摘要:

AbstractIn two experiments, ewes in weeks 1–20 of lactation received either pasture only or pasture plusad libitumconserved forage. Herbage height was maintained at 3·3–3·4 cm on both treatments by manipulation of stocking rate in the 24 plots (twelve per treatment) used for the experiment with additional ewes and lambs. In experiment 1, silage, which was of lower metabolizable energy (ME) and crude protein (CP) contents than the grazed herbage, was consumed at an average of 375 g dry matter (DM) ewe−1d−1. In experiment 2 a strawmix, containing (g kg−1freshweight) 480 g barley straw, 300 g concentrate and 220 g molasses, again with a lower ME and CP content than the grazed herbage, was consumed at an average of 165 g DM ewe−1d−1. In both experiments ewes not receiving forage lost weight whereas those with forage gained weight and tended to have increased body condition scores. Offering silage or strawmix did not affect lamb liveweight gain o

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02225.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn two experiments weaned entire ram lambs were offered either pasture alone or pasture plusad libitumconserved forage for 7–12 weeks during the finishing period. Herbage height was maintained at 3·2 cm on both treatments by manipulation of stocking rate in the twenty‐four plots (twelve per treatment) used for the experiment. In experiment 1 silage, which was of lower metabolizable energy (ME) and crude protein (CP) content than the grazed herbage, was consumed at an average of 194 g DM head−1d−1, providing approximately 40% of total DM intake requirements. In experiment 2 a strawmix, containing (g k g−1freshweight) 450 g barley straw, 300 g concentrate and 250 g molasses and again with a lower ME and CP content than the grazed herbage, was consumed at an average of 57 g DM head−1d−1, providing approximately 11% of total DM intake requirements. In both experiments stocking rate was increased by 20–25% by providing forage, but lamb growth rate

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02226.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe growth of a timothy sward, a timothy/white clover mixture and a multi‐grass/white clover mixture were compared and related to climatic factors at two sites of different altitudes.Temperature and radiation had a greater effect on sward growth than did species composition or management. If the reproductive and vegetative growth periods were studied separately, then more than 90% of the variation in yield could be explained by temperature and radiation. During spring reproductive growth, yields per unit increment of temperature or radiation were 2–3 times higher than during summer vegetative growth. Spring growth was affected more by temperature than by radiation and the lower yields at the higher altitude were also related to lower temperatu

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02227.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractEight field‐plot experiments were carried out on established grassland swards between 1984 and 1988 to examine the effects of date and rate of application of calcium ammonium nitrate (CAN) on herbage dry matter (DM) yield and apparent efficiency of nitrogen (N) use at first‐cut silage.CAN application significantly increased (P100 kg ha−1should be questioned where there are likely to be appreciable quantities of available N derived from non

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02228.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFive pasture treatments: (1) controlled grazing, (2) controlled grazing + lime, (3) controlled grazing + lime + phosphate, (4) controlled grazing + lime + phosphate + oversown white clover and (5) controlled grazing + lime + phosphate + oversown white clover + oversown perennial ryegrass were applied to three semi‐natural hill grassland communities. The communities were those dominated byAgrostis/Festuca, MoliniaandNardus.The proportion ofNardusat theNardus‐dominant site was substantially reduced by herbicide before treatments were applied. All treatments were grazed simultaneously by mature wether sheep on three occasions each year. There were two grazing periods each of 4 weeks duration between mid‐May and mid‐August with a further grazing period of 3 weeks starting mid‐October. During each grazing period stock numbers were set so that a residual herbage mass of 560 kg DM ha−1remained at the end of the grazing period. Measurements of net herbage accumulation (NHA) were made annually over a period of 13 years at each site. The green:dead ratio of grasses, species composition of the pasture and the pH of the soil were measured at intervals during the experiment.Estimates of mean annual NHA ranged from 3860 kg DM ha−1for treatment 1 (controlled grazing) to 5170 kg DM ha−1for treatment 5 (oversown white clover and perennial ryegrass). The application of lime and phosphate increased annual NHA by 300–350 kg DM ha−1with a further increase of around 400 kg DM ha−1when white clover was sown. Increases in NHA between year 1 and year 13 ranged from 30% for treatment 1 to around 55% for treatment 5. Although there was no difference in the mean NHA between sites, the herbage from theAgrostis/Festucasite contained a higher proportion of green grass and white clover than that from the other sites. The highest levels of green grass and white clover were found on the oversown treatments at each site.The grazing pressure exerted produced relatively little change in the botanical composition at theAgrostis/Festucasite. At theMolinia‐dominant site theMoliniawas largely replaced byNardusduring the first 6 years andNardusalso increased in cover at theNardussite. Application of lime and phosphate generally increased the proportion ofPoa pratensis, Festuca rubraandAgrotis tenuisbut did not halt the spread ofNardusat theMoliniaandNardussites. White clover and perennial ryegrass were successfully introduced by oversowing and proportions remained high throughout the 13 years. The cover by bryophyte spp. increased at all sites with the greatest increases occurring in each case on the less comprehensive pasture treatments.These results suggest that onAgrostis/Festuca‐dominant pastures herbage biomass production can be increased with relatively low‐cost pasture treatments while maintaining Species diversity. However,NardusandMoliniadominant pastures are likely to require more comprehensive pasture treatments involving sown grasses and white clover to provide herbage of acceptable quality and avoid an increase inNardusand bryophytes in the sward. With a regime of episodic summer grazing and the addition of fertilizers oversown pastures can be maintaine

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02229.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFive pasture treatments were applied to three semi‐natural hill grassland communities. The pasture treatments were: (1) controlled grazing, (2) controlled grazing + lime, (3) controlled grazing + lime + phosphate, (4) controlled grazing + lime + phosphate + oversown white clover and (5) controlled grazing + lime + phosphate + oversown white clover + oversown perennial ryegrass. The communities were dominated byAgrostis/Festuca(site 1),Molinia(site 2) andNardus(site 3). TheNardusat site 3 was substantially reduced by herbicide before treatments were applied. All treatments were grazed simultaneously by mature wether sheep on three occasions each year to a residual herbage mass of 560 kg DM ha−1. There were two grazing periods, each of 4 weeks duration, beginning in mid‐May and mid‐July respectively and a further grazing period of 3 weeks duration beginning in mid‐October. The number of sheep grazing days and liveweight gain of sheep were recorded during each grazing period for 13 years at each site. Organic matter intake (OMI) and digestibility (OMD) of ingested herbage were measured in years 2, 5 and 13.Mean daily OMI per head ranged from 1290 g for treatment 1 to over 1400 g for treatments 4 and 5. OMI values were higher for theAgrostis/Festucasite (mean OMI 1450 g) than for theMoliniaandNardussites (1310 g and 1370 g respectively) largely owing to differences in the values for treatments 1, 2 and 3. OMI values for each treatment decreased by around 300 g between May and October.Mean OMD values from treatments 1, 2 and 3 were higher for theAgrostis/Festucasite (0·66) than for theMoliniaandNardussites (0·63 and 0·64 respectively). The OMD values for treatments 1, 2 and 3 at theMoliniaandNardussites declined by between 0·05 and 0·02 between years 2 and 13 and also showed the greatest decrease between May and October (0·08). OMD values for treatments 4 and 5 (0·67 and 0·69 respectively) were higher than for treatments 1, 2 and 3 at all sites and levels were maintained over 13 years.Individual liveweight gains of sheep increased from treatment 1 (−18 g d−1) to treatment 5 (82 g d−1), but they decreased over time on all treatments.TheAgrostis/Festucasite gave 17% more annual sheep grazing days than theMoliniasite and 33% more than theNardussite. The mean number of annual sheep grazing days for each treatment ranged from 2250 for treatment 1 to 3640 for treatment 5. Annual sheep grazing days increased over 13 years by between 35 and 45% for treatment 1 and 55 and 70% for treatment 5.The results are described in relation to the changes in pasture composition a

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02230.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractLamina wettability, assessed using water droplet contact‐angle and surface water‐retention measurements on excised leaves, was examined inLolium perennecv. Melle, cv. Condesa and an indigenous population from an old pasture,Holcus lanatus, Poa trivialisandAgrostis stolonifera.The species fell into two significantly distinct categories, those with unwettable laminae, namelyH. lanatusandA. stolonifera, and those with highly wettable laminae,P. trivialisand the threeL. perennepopulations. There was no significant difference between theL. perennepopulations, which had the most wettable laminae overall. The possible implication of these differences in lamina wettability on animal production is discus

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02231.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractDuring 1984 and 1985, trials at sixteen sites throughout Wales measured the yield response in upland swards from applying 40 and 80 kg N ha−1at three dates, 20 August, 4 September and 18 September. All sites were between 230 m and 345 m above sea level. Grass yields were measured by cutting plots during October and November.Nitrogen increased the herbage dry‐matter (DM) yield at all sites in both years. The yield response per kg N applied varied between sites. Mean yield response for the two years declined from 16·2 kg DM kg N−1with 40 kg N ha−1applied on 20 August to 8·9 kg DM kg N−1with 80 kg N ha−1applied on 18 September. In general there was a decline in response to N with increased rate and delay in time of application. The results indicate that responses above an optimum of 9 kg DM kg N−1can be obtained well into September. A general rule that 1 kg N can be economically applied per 4 summed day degrees air temperature>6 °C remaining in the autumn up to 30 November is suggested.Delay in application and increasing N rate increased crude protein in the herbage but had only small effects on modified acid detergent (MAD) fibre and sugar. Generally, grass quality was good. Sward density assessed during the spring after nitrogen had been applied appeared to have been unaffected b

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02232.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractMeasurements of undisturbed sward surface height (sward height) were made using the HFRO and sonic sward sticks at 20 cm intervals along 100 m transects laid across paddocks grazed by either sheep, cattle or goats. Measurements of sward height were also made at 5 cm intervals along 10 m transects laid across the same paddocks using the HFRO sward stick alone. The variance of the measurements from each transect was partitioned across the range of spatial scales of roughness present using spectral analysis. The variance of the sward surface height appeared to be dominated by variation with spatial scales of less than 1 to 2 m. The variances of measurements made with the two sward sticks were similar despite the greater sampling area of the sonic sward stick. This was due to the presence of variation at spatial scales much larger than the sampling area of either instrument and to a greater contribution from non‐spatially related sources to the variance of the sonic sward stick measurements. The use of weighted disc meters for obtaining the mean height of continuously grazed sward deserves re‐examination, while automation of the sonic sward stick may be worthwhile if the spatial distribution of herbage is to be descri

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02233.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe components of a simulation model of mesophilic and thermophilic yeast and mould growth in aerobically deteriorating silage are presented. The purpose of the model is to examine the relative roles of yeasts and moulds in deterioration and the factors affecting aerobic stability. Information for the model was based on literature studies. Growth of the fungi was assumed to be affected by temperature, pH, water activity, and lactic and acetic acid concentrations. The substrates utilized in the model, in order of preference, were water‐soluble carbohydrates, ethanol, lactic acid and acetic acid. Gas movement and heat transfer were not considered. Consequently, oxygen and carbon dioxide concentrations were assumed to be those for open air, and the heat of respiration retained in the silage was set as a constant percentage of that released by fungal growth.Based on the relationships developed for the model, pH affects yeast growth minimally and does not affect mould growth at all. Water activity over the range in silage affects yeast growth more than mould growth, but affects neither one strongly. Undissociated lactic and acetic acids decrease growth rate and may be important factors in silage stability. Compared with moulds, yeast growth rates are less affected by suboptimum temperatures but are more sensitive to temperatures in excess of the optimum.A succeeding study compares the model with published aerobic deterioration studies and examines the predicted succession of microbial groups and the variation in silage stability as affected by silage parameters, initial temperature, and initial microbial population

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1991.tb02234.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY