摘要:

AbstractSix varieties of white clover, each grown with perennial ryegrass, four intervals between cuts and two levels of applied nitrogen in all combinations, were compared in a field experiment during the first 27 months after sowing.Increasing the interval between harvests from 3 or 4 to 8–12 weeks increased the yield of white clover and generally did not reduce the proportion of clover in total herbage. Increasing the interval between harvests reduced the number of grass tillers but increased grass yield and the size of grass leaves and increased grass height more than clover height; it also increased the proportion of petiole relative to leaflet in the clover. Differences between varieties in response to interval between harvests were small but supported the view that medium large‐leaved varieties can with advantage be defoliated rather less frequently than small‐leaved ones. The adverse effect of applied N on clover appeared almost equally great with all four intervals between harvests and further research on this topic is suggested. Applied N increased grass height more than clover height and increased the number of grass tillers, the size of grass leaves and grass yield. The medium large‐leaved varieties seemed more tolerant of applied N than the smaller va

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01571.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractSix varieties of white clover, each grown with perennial ryegrass, four intervals between cuts and two levels of applied nitrogen in all combinations, were compared in a field experiment during the first 27 months after sowing. Information about yields, crop fractions, heights and ryegrass tillers has been presented in an earlier paper (Wilman and Asiegbu, 1982). The present paper is concerned with the more detailed studies of white clover, which help to explain the yield results and contribute to the understanding of the response of this species to management when grown in competition with grass.Increasing the interval between harvests increased the length of clover stolon per unit area of ground and increased stolon diameter, petiole length, weight per leaf and number of leaves harvested as a proportion of the number present in the sward while only slightly reducing the rate of leaf emergence, helping to explain the positive effect of increasing the interval on clover yield noted in the earlier paper. During regrowth, successive leaves had longer petioles and the length of individual petioles increased beyond the stage at which the leaflets were fully opened. Weight per leaf in clover increased considerably from April to June and declined to below the April value by October. It was shown that weight per leaf can be greatly increased by increasing the interval between harvests without reducing the number of leaves harvested per unit area per year. The stolon length measurements provided some support for the view that medium large‐leaved varieties of white clover can with advantage be defoliated rather less frequently than small‐leaved varieties. Stolon length was less adversely affected by applied N in the medium large‐ than in the small‐leaved varieties. The small‐leaved varieties had thinner stolons than the medium large‐leaved varieties but about twice the stolon length when no N was applied, and a relatively high proportion of leaves which escaped defoliation. The application of N reduced stolon diameter, increased petiole length and had little or no effect on weight per

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01572.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractTwo experiments were carried out to determine whether the differences in intake and feeding value previously shown between two grass cultivars when offered to ruminants as chopped artificially dehydrated (dried) material could also be demonstrated when the grasses were offered in other forms. Two cultivars of tetraploid Italian ryegrass (Lolium multiflorum), Sabalan and Tetila, were established in the same field in 1975. In 1976 they were grazed and conserved (two cuts of primary growth) as dried material or as silage.The composition of the herbage selected at pasture and conserved showed higher concentrations of normal detergent fibre and acid detergent fibre in the dry matter for Tetila than for Sabalan, but differences between cultivars in digestibility were small. In both grazing and winter feeding trials differences in voluntary intake between the two cultivars were not significant, but at pasture young beef cattle spent less time grazing and tended to spend more time ruminating on Tetila than Sabalan. There was no measure of animal performance at pasture but liveweight gain was 15% higher for Sabalan than Tetila when both were offered to young beef cattle as the sole feed of dried grass or of silage. The voluntary intakes of the three forms of feed were very similar, which in part reflected a similarity in digestibility. However, gains were lower for calves given silage than those given dried grass. This may have been due to a lower efficiency in the utilization of the nitrogeneous components of silage for tissue growth than those of dried grass.

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01573.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractForage brassica catch crops can provide a valuable source of additional feed in the autumn when supplies of other feed are limited. Weaned lambs grazed either (A) a novel hybrid crop, stubble turnip cv. Appin, or (B) a sequence of crops consisting of fodder radish cv. Nerys, followed by forage rape cv. Canard. Forty, 60 or 80 g of crop DM per kg current live weight (LW) were allowed daily and the performance, intake and carcass yield of the lambs were monitored. Lamb LW gains were lower on treatment A (45, 65 and 72 g d‐1) than on B (78, 111 and 117 g d‐1) at the 40‐, 60‐ and 80‐g DM d‐1allowances respectively. Intakes of forage crops, however, did not differ significantly, probably because the estimates of intake were made in the middle of each 14‐d allocation period of the crops. The intake values are thus an indication of the potential intake when a relatively plentiful supply of food is available; they were 19·2, 17·2 and 18·2 g OM kg‐1LW for treatment A and 16·2, 19·2 and 19·2 g OM kg‐1LW treatment B at the 40‐, 60‐ and 80‐g DM d‐1allowances respectively.Mild anaemia occurred in lambs feeding on both crops. Anaemia was more marked on treatment B, which was consistent with the higher concentrations of S‐methyl cysteine sulphoxide (SMCO) but as the performance of animals was superior on treatment B, SMCO intake and anaemia are not thought to be the first or the most important factors in limiting animal performance. Goitrogenic changes in thyroid glands occurred on both crops. Mean weights of paired thyroid glands were 3·22, 4·28 and 4·21 g on treatment A and 3·29, 5·27 and 5·21 g on B at the 40‐, 60‐ and 80‐g DM d‐1allowances respectively; the effects of both treatment and allowance were significant (P<0·21). Thiocyanate concentrations were higher on treatment A than B, indicating differing glucosinolate concentrations. While this was consistent with animal performance, it was not consistent with the weight of thyroid glands. However, the goitrogenic responses may have been complicated by the ingestion of soil iodine because very high faecal ash values were recorded. Thus, glucosinolates appear not to have affected lamb growth rate by their goitrogenic effect but the possibility remains that the

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01574.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractSamples of 39 perennial ryegrass (Lolium perenneL.) and 24 Italian ryegrass (Lolium multiflorumLam.) commercial seed‐lots used at the Grassland Research Institute between 1974 and 1978 were examined for the presence of seed‐borneDrechsleraspecies. The five species ofDrechsleraisolated from the seeds wereD. andersenii, D. siccans, D. nobleae, D. sorokinianaand an unidentifiedDrechslerasp.A high proportion of the seed‐lots were infected but levels of infection were low except in the perennial ryegrass cv. S24. Infection was located more commonly inside the caryopses than externally on the lemmas and paleae, and about 12% of the seedlings growing from infected seeds were infected. The species recovered in the seedlings were the same as those observed on the seeds.There was no relationship between level of seed infection and level of damage observed in the field in the autumn of the first harvest

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01575.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractData from twenty‐two comparisons carried out at ADAS Experimental Husbandary Farms are used to compare untreated and formic acid‐treated silages. Additive treatment led to an improved fermentation in some crops, particularly those of low DM concentration (<262 g kg‐1). Where this occurred there were associated benefits in silage digestibility (+0·234 units), intake (+16%) and the growth rate of young cattle (+0·28 kg d‐1). Where the fermentation of the untreated silage was good, both digestibility and animal performance associated with treated and untreated silages were similar. It is suggested that the justification for using formic acid in a commercial situation is thus restricted to occasions where the untreated crop would be liable to develop a clostridial fermentation. These may be when crops contain less than 35 g water‐soluble carboh

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01576.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThree silages were produced from the same swards by harvesting grass using either a double‐chop harvester (DC) or a precision‐chop harvester adjusted to produce a long staple length (PL) or a short staple length (PS). The mean particle lengths were 47, 52 and 14 mm respectively.Of each material 250 t was ensiled unwilted and with formic acid additive at the mean rate of 2‐4 litres t‐1of grass. All three silages were well preserved and degree of chopping had no effect on fermentation as indicated by either pH, ammonia N or organic acid concentration.The silages were offeredad libitumto seventy‐two British Friesian cows with a mean calving date of 28 January which were in their second or later lactation, in a randomized‐block experiment from day 8 of lactation until 12 April. In addition twelve animals on each silage received a uniform daily concentrate allowance of 7·2 kg while twelve were offered concentrates according to their individual milk yields but with a mean concentrate allowance over the twelve cows of 7·2 kg d‐1. Degree of chopping had no significant effect on either silage dry matter intake or milk yield with mean intakes during the final 21 d of the experimental period of 9·2, 9·2 and 9·2 kg d‐1and mean milk yields of 25·2, 25·2 and 25·2 kg d‐1for the DC, PL and PS silages respectively. Method of concentrate allocation did not affect either the total yield of milk during the experimental period, 1717 and 1697 kg, or the total lactation yield, 5635 and 5711 kg, for the uniform and yield‐related allocation methods respectively. The butterfat and protein concentrations of the milk were not significantly affected by either the degree of silage chopping or the metho

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01577.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe change in structure of continuously grazed versus infrequently cut swards of perennial ryegrass (Lolium perenneL), cv. S23, was investigated during their first full harvest year. Measurements were made from early May until late September. The intensity of stocking by sheep in the grazed sward was adjusted in an attempt to maintain a high level of radiation interception and the cut sward was harvested at approximately monthly intervals.The herbage mass, lamina area index and radiation interception of the cut sward varied in a cyclic pattern between harvests but in the grazed sward these parameters showed considerably less variation, although they all increased early in the season and then declined later. The proportion of dead material above ground increased throughout the season in both sward types but was more marked in the grazed sward.There were major differences between the grazed and cut swards in the number of tillers per unit ground area; the difference became more marked throughout the season and by September the tiller densities in the grazed and cut swards were 3·204m‐2and 6·203m‐2respectively. Divergence in tiller density was associated with differences in specific stem weight and leaf area per tiller.Rates of appearance and death of leaves on tillers in the grazed sward were determined. During May, leaf appearance exceeded leaf death but this was reversed in June. During the rest of the season as a new leaf appeared on a tiller so the oldest leaf

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01578.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA high risk of pest damage to seedlings of white clover (Trifolium repensL.) and perennial ryegrass (Lolium perenneL.) was shown to exist after reseeding with a slot‐seeder. Damage varied between years and sites; white clover appeared to be more affected than perennial ryegrass. Insecticides of feasible commercial use (chlorpyrifos granules and γ‐HCH seed treatment) were found to prevent damage. There was no evidence of phytotoxicity from any of the pesticides studied at the dose rates used in the f

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01579.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractA rising‐plate meter was used in a double sampling technique to measure the herbage mass of rotationally grazed perennial ryegrass‐white clover swards over a period of 2 years. The meter was calibrated by developing a linear regression between meter reading and herbage dry matter mass as measured by cutting 0·2‐m2quadrats to ground level.There was a strong relationship between meter reading and herbage mass, and correlation coefficients were consistently 0·2 or above. The calibration regression was normally constant for extended periods, especially over the winter and spring. The relationship was more variable over the summer but appeared to follow a pattern that was to some extent repeatable between years. The slope of the regression (kg DM ha‐1cm‐1) was 312 and 267 in the two winters and reached values of 800 and 452 in the two summers. The calibration relationship was adequately described by a linear model over the winter and spring but there was a tendency for a curved relationship in mid‐to late summer.The standard pooled regression found with winter ryegrass‐clover swards was not applicable to the more erect prairie grass, and the standard regression overestimated slightly the yield of heavily grazed swards. There was no evidence of a difference in relationship between irrigated and non‐irrigated swards over the summer.The individual meter readings could be used to develop a useful diagrammatic picture of the changes that occurred in sward structure as the pastures were subjected to different managements and this could be used to illustrate problem areas in pasture management.The meter was useful in overcoming the problem of variability of herbage mass within paddocks and could give precise estimates of herbage mass, especially when it was possible to use a pooled regression encompassing a large number of calibration cuts. In these cases the meter could be used to detect differ

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1982.tb01580.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY