摘要:

AbstractMicroswards of white clover and perennial ryegrass were subjected to one of four treatments: weekly cutting to 3·5 cm, weekly cutting incorporating a period of no cutting for 6 weeks starting 27 April (early rest), weekly cutting incorporating a period of no cutting for 6 weeks starting 8 June (late rest), or cutting every 3 weeks. Two sward types were used: a mixture of white clover cv. Milkanova with perennial ryegrass cv. Melle, and white clover cv. Kent with perennial ryegrass cv. Melle. Growth measurements (leaf appearance, branching/tillering and stolon internode length) were confined to the first three treatments with records collected during contiguous 21‐d measurement periods. Vertical height increments of clover and grass and red:far‐red light ratios at the sward bases were also recorded at frequent intervals. At the end of the experiment population densities and unit weights were recorded for all treatments.Significant treatment effects on the rate processes were largely confined to the 21‐d period immediately after weekly cutting of rested swards had resumed. On previously rested compared with weekly cut swards, clover leaf appearance rates were increased by 40% and branching rates by 164%. During the same period, grass leaf appearance rates were reduced by 50% and net tillering changed from positive to negative values. Though the rate responses were transient, effects were still apparent at harvest in September, when population density and content (proportion by population density and weight) of clover were significantly higher in the late rest treatment. The variety Kent showed a consistent, though usually nonsignificant, higher leaf appearance and branching rate compared with Milkanova, and in September was characterized by a higher population (7400 m−2compared to 3200 m−2) of smaller units (27 compared to 46 mg/apical meristem) than Milkanova.The results are discussed in relation to defoliation effects and the role of light quantity and quality as they influence the component growth processes. Attention is drawn to the importance of canopy structure and the climatic and/or phenological differences in the relative seasonal behaviour of clover and grass, together with varietal variation within species in influencing responses to management man

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02203.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractPerennial ryegrass pastures were maintained at sward surface heights (SSH) of 30, 60, 90 and 120 mm by continuous variable stocking using lactating ewes and their twin lambs in spring and non‐lactating (dry) ewes in autumn.The effects of SSH on ingestive behaviour, herbage intake, animal performance and sward structure and production were measured in spring, and again in autumn, when an additional SSH of 20 mm was also established.In spring, differences in sward structure were quickly established with mean tiller numbers of 41 000, 30 000, 21 000 and 19 000 m−2and leaf area indices (LAI) of 1·5, 2·2, 3·3 and 4·1 at SSH of 30 to 120, respectively. By autumn the mean tiller numbers had fallen to 26 000, 26 000, 23 000, 18 000 and 13 000 m−2and LAI to 1·0, 1·1, 1·5. 2·0 and 1·5 for treatments 20 to 120.The mean stocking rates for the ewes in spring were 27, 20, 22, and 19 ewes ha−1and growth rates of their lambs were 208, 275, 250 and 263 g d−1for treatments 30 to 120. In autumn the stocking rates maintained for dry ewes were 22, 15, 9, 4 and 0 for treatments 20 to 120.In spring, both grazing times (GT) and prehension biting rate (BR) were negatively correlated with SSH, while bite mass (BM) was positively correlated with SSH. However, mean daily intakes of organic matter (OM), were reduced only for animals grazing the 30 mm sward.In autumn, intake rate was lower only for the animals grazing the 20mm sward and GT and BR were not significantly affected by SSH.Relationships between SSH and, components of ingestive behaviour and intake, are presented and the control mechanisms involved are discussed. The results showed that the optimum sward surface height for continuously stocked swards, grazed by sheep, Was betwe

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02204.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractSeventeen grass or oats swards, displaying a wide and largely independent variation in surface height and bulk density, were produced using different seed rates at sowing and different cutting or grazing pre‐treatments. Four sheep confined in cages were allowed to take twenty bites from small patches of each sward, and measurements of bite weight and the physical dimensions of the average bite in the sward (bite depth, area and volume) were related to a range of sward structural characteristics.Mean bite weight per sward ranged from 40 to 330 mg dry matter (DM). It was positively related to surface height (range 6–55 cm), which acted primarily upon bite depth and hence bite volume, and to the bulk density of the grazed stratum (range 0·1–2·0 mg DM cm−3) which influenced bite weight directly. The effects of surface height and grazed stratum bulk density were independent and additive, resulting in a planar response surface.The influence of sward variables on bite area was less clear than on bite depth, but within a given grass species the effect of surface height appeared to be positive and that of the population density of grazed leaves and stems negative. These findings are considered in relation to a theory concerning grazing mechanics.The merits of the grazing cage technique are discussed and suggestions made for fur

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02205.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractHerbage characteristics were monitored over 3 years (1985–1987) in three perennial ryegrass (Lolium perenneL.) varieties as grass/only (200 kg N ha−1) and grass/clover (Trifolium repensL.) (75 kg N ha−1) swards when continuously stocked with sheep. Although mean total annual herbage production was similar from the grass varieties, growth of Aurora, a very early‐flowering variety, was higher than that of Aberystwyth S23 and Meltra (tetraploid) late‐flowering types in spring. Herbage production from grass‐only swards was 15% higher than from grass/clover swards.In vitroorganic matter digestibility (OMD) of Aurora and Meltra was 34 g kg−1and 26 g kg−1higher (P<0·01) than that of S23. Averaged over varieties, the OMD of grass/clover was 25 g kg−1higher (P<0·05) than grass‐only during the post‐weaning period. Individual lamb digestible organic matter intake (DOMI) was 22% higher (P<0·05) on grass/clover than on grass‐only during this period. Water‐soluble carbohydrates content of Aurora was 42% higher (P<0·001) than that of both Meltra and S23.Herbage characteristics were related to lamb performance reported previously. Lamb production was positively correlated with DOMI. However, the magnitude of differences in lamb performance between treatments was much greater than the extent of differences detect

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02206.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFive white clover populations of Swiss origin and three bred varieties were grown in binary mixtures with two perennial ryegrass varieties, Aurora and S23. The seasonal yields of clover and grass plus clover were measured under a cutting regime during the second and third years after establishment. A series of destructive detailed sward measurements was made during the late autumn to spring period preceding each harvest year. In this way changes in the amounts of stolon, leaf plus petiole and numbers of growing points were monitored during the winter.There were large differences in clover yield between populations in both years. These were evident from the first (spring) harvest in each year. Higher‐yielding clovers in spring tended to produce higher annual clover yields. No grass × clover interaction was evident at any harvest. Large differences between clovers were also apparent in the morphological characteristics measured, with the Swiss material generally having greater amounts of stolon, leaf plus petiole and numbers of growing points present in early spring. It is proposed that these factors contribute to the high spring yield in the Swiss populations. Loss of stolon length over each winter was less in the Swiss material, indicating that its good spring growth was not obtained at the expense of winter hardiness. Annual clover yield was found to be significantly positively correlated with the amount of stolon present in spring, exemplifying the importance of stolon survival over the wint

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02207.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFour grass silages were made from perennial ryegrass ensiled after a 1h wilt in 2‐t silos without additive application, with application of formic acid or with one of two enzyme mixtures of hemicellulases and cellulases (enzyme 1 and enzyme 2). Effluent losses were monitored over the ensiling period (130 d).Analyses of the silage showed that formic acid‐treated silage had lower concentrations of lactic acid than the other silages. Both enzyme‐treated silages had lower levels of cellulose, acid detergent fibre (ADF) and neutral‐detergent fibre (NDF) than the untreated and formic acid treated silages. Effluent production was highest with enzyme‐treated silages.The silages were subsequently fed to growing steers equipped with rumen cannulae and T‐piece duodenal cannulae. Apparent whole‐tract digestibilities of organic matter constituents were significantly lower (P<0·05) with both enzyme‐treated silages (untreated; 0·736, formic acid; 0·722, enzyme 1; 0·694, enzyme 2; 0·703). Both untreated and enzyme 2‐treated silages sustained higher nitrogen digestibilities (g g−1intake) (untreated; 0·675, formic acid; 0·636, enzyme 1; 0·630, enzyme 2; 0·662) and N retentions (g d−1) untreated; 16·0, formic acid; 14·0, enzyme 1; 11·6, enzyme 2; 16·6), but none of these differences was significant. When formic acid‐treated silage was offered, there was a greater amount of organic matter apparently digested in the rumen (ADOMR). Non‐ammonia nitrogen and microbial nitrogen flows at the duodenum were similar on all diets. The efficiency of microbial protein synthesis was highest with enzyme 2‐treated silage and lowest with formic acid‐treated silage (untreated, 35·4; formic acid, 25·2; enzyme 1, 30·4; enzyme 2, 39·4),

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02208.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA first cut of timothy, treated with water (untreated), formic acid (FA), cellulase + lactic acid bacteria (CB), cellulase + hemicellulase (CH) or cellulase + hemicellulase + a lignin‐modifying enzyme (CHL), was ensiled in pilot‐scale silos. Silages, except CB, were fed to four male cattle, each equipped with a rumen and duodenal cannula, in a digestibility trial designed as a 4 × 4 Latin square. The animals were fed a diet of 400 g of concentrate and 600 g of silage at a level of 70 g DM kg−1live weight (LW0·75).All enzyme‐treated silages were well‐preserved with a more extensive fermentation than in FA silage. The quality of untreated silage was poorer as indicated by higher pH and ammonia‐N content. The amount of effluent from enzyme‐treated silages ranged from 116 to 127 g kg−1; for FA and untreated silages values were 101 g kg−1and 80 g kg−1, respectively. Total DM losses from enzyme‐treated silages were higher than from FA silage (P<0·05). No significant differences were noticed between silages in the apparent digestibility of organic matter (OM), neutral‐detergent fibre (NDF), acid‐detergent fibre (ADF) or nitrogen (N). The apparent digestibility of cellulose was higher with enzyme‐treated silages than with FA silage (P<0·05). The values for microbial N flow at the duodenum were 80·0, 91·9, 80·7 and 70·5g N d−1, and for the efficiency of rumen microbial N synthesis 38·6, 47·6, 36·9 and 32·5 g N kg−1OM apparently digested in the rumen for untreated, FA, CH and CHL silages, respectively. In the rumen the molar proportion of propionate was higher (P<0·01) and that of butyrate lower (P<0·01) with enzyme‐treated silages when compared with FA silage. The proportion of butyrate was also lower with untreated than with other silages (P<0·01). The rumen residence time of NDF and ADF was longer (P<0·05

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02209.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA series of experiments was undertaken to determine population statistics forin vitroorganic matter digestibility (in vitroOMD) data and to examine the effects of basal diet, donor animal and precollection fasting interval on the activity and specificity of rumen fluid inoculum. The experiments utilized wether sheep, a diverse set of pasture grass and legume feeds prominent in the Australian subtropics and the Tilley and Terryin vitrodigestibility procedure running under the operating pressure of a practicing feeds evaluation laboratory.The standard errors ofin vitroOMD estimates for within and between batch runs were ±0·88 × 10−2and 0·62 × 10−2, respectively. These error terms were used to develop protocols to accept, reject or scale rawin vitroOMD data. Differences between donor animals in the activity of rumen fluid were highly significant. Extending the precollection fasting interval beyond 16 h was associated with a substantial decline in inoculum activity.Anin vitro‐in vivocalibration relationship based on fifteen test feeds and using lucerne (Medicago sativa) as basal diet was described by the linear model y = 1·3 x‐0·195±4·9 × 10−2r= 0·79 (y =in vivoOMD, x =in vitroOMD). Despite large effects of basal diet on both the absolute values and relative ranking of test feeds, neither the RSD norrvalues were improved using alternative diets to Lucerne chaff.The results highlight the need to formally standardize the analytical and biological components of thein vitrodigestibility procedure to safeguard t

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02210.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractProcedures used to determine chemical composition and digestible organic matter in dry matter (DOMD) are slow and expensive. The possibility of using near‐infrared reflectance spectroscopy (NIRS) as an alternative procedure was investigated with annual legumes. Material from cultivars ofMedicago murex, Trifolium balansae, T. resupinatumandT. subterraneumwas harvested soon after plants had matured. Samples were sorted into stem, leaf and burr fractions and analysed chemically and by NIRS. Data were then sorted into two similar sets, one of which was for calibration and the other for validation. Data for each chemical fraction, in samples used for calibration, were regressed sequentially against the corresponding reflectance spectral data, the log of there reciprocal of which was transformed to first or second derivatives. Equations of best fit were then used to predict the composition of samples in the validation set.Standard errors of calibration and validation respectively, expressed as percentages of the mean, were 0·5 and 0·6 for dry matter (DM), 2·0 and 2·6 for organic matter (OM), 4·8 and 4·3 for DOMD, 6·0 and 7·2 for crude protein, 4·1 and 4·4 for acid‐detergent fibre (ADF), 2·5 and 3·1 for neutral‐detergent fibre (NDF) and 8·9 a

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02211.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA chemical hybridizing agent (CHA: WL 84811, azetidine‐carboxylic acid. Shell Chemical) was applied to annual ryegrass (Lolium rigidumGaud. cv. Wimmera) at four levels: 0, 1·6, 2·4 and 3·2 kg active ingredient (a.i.) ha−1, at booting and at anthesis with a view to reducing seed set and increasing the proportion of cell solubles in the senescing and dead plants. The CHA treatments reduced stem elongation by up to 40% and reduced the proportion of pollinated florets progressively according to the concentration of CHA. At 3·2 kg (a.i.) ha−1only 14% of florets were fertilized compared with 86% on the zero (control) treatment.The CHA treatments also resulted in progressive increases in the number of secondary tillers. Since there was no increase in the amount of neutral‐detergent solubles associated with increased CHA application, it was concluded that storage carbohydrates, which might otherwise have been directed towards seed development, were partitioned towards increased tillering. There was no effect, therefore, on the proportion of neutral‐detergent soluble material in senescing an

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02212.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY