摘要:

AbstractAn ultrasonic rangefinder (sonic sward stick) was developed for rapidly measuring and recording the undisturbed surface height of swards. HFRO and ultrasonic sward stick measurements of undisturbed sward height over continuously grazed pasture were closely related. The measurements obtained with both instruments were related to the sward mass; the distribution of that mass between leaf, stem and dead material had little effect.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02192.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractWhite clover varieties, potentially suitable for inclusion in seed mixtures for mixed stock‐rearing farm systems, were evaluated when growing with S23 perennial ryegrass under rotational sheep grazing with a silage cut in late May or early June, as practiced on farms. Monoculture grass swards were also included to enable the direct and indirect contribution of white clover to total sward production to be evaluated.White clover increased total sward production during all three years of the trial by an average of 50%. Although clover content of swards were similar, large differences occurred in their grass content, especially in the third year, when difference in total yields of swards based on large–leaved clover varieties was 2 t ha−1while difference in clover yield was only 0‐6 to ha–1The indirect contribution of white clover, namely the extra grass resulting from N transfer, was greater in the spring than in the autumn. It was also greater for Nesta than for other varieties. and exceptional for this variety in that the increase in grass yield above that of grass monoculture was maintained over three harv

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02193.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIntensive grazing of pastures may cause drastic and rapid changes in swards which have major effects on ingestive behaviour and diet. Twelve adult Angus cows (Bos Taurus), mean live weight of 482±19 kg, were allowed to graze on swards of lucerne (Medicago sativaL.) that were not grazed (TO), or had been grazed previously for 1 h (T1), or 2 h (T2) in a balanced changeover design. Herbage dry ma er (DM) masses (>5 cm) were 2611, 1895 and 1441 kg ha−1; leaf fractions were 0‐48, 0‐29 and 0‐14; and herbage DM allowances per animal were 10·6, 7·9 and 6·0 kg h−1for TO, T1 and T2, respectively. During a 1 h measured grazing session that followed an overnight fast, cows ingested 2‐93, 1·71 and 0·66 kg DM h−1with herbage DM intakes per bite of 1·6, 0·9 and 0·4 g for T0, T1. and T2, respectively. Rates of biting did not respond to sward treatment and averaged 30 bites min−1. Intake of leaf DM was estimated at 98, 70 and 6% of total DM intake for the same treatment sequence. Utilization of herbage allowance was 0·29, 0·23 and 0·12, for TO, T1 and T2, respectively. Metabolzable energy (ME) intake per animal was 30, 17 and 5 MJ h−1and ME intake per bite was 16, 9 and 3 KJ for TO, T1 and T2, respectively. Data show that grazing‐induced differences in sward characteristics moderate bo

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02194.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn experiment 1, a mixture of perennial ryegrass and white clover (176 g DM kg−1) was ensiled with no addition, or with the application ofLactobacillus plantarum, 3 × 106(g fresh weight of herbage)−1or enterobacteria, 3 × 106(g fresh weight of herbage)−1or both of these inoculants. Silos were incubated at either 18°C or 26°C for 7 d and sealing of half of the silos was delayed for 48 h. In experiment 2, cocksfoot (247 g DM kg−1) was ensiled with no additive, with the application ofL. plantarum, 4 × 106(g fresh weight of herbage)−1enterobacteria, 4 × 106(g fresh weight of herbage)−1or ammonium nitrate, 5 g (kg herbage)−1. Silos were incubated at 18°C and sealing was delayed for 48 h.In neither experiment were the untreated silages of satisfactory quality after 35 d ensilage, having pH's of 4·3 and 6·4. and ammonia‐N concentrations of 139 and 209 g N (kg total N)−1in experiments 1 and 2 respectively. The poorer fermentation in experiment 2 reflected the lower water‐soluble carbohydrate (WSC) content of the ensiled herbage (136 and 53 g WSC (kg DM)−1in experiments 1 and 2 respectively). Inoculation withL. plantarumsignificantly reduced silage pH and the concentrations of ammonia‐N (experiment 1 only) and ethanol and increased lactic acid concentrations. Inoculation with enterobacteria had only minor effects in each experiment.In experiment 1, incubation at 26°C increased the rate of fermentation in the silos as pH was significantly lower after 7d incubation at 26°C than at 18°C, but this effect had largely disappeared after 35 d incubation. When sealing of the silos was delayed for 48 h, the resulting silages had significantly higher pH and ammonia‐N contents than silages from silos that had been sealed immediately after filling.In experiment 2, addition of ammonium nitrate significantly reduced the concentrations of ethanol and acetic acid in silages opened after 7 d. After 35 d the concentrations of ethanol were significantly reduced and those of ammonia‐N increased by the addition of ammonium nitrate. There were marked increases in silage pH between 7 and 35 d ensilage and in the concentrations of ammonia‐N and acetic acid in the silages that had been ino

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02195.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA mathematical model is presented that predicts the time‐course of aerobic deterioration in grass and whole‐crop maize silages. The model predicts the stability of the silage taking into account the buffering capacity of the silage, the initial contents of organic acids and ethanol, pH, the initial temperature and the initial populations of the microorganisms. The specific processes simulated include the growth of yeast and acetic acid bacteria, the oxidation of fermentation products, the consumption of oxygen and the production of carbon dioxide, the rise in temperature. and the increase in pH.The deterioration of silage is seen to be initiated by acetic acid bacteria or by yeast, or by both groups together. The factors that determine which groups will prevail are the dry matter contents and the chemical composition of the silage. The output of the model is validated by comparison of the simulated data with data from published work on the deterioration of sil

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02196.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo systems of grazing management involving preferential treatment of high‐ yielding dairy cows were compared with a grazing system in which both high‐ and low‐yielders received uniform treatment. Cows were rotationally grazed across I‐day paddocks without concentrate supplementation from 23 April to 8 October 1985, with a mean stocking rate over the season of 5‐4 cows ha−1. Preferential treatment of high‐yielding cows was achieved either by using a leader/follower approach (LF) with high‐yielding cows in the leader group, or by preferential forage feeding (PFF) where high‐yielding cows were allowed access to grass silage for 1 ‐5 h daily and grazed alongside low‐yielders. Control (C) cows grazed together as a single group. The high grazing stocking rates used on all three treatments resulted in good grass utilization with residual sward heights, assessed by a rising‐plate sward stick, of 45, 50 and 48 mm for the LF, PFF and C treatments respectively. Animal performance data for the LF, PFF and C treatments respectively were: milk yield (kg d−1) 15middot;1, 15middot;6 and 14middot;7 (s.e. 0middot;78); milk fat yield (g d−1) 598, 606 and 567 (s.e. 34); milk protein yield (g d−1) 500, 519 and 480 (s.e. 31); and live weight gain (kg d−1) 0middot;12, 0middot;23 and 0middot;25 (s.e. 0·05). These results indicate that leader/follower grazing had little overall effect on animal performance when high grazing severity was imposed, with the improvement in animal performance of high‐yielding cows in the leader group being offset by the reduced performance of the follower group. Buffer‐feeding of high‐yielding, rotationally‐grazed cows with high‐quality grass silage had little effect on animal performance and resulted in a decrease in the efficiency of grassland utilization. Silage appeared to substitute for herbage, with a reduction in herbage DM intake

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02197.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractHarvesting techniques, which involve simultaneously preserving and upgrading mature crops of whole cereals using an alkali, have been developed. When treated crops have been fed to sheep and cattle, satisfactory intakes and growth rates have been observed. With the possibility of falling cereal prices, such an end‐use for grain crops may be attractive in the future. Accordingly, a mathematical model of the production, harvesting and utilization of whole‐crop wheat and grass silage has been developed to examine the economic implications. Using the model, the comparative costs of growing and feeding alkali‐treated whole‐crop wheat in place of grass silage for winter milk production have been examined.A milk production system based on whole‐crop wheat rather than grass silage is estimated to improve profits by up to £130 per cow. However, the improvement in profitability is very sensitive to assumptions about the uses for surplus land or silage arising from such a switch. Furthermore, for physiological reasons it may be prudent to restrict the quantity of whole‐crop wheat fed to about 50% of the total forage intake. Thus, whole‐crop cereals may best be seen as a complement to rather than a substitute for grass silage. However, in the absence of data on feeding dairy cows with treated wheat silage, research is required before the computer simulations can b

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02198.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe percentage of clover in a mixture of Huia white clover and Melle perennial ryegrass decreased during each of three winters. In the most severe winter, both grass and clover suffered a net loss of weight, clover losing two–thirds of its maximum weight while grass lost about one–third. In the mildest winter, grass continued to gain weight throughout, while clover lost weight. Such losses, when combined with conditions such as the use of nitrogen fertilizer, which prevent a recovery of clover percentage during summer, will lead to a long–term decrease in the clover content of a sward.The losses from the clover were contributed to by all plant parts especially leaf, which lost between 60% and 95% of lamina weight. The change from autumn to winter caused a greater decrease in the number of live leaves per shoot. and in the area and weight of individual leaves, in clover than in grass. Other work has shown that there is a greater decrease in photosynthesis in clover than in grass, probably owing to changes in canopy structure; this is one cause of clover's poor performance, though differences between the two species in the effect of winter on the distribution of the carbon fixed in photosynthesis and in losses of weight in respiration and tissue death may also be inv

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02199.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA small‐plot cutting trial was carried out 1983‐85 at North Wyke Research Station, Devon to compare the dry matter (DM) production and response to nitrogen (N) of a naturally occurringAgrostis stolonifera‐dominant sward, developed under low fertility conditions on a poorly structured soil. and a sward ofLotium perennecv. Melle, direct‐drilled in 1982 at the same site. All plots received standard inputs of P. and graded inputs of K, related to the four annual N treatments (0, 200, 400 and 800 kg ha−1, in seven equal applications). All plots were cut six times each year, except in 1983; DM yield, herbage digestibility, herbage N concentration, response to applied N, apparent recovery of applied N. and botanical composition of the swards were recorded.On average, A.stolonifera gave69% of the DM yield of L.perenne. A. stoloniferadid not out‐yield L.perenneat the low N levels (0 or 200 kg N ha−1a−1), or in mid‐season. and yielded significantly (P<0‐001) less in drought conditions in 1984 (4‐4 t DM ha−1and 6‐9 t DM ha−1, s.e.d.±0‐22). Average digestibility of A.stoloniferawas 3 units of D‐value lower (P<0‐001) than L.perenne, but N concentrations were higher (3‐01% and 2‐53%, s.e.d. ±0‐074). However, total yields of N from A.stoloniferawere lower. Responses in DM production per kg N applied were lower in A.Stoloniferathan in L.perennefor all N increments, except the highest, (400‐800 kg N ha−1). Fitted response curves allowed interpolation of the values of DM yield (Y10) and N input (N10) where the response was 10 kg DM (kg N)−1. Values of Y10for A.stoloniferaand L.perenneaveraged 7‐1 t DM ha−1and 12‐9 t DM ha−1respectively. and values of Mo averaged 460 kg N ha−1and 570 kg N ha−1, which further indicated the lower responsiveness of A.stoloniferato applied N. Apparent recovery of applied N was generally low, with significantly higher values (P<0‐001) for L.perennein 1983 and 1984, but not in 1985. The botanical composition of L.perenneswards with no applied N showed a steady and rapid decline in ground cover by the sown species. AH L.perenneswards showed an abrupt decrease of L.perennecover in late 1985, with invasion by A.stoloniferaat all but the highest N level (800 kg N ha−1). A.stoloniferatreatments receiving 400 or 800 kg N ha−1showed initial expansion of their native L.perennepopulations; however, these declined after the drought in 1984. Only low levels of L.perennecover remained in the A.stoloniferaswards at the end of the trial; these were unaffected by N level. It was concluded that under the conditions of this trial, A.stolonifer

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02200.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPermanently marked tillers of five perennial grasses, native to the mixed‐grass prairie of North America, were monitored to determine patterns of defoliation, architectural attributes influencing probabilities of defoliation. and post‐defoliation responses. Frequency of tiller defoliation was greatest for one of the dominant midgrasses, intermediate for the remaining midgrass and two dominant shortgrasses. and least for the subdominant midgrass. Midgrass species, including the infrequently grazed subordinate species, were consistently grazed more intensively than the shortgrass species. However, the relative intensity of defoliation did not vary among species or grazing periods indicating that intensity of defoliation was primarily a function of pre‐defoliation tiller height. Tiller architecture, including height, lamina number and the presence of reproductive culms, did not significantly influence frequency or intensity of defoliation within a species. The lack of evidence supporting tiller architecture as a selection criterion within a species suggests that animals were selecting on vegetation parameters at higher levels of vegetation organization than individual tillers. Grazed tillers of the three midgrasses exhibited greater relative rates of tiller elongation between grazing periods than non‐grazed tillers, particularly early in the season when environmental conditions for growth were most favourable. The patterns of interspecific tiller defoliation observed in this study parallel the long‐term patterns of grazing‐induced species replacement observed in thi

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1990.tb02201.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY