摘要:

AbstractA hay drying model (HAYDMO) which predicts the moisture content of pasture hay is described. It uses multiple regression equations based on field drying experiments with conditioned and unconditioned hay and predicts hourly changes in moisture content for both day and night and also those due to rain. The model can be used with three different combinations of weather, including hourly wet and dry bulb temperatures, radiation, wind speed and rainfall. Testing HAYDMO revealed a satisfactory agreement between predicted and observed moisture contents

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01903.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractInvertebrate numbers were studied in two white clover cultivars trials, grown with perennial ryegrass Weevils (Sitonaspp.), slugs, lucerne flea, leatherjackets and as were more common (at least at some life stage) in cultivars of lower cyanogenic potential. Damage to clover foliage by the first three species was also negatively related to cyanogenesis. The production of HCN ranged from 0.025 mg to about 1.8 mg g−1fresh leaf. There was no evidence of any other factor influencing cultivar preference.Cyanogenesis had most effect on numbers of weevil larvae and leatherjackets. The effect on weevil larvae was attributed partly to intercultivar differences in oviposition, but it was also suspected that larvae had fed on cyanogenic parts of the plant before reaching the root. Leatherjacket numbers developed inter‐cultivar differences during larval growth. In one case these differences were detectable by December. By March in the second experiment there were approximately three times as many leatherjackets at the low as at the high end of the cyanogenic range. Approximately four times as manySitona larvaewere found at the lower as at the higher end of the scale. There was some evidence that a higher clover content in the sward was attractive to ovipositingTipula paludosabut not in recently harvested cultivars of high cyanogenic poten

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01904.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPopulations of lactic acid bacteria (LAB) on lucerne before and after havesting were extensively monitored over a two‐year period and correlated with weather data, various wilting parameters and equipment used for harvest. The LAB on standing lucerne were below detectable levels (<10 colony forming units (CFU) g lucerne−1). Immediately after mowing, low levels of LAB (51 CFU g−1) were found on over half the samples. During wilting, the population of LAB generally increased. The amount of increase was affected primarily by the average air temperature during wilting, the length of wilting and the drying rate. The first two variables were positively correlated with bacterial growth whereas increased drying rate adversely affected LAB numbers. If the LAB numbers in the swath were below 100 CFU g−1prior to chopping, the forage harvester inoculated the chopped lucerne an level of 102to 104CFU g−1, depending on air temperature. Considering these factors, LAB counts on chopped lucerne could be predicted within one order of magnitude approximately 95% of

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01905.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA field investigation into the effect of slurry seeding on the dry‐matter yield and persistence of an Italian ryegrass sward was assessed over a 3‐year period (1984–86) under a regime of three cuts per season combined with sheep grazing in early spring and late autumn. Results showed that slurry plus seed treatments produced up to 30% more herbage dry matter and a significantly higher tiller density than where no slurry or seed were used. Slurry application with and without seed also reduced the proportion of weed grasses (mainly Poaspp.) in the sward. It is concluded that slurry seeding is a useful technique for extending the productive life of an Italian ryegrass

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01906.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractIn a small‐plot trial five grass varieties bromegrass cv. Grasslands Matua, perennial ryegrass CVS. Melle (diploid) and Bastion, Condesa and Meltra (tetraploid) were established as grass/white clover swards with white clover cv. Menna. Productivity was measured under 6‐weekIy cutting both without N fertilizer (No) and with 100 kg N ha−1applied in spring (N100) Evaluation was made over 2 harvest years, 1986–87.Total mean annual production of herbage dry matter (DM) in the first harvest year at No and Nowas 5·07 t ha−1and 6·93 t ha−1respectively. In year 2, corresponding values were 11·81 and 12·67 t ha−1. In year 1, Matua swards at Noand N100yielded 5·08 and 6·65 t DM ha−1compared with 507 and 70 t DM ha−1for the mean of the four ryegrass varieties. In year 2, corresponding values were 12·90 and 12·29 for Matua and 11·54 and 12·78 for the four ryegrasses. In year 1, the digestable organic matter in the dry matter (DOMD) of the Matua swards was lower than that of Melle, Bastion and Condesa at NO, particularly at the first cut. In year 2, differences in DOMD between treatments and varieties were not significant.The proportion of white clover was found to be higher in the Nothan the N100treatment, and also higher in year 2 in most treatments. For theNotreatment Matua swards had the highest proportion of white clover in year 1 (32% compared with 24% for the mean of the ryegrass varieties) but the lowest proportion in year 2 (27% compared with 60% for the ryegrasses). For the Notreatment in year 1 clover production was also 43% higher, on average, from the tetraploid treatments than with Melle as the companion grass; for this comparison in year 2 the differences were not significant.It is concluded that Matua bromegrass/white clover swards receiving no N fertilizer may have a good potential under cutting management. However, the evidence from this trial is that in the second year the proportion of white clover is lower with Matua swards than with perennial ryeg

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01907.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSeveral experiments were performed in spring summer over the period 1982–85 to study the relationships between digestibility of energy (DE), gross energy intake (GEI), acid detergent fibre (ADF) and dry matter (DM) content in pasture.Wether sheep in metabolism pens and fed ad libitum with daily‐cut fresh pasture were used. Two plots with different botanical composition were used to provide herbage; one dominated by Lolium perenne and the other by Holcus lanatus. A high correlation (r= ‐0·91) was observed between DE and ADF. The prediction used a second‐order degree polynomial.Gross energy intake and digestibility of energy were scarcely correlated (r= 0·50) when all cases as a whole were considered. Higher correlations between GEI and DE (r= 0·69) were obtained when only data from pastures where Holcus lanatus prevailed were considered, and still higher (r= 0·91) in those pastures dominated by sown species with DE values lower than 70%.Herbage DM content had a large effect on GEI(r= 0·83) in the pastures dominated by perennial ryegrass with DE higher than 70%, the correlation between DE and GEI being low and negative (r=‐0·36). It is possible, therefore, to predict apparent digestibility of pasture energy from ADF. However, DE is closely related to GEI only in those pastures in which DE is lower than 70%, DM content being an important factor limiting the intake of those fresh pastures dominated by Perennial ryegrass when

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01908.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractRates of leaf extension and senescence were measured over three‐day intervals on neighbouring sets of caged and uncaged tillers on several occasions during summer 1983, both when grazing animals were present and also when they were absent. The weather was dry and drought conditions developed as the season advanced.Comparison of data from caged and uncaged tillers indicated that some consistent differences occurred. Loss of information through grazing (affecting 30% of uncaged, larger than average, tillers), contributed to the significantly reduced estimates of leaf extension of ungrazed, uncaged tillers compared with caged tillers. Senescence rates were higher in the open plot than under the cages; old leaves were grazed on only 8% of uncaged tillers so that data loss was less important as a cause of bias. In the drought conditions prevailing, it was thought that caging in the presence of grazing animals resulted in reduced moisture stress and contributed to the above results.Comparisons of caged and uncaged tillers when grazing animals were absent were made to examine the environmental effects of caging and the slight difference in tiller marking procedure. No differences were found in leaf extension rates, though a trend towards higher senescence rates for the uncaged populations was evident. It was concluded that the criteria limiting the use of cages (a period of protection less than the average interval between both leaf appearance and repeated defoliation) should be extended to include a time limit set by the need to avoid bias associated with the environmental effects of caging and cessation of grazing. To define this time limit better in particular circumstances, the extent and direction of bias in the estimation of leaf extension and senescence rates as affected by period of caging, tiller handling procedures, sward and climatic conditions requires further investigation.In the case of vegetative tillers, estimates of leaf extension rates can be made considerably more precise by using tiller size variables (pseudostem length, total green leaf length, leaf width) as covariates. A suggestion for the number of tillers to be measured per transect is given. However, no such increase in precision can be made for estimates of senescence rate

