摘要:

AbstractDue to intensive Fertilizer application most silage crops contain appreciable amounts of nitrate. During silage fermentation the nitrate is completely or partially degraded. End‐products are ammonia and nitrous oxide with nitrite and nitric oxide occurring as intermediates. Factors that influence nitrate degradation and the levels of end products and intermediates found in silages are reviewed. The role of plant nitrate reductase and of enterobacteria, Clostridia and lactobacilli in nitrate catabolism and the significance for silage quality are discussed. Attention is paid to silo‐filler's disease, an illness of farm workers that is caused by inhalation of oxides of nitrogen, and to the occurrence of nitrosamines in sila

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01714.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractTiller pulling was studied in a perennial ryegrass sward that was continuously grazed by cattle. The treatments included severe (sward height after grazing 25 mm), medium (50 mm) or lenient (75 mm) grazing from turn‐out in April to 1 June, followed by grazing to 50 mm in the remainder of the season. Tiller pulling was confined to the midsummer‐autumn period of the grazing season. The losses were most severe in swards that had been leniently grazed to a mean height of 75 mm during the spring and least severe in swards grazed to a height of 25 mm. The lenient grazing treatment allowed both the true stem development and aerial tillering whereas in the more tightly grazed swards true stem development was significantly less and aerial tillering was virtually absent. The pulled organic matter in the lenient treatment was equivalent to about 5·3% of the total harvested yield. In the severely grazed swards, pulling losses were equivalent to about 1·7% of the total harvested yield. A high rate of turnover of the pulled herbage was found in all the treatments with between 69 and 78% of the freshly pulled herbage disappearing within a week of being pulled. Tiller pulling was found to have no effect on either the subsequent autumn‐winter tiller density or yields of cuts taken in the followi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01715.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractContinuous stocking with sheep at high stocking rates may reduce the content of white clover(Trifolium repens)in mixed grass‐clover swards. The present experiment was carried out to investigate the effects on sward production and composition of resting a perennial ryegrass(Lolium perenne)‐white clover sward from grazing and taking a cut for conservation.Swards were set‐stocked with 25 and 45 yearling wethers ha−1either throughout a grazing season, or on swards that were rested for a 6‐week period and then cut in early, mid‐ or late season. In an additional treatment swards were cut only and not grazed.Net herbage accumulation was higher at the lower of the two stocking rates and was marginally increased by the inclusion of a rest period at the high but not the low stocking rate. Clover content was higher at the lower stocking rate and was increased by the inclusion of a rest period by 30% at 45 sheep ha−1and by 11% at 25 sheep ha−1The effect was most marked at the end of the rest period before cutting. When rested from grazing the tiller density of ryegrass decreased although tiller length increased, and clover stolon length, petiole length and leaflet diameter increased though leaf and node number per unit length of stolon decreased; the reverse applied when the sward was returned to grazing after cutting.At the high stocking rate, rest periods in mid‐season or later maintained the greatest clover content and marginally increased total net herbage accumulation. At the low stocking rate the timing of the rest period had no significant effect on total net herbage accumulation or on clover content.These results show that the combination of grazing and cutting is of benefit where the stocking rate is high enough to threaten clover survival and limit sheep performance. However, at such a stocking rate, feed reserves are at a minimum throughout the grazing season and so opportunities for resting the sward

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01716.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractPasture variables measured in eight experiments at Kyabram, Victoria were used to quantify factors influencing the consumption of irrigated pastures grazed by dairy cows. In addition, whether intake prediction equations based on sward characteristics could be developed and applied in the field was also considered.Herbage intake (DMI) was positively related to herbage allowance (HA) in all cases; however, the increase in daily DMI achieved for every additional kg herbage offered to a cow ranged from 015 to 0·35 kg. Herbage intake was also consistently related to residual herbage (RH). For every additional tonne herbage dry matter (DM) ha−1remaining after grazing, each cow consumed increased daily amounts of herbage ranging from 3·2 to 5·1 kg DM. However, of the other pasture variables, herbage mass (HM), pasture type (PT) and digestibility of the herbage DM on offer (DMD) influenced herbage intake less consistently.When the data from all experiments were included together, DMI was influenced by sward characteristics in the following manner:where LW = live weight of the cow (kg) and DE = duration of experiment (d).When RH was considered instead of HA, only 61% of the variability in intake was accounted for compared to 80% when HA was considered:In both of these equations, two variables other than the sward characteristics were significant; these were LW and DE. The significance of these variables in these relationships are discussed together with the possibility of using them for predicting DMI in other environments. However, it is concluded that they do not have general applicability and it is suggested that they may be useful only in the environment in which they were gener

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01717.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThree legumes, red clover (Trifolium pratenseL.), alfalfa (Medicago sativaL.) and birdsfoot trefoil (Lotus corniculatusL.), were planted with a minimum‐tillage drill into eight grass fields, three in early spring, two in late spring and three in late summer, in Pennsylvania. The objective was to use pesticides at planting time to control slugs and insects which attack legume seedlings and ascertain whether pest control prevented seedling loss and increased yields of grass and legume dry matter (DM),in vitroDM digestibility and crude protein (CP). Methiocarb bait alone or in combination with carbofuran granules or spray applied at planting sometimes controlled the slugsDerocerus reticulatum(Müller),D. laeve(Müller) andArion fasciatusNilsson and improved establishment of seedling red clover and alfalfa but not birdsfoot trefoil. Increased yields of DM, digestible DM, CP and legume DM after treatment was greatest in late‐spring sowings. Larvae of the clover root curculio,Sitona hispidulus(F.), attacked roots of legumes in the spring following the year of sowing. Late spring and summer sowings without pesticides sustained considerable seedling losses from pests, whereas seedlings from early spring sowings in untreated areas were injured

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01718.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractCanopy structure, productivity and their relationships were examined in 2‐year‐old swards of fourteen tall fescue (Festuca arundinaceaSchreb.) strains during the vegetative and reproductive growth stages. During the vegetative growth stage morphological characters, particularly tiller size, were closely associated with productivity. Swards with large tillers showed an effective distribution of the incoming light energy within the canopy and hence low extinction coefficient (K) value and high productivity at complete light interception. On the other hand, although there was no apparent correlation betweenKand the productivity or the whole crop during the reproductive growth stage, the productivities of the reproductive and vegetative tillers were positively and negatively related to K respectively. Leaf area index of the reproductive tillers and their position in the canopy had marked effects on the distribution of the incoming light energy within the canopy and on the productivity of both types of tillers. The productivity of the vegetative and the reproductive tillers is discussed in terms of the effect of the competition for incoming light energy between both types of till

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01719.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractWith its potential for high yields and high animal output, lucerne appears to be an underexploited crop in British agriculture. In this paper an attempt is made to assess the prospects for expansion of the area of lucerne in Britain from an economic viewpoint, concentrating on lucerne as a conservation crop. Under good management lucerne is shown to have lower production costs than grass and its inclusion in the diet of dairy cows, but not beef cattle, could significantly lower winter feed costs. However, under apparently similar growing conditions, lucerne yields on different farms vary significantly, ranging from 9 to 13 t dry matter ha−1a−1. At the lower yields, the economic attraction of growing and feeding lucerne in place of grass is small. Moreover, since potential lucerne production is concentrated in the south and east of Britain, lucerne competes with other arable crops. For lucerne to offer a gross margin per unit area comparable with these, the price for conserved lucerne would have to be set at a level at which dairy farmers would derive little economic advantage from feeding it. Thus, although lucerne is a forage crop with some potential, at present it is likely to offer economic possibilities only where producers can combine high yields with on‐farm utilization of the

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01720.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractSeparate groups of non‐lactating cows and wether sheep grazed at similar herbage allowances for two successive 5‐d periods on swards that had previously been grazed frequently or infrequently with the intention of creating differences in canopy structure. Measurements were made of sward structure and composition, ingestive behaviour and diet composition. The preliminary treatments had little effect upon either sward conditions or animal behaviour.Herbage mass was reduced from 4020 kg dry matter (DM) ha−1to 3290 kg DM ha−1on average over a 5‐d grazing period as a consequence of the relatively low grazing pressure imposed. This resulted in a mean decline in intake per bite of 28%, and the changes for cattle and sheep did not differ significantly. However, there was a marked difference in the other behavioural responses of the two species; in the sheep biting rate fell and grazing time increased with declining herbage mass, particularly in the sward previously grazed infrequently, whereas the changes in the cattle were small.Differences in the botanical composition of the herbage eaten by cattle and sheep were minor, but there was a small but consistent advantage to the sheep in the digestibility of the herbage eaten.In the first of the two periods the variation in surface height after grazing was substantially greater for sheep‐grazed than for cattle‐grazed swards, indicating more patchy grazing by the sheep.Estimates of daily herbage organic matter (OM) intake calculated from ingestive behaviour variables were high (means 38 and 32 g (kg LW)−1for cattle and sheep respectively) and usually declined substantially over a

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01721.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractA technique for estimating herbage intake by weighing sheep before and after grazing, with an allowance for insensible weight loss (IWL) was evaluated.Live weights were estimated by weighing each animal 200 times using an electronic balance and a microcomputer. This enabled each sheep to be weighed to ± 10 g and overcame the problem of fluctuation in weight due to movement. Mean rates of IWL in housed sheep were 2·3, 1·4, and 0·8 g min−1for walking, standing eating or idling and when lying ruminating respectively. Intake rate (IR) estimated by weighing gave a small but significant bias of −0·8 g min−1when compared with measurements of IR made using housed sheep. Estimates of IWL and IR were made with ewes grazing continuously stocked ryegrass swards maintained at surface heights of 3,6,9 and 12 cm. IWL was higher outdoors than indoors and tended to be higher on the longer swards. IR estimated by weighing gave similar results to those obtained using the chromic oxide technique. At a sward surface height of 3 cm, IR and total intake were lower than for taller swards and total time spent grazing decreased with increasing sward surf

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01722.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractIn two separate feeding experiments using a total of twenty‐four individually housed Ayrshire cows six silages made from perennial ryegrass were offeredad libitumwith supplements of concentrates. In Experiment I herbage with a dry matter (DM) concentration of 225 g kg−1received either formic acid (‘Add‐F’) at the rate of 2·0 litres t−1or undiluted cane molasses at rates of 10, 20 and 30 litres t−l; the mean daily silage intakes were 9·54, 908, 9·27 and 9·49 kg DM per cow and the daily milk yields, corrected to 40 g fat kg−1, were 23·2, 22·3, 22·8 and 22·9 kg per cow respectively but none of the differences between the four treatments was significant. In Experiment 2 herbage with a DM concentration of 269 g kg−1received formic acid at a uniform rate of 2·6 litres t−1either with or without an additional application of molasses at 20 litres t−1; the mean daily silage DM intakes were 8·70 and 9·28 kg per cow and the daily fat‐corrected milk yields were 22·2 and 21·9 kg per cow respectively and were not significantly different. In both experiments the effects of the treatments on milk composition were small and not significant. It is concluded that there were no advantages in applying molasses to herbage treated with formic acid, and that the rate of application of molasses to untreated herbage which equated with the formic acid application was 20·30 litres t−lwhen assessed on the basis of silage

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1985.tb01723.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY