bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors influencing the availability of mineral nitrogen in clay soils of the brigalow (Acacia harpophylla) region of Central Queensland
Authors: Grace PR , MacRae IC , Myers RJK
Published: November 2004

Microbiological and chemical assays were performed on clay soils from woodland (Acacia harpophylla-Casuarina cristata), grassland (Panicurn maximum var trichoglume-Chloris gayana) and cropland (Vigna mungo) in the brigalow region of Central Queensland. Over a 15 month period, the microbial biomass C in the top 3.5 cm of native brigalow woodland soil was on average 3630 8g C g-l, 50% more than an associated perennial pasture and over 400% more than an annually cropped soil. Microbial biomass N (575 8g N g-l) in woodland soil was on average 41% and 270% higher than in pasture and cropped soils respectively and highly correlated with seasonal soil moisture content. Viable counts of bacteria were consistently lower (average 69.2%) in the 0-3.5 cm and 3.5-7.5 cm strata of woodland soil compared with pasture and annual crop sites. Soil NO-3- N levels increased two fold in the upper 3.5 cm of the woodland site during low rainfall periods. This increase may be attributed to a more efficient distribution of mineral N mediated by the increased presence of a fungal population in this community. Leaching may also play a significant role in the distribution of plant available N in the brigalow region as suggested by the inverse relationship N = 54.11-0.67 R (P<0.01), where N is soil NO-3-N (8g N g-l) and R is rainfall in the preceding 3 month period (mm month-1).
Host range, symptoms and effects on pasture production of a Victorian isolate of ryegrass mosaic potyvirus
Authors: Eagling DR , Villalta O , Sward RJ
Published: November 2004

A local isolate of ryegrass mosaic potyvirus (RMV) was identified from a pasture in Leongatha, south-east Victoria. The virus was mechanically inoculated to ryegrass and oats but could not be detected by ISEM in inoculated and symptomless wheat, cocksfoot or barley. Symptoms associated with infection varied between a white mosaic and a brown necrosis. The presence or absence of RMV did not significantly affect the total herbage yields of field plots. However, infection with RMV resulted in reductions in dry weight of 5-50% in the ryegrass component of total herbage yields; the reduction in ryegrass was compensated by increased weed growth. The extent of the reductions in ryegrass associated with RMV infection varied with both species and cultivar. Both the host range study and the herbage yields from the field trial showed that the Victorian isolate of RMV differed from isolates reported overseas.
The nutritive value of subterranean clover herbage grown under irrigation in northern Victoria
Authors: Stockdale CR
Published: November 2004

A series of experiments is described which considered the nutritive value of subterranean clover (Trifolium subterraneum) herbage grown under irrigation in northern Victoria. Digestion studies were undertaken with sheep and dairy cows and the degradation of herbage samples in nylon bags was evaluated. Digestion coefficients were estimated, 1eaf:stem ratios were measured, mineral and amino acid profiles were obtained, and protein degradabilities were assessed. The digestibility and chemical composition of freshly cut subterranean clover herbage was relatively constant until wilting of the herbage in mid spring. With few exceptions, in vivo DM digestibility and nitrogen content were greater than 75% and 3.2%, respectively, and neutral detergent fibre, acid detergent fibre and lignin were less than 40%, 30% and 6%, respectively. The chemical composition of leaves and petioles/stems were very different. The digestibility of the leaf fraction was often much lower than that of petiole/stem, but its nitrogen content was higher. Reasons for this, and their implications, are discussed. Discussed also are the adequacy of herbage minerals and their solubilities. Rumen protein degradability for vegetative herbage ranged from 0.51 to 0.64. Of the plant components, the protein in stems was more degradable than the protein in leaves. The effects of incubation of herbage in nylon bags in the rumen for 24 h on amino acid composition are also discussed.
Genotype × environment interactions in sugarcane. I. Patterns of response across sites and crop-years in north Queensland
Authors: Jackson PA , Hogarth DM
Published: November 2004

Responses of sugarcane genotypes across environments in north Queensland for sugar yield and its components cane yield and sugar content, were examined using pattern analysis methods. The aim was to provide information which could be used in designing efficient selection methods for sugarcane breeding programs. Of particular interest was the comparison of variation in relative performance of genotypes across sites and crop-years. Results from two series of sugarcane trials in north Queensland are presented. In the first series, 65 genotypes were evaluated at four sites and across plant, first ratoon and second ratoon crops. In the second, 52 genotypes were evaluated across four sites and across plant and first ratoon crops. Crops and years were confounded in both series. Crop-years within sites were generally more similar for genotypic responses than environments from different sites. Within most sites the relative ranking of groups of genotypes derived from cluster analysis was similar across different crop-years. However, there were some substantial differences in ranking of the groups between some sites and selection would vary if different subsets of sites were considered. There was little variation among groups in general response to ratoon crop-years. The results indicate that testing across sites is of importance. However, the similarity in information obtained across crop-years within most sites suggests there may be limited gain in testing across multiple crops or years within a particular site.
The mobility and transformation of soil nitrogen and the relationships between soil and plant nitrogen and yield at different times following application of various nitrogen fertilizers to sweet corn
Authors: Salardini AA , Sparrow LA , Holloway RJ
Published: November 2004

The concentration of NH4-N, NO3-N and their sum (mineral N) were monitored 12 times in 1 or 2 weekly intervals in the soil under a sweet corn crop. The samples were taken on the fertilizer band and to depths of 200, 400 and 600 mm. The NO3-N concentration of the sap expressed from the midrib of the leaf opposite and immediately above the primary cob (sap NO3-N) and that of midrib dry matter (midrib NO3-N) were determined weekly. Under the low rainfall and optimized irrigation of this trial the concentration of mineral N in soil to the depth of 400 mm or more was a good predictor of yield response to application of N at 10 of the 12 sampling times. The concentration of either NH4-N or NO3-N in the soil to any depth and the concentration of mineral N in the surface 200 mm correlated with the yield at only a few times of sampling. The concentration of mineral N in the top 200 mm of soil 1 or 2 weeks after top-dressing of N was highly correlated to yield. The concentration of sap NOS-N and midrib NO3-N decreased continuously until harvest. Both these concentrations were significantly correlated with the rates of basal and top-dressed N in most sampling times. These were also strongly correlated to yield 1 or 2 weeks after N top-dressing. Ammonium sulfate, ammonium nitrate and urea gave similar responses in sap NO3-N and midrib NO3-N and in soil nitrogen after 5 weeks when nitrification of fertilizer NH4-N was complete. These observations indicated that soil mineral N, sap NO3-N and midrib NO3-N all offer potential as techniques to predict the yield response of sweet corn to N application. The sap NO3-N test was simpler, quicker, cheaper and more consistent than other tests.
Nutrient uptake and partitioning by zucchini squash, head lettuce and potato in response to nitrogen
Authors: Huett DO , Dettmann EB
Published: November 2004

The effect of N application level on uptake and partitioning of nutrients by zucchini squash (Cucurbita pepo L.) cv. Blackjack, head lettuce (Lactuca sativa L.) cv. Monte110 and potato (Solanum tuberosum L.) cv. Sebago was investigated in sand culture experiments with a stable nutrient supply. Plants were grown during 14 (zucchini squash), 8 (lettuce) and 12 weeks (potato). Five nitrate N levels ranging from 2-36 mol m-3 for lettuce and 2-43 mol m-3 for zucchini squash and potato were applied in a complete nutrient solution. Gamma x quadratic response surface models fitted actual nutrient uptake data (R2> 0 . 9 5 ) . From these models, predicted nutrient uptake, partitioning of nutrients between plant parts and nutrient uptake rates were derived. Nitrogen had a pronounced effect on nutrient uptake of all species. The maximum predicted whole plant (excluding roots) uptake of N and K (parenthesis) was calculated (mol m-3 N) for zucchini squash (19.3, 17.7), lettuce (16.5, 12.1) and potato (12.7, 11.2) respectively. An N deficiency (2 mol m-3)did not result in remobilization of nutrients from vegetative to reproductive growth for zucchini squash and potato. Remobilization of N and K from outer leaves to head occurred for lettuce over the last week of the growth period at all N levels. An N deficiency increased partitioning of N and K by 36 and 54% respectively to reproductive growth for zucchini squash compared with adequate N for fresh yield (14 mol m-3), whereas an N deficiency had a negligible effect on partitioning to reproductive growth for potato. Partitioning, as measured by the ratio of nutrients in fruit, head or tuber to whole plant increased over the growth period, and at final harvest, partitioning was lowest for Ca (0.22-0.24 zucchini squash, 0.21-0.32 lettuce and 0.03-0.09 potato) and highest for K (0.39-0.60 zucchini squash, 0.59-0.68 lettuce and 0.63-0.86 potato). Potato tubers and lettuce head, in contrast to zucchini squash fruit, were dominant sinks for N, K and P.
Acremonium endophytes in perennial ryegrass and other pasture grasses in Australia and New Zealand
Authors: Heeswijck R. van , McDonald G.
Published: November 2004

Many grasses contain asymptomatic fungal endophytes which are now recognised as having a major impact on the performance of pastures in Australia and New Zealand, and elsewhere in the world. The association between the plant and the fungus is regarded as mutualistic, with the host grass able to benefit from endophyte presence through reduced herbivore feeding, increased resistance to insects, improved plant growth and possibly disease resistance. Grazing systems may be disadvantaged, however, as the ingestion of endophyte-infected grasses can be associated with a number of animal toxicoses including ryegrass staggers and fescue toxicosis. There is increasing evidence that the effects of endophyte on the host grass, and consequently on pasture performance and animal production, are mediated by a range of secondary metabolites produced by the plant-fungus interaction. Recent work has shown that a great deal of variation can be found amongst endophyte strains both in the types and amounts of these secondary metabolites produced. This review presents the current status of knowledge on the impact of endophyte on pasture grasses in Australia and New Zealand and attempts to place it in the framework of endophyte research in general. It discusses the potential for harnessing the benefits of endophyte infection, whilst minimizing deleterious effects, through the use of elite endophyte strains which have been isolated from naturally occurring grasses, or modified by the techniques of genetic engineering. It concludes by identifying a number of significant areas which require further research for us to fully understand the plant-fungus interaction and its effects on pasture systems.
The role of condensed tannins in the nutritional value of mulga (Acacia aneura) for sheep
Authors: Pritchard DA , Martin PR , O'Rourke PK
Published: November 2004

Sheep were fed mulga (Acacia aneura) ad libitum and supplemented with 0, 12 or 24 g/day of polyethylene glycol molecular weight 4000 (PEG), with or without an additional supplement of 1.5 g/day of each of nitrogen (N), phosphorus (P) and sulfur (S) (NPS). Supplementation with either 12 g/day PEG or 24 g/day PEG increased dry matter intake by 56 and 78% respectively and clean wool growth per unit surface area by 166 and 178% respectively. Supplementation with 24 g/day PEG increased wool fibre diameter, linear growth rate and volumetric growth rate by 32, 29 and 143% respectively. Sheep receiving 24 g/day PEG retained more N (1.80 g/day) and S (254 mg/day) and digested more N (218 g/kg) and S (229 g/kg) when compared with non-supplemented animals. These parameters were further enhanced when NPS was supplemented in conjunction with 24 g/day PEG. Maximum precipitation (77%) of mulga condensed tannins (CT) occurred at a PEG to CT ratio of 0.7:l.
Lactic acidosis and its effect on wool tensile strength
Authors: Murray PJ , Rowe JB , Speijers EJ
Published: November 2004

An experiment was conducted to test the effect of the feed additive virginiamycin (VM) on lactic acidosis and wool tensile strength in sheep given wheat. The ground wheat grain was given in a slurry by stomach tube in increasing amounts each day up to a maximum of 1 kg per dose or until rumen pH dropped below 5.20. Sixty mature Merino wethers were all fed wheat chaff ad libitum and given the following treatments: 10 control sheep were only fed the basal diet; 10 were given intra-ruminal doses of VM; 20 sheep were given wheat grain intra-ruminally; and 20 sheep were given wheat grain containing VM. Virginiarnycin was given at a rate equivalent to 80 mg/day. All animals were fed chaff for 83 days prior to and for 120 days following the wheat and VM treatments. Rumen pH and L-lactic acid concentration were measured in all 60 sheep from the day that wheat was first given until 3 days after the last wheat drench. Lactic acidosis, defined by a rumen pH of less than 5.2 and rumen lactic acid concentration of greater than 20 mmol/L, significantly decreased staple strength of wool in sheep given the wheat drenches. Inclusion of VM with the wheat grain significantly increased (P < 0.05) the tensile strength of the wool compared with the effect of wheat on its own. Reduction in wool strength was more closely correlated with a reduction in feed intake in the days following the lactic acidosis than with either rumen pH or the concentration of rumen lactic acid.
Possible contribution of protozoa to differences in rumen metabolism between cattle breeds
Authors: O'Kelly JC , Spiers WG
Published: November 2004

Brahman (B) and Hereford (H) cattle were used to study protozoal population density of ruminal fluid (RF) in relation to some aspects of rumen and body metabolism. Steers were fed restricted intakes of lucerne hay (HQ) or low-quality hay (LQ) in each of eight experiments. In the 8 h period following the once-daily feeding of HQ the number of entodiniomorphs declined by 50%, while the number of holotrichs increased by 60% before reducing to pre-feeding levels. There were no significant rises and falls in the numbers of protozoa of steers fed LQ once daily nor in those fed either HQ or LQ at hourly intervals. The numbers of entodiniomorphs, dasytrichs, total protozoa, pH and bacterial content of RF were higher and rumen temperature lower in B than in H. Urinary allantoin excretion used as an index of the total microbial population in the rumen distinguished between diets but not between breeds. The concentrations of propionic, butyric, isobutyric and isovaleric acids in RF and of glucose in plasma were higher in B than in H. The concentrations of all classes of long-chain fatty acids contained in the protozoa and bacteria of RF and of cholesterol and essential fatty acids in plasma were higher in B than in H. The amount of dry matter disappearing from nylon bags in the rumen of steers fed HQ did not differ between breeds, but was higher in B than in H fed LQ. Elevation of pH to peak values in RF with an accompanying disappearance of protozoa and volatile fatty acids during fasting from either HQ or LQ occurred more rapidly in B than in H. The plasma concentrations of non-esterified fatty acids were higher in B than in H during fasting. It is proposed that at the same level of intake of either HQ or LQ: (1) the higher protozoal population density in RF of B contributes to quantitative breed differences in the end products of digestion, (2) that B achieve and maintain a higher body weight because more metabolizable energy and essential nutrients are supplied from the rumen to their body tissues, and (3) after the same period of feed deprivation B have fasted for a longer period of time because the residual feed in their rumens is fermented at a more rapid rate.
Carotenoid and retinol concentrations in serum, adipose tissue and liver and carotenoid transport in sheep, goats and cattle
Authors: Yang A , Larsen TW , Tume RK
Published: November 2004

Carotenoid and retinol concentrations were determined in various tissues of sheep, goats and cattle, ruminants known to have widely different levels of pigmentation of their adipose tissues. An objective assessment of fat colour confirmed the whiteness of sheep and goat fat compared with that of cattle. No G-carotene was detected in the serum or fat of sheep and goats, but it was the predominant carotenoid present in the serum and fat of cattle. The major pigment present in serum and fat of sheep and goat was lutein, although its concentration was only 5-10% of that found in cattle. G-carotene was present in the liver of all three species with the highest concentration in cattle. Although lutein was the only carotenoid found in the serum and fat of sheep and goats, it could not be detected in their livers. The concentrations of retinol in serum and fat were similar for each species, but the liver of sheep had about three times the retinol concentration of the liver of goats and cattle. The transport of carotenoids in plasma was investigated. In sheep and goats, the pigments were associated mainly with very low density lipoprotein (VLDL) and low density lipoprotein (LDL), whereas in cattle, high density lipoprotein (HDL) was the major lipoprotein fraction involved.
Productivity of three crossbred ewe types mated naturally at 8-monthly intervals over two years
Authors: Fogarty NM , Hall DG , Atkinson WR
Published: November 2004

Productivity is reported for 175 Booroola MerinoxPoll Dorset (BD), 288 Trangie Fertility MerinoxPoll Dorset (TD) and 248 Border LeicesterxMerino (BLM) ewes joined three times (February, October and June) in 2 years. Overall joining in February resulted in higher performances (153�3% lambs born, 118�3% lambs weaned, 24.7�0.6 kg weight of lamb weaned, per ewe joined) than were obtained following October and June joinings (129�4% born, 93�3% weaned, 15.3�0.5 kg weight weaned per ewe joined). The mean number of lambings per year was 1.28�0.02 with an annual lambing rate of 211�4% lambs born and 160�3% lambs weaned. For lambs born, BD ewes were consistently higher than the other ewes, with BLM ewes having fewer lambs born from October and June joinings (P < 0.01). From the October joining, TD ewes had a higher weaning rate than BD ewes which were higher than BLM ewes (P < 0.01), but ewe type was not significant for the other two joinings. Over the three joinings there were no differences between the ewe types in the number of lambings per year or percentage of lambs weaned, but BD had more lambs born (239� 7%) than TD (212�5%) and BLM (181�5%). Analyses of the components of reproduction that contributed to overall lamb production showed that although more than 95% of ewes expressed oestrus in each season, fertility and litter size were higher from the February joining, while lamb survival was lower following the June joining. Ewe crossbred type was significant (P < 0.01) for litter size in all seasons. Litter size for BD ewes was 1.9 to 2.0, and for TD ewes was 1.6 to 1.7 at all seasons, while that for BLM ewes was 1.7 from February and 1.2 and 1.4 from October and June joinings respectively. The effects of ewe liveweight at joining and liveweight gain over joining were variable over the three joinings, but were generally small. BD ewes carrying the F gene tended to have a higher percentage of lambs born and lower percentage of lambs weaned than non-carriers. There was also a decline in lamb production, especially fertility and lamb survival, with ewe age among BD and TD ewes. Implications for production systems in the lamb industry are discussed.
Influence of rainfall and temperature on sensitivity of barley (Hordeum vulgare) to chlorsulfuron
Authors: Lemerle D
Published: November 2004

Effects of rainfall and temperature on the sensitivity of barley grown in low pH soil to chlorsulfuron applied post-emergence were examined under weed-free conditions. Chlorsulfuron at 15 g a.i. ha-1 applied to barley grown under a rainshelter in the field caused reductions in barley height (16%), leaf area (53%), shoot dry matter (23%) and tiller number (23%) at anthesis if simulated rainfall (5 or 10 mm) occurred within 7 days after treatment (DAT). Chlorsulfuron had little effect on barley when rain did not fall until 14 DAT. No responses of barley to chlorsulfuron were detected at maturity in any treatments, due to a dry end of season which prevented full expression of yield potential of untreated controls. Chlorsulfuron applied to barley growing at temperature regimes of 0/10, 5/15, 10120 and 15/25�C (night/day) for 7 DAT caused similar reductions at all temperatures in barley root DM, height, leaf area and tillering in cvv. Schooner and Grimmett grown in growth cabinets. Nodal roots were more sensitive to chlorsulfuron at high than at low temperature. Barley responded similarly to chlorsulfuron when grown at temperatures of 2/11 or 6/16�C (or combinations of both) for up to 14 DAT. Incidence of rainfall within 7 DAT is critical in causing damage from chlorsulfuron in this environment, although damage may not always result in yield loss at maturity.
Water use and productivity in sub. clover and murex medic swards. II. Seed production
Authors: Blumenthal MJ , Ison RL
Published: November 2004

A field experiment was established at Forbes in central-west N.S.W. to investigate the hypothesis that the pattern and efficiency of water use varies between genotypes of both (Trifolium subtewaneum) and murex medic (Medicago murex), and that this would affect the success of these genotypes in this environment. To test this hypothesis the productivity of two lines of M. murex (CD26 and CD53) and four cultivars of T. subtewaneum (Seaton Park and Woogenellup, and two recently released cultivars, Junee and Dalkeith) were compared. Genotypes were grown both with and without irrigation and soil water was monitored for the duration of the field experiment (1987-1989). Seed production in cv. Dalkeith was higher than in all other genotypes when grown with or without irrigation, and would thus be less inclined to suffer from annual legume decline than the other genotypes studied. Seed yield was very sensitive to small changes in available soil water, especially in sub. .clover cv. Junee, where water shortage over a short period during burr formation resulted in marked yield reductions. Murex medic seed yield was negatively correlated with water use. Seed size was the yield component most affected by available soil water in all sub. clover genotypes except cv. Dalkeith, where plant number was most highly correlated with seed yield. Implications for the persistence of annual legumes and the role of water use models are discussed.
Restrictions to root growth limit the yield of shoots of irrigated white clover
Authors: Blaikie SJ , Mason WK
Published: November 2004

Pasture yields in irrigated northern Victoria are low. This experiment examined the degree to which restrictions in root growth explained the low shoot yield of white clover (Trifolium repens) grown in irrigated soils. Soils were collected as intact cores from various field sites producing from well above to well below average pasture growth. A vegetative cutting of white clover was planted into each soil core and the growth of the shoot and root systems was monitored over a 38 day period by a series of destructive harvests. All plants were managed to minimize water, oxygen or nutrient stresses. There were large effects of treatments on the productivity of plants with growth in the soil cores reflecting the field productivity of each soil. This suggested that despite managing the cores carefully, it was not possible to overcome the limitations to plant yield that occur in these soils in the field. The most productive soil was one for which the profile had been physically modified. Measures of soil physical properties (bulk density, air-filled porosity, volumetric water content, penetrometer resistance) were collected from the field sites when the soil was at field capacity, but it was not possible to identify which of these were associated with the differences in productivity between soil core treatments. No measures of the soil physical conditions were made in the cores, but it is possible that the field data did not accurately reflect conditions in the soil cores, particularly during each daily watering. There were strong correlations between shoot and root production whether measured in terms of dry weight or morphological characteristics. The most important characteristic of highly productive soil was the capacity to support the rapid proliferation of a large root system. Improved forage yield will only be possible if the potential for white clover to produce roots in irrigated soils is increased.
Carcass composition in weight-selected and control bulls from a serial slaughter experiment
Authors: Morris CA , Baker RL , Bass JJ , Jones KR , Wilson JA
Published: November 2004

Bull calves were sampled at random at weaning from the 17th calf crop of an Angus herd selected for yearling weight (AS1) and from its contemporary control herd (ACO). Thirty animals per herd were slaughtered in groups of five per herd at intervals, from 7 to 25 months of age. Live weight and scrotal circumference were taken on the day before slaughter, along with a blood sample for analysis of plasma insulin-like growth factor-1 (IGF-1) and testosterone concentration. The left side of each carcass was dissected into saleable meat, bone and trimmed fat components. Live weights and hot carcass weights of AS1 animals were, on average, 16.8 and 17- 6% greater respectively than those of ACO animals. Allometric comparisons of the carcass composition data (log-log regressions) showed no significant herd differences in the rate at which saleable meat, bone or trimmed fat weights increased with carcass weight. Adjusted weights of bone, however, were significantly greater in the AS1 than ACO herds (P < 0.05). There were significant herd differences in the weights of kidney, liver and testes, in scrotal circumference and in the concentration of IGF-1, but these disappeared after adjustment for live weight. On an adjusted basis, heart weight was 6.1% greater in the AS1 than the ACO herd (P < 0.05).
Cell proliferation in the wool follicles of fleeceweight selected and control Romney rams
Authors: Kelly KE , Haris PM , Birtles MJ , Dellow DW , Hall AJ
Published: November 2004

Two year old Romney rams from the Massey University fleeceweight-selected (FW) and control (C) lines, five from each line, were given arterial catheters into a branch of the deep circumflex artery on each side of the sheep, to permit local infusion into patches of skin on each lateral abdominal flank. One side of each sheep was infused with saline to give a direct FW v. C comparison, while the other side was infused with low levels of either growth hormone, thyroxine, prolactin or insulin for 4 days. At the end of the infusion period, biopsy samples were taken from each flank for measurement of follicle activity, particularly bulb cell proliferation using intracutaneous injections of 5-bromo-2'-deoxyuridine (BrDU). After a period of recovery, the saline and treated sides were reversed and another series of infusions were performed and biopsies undertaken. Wool from the FW sheep had greater fibre length growth rate and fibre diameter than the C wool (P < 0.05). This was associated with larger follicle bulbs (P < 0.05) and greater numbers of BrDU labelled cells (P < 0.05) in the bulbs of the FW skin. In a restricted number of samples from two sheep, where BrDU was successfully given as repeated intracutaneous injections into the same site (one at 72 h and one at 6 h prior to biopsy), 55-60% of the numbers of BrDU cells in a section of bulb appeared in a section of the shaft of the same follicle. When converted to three dimensions, the efficiency of labelled bulb cell movement into the shaft was 30-40%. Hormonal infusions showed few significant effects with the restricted numbers of animals in each treatment. Thyroxine reduced the size of follicle bulbs (P <0.05) and the numbers of labelled bulb cells in skin from the infused area.
Quantitative animal nutrition and metabolism: a general review
Authors: Armstrong DG
Published: November 2004

Examples of increasing productivity of livestock enterprises over the last three to four decades, and the contribution to such advances, of scientific knowledge including that of the nutrition of farm livestock are referred to. Space limitations neccessitate restricting the review to consideration of ruminant livestock, with particular emphasis on ruminant digestive processes, on milk synthesis and on certain aspects of energy metabolism. Factors affecting the supply of amino acids to the host animal are referred to. The importance of synchronising N and energy supply to the rumen microorganisms to maximize microbial protein synthesis is emphasised and the need for knowledge of the extent to which particular feed proteins escape fermentation within the rumen. Concerning milk synthesis, the importance of an adequate supply of glucose or glucose precursors is mentioned as are the causes of the low milk fat syndrome. Limitations to existing knowledge of amino acid supply and milk protein synthesis are noted. Finally, aspects of ruminant energy metabolism studies are considered; particular stress is given to the importance of energy transactions in the intestinal wall as a major contributor to overall heat increment.
Quantitative ruminant nutrition — a green science
Authors: Leng RA
Published: November 2004

Knowledge of quantitative digestion and metabolism in ruminants was developed most rapidly when isotope dilution techniques became easy to apply, facilitated by improved instrumentation and mathematical approaches. The Armidale group led by Professor E. F. Annison and Dr D. B. Lindsay were at the forefront of these developments in the late 1950's. Since then knowledge in this area has developed at an ever increasing rate. The data that accumulated from the quantitative approach led to simple or complex models of animal digestion, metabolism and growth. These in turn led to much questioning of the dogma of feed evaluation and feeding standards as they applied in practice, especially for ruminants fed on poor quality forages. The knowledge that developed has clearly shown that the way toward substantial increases in productivity of ruminants on forage based diets is through the balanced nutrient approach that considers the efficiency of the rumen ecosystem and the availability of dietary nutrients post-ruminally. With increasing emphasis on quality-beef markets at the present time, it seems likely that the time is ripe for application of much of this knowledge. The major breakthroughs have come about by recognition of the nutrients required to balance a ruminant's diet where the animal depends on the end-products of rumen fermentation (i.e. on a forage-based diet). When this is achieved, the increase in efficiency of use of nutrients lifts the overall nutrition of the animal to a level that is well above that predicted from feeding standards, based on the metabolizable energy content of the supplement or the total diet. This understanding, together with the stoichiometry of rumen fermentation, has indicated an important approach to help ameliorate the greenhouse effect, that is, lowering of enteric methane production per unit of feed intake or per unit of animal products from ruminants by strategic supplementation.
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.
Nutrient balance in the diet of grazing dairy cows
Authors: Kellaway RC , Tassell RJ , Havilah E , Sriskandarajah N , Andrews A
Published: November 2004

A method is described for estimating the nutrient content of pasture selected by grazing cows. The method is non-invasive and suitable for use on commercial farms. Results from use of the method are reported for studies on a commercial farm over a period of 29 months. Confidence limits were calculated for estimated nutrient contents of pasture eaten. Estimated nutrient contents then were compared with recommended nutrient contents for high-yielding cows. Significant deficiencies of energy, protein, Ca, P and Na were common. Seasonal trends in nutrient content of pasture eaten are reported, together with selection differentials between pasture eaten and pasture available.
Hormonal regulation of hepatic glycine oxidation
Authors: Jois M , Brosnan JT
Published: November 2004

Hormones which regulate hepatic oxidation of glycine include glucagon, catecholamines and vasopressin. The stimulation of oxidation of glycine by glucagon requires cyclic nucleotidedependent phosphorylation of one or more cytosolic proteins and does not involve mobilization of calcium from intracellular stores. The stimulation of glycine oxidation by catecholamines and vasopressin, on the other hand, appears to involve calcium mobilization. While calcium has direct effect on mitochondrial glycine oxidation, the link between phosphorylation of cytosolic protein(s) and mitochondrial glycine oxidation is not known. The stimulation of glycine oxidation by hormones can be demonstrated in mitochondria isolated from rats treated with hormones prior to sacrifice. Both the effects of glucagon and calcium are evident in isolated mitochondria only when inorganic phosphate is included in the medium. These findings are discussed in relation to the regulation of hepatic glycine oxidation.
A simulation model of kenaf for assisting fibre industry planning in northern Australia. V. Impact of different crop traits
Authors: Muchow RC , Carberry PS
Published: November 2004

The production potential of rainfed kenaf in the Northern Territory (NT) (latitude 12-15�S.) has been assessed using a growth simulation model for the cultivar Guatemala 4. However, this raises the important question of how well-suited is this cultivar, and what are the likely yield gains which might be obtained by breeding or selecting a different cultivar. Answering these questions with conventional experimentation would be expensive, given the variable yield response among seasons associated with rainfall variability in the NT. Accordingly, the kenaf growth simulation model NTKENAF was used in conjunction with long-term climatic data for two sites in the NT to assess the value of different plant traits relative to Guatemala 4, that are potential selection criteria in plant breeding. Extending the duration from sowing to flowering resulted in relatively small gains in stem yield over Guatemala 4, but substantial yield losses were predicted by using an earlier flowering cultivar. Increasing the efficiency of water use (higher transpiration efficiency) greatly increased yield, and was the most risk-efficient crop improvement strategy. Unfortunately, the prospects for improving transpiration efficiency of kenaf by plant breeding remain uncertain. Increasing the amount of water available for crop growth by greater extent of soil water extraction had little effect on yield in this water-limited environment. Changing the yield potential of kenaf by altering the photosynthetic capacity (higher radiation use efficiency) was risk-efficient in some situations, but the mean yield change was relatively small. It is concluded from the simulation analysis, that the standard cultivar Guatemala 4 is well-suited to the NT environment.
Field studies of cadmium in potatoes (Solanum tuberosum L.) I. Effects of lime and phosphorus on cv. Russet Burbank
Authors: Sparrow LA , Salardini AA , Bishop AC
Published: November 2004

Field experiments were conducted at three sites on basaltic krasnozems to examine cadmium (Cd) responses of Russet Burbank potatoes to different rates of broadcast lime and banded phosphorus (P). Double superphosphate (DSP, containing 15 and 90 mg Cd kg-1) and triple superphosphate (TSP, 12 mg Cd kg-1)) were the sources of P. In a fourth experiment, lime was banded with the basal fertilizer. Despite producing a range of topsoil pH (1:5 H20) of 5.2 to 7.1, broadcast lime had no effect on tuber Cd concentrations. Lime had no effect when banded with the basal fertilizer, and the practice did not adversely affect yields. With broadcast lime, Cd availability from the fertilizer band may have been unaffected. However, there were also no lime x P interactions at any site, suggesting that lime also had no effect on the availability of Cd in the soil. It is possible that Tasmanian krasnozems, with their high organic matter and iron oxide content, restrict the availability of Cd in the soil such that pH change exerts little net influence on Cd availability. Increasing amounts of Cd applied in P fertilizer increased tuber Cd concentrations significantly, but the increases were less per unit of P than those found previously when TSP with 151 mg Cd kg-1) was used.
Field studies of cadmium in potatoes (Solanum tuberosum L.). Response of cvv. Russet Burbank and Kennebec to two double superphosphates of different cadmium concentration
Authors: Sparrow LA , Salardini AA , Bishop AC
Published: November 2004

Separate field experiments were conducted with Russet Burbank and Kennebec potatoes on a basaltic krasnozem where tuber cadmium (Cd) responses were examined over three rates of banded phosphorus (P), supplied as double superphosphate (DSP) containing either 15 or 90 mg Cd kg-1. In both cultivars, tuber Cd concentrations increased with rate of DSP. This response was due more to the amount of P supplied in the DSP than the amount of Cd supplied in the DSP and may be a result of banded P encouraging root proliferation in the fertilizer band. Even with DSP at 15 mg Cd kg-1, Cd additions at rates of DSP needed for high yields were 6-20 times higher than corresponding rates of Cd removal in tubers. Examination of data from all studies of Cd in Russet Burbank on Tasmanian krasnozems showed a significant relationship between petiole and tuber Cd concentrations, but the estimation of a petiole concentration associated with the critical tuber Cd concentration in Australia was subject to unacceptable uncertainty due to variation between sites.
Fleece rot and body strike in Merino sheep. VI. Experimental evaluation of some physical fleece and body characteristics as indirect selection criteria for fleece rot
Authors: Raadsma HW
Published: November 2004

Indicators of staple thickness, staple weight, staple density, wool weight cm -2, crimp frequency, dust penetration, fibre diameter (mean, variability), birthcoat score, and neck and body wrinkle were evaluated for their suitability as indirect selection criteria against fleece rot and body strike. The fleece traits were assessed in 949 Merino ewe hoggets representing the progeny from 134 sires in 15 contemporarily managed flocks. Fleece rot and body strike were assessed following experimental induction. In decreasing order of importance, variability (s.d.) in fibre diameter, average staple thickness, crimp frequency, variability (c.v.) in fibre diameter, mean fibre diameter, birthcoat score, staple density, variability in staple thickness, staple weight, and neck wrinkle score, accounted for a significant component of the variation in liability of sheep to fleece rot. Body wrinkle, variability (c.v.) in staple thickness, staple length, dust penetration, and wool weight cm-2 were not important. Based on combined estimates of the heritability of the indicator trait and its genetic correlation with fleece rot, variability in fibre diameter (s.d.) and birthcoat score showed the highest potential as indirect selection criteria. Variability in fibre diameter (s.d.) also showed a similar scope for selection against body strike. Indicators of mean staple thickness, crimp frequency, dust penetration and wrinkle score showed little or no scope for indirect selection against fleece rot or body strike. The role of variability in fibre diameter (s.d.) as an indirect selection criterion for fleece rot and body strike in designed breeding programmes which include other important objectives, will need to be further evaluated, given an undesirable genetic correlation with clean fleece weight. High between-flock correlations were observed for a number of fleece traits and susceptibility to fleece rot. Susceptible flocks were characterized by fleeces with longer, heavier, thicker staples with a lower crimp frequency, and higher fibre diameter with a higher variability. Predicting the susceptibility of flocks to fleece rot and body strike, through a between flock index based on the measurement of simple fleece traits, is suggested.
A comparison of fatty acid profiles and carcass characteristics of feedlot steers fed canola seed and sunflower seed meal supplements protected from metabolism in the rumen
Authors: Ashes JR , Thompson RH , Gulati SK , Brown GH , Scott TW , Rich AC , Rich JC
Published: November 2004

The effect of feeding protected canola seed (PCS) and protected sunflower seed meal (PSM) supplements on the fatty acid profile and carcass characteristics of feedlot steers was examined. Fifty Hereford cross steers, average weight of 290 kg, were assigned to five groups of 10 and fed the following barley based concentrate rations for 133 days: I, control (containing 15% untreated sunflower seed meal (SSM)); 11, PSM 15%; 111, PCS 10%; IV, PSM 15% plus PCS 10%; V, PSM 15% plus PCS 15%. The inclusion of PCS, with and without PSM, increased the proportion of Cis unsaturated fatty acids in the subcutaneous, perirenal and omental fats; there were threefold increases in the proportion of linoleic (18: 2) acid, fivefold increases in linolenic (18 : 3) acid and smaller increases in the proportion of oleic acid (18 : 1). There was a 20-25% reduction in the proportion of palmitic acid, and the largest decrease was observed in the adipose tissue of steers receiving 15% PCS in the diet. Joint feeding of PCS and PSM significantly increased the dressing percentage of carcasses in Groups IV and V and fat depth in Group IV.
Effect of trenbolone acetate alone and in combination with oestradiol-17β for reducing weight loss in cattle
Authors: Hunter RA , Johnson CG , Frisch JE
Published: November 2004

The effect of various doses of trenbolone acetate, either atone or in combination with oestradiol-17G, on liveweight loss of steers fed restricted amounts of low-quality roughage was determined in a series of experiments. It was found that for steers of 350-400 kg liveweight, a dose of at least 300 mg trenbolone acetate had to be used for significant reduction of the rate of weight loss. Treatment with 300 and 400 mg trenbolone acetate significantly (P < 0.01) reduced concentrations of plasma urea-N. It was also shown that steers grazing dry season pasture and implanted with 300 mg trenbolone acetate lost significantly (P < 0.001) less weight than their untreated counterparts (-8 v. -14 kg). Regardless of dose, trenbolone acetate in combination with oestradiol-17P did not significantly reduce the rate of weight loss or plasma urea-N concentration. The importance of these results in terms of the likely use of trenbolone acetate in cattle in the northern Australian dry season is discussed.
Defoliation and moisture stress influence competition between endophyte-free tall fescue and white clover, birdsfoot trefoil and Caucasian clover
Authors: Hill MJ , Hoveland CS
Published: November 2004

TOsceola white clover, AU Dewey birdsfoot trefoil, Rhizo Caucasian clover and Triumph tall fescue were grown in 2:1 and 1:2 grass legume mixtures, and in monocultures of each species, and defoliated at intervals of 3 and 6 weeks, with unrestricted watering, and two cycles of water stress in a glasshouse pot trial. Competition from tall fescue had a greater effect on legume performance than the cutting or moisture stress treatments. Caucasian clover was more severely affected by competition from tall fescue than either ladino clover or birdsfoot trefoil. Roots of Caucasian clover did not branch and spread amongst the root mass of tall fescue in the same manner as ladino clover. The legumes always exhibited lower leaf water potentials under moisture stress than did tall fescue, and ladino clover made up a greater proportion of the mixtures under 3-week cutting and adequate moisture. We concluded that while ladino clover and birdsfoot trefoil ombined well with tall fescue, the establishment and vigour of Caucasian clover could be very sensitive to the sowing density of companion grass species, particularly on shallow soils with restricted rooting depth.
Radiation interception, radiation use efficiency and growth of barley cultivars
Authors: Goyne PJ , Milroy SP , Lilley JM , Hare JM
Published: November 2004

Dry matter production and utilization of photosynthetically active radiation (PAR) was studied for barley (Hordeurn vulgare L.) in the field at Hermitage Research Station, Qld. In 1990, four cultivars (Gilbert, Tallon, Grimmett, Skiff) were sown at three times and grown with non-limiting soil moisture. In 1991, soil moisture limitations were imposed on one sowing of the cultivar Grimmett. The radiation extinction coefficient (k) was 0.41�0.02 and did not vary with cultivar, time of sowing or soil moisture availability. Radiation use efficiency (RUE) (based on absorbed PAR and above-ground dry matter) did not change with time of sowing but did vary between cultivars. RUE was highest for Gilbert (2.90�0.10 g MJ-1), while the other three cultivars averaged 2.60�0.04 g MJ-l. RUE of Grimmett was significantly lower in 1991 (1.48�0.07 g MJ-1) than in 1990 (2.60�0.07g MJ-1), but soil moisture differences in 1991 did not significantly affect RUE. Several factors with possible links with RUE were examined and discussed. Of the variables examined those which showed the strongest relationships with RUE were average daily vapour pressure deficit and average daily minimum temperature.