摘要:

AbstractFour cocksfoot varieties were harvested at three different growth stages and offeredad libitumto yearling Clun wethers in three 24‐d feeding trials indoors over a 4‐month period. A further cocksfoot variety conserved in bulk was offered concurrently as a control feed.The concentration of digestible organic matter in the dry matter (DOMD) and voluntary intake were measured in each feeding period. There was no significant change in the measured DOMD values between the different feeding periods. Voluntary intake of digestible organic matter (DOMI) increased over the 4‐month period for all four varieties and for the control feed. The increase in intake was greatest for the most digestible material, i.e. first‐cut harvests. Differences in DOMI were statistically significant between feeding periods for all varieties but the differences could be eliminated by correcting intakes with values from the control feed. It is concluded that comparisons of grass varieties involving intake measurements must either be made in the same feeding period or a control feed included and results corrected according to the control r

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01670.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractRecords of grassland productivity were kept for 2 years on 136 lowland dairy farms and 131 lowland beef farms. The grassland on each farm was classified according to the proportion of sown (preferred) species. The farms were then ranked on this basis and divided into quarters:On dairy farms the lowest quarter had 31% sown species and utilized metabolizable energy (UME) output from grass of 40.8 GJ ha−1, whereas the highest quarter had 70% sown species and UME output of 45.6 GJ ha−1. Dairy farmers in the lowest quarter used least fertilizer N and differences in output were no greater than would be expected from differences in N input. On beef farms the lowest quarter had 28% sown species and UME output of 32.3 GJ ha−1, and the highest quarter had 63% sown species and UME output of 45.9 GJ ha−1On these farms differences in fertilizer N could not completely account for differences in output.It is concluded that on beef farms botanical composition of grassland is a good indicator of its productivity but is not necessarily a prime cause of differences in output. On dairy farms there is little evidence of a direct benefit resulting from a high proportion of sown species. On such farms the need for deliberate manipulation of the botanical composition of grassland by reseeding or chemical means is que

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01671.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA study was conducted to determine the influence of a change in herbage mass on rates of herbage growth (G), senescence (S) and net production of green herbage (NP) in swards ofLolium perenne L., Poa annuaL. andTrifolium repensL. under continuous stocking with sheep. Swards were maintained at either high (1700–1900 kg OM ha−1; H) or low (700–900 kg OM ha−1; L) herbage mass from April to 20 August. From 20 August to 13 September half of the L sward was permitted to grow until a herbage mass similar to that of the H sward was achieved (LH), and at the same time half of the H sward was grazed down until a herbage mass similar to that of the L sward was achieved (HL). The other half of each sward was held at constant mass (LL and HH). Estimates of G, S and NP were obtained for each plant species over a 2‐week period from 17 September to 1 October and estimates of species population densities were also made.The combined species rates of G and S per unit area were highest in treatment LH and lowest in treatment HL, whilst the rates for the LL and HH swards were intermediate. The rate of NP was similar in the LL, HH and LH treatments (34.5, 29.3, 33.6 ± 6.2 kg DM ha−1d−1) but was lower in the HL sward (100 ± 6.2). The effects of alteration of herbage mass on individual tiller or stolon G and S rates were rapid but population density changes were slower.Within the limited conditions of this trial it was not possible to increase NP by manipulation of herbage mass under continuous stocking management but the results indicate that NP can be reduced in the short term if a sward of high herbage mass and low population density

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01672.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA mathematical model of grass production and utilization on a dairy farm is described. Using the model an assessment has been made of the extent to which financial uncertainty arising from year‐to‐year variability in grass yields, coupled with a preference among farmers for minimizing risks, may explain the relatively low stocking rates and observed nitrogen usages on many dairy farms in England and Wales. The degree of risk has been equated with the probability of profits in a particular year being less than those required to cover the consumption needs and short‐term borrowing requirements of the farmer. The results of the analysis indicate that a strategy of minimizing risks may lead to a significantly lower stocking rate than one of maximizing profits. Thus, considerations of risk may lead to stocking rates which are suboptimal from the viewpoint of economic and biological efficiency. However, there is no evidence to suggest that the comparatively low average usage of nitrogen on dairy farms in the UK is determined by risk considerations. On the contrary, increasing nitrogen usage lowers the apparent financial risk at a given stocking

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01673.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractForty hill farms in Northern Ireland were surveyed to obtain information on stocking rates and output and to identify factors affecting output. The mean farm area of 194 ha was composed of 155 ha hill land and 39 ha inbye land with a mean stocking rate of 0–7 cow‐equivalents ha−1.On the average farm most of the grassland (88%) was over 20 years old. The preferred species content of the swards averaged 22% over the whole farm and 42% in cut swards. This latter result may be attributed to the relatively high level of fertilizer N applied to these swards (131 kg ha−1) compared to the mean application rate over the whole farm of only 29 kg N ha−1and 93 kg ha−1applied to the inbye land.Output data calculated as utilized metabolizable energy (UME) per unit area for the whole farm and separately for hill and inbye components showed that although only 21% of the farm area was inbye land almost half the annual total metabolizable energy requirements of stock had to be met by grazing inbye. The capacity of herbage to meet stock energy demands was much lower on the hill with supplementary feed having to be provided over the winter.Calculated output from inbye land was 39 GJ ha−1compared to 7 GJ ha−1from the hill and 15 GJ ha−1from the whole farm. UME output of the whole farm was negatively correlated with farm size (r=−0 55) and positively correlated with stocking rate (r = 0 89), applie

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01674.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTwenty‐one strains of lactic acid bacteria were subjected to a range of tests based on established criteria to ascertain their suitability for use as inoculants for silage. The tests included a monitor of their growth in the presence of representatives of the microflora of forage crops with which they might have to compete for substrate, and their ability to effect rapid acidification and achieve a low pH in conditions which simulate low and high ensiling potential. In addition, their ability to produce acid from sugars and their action against organic acids found in forage crops, together with their tolerance of acid, elevated temperatures and conditions of low moisture availability (e.g. in wilted material) and possible proteolytic and amylolytic activities were examined. None or these cultures satisfied all of these criteria. However, three strains (Streptococcus duransstr. 1024,Lactobacillus acidophilus, str. 2356 andLactobacillus plantarumstr. 6) had a greater potential than the other

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01675.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractForage‐harvested crops of perennial ryegrass (200 g DM kg−1) and red clover (163 g DM kg−1) were inoculated with cultures ofStreptococcus duransstr. 1024,Lactobacillus acidophilussir. 2356 andLactobacillus plantarumstr. 6, and 1:1 mixtures of theStreptococcusand each of the lactobacilli, at rates of 106and 106(g fresh weight)−1and ensiled in laboratory silos for up to 128 d. The possible influence of these bacteria on fermentation was examined in relation to formic acid at rates of application of 0 and 2.3 g(kg fresh weight)−1, None of the cultures or culture mixtures, either at the low or high rate of application, had any notable influence on microbial development, the rate of acidification or promotion of the homolactic fermentation; they tended to exacerbate loss of insoluble nitrogen and deamination. All silages were well‐preserved with no butyric acid being detected, in spite of pH increase during storage. Only formic acid had any consistent and desirable effect on p

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01676.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe herbage dry matter (DM) harvested, N response and herbage quality of monocultures and mixtures ofHolcus lanatus(local ecotype) andLolium perenne(cv. S24) were compared in a field experiment. The species were seeded in the proportions 100:0, 75:25, 50:50, 25:75 and 0: 100; three rates of N were applied (150, 300 and 450 kg ha−1) and five or six cuts were taken in each of four harvest years.H. lanatusestablished poorly in the seeding year and in the first full harvest yearL. perennecontributed 1, 54, 76, 89 and 99% of the total herbage DM harvested from the five sward types (mean of N treatments). Only a small decline in theL. perennecontent of the swards occurred during the experiment.Total amounts of herbage harvested were significantly lower forH. lanatusmonoculture than for the other sward types in three of the four harvest years However,L perennemonoculture yielded significantly more total DM than mixtures withH lanatusin only one of the four harvest years. The five sward types did not differ overall in response to N fertilization. Nitrogen, phosphate and potassium content of the herbage was greatest forH. lanatusmonoculture and decreased with increasing proportions ofL perennepresent in the mixtures.Thus the presence of a high proportion ofH. lanatusin mixture withL. perennecv. S24 h

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01677.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThree diploid—Sabtoron, Violetta and Essex—and three tetraploid—Hungaropoly, Teroba and Red Head—red clover cultivars were sown alone and with each of three companion grasses—timothy (S48), tall fescue (S170) and perennial ryegrass (S24). The productivity and persistence of the red clover cultivars were compared. Results obtained over the first four harvest years were presented in an earlier paper (McBratney, 1981) and this paper presents results from the fifth and sixth (final) harvest years.The low yield obtained in the fifth and sixth year from Essex under each seeding treatment indicated a deterioration in its persistency or vigour or both. In the fifth year the remaining two diploids, Sabtoron and Violetta, were as highly productive and persistent as the three tetraploids but in the sixth year the decrease in productivity was greater in the diploids than in the tetraploids. In the fifth year Teroba, the highest yielder, produced 9 8 t total DM ha−1over all seeding treatments of which 73% was clover DM; in the sixth year Teroba was again highest yielding, producing 9.3 t ha−lwith 67% clover content. Tall fescue was the most consistent companion grass in the mixed swards, in the sixth year contributing 53% grass DM to the total 8 8 t DM harvested ha−1.The trial demonstrates the potential of a number of red clover cultivars grown either pure or with a suitable perennial grass to achieve and maintain a high output of herbage of good quality over a period of 6 years without any application of fertilizer N. The practical agricultural implications of using red clove

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01678.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractYields of grass were measured on three dairy farms in 1981. Farm 1, on free‐draining loamy soil over chalk, produced 10.3 t DM ha−1using 336 kg N ha−1. Farm 2, on poorly‐drained loam over Oxford clay, produced 12.8 t DM ha−1using 354 kg N ha−1. Farm 3, on loam over clay with some free‐draining sandy loam, produced 9.5 t DM ha−1with 169 kg N ha−1. Allowing for differences in soil nitrogen and summer rainfall these yields were quite close to expectations from experimental results, despite considerable poaching damage to some swards.Animal production records were kept and all livestock were weighed every 6 months, so as to calculate the utilized metabolizable energy (UME) output from grassland on each farm. These were 73, 62 and 59 GJ ha−1on farms 1, 2 and 3 respectively.The UME output, expressed as a proportion of the yield of grass (converted to ME), was taken as the ‘efficiency of utilization’ of grass. This was 70% on farm 1,44% on farm 2 and 58% on farm 3. Results are presented separately for the summer and winter 6 months. Utilization by grazing appeared to be markedly reduced under very wet soil conditions. Major losses occurred in the conservation of grass.The results begin to establish a valuable base of dat

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1984.tb01679.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY