Effects of spray application parameters on foliar uptake and translocation of daminozide and 2,4-D-triethanolamine in Vicia faba

The uptake and translocation of daminozide and the triethanolamine salt of 2,4-D(2,4-D-TEOA) were determined radiochemically 24 h after application to leaves of Vicia faba (field bean). Chemicals were applied in aqueous solutions as monosize spray drops of varying diameters (50–500 μm), the volume median diameter (VMD):number median diameter (NMD) ratio of the droplet spectra being < 1 · 03. Daminozide was applied at concentrations of 0·17–2·4 g/l in volumes of 10–90 l/ha, providing doses of 5–215 g/ha. 2,4-D-TEOA was applied at 0·20–5·0 g acid equivalent (a.e.) per litre in 20–190 l/ha to provide doses of 4–420 g a.e. per hectare. Uptake of daminozide was 9·3 ± 2·6% (mean ± standard deviation), of which 26 ± 4·4% was translocated out of the treated leaflet, with 25 ± 6·5% of the translocated ¹⁴C being redistributed in an acropetal direction. Equivalent values for 2,4-D-TEOA were: 16 ± 5·5% uptake, 70 ± 8·0% translocation and 12 ± 4·9% acropetal redistribution. The quantity of both chemicals taken up increased with increasing dose (r² > 0·92). Multiple regression analyses demonstrated that the efficiency of uptake (%) of both chemicals was not related to drop size or number, leaf coverage, concentration of active ingredient (a.i.) or application volume. For both chemicals, percentage uptake was inversely related to applied dose, and uptake and translocation were interrelated.     

The effect of accumulation period and harvest date in spring on dry-matter yield and forage quality in mixed swards containing Lolium spp. and Trifolium subterraneum in Western Australia

The object of this study was to determine the effect of closing date and date of harvest for conservation (accumulation period), on dry‐matter (DM) yield and forage quality of annual pasture in Western Australia. The field study comprised 48 plots, 2 m × 2 m, sown with either annual ryegrass (Lolium rigidum Gaud.) or Italian ryegrass (L. multiflorum Lam.), and mixed with subterranean clover (Trifolium subterraneum L.). Defoliation of swards until the end of winter was at the three leaves tiller^–1 stage. In spring, once stem nodal development had commenced, swards were defoliated every 3–4 weeks. Swards were defoliated either twice with three leaves tiller^–1 (accumulation period 1 commenced on 15 August); twice with three leaves tiller^–1 and then once after 4 weeks (accumulation period 2 commenced on 11 September); twice with three leaves tiller^–1 and then twice after 4‐week intervals (accumulation period 3 commenced on 9 October) or; twice with 3 leaves tiller^–1 and then twice after 4‐week intervals and then once after 3 weeks (accumulation period 4 commenced on 30 October). From the commencement of the accumulation period, tiller density, DM yield and forage quality were determined weekly for up to 10 weeks. There was a positive quadratic association between DM yield and days after the commencement of the accumulation period. Yields were maximized from accumulation period 1 with 5·3, 6·6 and 9·5 t DM ha^–1, and growth rates were 140, 128 and 145 kg DM ha^–1 d^–1, for Wimmera annual ryegrass and Richmond and Concord cultivars of Italian ryegrass respectively. In contrast, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with days after the commencement of the accumulation period, and initial values were greater than 0·80 and 180 g kg DM^–1 for IVDMD and CP content respectively. The rate of decline in IVDMD d^–1 for Wimmera annual ryegrass was 0·005, 0·019 and 0·012 d^–1 for accumulation periods 1, 2 and 3, respectively, while for Italian ryegrass cultivars Richmond was 0·015, 0·011, 0·02 and 0·012 d^–1 and Concord was 0·014, 0·009, 0·013 and 0·01 d^–1, for the 4 accumulation periods respectively. It is recommended that annual and Italian ryegrass pastures be harvested between 10% and 20% inflorescence emergence when IVDMD will exceed 0·70 regardless of cultivar and/or defoliation practice prior to the commencement of the accumulation period.     

Modelling the Contribution ofAlpha-Amylase,Beta-Amylase and Limit Dextrinase to Starch Degradation During Mashing

Response surface methodology was used to determine the levels ofalpha-amylase,beta-amylase and limit dextrinase enzymes required for efficient conversion of starch to fermentable sugars during mashing. Micro-scale mashes with purified barley starch and malt enzymes were performed in a Brewing Research Foundation mash bath, and mash liquors were analysed for solubilised starch, reducing sugars (neocuproine assay) and fementable sugars (anion exchange HPLC). Fermentable sugars in the mash liquor were positively correlated with reducing sugars (R²=0·94) and the percentage of starch solubilised during mashing (R²=0·68). A multiple regression equation relating the levels of the three starch degrading enzymes to the percentage of starch hydrolysed to fermentable sugars gave a good fit to the second order response surface (R²=1·00, RMSE=1·37%). Addition of limit dextrinase to the mashes resulted in a substantial increase in levels of fermentable sugars, and limit dextrinase showed a synergistic effect in increasing levels of maltose in the mash liquor when combined with high levels ofbeta-amylase. The efficiency of any one starch degrading enzyme in a mash is influenced by the presence of other starch degrading enzymes. Commercial malts contain excess levels ofbeta-amylase and below optimal levels of limit dextrinase. Malt extract may not be a good indicator of the level of fermentable carbohydrates produced during mashing.     

Genetic and environmental variation in the diastatic power of australian barley

Variation in the diastatic power of Australian barley, and the relationships between diastatic power and the starch-degrading enzymes contributing to diastatic power, were investigated in 11 cultivars of barley grown at six diverse locations in Australia. Diastatic power varied with genotype and location, with the levels ranging from 3·1 to 16·5 U/kg. For alpha-amylase activity, levels across cultivar and location ranged from 52 to 214 U/g, for beta-amylase activity they ranged from 201 to 1550 U/g; and, for limit dextrinase activity, they ranged from 56 to 636 U/kg. Alpha-amylase (r = 0·64) and beta-amylase (r=0·77) activities were correlated more strongly with diastatic power than was limit dextrinase (r=0·37). Grain nitrogen content was correlated positively with diastatic power (r=0·71), largely because of the relationship between nitrogen content and beta-amylase activity (r=0·82). High grain nitrogen contents were also associated with small grain sizes (r=−0·76) and low hot-water extracts (r=−0·75). The levels of alpha-amylase activity were correlated more closely with limit dextrinase activity (r=0·65) than with beta-amylase activity (r=0·28). The results indicate the need to select barley cultivars separately for alpha-amylase and beta-amylase activities to achieve high levels of diastatic power.     

Variation in the degree of D-Xylose substitution in arabinoxylans extracted from a European wheat flour

Total water-extractable arabinoxylan from flour of the European bread making wheat cultivar Camp Remy was fractionated by ethanol precipitation. Both ¹H-NMR spectroscopy and methylation analysis of the isolated arabinoxylan fractions showed wide variation in the degree of xylose substitution. More highly substituted arabinoxylan fractions were precipitated at higher ethanol concentrations. At ethanol concentrations of 10–30% (v/v) (1→3),(1→4)-β-d-glucan co-precipitated with arabinoxylan. Re-precipitation of the polymer mixture resulted in a partial separation of the arabinoxylan from the mixture. Arabinoxylans with wide structural variation were also isolated by extraction of the flour with aqueous ethanol solutions of decreasing concentations. By this isolation technique, fractions with the highest degree of substitution were extracted with the most concentrated (50%) ethanolic solutions. The range of structural variation in the fractions was quite similar for both isolation methods. A decrease in the proportion of unsubstituted xylose residues occurred concomitantly with a decrease in the proportion of monosubstituted xylose units and with an increase in the proportion of disubstituted xylose units. An increase in the proportion of paired disubstituted xylose units as the arabinose to xylose ratio of the arabinoxylan fractions increased, and the presence of monosubstituted xylose residues next to disubstituted xylose residues in the highly substituted fractions, were illustrated by ¹H-NMR spectroscopy. Methylation analysis indicated an increase in traces of side chains of arabinose residues and in the levels of O-2 substituted xylose residues as the arabinose to xylose ratio increased.     

Water vapor transport parameters of a cast wheat gluten film

Understanding the mode of transport of water vapor through the film is important for improving the moisture barrier properties of wheat gluten (WG) films. Effective permeability (P_eff), solubility (S_eff), and diffusion (D_eff) coefficients of a hydrophilic cast WG film were determined at 25°C within the relative humidity (RH) range of 0–84% (with a 9–13% RH gradient between upstream and downstream water vapor flux). P_eff, S_eff, and D_eff increased substantially as the RH gradient moved upwards in the RH spectrum. P_eff increased by four orders of magnitude from the lowest RH condition of 0–11% (3.8×10⁻¹¹ g·m/m²·s·Pa) to the highest RH condition of 75–84% (4.1×10⁻⁷ g·m/m²·s·Pa). A moisture sorption isotherm of the film at 25°C was constructed. Both the Guggenheim–Anderson–DeBoer (GAB) and the Kuhn moisture sorption isotherm models showed a good fit to the experimental adsorption data. Testing of WG films at the expected conditions of actual use is necessary to quantify the water vapor permeation through the films.     

Effluent production from grass silages treated with additives and made in large-scale bunker silos

Data from twenty experiments, conducted at ADAS Research Centres in England and Wales during 1986–92, were used to determine effluent production from additive-treated grass silages made in large-scale bunker silos. The additives compared were formic acid at 4·0 l t^–1, rolled barley at 44·0 kg t^–1, dried molassed sugar beet feed at 40·0 kg t^–1 and liquid inoculants at 2·2 l t^–1 together with a non-additive-treated control. The silages were made from herbage with an average dry-matter (DM) content of 177 (s.e. 3·8) g kg^–1 and water-soluble carbohydrate content of 140 g kg^–1 DM. Average silage toluene DM content was 213 (s.e. 3·8) g kg^–1. The formic acid and sugar beet feed silages were both well fermented, whereas the other silages were less well fermented. Effluent produced was determined as either effluent production (l t^–1 grass ensiled) during the 52-d period in which it was measured or peak flow (l h^–1) during the first 2 d of ensilage. Compared with non-additive-treated silage, dried molassed sugar beet feed significantly reduced both effluent production (27%) and peak flow (36%). Formic acid significantly increased peak flow (51%), but had little effect upon effluent production, and significantly reduced effluent N and lactic acid content. Barley and inoculant treatment had no significant effect upon effluent production. In general, poor relationships were found between DM content and effluent production. Nevertheless for silages, except those treated with absorbents or formic acid, a significant (P < 0·001) negative relationship between silage effluent production (l t^–1 grass ensiled) and the DM (g kg^–1) content of the ensiled grass was found.     

NMR-baking and Multivariate Prediction of Instrumental Texture Parameters in Bread

To study the kinetics of the bread baking process, transverse relaxation (T₂) of protons was measured during a baking process performed inside the magnet of a pulsed low field¹H nuclear magnetic resonance (NMR) instrument. Experimental NMR relaxation data were analysed both by chemometric data analysis and by multi-exponential curve-fitting. Throughout the entire baking process from dough to bread three T₂-components were determined. During the NMR-baking process significant shifts were observed in the characteristic time constants at c. 55 °C (gelatinisation of starch) and at c. 85 °C. In a second experiment staling of white bread crumb aged 0–8 days was investigated by texture analysis and NMR relaxation. High correlations (r>0·9) between texture parameters and NMR relaxation data of bread crumb were found by partial least squares regression (PLSR) models. Firmness and elasticity as measured by a Texture Analyser were predicted with an estimated error (RMSECV) of 150 (range 200–2200) and 0·032 (range 0·4–0·7), respectively. Future texture of the bread samples was also predictable by use of NMR relaxation data from the early storage period (day 0 to day 3).     

‘MaxClover’ grazing experiment: I. Annual yields,botanical composition and growth rates of six dryland pastures over nine years

Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass‐white clover control and a lucerne monoculture were monitored for nine years. Total annual dry‐matter (10.0–18·5 t DM ha^?1) and sown legume yields from the lucerne monoculture exceeded those from the grass‐based pastures in all but one year. The lowest lucerne yield (10 t ha^?1 yr^?1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass‐based pasture. Yields were 8·7–13·0 t DM ha^?1 annually. Subterranean clover yields were 2·4–3·7 t ha^?1 in six of the nine years which represented 26–32% of total annual production. In all cocksfoot‐based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year (R² = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass‐white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year (R² = 0·94). By Year 9, 79% of the 6.6 t ha^?1 produced from the ryegrass‐white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450–780 mm yr^?1 rainfall should grow lucerne or cocksfoot‐subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed.     

Use of falling number and rapid visco analyser instruments to estimate sorghum malt diastatic power

Diastatic power (DP), a measure of joint alpha- and beta-amylase activities, is the most important quality criterion of sorghum malt. There is a need for a rapid method to estimate sorghum malt DP. Such methods have been developed using both the Falling Number (FN) and Rapid Visco Analyser (RVA) instruments, which measure alpha-amylase activity. Maize starch is used as substrate at a ratio of malt to maize starch of 1:29. Good estimates of DP can be obtained with malts prepared from grain of a single cultivar (FN, r = −0·872; RVA, r = −0·993). The estimate is less good with malts prepared from different cultivars (FN, r = −0·759; RVA, r = −0·759), probably a result of the different cultivars having varying proportions of alpha-amylase relative to DP. The methods are well suited, therefore, to quality control in maltings and breweries, but less suitable for evaluating the malting quality of different cultivars.     

Insecticidal control and economic damage of sugar-cane wireworm, Agrypnus variabilis (Candèze) in maize

Six insecticides (terbufos, chlorpyrifos, ethoprophos, phoxim, bendiocarb and lindane) were tested against sugar-cane wireworm Agrypnus variabilis (Candèze) in maize. The first five insecticides were applied at 0·25, 0·5 and 0·75 kg a.i./ha (2·27, 4·55 and 6·82 g a.i./100 metres of row) while lindane was applied at the registered rate of 0·29 kg a.i./ha (2·64 g a.i./100 metres of row). In addition, bendiocarb was applied as a seed treatment at the rates of 4000 and 6000 ppm. The insecticides were applied at planting as insecticide/fertilizer mixtures in 18 cm wide bands, 2–3 cm below the soil surface and 3–5 cm above the seed. The minimum effective rates were terbufos 0·25 kg a.i./ha, lindane 0·25 kg a.i./ha and chlorpyrifos and ethoprophos both at 0·5 kg a.i./ha. These treatments gave at least 5 weeks' residual control. The bendiocarb seed treatments were phytotoxic. No residues were detected in the cobs or grain at the minimum effective rates of the terbufos, chlorpyrifos or ethoprophos treatments. The positive linear relationship between plant population and yield showed that for every 1% loss in plant stand below the optimum range of 60 000–65 000 plants/ha, there is a 0·72-0·74% loss in grain yield respectively. Control measures would be economically justified with only a 2·3% reduction in plant stand (assuming $20/ha for cost of control and $150/tonne for maize).     

Influence of Technological Modifications of the Protein Network from Pasta on in vitro Starch Degradation

The pasta protein network limits starch hydrolysis rate in vivo leading to low post-prandial glycemia. To better understand the mechanisms involved, various pasta products were processed to obtain protein network structures differing from that in reference pasta extruded at 40 °C and dried 17 h at 55 °C. After cooking, pasta strands were submitted to in vitro alpha -amylolysis. Compared to reference pasta, higher extrusion temperature (70 °C), high-temperature drying treatment (2 h at 90 °C) or autoclaving (115 °C for 15 or 40 min) had no marked effect on the rate of dextrin release from pasta particles. Protein enrichment at a 20%-level and flour fractionation-reconstruction with removal of insoluble fibre before pasta extrusion significantly (p<0·05) delayed (≥1 h) the rate of dextrin release (−14% at 8 h). Confocal laser scanning microscopy allowed the three-dimensional structure of the protein network from protein-enriched pasta to be observed, and suggested that increased starch encapsulation may explain the reduced accessibility of starch to alpha -amylases. A stronger cohesiveness between starch and protein, due to insoluble fibre removal, was probably responsible for the decrease of starch accessibility to alpha -amylase in fractionated-reconstructed flour pasta. Modified geometrical characteristics (e.gtortuosity) of the protein network were not correlated with starch degradation rates.     

Effect of Triticum monococcum glutenin loci on cookie making quality and on predictive tests for bread making quality

The effects of Triticum monococcum glutenin loci on cookie making quality and predictive tests for bread making quality were evaluated in recombinant substitution lines (RSLs) between chromosome 1A^m from T. monococcum and chromosome 1A from Chinese Spring. All four combinations of high molecular weight (H M_r-GS) and low molecular weight glutenin alleles (L M_r-GS) were studied in a factorial design to evaluate their interactions. Grain protein content was used as a covariable to evaluate the effect of these loci independently of the variation in protein content among lines. No significant interactions were detected indicating an additive effect. RSLs carrying the HM_r -GS from T. monococcum showed a 13·6% increase in SDS sedimentation volume (p=0·004) and a significant reduction in cookie diameter (−5·2%,p =0·02), and cookie quality (−6·8%, p=0·02). RSLs carrying the LM_r -GS from T. monococcum showed a significant decrease in the proportion of polymeric protein (−2·8%, p<0·0001), SDS sedimentation volume (−8·1%,p =0·03) and gluten strength (−16·5%, p=0·01), and a significant increase in cookie quality (5·9%, p=0·05). The T. monococcum LM_r. -GS allele has potential value to be used in soft wheat breeding programs. These results suggest that diploid T. monococcum could be a valuable source for new allelic variation for storage proteins loci and new quality characteristics.     

Effect of formic acid and a bacterial inoculant on the amino acid composition of grass silage and on animal performance

An Italian ryegrass and hybrid ryegrass sward was harvested on 11 May 1994. The mean dry‐matter (DM) content of the herbage was 197 g kg^–1 fresh matter (FM), and mean nitrogen and water‐soluble carbohydrate contents were 20 and 272 g kg^–1 DM respectively. Approximately 72% of total nitrogen (TN) was in the form of protein‐nitrogen. The herbage was treated with either no additive, formic acid (3·3 l t^–1) (Add‐F, BP) or inoculant (2·3 l t^–1) (Live‐system, Genus) and ensiled in 100 t silos. Changes in effluent composition with time showed that silage fermentation and protein breakdown were delayed by treatment with formic acid. Formic acid and inoculant treatments also inhibited amino acid catabolism during ensilage. All silages were well fermented at opening with pH values < 4·0 and ammonia‐N concentrations of ≤ 50 g kg^–1 TN after 120 d ensilage. Treatment had an effect on protein breakdown as measured by free amino acid concentration, with values of 21·5, 18·2 and 13·2 mol kg^–1 N at opening (191 d) for untreated, formic acid‐treated and inoculated silages respectively. Amino acid catabolism occurred to the greatest extent in untreated silages with significant decreases in glutamic acid, lysine and arginine, and increases in gamma amino butyric acid and ornithine. The silages were offered ad libitum without concentrate supplementation to thirty‐six Charolais beef steers for a period of 69 d (mean live weight 401 kg). Silage dry‐matter intakes and liveweight gains were significantly (P < 0·05) higher on the treated silages. Silage dry‐matter intakes were 7·42, 8·41 and 8·23 kg d^–1 (s.e.d. 0·27) with liveweight gains of 0·66, 0·94 and 0·89 kg d^–1 (s.e.d. 0·058) for untreated, formic acid‐treated and inoculated silage‐fed cattle respectively. In conclusion, additives increased the intake of silage and liveweight gain by the beef steers, and it is suggested that this may be caused in part by the amino acid balance in these silages.     

Effects of inoculant treatment on silage fermentation, digestibility and intake by growing cattle

A changeover design experiment involving thirty-six 3-month-old Friesian male calves (mean initial live weight 127 kg) was carried out to evaluate a bacterial inoculant based on a single strain of Lactobacillus plantarum (Ecosyl, ICI) as a silage additive. On 25–31 August 1988, nine silages were harvested using double-chop forage harvesters from the second regrowth of three swards, namely permanent pasture which had received 100 kg N ha^?1 and perennial ryegrass which had received either 100 or 150 kg N ha^?1. Herbages (mean DM and WSC concentrations 144 and 11·2 g kg^?1 respectively) from each sward were treated with either no additive, formic acid (2·4 1 t^?1) or the inoculant (3·3·1 t^?1) and were ensiled in 126 silos of 0·8 t capacity. The only effects of the inoculant on chemical composition of the silages were a decrease in modified acid detergent fibre and an increase in endotoxin and crude and true protein concentrations. Silages were offered ad libitum and supplemented with 1·0 kg of concentrates per head daily for three periods each of 3 weeks in a partially balanced changeover design experiment. Digestibilities of the total diets were determined at the end of the experiment. For the untreated, formic acid-treated and inoculant-treated silages, silage dry matter intakes were respectively 3·58, 3·66 and 3·67 (s.e. 0·044) kg d^?1, estimated metabolizable energy (ME) intakes were 46·1, 46·7 and 47·1 (s.e. 0·44) MJ d^?1, energy digestibilities were 0·727, 0·727 and 0·738 (s.e. 0·0046) and organic matter digestibilities were 0·770, 0·771 and 0·788 (s.e. 0·0042). Rumen degradabilities of the silages were determined using two rumen-fistulated cows. Mean dry matter and nitrogen degradabilities for the control, formic acid-treated and inoculant-treated silages, assuming an outflow rate of 0·05 h^?1, were 10·508, 0·49, 0·491 and 0·702, 0·676 and 0·729. It is concluded that the inoculant significantly increased the digestibility of the silages but did not affect dry matter or ME intake.     

Influence of Non-Starch Polysaccharides Structure on the Metabolisable Energy of U.K. Wheat Fed to Poultry

With the inclusion of wheat in European poultry diets at 600 g/kg, or more, there is increasing concern that its apparent metabolisable energy (AME) is more variable than would be predicted by conventional analysis. Twelve samples of wheat with a range of AME values (8·34–13·74 MJ/kg dry matter when fed to broiler chicks aged 11–14 d at 750 g/kg diet) were used to investigate the causes of this variability. AME was not correlated with the amount of total water-soluble non-starch polysaccharide (sNSP), soluble arabinoxylan (the major polysaccharide contributing to NSP) or (1→3, 1→4)-β-glucan released from the grain or with the viscosity of aqueous extracts. Surprisingly,in vitroviscosity was negatively related to soluble (r²=0·61) and total (r²=0·82) arabinoxylan. This was thought to be due to the slow, but cumulative, action of endogenous hydrolases in the stored grain. Soluble NSP from each wheat was characterised by measurement of molecular weight distribution and the structural features of arabinoxylan determined from the amount and nature of the oligosaccharides released following treatment with an endo-xylanase. Oligomer molecular weight was determined by matrix-assisted laser desorption/ionisation time of flight mass spectrometry and structure by NMR. Multivariate analysis of the 32 variables measured provided a three-term model able to explain approximately 0·80 of the variation between wheat samples: AME=8·07+11·16(XRAX)+30·67(AX-6)−0·355(sNSP) Two terms (XRAX, the proportion of arabinoxylan resistant to hydrolysis by xylanase and AX-6, the properties of branched six-sugar present in hydrolysates) reflected the degree of branching of arabinoxylan and were positively associated with AME while the third term, the amount of sNSP present, was negatively related.     

The effects of silage harvesting system and supplementation of silage-based diets by protein and methionine hydroxy analogue on the performance of lactating cows

Three silages were produced by harvesting grass using either a flail (F), double-chop (DC) or a precision-chop (PC) forage harvester. Each silage was ensiled unwilted and with formic acid additive applied at the mean rate of 2·2 1 t^-1 of grass. All three silages were well preserved and had mean particle lengths of 54, 49 and 26 mm and digestible organic ma er in dry ma er (DOMD) values of 0·67,0·66 and 0·66 for the F, DC and PC silages, respectively. The three silages were offered ad libitum to three groups each of 21 British Friesian cows, with a mean calving date of 29 January, from day 8 of lactation until 9 April. Within each silage group all cows were offered 4·1 kg dry ma er (DM) d^-1 of a control supplement divided equally in two feeds and given during milking. In addition, 24 kg DM d^-1 of the control supplement (C), a high protein supplement (HP) or a supplement containing methionine hydroxy analogue (MHA) were given at midday. The mean crude protein contents of the total supplementary feeds given were 193 253.and 195gkg for the C, HP and MHA treatments, respectively. The treatment effects showed no significant interactions between silage harvesting system and type of supplement. Silage harvesting system influenced milk yield, with the mean yields over the final 21 days of the experiment being 26·1, 27·4 and 25·5 kg d^-1 for the F, DC and PC silages, respectively, and the difference between DC and PC achieved significance (P <0·05). However, the milk from cows given DC had a significantly lower concentration of fat (P <0·01) and silage harvesting system had no effect on the yield of fat or protein. The type of supplement had no significant effect on milk yield, with the mean yields over the final 21 days of the experiment being 264, 267 and 259 kg d^-1 for the C, HP and MHA supplements, respectively.     

Silage intake and milk production in cows given barley supplements of reduced ruminal degradability

Three change-over experiments were conducted to determine the effect on ad libitum silage intake and milk production in dairy cows of treatment of barley supplements with an acid-formaldehyde reagent designed to reduce the rate of starch and protein digestion in the rumen. In Experiment 1 there were six dietary treatments consisting of silage with supplements of 4·0,6·5 and 9·0 kg d^-1 of barley given untreated or treated with formaldehyde reagent (8·1 t^-1). In Experiment 2 there were four dietary treatments consisting of silage with supplements of barley (7·0 kg d^-1) or barley and fishmeal (6·0 kg d^-1 plus 1·0 kg d^-1), with the barley untreated or treated with formaldehyde reagent (15·1t^-1). In Experiment 3 there were four dietary treatments consisting of silage given alone or with supplements of barley (9·0 kg d^-1). Treated barley (15·1 t^-1, 9·0 kg d^-1) and barley plus sodium bicarbonate (9·0 kg d^-1 plus 25·0 g d^-1). Treatment of the barley supplement with formaldehyde reagent had no effect on silage intake or milk production in Experiment 1 where the rate of application of the reagent was low and the basal silage-barley diet was limiting in rumendegradable nitrogen. However, in Experiments 2 and 3 treated barley supplements were associated with improvements in silage intake and milk production. As compared with corresponding control diets containing untreated barley, increases in silage intake ranged from 0 to 0·16 of the control value, whilst associated increases in the yields of milk, milk fat, milk protein and lactose were 0·077–0·089, 0·016–0·026, 0·092–0·118 and 0·080–0·092 of the control value. These responses are discussed in relation to the increases in silage intake and milk production observed with fishmeal supplementation of the diet in Experiment 2 and inclusion of sodium bicarbonate in Experiment 3.     

Performance of white clover/perennial ryegrass mixtures under cutting

Clover persistence in mixtures of two varieties of perennial ryegrass (Lolium perenne) with contrasting growth habits and three white clover (Trifolium repens) varieties differing in leaf sizes was evaluated at two cutting frequencies. An experiment was sown in 1991 on a clay soil. The plots received no nitrogen fertilizer. In 1992, 1993 and 1994, mixtures containing the large-leaved clover cv. Alice yielded significantly more herbage dry matter (DM) and had a higher clover content than mixtures containing cvs Gwenda and Retor. Companion grass variety did not consistently affect yield or botanical composition. Cutting at 2 t DM ha^?1 resulted in slightly higher total annual yields than cutting at 1.2 t DM ha^?1, but did not affect clover content. In 1992 the mixtures yielded, depending on cutting frequency and variety, 10·6–14·6 t DM ha^?1 and 446–599 kg ha^?1 N, whereas grass monocultures yielded only 1·2–2·0 t DM ha^?1 and 25–46 kg ha^?1 N. From 1992 to 1994 the annual mean total herbage yield of DM in the mixtures declined from 12·2 to 10·5 to 8·7 t ha^?1, the white clover yield declined from 8·7 to 6·5 to 4·1 t ha^?1 and the average clover content during the growing season declined from 71% to 61% to 46%, whereas the grass yield increased from 3·4 to 4·0 to 4·5 t ha^?1. The N yield decreased from 507 to 406 to 265 kg N ha^?1 and the apparent N fixation from 470 to 380 to 238 kg N ha^?1. Nitrate leaching losses during the winters of 1992–93 and 1994–95 were highest under mixtures with cv. Alice, but did not exceed 10 kg N ha^?1. The in vitro digestible organic matter (IVDOM) was generally higher in clover than in grass, particularly in the summer months. No differences in IVDOM were found among clover or grass varieties. The experiment will be continued to study clover persistence and the mechanisms that affect the grass/clover balance.     

Herbage yield, tiller number and root system activity after defoliation of prairie grass (Bromus catharticus Vahl)

The effects of defoliation upon root and shoot systems of prairie grass (Bromus catharticus Vahl) were examined in both field and pot studies. The varieties used were 78–32 (HY), a high-yielding variety; 79–42 (LY), a low-yielding variety; and the commercial variety Grasslands Matua. In the field, the presence of roots in early and late spring was estimated by measuring uptake of [³²P]phosphate by roots; herbage yields and tiller numbers were recorded. In a pot study, root and shoot dry-matter (DM) yields were analysed. In the field, roots were detected to a depth of 1·2 m. After defoliation to a height of 0·1 m, root presence decreased more than 50% at depths of 0·6 m for LY and 1·0 m for Matua in early spring and at several depths for each variety in late spring. After a second defoliation, the apparent growth rate of shoots decreased by 35% in relation to the first regrowth period. In pots, shoot DM and root DM of control plants (undefoliated) had the following allometric relationship of the form: In (shoot DM) = 0·61 + 1·14 ln (root DM) (r²= 0·81). After defoliation, compared with undefoliated controls, the relative growth rate of shoots and total herbage yields were higher, but root and stubble DM were lower in all three varieties. Pooled root DM means were 10·3 and 6·8 g plant^?1 and pooled stubble DM means were 12·7 and 7·6 g plant^?1 for control and defoliated plants respectively. HY produced heavier tillers than LY, pooled means being 0·94 and 0·53 g DM tiller^?1 (field study) and 3·44 and 2·05 g DM tiller^?1 (pot study) for HY and LY respectively. HY had 5–6 green leaves per tiller, whereas LY had 3–4. Developed green leaves were heavier in HY (58 g m^?2) than in LY (48 g m^?2). It is suggested that differences in both leaf parameters may be related to higher herbage yields for HY than LY.