摘要:

AbstractThe effect of cyanide concentration and plant morphology on the relative acceptability to sheep of fifteen cultivars ofTrifolium repensand one cultivar one cultivar ofTrifolium ambiguumwere assessed in a field trial at Armidale, Australia (30°S). Preference was shown for the taller, larger leaved cultivars of white clover such as Lucky. Regal, Haifa, Aran, Olwen, and for Monaro Caucasian clover, when differences in leaf size and height were most accentuated. Dry matter consumption was a poor indicator of preference. Acceptability measures were not well‐correlated with HCNp. Cyanide contents increased from January to April, but were considerably lower in July and November. Aran and Olwen had consistently the highest HCNp while Lucky, Regal and Monaro had the lowest HCNp. Sulphur contents were always high (>2%) and varied only slightly between cultivars. Sheep preferred clover cultivars that were easiest lo harvest; these were large leaved, tall types. However, once the obvious differences in ease of harvesting were removed, sheep grazed opportunistically. Since HCNp had no effect on acceptability, breeders should aim for cultivars with moderate to low HCNp to retain pest protection but minimize goitrogenic potential. Caucasian clover exhibited a different growth pattern to white clover but its acceptability was simil

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02287.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of blending small‐ and medium‐leaved white clovers together in a mixture of varieties was examined under continuous sheep stocking over a period of three years. Four varieties were used, S184 and Gwenda, small‐leaved varieties suitable for intensive sheep grazing, together with medium leaved varieties Menna and Donna, which are mainly used in general purpose seed mixtures for medium term leys. The small‐leaved varieties were blended with Menna or Donna, sown with a commercial grass mixture and managed as near as possible to farm practice. Although the leaf size of Gwenda is only slightly greater than that of S184, blends based on these two small‐leaved varieties behaved differently. In spring of the first harvest year the yield of Gwenda and of the clover in mixtures containing Gwenda was 27% greater than the yield of the same mixtures which contained S184. As the season progressed this difference decreased. In terms of total annual yields and saving in fertilizer N, the benefits of including white clover in a seed mixture were more pronounced when Menna was mixed with S184 and Gwenda, rather than when Donna was used, although both varieties are in the medium‐leaf category. It was concluded that the slower establishment and the lower clover yield of S184, when compared with larger leaved varieties, can be overcome by blending with a variety that is slightly larger in leaf size, such as Menna, although the choice of variety may depend on sward management and its persistency un

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02288.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe object of this study was to determine the importance of frequency and height of defoliation on regrowth potential ofLolium perenne.Defoliation interval was based on stage of the regrowth cycle, as indicated by leaves per tiller.Simulated swards ofLolium perennecv Yatsyn were grown as individual plants in a glasshouse kept at a day/night temperature of 25°C/15°C.Treatments imposed were defoliation at 2, 5 or 12 cm residual height, and low and high water soluble carbohydrate (WSC) level obtained by varying defoliation interval, i.e. defoliating at the 1‐leaf or 3‐leaf stage of the regrowth cycle. Regrowth after frequent short defoliations was only 65% of the less frequently defoliated plants taken over the full regrowth cycle. This was associated with a lower stubble WSC content (2·15 vs 17·5% in stubble) and a twenty‐seven‐fold difference in the amount of WSC in the stubble per plant. This difference in total WSC was a combined effect of more and heavier tillers and higher WSC content in stubble of plants defoliated less frequently at the end of the regrowth cycle. The regrowth of plants with WSC levels depleted by frequent defoliation when defoliated at 2 cm was significantly below that of those defoliated at 5 and 12 cm.The results indicate the desirability of defoliating plants at the 3‐leaf stage of the regrowth cycle. This not only allows the full regrowth potential to be expressed in that growth cycle, but also in the next cycle, by allowing the replenishment of WSC reserves and optimizing tiller status. The potential to regrow appears then to be based more on the total amount of WSC than the proportion of W

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02289.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of forage matting on rate of grass drying and silage fermentation, digestibility, and intake were examined using perennial ryegrass swards. Treatments compared were: forage mats, where grass was processed through a laboratory scale macerator prior to matting and wilting to 228 g dry matter (DM) kg−1(FM treatment); unconditioned grass which was direct ensiled at 163 g DM kg−1(DE treatment); unconditioned grass which was wilted for the same period as FM to 213 g DM kg−1(UC treatment); unconditioned grass which was wilted to 234 g DM kg−1(UC25, treatment). All forages were dried on black plastic sheeting. For each treatment a total of approximately 80 kg grass DM was ensiled in seven 290 I plastic bins for 136 d prior to feeding to wether sheep. A further total of 14 kg grass DM from each treatment was ensiled in twenty‐one plastic pipes (152 mm diameter, 762 mm long) to give a total of 84 pipes. Rate of silage fermentation was determined by destructively sampling pipes following 1, 2, 4, 6, 13, 20 and 50 d of ensilage. Over the mean wilting period of 6·9 h, grass from the FM treatment dried significantly faster (P<0·001) and required less solar energy per unit of moisture loss than unconditioned grass. The rate of grass drying was highly correlated with solar radiation. The FM treatment did not influence the rate or extent of silage fermentation. The intakes and digestibilities of FM, UC and UC25were not significantly (P<0·05) different from each other but were higher than for the DE treatment (P<0·05 for digestibility and NS for intake). In Northern Ireland it is unlikely that there will be sufficient solar radiation to allow forage mats to be made, wilted to a level to prevent effluent production and harvested within one working day. Further work is required to optimize mat‐making technology for more rapid drying and to determine the effect of adverse weather on nutrient l

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02290.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn 1988 and 1989, swards of grass (G0), while clover (C0) and grass/white clover (GC0) receiving no N fertilizer, and a grass sward supplied with 420 kg N ha−1(G420), were grazed by non‐lactating sheep to maintain a sward surface height of 6 cm. Herbage organic matter (OM) intakes averaged between 1200 and 1700 g OM ewe−1d−1. For treatments G0, C0, GC0 and G420 respectively, the ewes' live weight gain was 102, 112, 100 and 110 g d−1and changes in body condition scores were +0·28, +0·52, +0·36 and +0·44 units season−1. However, the effect of treatment was not significant for either variable. There were similar levels of output of faecal N ewe−1but significantly more urinary N ewe−1was excreted on treatments C0 and G420, where the concentrations of N in herbage laminae were also higher. For example, in 1989, total daily N excreted was 39·7, 64·4, 44·0 and 63·3 g N ewe−1for G0, C0, GC0 and G420 respectively. Taking into account the mean daily stocking rates, which were 19·4, 26·6, 27·2 and 36·5 ewe ha−1, the total faeces and urine returns over the season were 161, 358, 249 and 484 kg N ha−1for each treatment respectively. The herbage OM intakes ewes−1d−1measured in September and October were similar for C0 and G420, and so the intake of herbage OM ha−1d−1was related to stocking rate, i. e. the estimated herbage intake ha−1over the growing season for the white clover monoculture was 73% of that for N‐fertilized grass. Excretal nitrogen returns to the pasture from grazed mono‐cultures of clover were high, and similar to those from a grass sward receiving 420 kg fertilizer N ha−1. Consequently potential losses of N to the en

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02291.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractGrass (220 g DM kg−1was ensiled after adding 106and 108enterobacteria (90%Rahnella aquatilis, 9·9%Hafnia alveiand 0·1%Escherichia colig−1fresh mutter. The silages were exposed to aerobic conditions alter 125 d of storage. In all treatmentsH. alveirapidly superseded the initial high number ofEnterobacter agglomerans(naturally present) andR. aquatilis.The maximum number of enterobacteria was detected about I d after initiation of fermentation. After 4 d of fermentation, when concentrations of undissociated lactic and acetic acids ranged from 52 to 36 mM and 41 to 51 mM respectively, no enterobacteria were detectable. Inoculating the crop with enterobacteria restilted in a temporarily retarded rate of production of lactic and acetic acids and a 50% increase in the concentration of ammonia‐N. The concentration of endotoxin in the silages was 6–7 μg g−1fresh matter. There was no change in the level of endotoxin during ensiling. High numbers of enterobacteria at the beginning of the fermentation improved the aerobic stability of the silages. There was a lag in the decrease in concentrations of acids and delays in the increase in pH, respiration rate and numbers of yeast andBacillusspores, in uninoculated silages the pH increased from 4·1 to 5·0 after 8 d of aerobic storage, whereas in inoculated silages a pH of 5·0 was not reached until after

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02292.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe long‐term influence of sward height from April to July (Phase 1) and from July to early October (Phase 2) on total herbage and white clover production was measured over four years (1988–1991) as herbage accumulation. A subsidiary experiment to determine the influence of leaf area index (LAI) on gross canopy photosynthesis was conducted to aid interpretation of growth from herbage accumulation data. Target sward heights in 0·5 ha plots in two blocks were 5,7 or 9 cm in Phase 1 and 7 or 9 cm in Phase 2, although mean actual heights per phase were slightly higher. Net herbage accumulation (NHA) was measured within mobile exclosure areas over successive two‐week intervals. Gross photosynthesis was measured in circular turves removed from the trial area representing a range of LAIs with an at least reasonable clover content. Despite wide differences in mean sward height and herbage mass, NHA and net clover accumulation for a given phase were not generally affected by treatments. Positive effects of grazing at 5 cm in Phase 1 on NHA and clover accumulation later in the year, and of grazing at 7 cm in Phase 2 on NHA in the following spring were sometimes apparent. Gross canopy photosynthesis (g CO2m−2h−1) at 1500 μE m−2s−1and 18–21°C was linearly related to LAI described by 1·003 + 1·165 LAI over the LAI range 0·7 to 4·5. Total herbage and clover growth, interpreted from NHA by a previously described model, was predicted to be marginally lower in shorter swards. Similarity in NHA and clover accumulation between treatments was considered to be because of lower senescene and decomposition, and a higher proportion of new tissue being assigned to lamina growth, despite lower LAI and gross photosynthesis in the shorter swards. It was concluded that stocking intensity in swards continuously stocked with cattle did not have a strong influence on net total her

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02293.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSuccessful integration of rotational grazing into livestock production systems requires estimates of pasture growth rates for feed budgeting of daily animal intake. By matching livestock nutrient demand with forage availability, over‐feeding of supplements can be minimized, which reduces feed costs and the need lo manage surplus nutrients, A three‐year grazing study was carried out on a Kentucky bluegrass (Poa pratensisL.)‐dominant pasture to estimate the daily quantity of herbage available to cattle in an intensive, rotational grazing system. Herbage production, species composition, and forage quality were determined in each of the six grazing cycles in a year, from April until September. The average length of a grazing cycle was 28·6 d, with 2·7 d for duration of grazing on a paddock. Pre‐grazing and post‐grazing sward heights, measured with a plate meter, were 14 and 7 cm, and the corresponding herbage masses were 1955 and 775 kg DM ha−1respectively. Under adequate soil moisture during 1989, herbage available for daily intake was 53 kg ha−1from April until mid‐ August, declining to approximately 32 kg ha−1d−1by the end of September. Distribution of this herbage was fairly uniform until the end of August. However, a dry summer in 1991 reduced herbage availability to 15 kg ha−1d−1. Bluegrass and white clover (Trifolium repensL.) formed 70% of the herbage yield during the period April–June. Later in the season, dead matter and other species increased, reducing the contribution of bluegrass and clover to approximately 60% of total dry matter. While these pastures have the potential to provide significant amounts of forage for 5–6 months in a year, additional on‐farm forage reserves are needed

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02294.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA total of 2225 samples of herbage, typical of that taken for first‐cut silage on commercial farms in England and Wales, was taken between 1988 and 1991. Samples were analysed for dry matter (DM), water soluble carbohydrate (WSC), crude protein (CP) and metabolizable energy calculated from modified acid detergent fibre. The results were used to investigate the effect of weather conditions upon herbage quality for ensilage. In general, in areas of high rainfall, i.e. western areas, herbage DM and WSC were significantly lower than in eastern areas, whilst the reverse situation occurred with CP. Italian ryegrass (IRG) had a significantly higher WSC and lower CP than other grasses, whilst samples from permanent pasture (PP) had significantly lower DM and WSC, and significantly higher CP than other grasses. It was calculated that to produce a WSC concentration in the fresh grass of 37 g kg−1, to produce well‐fermented silage without additive use, IRG grown in the east would require a DM of 160 g kg−1, In contrast PP grown in the west would require a DM content of 25

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02295.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractEstimates of leaf and internode weight, leaf appearance rate and shoot number are not appropriate for non‐destructive determinations of lucerne (Medicago sativa) growth rates as they are too variable. In an experiment involving four cultivars of lucerne harvested on two dates, a good relationship was found between linear measurements and the dry weight of shoots. An equation of the form W1/3= a.(dl*d2*length)1/3, where W = dry weight; dl, d2 = two diameters of the basal end of the shoot; length = maximum length of the shoot; and a = constant, gave a good fit to the data. The value of a varied between cultivars and sampling dates, and in the proportion of shoot harvested. The product of estimated shoot weight and shoot number can be used to give an estimate of plot yiel

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02296.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY