bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen cycling in semi-arid Mediterranean zones: removal and return of nitrogen to pastures by grazing sheep
Authors: White P. F. , Treacher T. T. , Termanini A.
Published: August 2004

The intake of nitrogen and its removal, return, and partition between urine,
faeces, and milk was measured over 5 months in Awassi ewes grazing medic
pasture or barley. Total faeces and urine were collected in bags carried by
the ewes for 5-day collection periods at monthly intervals. Bags were changed
in the morning and evening so that excreta produced in the field or in the
yards at night were collected separately. Nitrogen was partitioned between the
urine and faeces on the basis of the N: ADF ratio of samples of faeces taken
directly from the rectum of the animal when the bags were changed. Outputs of
excreta and N were very similar in the field and at night in the yard. When N
output in the milk was included, 20% more N was removed from the field
than was returned. The partitioning of N output between urine and faeces
changed markedly during the season and corresponded with changes in the
quality of the herbage. Fifty per cent and 65% of the removal of N in
faeces and urine, respectively, occurred in the first 2 months of the
experiment.
Defoliation frequency and the response by white clover to increasing phosphorus supply 1. Leaf dry matter yield and plant morphology responses
Authors: Singh D. K. , Sale P. W. G.
Published: August 2004

A glasshouse experiment was carried out to determine how an increasing P
supply influences the growth and survival of white clover plants subjected to
a range of defoliation frequencies. Treatments involved the factorial
combination of P application rate (0, 30, 90, and 180 mg/pot) to a
P-deficient Krasnozem soil and defoliation frequency (1, 2, or 4 defoliations
over 36 days). The survival of P-deficient plants was threatened by the most
frequent defoliation; their leaf area declined owing to a reduction in leaf
number and individual leaf size with each successive defoliation. Increasing
the P supply to 180 mg/pot reversed this downward trend as the high P
plants were able to maintain leaf area by increasing leaf size and number.
Increasing the frequency from 1 to 4 defoliations over the 36 days also
changed the form of the leaf dry matter response to added P, from an
asymptotic to a linear response. The P requirement of white clover for maximum
leaf yield therefore increased under frequent defoliation. This effect was
also apparent for a range of morphological measurements including stolon
elongation rate, leaf area, root mass, leaf number, and stolon number, where
the magnitude of the P response was consistently greater for frequently
defoliated plants. Exceptions included stolon mass, which responded more to P
addition under infrequent defoliation.
Short-term changes in whole body and skin sulfur amino acid metabolism of sheep in response to supplementary cysteine
Authors: Harris P. M. , Sinclair B. R. , Treloar B. P. , Lee J.
Published: August 2004

Two groups of five 40-kg, 12–15-month-old, cryptorchid Romney sheep were
housed indoors in metabolism crates at 18°C and fed lucerne
(Medicago sativa) chaff at above-maintenance intakes. At
2-weekly intervals, 1 sheep from each group underwent surgery to insert
arteriovenous catheters across the abdominal skin patch. One group of sheep
was continuously infused with 2 g/day of cysteine (Cys) in sterile
physiological saline via the jugular, and the other group received an infusion
of saline only. After 5 days of infusion, measurements were made in each sheep
comparing the whole body metabolism of Cys and skin metabolism of Cys and
methionine (Met). The groups were then reversed in treatment and 2 days later
the same measurements were repeated followed by a comparison of whole body and
skin Met metabolism.
There was a trend (P = 0·07) for arterial
Cys concentration to be increased in the Cys-supplemented sheep but there were
no significant treatment differences in glutathione or Met concentration. The
irreversible loss rate (ILR) of Cys was increased significantly
(P < 0·01) in the Cys-supplemented sheep.
Proportional oxidation of Cys was very significantly (P
< 0·001) increased across the Cys-supplemented sheep. Met ILR was
not related to the Cys ILR. Blood flow to the skin was significantly reduced
in the Cys-supplemented group, resulting in an unchanged flux of Cys past the
skin. There was a trend (P = 0·06) for
both net and total uptake of Cys to be increased in the Cys-supplemented
sheep. There was no net efflux of oxidation products of Cys or Met in the
venous drainage of either treatment group.
The effect of short-term supplementation with Cys directly into the peripheral
circulation of the sheep was an increase in whole body catabolism of both Cys
and Met that would reduce the efficacy of the supplement. Of the 2 g/day
of additional Cys supplied, about 25–30% was able to be taken up
by the skin and used for protein synthesis. The skin does not export oxidation
products of either Cys or Met, and so all the enhanced skin uptake of Cys in
response to supplementation is directed towards protein synthesis, but this is
probably predominantly used to change the expression of individual proteins
rather than to enhance total protein synthesis.
Grain growth and malting quality of barley. 2. Effects of temperature regime before heat stress
Authors: Savin Roxana , Stone Peter J. , Nicolas Marc E. , Wardlaw Ian F.
Published: August 2004

Short periods of very high maximum temperature (>35°C) during grain
filling appear to reduce grain yield and quality in barley. Tolerance of grain
yield and quality to heat stress may be increased when acclimation to high
temperature occurs. Two experiments were performed to test the hypothesis that
a gradual (or stepped) increase to very high temperature reduces the impact of
that stress on grain growth and quality of barley, compared with a sudden
increase over the same temperature range. Plants experiencing either a sudden
or a gradual increase did not exhibit any differences in grain weight or
malting quality, but increasing the temperature in 2 steps (so that plants
were exposed to 30 or 34°C for 2 h before a 40°C heat stress) appeared
to have produced acclimation, since the reduction in grain weight under the
2-step treatment was about half that of either a sudden or gradual increase in
temperature.
Heat stress altered grain composition in various ways. The reduction in final
grain weight was strongly and linearly related to the reduction in starch
content. Grain β-glucan was 4·5 ± 0·5% across
treatments and experiments and was significantly reduced in the glasshouse but
not in the phytotron experiment. However, β-glucan degradation was similar
between treatments in both experiments. Grain nitrogen concentration was very
high and similar between treatments. Consequently, diastatic power was high
and there was a trend towards a reduction under heat stress. Free amino
nitrogen was higher under heat stress, indicating a higher protein
modification than in the controls. Malt extract was significantly reduced by
heat stress in the glasshouse experiment.
Effect of nitrogen fertiliser placement on grain protein concentration of wheat under different water regimes
Authors: Lotfollahi M. , Alston A. M. , McDonald G. K.
Published: August 2004

Two experiments were conducted in pots 105 cm deep and 11 cm in diameter to
determine the effects of subsoil nitrogen (N) on grain yield and grain protein
concentration (GPC) of wheat (Triticum aestivum L. cv.
Molineux). In both experiments, KNO3 was applied in
solution at different times and depths in the profile. In the first
experiment, in which a sandy soil low in available N was used, application of
150 mg N at 60 cm, 2 weeks after anthesis, significantly increased grain yield
and GPC. The N was taken up gradually by the plant after N was applied. Adding
N to the subsoil increased root growth and this resulted in increased water
use and water use efficiency. Although there was an increase in the rate of N
uptake by the roots, the main factor that influenced the utilisation of
subsoil N was the root length density. In the second experiment, the effects
of depth and time of N application, and of a reduction in post-anthesis water
supply, were determined. A more fertile soil was used than the one in the
first experiment. There were 5 KNO3 treatments: nil N;
150 mg N applied to the topsoil at sowing; 75 mg N to the topsoil and 75 mg N
to the subsoil (60 cm depth) at sowing; 150 mg N to the subsoil at sowing; 75
mg N to the topsoil at sowing and 75 mg N to the subsoil 1 week after
anthesis. The effect of post-anthesis water stress was assessed by allowing
the topsoil to dry and then supplying half the amount of water used by the
well-watered control treatment at 60 cm in half of the pots. Adding N
increased yield and GPC but there was no significant difference in yield and
GPC between the different N treatments. When N was applied to the topsoil
only, most of it was used by the wheat plants or leached to the subsoil by
anthesis; post-anthesis uptake of N depended on the amount of N in the
subsoil. Adding N, irrespective of the depth of placement or time of
application, increased water use and water use efficiency. In both
experiments, increasing the availability of N in the soil after anthesis
reduced the amount of N that was remobilised from the roots and stem to the
grain. The recovery of applied N in both experiments was high (about
80%). These experiments have shown that N available in the subsoil
after anthesis can be used very efficiently and can contribute to both grain
yield and GPC. A critical factor in the efficient use of this N appears to be
root length density in the subsoil.
Effect of coal mine pit water on the productivity of cattle. II. Effect of increasing concentrations of pit water on feed intake and health
Authors: Harper G. S. , King T. J. , Hill B. D. , Harper C. M. L. , Hunter R. A.
Published: August 2004

The effect of drinking high mineral content coal mine pit water on the health
and growth of yearling tropically adapted steers was investigated. Steers
consumed town water (~ 30 mg sulfate/L) or dilutions of pit water, which
at the highest concentration contained (mg/L) 4000 sulfate as well as 3082
chloride, 328 calcium, 562 magnesium, 2600 sodium, and other minerals at
lesser concentrations (total dissolved solids, 8600 mg/L). The growth and
performance of the steers were measured as average daily weight gain, dry
matter intake, faecal dry matter content, and water intake. Health was
assessed using haematological indices (packed cell volume, haemoglobin, and
others) and on randomly selected animals, by complete
post mortem haematological and biochemical analysis.
Consumption of diluted pit water of up to 2000 mg sulfate/L, if introduced
gradually, did not result in a reduction in dry matter or water intake.
Significant interactions (P < 0·05) occurred
between rate of introduction and plane of nutrition in affecting weight gain,
whereby weight gains on pit water were marginally greater when treatment was
introduced abruptly. Plane of nutrition was the main effect in determination
of packed cell volumes, where low plane of nutrition led to higher values.
Interactions of time on pit water treatment with rate of introduction or
nutrition in affecting packed cell volume were statistically significant
(P ≤ 0·006) but small in magnitude
(1–2%), and hence unlikely to be biologically significant since
averages remained within the normal range for the age group. Pit water
treatment did not compromise the animals’ health at 2000 mg
sulfate/L, as assessed by visual veterinary and histopathological
examinations of tissues taken at autopsy. When the concentration of pit water
was increased to 4000 mg sulfate/L, dry matter intake was depressed by
14% and water intake was decreased by up to 40%, increasing
slightly with longer time on treatment. Under the conditions of this
experiment, beef steers can drink coal mine pit water containing up to 2000 mg
sulfate/L (4000–6000 mg/L of total dissolved solids) without
suffering ill effects, provided that it is introduced gradually. The study
therefore provides evidence that the recommendation of 1000 mg sulfate/L
as the maximum concentration in livestock drinking water may be too
conservative for steers if favourable conditions exist.
The concentration of creatine and creatine phosphate in sow colostrum and milk throughout lactation and weaning
Authors: Kennaugh Linda M. , Arthur Peter G. , Hartmann Peter E.
Published: August 2004

The concentrations of creatine and creatine phosphate were determined by
enzymatic analysis of mammary secretions from a total of 63 sows from
pre-farrowing (PF), during farrowing, and on Days 1, 2, 3, 4, 5, 7, 11, 18,
and 28 (at weaning) of lactation. Three sows were sampled on all days and on
Days 1, 2, 3, 4, and 5 post weaning. Samples were collected from an additional
5 sows on the sampling days PF to Day 28 of lactation. The concentration of
creatine remained constant at 1·4±0·02 mM (mean
±s.e.m.) prior to farrowing and throughout lactation. The concentration
of creatine phosphate was 0·41±0·05 mM prior to farrowing
until Day 2 of lactation. The concentration of creatine phosphate then
increased gradually from Day 3 to reach a peak at 1·1±
0·05 mM by Day 7 and then remained unchanged throughout lactation. The
concentrations of creatine and creatine phosphate decreased 30-42 h post
weaning, and by 118 h post weaning both creatine and creatine phosphate were
undetectable in milk samples. The within-sow variation in the concentration of
creatine and creatine phosphate in colostrum before farrowing was small (CVs
2-9% and 6-9%, respectively). However, during farrowing,
throughout lactation, and post weaning, the variations in the concentration of
creatine and creatine phosphate were much larger (CVs 19-27% and
25-80%, respectively). In contrast, the between-sow variations in the
concentration of creatine and creatine phosphate in mammary secretion
collected at all of these stages of the lactation cycle were large (CVs
15-41% and 19-57%). It was concluded that concentrations of
creatine and creatine phosphate may reflect mammary gland metabolic activity
and could be involved in the development of the piglet during the suckling
period.
Grain yield and water use efficiency of early maturing wheat in low rainfall Mediterranean environments
Authors: Regan K. L. , Siddique K. H. M. , Tennant D. , Abrecht D. G.
Published: August 2004

Wheat cultivars with very early maturities appropriate for late sowings in
low-rainfall (<325 mm) short-season environments are currently unavailable
to wheat growers in the eastern margin of the cropping region of Western
Australia. A demonstration that very early-maturing genotypes can out-perform
current commercial cultivars would open new opportunities for breeding
programs to select very early-maturing, high- and stable-yielding cultivars
for these environments. Six field experiments were conducted over 4 seasons at
2 low-rainfall sites in Western Australia to investigate crop growth, grain
yield, and water use efficiency of very early-maturing genotypes compared with
current commercial cultivars when sown after 1 June.
Very early-maturing genotypes reached anthesis up to 24 days (328 degree-days)
earlier than the current cultivars, produced less leaves, had similar yields
and dry matter, and maintained high water use efficiencies. On average across
seasons and locations the very early-maturing genotypes
(W87–022–511, W87–114–549, W87–410–509)
yielded more than the later maturing cultivars Gamenya and Spear (190
v. 160 g/m2) but they were
similar to the early-maturing commercial cultivars Kulin and Wilgoyne (191
g/m2). Very early-maturing genotypes generally had a
higher harvest index and produced fewer spikelets, but heavier and more
grains, than Kulin and Wilgoyne.
There were only small differences in total water use between very
early-maturing genotypes and commercial cultivars; however, very
early-maturing genotypes used less water in the pre-anthesis period and more
water in the post-anthesis period than the later maturing genotypes, and
hence, experienced less water deficit during the grain-filling period. This
study indicates that there is a role for very early-maturing genotypes in
low-rainfall short-season environments, when the first autumn rains arrive
late (after 1 June).
The effectiveness of a range of insecticides against western flower thrips (Frankliniella occidentalis) (Thysanoptera : Thripidae) on cut flowers
Authors: Seaton K. A. , Cook D. F. , Hardie D. C.
Published: August 2004

Three insecticide spray trials were conducted on field calendulas and
chrysanthemums to test the effectiveness of 10 insecticides against western
flower thrips (Frankliniella occidentalis). The efficacy
of each insecticide was assessed between 1 and 11 days post-spraying.
Methamidophos was the most effective insecticide, followed to a lesser extent
by dichlorvos, ¸Λ -cyhalothrin, fluvalinate, and maldison. Apart from
methamidophos, insecticides were generally less than 50% effective at 3
or more days post-spraying. In a separate trial, 5 insecticides were applied
as drenches to the soil of pots in which carnations infested with
F. occidentalis were grown. The pots were placed in
thrips containment cages and adult thrips emerging from the soil were caught
on sticky traps. Parathion-methyl and chlorpyrifos reduced thrips emergence
from soil by 90–95%.
A comparison of the fatty acid composition of triacylglycerols in adipose tissue from Limousin and Jersey cattle
Authors: Malau-Aduli A. E. O. , Siebert B. D. , Bottema C. D. K. , Pitchford W. S.
Published: August 2004

The fatty acid composition of the triacylglycerol fraction of shoulder fat
from Limousin and Jersey yearling heifers, yearling steers, and non-lactating
cows was investigated.
Significant breed differences in the degree of fatty acid saturation were
apparent between Jersey and Limousin cows, but were not observed in the
yearlings. Jersey cows had less saturated fatty acids than the Limousin.
Jersey cows showed an increased percentage of monounsaturated fatty acids
compared with the Jersey yearlings. In contrast, the level of monounsaturated
fatty acids in the Limousin cows was the same as in the Limousin yearlings.
The calculated indices of enzyme activities also differed between the breeds.
Jersey cows had higher indices of Δ9-desaturase and elongase activities
than Limousin. This was also reflected by differences in the ratios of total
unsaturated and polyunsaturated to saturated fatty acids.
Breed differences were also observed in the triacylglycerol fatty acid chain
length. In this case, however, yearlings showed significant breed differences
that were not detected in the cows. Limousin yearlings had more long chain
fatty acids (C16 and C18) than the Jersey yearlings. Limousin yearlings also
had a higher elongase activity index than their Jersey counterparts. Thus,
breed and age affect the fatty acid composition in these cattle.
The effect of altering the dietary arginine to lysine ratio on the breast meat yield of broiler chickens at moderate and high temperatures
Authors: Gorman I. , Balnave D. , Brake J.
Published: August 2004

In 4 experiments broilers were housed at moderate or high temperatures and fed
diets containing arginine : lysine (arg : lys) ratios ranging from 1·01
to 1·45 from 3 weeks of age until reaching a processing weight of
2·2 kg. The effects of temperature and arg : lys ratio on breast meat
yield were determined. In the first 3 experiments, increasing the arg : lys
ratio increased breast meat yield at moderate temperatures and reduced breast
meat yield at high temperatures. Hypothesised response curves are presented to
explain the different responses in breast meat yield to arg : lys ratio at
moderate and high temperatures. Expt 4 was designed to test the validity of
the hypothesised response curves. The pattern of the responses obtained from
this experiment supports the hypothesis.
Expression of resistance by tetraploid and diploid lucerne genotypes to Phytophthora medicaginis is not influenced by inoculum level or by temperature
Authors: Irwin J. A. G. , Maxwell D. P. , Smith R. R.
Published: August 2004

Phytophthora-resistant lucerne cultivars do not always perform well under
conditions of high disease pressure in the field. To determine whether
resistance expression remains stable under different infection intensities,
tetraploid and diploid lucerne genotypes, genotypically defined for their
reactions to Phytophthora medicaginis, were clonally
propagated, and the influence of different reproducible inoculum levels
(0·5 and 5·0 g dry weight mycelium/kg dry weight potting
mix), the period of exposure to these levels (10–60 days), and
temperature (16/22°C and 24/30°C) on disease expression was
determined in controlled environments. Generally, expression of resistance by
resistant genotypes, remained stable under these conditions. Biotic (e.g.
Aphanomyces eutiches) or abiotic factors other than
P. medicaginis may be responsible for the poorer than
expected performance under fiield conditions in some instances, or the
percentage of resistant plants in some cultivars currently classified as
resistant is insufficient to provide buffering against productivity reductions
under severe epidemics. Further research is needed to clarify the situation.
Estimation of responses of yield and grain protein concentration of malting barley to nitrogen fertiliser using plant nitrogen uptake
Authors: Birch C. J. , Fukai S. , Broad I. J.
Published: August 2004

The effect of nitrogen application on the grain yield and grain protein
concentration of barley was studied in 13 field trials covering a wide range
of soil N conditions over 4 years at locations in south-eastern Queensland.
The main objectives of the study were to quantify the response of barley to N
application rate over a range of environmental conditions, and to explain the
response in terms of soil mineral N, total N uptake, and N distribution in the
plants.
Barley made efficient use of N (60 kg grain/kg N) until grain yield
reached 90% of maximum yield. Grain protein concentration did not
increase to levels unacceptable for malting purposes until grain yield
exceeded 85–90% of maximum yield. Nitrogen harvest index was
generally high (above 0·75), and did not decrease until the total N
supply exceeded that necessary for maximum grain yield. Rates of application
of N for malting barley should be determined on the basis of soil analysis
(nitrate-N) to 1 m depth and 90% of expected maximum grain yield,
assuming that 17 kg N is taken up per tonne of grain produced. It can further
be assumed that the crop makes full use of the nitrate N to 1 m present at
planting, provided the soil is moist to 1 m.
A framework relating grain yield to total N uptake, N harvest index, and grain
N concentration is presented. Further, total N uptake of fertilised barley is
related to N uptake without fertiliser, fertiliser application rate, and
apparent N recovery. The findings reported here will be useful in the
development of barley simulation models and decision support packages that can
be used to aid N management.
An Australian temperate pastures database
Authors: Pearson C. J. , Brown R. , Collins W. J. , Archer K. A. , Wood M. S. , Petersen C. , Bootle B.
Published: August 2004

A census of pasture types and their composition and attributes (e.g. purpose
and carrying capacity) was carried out throughout southern Australia from June
to October 1994. This paper describes the survey process and subsequent
creation of an Australian temperate pastures database. Data were created for
562 local government areas (LGAs) from ‘desk estimates’ by trained
agriculturists. They identified about 2500 pasture types, which were grouped
into 120 standardised pasture categories.
Some findings from the data are identified, namely the high relative
importance on an area basis of unimproved native pastures, the importance of
weedy species (e.g. Vulpia), and the marked decline with
increasing rainfall in importance of annual medics compared with subterranean
clover. This paper provides examples of the data and their use for assessment
of the regional economic impact of increases in productivity of pasture
species.
Effect of temperature and dietary sodium bicarbonate supplementation on the mineral excretion of broilers
Authors: Gorman I. , Balnave D. , Roberts J. R.
Published: August 2004

A non-surgical technique was developed for the collection of urine samples
free from faecal contamination. This technique was used with growing broilers
to study the effects of ambient temperature and dietary sodium bicarbonate
(NaHCO3) supplementation on the urinary excretion of
mineral ions 1·5–2·0 h after feeding. High ambient
temperatures resulted in increases in the absolute retentions of sodium,
potassium, calcium, magnesium, phosphorus, and sulfur. The lack of any
temperature effect on the urinary excretion of the non-monovalent ions
indicated that the changes in retentions of these ions were due to changes in
absorption. The increase in potassium retention was related to a decrease in
urinary excretion, as would be expected for an ion regulated predominantly by
the kidneys. However, no effect of temperature was observed on the urinary
excretion of sodium. Sodium bicarbonate supplementation resulted in an
increase in both the absolute retention and urinary excretion of sodium. Other
minerals were unaffected by NaHCO3 supplementation other
than for a marginally significant (P =
0·05) increase in the absolute retention of sulfur. In order to
minimise faecal contamination of the urine samples, birds were fasted for 16 h
prior to feeding with experimental diets. Possible problems with tissue
catabolism were minimised by supplying birds with a glucose–casein
solution during the fasting period.
Detection and differentiation of phytoplasmas in Australia
Authors: Davis R. I. , Schneider B. , Gibb K. S.
Published: August 2004

In a polymerase chain reaction (PCR) diagnostic test, phytoplasma (formerly
known as plant-pathogenic mycoplasma-like organism or MLO) ribosomal DNA was
detected in total DNA extracts prepared from 56 out of 63 plants collected
from geographically diverse locations across Australia. The list of
phytoplasma hosts consisted of 38 different species in 16 different families.
Restriction site analysis of the PCR-amplified DNA accessions was used to
divide the phytoplasmas into 2 groups. The majority of the tomato big bud
group and sweet potato little leaf group phytoplasmas were closely related to
a phytoplasma originally obtained from Crotalaria in
Thailand, which is a member of the faba bean phyllody strain cluster. In
contrast, phytoplasmas associated with Australian grapevine yellows and papaya
dieback were most similar to members of the aster yellows strain cluster.
Twelve phytoplasmas were compared by Southern blot hybridisation with DNA
cloned from the sweet potato little leaf phytoplasma strain V4. The
restriction fragment length polymorphism pattern of all phytoplasmas compared
was identical except for 2 sweet potato little leaf phytoplasmas.
Influence of grazing frequency and intensity on tiller appearance and death rates of Lolium perenne L. under subtropical conditions
Authors: McKenzie F. R.
Published: August 2004

Use of Lolium perenne (perennial ryegrass) in
subtropical environments has been limited by its lack of persistence, possibly
resulting from poor grazing management. Perennial ryegrass tiller appearance
rates (TAR) and tiller death rates (TDR) were monitored under sheep grazing
for 2 years. There was a tillering ‘flush’ during the cool-season
months, relative to summer. This flush was highest for spring, with a minor
trough in winter, and was associated with high TAR and low TDR for these
periods. Summer was characterised by high TDR and low TAR. Seasonal patterns
of tillering and death were largely unaffected by grazing, although the
magnitude of TAR and TDR was manipulated by grazing within a given season.
Frequent intense grazing initially produced high TAR, but these were not
sustained. Frequent intense grazing resulted in the highest TDR relative to
other treatments. Infrequent grazing, irrespective of intensity, resulted in
the lowest TDR, particularly during summer, and should be considered by
managers to enhance persistence of perennial ryegrass in the subtropics.
Polyethylene glycol is more effective than surfactants to enhance digestion and production in sheep fed mulga (Acacia aneura) under pen and paddock conditions
Authors: Miller S. M. , Pritchard D. A. , Eady S. J. , Martin P. R.
Published: August 2004

Chemicals that interfere with the formation of tannin-protein complexes were
evaluated as dietary additives for mulga-fed sheep in pens and under paddock
conditions. Condensed tannins (CT) in mulga inhibit protein digestion, and the
use of chemicals to precipitate CT or dissociate CT-protein complexes may
improve production from sheep consuming a mulga diet. In a digestion study
with mulga-fed sheep in pens, provision of polyethylene glycol (PEG) at a rate
of 6 g/day significantly (P < 0·05)
improved nitrogen (N), phosphorus (P), and sulfur (S) balance, and apparent N,
P, dry matter (DM), and organic matter digestibility, and the rate of
liveweight gain. Addition of the surfactants SDS or alkanate 3SL3 to the diet
of mulga-fed sheep did not improve N balance or digestion; however, apparent
digestibility of P, and P and S balance, were significantly improved by SDS.
Teric PE64, a compound structurally similar to PEG, significantly improved S
balance, but not DM intake or N balance. For sheep consuming a predominantly
mulga diet under paddock conditions, provision of PEG at a rate of 12
g/day significantly improved clean wool growth and liveweight gain
compared with unsupplemented sheep, by 9% and 100%, respectively
(0·809 v. 0·745
mg/cm2.day, and 44 v. 22
g/day). The studies demonstrated that although surfactants can affect
mulga digestion, using PEG to precipitate CT is more effective to improve
mulga digestion and animal production than the use of surfactants. However,
the wool and liveweight production responses achieved with PEG were not
sufficient to justify its wide-scale use for mulga-fed sheep. Consequently,
alternative methods should be sought to reduce the negative effects of mulga
CT on sheep production.
Using fire to manage species composition in Heteropogon contortus (black speargrass) pastures.
Authors: Orr D. M. , Paton C. J.
Published: August 2004

Burning in spring can increase the proportion of the desirable species
Heteropogon contortus (black speargrass) when pastures
remain ungrazed following burning and to a lesser extent when the pasture is
grazed. Consequently, an experiment examined the effects on pasture
composition of annual spring burning followed by grazing deferment for 0, 2,
4, or 6 months or for 0 months but at half the stocking rate of the other 4
treatments.
Either deferring grazing for 4 or 6 months or halving the stocking rate after
burning in spring resulted in an increase in the proportion of
H. contortus. Burning reduced the undesirable
Aristida spp. as a pasture component and this effect
occurred independently of grazing treatment.
The development of 2 cohorts of H. contortus seedlings
was monitored for 18 months. Seedlings were selectively grazed but developed
rapidly with few differences between treatments. Differences in seedling
survival between years reflected differences in rainfall after establishment.
Results indicate that burning in spring to increase the proportion of
H. contortus will be more effective if followed by
4–6 months rest or by reduced grazing pressure.
Insulin sensitivity and fetal growth in ewes maintained in a moderate body condition compared with a lean body condition in late pregnancy
Authors: McNeill D. M. , Kelly R.W. , Williams I. H.
Published: August 2004

The possibility that an increase in maternal fatness might further enhance
pregnancy-induced insulin insensitivity was investigated in ewes pregnant with
one fetus. After selection of fat and lean ewes, they were fed to maintain
maternal energy balance throughout pregnancy. A difference in insulin
sensitivity of ewes in either a medium condition [score 2·9,
0·32± 0·031 kg fat/kg fat-free empty body (FFBW),
n = 7] or lean body condition (score
2·0, 0·16±0.028 kg fat/kg FFBW,
n = 8) at Day 136 of pregnancy was inferred by
comparing their insulin response to an injection of glucose (350 mg/kg
liveweight). The ewes were slaughtered at Day 146 of pregnancy to allow fetal
weight, fetal fatness, and maternal fatness to be related to the capacity of
the ewe to release insulin. The fatter ewes released more insulin in response
to the injection of glucose (2. 54 log area units under the insulin response
curve v. 2·22 for the lean ewes, pooled s.e.
= 0·092, P < 0·05), yet cleared
the glucose from their blood streams at the same rate as the leaner ewes.
Because the fat ewes required more insulin to remove a similar amount of
exogenous glucose at a similar rate to the lean ewes, we suggest that the fat
ewes were less sensitive to insulin. Further, the fetuses of the fatter ewes,
while not different in total weight, had higher levels of body fat than those
of the leaner ewes (29·4 v. 23·8 g/kg
FFBW, pooled s.e. r = 1·32,
P < 0·05). Fetal fatness was also positively
correlated to the magnitude of insulin release by the ewe
(r = 0·61, P <
0·05). Since glucose is the major precursor of fetal fat, these data
support our contention that a reduction in maternal insulin sensitivity,
brought on by an increase in maternal fatness, could partition more glucose to
the fetus. If fat reserves aid lamb survival, lambs from fat ewes rather than
lean ewes may have a better chance of survival, particularly in cold
conditions.
Effect of cultivar, sowing time, and density on the growth of subterranean clover in winter
Authors: Ru Y. J. , Fortune J. A. , Bellotti W. D.
Published: August 2004

In winter and early spring in Mediterranean environments, animal production is
often limited by the low herbage availability associated with low growth rates
and short swards, which result in low intake. In the present study, 26
subterranean clover (Trifolium subterraneum) cultivars
were evaluated for herbage availability early in the season. There were large
variations in dry matter yield (0·3-0·7 g/plant), sward
height (2·9-9·3 cm), and leaf area index (1·0-5·1)
among cultivars after 70 days of growth, indicating a possibility for
selection of cultivars based on these parameters.
Increasing plant density from 460 to 4600 plants/m2
increased dry matter yield from 88·5 to 362·8
g/m2 and sward height from 2·6 to 8·3
cm at Day 60.
Early sowing increased dry matter yield, sward height, petiole length, leaf
number, and leaf size by 13, 6, 32, 10, and 23%, respectively, after 70
days of growth. These results indicate that new pastures should be established
early if soil moisture is adequate, and that the time of the season break has
an important influence on early growth of pastures and, consequently, on the
budgeting of feed in farming practice.
Subsurface acidity and liming affect yield of cereals
Authors: Scott B. J. , Conyers M. K. , Poile G. J. , Cullis B. R.
Published: August 2004

In 2 field experiments, varying lime rates were applied to acidic soils and
incorporated to 10 or 20 cm depth by rotary hoeing. In Expt 2, soil was also
limed in 10-cm layers to 40 cm depth, and the profile was reconstructed. The
aim was to remove acidity as a constraint to plant growth. In both
experiments, 3 cereal cultivars (1 barley and 2 wheat) of varying aluminium
(Al) tolerance were sown. Grain yield was monitored in 4 seasons (Expt 1) or 5
seasons (Expt 2).
Incorporation of lime to 20 cm rather than to 10 cm improved yields of the
cereals in 2 of 4 seasons in Expt 1, and improved yields markedly in a drier
season in Expt 2. In Expt 2, cereal yield was demonstrated to be a function of
soil pHCa in both the 0-10 and 10-20 cm layers. There
was no advantage of amendment to 40 cm depth compared with 20 cm depth at this
site. At both sites, the 10-20 cm soil (corresponding to the upper A2 layer)
was very acidic, and the incorporation of lime to 20 cm removed this barrier.
The effect of amendment or pHCa increase in the 10-20 cm
layer is clearest and most consistent for barley, the most Al-sensitive
species, and least consistent for the tolerant wheat cultivars.
It is probably not realistic in commercial agriculture to incorporate lime to
20 cm depth. The alternative strategies are to wait for the effects of
amendment of the 0-10 cm layer to move down the soil profile, or to amend part
of the soil below 10 cm depth by lime injection. Until the subsurface soil is
amended, the best strategy is to combine surface liming (0-10 cm) with the use
of Al-tolerant cultivars.
Variation in growth, development, and yield of durum wheat in response to high soil boron. II. Differences between genotypes
Authors: Yau S. K. , Nachit, M. , Ryan J.
Published: August 2004

This greenhouse study examined the variation in growth, development, and yield
between 9 durum wheat (Triticum turgidum L. var.
durum Desf., syn. T. durum) lines
in response to high soil boron (B) levels. The lines were selected to
represent the range of B-toxicity tolerance in an earlier screening
experiment. Three soil B levels (hot-water extractable B concentrations of
0·3, 7·1, and 17·4 mg/kg, designated as B0, B25, and
B50, respectively) were set up by mixing different amounts of boric acid with
soil. Foliar B-toxicity symptom score, dry weight, and shoot-B concentration
were measured at tillering. Agronomic traits and yield were measured. There
were differential responses to high soil B levels between the durum lines. The
boron×line interaction was significant for B-toxicity symptom score and
shoot-B concentration. Based on these 2 characters, and percentage of shoot
dry weight and grain yield reduction from B0 to B50, Oued Zenati, Omrabi-5,
and Gezira-17 were the most tolerant of the 9 durum lines, yet they were less
tolerant to high soil B levels than the tolerant bread-wheat check, Halberd.
Nonetheless, until more tolerant materials are developed, these moderately
tolerant durum lines could still be useful for areas, like southern Australia,
where B toxicity is a problem.
The buffering capacity of caecal digesta exceeds that of rumen digesta from sheep fed pasture or roughage diets
Authors: Ding Z. , Rowe J. B. , Godwin I. R. , Xu Y.
Published: August 2004

The buffering capacities of caecal and rumen digesta of sheep on different
diets were determined by titration with lactic, acetic, and hydrochloric
acids, and certain factors affecting the buffering capacity of rumen digesta
were studied. Both rumen and caecal digesta had maximal buffering capacity at
pH 6·5–6·0. The buffering capacity of caecal digesta was
nearly double (P < 0·001) that of rumen
digesta. The rumen digesta from sheep fed oaten chaff had a buffering capacity
21% higher (P < 0·05) than that of
sheep grazing green pasture. This was reduced (P <
0·05) by one-third following ruminal infusions of glucose, lactic, or
acetic acid to induce acidosis. Diet did not significantly affect the
buffering capacities of rumen and caecal digesta. However, the buffering
capacities of rumen and caecal digesta from pasture-fed sheep that had been
fasted for 24 h were significantly greater (P <
0·001) than those for sheep that had not been fasted (62 and
18%). The buffering capacity determined using HCl was always less than
that for lactic or acetic acid. This may be due to the lower pKa for HCl and
the fact that there is no evidence that HCl undergoes inter-conversion through
fermentation that the organic acids may undergo. The addition of carbonate or
phosphate buffer significantly increased (P <
0·05) the buffering capacity of rumen and caecal digesta. The sodium
bicarbonate and sodium carbonate (NaHCO3 and
Na2CO3) system played a more
effective buffering role than the sodium dihydrogen orthophosphate and
disodium hydrogen orthophosphate
(NaH2PO4 and
Na2HPO4) system in the rumen
digesta.
Genetic analysis of variation for grain yield and protein concentration in two wheat crosses
Authors: Fabrizius M. A. , Cooper M. , Basford K. E.
Published: August 2004

Grain yield and protein concentration are two of the more important criteria
for wheat breeding in Queensland. Three aspects of the inheritance of both of
these traits can have an impact on achieving genetic progress:
(i) the magnitude and form of the genetic correlation
between the traits, (ii) the magnitude of genetic
variation and genotype × environment interactions, and
(iii) the importance of epistasis in genetic variation.
These 3 factors were examined for 2 crosses in a multi- environment trial
conducted in Queensland in 1989. Negative genetic correlations were found
between grain yield and protein concentration in both crosses. Genetic
variation and genotype × environment interactions were found to be
important for both traits. There was little evidence for the existence of
significant additive × additive epistasis for either trait and the
genotype × environment interactions were predominantly additive ×
environment in nature. From both crosses, progeny combining the high yield and
high protein levels of the parents were identified. This suggests that there
was a degree of independent segregation of the genes controlling grain yield
and protein concentration in both crosses. Therefore, simultaneous genetic
progress for yield and protein concentration is possible in Queensland
environments.
Phosphorus nutrition of spring wheat (Triticum aestivum L.). 1. Effects of phosphorus supply on plant symptoms, yield, components of yield, and plant phosphorus uptake
Authors: Elliott D. E. , Reuter D. J. , Reddy G. D. , Abbott R. J.
Published: August 2004

The effects of phosphorus (P) deficiency on plant symptoms, yield, and
components of yield of wheat (Triticum aestivum L. cv.
Halberd), P uptake, and the distribution of dry weight within plants of
variable P status were examined in 2 glasshouse and 5 field experiments.
Apart from stunted growth and depressed tillering, the symptoms of acute P
deficiency, most noticeable on older leaf blades, were equivocal; they were
not always observed on acutely deficient plants and were absent on moderately
deficient plants. In glasshouse experiments, the leaves of acutely deficient
plants were spindly, erect, and dark green, whereas in field experiments, the
leaves were pale green.
In acutely P-stressed plants, leaf senescence, phasic development, and
anthesis were delayed. The disorder restricted tiller development and
therefore the rate of appearance and the number of leaves per plant. It
depressed grain yield principally by reducing the number of fertile tillers.
Severe P deficiency depressed shoot growth within 15 days of sowing and
ultimately reduced plant height, root mass, and grain yield. In all
experiments, shoot yield responses to applied P increased progressively until
stem elongation (Zadoks Scale 30) and changed little thereafter. As a result,
the external requirement for P (i.e. P level required for 90% maximum
growth) increased with time during vegetative development in most experiments.
Severe P deficiency also affected the distribution of dry matter between the
roots and shoots and between the leaf blades and conducting tissues (sheaths
and stems). Both of these responses intensified with advancing plant age.
Treatment differences in P uptake in shoots also occurred early in growth and
persisted until grain maturity. The partitioning of P between roots and shoots
favoured P uptake or retention in the roots of P-deficient plants.
Under conditions of acute and moderate P stress, the resources of the wheat
plant appear to be directed towards maintaining root growth (at least
initially), limiting and delaying shoot proliferation, and maximising the leaf
: stem ratio. These regulations appear circumstantially to be adaptive
mechanisms for conserving suffiient P to ensure the survival of at least 1
weak, but fertile, tiller on each plant.
Phosphorus nutrition of spring wheat (Triticum aestivum L.). 4. Part 3, Aust. J. Agric. Res., 1997, 48, 883-97.. Calibration of plant phosphorus test criteria from rain-fed field experiments
Authors: Reuter D. J. , Elliott D. E. , Reddy G. D. , Abbott R. J.
Published: August 2004

Five single-year field experiments conducted on phosphorus (P) deficient soils
were used to calibrate plant P test criteria for rain-fed, spring wheat. At
each site, P concentrations in whole shoots and young and mature leaf blades
reached asymptotic values in the adequate-luxury P zone, within 6 weeks of
sowing. The asymptotic P concentration varied between sites and declined as
plants aged. The applied P level required to reach the asymptote increased
with advancing plant age. Two consistent trends in relationships between
relative shoot yield and P concentrations in whole shoots and leaf blades were
observed. Firstly, as plants aged, the slope of the relationship in the zone
of deficiency progressively increased and at later stages of growth became
nearly vertical so that severely deficient plants had P concentrations only
slightly lower than plants of adequate P status. Secondly, there was only a
narrow range of P concentrations in the zone of adequate to luxury P status
for whole shoots and young leaf blades.
Plant P test criteria derived from field- and glasshouse-grown wheat coincided
when related to stage of ontogeny as defined by the level of leaf insertion on
the main culm. Using this as a basis of stage of plant growth, plant P
criteria in shoots and young leaf blades were constant up until early
tillering, declined rapidly until late tillering, and thereafter decreased
more slowly. Critical concentration ranges for total P are proposed for YEB
and for whole shoots. Critical values for grain P were estimated to lie
between 0·19% and 0·23% P for 90% maximum
grain yield and between 0·21% and 0·24% for near
maximum grain yield.
Soluble P and labile P fractions were highly correlated and produced similar
relationships with relative shoot yield. The diagnostic relationships for both
fractions had steep slopes in the zone of deficiency and criteria for standard
leaf blades derived for either fraction sometimes declined as plants aged. The
labile P: total P ratios for YEB and YEB+1 were also of diagnostic value;
where this ratio was <30% during tillering, P deficiency was
assured.
Micropropagated dwarf off-type Cavendish bananas (Musa spp., AAA) show improved tolerance to suboptimal temperatures
Authors: Damasco Olivia P. , Smith Mike K. , Godwin Ian D. , Adkins Steve W. , Smillie Robert M. , Hetherington Suzan E.
Published: August 2004

The responses of micropropagated normal plants and dwarf off-types of
Cavendish (Musa spp. AAA) bananas to suboptimal
temperatures were evaluated under field and controlled environmental
conditions. Compared with bananas grown at 30/25°C (day/night),
leaf production at 18/14°C was inhibited by 51% in normal
plants and 18% in dwarf off-types. The emergence of the first leaf that
developed at low temperature was delayed by 11 days for normal plants and 5
days for the dwarf off-types. Photoinhibition of lamina, measured by decrease
in the chlorophyll fluorescence variable Fv/Fm, occurred in all banana
plants growing in the field during the winter months. The extent to which the
plants were photoinhibited was significantly greater for the normal plants
than dwarf off-types. Under controlled environmental conditions,
photoinhibition was similarly greater in normal plants than dwarf off-types.
After 153 h at 18/14C and a 9-h photoperiod of photon flux density (PFD)
of 380 mmol/m2· s, Fv/Fm was reduced by
22 and 13% for normal and dwarf off-types, respectively. When plants
were exposed to 18°C and a continuous PFD of 380
µmol/m2· s for 20 h, Fv/Fm was
reduced by 50% for normal plants and 36% for dwarf off-types.
The results of the study indicate that dwarf off-types generated from banana
micropropagation showed improved tolerance to low temperature and light,
showing better growth and lower susceptibility to low-temperature induced
photoinhibition than normal plants.