摘要:

AbstractTurnover rates of grass laminae and clover leaf tissue were estimated over a range of intervals within three periods each year in the second to fourth years (1983‐85) of a trial involving swards continuously grazed by steers and receiving either 60 kg N ha‐1 in spring (60N) or 360 kg N ha−1throughout the year (360N). Within the 60N swards initial stocking rates at turnout were low (60N LS) at 7‐2 steers ha−1and high (60N HS) at 90 steers ha−1in 1983, and in 1984 and 1985 corresponding rates were 10‐8 and 13‐5 ha−1. The 360N swards were initially stocked at turnout at 96 (360N LS) and 120 (360N HS) steers ha−1. Stocking rates were reduced by 33% in midsummer except for 60N in 1984 and 1985 when they were reduced by 50%.Meaned over 3 years, 360N HS had lower herbage mass than 60N LS. Tiller density in 360N was almost 50% higher than in 60N and clover growing point density was only one quarter that of 60N with the 60N LS having lower clover densities than 60N HS in 1985.Generally, leaf extension rate per tiller was higher in 360N than 60N and, when significant, 60N LS had higher senescence rates per tiller than 360N HS.Rate of increase in new clover lamina tissue per stolon was not affected by treatments, whereas in 1983 LS had higher senescence rates of clover laminae than HS. Petiole growth per stolon was higher in LS than HS in 1983 and 1984, the mean over these years for 360N HS being 77% that of 60N LS. Petiole senescence per stolon was lower in 360N HS than 60N LS only in 1983.When comparing 60N HS and 360N LS (representing similar levels of grazing intensity, having similar herbage mass) the gross growth of leaf material in the former was 75% of the latter, in contrast to 57% for net growth. Clover contributed 18% to the estimated growth of leaves compared to a mean of 7% in herbage mass. Taking inflorescence and pseudostem into account in 1984 and 1985,60N HS had 7% clover in standing herbage and 14% in net growth. Therefore, the contribution of clover to growth is considerably higher than its presence in herbage mass would suggest in continuously grazed swards. It is concluded that low‐N swards, owing to their lower tiller density and slower grass leaf extension rate, will be less efficiently grazed than swards at higher N levels at a given herbage mass, but the presence of clover will partly off

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02162.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe response of continuously stocked spring‐calving beef cows and calves to a range of sward surface heights was determined. Mean sward heights of 4‐5, 60, 70, 91 and 11‐0 cm (treatments A to E respectively) were maintained from mid‐May to mid‐August (Period 1) and treatments C, D and E continued until the end of September (Period 2), during which time mean sward heights were 5‐4, 7‐8 and 9‐2 cm respectively. Hereford x Friesian or White Shorthorn‐x Galloway cows with their Charolais‐cross calves were used, with 9, 6, 6, 5 and 9 cows on treatments A to E respectively. During Period 1 the mean live weight gains of cows were‐0‐52,‐005,0‐32,075 and 0 40 (s.e.d. 0167) kg d−1on treatments A to E respectively and during Period 2.‐0‐31, 057 and 059 (s.e.d. 0153) kg d−1for treatments C, D and E respectively with maximum cow liveweight gain at sward heights of 8 to 10 cm. Calf liveweight gains were 0 88,091, 098, 1 04 and 1‐06 (s.e.d. 0068) kg d−1in Period 1 for treatments A to E respectively and 098, 1‐22 and 1 35 (s.e.d. 0067) kg d−1in Period 2 for treatments C, D and E. The percentage of area infrequently grazed was generally less than 20% on treatments A to D, but on treatment E it was more than 40% for 6 weeks after turnout and thereafter remained between 20 and 40%. Maximum calf liveweight gain per hectare was achieved on the shorter swards, but maximum total liveweight gain of cows and calves per hectare occurred on treatment D. It is concluded that for maximum cow and calf performance on continuously stocked pastures, sward height should be maintained at no more than 8 cm in spring and early summer and then increase

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02163.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe productivity of fourteen grasses was measured under a silage cutting regime of four harvests per year for 3 years (1984‐86) with an annual fertilizer N rate of 360 kg ha−1, applied at 120, 100, 80 and 60 kg ha−1for successive harvests. The grasses were: red fescue(Festuca rubra)cvs Reptans, Dawson and Ruby, perennial ryegrass(Lolium perenne)cvs Perma and Sprinter, Yorkshire Fog(Holcus lanatus)commercial types I and II, smooth meadow‐grass(Poa pratensis)cvs Parade and Arena, creeping bentgrass{Agrostis stolonifera)cv. Penncross, crested dogstail{Cynosurus cristatus)cv. Southlands and rough meadow‐grass(Poa trivialis)cvs Dasas, Omega Øtofte and Sabre.Red fescue gave the highest dry‐matter (DM) production over the 3 years but because of low organic matter digestibility (OMD), its production of digestible organic matter (DOM) was lower than that of perennial ryegrass. Rough meadow‐grass was relatively low yielding in the first year and did not persist thereafter. Three‐year mean DM production ranged from 9‐22 kg ha”’(crested dogstail) to 14‐37 kg ha‐1 (red fescue cv. Reptans), while mean annual OMD values ranged from 0‐660 (smooth meadow grass cv. Arena) to 0766 (ryegrass cv. Sprinter). The mineral composition (P, K, Ca and Mg) differed among species; creeping bentgrass, crested dogstail, perennial ryegrass and Yorkshire fog had moderate to high mineral concentrations while smooth meadow‐grass had low concentrations. Mean two‐year (1985‐86) mineral composition (g kgDM−1) ranged from 3‐1 to 40 (P), 234 to 31‐0 (K), 3‐8 to 6‐0 (Ca) and 1‐6 to 2‐6 (Mg),It was concluded that while red fescue and Yorkshire fog showed considerable potential for silage DM production, there is scope for breeding red fescue cultivars with improved digestibility and more winterhardy Yorkshire fog; characterization

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02164.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of rate and pattern of fertilizer S application on herbage production from Perennial ryegrass‐dominant swards at six potentially S‐deficient sites in south‐west Scotland were measured under a silage cutting regime (3 cuts year‐1) with high fertilizer N application (300 kg ha−1year‐1). Fertilizer S (as gypsum) was applied at annual rates from 0 to 48 kg ha−1as single spring applications before the first cut or split before each of the three cuts. The residual effect of S in the year following its application was assessed at one site.Applied S increased total DM production at four of the six sites. These increases were restricted to the second and/or third cuts and were generally in the range 10‐30% greater than where no S was applied. Timing of S application was not important in influencing annual DM yield. The residual effect of gypsum in the year following application was small.The supply of available soil S is limiting herbage production in certain areas and soil types of south‐west Scotland. Areas of S deficiency are likely to increase in the future and need to be identified more precisely than th

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02165.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA deterministic model that simulates forage dynamics is described and validation results presented. The model simulates different species of grasses and forbs for a production year and provides the necessary input for a diet selection model. The model does not simulate growth, but does simulate the accumulation of live leaf and stem, the senescence of live biomass, and its transfer to dead mass using growth rates for leaf and stem of each species, which are specified for the model. Using such an approach specific types of years can be simulated. Plant components in the model include live leaf and stem, dead leaf and stem, and old dead leaf and stem which were produced during the previous growing season. These plant components were chosen because of their importance in the diet selection process and their differences in forage quality. Plant species which the model was validated against wereCynodon dactylon, Avena sativa. Schizachyrium scopariumand Paspalum plicatulum. Validation results indicated that with adjustment to input growth rates, live biomass could be adequately simulated. Deviations between measured and simulated dead components were observed forS. scopariumandP. plicatulum.High values observed for dead stem early in the trial resulted from lack of separation of dead and old dead stem material in the field sampling. Variations in dead forage throughout the season were caused by unexplained sources of variation. This indicated a need for field research to better quantify the dynamics of dead biomass. The model meets its goal of simulating biomass dynamics and forage quality of plant parts and it provides a suitable forage base to interface with diet selection and animal simulation models.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02166.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTwelve tethered Angus cows(Bos taurus)weighing 471 ± 18 kg were used in a balanced changeover design to estimate the direct (D), residual (R), and permanent (P) effects of 1,2, and 3 h fasts following 2 h grazing sessions on the ingestive behaviour of cattle grazing swards of endophyte‐(Acremonium coenophialumMorgan‐Jones and Gams)‐free tall fescue(Festuca arundinaceaSchreb. cv Kentucky 31) (Exp I) and lucerne(Medicago sativaL. cv Arc) (Exp II). Herbage dry‐matter (DM) mass (>5 cm) and individual herbage DM allowances were 1‐16 t ha‐1 and 50 kg per hour in Exp I and 1‐861 ha‐1 and 78 kg per hour in Exp II, respectively. In Exp I, P effects of fasting followed trends of R effects since the D effects were small. Mean DM intake rates (P) were 2‐2., 1‐8, and 1‐3 kg h‐1 for cows given 1, 2, and 3 h fasts, respectively. Mean intakes (DM) per bite (P) were 082, 071, and 045 g bite‐1 for cows assigned 1, 2, and 3 h fasts, respectively. Rates of biting were not affected by fasting and averaged 45 bites min”’. In Exp II, P effects followed trends in D effects since R effects were small.Mean DM intake rates (P) were 20, 22, and 3‐0 kg for cows subjected to 1,2, and 3 h of fast, respectively. Rates of biting (P) were 24, 27, and 32 bites min‐1 for cows after 1, 2, and 3 h fasts, respectively. DM intakes per bite (P) were not affected by fasts and averaged 1‐46 g bite‐1. The behavioural responses of cattle to interval between meals were attributed to differences in flow characteristics of ingesta of lucerne and tal

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02167.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractHerbage and faeces samples were retained from an intake and invivodigestibility trial using material harvested at three different stages from five indigenous hill plant communities (those dominated byAgrostis‐Festuca., Nardus stricta., Molinia caerulea., Eriophorum vaginatumandTri‐chophorum caespitosum)and from sown swards of ryegrass or white clover. Samples of the herbages and of their separate components, together with extrusa samples of the same herbages recovered from pen‐fed sheep and cattle oesophageal fistulates, were digestedin vitrousing rumen liquor. Measurements were made also of faecal nitrogen concentration (FN) and of indigestible acid‐detergent fibre (IADF) using the samples from the original trial.The range ofin vitrodisappearance values of the herbages (IVOMD; 0809‐0278) was slightly wider than those ofin vivodigestibility (OMD; 0‐796‐0‐37I). Differences between OMD and IVOMD were greatest at low quality and relationships were best described by two separate linear regressions of OMD on IVOMD for (a) ryegrass, white clover,Agrostis‐FestucaandNardus(RSD; 0 0185) and, (b)Molinia, Tricho‐phorumandEriophorum(RSD; 00246).In vitrodisappearance values of extrusa were higher than those of herbages offered by 00503 and 00156 units for sheep and cattle respectively, partly because of greater levels of ensalivation, especially in the sheep. The relationships of OMD to IADF and to FN were poor, though inclusion of faeces output and fitting parallel lines for communities in the regression of OMD on FN reduced the RSD to 0020. We conclude thatin vitrodigestion of samples of extrusa, using appropriate standards, is the best method of diet digestibility prediction for sheep and cattle grazin

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02168.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAn experiment was carried out to examine the changes in perennial ryegrass (Lolium perenneL.) and white clover (Trifolium repensL.) populations in mixed swards, under different grazing severities over three successive grazing seasons. In year 1, three paddocks were erected on a sward with a low initial content of clover (block 1). Sward heights were measured using a rising‐plate meter, and were maintained at overall mean heights of 3·0, 5·5 or 7·0 cm by variable stocking with 8‐month‐old steers. In year 2, a further three paddocks were erected on an adjacent area with a high initial content of clover (block 2), and were maintained at the same three heights by similar management. Botanical analyses were carded out on samples collected at four times during the season. Maintaining swards at 5·5 or 7·0 cm led to a large proportion of the area being infrequently grazed. Block I paddocks had higher initial tiller densities, which increased as sward height was reduced, while block 2 paddocks, with their lower initial tiller density, showed little effect of sward height on tiller density. Initially, clover stolon growing‐point densities and stolon masses increased more rapidly in the taller swards. Later, however, large losses in the clover populations occurred on all paddocks during long wet winters and there was a general reversal in these trends for stolon growing‐point densities and stolon masses, 3·0>5·5>7·0. By year 3, swa

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02169.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractDuring an experiment in which the height of mixed perennial ryegrass/while clover swards was maintained throughout the season at 3 or 7 cm (S and T, respectively), or were maintained al those heights until 30 June then changed (ST and TS), a limited study was made of the effects on the population densities and masses of the two species. During the earlier part of the season the short swards (S and ST) developed higher tiller and stolon growing point (sgp) densities, but with a reduced mass of ryegrass, principally of the pseudostem fraction, than the tail swards (T and TS). Thiere was little effect of sward height on the mass of clover. Whilst there was a general tendency for tiller and sgp densities to increase during the latter part of the season, tiller density increased greatly where sward height was reduced (TS) and both tiller and sgp densities were reduced where sward height was allowed to increase (ST). Changing sward height, whilst limiting the accumulation of dead grass material (TS), allowed grass leaf and dead masses to increase (ST), and adversely affected the increase in the clover component, principally of stolon material, in both ST and TS.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02170.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA change‐over design was used to establish the ingestive behaviour of twelve adult Angus cows(Bos taurus), live weight (LW) of 475 ± 18 kg, while grazing luceme(Medicago sativaL.) (T1), eating from a swath of freshly cut lucerne (T2), or eating wilted lucerne from a swath (T3). In the first experiment, the herbage dry matter (DM) allowance was 4‐7 kg h−1and in T1the available herbage DM mass (>5 cm) was 2892 kg ha−1. Herbage DM intake was 2.5, 1.6 and 2.0 kg h−1(0.53,0.35 and 0.41 kg (100 kg LW)−1h−1) for T1, T2and T3, respectively. Cattle grazed at 29 bites min−1and ate the swathed lucerne at 6 bites min−1. Herbage DM intake per bite was 1‐2, 4‐9 and 6‐7 (2‐5,104 and 14‐4 mg(kg LW)−1)for T1, T2and T3, respectively. The DM content of the luceme was 227, 263 and 309 g kg−1for the same sequence. In a second experiment with luceme of available herbage DM mass of 5321 kg ha−1and an allowance of 7‐ 3 kg h−1cows grazed lucerne at 2‐9 kg h−1, ate freshly cut material at 21 kg h−1and wilted herbage at 25 kg h−1(0.61, 0.45 and 0.52 kg (100 kg LW)−1h−1), respectively. Leaf accounted for 80%, 68% and 54% of intake for T1, T2and T3, respectively. Swathing lucerne reduced the diet selectivity by forcing cattle to take large bites that required many jaw movements to form a bolus that could be swallowed. It appeared that the mechanics of bolus formation determined in

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb02171.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY