bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of progressive defoliation of a grass sward on the eating behaviour of cattle
Authors: Chacon E , Stobbs TH
Published: November 2004

Changes in sward structure, diet selection and eating behaviour of cattle (grazing time, biting, bite size and estimated intake) were studied as contrasting swards of Setaria anceps cv. Kazungula were progressively defoliated. In one experiment three replicates in time of 9-week autumn regrowths were grazed down over 14-day periods, and a further two time replicates of 5-week regrowths were grazed down over 10-day periods in spring. A second experiment investigated the causes of changes in grazing behaviour. In the early stages of defoliation cows selected mainly leaf (> 80%) from the uppermost layers of the sward. As the quantity of leaf on offer became less, the animals took smaller bites, increased the time spent grazing (up to a mean of 646 min in autumn and 593 min in spring), and increased the rate of biting (up to 62.4 and 59.4 eating bites min-1 in autumn and spring respectively) and the total number of eating bites (up to 39,500 and 34,000 day-1 in autumn and spring). At this stage bulk in the rumen appeared to limit intake of herbage. Peak grazing time and highest number of bites occurred when leaf yields averaged 1000 kg dry matter ha-1, although total yield and dry green yield varied between swards. In the later stages of defoliation, grazing time and eating bites declined and, together with a reduced bite size (as low as 66 and 79 mg organic matter per bite eaten in experiments 1 and 2 respectively), resulted in a low intake of herbage. Stem and senescent material in the diet increased up to 77%, but bulk was not the major cause of reduced intake. Nitrogen and mineral levels appeared sufficient for maximum intake. Low leaf density prevented animals harvesting large quantities of herbage from the swards. It was concluded that leaf is the most important component of the sward and that leaf yield, percentage leaf and bulk density of green material (leaf and stem) are the major sward factors influencing intake by grazing animals.
The effects of frequency and extent of defoliation, summer irrigation, and fertilizer on the production and survival of the grass Danthonia caespitosa Gaud
Authors: Hodgkinson KC
Published: November 2004

The effects of extent and frequency of defoliation on the growth and survival of Danthonia caespitosa were measured in a series of field experiments. Additional treatments, of summer irrigation and application of nitrogen and phosphorus fertilizer, were included in some of the experiments to assess how they modified the effects of defoliation. During the summer, complete defoliation increased the shoot yield of plants which had not been irrigated, but yield was decreased in the irrigated treatments. Frequent, partial defoliation increased yields of irrigated plants but decreased yields of plants not irrigated. Depression of yields was caused by both tiller death and reduced regrowth of individual tillers. In an experiment lasting 2 years, plants were completely defoliated monthly, bimonthly or tri-monthly or left intact, and shoot yields, tillering characteristics and plant survival under the treatments were compared. Monthly defoliation depressed yields and rate of tillering and accelerated the death rate of plants, particularly during the summer and autumn periods. Plants also died when cut bimonthly but the rate was slower. Plants irrigated during the first summer generally died at a faster rate than plants not irrigated. Tillering was more rapid during the autumn and early winter months. Midwinter application of fertilizer to plants cut bimonthly greatly stimulated shoot yields and seed production in the spring but not in the following year. Examination of tiller apices showed that floral induction took place prior to the beginning of July. Many apices were elevated above the 'grazing level' by early September, and flowering and seed set occurred in October.
Studies on recycling spent compost for mushroom cultivation
Authors: Nair NG
Published: November 2004

Natural weathering of spent compost for 2 years resulted in a lowering of electrical conductivity which enabled it to be used as a casing material in mushroom cultivation. Spent compost and peat moss had different optima of electrical conductivity values for normal mushroom production. Relatively high levels of soluble salts such as calcium nitrate and calcium chloride reduced the yield of mushrooms. The addition of rice hulls and peat moss to spent compost overcame the effect of sealing caused by watering. These amendments improved aeration of the casing layer and increased the number of pseudomonads. Pasteurized, spent compost, aged for 2 years, at a moisture level of 65% saturation, was shown to be a suitable casing material for obtaining relatively good yields of mushrooms. It is suggested that this material may find an application in commercial cultivation of mushrooms.
Site variation in the deposition of linoleic acid in adipose tissue of cattle given formaldehyde-treated sunflower seed
Authors: Hood RL , Thornton RF
Published: November 2004

Fatty acid analyses were carried out on adipose tissues from several anatomical locations in steers raised either under grazing conditions or on a diet containing 30% of formaldehyde-treated sunflower seed. The level of linoleic acid deposited in adipose tissue of steers receiving the protected sunflower seed (PSS) varied from 9.2% in the brisket to 20.4% in the channel fat. A technique which permits the simultaneous calculation of both the extent of deposition of exogenous lipid at any anatomical location, and the degree of in vivo protection of the seed oil from ruminal hydrogenation, is described. By means of this technique, the PSS was calculated to be 71.6% protected from in vivo hydrogenation, and fat from the PSS was found to be preferentially incorporated into the internal depots and the tissues of the forequarter rather than those in the hindquarters of the steers. This technique has application in the determination of patterns of deposition of dietary fat at different stages of development and in different breeds of cattle and sheep.
Temperature effects at three development stages on the yield of the wheat ear
Authors: Warrington IJ , Dunstone RL , Green LM
Published: November 2004

Temperature effects on the growth and yield of wheat (cv. Gamenya) were studied in controlled environments under three day/night temperature regimes (viz. 25/20, 20/15 and 15/10°C) and at three stages of development, viz. vegetative, ear development and grain growth stages. The most important temperature effects were found during the ear development phase. Plants grown at low temperature at this time had long culms, large flag leaves and more potentially fertile florets in each spikelet. The number of florets which produced harvestable grains, and the weight of these grains at maturity, were affected by temperature during the grain growth stage. Temperature prior to floral initiation was not of major importance to final ear weight in this variety, but it did have an effect on the number of mature ears present at harvest. Grain weight per ear at maturity was found to be highly correlated with the number of grains set (r = 0.96), and hence variation in grain number accounted for most of the variation in ear grain weight. In those treatments where grain numbers were not markedly depressed by the temperature treatments, a hlgh positive correlation was found between flag leaf area duration and total grain yield (r = 0.73).
Survival of annual ryegrass (Lolium rigidum Gaud.) seed in a Mediterranean type environment. II.* Effects of short-term burial on persistence of viable seed
Authors: Gramshaw D , Stern WR
Published: November 2004

Two seed components, dark dormant and non-dark dormant, were identified in experiments in which germination and survival of seeds buried in soil were examined. These comprised c. 10–20% and 80–90% of the seed population respectively. About 12% of the dark dormant seeds (1–2% of total seed population) germinated when first buried between 0 and 2 cm depth, and subsequent disturbance of the soil on two occasions caused further germinations. In contrast, all non-dark dormant seed rapidly germinated when buried at 2 cm; however, germination of non-dark dormant seeds decreased progressively as burial depth increased, until at 11 and 14 cm no seed germinated. In one experiment, seed that failed to germinate when buried at 14 cm was found to germinate readily if transferred to a depth of 2 cm without soil disturbance. This indicated that dormancy was enforced, rather than induced, in seeds buried relatively deeply for short periods. In these experiments soil temperature and moisture were favourable for germination, and it is suggested that an unfavourable gaseous environment around deeply buried seeds is the factor enforcing dormancy. The implication of these findings for the persistence of annual ryegrass in the pasture-crop rotation is discussed.

_____________________
*Part I, Aust. J. Agric. Res., 28: 81 (1977).
The detection of prune dwarf virus in peach trees affected with peach rosette and decline with Golden Queen peach as an indicator, and the distribution of the virus in affected trees
Authors: Smith PR , Stubbs LL , Challen DI
Published: November 2004

Golden Queen peach was a better indicator than Italian prune and Elberta peach seedling for detecting prune dwarf virus (PDV) in peach trees naturally infected with peach rosette and decline disease. Both cv. Golden Queen and Elberta seedling had lower probabilities of failing to detect PDV, but the symptoms produced were mild and transient in Elberta seedling compared with the severe and persistent symptoms produced in cv. Golden Queen. The virus was transported in the phloem, but not xylem, of affected peach trees and moved into limbs adjacent to the initially affected limb within 2 months of flowering.
Effects of Trichostrongylus colubriformis (Nematoda) on the nutrition and metabolism of sheep. III.* Digesta flow and fermentation
Authors: Roseby FB
Published: November 2004

The effect of infection with Trichostrongylus colubriformis on the characteristics of digesta flow and fermentation was studied in young Merino sheep fed on a pelleted roughage diet at 540 g/day.The pattern of elimination of 51CR-EDTA was compared in six infected and six paired control sheep. The half-times of the water-soluble marker in rumen and caecum-proximal colon were similar, but the transit time of marker through the tubular intestine was significantly greater in the infected sheep. The distribution of digesta and the pattern of fermentation in the digestive tract was compared in three infected and three paired control sheep under general anaesthetic. The dry matter, water and nitrogen contents of the rumen were decreased, while those of the abomasum, smail intestine and caecum-proximal colon were increased, in infected sheep. The concentrations of volatile fatty acid and ammonia in the digesta indicated that fermentation in the large intestine was increased by infection. A flow diagram was developed to describe the specific derangements of nitrogen metabolism caused by infection with T. colubriformis. It was concluded that the combined effects of increased leakage of endogenous protein into, and reduced efficiency of absorption from, the small intestine resulted in a reduction in the net absorption of amino acid nitrogen by infected sheep. The corresponding increase in microbial deamination of protein in the large intestine increased the availability of ammonia, but very little of this ammonia was used for amino acid synthesis as most was converted to urea and excreted.

_________________
*Part II, Aust. J. Agric. Res., 25: 363 (1974).
Superphosphate requirements of clover-ley farming. II.* The residual effects of topdressing
Authors: Ayres JF , McFarlane JD , Osborne GJ , Corbin EJ
Published: November 2004

The residual effects of topdressing the grazed clover-ley were evaluated at four sites in southern New South Wales. The significance (for the initial crop) of changes in soil fertility induced by topdressing were studied in crop experiments (five superphosphate drill rates x three nitrogen rates) immediately following the ley phase. Topdressing influenced the level of available phosphate at all sites: heavy applications induced a large increase in available phosphate, light applications induced a moderate increase, and omission of topdressing led to a slight decline. The rate of soil nitrogen accretion was affected by topdressing only at sites that were initially of medium soil phosphate status. Topdressing exerted residual effects on crop growth, grain yield, and grain composition; crops following topdressed leys showed little response to superphosphate drilled with the crop at sowing. By contrast, crops following untopdressed leys showed a consistent but low requirement for superphosphate; grain production was maximized at low application rates (< 100 kg superphosphate ha-1) and the (economic) optimal rate was usually in the range 30-60 kg superphosphate ha-1. For the initial crop, low drill application rates were apparently equivalent to large amounts of superphosphate applied by topdressing the ley.

___________________
*Part I, Aust. J. Agric. Res., 28: 269 (1977).
Effects of simulated rust epidemics on the growth and yield of sunflower
Authors: Siddiqui MQ , Brown JF
Published: November 2004

Oil yield losses in sunflower (cv. Peredovic) caused by rust infection (Puccinia helianthi) were greatly influenced by the growth stage of the plant when infection occurred and by the intensity of infection. Simulated epidemics produced under greenhouse conditions, where plants were first inoculated at the vegetative, budding, anthesis or seed development stages of growth and thereafter at 10 day intervals, resulted in reductions in oil yield of 85, 73, 38 and 13% respectively relative to those in uninoculated controls. In contrast, plants inoculated once only at each of these growth stages showed reductions in 011 yield of 13, 42, 35 and 10% respectively. When plants were inoculated at the vegetative stage and thereafter at 10, 20 and 40 day intervals, the reductions in oil yield were 85, 79 and 64% respectively relative to uninoculated controls. The reduction in oil yield of infected plants was caused by a reduction in the number of seeds produced per head, the weight of individual seeds and the percentage oil content of seeds. The effects of rust infection on other parameters showed similar trends to that on oil yield.
The effects of severe feed restriction on bulls and steers. II.* Carcass composition
Authors: Price MA
Published: November 2004

The effects of a substantial liveweight loss on the carcass composition of nine half-sib Hereford bulls and steers of similar weight but different fatness have been studied by a serial slaughter technique. Bulls had a significantly (P < 0.01) greater percentage of muscle and bone and lower percentage of fat in the three-rib cut. Weight loss resulted in a significant increase in the proportion of bone (P < 0.001) and of muscle (P < 0.05), and a significant (P < 0.01) decrease in the proportion of fat, in the three-rib cuts of the steers. In terms of estimated absolute weight change in the carcass, bone loss was small in both 'sexes', and muscle loss was 32% greater than fat loss in the bulls, and 25% less than fat loss in the steers during the same period. The proportions of some commercial cuts in the carcass differed both between 'sexes' and among liveweights. An hypothesis (homeomyosis) is advanced, to explain the regulation of individual tissue weight changes during periods of liveweight change. The hypothesis indicates that it may be possible to develop greater muscularity (e.g. by the application of external loads) in cattle, and to change the distribution of muscle weight in the carcass.

________________
*Part I, Aust. J. Agric. Res., 28: 521 (1977).
Genotype, genotype × environmental and environmental effects on grain yield and related characters of cowpea (Vigna unguiculata (L.) Walp.)
Authors: Erskine W , Khan TN
Published: November 2004

Genotypic, environmental and genotype x environmental interaction variances of grain yield and related characters were estimated in six diverse lowland environments in Papua New Guinea. The genotypic variance of grain yield for six diverse genotypes accounted for only 0.2% of overall variance and was not significant against genotype x environment interaction. The relative merits of alternative selection criteria, viz. pod number per plant, seed number per pod, mean seed weight, pod length and main stem height were assessed. Environmental effects of grain yield accounted for 82% of total variance, and two factors associated with moisture and soil conditions were isolated as the major causes of this variation. Genotype × environment interaction effects were analysed by joint regression analysis, and the applicability of the analysis to tropical areas with low levels of management is discussed.
Field responses to cobalt and molybdenum by different legume species, with inferences on the role of cobalt in legume growth
Authors: Gladstones JS , Loneragan JF , Goodchild NA
Published: November 2004

Six legume species were sown over two seasons on a sandy lateritic soil of marginal cobalt and molybdenum status, with varying rates and combinations of applied cobalt and molybdenum. The seeds were from plants previously grown on the same soil without cobalt or molybdenum addition. Species differed in their responses. Lupinus angustifolius responded strongly to cobalt, which increased dry matter yield by nearly 50%, but at most only marginally to molybdenum. Lupinus cosentinii, Vicia atropurpurea and Trifolium subterraneum responded to molybdenum but not to cobalt. Lupinus luteus, and more doubtfully Trifolium hirtum, responded to neither element. Yield responses to molybdenum were always accompanied by increased nitrogen concentrations in the tops. Cobalt application resulted in either no change or a reduction ir, nitrogen concentration in the tops, even when yield was increased. No interaction was evident between the two elements. Neither element increased nodule numbers, which were ample in all treatments, but in L. angustfolius cobalt markedly increased both nodule size and to a lesser extent crown nodule incidence and slightly increased leg-haemoglobin concentration. Possible reasons are discussed for the unexpectedly unchanged or reduced nitrogen concentrations in the tops of L. angustifolius showing yield responses to cobalt. One suggestion is that enhanced rhizobium and nodule growth resulted in greater cytokinin production, with a greater effect on top growth under the conditions of the experiments than that stemming from increased nitrogen fixation.
Natural outcrossing in wheat substitution lines
Authors: Redden RJ
Published: November 2004

The frequency of natural outcrossing in two chromosome substitution lines of wheat (Triticum aestivum L. em. Thell) was estimated with one procedure and in a third substitution line with another method. The first procedure utilized a dominant inhibitor of awns as the marker to detect outcrosses in the progeny of an awned line. This trial was repeated at five locations. Segregation tests indicated that up to 80 (0.32%) awnless outcrosses were present in an estimated sample of 25,450 progeny. The second method measured outcrossing between a substitution line and two unrelated varieties by observing the intermediate phenotype of the F1 spike. Confirmation of hybridity was obtained for each plant by using starch gel electrophoresis on the endosperm of five F2 seeds from the intermediate F1 spike. This method indicated 0.16% natural outcrossing.
Influence of rootstocks on the accumulation of chloride, sodium and potassium in grapevines
Authors: Downton WJS
Published: November 2004

The seasonal course of chloride, sodium and potassium accumulation in leaves and berries of Shiraz, Cabernet Sauvignon, Sultana and Muscat Gordo Blanco scions was studied in relation to rootstock effects (own roots v. Salt Creek, Harmony and Schwarzmann rootstocks). Vines on rootstocks generally contained less chloride, but more potassium, in petioles and berries than did own-rooted vines. The extent of the effect, however, was dependent upon scion variety. Cabernet Sauvignon differed from the other scions in that vines on Harmony stock accumulated more sodium than did own-rooted vines. High levels of chloride, sodium and potassium were retained by petioles and laminae at abscission. Some possible consequences of rootstock-induced changes in the ionic composition of leaves and berries are discussed.
Superphosphate on perennial pastures. I. Effects of a pasture response on sheep production
Authors: Curll ML
Published: November 2004

From 1973 to 1975 in the Mediterranean environment of southern New South Wales, superphosphate was applied annually at four rates (0, 62, 125 and 250 kg ha-1) to an established perennial pasture with a substantial history of superphosphate use. The pasture was continuously grazed by Border Leicester × Merino ewes (at 10 and 13.3 ha-1), so that plant growth responses to superphosphate could be assessed in sheep production terms and an estimate made of the monetary value of these responses. Growth rate of unfertilized pastures declined over the experimental period, and depending on the quantity of superphosphate applied and stocking rate, responses of fertilized pastures ranged from 20 to 36% in 1973, 28 to 157% in 1974 and 75 to 233% in 1975. From having similar proportions of perennial ryegrass (Lolium perenne) and subterranean clover (Trifolium subterraneum), pastures tended towards clover dominance with little (62 kg ha-1) or no superphosphate, particularly at high stocking rate, and to grass dominance at higher rates of superphosphate, particularly at low stocking rate. By increasing the level of available pasture, superphosphate increased wool production and ewe liveweight, lambs reared, their growth rate and the percentage that reached marketable weight (32 kg). These trends were similar at both stocking rates. Significant quadratic response relationships existed between these parameters and rate of superphosphate. Withholding superphosphate caused a progressive reduction in gross margins of about 37% over the 3 year trial period, while its application increased gross margins, relative to those from unfertilized pastures, by a maximum 10, 42, and 140% for the first, second and third year respectively. It is suggested that these pasture responses calibrated in animal production terms may be extended to other situations most effectively by using the data to test and improve tentative models used to predict fertilizer requirements.
Observations on the wool follicle abnormalities in Merino sheep exposed to prolonged wetting conducive to the development of fleece-rot
Authors: Nay T , Watts JE
Published: November 2004

Groups of sheep found to be resistant and susceptible to fleece-rot following prolonged periods of natural and experimental rainfall were used in a preliminary study of the histopathological changes associated with the development of this condition. Wool follicle abnormalities affecting the growth of the wool fibre and inner root sheath were frequently observed. Weakened stretches of fibres, which appeared to result from impaired keratinization, were the sites of fibre breakage in the skin. Hypertrophic thickening and duplication of the inner root sheath occurred, and this material encased the proximal ends of broken fibres to form 'plugs'. The plugs grew vigorously in sheep that developed fleece-rot, apparently breaking the continuity of the skin as they emerged into the fleece. Fragments of plugs, broken wool fibres and exudate were present in fleece-rot bands along with cornified epithelial cells. Attempts to quantify the frequency of these abnormalities were complicated by marked variations in their horizontal and vertical distributions in the skin.
Patterns of assimilate distribution in soybeans at maturity. III.* The contribution of assimilate to pods near the apex in determinate types
Authors: Stephenson RA , Wilson GL
Published: November 2004

The distribution of 14C from leaves to pods at upper nodes in indeterminate soybeans was examined in two breeding lines. In one, each node carried pods, but the highest node had no leaf. In the other there were leaves at each node, but the second node from the top had no pods. Leaves were supplied with 14CO2 at each of the upper nodes, at a series of developmental stages from pod set to maturity, and the 14C distribution between the pods at the various nodes was determined at maturity. In both of the lines, acropetal movement to racemes became increasingly important towards the top of the plant. The higher racemes, which did not have the relationships with leaves above them or at the same level that those lower in the canopy had, drew assimilates from lower leaves. The only major differences between the patterns of distribution related to the missing raceme. The duration of pod-filling and the retention of photosynthetic capacity at the upper nodes appeared to be important for seed growth in the pods at those positions.

__________________
*Part II, Aust. J. Agric. Res., 28: 395 (1977).
Physical and chemical changes in fruit of seven avocado cultivars at Mildura
Authors: El-Zeftawi BM
Published: November 2004

The pre- and post-harvest changes of seven different avocado cultivars were determined and evaluated as indicators of maturity. All cultivars had similar trends in their growth. These trends continued during development, accompanied by reductions in moisture and free fatty acid contents, increases in oil content, and variable changes in ash content. Decreases in moisture content during maturity were negatively correlated with oil content. A relationship was found between oil content and seed weight. It is suggested that the moisture content and/or seed weight could be used by the growers to estimate oil content and therefore the best time for picking. Oil content (Y) could be calculated from one of the following equations: Y = 0.19x – 1.57 where x is the seed weight (g); or Y = 90.87 – 0.77x, where x is the percentage of moisture in the mesocarp. Taking into account the differences between the cultivars and the limited nature of the results, and on the basis of a minimum oil content of 8% as the crude fat extract, it is suggested that under local conditions, Zutano could best be picked in May, Fuerte in July, and Hazzard in September, with other cultivars to be picked between July and September. In this way a continuous supply of avocado from May to September, and even later, could be provided.
Acidosis in preruminant lambs: effect of sodium bicarbonate on nitrogen utilization and voluntary feed intake
Authors: Walker DM , Gibney MJ , Kirk RD
Published: November 2004

Thirty-three male crossbred lambs, aged 2–5 days at the start of the experiment, were used in four experiments. Experiment 1. Low protein milk replacers (0.10 of total energy as protein) that differed in acid-base balance and contained casein (diet A), cows' milk proteins (diet B) or isolated soybean proteins (ISP; diet C) were each fed to three lambs. Lambs given diet C excreted more urinary ammonia, chloride and phosphorus, but less magnesium and sodium than lambs given diets A and B. Experiment 2. Three lambs were given diet C (49 mg sodium per MJ) in three successive 9–11 day periods. When sodium bicarbonate (114 mg sodium per MJ) was added in period 2, there was a reduction in urinary ammonia nitrogen excretion (from 0.23 to 0.10 of total urinary nitrogen), but no net change in nitrogen balance. Experiment 3. The supplement of sodium bicarbonate to diet C was increased to 228 mg sodium per MJ for three lambs. Urinary ammonia nitrogen excretion decreased to 0.03 of total urinary nitrogen, but nitrogen balance was again unchanged. Experiment 4. Nine lambs were given diet C with a supplement of sodium bicarbonate to provide an additional 282 mg sodium per MJ. Nine lambs were given the unsupplemented diet (49 mg sodium per MJ). The quantity of milk replacer offered was slowly increased on alternate days. Voluntary intake fell below the amount offered after 7 days in both groups. The voluntary intake of lambs given sodium bicarbonate was significantly higher than that of the unsupplemented lambs after 9 days.
Variation between and within species of rapeseed (Brassica campestris and B. napus) in response to drought stress. I. Sensitivity at different stages of development
Authors: Richards RA , Thurling N
Published: November 2004

Drought imposed at different times on four spring cultivars of each of two oilseed rape species (Brassica campestris and B. napus) markedly influenced seed yield and its components and other characteristics of the mature plant. In general, drought reduced those plant and yield components associated with plant size, whereas other characters were variable, depending on the species and treatments. Seed yield was lowest in both species when drought was applied either from stem elongation or from the time of anthesis. However, considering grain yields in terms of the amount of water added in each treatment, B. napus cultivars were most sensitive at anthesis, with the exception of Masoweicki which was most sensitive at pod-filling. In B. campestris, Span was most sensitive when drought stress was first imposed at stem elongation, whilst other cultivars were sensitive at later reproductive stages. Principal component analyses reduced the complex interrelationships between all variables excluding yield to two major factors in each species and treatment. In general, the first factor, which explained most of the variation in the parameters measured, was composed of variables associated with plant size, whereas the second was composed of variables which were independent of plant size. The relative importance of these two factors as yield determinants varied substantially with the different species and treatments. In B. napus the first factor was the major determinant of yield ill the control and in the drought treatment imposed from stem elongation. In B. campestris the second factor was a significant determinant of yield in all treatments and the major factor influencing yield in the control and stem elongation treatments. Increased root weight was associated with increased yield in the drought treatments in both species, but this was primarily due to its association with plant size. When the influence of plant size was accounted for, it was observed that a smaller root weight relative to the above-ground plant weight and a greater tap-root weight relative to lateral root weight was associated with higher yield in both species in all drought treatments. As well as these latter characters, seed weight per pod, and harvest index were the most important group of characters contributing to yield in both species in all treatments when variation in plant size was accounted for.
Epidemiological factors influencing the success of roguing for the control of bunchy top disease of bananas in New South Wales
Authors: Allen RN
Published: November 2004

An infection chain was reconstructed from historical data of a typical outbreak of bunchy top disease of bananas to determine factors influencing the seasonal occurrence and eradication of disease under roguing. The results were described by a mathematical model involving four random variables (incubation period, relative infection rate, detection efficiency and eradication efficiency) and one fixed variable (inspection interval). The model successfully predicted the course of roguing in an independent disease outbreak. The incubation period of the disease depended on the time taken for two banana leaves to emerge after inoculation. At Alstonville, N.S.W., the incubation period varied from 19 days in summer to 125 days in winter. The relative infection rate varied on average from 0.027 to 0.001 new infections per old infection per day in summer and winter respectively. Efficiency of disease detection by experienced inspectors depended on the number of leaves displaying disease symptoms and, equally, on time of year. Under the normal 3-weekly inspection routine, detection efficiency varied from 0.94 in summer to 0.19 in winter, plants being found on average at the two-leaf stage of disease. The efficiency with which banana growers eradicated diseased plants following their detection was found to be a characteristic of the grower concerned but was, in general, poorest in late summer.
Relative efficiency of Merino and Border Leicester × Merino ewes
Authors: Kleemann DO , Dolling CHS
Published: November 2004

Thirteen South Australian strong-wool Merino ewes and eight Border Leicester × Merino ewes mated to Poll Dorset rams were fed on lucerne pellets ad libitum during late pregnancy and lactation in pens. Each of their single-born progeny was slaughtered at 33 kg full liveweight. Breeds were compared for efficiency of the ewe (organic matter intake per unit liveweight and clean wool per unit intake), efficiency of the lamb (liveweight and body solids gain per litre of milk), and efficiency of the ewe-lamb unit (liveweight and carcass weight per unit intake). Border Leicester × Merino ewes ate 7% less organic matter per unit liveweight than Merino ewes during lactation; however, there was no significant difference during late pregnancy. In terms of absolute intake 120 Merinos = 100 Border Leicester × Merinos. Border Leicester × Merino ewes were 73% as efficient in converting feed to clean wool as Merino ewes. Merino ewes grew wool of smaller diameter and higher crimp frequency than crossbreds. Lambs from the Merino ewes were as efficient in converting milk into animal tissue as the progeny from Border Leicester x Merino ewes during the first 4 weeks of suckling. Lambs from Merino ewes required on average 25 extra days to grow to the same slaughter weight and ate 110% more organic matter from solid feed than lambs from crossbred ewes. However, the proportion of feed eaten by the lamb was small (10%) compared with that eaten by the ewe. Lambs from crossbred ewes were 23% heavier than those from Merino ewes at the same age. The crossbred ewe-lamb unit, however, consumed 20% more feed and hence was as efficient as the Merino ewe–lamb unit. The Merino ewe–lamb unit was more efficient than the crossbred ewe-lamb unit when the lamb genotypes were slaughtered at the same liveweight (P < 0.05); however, the difference was not significant when expressed as carcass weight per unit intake.
Corrigendum - Relative efficiency of Merino and Border Leicester × Merino ewes
Authors: Kleemann DO , Dolling CHS
Published: November 2004

Thirteen South Australian strong-wool Merino ewes and eight Border Leicester × Merino ewes mated to Poll Dorset rams were fed on lucerne pellets ad libitum during late pregnancy and lactation in pens. Each of their single-born progeny was slaughtered at 33 kg full liveweight. Breeds were compared for efficiency of the ewe (organic matter intake per unit liveweight and clean wool per unit intake), efficiency of the lamb (liveweight and body solids gain per litre of milk), and efficiency of the ewe-lamb unit (liveweight and carcass weight per unit intake). Border Leicester × Merino ewes ate 7% less organic matter per unit liveweight than Merino ewes during lactation; however, there was no significant difference during late pregnancy. In terms of absolute intake 120 Merinos = 100 Border Leicester × Merinos. Border Leicester × Merino ewes were 73% as efficient in converting feed to clean wool as Merino ewes. Merino ewes grew wool of smaller diameter and higher crimp frequency than crossbreds. Lambs from the Merino ewes were as efficient in converting milk into animal tissue as the progeny from Border Leicester x Merino ewes during the first 4 weeks of suckling. Lambs from Merino ewes required on average 25 extra days to grow to the same slaughter weight and ate 110% more organic matter from solid feed than lambs from crossbred ewes. However, the proportion of feed eaten by the lamb was small (10%) compared with that eaten by the ewe. Lambs from crossbred ewes were 23% heavier than those from Merino ewes at the same age. The crossbred ewe-lamb unit, however, consumed 20% more feed and hence was as efficient as the Merino ewe–lamb unit. The Merino ewe–lamb unit was more efficient than the crossbred ewe-lamb unit when the lamb genotypes were slaughtered at the same liveweight (P < 0.05); however, the difference was not significant when expressed as carcass weight per unit intake.
Effects of boron on the physiological activity of zinc in maize
Authors: Leece DR
Published: November 2004

When maize plants were grown in pots in a glasshouse for 30 days on a black earth soil, plants developed symptoms of zinc deficiency and responded to zinc fertilization, yet the tops contained normal levels of zinc. It was assumed that much of the zinc accumulated in plant tops was physiologically inactive. The condition was not caused by phosphorus/zinc, iron/zinc, copper/zinc, or manganese/zinc imbalances, but was associated with marginally deficient boron levels in experiments conducted in late autumn when light intensity was low. In one such experiment, boron fertilization (1 µg/g) prevented the inactivation of zinc and increased plant growth. However, in experiments conducted in spring when light intensity approximated the normal field situation more closely, boron levels were normal and boron fertilization (5 µg/g) had no effect on plant growth and failed to prevent zinc inactivation. Thus, it is unlikely that zinc inactivation under normal field conditions is caused by marginally deficient boron levels.
The effect of photoperiod and temperature on the first crop and ratoon growth of Pennisetum purpureum Schum
Authors: Ferraris R
Published: November 2004

Elephant grass (Pennisetum purpureum Schum.) was grown in phytotron cabinets for 60 days at 30/25° or 21/16°C (daylnight) in either 8 or 16 hr photoperiods. During the juvenile phase the higher temperature increased the leaf appearance rate, tillering rate and main stem elongation rate. Once plants in the 8 hr photoperiod became reproductive, the stem elongation, tillering rate and leaf appearance rate increased. The higher temperature continued to stimulate development. At harvest at 60 days plants grown at 30/25° had higher leaf, stem and total dry matter yields, a greater leaf area but lower carbohydrate content in the stubble. The 16 hr photoperiod produced higher dry matter yields at harvest than the 8 hr photoperiod. A comparison pot experiment grown in short day and long day photoperiods under field conditions in north Queensland produced similar findings to the phytotron experiment. After harvest, stubbles were ratooned into either short day (8 hr) or long day (16 hr) photoperiods, the temperature difference being maintained. Leaf number per main stem and main stem elongation were similar to those of the first crop, but more tillers and higher yields were produced in the ratoon crop. Temperature and photoperiod effects were similar in both crops. It was concluded that low temperatures rather than reduced photoperiod would be the greatest limitation to the adaptation of the species as an industrial or forage crop where yearround production is required.
Digitaria striate virus—a rhabdovirus of grasses transmitted by Sogatella kolophon (Kirk.)
Authors: Greber RS
Published: November 2004

A previously undescribed rhabdovirus causing striate symptoms mainly in the Digitaria species D. decumbens (pangola grass) and D. ciliaris (summer grass) was found within a range of 18–28°S, of the Australian east coast. About 10% of individuals of the delphacid leafhopper Sogatella kolophon (Kirk.) transmitted the virus after a 24 h acquisition feed. The time between acquisition and first transmission was 5–8 days with an 8–11 day latent period before symptoms appeared in the plant. Transmission in a persistent manner was demonstrated for males and females and for nymphs and adults and through the moult to adults.The experimental host range was shown to include Avena sativa, Brachiaria miliiformis, Digitaria sanguinalis, Dinebra retroflexa, Eleusine coracana, Eleusine indica, Hordeum vulgare, Lolium multiflorum, Rhynchelytrum repens and Urochloa mosambicensis. Bullet-shaped particles 280 nm by 55 nm were readily found by electron microscopy of negatively stained sap from infected plants. The particles were often in groups and frequently showed crosss-triations, which were at a spacing of 4.2 nm and coincided with the frequency of the surface projections. Thin-section electron microscopy of infected plant tissue showed bacilliform and bullet-shaped particles in groups bounded by cytoplasmic membranes. No particles were seen within the nucleus or perinuclear space, and the particles were almost exclusively within companion cells and phloem parenchyma cells. Rhabdovirus-like particles and tubular structures were located within the brain and salivary glands of proven vector individuals, but not in healthy insects.
The production of toxin in annual ryegrass, Lolium rigidum, infected with a nematode, Anguina sp., and Corynebacterium rathayi
Authors: Stynes BA , Petterson DS , Lloyd J , Payne AL , Lanigan GW
Published: November 2004

Experiments confirmed that galls induced by nematodes (Anguina sp.), which develop in the place of seeds on ryegrass plants, become toxic to animals when colonized by Corynebacterium rathayi. The distribution of the toxin within the galls was determined by measuring the levels in extracts from the plant and from the parasite components. Bioassays showed that the toxicity of the plant component was considerably greater than that of the bacterial component. An amount of toxin constituting a dose lethal to nursling rats was extracted from between 0.15 and 0.25 mg of plant component compared with between 5.52 and 5.75 mg of bacterial component. These results suggest that the toxin is produced in the plant tissues in response to the presence of the bacterium. Furthermore, the extracts inhibited the growth of C. rathayi in vitro, which suggests that the toxin behaves in a general sense like a phytoalexin.
Selection against sprouting damage in wheat. III.* Dormancy, germinative alpha-amylase, grain redness and flavanols
Authors: Gordon IL
Published: November 2004

Grain development of embryo dormancy, germinative α-amylase, pigmentation and flavanols was examined in the wheats Timgalen and Gamut (white-grained, non-dormant), and Pembina and Sonora (red-grained with different levels of dormancy). It was found that each trait had distinctive patterns of development. The net result at harvest ripeness depended on the synchronizations amongst the traits. Dormancy, as judged by embryo response (i.e. embryo dormancy), was restricted to the red wheats. Three ways of expressing it were noted: (1) in terms of development patterns, (2) as levels at harvest ripeness or at harvest, and (3) by the length of the period of embryo dormancy after harvest ripeness. Two hypotheses linking embryo dormancy and grain redness appeared plausible from the results. One was that the polyphenol oxidase complex, which polymerizes flavanols to the putative pigment phlobaphene, contributes towards embryo dormancy, probably through enhancement of hypo-oxia. The other was that the pigment itself and its tanning complexes cause the hypo-oxia. Flavanols did not appear to be in vivo germination inhibitors. Dormancy, as judged by α-amylase response (i.e. amylase dormancy), was not always present together with embryo dormancy. A long period of amylase dormancy was found in the more embryo-dormant red wheat, but not in the other. Conversely, a short period of amylase dormancy was found in one white wheat, but it was not embryo-dormant. Possible relationships between these physiological traits and the classical genes for red grain-coat were discussed. Implications concerning selection against sprouting damage were considered.

_________________
*Part II, Aust. J. Agric. Res 30: 1-17 (1979).
Herbage digestion in the stomach and intestines of weaner lambs at different stages of their maturity
Authors: Weston RH , Margan DE
Published: November 2004

Various parameters relating to digestion of a clover diet in the stomach and intestines were measured by marker techniques in the same weaner lambs at 15, 24 and 40 weeks of age when body weights averaged 18, 29 and 44 kg respectively. Significant small changes were observed with increasing age and body size in the values of several of the parameters measured. Thus at 40 weeks relative to 15 weeks values were higher for (i) crude protein digested in the intestines per unit feed intake (+ 10%), (ii) sodium content of rumen liquor and sodium flow from the rumen per unit feed intake (+ 9%, + 14%), (iii) potassium and chloride contents of abomasal liquor (+ 9%, + 7%) and (iv) pH of abomasal digesta (+ 0.3 pH unit). Values were lower for (v) digestibility of organic matter and cell wall constituents in the whole alimentary tract (c. – 1.8%), (vi) ammonia content of rumen liquor and ammonia flow from the rumen and abomasum per unit feed intake (– 15% to – 20%) and (vii) potassium content of rumen liquor (– 9%). No changes attributable to age or body size were observed with several paramefers, including (i) rate of production of volatile fatty acids in the rumen per unit feed intake, (ii) rate of absorption of volatile fatty acids from the rumen, (iii) rate of flow of digesta through the stomach per unit feed intake, and (iv) mean residence time of water-soluble marker in the rumen. The results indicate that care needs to be exercised in applying digestion data obtained with adult sheep to the nutrition of the growing weaner lamb.
Genetic variability of root growth in wheat (Triticum aestivum L.)
Authors: O'Brien L
Published: November 2004

Ten wheat genotypes were examined for their pattern of root development in glass-fronted growth containers in the greenhouse. Differences between genotypes were recorded in the number of first-order lateral roots at 2,3 and 4 weeks' growth, the number of second-order lateral roots, the maximum depth of penetration, and the angle between the seminal root axes at 4 weeks' growth and the length of lateral root per 10 cm depth increment at 5 weeks' growth. Significant positive correlations existed between many of the seminal root parameters. Differences between genotypes in the length of nodal root axes were recorded at 7 and 8 weeks' growth. Nodal root length was influenced by tiller number and the rate of tiller initiation. Tiller development, and consequently root growth, was related to plant phasic development. Genetic modification of seminal root development appears possible, with the direction of selection depending on the definition of an optimum root development pattern.
The accuracy of tritiated water turnover rate as an estimate of milk intake in lambs
Authors: Dove H , Freer M
Published: November 2004

The accuracy of water turnover measurement as an estimate of milk intake was evaluated, with special reference to the validity of the assumptions underlying the technique. Even when milk was the only source of water for penned lambs, water turnover measurement significantly underestimated known milk intake. The underestimates were greater over longer measurement periods. It is suggested that these underestimates occurred because changes in body water pool size were not considered in the calculation of water turnover, since estimates were improved by the incorporation of a pool size correction. In a second pen trial, it was demonstrated that the inhalation of vapour from tritiated water excreted by other lambs was not a source of error in the estimation of water turnover. .In a field trial, the turnover technique was successfully employed to estimate milk intake in the first 3–4 weeks of life. A method for accommodating changes in pool size is presented, and it is suggested that the effects of pool size changes on the accuracy of the estimate of milk intake are too large to be ignored. In later weeks of the experiment, it was obvious that lambs were consuming water in forms other than milk, so that milk intake estimates were inaccurate. .It is concluded that in animals consuming only milk, measurement of tritiated water turnover provides an accurate estimate of milk intake, but only if changes in body water pool size are taken into account.