time spent at temperatures near 0 °C under short day lengths.
Abstract: Changes in the stolon carbohydrate contents (water-soluble and total non-structural) of four white clover populations were measured at the beginning and end of winter. Three of the populations were of Swiss origin ― two of these were from high-altitude pastures, and the other from a valley location. Grasslands Huia was measured as a control variety. Levels of both types of carbohydrate declined during the winter in all populations. The Swiss populations from high altitudes contained the highest levels of both carbohydrate types. An artificial freezing test was carried out on stolon segments collected from a range of clover populations (including the two high-altitude Swiss clovers) growing in field plots in January, and values of «lethal dose 50» (LD 50 ) were calculated. The two Swiss populations had the lowest LD 50 values, indicating a greater intrinsic tolerance to freezing in those plants than in the other populations (of lowland temperate origin). One of the Swiss populations, Ac3785, was grown under two temperature regimes and short daylength to determine whether its tolerance to freezing increased with time. Significant increases in tolerance occurred after 8 days at 2°C, but plants grown at 8°C showed no change in tolerance even after 30 days. The results suggest that (i) stolon carbohydrate content is an important factor in the overwintering of white clover, (ii) there is a considerable amount of genetic variation in cold tolerance within white clover, (iii) artificial freezing tests can provide a method of predicting the survival of clover stolons during winter and (iv) the cold hardiness of white clover increases with time spent at temperatures near 0°C under short daylengths
TL;DR: Yields did not differ greatly with straw or cultivation systems, although there were clear effects of take-all in those years when the disease was most severe, and eyespot and sharp eyespot were both slightly but significantly less severe where straw was incorporated than where it was burnt.
Abstract: Disposal methods for straw from continuous winter wheat were tested on two soil types, a flinty silty clay loam and a sandy loam, over 7 years (1985–91). The methods tested were burnt or chopped straw in full factorial combination with four cultivation methods (tined to 10 cm, tined to 10 cm then to 20 cm; ploughed to 20 cm; tined to 10 cm then ploughed to 20 cm). Measurements were taken to determine the effects on crop establishment and growth, pest and disease incidence, and the consequent effects on yield. Another experiment (1985–91) on the flinty silty clay loam site, investigated the interactions between straw treatments (burnt, baled or chopped in plots that were all shallow cultivated to 10 cm) and five other factors; namely, time of cultivation, insecticides, molluscicides, fungicides and autumn nitrogen. All the straw x cultivation systems allowed satisfactory crops to be established but repeated incorporation of straw using shallow, non-inversion cultivations resulted in very severe grass-weed problems. Early crop growth, as measured by above-ground dry matter production, was frequently decreased by straw residues, but the effect rarely persisted beyond anthesis. Pests were not a problem and their numbers were not greatly affected either by straw or cultivation treatments, apart from yellow cereal fly which, especially on the heavier soil, was decreased by treatments which left much straw debris on the soil surface. Incorporating straw also caused no serious increases in the incidence of diseases. Indeed, averaged over all sites and years, eyespot and sharp eyespot were both slightly but significantly less severe where straw was incorporated than where it was burnt. Eyespot, and even more consistently sharp eyespot, were often more severe after ploughing than after shallow, non-inversion cultivations. Effects on take-all were complex but straw residues had much smaller effects than cultivations. Initially the disease increased most rapidly in the shallow cultivated plots but these also tended to go into the decline phase more quickly so that in the fourth year (fifth cereal crop) take-all was greater in the ploughed than in the shallow cultivated plots. On average, yields did not differ greatly with straw or cultivation systems, although there were clear effects of take-all in those years when the disease was most severe. In the last 2 years, yields were limited by the presence of grass weeds in the plots testing chopped straw incorporated by tining to 10 cm.
TL;DR: It appeared that a feeding duration of 5 h per day was adequate for maintenance but insufficient for optimum production of indigenous goats in Zimbabwe.
Abstract: The feeding behaviour of indigenous goats grazing on natural vegetation in a semi-arid region of Zimbabwe was studied over five seasons covering a period of one year (March 1989 to March 1990). The goats were randomly allocated to two groups, A and B, which grazed for 8 h (08.00-16.00 h) and 5 h (11.00-16.00 h) daily, respectively. These grazing times were based on the current practices of smallholder farmers. The botanical and chemical composition of the diet was determined by analysing samples collected from oesophageal fistulated goats. Daily feed intake was estimated by the total faecal collection method. Feed selection varied markedly with season and was similar in both groups. From January to March (wet season) grass formed 55-70% of the forage consumed, while from May to early November (dry period) browse, herbs and fruits formed 77-91% of the diet. Dietary crude protein levels ranged from 128 to 157 g/kg over the seasons. Neutral detergent fibre content ranged from 590 to 790 g/kg, and was highest in wet months and lowest in dry months. Feed intake ranged from 33 to 60 g/kg BW 0.75 or 16-28 g/kg of body weight. It appeared that a feeding duration of 5 h per day was adequate for maintenance but insufficient for optimum production
TL;DR: In this article, composites of herbage and faecal samples from studies with sheep provided the experimental material used to evaluate a series of modifications which would simplify and reduce the workload involved in the chemical analysis.
Abstract: The evaluation of n-alkane concentrations in herbage and faeces is the basis of a methodology that yields precise estimates of herbage intake. Established chemical analysis procedures for the determination of n-alkane concentrations in herbage and faecal samples involve an elaborate sequence of steps utilizing n-hexane as solvent for both the liquid-liquid extraction of n-alkanes from the sample and the solid-phase separation of n-alkanes in the extract. Composites of herbage and faecal samples from studies with sheep provided the experimental material used to evaluate a series of modifications which would simplify and reduce the workload involved in the chemical analysis. The results show that a less hazardous chemical, n-heptane, can replace n-hexane at all stages of the analytical procedure. They also show that evaporation of the sample extract and redissolving it prior to the separation of the n-alkanes, using a silica gel column, is unnecessary and that the volume of solvent used can be reduced. Procedures for saponification of samples prior to extraction can also be simplified as the process can be run overnight involving a slow build-up of temperature to 90 °C. The gain in precision from processing samples in duplicate was negligible and it would be more appropriate to invest extra efforts on an increased number of experimental animals. The results snowed that the workload and cost of using the n-alkane technique to estimate herbage intake can be reduced substantially.
TL;DR: Partitioning was the most important yield component affecting yield variation among cultivars, and the Sahelian cultivars 796, 55–437 and TS 32–1 were the most consistent for drought tolerance.
Abstract: A 2–year study (1990 and 1991) was conducted at the ICRISAT (International Crops Research Institute for the Semi-Arid Tropics) Sahelian Centre, near Niamey, Niger, to select groundnut cultivars tolerant to drought and to examine selection techniques. Thirty-six cultivars known to vary in yield potential were grown under rainfed and irrigated conditions. Crop growth rate (C) and partitioning co-efficient (p) were estimated from phenological and final harvest data. The correlation between years was greater for partitioning than for pod yield (implying a higher heritability for p than for yield). Tolerance as determined by a drought susceptibility index for pod yield (SY), crop growth rate (Sc) and partitioning (Sp) to reproductive sinks showed thirteen cultivars as drought tolerant for either C or p or for both. The Sahelian cultivars 796, 55–437 and TS 32–1 were the most consistent for drought tolerance. Partitioning was the most important yield component affecting yield variation among cultivars.
TL;DR: It was calculated that sambar selected a total diet higher in condensed tannins and lignin but lower in nitrogen than that selected by red deer, with similar values for total fibre and OMD.
Abstract: Grazing sambar and red deer in New Zealand were offered a free choice of seven different plant species (forage legumes, browse and grasses) in 1992 and 1993 and dietary preference rankings were determined. Nutritive value of plants on offer and diet selected, plant height, plant species purity and stem diameter selected (browse only) were also determined. Total nitrogen (N) and organic matter digestibility (OMD) were highest for red clover, lowest for grasses and intermediate for browse species (willow, poplar and lupin). Top dietary preference ranking was willow for sambar and red clover for red deer in both years, with Yorkshire fog and prairie grass being lowly preference ranked with both deer species. Sambar selected willow stems up to 38 mm in diameter and poplar stems up to 54 mm in diameter. When the plants were grouped into browse, grass and forage legume categories, both deer species showed a similar preference ranking for grasses. Relative to grasses, sambar showed a strong preference for browse and a low preference for forage legumes, whilst red deer showed a strong preference for forage legumes of high nutritive value and a very low preference for browse. It was calculated that sambar selected a total diet higher in condensed tannins and lignin but lower in nitrogen than that selected by red deer, with similar values for total fibre and OMD. Differences in dietary preference between the two deer species may be linked with the greater ability of sambar deer to neutralize some plant secondary compounds and their more efficient rumination pattern compared with red deer. Both sambar and red deer can be classified as intermediate feeders, having a similar preference for grasses, but differing preferences for forage legumes and browse.
TL;DR: The authors compared six 2-course rotations, in which barley alternated with feed legumes (pure or mixed with barley), fallow or barley, in partial factorial combination with different N and P fertilizer regimes.
Abstract: Trials were established at two sites in 1982 to compare six 2-course rotations, in which barley alternated with feed legumes (pure or mixed with barley), fallow or barley, in partial factorial combination with different N and P fertilizer regimes. This paper summarizes data from the second to the seventh cropping seasons.Barley yielded most after fallow and more after legumes than after barley; but, on the basis of total dry matter production over both courses, barley-legume rotations outyielded barley-fallow and barley-barley rotations. In terms of net nitrogen offtake, which may be taken as a rough measure of feed value, barley-legumes surpassed the other rotations by c. 100% at both sites, whether the comparison was made on values obtained from plots with or without added fertilizer. Of the legumes, Lathyrus sativus was slightly more productive than Vicia saliva, and this carried over into the rotational yield of both dry matter and nitrogen. Rotations involving pure legumes were slightly more productive than those involving legume/barley mixtures.Yields of all crops and rotations varied greatly from year to year depending on rainfall. Those of the barley-fallow rotation were much less variable than those of the barley-barley rotation at the wetter site (323±103 mm), with the barley-legume rotation intermediate; but variability was much greater at the drier site (250±79 mm), with much less difference between rotations. Nevertheless, fertilizer use and rotations including legumes gave a significant yield advantage under the driest conditions.
TL;DR: It was concluded that increasing the proportion of concentrates in grass silage-based diets increased carcass weight gain per MJ of metabolizable energy consumed and tended to reduce carcass fatness.
Abstract: Isoenergetic diets containing grass silage and concentrates in the ratios 75:25; 50:50 and 30:70 on a dry matter (DM) basis were offered to 42 beef heifers, which were initially 361 kg liveweight, for 115 days in 1987 at Hillsborough, Northern Ireland. Half of the animals given each forage concentrate ratio were given one of two crude protein (CP) intakes in a 3 × 2 factorial design. The silage contained 152 g CP/kg DM, 94 g ammonia-N/kg total N and 734 g digestible organic matter/kg DM. Concentrates were based on barley and soyabean meal and were formulated to equalize CP intakes for the three forage: concentrate ratios. For diets containing 75, 50 and 30% silage, metabolizable energy intakes were 94, 92 and 87 MJ/day; liveweight gains 0·99, 1·07 and 1·12 (S.E. 0·051) kg/day; carcass gains 0·61, 0·64 and 0·67 (S.E. 0·033) kg/day; carcass lean concentrations (estimated from dissection of fore-rib joints) 636, 642 and 648 (S.E. 4·7) g/kg and carcass fat concentrations 204, 199 and 194 (S.E. 5·3) g/kg. Increasing protein intake did not affect performance, but increased carcass fat concentration at all three forage concentrate ratios. It was concluded that increasing the proportion of concentrates in grass silage-based diets increased carcass weight gain per MJ of metabolizable energy consumed and tended to reduce carcass fatness. Contrary to previous findings with young growing cattle, increasing protein intake did not alleviate the problem of greater fat deposition in finishing cattle given high-silage diets, but rather significantly increased carcass fat concentration.
TL;DR: The results suggest that selection for weaning weight has altered the dynamics of protein metabolism in lambs, principally through alterations in protein breakdown in muscle.
Abstract: The physiological consequences of selection for weaning weight were investigated using 14-month-old castrated male Merino lambs from lines selected for (W +) and against (W −) weight at weaning for over 10 generations. The selection experiment commenced in 1953 and was conducted at Trangie, NSW, Australia. Lambs from these lines now differ by 42% in weight at weaning and maturity, and have a proportionately similar composition of protein, fat and ash in their bodies at similar stages of maturity. In the whole body, there were no apparent between-strain differences in protein synthesis, but W + lambs had lower (P < 0.05) rates of phenylalanine oxidation than W − lambs. In hind limb muscle, protein metabolism of W + lambs was more responsive to food intake than in W − lambs. In particular, the rate of change of protein degradation differed (P < 0.05) between the lines in response to food intake per unit liveweight with protein degradation decreasing with increased feed intake in W + lambs. W + lambs had lower (P < 0.05) rates of blood flow to, and used less (P < 0.05) oxygen per kg hind limb muscle than W − lambs. Endocrine differences between the lines included increased (P < 0.05) plasma insulin-like growth factor-I (IGF-I) concentration in W + compared to W − lambs and, from regression analysis, an indication that there was a higher (P < 0.01) response in hind limb protein gain to insulin in the W + lambs. These results suggest that selection for weaning weight has altered the dynamics of protein metabolism in lambs, principally through alterations in protein breakdown in muscle. Moreover, they suggest that there are associated genetic differences in endocrine control of protein metabolism which involve insulin and possibly IGF-I
TL;DR: Calves which had been restricted in either of the early periods had significantly improved food conversion efficiency during the compensating period but lifetime food efficiency was not affected by plane of nutrition in early life.
Abstract: Low, medium and high planes of nutrition were imposed on Friesian calves from 1 to 13 weeks of age (Period 1) and factorially arranged with low and high planes of nutrition in the 13–25 week period (Period 2). In the final (residual) period, from 25 weeks to slaughter, all animals were given the same high plane diet comprising 3·5 kg of concentrates and grass silage ad libitum. The different planes of nutrition were achieved by offering restricted allowances of milk replacer or concentrates with grass silage ad libitum. Representative animals were slaughtered at 1, 13 and 25 weeks of age while the remaining animals were slaughtered at mean liveweights of 503 and 553 kg. Over 2 years, a total of 120 Friesian steers were taken through to the final slaughter point, with 60 additional animals being slaughtered at interim stages. The animals were housed in non-bedded accommodation throughout the study and the calves were born in January of each year. The ME intake of the low plane animals in Period 1 was 0·55 that of the high plane animals and produced liveweight (LW), empty body (EBW), carcass (CW), non-carcass (NCW) and alimentary tract (ALW) weight gains which were 0·60, 0·46, 0·47, 0·44 and 0·55 of the gains of the high plane animals. In Period 2 the low plane animals had ME intakes which were 0·69 of the high plane animals and produced proportional gains of 0·57, 0·48, 0·45, 0·51 and 0·56 respectively. Previously restricted animals had higher rates of gain subsequently and the indices for weight compensation by the final slaughter point in LW, EBW, CW, NCW and ALW for the low plane treatments in Period 1 were 0·72, 0·82, 0·89, 0·73 and 0·97 while indices for low v. high in Period 2 were 0·82, 0·82, 0·79, 0·86 and 0·95. With lower plane animals, food intakes/liveweight0·75 were significantly higher during the compensating period. Calves which had been restricted in either of the early periods had significantly improved food conversion efficiency during the compensating period but lifetime food efficiency was not affected by plane of nutrition in early life.