摘要:

AbstractThe objectives of this experiment were to study the effects of different grazing managements in spring on herbage intake and performance of summer‐calving dairy cows and to examine the effects of regrowth in early June on herbage intake and cow performance. Four spring‐grazing treatments were applied to predominantly perennial ryegrass swards: Control (C), sward grazed by cows to 6–8 cm sward surface height (SSH); CG16, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to a target SSH of 16cm in early June; CG8, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to 8cm in early June; and SG8, sward grazed by sheep to 2–3 cm SSH in May and allowed to regrow to 8 cm in early June, All swards were continuously stocked by summer‐calving (May and July) primiparous and multiparous cows from 16 June to 7 September, to a target SSH of 8–10cm.Spring treatments bad marked effects on herbage intakes and milk production. Estimated in July bynalkane analysis, the mean herbage intake ± s.e.d. of cows on each treatment were 1·8, 1·4, 1·4 and 3·0 ± 0·31 kg dry matter (DM) 100 kg live weight (LW)−1d−1(P<0·01) for treatments C, CG16, CG8 and SG8 respectively. Measured in August, intakes were 1·8, 20, 2·1 and 2·4 ± O·33kg DM 100kg LW−1d−1respectively. Severe spring grazing led to increased milk yield and reduced milk fat content from summer‐calving cows fed 5·2 kg d−1of a proprietary concentrate. Average milk yields for the eleven experimental cows on each treatment were 24·3, 23·4, 26·2 and 29·0 ± 1·20 kgd−1(P<0·01) for C, CG16, CG8 and SG8, and average milk fat contents were 45·4. 42·4, 43·9 and 40·9 ± 1·02gkg−1(P<0·05) respectively.The results suggest that severe grazing of swards in early season could improve herbage intake and milk yield of summer‐calving cows in mid‐ and late season. The most favourable spring treatment in this respect was severe grazing by sheep. However, this adva

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02326.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractField experiments were carried out in four harvest years to compare the peduncle characteristics and reproductive growth of the small‐leaved white clover (Trifolium repensL.) cv. AberDale, selected for long and strong peduncles, with other varieties bred in the Institute of Grassland and Environmental Research (IGER). The peduncles of cv. AberDale were of larger diameter and had a greater fresh and dry weight than those of other varieties. There were also differences in structure as the peduncles of cv. AberDale had more pronounced ridges and furrows than those of cv, Menna.Inflorescences of cv. AberDale and other varieties were tagged when in full bloom throughout the flowering period in each of the four harvest years. Generally, more inflorescences of cv. AberDale remained intact until harvest, particularly from the early tagging dates. Although there were seasonal differences, at harvest in each of the 4 years, cv. AberDale had more inflorescences and seeds per floret and a greater potential seed yield than the other varieties.The basis of peduncle strength and effect on reproductive growth is discussed, and the implications for improving the seed yield potential of white clover varieties is considere

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02327.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAerobically spoiled silage has often been shown to harbour dangerously high levels ofListeria monocytogenes.This paper investigates the dynamics of aerobic deterioration in a silage bale as it occurs close to a site of damage to the cover. The underlying aim was to enable prediction of the extent of the silage that may become suitable forListeriagrowth during the course of storage. In order to meet these objectives, a model was formulated that represents the microbiology of the deterioration process and the transport of oxygen and heat through the silage. The geometry of the system was exploited to ensure that the model is computationally tractable. The model was used to evaluate the effect of silage pH and puncture size on the risk ofListeriacontamination. Although the hazardous fraction was seen to be relatively insensitive to the initial pH of the silage, it increased rapidly with puncture size. However, a small puncture can result in the ‘loss’ of a considerable fraction of the bale because of the relatively long time scale over which bales are sto

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02328.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThree experiments designed to investigate different facets of autumn management on white clover stolon development are described. The effects of defoliation interval (2, 4, 6 and 8 weeks during 16 weeks from 27 July) were investigated. The shortest interval resulted in the shortest length of stolon material per unit area but cutting interval had no effect on growing point density nor on hardiness of stolon tips evaluated in October, December and January.Chemical grass suppressants were employed to reduce grass biomass during winter in two experiments to evaluate the influence of grass on white clover development. One experiment involved varying grass tiller density by spraying a perennial ryegrass/white clover sward in October with three rates of three chemical suppressants (Clout, Kerb and Checkmate). Although tiller and clover growing point density were inversely related in January, the overall relationship was not strong.Clout at l·5kg a.i. ha−1was sprayed in October on one of two subplots in each of twelve grazed grass/white clover plots that had been maintained at 7 or 9 cm from July to October then grazed to 3–4 cm with sheep. Sward height had no effect on clover population density but the shorter sward had a greater mean node number per secondary stolon branch. By March, suppressing grass resulted in more than double the stolon population density, a higher proportion of plants with tertiary and quaternary branches, and on marked stolons, five times more branches and 60% higher dry matter (DM) produced during winter but with shorter petioles compared with clover in untreated plots.It is concluded that white clover has the capacity to branch during a mild winter and as stolon branch numbers can suffer a net loss as a result of the presence of the grass canopy, management that controls grass growth during winter should aid over‐wintering and improve persistence of white

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02329.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe manurial value of liquid anaerobically digested sewage sludge (LAS), surface applied once at four different times during winter to contrasting swards, was assessed over each of three growing seasons by comparison with fertilizer N. Four nominal rates of N (0, 18, 36 and 54 kg ha−1) were used based on the inorganic N content of LAS. Herbage dry matter (DM) and N uptake responses were measured by cutting three times per year.Application of LAS in late winter compared with early winter led generally to greater N uptake and DM production. Herbage production response from LAS ranged from 5·4 to 30·1 kg DM kg−1N; within this range, larger responses were obtained from a sown sward than from permanent pasture. The apparent efficiency of LAS compared with fertilizer N ranged from 0·41 to 0·88 (permanent pasture) and 0·20 to 0·77 (sown sward) but occasionally mean apparent efficiencies of over 1·0 occurred because fertilizer N was poorly recovered. There was no residual effect on annual N uptake from applying sludge. It is concluded LAS is a useful nitrogenous manure when applied to grassland in late winter/early spring but more research is needed to elucidate the importance of pathways of N losses following the surface application of LAS, and to quantify th

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02330.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects on productivity, botanical and chemical composition of cutting species‐rich hay meadows in Somerset on four different dates between late May and early September in two consecutive years, were measured. Plots that had received 200 kg N ha−1year−1with low levels of P and K for the previous 5 years were compared with plots that had previously received no fertilizer.Previous fertilizer treatment increased metabolizable energy (ME) production only with cutting in May. Dry‐matter (DM) yield increased significantly with date of cutting until August, whereas ME value declined correspondingly. There was no difference in either yield or quality of herbage cut between August and September. ME output per hectare increased very significantly between May and July, but showed no further change between cutting dates.Botanical diversity was reduced by cutting in May after 1 year and by cutting in either May or September after 2 years, and was greatest with cutting in August. The dominance ofHolcus lanatuson previously fertilized plots increased after cutting in either May or September. The contribution to vegetation cover of species that regenerate primarily by seed, including annuals, was greatly influenced by cutting date in preceding years, whereas species that regenerate vegetatively were not a

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02331.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study used both experimental evidence and a mathematical model to address some differences in interpretation in the literature on the relationship between sward height and the bite dimensions (bite depth, bite area and bite mass) of sheep grazing contrasting vegetation types. Individual non‐fasted sheep were released onto small areas (10 × 10m) of white clover (Trifolium repens) and perennial ryegrass (Lolium perenne) and bite dimensions were measured as they grazed across patches (0·7 × 0·7 m) of predetermined sward surface height (SSH). Sward heights were 4, 7, 10, 13 and 16cm for white clover patches and 4, 6, 5, 9, 11·5 and 14cm for ryegrass patches. Four sheep were assigned to each plant species and each sheep grazed one patch of each height (five patches/sheep). Bite depth, bite area and bite mass increased linearly with SSH in both white clover and ryegrass. At a given SSH, bite depth was similar in white clover and ryegrass, but bite area and bite mass were greater in white clover than in ryegrass. The linear relationships observed between bite mass and SSH contrasted with the asymptotic relationships observed in some other studies, but it is suggested that different relationships may arise because of methodological differences between studies. Furthermore, when linear relationships for bite mass were compared with asymptotic relationships for bite mass in a mechanistic model of animals grazing from ryegrass‐white clover pastures it was demonstrated that the nature of the relationship had relatively little effect on the relationship between intake rate and SSH. This was because intake rate depended on the fundamental mechanistic relationship between bite mass and prehension bite rate. This relationship meant that the greater bite masses found when linear relationship were assumed were associated with reduced prehension bite rates and thus the effect on intake rate was relatively small. In addition, the predictions of the model regarding the bases of diet selection by animals grazing ryegrass‐white clover mixtures were simplified, and stabilized, when linear relationships we

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02332.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAbstract Four sward height treatments were imposed by continuous variable stocking using at least ten Suffolk × Greyface lambs per plot from late July to late August: constant 3·5 cm. constant 6·0 cm. 3·5cm increasing to 6·0 cm and 6·0 cm decreasing to 3·5 cm. The treatments were established on two swards given fertilizer N applications over the season of 97 and 160 kg N ha−1respectively.Animal density was greater on the high fertilizer treatment, at the lower sward height and especially on the decreasing height treatments. Liveweight change of lambs was higher (P<0·001) on the 6‐cm than on the 3·5‐cm treatments (+159vs‐13g d−1and was also higher (P<0·001) on the increasing than on the decreasing sward height treatments (+92vs‐26 g d−1). Herbage organic matter intake (OMI), measured on two occasions in the experiment, was greater (P<0·001) on the 6·0 cm than on the 3·5‐cm sward heights whereas values for the increasing sward height treatments were much greater than those for the decreasing sward height treatments. There was little difference in the organic matter digestibility of the diet between treatments. Diets were composed largely of lamina, although there was more pseudostem and dead herbage in the diets of Iambs grazing the decreasing than the increasing sward height treatments at the end of the experiment. Bite mass was closely related to OMI but the treatment and period differences were relatively greater than for OMI. Bite mass was more closely related to the depth of the lamina layer (sward height‐pseudostem height) than it was to sward height. There was evidence that pseudostem acted as a barrier to defoliation on these short swards and also that the proportion of youngest leaf in the diet was positively related to sward height and to increases in sward height.Sward height and especially the direction of change in sward height, together with associated stock density, were potent influences on lamb growth rate. This was a consequence of differences in herbage intake, which was st

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02333.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of sward height on the liveweight gain of yearling farmed red deer stags grazing permanent upland pastures in the UK in two successive years is described. The swards received nitrogen fertilizer at a rate of 218 kg ha−1. Red deer stag calves, which had been weaned in September and housed over winter on a hay and concentrate diet to gain on average 57 g d−1in year 1 and 75 gd−1in year 2, grazed at one of fourmean sward heights of 4, 6, 8 and 10cm from the beginning of June until September. Liveweight gains were recorded over a period of 15 weeks. All animals were slaughtered and carcass weights were recorded after the end of the grazing period. Liveweight gains and final live weights and carcass weights were significantly (P<0·05) lower on the 4‐cm sward than on the other swards, but there were no differences between the performance of animals on the 6‐, 8‐ and

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02334.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFourteen grass/legume mixtures, mostly including white clover or lucerne, in association with a variable number of other forage species were grown at six Italian alpine and subalpine locations under a mowing regime. The response of the mixtures in terms of dry‐matter (DM) yield and visually estimated legume percentage over the second and third years of crop cycle was investigated through an additive main effects and multiplicative interaction (AMMI) analytical model. Locations and mixture‐location interaction effects were significant whereas mixture was not. The interaction effect was very large, and the first two interaction principal component (PC) axes were significant at P<0·001. PC 1 accounted for 88% and 92% of the interaction variation for DM yield and legume percentage respectively. Both for sites and for mixtures, the ordination on PC 1 for these variables was very similar, indicating that the interaction effects for DM yield tended to parallel those for legume percentage. The adaptive response of the mixtures mainly depended on the response of their legume components. White clover was specifically adapted to locations with high soil clay content, probably through better tolerance to the associated severe waterlogging. Lucerne performed relatively better at high‐yielding, favourable sites, probably because of its greater competitive ability than associated grasses under conditions that emphasize competitive effects. Minor interaction effects were related to the response of cocksfoot and timothy, the latter being indispensable for high DM yield of mixtures at high‐elevation, cool‐summer sites. No clear advantage of having a high number of components in the mixture was apparent, and it was concluded that the association of timothy and cocksfoot with one legume should be adequate for most situations in the gi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1995.tb02335.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY