bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of addition of urea to a low nitrogen diet on the rumen digestion of a range of roughages
Authors: Dixon R. M.
Published: September 2002

Four steers were given 2 diets consisting of oat hay and molasses which
contained either no urea or 4% urea. Sixteen roughages (including
cottonwool, straws, alkali-treated straws, and grass and legumes hays) were
incubated in synthetic fibre bags in the rumen for 24 h, and the disappearance
from the bags of insoluble organic matter (OM) was determined. In steers given
molasses containing 4% urea, rumen ammonia concentrations exceeded 100
mg N/Lfor only about 5 h during the 24-h cycle and were <50 mg
N/L within about 4 h after feeding. In steers given molasses without urea,
rumen ammonia concentration averaged 7 mg N/L. The depression in OM
disappearance from synthetic fibre bags due to the low rumen ammonia
concentrations, expressed as a percentage of the disappearance at the higher
rumen ammonia concentration, ranged among the roughages from 24 to 87%,
and was inversely related to the N content of the roughage. In additional
experiments the differences in ammonia concentration between rumen fluid
sampled from the ventral sac of the rumen and fluid extracted from synthetic
fibre bags were small compared with the differences between diets. These
results indicated that the effect of low rumen ammonia concentrations on
microbial digestion in the rumen varied widely among roughages.
Micron blowout: heritability and genetic correlations with fibre diameter and secondary follicle diameter
Authors: Hill J. A. , Ponzoni R. W. , James J. W.
Published: September 2002

Calculation of micron blowout as the difference between fibre diameter records
taken at different ages can produce ‘biased’ estimates of the
heritability and genetic correlations due to a scale effect. In some
instances, standardisation of the fibre diameter records to a common genetic
variance (i.e. removal of the scale effect) changed the heritability and the
genetic correlation estimates. The effect of standardisation on the
heritability of micron blowout was determined to a large extent by the
difference in the genetic variance between the 2 fibre diameter measurements,
whereas in the case of the genetic correlation between micron blowout and
another trait, it was also dependent on the genetic correlation between the
other trait and the two fibre diameters. It is recommended that heritabilities
and genetic correlations involving micron blowout be calculated after
standardising the fibre diameter measurements to a common genetic variance.
The practical implications of the results are briefly discussed.
Rumen characteristics, methane emissions, and digestion in weaned lambs reared in isolation
Authors: Faichney G. J. , Graham N. M. , Walker D. M.
Published: September 2002

Twelve Merino lambs were separated from their dams at 2 days of age. Six were
reared in isolation and 6 were inoculated with rumen fluid when 4 weeks old.
Apelleted, mixed diet was available from 10 days of age; milk feeding was
restricted to maintenance from 2 weeks and discontinued when liveweight
reached 9 kg. Three lambs from each group were given a medium intake and 3 a
high intake of the diet.
The isolated lambs had virtually no rumen protozoa; rumen ammonia and volatile
fatty acid concentrations were lower in these lambs but acetate:propionate
ratios were higher. The rumen mean retention time (MRT) of a solute marker was
longer but the microbial turnover time (TT) was shorter in the isolated lambs;
both MRT and microbial TT were shorter on the high intake. Total microbial
synthesis did not differ between groups. The digestibilities of energy,
organic matter, non-structural carbohydrate, and crude protein were lower in
the isolated lambs but those of cell wall constituents were not affected
significantly; digestibilities were lower on the high intake. The isolated
lambs emitted much less methane than the inoculated lambs; consequently,
available energy (i.e. digestible less methane energy), was similar for the 2
groups. Recovery of reducing equivalents in the rumen fermentation was
incomplete in the isolated lambs but could be accounted for if reductive
acetogenesis provided 13% (medium intake) or 16% (high intake)
of the acetate and butyrate formed.
Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass - white clover dairy pastures in western Victoria. 1. Growth and composition
Authors: Jacobs J. L. , McKenzie F. R. , Ryan M. J. , Kearney G.
Published: September 2002

Field experiments were carried out at 2 sites to study the effects of time and
rate of nitrogen (N) application from autumn to midwinter on perennial
ryegrass–white clover pasture dry matter (DM) yield and species
composition. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in
mid-April, early May, mid-May, early June, and mid-June 1996 onto a grazed
pasture. Dry matter yield was estimated when perennial ryegrass in the 45 kg
N/ha treatment reached the 3-leaf stage of development. Species
composition estimates were made on all plots in autumn, late winter, and late
spring (November). Asecond DM yield estimate was taken one regrowth cycle
after the primary DM yield estimate to determine residual N impact on pasture
growth, and then the pastures were returned to the grazing routine of the
farm.
Increasing levels of N fertiliser resulted in a linear (Site 1) and
curvilinear (Site 2) primary DM yield response. Residual DM yield responses
were linear at both sites. The highest primary DM yield response at Site 1 was
9.1 kg DM/kg N (mid-April application), whereas the highest residual N
response was 9.4 kg DM/kg N (mid-May application). The time taken for the
45 kg N/ha treatment to reach the 3-leaf stage of development ranged from
38 (early June application) to 47 (mid-April application) days for the primary
harvest, and from 46 (early May application) to 72 (early June application)
days for the residual harvest. At Site 2, the highest primary DM yield
response to N was 15.8 kg DM/kg N at 45 kg N/ha (mid-April
application), whereas the highest residual N response was 8.3 kg DM/kg N
(mid-June application). The time taken for the 45 kg N/ha treatment to
reach the 3-leaf stage of development ranged from 24 (early June application)
to 36 (mid-April and early May applications) days for the primary harvest, and
from 30 (mid-April) to 57 (early June application) days for the residual
harvest. Based on the current cost of urea, the study concluded that N
fertiliser use during autumn to midwinter is economically viable for dairy
farmers.
Botanical composition was unaffected by N application. There were no treatment
effects on botanical composition of the sward at either site the following
spring (November). It is concluded that a ‘once-off’ strategic N
application up to 60 kg N/ha during autumn to midwinter is not likely to
influence dairy pasture composition in western Victoria.
Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass - white clover dairy pastures in western Victoria. 2. Pasture nutritive value
Authors: Jacobs J. L. , McKenzie F. R. , Ryan M. J. , Kearney G.
Published: September 2002

Field experiments were carried out at 2 sites to study the effects of time and
rate of nitrogen (N) application from autumn to midwinter on the nutritive
value of perennial ryegrass–white clover dairy pastures in western
Victoria. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in
mid-April, early May, mid-May, early June, and mid-June during 1996 onto a
pasture which had been grazed and topped to a uniform height of 5 cm prior to
imposition of treatments. Pasture samples to a height of 5 cm were collected
when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf
stage of development. Samples were analysed for metabolisable energy (ME),
crude protein (CP), neutral detergent fibre (NDF), and water-soluble
carbohydrates (WSC).
Increasing rates of N gave rise to a curvilinear (Site 1) and linear (Site 2)
increase in pasture ME and CP content. The actual response of 0.007 MJ/kg
DM. kg N at 45 kg N/ha was the same at both sites, regardless of N
application time, and corresponded to an increase of 0.32 MJ/kg DM. At
Site 1 the actual increase in CP content at 45 kg N/ha (0.067% per
kg N applied) was the same for all application times and corresponded to an
increase in CP content of 3%. For Site 2, the increase ranged from
0.040% (mid-April) to 0.098% (mid-May) per kg N, corresponding
to a pasture CP content increase of 1.8 to 4.4% at 45 kg N/ha,
respectively.
The application of N gave rise to a curvilinear (Site 1) and linear (Site 2)
decrease in pasture NDF. For Site 1 at 45 kg N/ha, the actual decrease
ranged from –0.04% (early May) to –0.10% (mid-May)
per kg N, corresponding to a pasture NDF content decrease of 1.69 to
4.61%, respectively. At Site 2, the actual decrease in NDF content
(–0.04% per kg N applied) was the same for all application times
and corresponded to a decrease of 1.58% at 45 kg N/ha. Apart from
some exceptions, increasing rates of applied N gave rise to a linear (Sites 1
and 2) decrease in pasture WSC content. For Site 1, the change in pasture WSC
content ranged from 0.007% (early May) to –0.032%
(mid-June application) per kg N, corresponding to a change in pasture WSC
content of 0.32 to –1.44% at 45 kg N/ha, respectively. At
Site 2, the change in WSC content ranged from 0.0004% (mid-April) to
–0.076% (mid-May) per kg N, corresponding to a change in pasture
WSC content of 0.02 to –3.42% at 45 kg N/ha, respectively.
In this study, N application had a positive effect on the nutritive value of
dairy pastures in the autumn to midwinter, in western Victoria. This is
particularly important for the provision of quality feed during this period as
the majority of dairy herds in the region are calving at this time. Thus, the
provision of an increased quantity of higher quality feed may lead to a
reduction in the requirement for purchased feeds.
Landform and phosphorus effects on nitrogen fixed by annual clovers and its contribution to succeeding cereals in the Ethiopian highlands
Authors: Haque I. , Lupwayi N. Z.
Published: September 2002

Poor drainage of Vertisols and nitrogen (N) and phosphorus (P) deficiencies
are some of the major constraints to food and feed production in the Ethiopian
highlands. The effects of soil drainage and P supply on N fixation by annual
Trifolium species and their residual value to succeeding
crops was investigated in field experiments on Vertisols at Addis Ababa and
Ginchi. In one experiment, the Trifolium spp. fixed
55–122 kg N/ha when P fertiliser was applied, and the increase in
grain yields of oats following different clovers ranged from 20% for
T. steudneri to 55% for T. rueppellianum compared
with yields of continuous oats. In another experiment, landform treatments
designed to effect drainage had no significant effects on N fixation and
clover dry matter, or on yields of wheat following the clovers. Phosphorus
applied at 50 kg P/ha increased N fixation from 11 to 72 kg N/ha on
the broadbed-and-furrow landform and from 10 to 64 kg N/ha on the flat
landform, and herbage yield responded similarly. Only the wheat following
P-applied clover, particularly when supplemented with N fertiliser at 50 kg
N/ha, had significantly higher wheat grain yields compared with continuous
wheat grown without N fertiliser. These results confirm the critical
importance of P in increasing the productivity of clovers in the Ethiopian
highlands.
Effects of different cultural practices on spread of cucumber mosaic virus in narrow-leafed lupins (Lupinus angustifolius)
Authors: Bwye A. M. , Jones R. A. C. , Proudlove W.
Published: September 2002

Lupinus angustifolius (narrow-leafed lupin) was sown in
7 field experiments to examine the effects of cultural practices on incidence
of cucumber mosaic virus (CMV). The factors investigated were row spacing,
banding fertiliser below seed, straw groundover, and tillage. The seed sown
carried 5–15% CMV infection. Seed-infected plants were the
primary source for subsequent virus spread by aphids. Incidence of
seed-infected plants and the extent of virus spread were gauged by counting
numbers of lupin plants showing typical seed-borne and current-season
CMV symptoms. Due to greater competition with other plants within wide than
narrow rows, wide row spacing diminished the survival of seed-infected plants
by 46%. Increased plant growth from banding superphosphate below seed
did not significantly decrease numbers of seed-infected plants surviving.
Straw spread on the soil surface suppressed final CMV incidence by
25–40% and, when applied at different rates, diminished recorded
CMV incidence more at 4 than 2 t/ha and least at 1 t/ha. Where there
was no straw, CMV incidence increased faster with narrow spacing than wide
spacing. Soil disturbance from sowing seed with double discs instead of tynes
significantly increased incidences of both seed-borne and current-season
infection and diminished grain yield. Neither straw nor row spacing treatments
significantly affected grain yield, but the decrease in CMV spread due to
straw ground cover significantly increased individual seed weight once and
overall yields were greater with straw. Myzus persicae
was the main colonising aphid species but
Aphis craccivora and
Acyrthosiphon kondoi also colonised the lupins. There
were significantly fewer colonising M. persicae in plots
with 4 t/ha of straw than in those with none. This work suggests that
stubble retention, minimum tillage, and wide row spacing should be included as
components of an integrated disease management strategy for CMVin
L. angustifolius crops.
Variability of Ascochyta fabae in South Australia
Authors: Stoddard F. L. , Kohpina S. , Knight R.
Published: September 2002

Fifty-two isolates of Ascochyta fabae were established
from 23 collections made in 3 States of Australia and were purified through 2
cycles of single-spore isolation. The isolates were evaluated for spore size,
spore production, colony diameter, aerial mycelium, and pycnidia production.
Variation in all of these traits among related single-spore cultures was
comparable to that among unrelated ones and only colony diameter varied
significantly among isolates. Spore size was 3–6 by 10–26
µm.
Eight of these 52 isolates were chosen for further investigations of
pathogenicity characteristics using 8 populations of faba bean. Plants were
scored daily for rate of appearance of symptoms and then 15 and 21 days after
inoculation for lesion size and number, production of pycnidia on the lesions
and overall disease score. Leaves and stems reacted differently to the
disease, with one isolate producing many leaf lesions but few stem lesions on
one bean accession but many stem lesions on another. Lesion size was not
strongly correlated with the other measures of disease. Resistant accessions
had longer incubation periods, fewer total lesions and fewer pycnidia-producing lesions than susceptible accessions. The 8 isolates on the 8 bean
accessions showed 7 distinct patterns of resistance. The results showed that
in southern Australia, A. fabae exhibited great
variability which was incompatible with classification into biologically
meaningful pathotypes.
Comparative performance of Lupinus albus genotypes in response to soil alkalinity
Authors: Liu A. , Tang C.
Published: September 2002

Narrow-leafed lupin (Lupinus angustifolius L.) grows
poorly on alkaline soils, whereas white lupin
(Lupinus albus L.) grows relatively well. This study
aimed at examining genotypic variations of white lupins grown in limed acid
and alkaline soils in the glasshouse and to test whether the glasshouse
findings correlated with those observed in the field.
Twelve white lupin genotypes were tested for their tolerance of limed and
alkaline soils in the glasshouse. In limed soils compared with the control
soil, genotypic variation in shoot growth ranged from 58 to 80%, root
weight from 49 to 72%, and leaf chlorophyll concentration from 47 to
96%. In the alkaline soil, shoot weight ranged from 75 to 110%,
root weight from 39 to 63%, and chlorophyll concentration from 58 to
94% of the control. However, iron chlorosis did not negatively
correlate with shoot growth of the genotypes on the limed or alkaline soils.
The results suggest that iron chlorosis may not be used as a sole indicator
for selecting tolerant albus lupins for alkaline soils. Nineteen lines
including those used in the glasshouse were compared in the field for their
ability to grow on an alkaline clay. Large genotypic variation in early shoot
growth was also found; shoot weight on the alkaline soil relative to an acid
soil ranged from 38 to 85%. However, growth performance of the white
lupin genotypes in response to the alkaline soil did not correlate with those
in the glasshouse, indicating that factors other than soil alkalinity might
also be important for the growth of albus lupin. Screening techniques to
identify tolerant genotypes for alkaline soils need to be further developed.
Ecotypic variation for seed dormancy contributes to the success of capeweed (Arctotheca calendula) in Western Australia
Authors: Dunbabin Matthew T. , Cocks P. S.
Published: September 2002

The seed dormancy characteristics of 2 capeweed
[Arctotheca calendula (L.) Levyns] ecotypes
from Western Australia were studied to determine aspects of seed dormancy that
contribute to the success of this species in southern Australia. Short- and
long-term dormancy pattern of buried and soil surface seed, effect of summer
temperatures on afterripening, and effect of temperature on seed germination
were investigated using seed produced in a common environment.
There were large differences in the seed dormancy pattern of the 2 ecotypes
studied. On the soil surface, >95% of seed of the Mt Barker ecotype
became non-dormant and germinated in the first year, the remainder germinating
the following season. In contrast, only 5% of Mullewa seed germinated
in the first year, with 75% germinating in the second year and
20% of seed remaining dormant after 2 years. Cycling of dormancy was
observed for buried seed of both ecotypes, with periods of non-dormancy
corresponding with the likely timing of the break of the season. Dormancy
cycling was also apparent in seed stored under constant conditions in the
laboratory. Burial prevented germination of both ecotypes; however, the
ability to resist germination while buried was lost in 30% of the Mt
Barker seed in the second season. Differences in the duration of dormancy of
soil surface and buried capeweed seed have evolved as an adaptation to the
different environments likely to be experienced by plants at their site of
collection.
All seeds possessed primary dormancy at maturity, with any afterripening
during the first year occurring by the end of summer. Afterripening was
enhanced by exposure to typical soil surface temperatures, providing some
protection against germination during early summer rainfall. Protection from
late summer rains is insured by the inability of seed to germinate at
temperatures >30°C and a relatively slow rate of germination. These
features of capeweed seed dormancy, combined with the ability to evolve
genetically distinct populations suited to particular environments, help
explain why capeweed is so widespread and abundant across southern Australia.
Methane emissions from Australian livestock: implications of the Kyoto Protocol
Authors: Howden S. M. , Reyenga P. J.
Published: September 2002

Human activities have increased the atmospheric concentration of methane by
about 140% since pre-industrial times. The accumulation of methane and
other ‘greenhouse’ gases is anticipated to cause significant
climate changes in the future. Ruminant livestock are the largest producers of
methane in Australia and this source constitutes about 12% of the
national net emissions. Australia is a signatory to the Kyoto Protocol, which,
if it comes into force, requires limiting annual emissions during the period
2008–2012 to 8% over the 1990 value. Australian livestock
emissions are projected to increase by 7% by 2010 with total Australian
emissions expected to increase by 28–43%. Emissions per unit GDP
are higher for the livestock sector than for most other sectors and this may
negatively affect the sector if free market emission trading is implemented
and no new technologies to reduce emissions cost-effectively are introduced.
Using information from the National Greenhouse Gas Inventory, we demonstrate
that reductions in emissions per unit product are already occurring in at
least one Australian livestock industry and discuss ways to ensure that
similar future changes will be recorded. Cautionary notes are made regarding
options of grain feeding and more intensive production, which appear to be
attractive but may lead to increasing emissions when viewed on a broader
basis. The potential for increased animal production with new technologies
developed to reduce methane emissions suggests that there may be significant
opportunities for the Australian livestock industries arising from the issue
of greenhouse gas reductions. Opportunities to establish carbon sinks are also
discussed. We suggest that addressing reduction of emissions per hectare
rather than per head or per kilo of product results in a strong alignment with
the development of more sustainable livestock industries.
Accuracy of SF6 tracer technology and alternatives for field measurements
Authors: Ulyatt M. J. , McCrabb G. J. , Baker S. K. , Lassey K. R.
Published: September 2002

The SF6 tracer technique allows methane production from
individual grazing ruminants to be measured by placing a calibrated source of
SF6 (a permeation tube) in the rumen and determining
the ratio of methane to SF6 in the animal's
breath. The technique can provide estimates of methane production that are
comparable with those determined by respiration calorimetry provided careful
attention is paid to the details of permeation tube calibration, gas
collection procedures, and gas analysis. The SF6
technique indicates that most of the variation occurring in methane production
in the grazing situation is between animals, with small but significant
differences between sampling days. Three types of mass balance techniques have
also been used, where average methane production is measured outdoors from air
flowing across a group of animals. Good agreement can be achieved between
these types of techniques and SF6 measurements. The
advantage of the SF6 technique for animal scientists is
that it can be used under normal grazing conditions and data can be obtained
from individual animals thus allowing treatment comparisons to be made. The SF6 technique therefore provides an opportunity for
countries whose methane emissions derive predominantly from grazing livestock
to obtain accurate estimates of emission and to develop mitigation options.
Ruminal acetogens and their potential to lower ruminant methane emissions
Authors: Joblin K. N.
Published: September 2002

Ruminant methane is a major contributor to the anthropogenic greenhouse gas
inventories of Australia and New Zealand. Direct intervention in the rumen
offers one means for controlling ruminant methane emissions. In this respect,
acetogenic bacteria (acetogens) normally present in the rumen are of interest
because they have the potential to provide an alternative sink for H2, an essential intermediate in the formation of
methane. Although little is known about the populations of acetogens in
grazing ruminants, studies on ruminants fed diets containing concentrates or
conserved forages indicate that the rumen contains a diversity of acetogens
and that some of these have the potential to act as hydrogenotrophs in place
of methanogens. This paper describes the current understanding of ruminal
acetogens and outlines potential applications of acetogens in methane
mitigation strategies. Strategies which use acetogens to outcompete and
displace methanogens are considered less likely to be successful than
strategies which use acetogens to maintain low H2
levels in the rumen following suppression of methanogens. However, the former
cannot be completely discounted at present.
Rumen methanogens, and inhibition of methanogenesis
Authors: Baker S. K.
Published: September 2002

Methane-producing archaea (known as methanogens) are a distinct group of
organisms which are a normal component of the rumen microbial ecosystem.
Hydrogen and carbon dioxide are the principal substrates used by rumen
methanogens to produce methane (CH4). Because hydrogen
and formate are products of fermentation by other microorganisms in the rumen,
inhibition of fermentation by other members of the rumen microbial population
may in turn inhibit methanogenesis. As well, compounds that inhibit the
activity of methanogens directly are likely to reduce or eliminate CH4 production.
A strong inverse relationship between the molar proportion of propionate and
CH4 production is predicted from knowledge of the
interactions among microbial populations in the rumen, and compounds that
promote greater production of propionate in the rumen may also have the effect
of decreasing CH4 production. Although a wide range of
ionophores, antibiotics, and other compounds have been evaluated
in vivo and in vitro for their
influence on rumen microbial populations and on propionate production,
re-evaluation of some of these has been prompted by a search for compounds
that both enhance propionate production and decrease production. Where there
is a focus on CH4 production by livestock, interest
necessarily is in the total amount of CH4 produced per
day as a proportion of gross energy intake (%GEI) and its relationship
with animal productivity. Because enhanced production of propionate in the
rumen also can be associated with an increase in the flow of microbial protein
from the rumen, evaluation or re-evaluation of compounds that may be effective
in reducing methane production should also include evaluation of the effects
on animal productivity, and appropriate approaches are discussed.
Opportunities for biological control of ruminal methanogenesis
Authors: Hegarty R. S. , Klieve A. V.
Published: September 2002

Methane is a major waste product from ruminants, contributing 53% of
Australia's total emissions of the gas. Arange of chemical inhibitors of
methanogenesis are known to be effective but the real and perceived risks to
the environment and health from chemical residues may curtail widespread
application of these products in ruminant industries. As with other
agricultural industries, future control of unwanted organisms (such as
methanogens) is likely to lie with biocontrol agents rather than with
chemicals. Opportunities exist for biological reduction of rumen methane
emissions using direct means (viruses and bacteriocins specific to
methanogens), and indirectly through the elimination of rumen protozoa which
symbiotically support some rumen methanogens. The feasibility of these
approaches and their current research position are discussed. The most
promising work to date is using the common food preservative, nisin (a safe
and naturally occurring bacteriocin). When ruminal contents were incubated
with nisin in vitro, methane emissions were reduced by
36%.
Mechanisms for competitively reducing ruminal methanogenesis
Authors: Hegarty R. S.
Published: September 2002

Methane production is the principal end use of hydrogen gas derived by
phosphoroclastic reactions or the release of protons from reducing equivalents
by hydrogenases in the rumen. It should therefore be possible to reduce
methanogenesis by (1) inhibiting H2 liberating
reactions, (2) promoting alternative reactions which accept H+ during reoxidation of reducing equivalents, and
(3) promoting alternative H2-using reactions.
Strategies to reduce methanogenesis by these means are discussed. Particular
attention is given to increasing synthesis of propionate and long chain fatty
acids in the rumen, to acetogenesis, and to the actions of chemicals such as
monensin and dietary fatty acids.
Reducing rumen methane emissions through elimination of rumen protozoa
Authors: Hegarty R. S.
Published: September 2002

Methanogens living on and within rumen ciliate protozoa may be responsible for
up to 37% of the rumen methane emissions. In the absence of protozoa,
rumen methane emissions are reduced by an average of 13% but this
varies with diet. Decreased methane emissions from the protozoa-free rumen may
be a consequence of: (1) reduced ruminal dry matter
digestion; (2) a decreased methanogen population;
(3) an altered pattern of volatile fatty acid production
and hydrogen availability; or (4) increased partial
pressure of oxygen in the rumen. The decline in methanogenesis associated with
removal of protozoa is greatest on high concentrate diets and this is in
keeping with protozoa being relatively more important sources of hydrogen on
starch diets, because many starch-fermenting bacteria do not produce H2. Because protozoa also decrease the supply of protein
available to the host animal, their elimination offers benefits in both
decreasing greenhouse gas emissions and potentially increasing livestock
production. Strategies for eliminating protozoa are reviewed. None of the
available techniques is considered practical for commercial application and
this should be addressed.
Prediction of methane emissions from beef cattle in tropical production systems
Authors: McCrabb G. J. , Hunter R. A.
Published: September 2002

The northern beef cattle herd accounts for more than half of Australia’s
beef cattle population, and is a major source of anthropogenic methane
emissions for Australia. National Greenhouse Gas Inventory predictions of
methane output from Australian beef cattle are based on a predictive equation
developed for British breeds of sheep and cattle offered temperate
forage-based diets. However, tropical forage diets offered to cattle in
northern Australia differ markedly from temperate forage-based diets used in
the United Kingdom to develop the predictive equations. In this paper we
review recent respiration chamber measurements of daily methane production for
Brahman cattle offered a tropical forage or high grain diet, and compare them
with values predicted using methodologies of the Australian National
Greenhouse Gas Inventory Committee and the Intergovernmental Panel on Climate
Change. We conclude that a reliable inventory of methane emissions for cattle
in northern Australia can only be achieved after a wider range of tropical
forage species has been investigated. Some opportunities for reducing methane
emissions of beef cattle by dietary manipulation are discussed.
Ecotypic variation between and within two populations of Trifolium tomentosum (woolly clover) from Syria and Western Australia: its success as a colonising species
Authors: Bennett Sarita Jane
Published: September 2002

Ecotypic variation was studied between and within populations of
Trifolium tomentosum (woolly clover) using seed that was
collected from 2 semi-arid environments: Tel Hadya, Syria, and Pingrup,
Western Australia. The seed was collected from 64 subplots within a
40-m2 grid at each site and the material was grown at
the University of Western Australia Field Station at Shenton Park, Perth.
Fifteen morphological characters were scored and were analysed using analysis
of variance, principal components analysis, and discriminant function
analysis. Material from the 2 sites was separated using multivariate analysis,
with the seed from Tel Hadya containing more within-site variation. It is
suggested that the lack of within-site variation observed at Pingrup is the
result of a number of factors: a limited amount of genetic diversity being
present in the original introduced material, a preference of
T. tomentosum for alkaline soils rather than the acid
soils predominantly occurring in Western Australia, the harsh selection
pressures present in a semi-arid environment, and a limited time for genotypes
to adapt to specific micro-niches within each environment. The results are
used to contribute to our understanding of the success of colonising species
in semi-arid environments.
The effect of growing sites on grain quality of oats and pasting properties of oatmeals
Authors: Zhou M. X. , Glennie-Holmes M. , Roberts G. L. , Robards K. , Helliwell S.
Published: September 2002

To assess the effect of growing sites on oat quality, 8 varieties were grown
at 13 sites in New South Wales, Australia, in the 1995–96 and
1996–97 growing seasons. Grain milling quality, chemical composition,
and pasting properties differed significantly between sites and were related
to both variety and growing conditions. Varieties were the main determining
factor of kernel size, kernel weight, and oil concentration, whereas growing
conditions accounted for most of the variance in groat percentage and protein
concentration. Breeding and selection offer opportunities for improving oat
quality, and selecting suitable sites to grow oats could greatly improve
milling quality and pasting properties, and ensure appropriate chemical
composition.
Current issues in trace element nutrition of grazing livestock in Australia and New Zealand
Authors: Masters D. G. , Judson G. J. , White C. L. , Lee J. , Grace N. D.
Published: September 2002

Improving trace element nutrition of grazing animals, in a way that is cost
effective and that meets consumer perceptions and preferences, is a continuing
challenge. This review focuses on research over the past 10 years, addressing
issues and perspectives on the roles, risks of inadequacy, and supplementary
remedies of key trace elements, both essential and deleterious, which have an
impact on the productivity and product quality of grazing livestock throughout
Australia and New Zealand. The emphasis is on copper (Cu), cobalt (Co), iodine
(I), selenium (Se), and, to a lesser extent, zinc (Zn) — the trace
elements most frequently found to be deficient in parts of Australia and New
Zealand. Research continues to elucidate new roles for trace elements in the
animal, and as this leads to a better understanding of requirements,
diagnostic criteria and supplementation strategies need re-evaluation. Newer
perspectives on marginal deficiency for Cu, I, Se, and Zn are given and issues
for risk management discussed. Advances in sustained delivery of trace
elements such as Co (as vitamin B12), I, and Se are
reported. The diagnosis and management of marginal Cu deficiency continue to
be difficult, especially in New Zealand where recent work has shown that
dietary antagonists [iron (Fe), molybdenum (Mo), and sulfur (S)] may
impair Cu absorption at lower intakes than previously thought. There is still
a dearth of scientific data on the advantages of using so-called organic trace
element supplements (metals complexed or chelated with amino acids or
peptides). Nevertheless their usage continues to increase. There is increasing
evidence that trace elements influence the pathophysiology arising from the
ingestion of toxins. This review summarises recent work on the role of Co in
annual ryegrass toxicity; Cu, Se, and Zn in lupinosis; Cu and alkaloid
toxicity; Zn and facial eczema; and Co and white liver disease. Trace elements
are required to support immune function (e.g. as imposed parasite infection)
and marginal deficiencies may be exacerbated by an immunological challenge.
The roles of Cu, Co, Mo, Se, and, to a lesser extent, chromium and Zn have
attracted attention and under conditions of stress there may be an additional
need for these elements. Diversification in farming has led to the
introduction of species such as deer (Cervus), alpacas
(Camilids), emus, and ostriches
(Ratites) and the paucity of information on trace
element requirements for these species, and also for horses, indicates the
need for further work. The effect of supplementation on trace element
composition of meat, milk, and wool is also reviewed, both in terms of product
characteristics and human health. Of the deleterious elements, cadmium has
attracted the most interest and concern because of its introduction into the
pastoral system from phosphate-based fertilisers.
Environmental and genetic variation for grain yield and barley malting quality attributes
Authors: Lu M. Q. , O'Brien L. , Stuart I. M.
Published: September 2002

Genotype, environment, and genotype × environment interaction effects
for malting quality attributes and grain yield were investigated using
breeding lines from the F2, F3, and F4 generations and the parental varieties of 4
barley crosses. There were significant differences between the parental
varieties for all attributes studied. Both malting quality and grain yield
exhibited a wide range among progenies in all generations. While performance
of the parental varieties and progeny for malting quality and grain yield were
greatly influenced by environment, performance in one environment was
predictive of that in other environments. Only for grain protein content was
there evidence of crossover G × E interaction.
Heritability was generally higher for F3 to F4 than for F2 to F3 for all malting quality attributes. F3 on F2 regression per cent
heritability estimates for protein content, potential malt extract and grain
weight were all highly significant with values generally medium in magnitude.
Genetic gain was obtained from selection in both the F2
and F3 generations. Heritability and genetic gain
varied from cross to cross for diastatic power. Progress from selection for
the other quality attributes attests to the potential value of NIT (near
infrared transmittance) spectroscopy for predicting potential malting quality.
Heritability for F2 to F3 for
grain yield was not significant in any cross, indicating selection for yield
on the basis of individual F2 plant yield was
ineffective. Heritability for grain yield from F3 to F4 was highly significant and medium in magnitude for 3
of the 4 crosses.
The results of this study indicate that good genetic gain could be expected
from early generation selection for potential malting quality using NIT
spectroscopy and for grain yield using F3 progeny
testing.
The in vitro inhibition of Phytophthora clandestina by some rhizobia and the possible role of Rhizobium trifolii in biological control of Phytophthora root rot of subterranean clover
Authors: Simpfendorfer S. , Harden T. J. , Murray G. M.
Published: September 2002

The interaction between 29 isolates of Rhizobium and the
in vitro growth of 3 strains of
Phytophthora clandestina was investigated to determine
the potential of these bacteria as biological control agents against root rot
of subterranean clover (Trifolium subterraneum L.). The
biological control activity of Rhizobium on the severity
of root disease in seedlings was also investigated under glasshouse
conditions. Thirteen of the 29 Rhizobium isolates caused
significant reductions in the hyphal growth of the 3
P. clandestina isolates examined. Inoculation of
seedlings with Rhizobium trifolii reduced the severity
of root disease by 14–58% with corresponding increases in dry
matter production of 20–73%. These results indicate that
Rhizobium species have potential as biological control
agents against the root rot of T. subterraneum seedlings
caused by P. clandestina.
Germination of Four Species of Native Western Australian Plants using Plant-derived Smoke
Authors: Tieu Anle , Plummer Julie A. , Dixon Kingsley A. , Sivasithamparam K. , Sieler Ingrid M.
Published: September 2002

Plant-derived smoke was investigated in this study as a pre-germination
treatment for seed of four native plant species from south-western Western
Australia. Many Australian native species demonstrate low germination
responses using conventional nursery propagation methods. Smoke water,
prepared from burning 6 kg of fresh and dry foliage of
Eucalyptus, Adenanthos and
Banksia species and bubbling the smoke through water (20
L) for 1 h was found to substantially improve germination of
Stylidium affine Sonder.,
Stylidium brunonianum Benth. (Stylidiaceae) and
Conostylis setigera R.Br. (Haemodoraceae), whereas
Actinotus leucocephalus Benth. (Apiaceae) retained a
high level of dormancy despite prolonged exposure to smoke water. Diluted and
full strength smoke water was found to significantly increase germination of
S. brunonianum, C. setigera and
A. leucocephalus over water alone. Seeds retained the
smoke cue after imbibition in smoke water, whether incubated continuously with
smoke water or imbibed in smoke water and dehydrated or dehydrated, stored for
3 weeks. Species varied in their germination response to changes in imbibing
time in diluted smoke water. A. leucocephalus required
longer periods of smoke water imbibition (24-48 h) to elevate germination
irrespective of the three treatments following imbibition. All imbibition
periods were effective in enhancing germinability of
S. affine and S. brunonianum
regardless of subsequent treatments. However, S. affine
required shorter imbibition exposure times (3Œ12 h) for optimal
germination for the dehydrated and stored treated seeds.
C. setigera required shorter exposure to smoke water of
3 and 6 h, when germinated immediately, whereas longer exposure to smoke water
was necessary for effective germination in dehydrated (24-48 h) and dehydrated
and stored (48 h) treated seeds.
The site of action of smoke water in seed was investigated and found to reside
in part in the seed coat in S. affine, and the embryo
and/or endosperm in A. leucocephalus. The smoke
chemical(s) overcame multiple dormancy mechanisms in
S. affine and A. leucocephalus
whereas gibberellic acid (GA) and zeatin were unable to break dormancy.
Mechanism of dormancy relief by smoke water was not the same as GA and zeatin.
These data indicate that there are good prospects using imbibition with smoke
water as a pre-treatment for seeds in the horticulture and land restoration
activities.
Seasonal Variation in Buried Germinable Seed Banks of Grass Species in an Urban Eucalypt Forest Reserve
Authors: Odgers B. M.
Published: September 2002

Grass species in the buried germinable seed banks of selected forest, mown and
road-bank sites in the Mt Coot-tha Reserve, south-eastern Queensland were
quantified for five consecutive seasons to determine seasonal patterns in the
seed banks, and differences in seasonal patterns between native and exotic
grass species, and between grasses in natural and disturbed forest areas. Ten
types of seed banks were identified. While native and exotic species had
similar seed banks most native grass species had transient seed banks whereas
most exotic grass species had persistent seed banks.
Cross Fertility of Australian Accessions of Wild Mungbean (Vigna radiata ssp. sublobata) with Green Gram (V. radiata ssp. radiata) and Black Gram (V. mungo)
Authors: Lambrides C. J. , James A. T. , Lawn R. J. , Williams R. W.
Published: September 2002

The position of Australian accessions of wild mungbean
(Vigna radiata ssp. sublobata) in
the Asiatic Vigna gene pool was examined by assessing
their cross fertility with the green gram cultigen
(Vigna radiata ssp. radiata) and
black gram (Vigna mungo). No difficulties were
encountered in obtaining F 1 and backcross seed in
crosses with green gram. The hybrid progenies were vegetatively vigorous and
fully fertile. Inheritance of traits appeared normal and, where direct
comparisons were possible, consistent with crosses within the cultigen.
Inheritance of a new seed mottling gene is presented and several linked traits
were found. Crosses with black gram proved difficult to achieve, and the
resulting hybrid seed showed varying degrees of viability. Individuals that
germinated were weak, and if they survived to flower, possessed low pollen
fertility and poor seed set. It was concluded that indigenous Australian
accessions of wild mungbean belong to the primary gene pool of
Vigna radiata.
Effectiveness of Invertebrate and Vertebrate Pollinators and the Influence of Pollen Limitation and Inflorescence Position on Follicle Production of Banksia aemula (Family Proteaceae)
Authors: Dalgleish Elizabeth
Published: September 2002

Follicle development of Banksia aemula (R.Brown 1810)
was studied in northern New South Wales, Australia, after exposure of
inflorescences to different combinations of pollinator type and pollen
quantity. When inflorescences within plants were exposed to all pollinators
and provided with additional cross-pollen, follicle development was
increased, suggesting that B. aemula was pollen-limited.
The addition of cross-pollen did not increase follicle development when
inflorescences within plants were exposed to invertebrate pollination only.
Nor did exclusion of vertebrates significantly reduce follicle development of
plants relative to that of others which were exposed to all pollinators. The
vegetation surrounding plants influenced the follicle development of
inflorescences, and inflorescences in peripheral positions had more follicles
than inflorescences that were internal.
Wind Dispersal of the Vagant Lichen Chondropsis semiviridis in Semi-arid Eastern Australia
Authors: Eldridge D. J. , Leys J. F.
Published: September 2002

A field-based wind tunnel was used to assess threshold wind velocities
required to initiate movement of the vagant lichen
Chondropsis semiviridis (F.Muell. ex Nyl.) Nyl. in a
semi-arid eastern Australian woodland. Threshold wind velocities were lowest
on bare surfaces (21 km h-1) and highest on surfaces
covered with the needle-like litter of
Casuarina cristata Miq. trees (58 km
h-1). Examination of wind speed data suggests that
threshold wind velocities for movement on litter-covered surfaces occur about
1% of the time in summer. The extensive litter cover in the groves, and
the tendency of C. semiviridis to firmly attach to this
litter, probably explains the concentration of
C. semiviridis in the groves and the low rates of
migration and emigration during most years. It is hypothesised that migration
of C. semiviridis between timbered groves would only
occur during extreme droughts when pasture and litter cover are sparse.
Physiological Characterisation of Salt-resistant Rice (Oryza sativa) Somaclones
Authors: Lutts Stanley , Bouharmont Jules , Kinet Jean-Marie
Published: September 2002

The progenies of 90 R0 plants regenerated from mature
embryo-derived rice (Oryza sativa L.) calli obtained
from two cultivars (I Kong Pao, salt-sensitive and Aiwu, moderately resistant)
exposed to NaCl stress at various steps of in vitro
culture, were screened for their salinity resistance in nutritive solution.
Sixteen R1 families presented a higher survival rate in
stress conditions than their corresponding initial cultivar and several of
them exhibited an improvement in the mean number of spikelets per panicle and
total grain weight produced per stressed plant. In four cases, the better
behaviour of the somaclonal family could be related to physiological
modifications such as a higher K+
:Na+ discrimination, preferential
Na+ accumulation in the oldest leaves, lower
decrease in cell membrane stability or higher tissue tolerance to internal
Na+ accumulation. In some cases, these
physiological properties were transmitted to R2
progenies. Heritabilities of yield-related parameters were quantified in
control and stress conditions. The relationships between these parameters and
the physiological behaviour of stressed material are discussed in relation to
the effectiveness of in vitro culture techniques for the
selection of salt-resistant plants in rice compared with a simple mass
selection.