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01909.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis study investigates forage particle breakdown, which is a factor of potential importance for the low intake of forages, particularly tropical grasses. A comparison was made between fresh leaf blades of a tropical grass, green panic (Panicum maximum var. trichoglume) and a temperate grass, Italian ryegrass (Lolium multiflorum). Leaf blades were chopped into 50 mm lengths and fed to cattle with oesophageal and rumen fistulae. Particle size was assessed on chewed samples immediately after eating and after digestion for 6, 12, 24, 48, 96 h and 3 weeks in nylon bags in the rumen.Chewing during eating reduced particle size more in length than in width and more in green panic than in ryegrass. Mean length was decreased 9·2‐fold and 4·7‐fold for the two species respectively, and mean width 5·4‐fold and 2·3‐fold. Green panic leaf had a higher cell wall content and higher dry matter content than ryegrass leaf.Digestion caused a substantial reduction in the width of the particles but not in the length. Width reduction occurred more rapidly in the ryegrass which was reduced to narrow fibres within 12–24 h of digestion while in green panic the same extent of degradation took<48 h. After 96 h digestion, mean width of the chewed material had been reduced 40‐fold in ryegrass compared with only 165‐fold in green panic; all particles of both species were<1 mm in diameter. The mean length of particles after 96 h digestion was similar to that of the chewed feed. Ryegrass was more digestible than green panic, a difference of 150 g kg DM−1which was maintained from within the first 6 h of digestion up to 96 h digestion. After three weeks the digestibility of ryegrass was c. 50 g kg DM−1higher than that of green panic but the proportion of cell wall that was ultimately indigestible was the same (0

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01910.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractTo investigate links between the anatomy of grass leaves and their resistance to breakdown in the rumen, leaf blades of the tropical grass, green panic (Panicum maximumvar,trichoglume), and the temperate grass, Italian ryegrass (Lolium multiflorum), were chopped into 50 mm lengths and fed fresh to cattle. Particle size reduction of the chewed feed was studied immediately after eating and after digestion in nylon bags in the rumen for 6, 12, 24, 48, 96 h and 3 weeks. The lengths of fibre elements, separated into groups of different diameters, were measured on samples digested for 96 h. The process of tissue breakdown was studied using light and electron microscopy.Green panic leaves had twice the cross‐sectional area of thick‐walled tissues, a higher vascular bundle frequency per unit leaf width, and less, but more densely packed mesophyll, than did the ryegrass leaves. Despite the contribution of these characteristics to greater leaf rigidity, green panic was broken down to a greater degree by chewing than was ryegrass.During digestion, width reduction of the chewed leaf particles was faster in ryegrass than in green panic because of two anatomical features: (i) the straight‐walled intercostal cells of the epidermis in ryegrass were easily separated allowing the epidermis to split, whereas the sinuous walls in green panic were resistant to splitting, and (ii) the epidermis of ryegrass was linked to the vascular bundles by thin‐walled mesophyll cells and was shed when these were digested, whereas in green panic the linkage was via thick‐walled bundle sheath cells causing the epidermis to remain attached for much longer. Ryegrass leaf was reduced to isolated fibres within 24 h digestion; this process took>48 h in green panic. These fibres all had a high resistance to length reduction by digestion irrespective of their anatomical or species origin. Even after 3 weeks in the rumen there was little digestive disruption to the longitudinal walls of these fibres.The isolated vascular fibres of ryegrass were smooth‐surfaced in contrast to those of green panic which were rough owing to attached undigested bundle sheath cells and jagged, broken sections of epidermis; this could influence ease of separation of particles from the digesta mass and flow from the rumen.Anatomical differences between these grasses were, therefore, important in the rate of width reduction of leaf particles during digestion and for the characteristics of the isolated fibre, but not for length reduction of particles duri

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01911.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractProgress in improving the feeding value (FV) of forage plants has been slow despite the benefits to animal production that can result from using plants of intrinsically higher FV. The slow progress is due in part to a lack of consensus on the criteria to be used in breeding or selecting forages of high FV. This paper reports the use of the Delphi technique to obtain such a consensus from an international panel of specialists in grazing animal production.The specialists, from Europe, USA, New Zealand and Australia, ranked eleven criteria for improving the FV of grasses and legumes for liveweight gain and for wool production.In general, the primary criteria chosen were high digestibility, easy communication, high nonstructural carbohydrate, high crude‐protein and, for sheep kept primarily for wool production, a high sulphur‐amino acid content. High relative palatability, high lipid‐content and erect growth habit were ranked as least important. It was generally considered that mineral content and anti‐quality constituents should be monitored rather than making them specific breeding objectives, although some exceptions were noted. Minor importance was attached to having ‘appropriate’ tannins in grasses; however, this was given a high priority in legumes. These criteria, and the desirability of reducing the extent of protein degradation in the rumen are discussed in relation to comments made by pa

ISSN:0142-5242    

DOI:10.1111/j.1365-2494.1989.tb01912.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY