bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrigendum - The role of wheat non-starch polysaccharides in broiler nutrition
Authors: Annison G
Published: November 2004

It has been well established over a number of years that the apparent metabolisable energy (AME) value of wheat is highly variable. In 1983 and 1987 in Australia two surveys indicated that approximately 25% of wheats have AME values lower than 13 MJ/kg.DM (range 10.4-15.9 MJ/kg.DM). Following recent studies it has been proposed that the soluble non-starch polysaccharide cell-wall components of wheat (mainly arabinoxylan with some G-glucan) have an anti-nitritive activity when wheats are present at high levels in broiler diets and are responsible for the low-AME wheat phenomenon. The main findings supporting this hypothesis are (1) wheat AME values are negatively correlated with soluble non-starch polysaccharide levels, (2) low level addition (30g/kg) of commercially available pur non-starch polysaccharides to broiler diets depresses the AME,of the diets, (3) degradation of the cell wall polysaccharides in situ by addition of glycanases to broiler diets raises AME values, and (4) addition of purified wheat arabinoxylan to broiler diets depresses the AME in a dose-dependant manner. The AME depression is a result of the inhibition of starch, lipid and proteindigestion in the fore-gut. This paper reviews the experiments and the data from the studies and discusses further aspects of the anti-nutritive activity of cereal polysaccharides in broiler diets. The possible role of the gut microflora in the growth depression observed when diets containing high levels of rye, barley and wheat are fed to broiler chickens is also examined.
Carbohydrate and lipid oxidation during exercise
Authors: Pethick DW
Published: November 2004

In this paper, evidence is put forward to suggest that sheep are well adapted to maintain a supply of carbohydrate for contracting muscle when compared to other mammals such as the human athlete. This is achieved by a remarkable ability to maintain or even elevate glucose concentration in the blood through 'feed forward' control of glucose metabolism. Glycogen, whether hepatic or muscle, is also readily utilized at work rates above the anaerobic threshold. The ability to replace glycogen is substantial in sheep which are adapted to exercise and in type IIA muscle is not greatly lower than in non-ruminant animals. Aspects of long chain fatty acid (NEFA) metabolism are also discussed. An interesting finding in sheep is the partial oxidation of NEFA to acetate during sustained exercise at above the anaerobic threshold. This represents a mechanism to increase the power of fat oxidation and deserves attention in other species.
Increasing annual growth rates of cattle by reducing maintenance energy requirements
Authors: Hunter RA , Sillence MN , Gazzola C , Spiers WG
Published: November 2004

In seasonally dry areas cattle undergo periods of arrested growth because the forage on offer is of poor quality. Annual liveweight gains could be increased and age of turnoff for slaughter reduced if maintenance energy requirements could be lowered during the dry season with no concomitant reduction in forage intake. Strategies to reduce metabolic rate, and so rate of liveweight loss using the anabolic steroid, trenbolone acetate, and the �2-agonist, guanfacin, are discussed. Both compounds reduced fasting metabolic rate of steers; an implant of 300 mg trenbolone acetate by about 10% and continuous intravenous infusion of 40 8g/kg liveweight per day guanfacin by about 20%. The effects of other anabolic steroids on energy metabolism is reviewed. Trenbolone treatment of steers fed a low-protein roughage diet reduced voluntary feed intake. The mechanism by which this occurred was established and is discussed, as are studies aimed at determining the mechanism by which trenbolone reduces metabolic rate. Further, it has been established that the guanfacin-induced reduction in metabolic rate which is largely mediated peripherally is an �2-adrenergic effect and not some other effect of the drug.
Changes in plasma amino acid patterns and wool growth during late pregnancy and early lactation in the ewe
Authors: Masters DG , Stewart CA , Connell PJ
Published: November 2004

Pregnancy and lactation result in depressed growth, fibre diameter and tensile strength of wool. Competition for nutrients between wool follicles, maternal tissues and the foetus may cause these changes. Changes in the concentrations of individual free amino acids in plasma, during late pregnancy, were used as indicators of limiting amino acids in this experiment. A group of pregnant ewes was maintained in the animal house during late pregnancy and early lactation and measurements made on amino acids in plasma. Liveweight, wool growth and quality characteristics and sulfur in wool were also measured. Comparisons were made between the different time periods in pregnancy and lactation and between the reproducing ewes and a group of non-reproducing ewes maintained under the same conditions. During the last 3 weeks of pregnancy, there was a 31% decline in the concentration of the total, free essential amino acids in plasma. There was also a significant decline in the concentration of arginine (60%), lysine (55%) and threonine (48%). The concentrations of these amino acids increased during the first 3 weeks of lactation. There was no change in concentration of methionine or cystine. Wool growth rate was lowest in the last 3 weeks of pregnancy and the reproducing ewes had significantly lower wool growth, fibre diameter, staple strength and sulfur in wool than the non-reproducing ewes. The results indicate that a lack of the sulfur-containing amino acids is unlikely to be limiting, but a lack of arginine, lysine or threonine may be limiting wool growth and protein deposition in late pregnancy.
Relationship of feed intake with cystine availability and wool growth in Merino wethers
Authors: Lee GJ , Williams AJ
Published: November 2004

Two experiments were conducted to characterize the relationship between nutrient supply and the rate of wool growth. We concentrated on the accepted view that the rate of wool growth in Merino sheep is primarily limited by the availability of sulfur amino acids, which are largely determined by diet intake and its interaction with microbial fermentation in the reticulo-rumen. In the first experiment, the effects of variable intakes of two diets (one including 10% fishmeal) by sheep on the rate of irreversible loss of cystine and plasma cystine concentration were investigated. Nitrogen intake (N) was positively and linearly related to both the irreversible loss rate and the plasma concentration of cystine, with no effects of diet per se. In the second experiment, the same dietary treatments were imposed on 39 wethers for 16 weeks following an 8 week pre-experimental period. The monthly rates of wool growth, average fibre diameter and sulfur content of the wool were measured and related to various components of intake. The rate of wool growth responded in a positive curvilinear decreasing manner to changes in intake, the response requiring 2 months to stabilize. There was no significant effect of diet when daily intake was expressed as g N kg-0.75 liveweight. Including the covariate (wool growth when fed the standard diet), the quadratic linear model accounted for 90% of the total variation in wool growth. Responses in fibre diameter and its variation, and wool sulfur content were similar to those of wool growth, in that they were positive and did not equilibrate quickly. A saturation kinetics model of the relationship between daily N intake (g N kg 0.75 liveweight) and wool growth accounted for a similar proportion of the variation as did a linear (with quadratic term) model without the covariate. It is concluded that the saturation kinetics model may be useful for more comprehensive comparisons of both the genetic potential and the sensitivity of wool growth to environmental changes.
Fleece growth in Australian cashmere goats. II. The effect of pregnancy and lactation
Authors: Kloren WRL , Norton BW
Published: November 2004

Groups of Australian cashmere does were randomly assigned to December, March, July and September kidding groups in two successive years, and cashmere and hair growth was compared to does not kidding in each year. There was no significant (P > 0.05) effect of kidding time on cashmere growth rate. Kidding in December significantly (P < 0.05) delayed initiation of cashmere growth by around 2 weeks and occurred around February. Half of the does kidding in March failed to grow cashmere, and of the others, initiation date or rate of growth was not affected. Kidding in July advanced the cessation of cashmere growth to May compared with July in control does. Does kidding in September had cashmere growth cycles similar to those of control goats; however, fleece regrowth following shearing in June was significantly (P < 0.05) less. There were no consistent effects of kidding time on hair growth, but regrowth was significantly (P < 0.05) greater in the March kidding group following shearing in June.
Application of the Fick principle to the continuous measurement of energy expenditure in pigs
Authors: Giles LR , Gooden JM
Published: November 2004

The paper reviews the current methods available for the measurement of heat exchange in pigs. The cost of construction of automated open-circuit respiration chambers, in association with climate-controlled facilites, has restricted continuous measurement of energy expenditure in pigs to a small number of laboratories around the world. Ventilated hoods and face mask techniques are not viable alternatives because of difficulties in maintaining a uniform environment around the animal and restriction of food intake. Indirect techniques, including carbon dioxide (CO2) entry rate and doubly-labelled water are only applicable when other technique are not available because of the errors involved when energy expenditure is based on CO2 production alone. An alternative procedure is described for the measurement of energy expenditure in the growing pig. Whole-body oxygen (O2) consumption is calculated from the product of cardiac output and the arteriovenous difference in blood O2 concentration across the lungs (Fick principle). Oxygen consumption recorded with the new procedure was compared with the ventilated hood and CO2 entry-rate techniques, and used to examine the heat exchange of growing pigs maintained at high ambient temperatures
National survey of viruses in pastures of subterranean clover. I. Incidence of four viruses assessed by ELISA
Authors: Helms K , Muller WJ , Waterhouse PM
Published: November 2004

A nationwide survey was made of the time-course incidence of alfalfa mosaic virus (AMV), clover yellow vein virus (CYVV), subterranean clover mottle virus (SCMoV) and subterranean clover red leaf virus (SCRLV) in improved pastures in southern regions of Australia over a 3-year period. Up to 2 500 samples (cvv. Mt Barker or Woogenellup) were collected in winter and spring of 1984, 1985 and 1986 in each of New South Wales, Victoria, South Australia. Western Australia and Tasmania, and assayed by ELISA. Usually, each sample consisted of one or two plants or parts thereof. However, a small number of samples in winter contained parts of up to 10 seedlings. For this reason, incidences are expressed as percentage of infected samples rather than percentages of infected plants. All four viruses occurred in all five states. Averaged over all states, the incidence of infected samples increased progressively from 15.3 to 19.9 to 22.5% from 1984 to 1985 to 1986, respectively, in spring, and from 6.8 to 13.8 to 18.8% respectively in winter. The incidence of samples infected with multiple infections (2-4 viruses) increased from 1.9 to 3.2 to 5.0% from 1984 to 1985 to 1986, respectively, in spring, and from 0.5 to 1.6 to 4.0%, respectively, in winter. Since 1-4 viruses were detected in each infected sample, more individual infections than infected samples were recorded. For example, the incidence of virus infections per paddock increased progressively from 17.5 to 24.1 to 28.6% from 1984 to 1985 to 1986, respectively, in spring. On a state basis, the incidence of infected samples was greatest in W.A., reaching 38.9 and 34.9% in spring of 1985 and 1986, respectively, and in S.A. reaching 30.3% in spring of 1986; these high levels were due largely to SCMoV which reached 97% in one paddock in each of the two states. In N.S.W., Vic. and Tas., the highest incidences of infected samples in either winter or spring were 21.4, 16.2 and 23.1%, respectively. Averaged over all states, the highest mean incidence recorded for samples infected with individual viruses in either winter or spring was 9.4% for AMV, 5.7% for CYW, 10.9% for SCMoV and 7.5% for SCRLV. For AMV and SCRLV, there was an increasing trend from spring 1984 to spring 1986. A similar increasing trend for SCMoV was more evident in winter than in spring. For CYVV, no time-course pattern was evident. These results support the proposition that viruses contribute significantly to 'clover-decline', a well-known problem in pastures of subterranean clover.
Dynamics of carbon and nitrogen in a long-term cropping system and permanent pasture system
Authors: Robertson FA , Myers RJK , Saffigna PG
Published: November 2004

On the brigalow lands of south-east Queensland, productivity of sown perennial grasses is severely limited by N availability, whereas annual crops grown on the same soil are N-sufficient. The dynamics of C and N were compared under in these soils under permanent green panic (Panicum maximum var. trichoglume cv. Petrie ) pasture and continuous cropping with grain sorghum (Sorghum bicolor). Although the sorghum system was more productive, it contained 18% less N and 29% less C. Annual flows of C and N through the soil microbial biomass were, respectively, 4500 and 240 kg ha-1 under sorghum, and 4050 and 60 kg ha-1 under pasture. Over 80% of C and N inputs to the sorghum system occurred after harvest. Under pasture, the continuous supply of residues of high C/N ratio (50-75) enabled the development of a large and active microbial biomass, which competed with the pasture plant for N, resulting in slow net mineralization of N and low levels of inorganic soil N. Under sorghum, the size of the microbial biomass was limited by C availability during the growing season. The sorghum residues had slightly lower C/N ratios (36-46), and their rapid decomposition and net mineralization of N were promoted by the fallow period and soil cultivation. Estimated annual C turnover through the soil microbial biomass was slightly faster under sorghum, and annual N turnover was around seven times faster under sorghum than under green panic. The productivity of these soils under the two management systems was controlled by the amount, quality and timing of organic matter inputs. These in turn controlled the size of the soil microbial biomass and its C and N supply, and hence the balance between immobilization and mineralization of N.
Field studies of cadmium in potatoes (Solanum tuberosum L.). III. Response of cv. Russet Burbank to sources of banded potassium
Authors: Sparrow LA , Salardini AA , Johnstone J
Published: November 2004

Six field experiments were conducted where Russet Burbank potatoes were grown with banded fertilizer consisting of diammonium phosphate (DAP) and either potassium sulfate (K2S04) or potassium chloride (KCl). At each site, rates of nitrogen (N), phosphorus (P) and potassium (K) were matched as closely as possible for each K fertilizer treatment. At four of the six sites, potatoes grown with K2S04 had tuber and petiole cadmium (Cd) concentrations 20-30% lower than did potatoes grown with KCl. The use of K2S04 instead of KCl appears to offer considerable promise as a means of decreasing tuber Cd uptake. Sulfate ions presumably promote increased soil adsorption of soil and/or fertilizer Cd compared with chloride ions, and so decrease Cd availability. We attributed the lack of difference in tuber and petiole Cd between K sources at two sites to either leaching, chloride in irrigation water, or at one site to a higher than desired rate of NPK fertilizer with the sulfate treatment. Any one of these may have offset decreases in Cd uptake due to the presence of sulfate ions.
Seasonal variation in voluntary feed intake and growth in cashmere bucks fed ad libitum diets of low or high quality
Authors: Walkden-Brown SW , Norton BW , Restall BJ
Published: November 2004

The effects of season and diet quality on voluntary feed intake and growth were examined in mature cashmere bucks over a 16 month period at Wollongbar (29�S., 153� E.). Three-year-old bucks were individually housed under natural photoperiod and fed ad libitum diets of High (pelleted lucerne, CP 17.6%, ME 8.3 MJ/kg) or Low (pasture hay; CP 6.9%, ME 6.6 mJ/kg) quality, between July 1988 and Oct. 1989 (n = 6/treatment). Bucks on both diets exhibited a seasonal pattern in voluntary feed intake with maximal intakes during spring and summer, and minimal intakes during autumn. The pattern appeared to be circannual with high intakes during spring of both years. Liveweight also varied with season peaking in mid to late summer and reaching a seasonal nadir in late autumn or early winter. Change in liveweight was closely associated with digestible energy intake ( r = 0-87, P < 0.001) resulting in a growth cycle closely resembling that of voluntary feed intake. In both treatments, bucks lost weight throughout autumn, while growth rates were maximal between mid-winter and mid-spring. Diet quality did not alter the magnitude of the autumnal decline in liveweight with bucks losing 7.6% (Low) and 7.8% (High) of liveweight during this period. However, bucks on the high quality diet exhibited significantly elevated growth rates between mid-winter and mid-spring. We conclude that mature cashmere bucks exhibit an annual growth cycle with weight loss during autumn and maximal weight gains between mid-winter and mid-spring; that the growth cycle is driven primarily by changes in voluntary feed intake; and that increasing diet quality does not reduce the autumnal decline in liveweight but significantly increases liveweight gain during the seasonal peak in growth.
Selenium fertilizers for pastures grazed by sheep. 1. Selenium concentrations in whole blood and plasma
Authors: Whelan BR , Peter DW , Barrow NJ
Published: November 2004

Two forms of prilled selenium fertilizer from Mintech N.Z., Na2 SeO4 (Selcote�) and BaSe04 incorporating a slow-release technology, were applied to pasture once at 10 and 20 g Se ha-1 in 1987 at Bakers Hill, Western Australia. The pasture was grazed at 10 sheep ha-1 for 3 years. In the first year, half the sheep were also treated with a selenium intra-ruminal pellet. The Selcote fertilizer produced a rapid rise in pasture selenium concentration, resulting in a similar response in the concentrations of selenium in the whole blood and plasma which reached their maximum values within 7 weeks of commencing grazing. The selenium concentration then declined until, after 15 months, there was insufficient selenium in the pastures to increase the selenium status of sheep. In contrast, the slow-release formulation provided adequate selenium in each of the 3 years with sheep reaching their maximum plasma selenium of 80 8g Se L-1 in the second and third year. At relatively low values for whole blood selenium (< 75 pg Se L-1), supplying an additional selenium source had an additive effect on selenium concentration in the blood, but at higher concentrations (> 350 8g Se L-1) additional sources of selenium only marginally increased the whole blood concentration of selenium. Plasma was a more sensitive indicator of the selenium content of pasture in the short term than whole blood. The results indicate that either Selcote or the BaSe04 fertilizer provides an effective alternative to current strategies for supplying Se to grazing animals.
An investigation of the grain yield adaptation of advanced CIMMYT wheat lines to water stress environments in Queensland. I. Crop physiological analysis
Authors: Cooper M , Byth DE , Woodruff DR
Published: November 2004

Wheat improvement in Australia has made extensive use of germplasm developed by the International Maize and Wheat Improvement Center (CIMMYT). The opportunity for further yield improvement in Queensland was investigated by comparing CIMMYT lines and Queensland cultivars in irrigated and dryland environments at three locations. CIMMYT lines were identified, with greater than 20% yield advantage in individual environments and between 15 and 20% yield advantage over the six environments. The line mean repeatability for yield was moderate (0.492), with the variance component for line by environment (L x E) interaction 4.2 times that for lines. Therefore, while the CIMMYT lines expressed considerable L x E interaction, there was scope for further yield improvement. The water stress differential between the irrigated and dryland environments at the three locations strongly influenced L x E interaction for grain yield. Pre-anthesis water stress generated more L x E interaction for grain yield than post-anthesis stress. At the two locations where pre-anthesis water stress was severe in the dryland environment, there was no association (P > 0.05) between yield under irrigated and dryland conditions. However, at the location where there was little pre-anthesis stress and a degree of post-anthesis stress there was a strong association (P < 0.01) between yield under irrigated and dryland conditions. Grain yield was positively associated with the yield component grain number per unit area in all environments. Grain weight showed little L x E interaction across environments and the majority of L x E interaction for grain yield resulted from L x E interaction associated with grain number per unit area. Grain number per unit area was positively associated with the component grains per fertile tiller but not tiller number per unit area. Grains per fertile tiller was in turn positively associated with total dry matter at anthesis; however, there was no direct association between total dry matter at anthesis and grain number per unit area. There was a weak association between days to anthesis and grain yield in four of the six environments.
Ribosomal DNA, peroxidase and extensin variation in genomic DNA of Medicago laciniata (L.) Miller from Australia and Africa
Authors: Young RR , Lagudah ES
Published: November 2004

Fifty-four Medicago laciniata (L.) Miller accessions from diverse locations in eastern Australia, Africa and Israel were characterized for genotypic differences by restriction endonuclease cleavage of genomic DNA and probing with radio-labelled DNA sequences to detect restriction fragment length polymorphisms (RFLP). Digestion of the genomic DNA with the restriction endonuclease, Bam HI, and probing with the complete ribosomal DNA (rDNA) repeat unit of soybean (pGmrl) and its subclones revealed that the variable region in M. laciniata spans the Bam H1 sites of the intergenic spacer region between the 18s and 26s DNA. The length variation in the rDNA repeat unit clearly distinguished South African from Australian accessions. The rDNA variants from SA1847 (Morocco) and SA7750 (Tunisia) were the same as the Australian accessions and slightly larger than the rDNA spacer variant unique to SA3428 (Israel). When Eco R1 digested M. laciniata genomic DNA was probed with peroxidase and extensin cDNA clones, all Australian accessions were again characterized by the same RFLP genotype with further differentiation between African and Israeli accessions. An accession of unknown origin, SA3412, possessed the same RFLP genotype as the Australian accessions for all endonuclease and probe combinations. For the African accessions, differences in RFLP genotype were more frequent than differences in phenotype (leaflet laciniation and colour). However, of three South African accessions with the same RFLP genotype, SA26844, SA26847, and SA26848, SA26847 had more pronounced leaflet laciniation.
Follicular determinants of the length and diameter of wool fibres. 1. Comparison of sheep differing in fibre length/diameter ratio at two levels of nutrition
Authors: Hynd PI
Published: November 2004

Two groups of sheep were formed with similar mean fibre diameter (D) but differing rate of fibre elongation (L), and two groups with similar mean L but differing D. The sheep were placed on a low plane of nutrition for 8 weeks followed by a high plane of nutrition for a further 7 weeks. L, as a result of selection and nutrition, ranged from 268 to 515 8m/day, D from 17.5 to 32.8 8m, and LID ratios from 13 1 to 24.5 between individuals. Nutrition significantly influenced the dimensions of the follicle bulb and dermal papilla, the rate of division of follicle bulb cells, the dimensions of the cortical cells, and the production ratio (the ratio of fibre area to fibre-plus-inner root sheath area). The high and low diameter groups differed in bulb and papilla dimensions and in the rate of bulb cell division. The high and low fibre length growth phenotypes differed only in papilla length and cortical cell length. Stepwise multiple regression analysis revealed that a model including terms for nutrition, phenotype group and cortical cell length accounted for 0.60 of the variance in fibre L (P < 0.0001). Fibre D was best accounted for by nutrition, phenotype group, cortical cell volume and papilla area ( Ra2 = 0.88, P < 0.0001). This differential dependence of the fibre dimensions on follicle characters means that the shape of the fibre has the potential to change in situations where cortical cell length, cortical cell volume and papilla size are differentially altered. Several hormonal, nutritional and selection regimes known to alter L/D must have this effect, but simple nutritional changes such as the one imposed in this experiment apparently do not, as there was no change in fibre L/D. The follicular efficiency of fibre production (measured as fibre output per unit bulb tissue or per unit bulb cell produced) in sheep producing fine (20.3 8m) wool was similar to that of sheep producing coarse (27.0 8m) wool. There appears therefore to be no inherent inefficiency in small follicles producing fine wool and thus no follicular impediment to the production of large amounts of fine wool.
Reduction of synthetic and mitotic activity in the wool follicle by catecholamines
Authors: Scobie DR , Hynd PI , Setchell BP
Published: November 2004

Literature evidence on the effects of catecholamines on wool growth is scant and the short-term effects have not been investigated. Since catecholamines are relatively short-lived, three approaches were adopted to investigate their effects on cellular events in the wool follicle over periods as short as 4 h. In vitro culture of skin revealed a reduction of DNA synthesis in response to either adrenaline or noradrenaline added to the media (P < 0.001) in a dose-dependent manner (P < 0.001). Intradermal injections of adrenaline and noradrenaline significantly lowered the rate of cell division in wool follicles in comparison with control sites in vivo (P < 0.05). These results indicate that the catecholamines can rapidly lower the rate of proliferative events in the wool follicle. The left superior cervical ganglion was removed from 18 sheep. The animals were exposed to a cold environment and ear temperature was monitored to indicate the likely release of noradrenaline in the skin of the cheeks or adrenaline from the adrenals. With respect to the sympathectomized side, a reduction in ear temperature on the unoperated side was associated with lowered mitotic rate at the unoperated cheek site (P < 0.026). However, when the temperature of the unoperated side was not lowered, mitotic rate was not consistently lower on one side with respect to the other. Physiological levels of noradrenaline therefore mimicked the effects observed during the pharmacological studies, and the catecholamines may therefore play an important role in the regulation of wool growth.
Digesta flow and rumen microbial protein production in ewes grazing perennial ryegrass
Authors: Dove H , Milne JA
Published: November 2004

Herbage organic matter (OM) intakes and the abomasal flows of OM, non-ammonia nitrogen (NAN) and microbial nitrogen (MN) were estimated in ewes grazing perennial ryegrass during lactation in spring/summer (Group 1) or in autumn after the end of lactation (Group 2). On average, ewes in Group 1 consumed 804 g OM/day more than ewes in Group 2, while their daily abomasal flows of OM, NAN and MN were, respectively, 372, 28.8 and 26.7 g/day more than those in Group 2 ewes. The regression equations relating the flows of digesta or digesta components to OM intake were significantly different between the two groups of ewes. Rumen ammonia and volatile fatty acid levels were significantly higher in Group 1 ewes, though ewes in Group 2 had significantly higher molar proportions of acetate and significantly lower proportions of butyrate and especially propionate. Ewes in Group 1 had significantly faster CrEDTA fractional disappearance rates (FDR) (0.1474 h-l) than ewes in Group 2 (0.0847 h-l). The efficiency of microbial protein synthesis in Group 1 ewes was consistent with published values and was almost twice that estimated in Group 2 ewes. Results are presented to suggest that the observed differences between the two groups or ewes are not due to an effect of lactation, but to differences in the composition of the consumed herbage in autumn compared with spring/summer. It is argued that the observed differences in rumen fermentation pattern between the two groups of ewes reflect underlying differences in the water-soluble carbohydrate content of the consumed herbage. The inclusion, in multiple regression analyses, of either rumen propionate or rumen acetate : propionate ratio, together with OM intake explained approximately 0.80-0.85 of the variance in NAN or MN flows, reduced residual standard deviations compared with fitting OM intake alone, and removed the difference between the two groups of ewes. Inclusion of the CrEDTA FDR contributed no further explanation of the variance in the above flows.
Segregating red and white wheat visually and with a tristimulus colour meter
Authors: Bason ML , Zounis S , Ronalds JA , Wrigley CW
Published: November 2004

With red-grained wheat now being grown in Australia in some places, there is a need to segregate it from white grain at the silo to avoid loss of milling and end-use quality. The Minolta tristimulus colour meter and visual inspection have been assessed as possible means to facilitate this segregation. Using only reflected light for sample illumination, 86% of a restricted sample set were correctly classified visually, and 95% of all samples using the Minolta meter. These values were increased to up to 99% in both cases by additionally using transmitted light to illuminate the samples. Thus both the Minolta and visual methods that included alternate use of both illuminant sources provided good segregation of red and white wheat samples. Sample transillumination was particularly helpful for classifying vitreous white grain, and also red grain that had been bleached by rain.
Effects of continuous cultivation on Ferrosols in subtropical southeast Queensland. I. Site characterization, crop yields and soil chemical status
Authors: Bell M. J. , Harch G. R. , Bridge B. J.
Published: November 2004

The productivity of Ferrosols used for rainfed agricultural production in the south and central Burnett regions of south-east Queensland was examined in relation to the duration under continuous cultivation. A range of crops grown in on-farm situations during 1986-90 were examined using paired sites to assess the extent of yield decline with time under cropping. The changes in soil chemical characteristics that have occurred during the cropping period were also assessed. All locations showed evidence of a significant reduction in crop growth (50-100%) where continuously cropped sites were compared with sites which had either never been cropped or which had been under grazed grass pasture for >20 years. In the absence of severe late season water deficits, this reduced growth rate was always reflected in lower (21-72%) crop yields at maturity. However, crop dry matter (DM) could interact with crop water use under conditions of late-season water deficit to negate, or even reverse, early growth advantages on previously untilled soil. At least part of the observed yield reduction on continuously cropped soil was due to nutrient deficiencies resulting from depletion of both surface and subsurface reserves during cropping. Long-term cropping has resulted in depletion of soil K and Zn (especially in the subsoil), organic carbon and total N status, and caused significant acidification of both surface and subsoil layers despite the use of lime. The decline in subsoil K status and falling subsoil pH have severe implications for crop performance in dry seasons, when crops rely on subsoil reserves to sustain crop growth. The decline in soil N status has occurred despite a high frequency (>50%) of grain legumes in the crop rotations practised on all farms monitored, and illustrates the small N return from these crops under rainfed conditions. The reduction in soil organic carbon due to cropping was extreme, with continuously cropped areas having organic carbon levels of only 0.9 to 1.5% in the 0-10 cm layer-values which were only 25-40% of levels in untilled soil. Grazed grass leys were only partly successful in restoration of soil organic carbon status.
Economic values of traits for pig improvement. I. A simulation model
Authors: Skorupski MT , Garrick DJ , Blair HT , Smith WC
Published: November 2004

A computer model simulating life cycle production of a breeding sow and growth performance of her offspring was developed to estimate economic values of reproduction and growth performance traits. A biological growth model, simulating the digestion and metabolism of dietary nitrogen in growing pigs (20 to 85 kg), was part of the life cycle model. The growth model was based on the linear/plateau relationship between daily protein deposition and digestible energy intake. A farrow-to-finish production system, with slaughter pigs marketed at fixed liveweights, was simulated. Input variables were: gilt age at first oestrus, weaning to oestrus interval, number of pigs born alive per litter, and pre-weaning mortality for each parity. Economic inputs included prices of feed ingredients, carcass returns and non-feed costs. The upper limit to body protein deposition rate, mean daily ad libitum digestible energy intake and minimum lipid to protein deposition ratio were assumed the major genetic determinants of pig growth. The model output included average daily gain, ad libitum daily feed intake, backfat thickness, and life cycle reproductive performance and profit. The combined life cycle profit was expressed in the form of an Annualized Present Value. Life cycle profit was calculated for a range of simulated pig genotypes.
Studies on Western Australian Merino sheep. III. Genetic and phenotypic parameter estimates for subjectively assessed and objectively measured traits in ewe hoggets
Authors: Lewer RP , Woolaston RR , Howe RR
Published: November 2004

Between 1440 and 2084 Merino hoggets were scored for visual traits, with the number of records differing according to the traits. Eight wool traits and seven body traits were subjectively assessed, while four wool traits and five serial liveweights were measured. Heritabilities for all subjective traits were estimated, with sire models using restricted maximum likelihood, as were genetic and phenotypic correlations between subjective and objective traits. Heritability estimates for back wool, lock thickness, wool character, underline, condition, wool colour, hock shape, feet shape, face cover score, neck wrinkle, breech wrinkle and side wrinkle were moderate (0.1 to 0.3), while those for visual fineness and wool handle were high (0.34 and 0.41), and overall score, low (0.06). Correlations between these traits and objective traits having economic value (wool weight, average fibre diameter and liveweight) were low or negligible, indicating that it may be more efficient if classing traits are not used to the exclusion of objectively measured traits. However, under some circumstances, they may have potential for increasing selection efficiency or used as an inexpensive first step in a two-stage selection procedure.
Pentosan levels in Australian and North American feed wheats
Authors: Wootton M , Acone L , Wills RBH
Published: November 2004

Pentosan levels in 19 Australian and 12 North American wheats, predominantly of feed grade, were determined. Values were not significantly different between wheats from the two regions and ranged from 5.4 to 7.2% in the Australian and from 5.5 to 6.5% in the North American samples. Apparent metabolizable energy (AME) values for the Australian wheats, when used in poultry rations, showed a positive correlation with pentosan levels, which is counter to current thinking that suggests a negative relationship. These results imply that any difference between feed wheats from the two regions with respect to AME in poultry rations cannot be attributed to pentosan content.
Some comparative studies of sulfate metabolism in Merino sheep genetically different in wool production
Authors: Williams AJ , Williams AJ
Published: November 2004

Several aspects of sulfate metabolism were compared in sheep from two selection flocks, selectively bred for either high (Fl+) or low (FI-) clean fleece weight per head. These were studied within a 23 factorial design: 2 flocksx2 levels of formaldehyde treated casein in diet (0 or 80 g day-1)x2 levels of subcutaneous L-thyroxine (0 or 1 mg day-1) with 4 sheep per cell. The treatments influenced the rates of wool growth and the output of sulfur in wool (P < 0.05), but with interactive effects (P < 0.05). The F1+ sheep produced 24 and 32 8g sulfur in wool cm-2 day-1at the midside when consuming the control and casein supplemented diet. The outputs of sulfur in wool by F1- sheep consuming these two diets were 16 and 17 8g cm-2 day-1. The thyroxine treatment increased the rate of growth of wool by 11% (P < 0.05), but did not increase average fibre diameter or the sulfur content of wool. Sulfate was cleared more rapidly (P < 0.05) from the plasma of sheep consuming the casein supplemented diet, with a rate constant of 0.134 h-1, compared to 0.099 h-1for the control sheep. The rate constants for Fl+ and F1- sheep were 0.102 and 0.131 h-1 respectively (P < 0.05). The concentration of sulfate in plasma was similar in all treatment groups: 1.3 mmol L-1The differences in the clearance of sulfate from plasma were reflected in similar differences in the proportion of the injected 35S-sulfate excreted in urine during the following 24 h. The sheep of the F1- flock and those consuming the casein-supplemented diet excreted significantly greater proportions of the injected 35S in urine (P < 0.05). In a second experiment, adult sheep (n = 24), the progeny of F1+ or F1- rams mated with a flock of medium wool Merino ewes, were randomly allocated to a low (c. 0.8 maintenance, 1 g sulfur day-1) or high (c. 2xM, 3 g sulfur day-1) dietary regime. [35S] sodium sulfate was again injected intravenously. There were no significant differences between the genetic groups for (i) sulfate concentration in plasma, (ii) total and net rates of irreversible loss of sulfate from plasma, (iii) the proportion of the injected [35S] sodium sulfate excreted in urine, (iv) the proportion of the excreted 35S present in urine as sulfate, and (v) the quantity of sulfate excreted in urine daily. However, the dietary treatments significantly influenced all these traits, except the concentration of sulfate in plasma. The direction of these effects was consistent with the proposition that sheep regulate excretion of sulfate from kidneys to maintain homeostasis of sulfate within the body. The smaller phenotypic difference in wool production between the two half-bred flocks in the second experiment, probably limited the chances of detecting any differences in the metabolism of sulfate.
Evaluation and selection of bread wheat (Triticum aestivum L.) for preharvest sprouting tolerance
Authors: Trethowan RM
Published: November 2004

This paper examines the success of selection for preharvest sprouting tolerance in white-grained bread wheat using a standard wetting treatment, germination of hand-threshed seed and falling number measurements. The rain simulator was usefull in shifting the population mean of field grown material towards higher levels of tolerance in successive years; however, large genotype x year interactions in material sown under rain protection did not allow accurate assessment of individual genotypes. The most accurate assessments were achieved using falling number measurements (h2 = 80.7%) and hand-threshed seed germinations (h2 = 38.4%), where no genotype x year interactions were recorded. Seed dormancy (determined from hand threshed grain) correlated significantly with change in falling number following 3 days' treatment in the rain simulator ( r = -0-56**). Visual measurements scored in the rain simulator, however, did not correlate significantly with seed dormancy in the first year (r = 0.20) but correlated strongly in the second (r = 0.73***). In comparisons of the same test between years, falling number (without rain treatment) and seed dormancy were significantly correlated (r = 0.68* and 0.90***, respectively), whilst visual scores of sprouting showed no association (r = -0.03).
N application enhances remobilization and reduces losses of pre-anthesis N in wheat grown on a duplex soil
Authors: Palta JA , Fillery IRP
Published: November 2004

The effect of fertilizer N on the remobilization of N to the grain in wheat was evaluated on a duplex soil at East Beverley, Western Australia. Remobilization of N to the grain was determined using the stable isotope, 15N , which was fed to wheat plants during the vegetative growth phase. Nitrogen was applied at 15, 30 and 60 kg N ha-1 with half being applied at seeding and the remainder at 35 days after sowing (DAS), before the onset of tillering. The high N treatment increased N uptake between stem elongation and anthesis and grain protein concentration by 2.9% relative to the low N treatment. Both the nitrogen harvest index (NHI) and the nitrogen utilization efficiency (NUE) declined as the rate of N application was increased; the decline was more pronounced when the rate of N application was increased from 30 to 60 kg N ha-1. Total grain N at 60 kg N ha-1 was increased by 54%, relative to that at 15 kg N ha-1, due to a 2.3 fold increase in remobilization of pre-anthesis accumulated N and despite a 5 fold reduction in post-anthesis uptake. The application of 60 kg N ha-1 reduced the losses of pre-anthesis N from 19% to 6%. The absolute contribution of the N taken up early in the growth of the crop (before the second node stage) to grain N was 0.9, 1.4 and 3.2 g m-2 at 15, 30 and 60 kg N ha-1 respectively. The contribution of pre-anthesis N to the grain was 2.2, 3.7 and 5.1 g m-2 when 15, 30 and 60 kg N ha-' were applied respectively. This contribution accounted for 60, 82 and 95% of the total grain N respectively. Results indicated that with greater amounts of N accumulated before anthesis, there was higher remobilization to the grain and less risk of net N losses at maturity, because post-anthesis water deficits developed more rapidly.
Resistance to subterranean clover mottle virus in subterranean clover results from restricted cell-to-cell movement
Authors: Njeru R , Jones RAC , Sivasithamparam K , Jones MGK
Published: November 2004

Subterranean clover mottle sobemovirus (SCMoV) is an important pathogen of subterranean clover (Trifolium subterraneum) pastures in Australia. Cultivars of subterranean clover are susceptible (e.g. Dalkeith, Woogenellup), moderately susceptible (e.g. Green Range), partially resistant (e.g. Goulburn) or highly resistant (e.g. Meteora, Trikkala) to SCMoV. The resistant class does not become systemically infected on sap inoculation, while only a proportion of plants develop systemic infection with the moderately susceptible and partially resistant classes (Wroth and Jones 1992b; Ferris and Jones 1994). These different classes were used to examine the basis of SCMoV resistance using cell biological approaches. Virus levels were quantified at the tissue level by ELISA and at the cell level by counting protoplasts which fluoresced after antibody staining. Three aspects were investigated: (1) initial cell infection, (2) frequencies of cell infection in sap-inoculated leaves and in systemically infected leaves from graft-inoculated plants, and (3, ability of the virus to replicate in isolated protoplasts. Fewer and smaller starch lesions formed in inoculated leaves of a highly resistant cultivar than in those of moderately susceptible and susceptible cultivars. In protoplasts isolated from epidermal cell strips from inoculated leaves, initially the numbers of fluorescing protoplasts were the same for all four classes of cultivars (5-7%). Subsequently, however, the numbers remained unchanged for the two highly resistant cultivars, but increased considerably in the susceptible one used, and to a lesser extent in the moderately susceptible and partially resistant ones. For protoplasts isolated from whole inoculated leaves, the percentage of protoplasts that fluoresced was greatest in the susceptible cultivars used, lower in the moderately susceptible and partially resistant cultivars, and least in the highly resistant ones. All classes became systemically infected when graft-inoculated, but with the systemically infected leaves the proportions of protoplasts that fluoresced were least for the highly resistant and greatest for the susceptible classes. When protoplasts were inoculated with SCMoV in vitro, the proportions which fluoresced were the same (53-56%) for highly resistant, moderately susceptible and susceptible cultivars, showing that resistance was not expressed at the single cell level as an inhibition of virus replication. Because movement of SCMoV was restricted in inoculated leaves of the highly resistant class (starch lesion, epidermal strip and whole leaf data) and in graft-induced systemically infected leaves, it is concluded that the basis of resistance to SCMoV in highly resistant cultivars of subterranean clover is restriction of cell-to-cell movement of the virus.
Seedling vigour and rhizome development in Trifolium ambiguum M. Bieb. (Caucasian clover) as affected by density of companion grasses, fertility, drought and defoliation in the first year
Authors: Hill MJ , Mulcahy C
Published: November 2004

Trifolium ambiguum was grown from seed in a mixture with Festuca arundinacea and Phalaris aquatica at four grass densities under high fertility, and at two intermediate grass densities under low fertility, with frequent or infrequent defoliation imposed from week 15 to week 31, in large pots for 1 year. Selective defoliation of the clover at week 35, and 3-4 weeks drought were imposed on high and low fertility treatments in the post-cutting period. The impact of these treatments was assessed by destructive harvest of shoots, roots and rhizomes. Plant densities of T. ambiguum and grasses were unaffected by the treatments; however, rhizome numbers were reduced by increasing density of grasses, by frequent defoliation, and at high fertility compared with low fertility where grass vigour was very poor. Selective defoliation of T. ambiguum and short-term drought temporarily reduced the contribution of T. ambiguum to harvested herbage, but had no permanent effect on growth rate. Final root and rhizome biomass of T. ambiguum was reduced by increasing density of grass, by frequent defoliation and at high fertility where grass competition was vigorous. We conclude that early growth of T. ambiguum, in particular root and rhizome development, may be better where the density of companion grasses is low, or grass vigour is low due to low fertility, provided soil P and S are not limiting for clover growth. Defoliation in the presence of vigorous grass competition reduces root and rhizome development and may not be effective in minimizing competition. Options for inclusion of T. ambiguum in mixed swards are discussed.