bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of carcass cuts to predict beef carcass composition: a research technique
Authors: Johnson ER , Charles DD
Published: November 2004

Eleven Angus, 12 Friesian and 12 Hereford steers were used to investigate the degree of accuracy and usefulness of primal cut tissues in predicting side composition. The criteria used for evaluating the cuts were: (a) standard error of estimate of the equation, (b) homogeneity of 'b' values among breeds, (c) appreciable bone content in cut to allow the prediction of side bone, and (d) the absence of major difficulties in the replication and dissection of cuts. Simple and multiple regression analyses showed that the most accurate predictors of carcass composition, in descending order, with standard errors of estimate of muscle, fat and bone percentages respectively, were: hindquarter plus rib cut (0.37 %, 0.47 %, 0.30 %); hindquarter (0.73 %, 0.87%, 0.49%); loin plus rib cut (0.84%, 0.88%, 0.48%); rib cut (1.13%, 1.26%, 0.59%); loin (1.24%, 1.21 %, 0.72%). The most useful of four easily obtained carcass variables in improving the prediction accuracy of carcass components from multiple regression proved to be primal cut weight and fat thickness at the 12th rib, particularly the former. Both significantly reduced the standard errors of estimate of muscle, fat or bone in equations based on loin, rib cut and loin plus rib cut, but not in equations based on hindquarter plus rib cut and hindquarter. Kidney plus pelvic fat weight was of limited value, resulting only in a slight improvement in the prediction of side bone percentage using the equations based on bone percentage of the hindquarter. Carcass weight was of equal value to primal cut weight in improving the prediction accuracy of multiple regression. Five sets of part-carcass prediction equations are given, providing a choice of prediction accuracy, labour expenditure and cost for research workers whose requirements and resources may vary.
An analysis of variability and genotype × environment interaction in mung bean (Vigna radiata) in south-eastern Queensland
Authors: Imrie BC , Butler KL
Published: November 2004

Thirty mung bean (Vigna radiata) accessions were grown in replicated hill plots at two sites in each of 2 years. Plant height, days to flower and to harvest, and seed yield were recorded for each plot. In an analysis of variance most main effects and interactions were statistically significant. Estimated variance due to environment exceeded that due to genotypes for all characters. Broad sense heritability of seed yield was 0.07. The linear regression of seed yield on plant height was statistically significant, and there was a significant quadratic effect of yield on days to flower. It was concluded that environmental effects on the duration of growth phases were likely to be mainly due to the effect of different sowing dates on photoperiod-sensitive accessions, while rainfall variability most likely contributed to yield variance. Emphasis in an evaluation program should be on sampling years rather than locations.
The influence of feeding level and type of feed on the carcasses of steers
Authors: Sully RJ , Morgan JHL
Published: November 2004

In an experiment started in June 1976, 14-16-month-old Hereford steers weighing 300 kg were allocated to five treatments. Cattle in four of the treatment groups, viz. high (H), medium (M), low (L) and low-high (L-H) growth rates were held in feedlots and offered whole oats supplemented with linseed meal, hay and minerals to obtain growth rates of 1.0, 0.7, 0.4 and 0.4-1.0 kg day-1 respectively. Steers in the fifth treatment group were grazed on pasture (P) to gain weight at 0.7 kg day-1 and received no supplements. Each treatment group of 10 steers was slaughtered at a mean liveweight of 450 kg. The carcasses of H steers were shorter, had more total fat and a greater depth of fat at the 12-13th rib than those of the L steers (fat depths of H, M and L groups were 10.1, 8.6 and 7.1 mm). The H steers also had a larger eye muscle area, a higher ABCAS (Australian Beef Carcase Appraisal System) score and higher carcass grades than the L steers. The L-H treatment appeared to reduce the fat content of the total side relative to the M treatment but the treatment was confounded with differences in carcass gain and carcass weight. Pasture grazing reduced carcass fat content as compared with grain feeding (15.2 v. 18.6%; P c 0.05), but differences in depth and weight of subcutaneous fat in the carcass side or in individual cuts were not significant. There was no detectable difference in tenderness due to level of feeding or feed type. Separately, the effects of feeding level and grain feeding increased carcass fatness by 16 and 22% respectively; we suggest that these effects are of commercial importance, particularly if the combined effects are additive.
Growth and productivity of irrigated Sorghum bicolor (L. Moench) in northern Australia. I. Plant density and arrangement effects on light interception and distribution, and grain yield, in the hybrid Texas 610SR in low and medium latitudes
Authors: Muchow RC , Coates DB , Wilson GL , Foale MA
Published: November 2004

The influence of plant arrangement and density on yield of the grain sorghum hybrid Texas 610SR grown as an irrigated dry season crop in the Ord Irrigation Area (lat. 16�S) was determined. Neither the rate of dry matter production nor the pattern of partitioning of dry matter during grain-filling varied between treatments, and grain yield was unresponsive to row spacings below 75 cm and densities above 267000 plants ha-1. The results were analysed by considering the effect of radiation interception and distribution in the canopy on dry matter production. The opportunity was then taken to compare this trial, and two others conducted at the same low latitude where grain yield was unresponsive to density, with four trials conducted at higher latitudes (27�S.) where Texas 610SR was very responsive to density. The effect is shown to be associated with radiation penetration into canopies. In the low latitude trials the poorer penetration of photosynthetically active radiation (PAR) into high density stands could have resulted from lack of structural adjustment of the canopy, in contrast to the experience at medium latitude. Equally, there may have been an effect of lower solar angles at low latitude, resulting in the poorer PAR distribution. The consequence was a failure of response of dry matter production to increasing density, reflected in grain yield.
Urinary calculi formation in sheep on high wheat grain diets
Authors: Godwin IR , Williams VJ
Published: November 2004

The effects of calcium, phosphorus and magnesium contents of diets containing different proportions of wheat grain to roughage on the excretion of minerals involved in urinary calculi formation by sheep, were examined in three separate studies: the first, with six sheep, determined the effects of increasing the percentage of wheat grain in the diet on the digestibilities of Ca, P and Mg, the excretion of these three elements in urine and on the propensity of the diets to form calculi; the second involved two sheep and studied the effects of supplementing a 90% grain diet with CaCO3 and roughage on faecal and urinary excretion of Ca, P and Mg; the third was carried out using four sheep fed on a 75 % grain diet and examined the effects of supplementation with extra P, Ca and roughage on Ca, P and Mg excretion. Urinary P concentration was directly correlated with the formation of calculi. Plasma inorganic phosphorus (P,) increased when grain in the diet was 75 % or greater and this led to increased urinary P excretion. The addition of CaCO3 reduced urinary P without large changes in plasma P1 and increased the faecal output of P. Extra roughage added to high grain diets reduced the digestibility of both Ca and P and the plasma concentration and urinary excretion of P. The significance of these findings for the prevention of urinary calculi in sheep is discussed.
Genetic parameters for egg weight v. age curve, and other egg production and egg weight traits, in synthetic lines of chickens
Authors: Yoo BH , Sheldon BL , Podger RN
Published: November 2004

An exponential curve, W = P-Qexp(- Rt), where W is egg weight at age t, was fitted to egg weights of individual pullets, and genetic parameters were estimated for P, Q and R, the residual standard deviation and other egg weight and egg production characters. The data consisted of records collected over six generations on more than 4000 pullets in two selection lines and a control line which originated from a synthetic gene pool of White Leghorn x Australorp crosses. The half-sib and offspring-on-parent regression estimates of heritability pooled over the lines were 0.23 and 0.33 for P, 0.14 and 0.20 for Q, and 0.14 and 0.25 for R. Genetic correlations were estimated to be -0.10 between P and Q, -0.46 between P and R, and 0.90 between Q and R. These estimates suggest that the egg weight v. age curve may be modified to increase the proportion of eggs in desirable weight grades and reduce the incidence of oversized eggs later in the production year. The genetic correlation between mean weight of first 10 eggs and egg weight at 62 weeks of age was estimated to be 0.68, further suggesting that early egg weight may be improved partly independently of late egg weight. The heritability estimates of egg mass output were not higher than those of egg number in spite of the highly heritable average egg weight being an important component of egg mass, probably because of the negative genetic correlation (r = -0.49) between egg number and average egg weight. The standard deviation of individual pullet's egg weights was moderately heritable and genetically correlated positively with egg weight characters and negatively with egg production; these estimates were consistent with the responses to selection for reduced egg weight variability observed elsewhere
Degradation of mimosine by rumen contents: effects of feed composition and Leucaena substrates
Authors: Tangendjaja B , Hogan JP , Wills RBH
Published: November 2004

Samples of rumen fluid obtained from sheep that had been fed on different diets were fractionated into microorganism and supernatant fractions, and the former divided into bacteria-rich and protozoa-rich fractions. The fractions were evaluated for their ability to degrade purified mimosine during in vitro incubation. The rumen contents of sheep fed on a lucerne-oats mixture produced a more rapid degradation of mimosine than did that from sheep fed on lucerne hay, which was greater than that from a Digitaria pentrii diet. Most activity was in the bacteria-rich fraction for the lucerne-oats diet and in the protozoa-rich fraction for the other diets. The rate of degradation of endogenous mimosine in Leucaena leaf during incubation in ruinen fluid was much greater than for the purified mimosine. The substantial degradation observed when a buffer solution was substituted for rumen fluid was attributed to endogenous leaf enzymes. These enzyme systems were more efficient at degrading mimosine than were the microorganisms in the rumen liquor.
Measurement of the quantity and composition of digesta in the reticulo-rumen of sheep fed on a roughage diet
Authors: Egan JK , Pearce GR , Doyle PT , Thomas R
Published: November 2004

In two experiments, estimates of the quantity and composition of digesta in the reticula-rumen of sheep given a roughage diet were made using a recently published marker technique. These estimates were compared with measurements made on the same sheep at slaughter. Estimates of digesta dry matter were influenced by the method of obtaining digesta samples from the rumen. When samples were withdrawn through a plastic tube, the resultant estimates underestimated the values obtained at slaughter by an average of 6%. An alternative sampling procedure is described which provided estimates within 1.5 % of values at slaughter. Values obtained for the organic matter, plant cell wall, and nitrogen content of digesta were similar for the slaughter method and the marker technique, irrespective of the method of sampling. In both experiments, the marker technique consistently underestimated the quantity of water in the rumen by 2-19 %. The importance of measures made on digesta load in the reticulo-rumen is illustrated by an examination of the variability between sheep in digestion of plant cell wall material.
Control of the nematode associated with annual ryegrass toxicity
Authors: McKay AC , Fisher JM , Dube AJ
Published: November 2004

To control the nematode Anguina funesta (considered by some to be A. agrostis), the vector in annual ryegrass toxicity, pasture management treatments were applied before and after gall initiation. Before gall initiation, the herbicides paraquat and diclofop methyl were used to remove ryegrass. These treatments gave good control of the nematode, but reduced pasture production in winter when feed is generally scarce. Diclofop methyl had no detrimental effect on legume growth, and was more effective on actively growing ryegrass than was paraquat, which severely retarded subterranean clover. Desiccating the ryegrass heads, with mechanical topping or the desiccant herbicide paraquat, after gall initiation, but before hatching of the second-stage juveniles ( J2s ) , gave good control of the nematode population. The main limitations with mechanical topping are that the ryegrass heads must be tall enough to cut before the J2s hatch and not all paddocks are suitable for topping. With paraquat, the main limitations are that treated material was susceptible to weathering and there was less regrowth to set seed. Oxamyl, a systemic nematicide applied after gall initiation, had no effect on the nematode, nor had spraying pasture with the nematode parasitic fungus Verticillium sp.
The utilization of nitrogen and sulfur by weaner and mature merino sheep
Authors: Doyle PT , Egan JK
Published: November 2004

The intake, excretion, and retention of nitrogen and sulfur were measured in weaner (liveweight 15-17 kg) and mature (40-45 kg) Merino sheep offered ad libitum amounts of three pasture hays. The hays (H, M and L) varied in their content of digestible organic matter (71, 59 and 45%), of nitrogen (2.84, 0.72 and 1.20%), and of sulfur (0.20, 0.13 and 0.09%). When given the most-digestible hay (H), the weaners retained more nitrogen than did the mature sheep (0.97 v. 0.81 g per l00g digestible organic matter intake (DOMI), but there was no difference in retention of sulfur (79 v. 74 mg per l00g DOMI)). However, on the basis of metabolic liveweight, the weaners incorporated more of both nutrients into tissues, while the mature wethers incorporated more nitrogen and sulfur into wool. The retention of nitrogen and of sulfur per unit of DOMI were similar for each age group of sheep when the medium quality hay (M) was given. Mature sheep again incorporated more of each nutrient into wool. With the poorest quality hay (L), the weaners excreted more nitrogen and sulfur as a proportion of the amounts consumed than did the mature sheep. This resulted in a lower retention of nitrogen (-1.45 v. -0.74 g per l00g DOMI) and sulfur (-77 v. -14 mg per l00g DOMI) by the weaners. There was a lower incorporation of nitrogen into tissues per unit of metabolic liveweight by the weaners, and the mature sheep incorporated more nitrogen and sulfur into wool. The weaners grew wool less efficiently (g per l00g DOMI) than the adult sheep on all diets, the difference being greatest when the poorest quality hay was given. These results are discussed in relation to the nature of tissue energy reserves in weaner sheep.
Effect of level of water intake on water, energy and nitrogen balance and thyroxine secretion in sheep and goats
Authors: More T , Howard B , Siebert BD
Published: November 2004

Sheep and goats fed on a diet of oaten chaff were subjected to a 50% reduction and a 50-70% increase in their water intake. Measurements were made of water, energy and nitrogen balance and thyroxine secretion rate. Water restriction decreased feed intake by 25%, but in a lesser proportion than expected from the ad libitum feed to water relationship. This effect was achieved by a reduction in the concentration of water in faeces and by the evaporation of less water. When additional water was given, there was a 10% reduction in feed intake associated with a loss of nitrogen brought about by an increase in urine volume. Again less water was evaporated than expected under this treatment. Thyroxine secretion rate was positively related to energy intake.
A caliper for determining carcass composition in live cattle and skin-on carcass
Authors: Johnson ER , Davis CB
Published: November 2004

A Harpenden Skinfold Caliper used to predict body density in man was modified for use in cattle. It was used to measure thickness of the anal fold, caudal fold and rectal wall in 34 live steers or their skinon carcasses (hot dressed weight 139-339 kg). The value of these measurements in determining carcass fat and carcass muscle was compared with that of 10th and 12th rib fat thickness measurements made in the carcass. Hot carcass weight was the best predictor of side fat weight and side muscle weight. Side fat percentage and side muscle percentage were most accurately predicted by 12th rib and 10th rib fat thickness, followed by live then single-shackle anal fold fat thickness. The three caudal fold measurements and rectal wall thickness were poor predictors. Addition of hot carcass weight to all linear measurements markedly improved the prediction of side fat weight and side muscle weight, but nor side fat percentage and, only marginally, side muscle percentage. Single-shackle anal fold fat thickness, slightly less accurate than the live measurement, was the most useful skin-on measurement. The spring-operated caliper described can be used to determine carcass fatness and carcass lean in live steers with an accuracy closely approaching that of 12th rib fat thickness in the carcass.
Efect of great brome (Bromus diandrus Roth.) on the growth of wheat and great brome and their uptake of nitrogen and phosphorus
Authors: Gill GS , Blacklow WM
Published: November 2004

A field experiment was conducted at Badgingarra, W.A., during 1981 to study competition between wheat (cv. Gamenya) and great brome (Bromus diandrus Roth.). Shoot dry matter per plant of wheat was reduced from 1.41 g per plant in wheat monoculture to 0.50 g per plant after competing for 71 days with great brome at density of 400 plants m-2. Tiller production was reduced from 605 tillers m-2 in monocultures of wheat to 336 tillers m-2 when growing in association with 400 plants m-2 of great brome. Competition with great brome reduced the concentration of nitrogen and phosphorus in wheat shoots; at Feeke's scale 3 (tillers formed) wheat plants competing with 400 plants m-2 of great brome had 3.15 � 0.09% (mean � s.e., w/w) nitrogen and 0.58% phosphorus against a concentration of 4.05 � 0.1% nitrogen and 0.77% phosphorus in the monoculture of wheat. The reduction in the nitrogen - and phosphorus concentrations in wheat shoots earlier than any significant reductions in their dry matter suggested that great brome competed with wheat for absorption of nitrogen and phosphorus. Competition with great brome also resulted in significant reduction in the grain yield (r = - 0.77) and yield determinants of wheat. Reduction in mass per grain (r = - 0.77) was probably due to competition with great brome for water during grain-filling.
Effects of soil salinity and mineral nitrogen on the acetylene reduction activity of Trifolium subterraneum
Authors: Hopmans P , Douglas LA , Chalk PM
Published: November 2004

Subterranean clover (Trifolium subrerraneum L.) was grown under controlled environmental conditions in pots containing a variety of soils. Non-destructive assays were used to measure rates of acetylene (C2H2) reduction by the plants. Soil mineral nitrogen (N) status and, to a lesser extent, soil salinity were found to be the most important soil properties relating to the development of C2H2reduction activity in subterranean clover. Application of KNO3 to pots resulted in an immediate decrease in the rate of C2H2reduction. A linear relationship was found between the loss in C,H, reduction activity and the amount of N applied up to 40 mg N kg-1 soil. Addition of salt (NaCl) to pots caused an immediate decrease in C2H2 reduction activity, followed by a gradual recovery. A linear relationship was found between the loss in C2H2 reduction activity and the level of soil salinity induced by salt addition. The loss in C2H2reduction \vas reflected in the lower total N content of the plants when soil salinity levels exceeded 4 mS cm-1.
Studies on competition for sulfur between subterranean clover and annual ryegrass. III. Effects of plant density and nitrogen supply
Authors: Gilbert MA , Robson AD
Published: November 2004

The effects of plant density and supplies of nitrogen and sulfur on competition for sulfur between subterranean clover (Trifolium subterraneum cv. Trikkala) and ryegrass (Lolium rigidum cv. Wimmera) were studied in a glasshouse experiment over a period of 40 days. Irrespective of the density or proportion of each species in the mixture, changes in the supply of nitrogen and sulfur did not cause interspecific competition for sulfur. For subterranean clover, sulfur application increased the number of lateral branches, petiole length and shoot yield. Sulfur application had similar effects on ryegrass, but only at the high level of nitrogen supply. Nitrogen application increased leaf length and tiller number of ryegrass, and increased yield and sulfur content of shoots of both species. In swards where both species were in equal proportions, increasing the overall density from 10 to 30 plants/pot (i.e. from 497 to 1490 plants/m2) did not affect botanical composition or result in interspecific competition, but increased the degree of intraspecific competition. As density increased, the number of branches (tillers), the yield and the sulfur content per plant of each species decreased. Increasing plant density increased the average length of subterranean clover petioles, but had no effect on the average length of ryegrass leaves. When the ryegrass density in mixed swards was low, increasing the density of subterranean clover plants resulted in interspecific competition to the detriment of ryegrass. This competitive situation was considered to be due to competition for light, as it was not alleviated by the addition of sulfur and nitrogen.
Corrigendum - Investigations into the increased rust (Puccinia helianthi) intensity on some hybrid sunflower cultivars grown in Queensland
Authors: Goulter KC , Kochman JK , Brown JF
Published: November 2004

Sunflower rust intensity in crops of several hybrid cultivars in Queensland during the 1980, 1981 and 1982 seasons ranged from 30 to 60% of leaf area. In previous years, these cultivars had rust ratings of 2-5%. Rust was also found on some crops of usually immune hybrids grown during winter in central Queensland. A number of rust differential lines were inoculated with several isolates collected from throughout Queensland during 1981 and 1982, as well as with isolates stored in liquid nitrogen from the years 1976, 1978 and 1980. Because all isolates failed to infect the differentials possessing either the R1 or R2 genes for resistance, all collections were allocated to race 1. Comparisons of the temporal isolates revealed that no differences could be detected among the generation times, pustule number and pustule size produced by isolates on a range of sunflower rust differentials and hybrid cultivars. These data indicated that the composition of the pathogenic population had not altered. The application of higher inoculum densities shortened generation times and produced more pustules; both relationships were linear. The development of race 1 rust on seedlings of the immune hybrid Hysun 30 was induced by maintaining the plants under low light intensity or short photoperiods.
Factors affecting growth and reproduction of Noogoora burr (Xanthium occidentale Bertol.)
Authors: Martin RJ , Carnahan JA
Published: November 2004

Plant density and availability of light and water significantly affected growth and reproduction of Noogoora burr plants grown in a glasshouse. Burr yield was reduced most by low levels of available water. Low light intensity, low water availability and high plant density reduced net assimilation rates and, in combination, caused the greatest reduction in burr production. Under field conditions the ratio of burr dry weight to total shoot dry weight decreased with increasing plant density. In terms of production per unit area, dry weight of main stems and main stem leaves increased with increasing plant density at the expense of burr dry weight. We conclude that the success of Noogoora burr as a fleece contaminant could be attributed, in part, to: the insensitivity of burr production to variation in soil fertility and length of growing season; the ability to regulate plant density under conditions of limiting light or water; and the ability to regulate plant components so that the efficiency of burr production increases with a decrease in plant density.
Effects of soil bulk density and water regimen on root growth and uptake of phosphorus by ryegrass
Authors: Cornish PS , So HB , McWilliam JR
Published: November 2004

The effects of soil bulk density (�) and water content on root extension, phosphorus (P) uptake and plant growth were studied with ryegrass in pot experiments with a sandy loam soil. Uptake was considered in terms of a root cylinder model with parameters of root length and uptake per unit length. Increasing � (from 1.0 to 1.54 g cm-3 ) slightly increased root diameter and reduced root hair length, but the main effect on uptake per unit length of root was related to the increased mass of soil and hence the increased mass of P within the root hair cylinder. The effect of � on diffusion to the surface of the cylinder appeared to be small. Increasing � also increased soil strength, causing a reduction in root length which was linearly related to P uptake. Thus the effect of � on total P uptake was a product of the opposing effects on uptake per unit length and root length. The importance of these two effects was confirmed by calculating potential P uptake using a simple root cylinder model in which � was a variable. Predicted and observed values were highly correlated (r2 = 0.94). Drying the soil reduced P uptake per unit length of root, but, in compacted soil, this effect was small compared with the effect of drying on root extension. It appears that, when this soil type is not cultivated, drying will reduce P uptake mainly because mechanical resistance reduced root extension, and root extension ceased well within the available water range in intact soil cores.
A species-area curve for buried viable seeds
Authors: Forcella F
Published: November 2004

A species-area curve was constructed for buried viable weed seeds in a 5-year-old subterranean clover-annual ryegrass pasture in south-eastern Australia. A soil surface area of about 200 cm2 (to a depth of 10 cm) was required to obtain a representative individual sample (i.e. a replicate) of the number of taxa in the soil seed bank, whereas a combined area of about 1000 cm2 was required for adequacy within any treatment. The total number of buried viable seeds of all species combined was distributed spatially in a more-or-less uniform manner. This suggests that a sample whose size is sufficient for determination of species diversity of buried seeds is equally adequate for measuring buried seed density.
Survival over summer of Rhynchosporium secalis in host debris in the field
Authors: Mayfield AH , Clare BG
Published: November 2004

The ability of Rhynchosporiurn secalis to survive over summer in plant debris and to produce inoculum for scald disease development in barley crops was investigated. Viable inoculum was recovered from dead host leaves (Hordeurn vulgare and H. leporinurn) kept on soil surfaces in the field for up to 30 weeks after crop maturity in a range of South Australian barley-growing environments. When infected leaves were suspended 30 cm above soil surfaces, the fungus survived for up to 37 weeks. When buried 6 cm below soil surfaces, the fungus survived for 20 weeks. Following an initial decline in infectivity of inoculum over summer, infectivity increased during autumn to levels similar to those obtained at the start of the trials.
Photosynthetic dysfunction and in vivo changes in chlorophyll a fluorescence from manganese-deficient wheat leaves
Authors: Kriedemann PE , Graham RD , Wiskich JT
Published: November 2004

Leaves on wheat plants growing in manganese-deficient media showed much higher constant-yield fluorescence (Fo) but greatly reduced variable fluorescence (Fv). Higher Fo was symptomatic of a stronger overall emission which derived from functional changes within photosynthetic membranes and was not simply attributable to differences in leaf reflectivity of wavelengths relevant to fluorescence measurements (710-720 nm). Topical application of 4 mM MnCl, to such deficient material restored photosynthetic activity (O2 evolution by leaf slices) and also led to correlative changes in fluorescence: increased Fv, and lower Fo. Original symptoms were therefore attributable to Mn-deficiency per se. Quantitative relationships between leaf Mn concentration and certain fluorescence characteristics (the ratio Fo/Fv) were then established on flag levels excised from field plants. Critical levels of leaf Mn were discernible as an abrupt increase in the Fo/Fv ratio, once leaf Mn was below a threshold concentration, which was the minimum requirement of this element for dry matter productivity, viz. 10-12 �g Mn g-1 dry wt.
Effect of fertilizer, root and shoot competition on the growth of Siratro (Macroptilium atropurpureum) and green panic (Panicum maximum var. trichoglume) seedlings in a native speargrass (Heteropogon contortus) sward
Authors: Cook SJ , Ratcliff D
Published: November 2004

The effect of root and shoot competition and the application of fertilizer on the growth of Siratro (Macroptilium atropurpureum) and green panic (Panicum maxinzum var. trichoglume) seedlings under supplementary irrigation in an existing native grassland dominated by Heteropogon contortus was studied. The seedlings were grown in both the presence and absence of root competition and varying levels of shoot competition. Root competition was prevented by the use of steel tubes while shoot competition was varied by: clipping the native pasture to a height of either 3-5 cm or 10-15 cm every 7-10 days, leaving the native sward unclipped, and unclipped sward with wire-netting guards fitted around each seedling to prevent overtopping and facilitate light penetration. Seedling growth was assessed by determining dry weights after 29 days and also by measuring plant heights, leaf and tiller numbers and the leaf widths at 7-day intervals during this period. Application of superphosphate and nitrogen fertilizer increased the growth of both species, the initial effects being evident within 1-2 days of seedling emergence. However, at both fertilizer levels the growth of both species was primarily affected by root competition for nutrients. Where fertilizer was applied and no root competition was present heavy shading in the lower 5-10 cm of the sward canopy restricted seedling growth by reducing tiller and leaf production. The removal of shoot competition increased seedling yields fivefold whereas the removal of root competition and the removal of both root and shoot competition increased yields by 25- and 45-fold, respectively. Siratro and green panic yields were the same in the absence of root competition but Siratro yields were 11 times those of green panic where root competition was present.
Evaluation of potential genetic marker traits and estimation of outcrossing rate in Stylosanthes guianensis
Authors: Miles JW
Published: November 2004

The inheritance of flower, seed testa, and hypocotyl colour, and growth habit were studied in the F2 generation of biparental crosses between Stylosanthes guianensis accessions exhibiting contrasting phenotypes. Segregation ratios for flower colour in seven crosses and the pooled ratio supported a conclusion of single-gene inheritance, with yellow dominant to white. The data on seed colour (purple v. brown) gave inconsistent results in the two crosses evaluated. Neither red v. white hypocotyl colour nor normal v. dwarf growth habit appeared to be inherited monogenically, since a range of intermediate phenotypes was observed in the F2 populations examined. The open-pollinated progenies of 12 homozygous recessive (white-flowered) individuals within one F2 population contained yellow-flowered plants attributed to outcrossing. Overall outcrossing rate ( � s.e.) was estimated as 0.138�0.021. The proportion of yellow-flowered outcrosses in these 12 progenies was related to the number of yellow-flowered individuals adjacent to the F2 parent, indicating that pollen movement was limited within the F2 plot. Based on these findings a practical, recurrent population improvement scheme for S. guianensis is proposed.
Rumen fermentation pattern, postruminal protein flow and wool growth rate of sheep on a high-barley diet
Authors: Hynd PI , Allden WG
Published: November 2004

Variations in the wool growth rate of sheep fed diets containing cereal grains were investigated. In experiment 1, eight sheep consuming similar quantities of a pelleted diet of barley grain and lucerne chaff (60:40 by weight) were selected for high (n = 4) or low (n = 4) wool growth rate. These wool growth differences were eliminated by feeding a high-protein, predominantly roughage diet. Subsequent reintroduction of the high-grain diet regenerated wide between-sheep variance, but there was little evidence of repeatability of performance on this ration. These variations in wool growth were examined in experiment 2 in terms of rumen fermentation pattern and postruminal protein flow. Ten sheep with simple cannulae in the rumen and abomasum were given a pelleted lucerne chaff diet for 14 weeks and the high-grain diet of experiment 1 for a further 16 weeks. The variance of all measured characters was low on the lucerne diet, but the high-barley diet generated wide variance in rumen fermentation pattern, protein flow from the rumen and wool growth rate. Fermentations characterized by high ammonia level, high minimum fluid pH and high butyrate molar proportion were associated with high urinary nitrogen output, high diet digestibility and low postruminal protein flow. Wool growth rate was closely related to protein flow on the high-grain diet alone (r2 = 0.77, P < 0.01) and for the high-grain and lucerne diets considered together (r2= 0.86, P < 0.001).
Levels of heterosis for yield and quality in an F1 hybrid wheat
Authors: Boland OW , Walcott JJ
Published: November 2004

A newly released F1 hybrid wheat (Hybrid Titan) was compared with its parents and three commercial check cultivars in yield trials over 16 site years. Mid-parent heterosis varied considerably (100-127%) over the sites and averaged 111%. However, high-parent and high-check cultivar heterosis levels were much lower (99-119%), most likely a consequence of the low yield of the male parent. A concurrent seeding rate trial showed that lower levels of heterosis resulted if the seeding rate of the hybrid was reduced below that of the parent and check cultivars. Quality tests performed on the harvested grain showed some characters deviating considerably from expected values. The most significant of these were lower milling yield, flour protein content, and water absorption. The T. timopheevi nucleo-cytoplasmic system for producing hybrid wheat was implicated as having likely side effects on yield performance and quality. The study emphasized the need for both parents to be high-yielding and to have good combining ability for both yield and quality.
The separate and combined effects of barley yellow dwarf virus and take-all fungus (Gaeumannomyces graminis var. tritici) on the growth and yield of wheat
Authors: Sward RM , Kollmorgen JF
Published: November 2004

The single and combined effects of barley yellow dwarf virus (BYDV) and the take-all fungus, Gaeumannomyces graminis var. tritici (Ggt) on wheat, cv. Condor, were determined in field and glasshouse trials. Before and after tillering, aphids with BYDV were fed on plants growing in soil with different proportions of dead and live inoculum of Ggt. Each pathogen reduced grain yield and increased the number of deadheads. In a number of cases, especially in the field, the combined effect of BYDV and Ggt was greater than a simple additive effect of either pathogen alone. Grain yield per plot and grain weight per head were each reduced, whilst the incidence of deadheads was increased, particularly following infection with BYDV after tillering. A possible mechanism to explain the interaction of the two pathogens is discussed.
The accretion and distribution of carcass tissues in steers during growth between 9 and 15 months of age
Authors: Charles DD
Published: November 2004

Carcass muscle, fat and bone weights, and distribution in 12 Brahman x Hereford steers between 9 and 15 months of age were obtained by carcass side dissection. The tissue proportions of liveweight and carcass weight at mean age 13 months, and the regression estimates of tissue accretion and distribution were compared. The carcass muscle and bone components of liveweight gain decreased by 18 and 24% respectively, and carcass fat increased by 64% when all tissues were compared to composition at 13 months of age. The tissue components relative to carcass weight gain followed the same pattern. The decrease in muscle and bone growth relative to liveweight gain was greater in the hindquarters. Whereas hindquarter muscle, fat and bone were 530, 570 and 450 g/kg respectively of carcass muscle, fat and bone at the mean age of slaughter, they were 500, 570 and 420 g/kg of the respective carcass tissue accretions between 9 and 15 months. The disproportionate decrease in muscle accretion between the carcass quarters was largely a result of differences in growth among the 26 heaviest carcass muscles.
Apex and root temperature and the early growth of wheat
Authors: Aston AR
Published: November 2004

Wheat was grown in temperature controlled water-baths in order to regulate the temperature of the roots, the growing apex and the zone of leaf extension. Twenty-two alternating day and night temperatures varying between 26 and 2�C were studied. All plants experienced the same aerial environment. Leaf extension rates were measured on 6 days throughout the early growth stages and dry matter production was determined after 39 days. Night leaf extension was found to be related not only to the temperature of the meristem and leaf extension zone during the night, but also to the temperature experienced during the preceding day. Leaf extension during the day was determined by daytime temperature, and also the temperature conditions of the previous night. These growth patterns were explained in terms of leaf sugar concentrations, which were measured at the end of the experiment. Dry matter production was found to be exponentially related to the time-corrected mean daily temperature of the apex, leaf extension zone and roots. These results confirm the suggestion that the improved early vigour of wheat sown by conventional cultivation practices with a minimum of surface residues compared to direct drilled wheat, could at least partially have been due to the different patterns in soil temperature.
Corrigendum - Further studies on epidemiological factors influencing control of banana bunchy top disease and evaluation of control measures by computer simulation
Authors: Allen RN
Published: November 2004

The basic infection rate of bunchy top disease in established bananas averaged 0.0342 new infections per infectious plant per day, but varied seasonally with a maximum in summer. The mean distance of spread for the aphid vector was 15.2 m. The latent period was 59.8 days and correlated with the time required for the growth of 3.7 new banana leaves. A microcomputer program was written to simulate spread of banana bunchy top disease in space and time. In the absence of disease control, disease spread from an initial primary infection in July or January to 124 or 153 infected plants, respectively, in one year. When disease control was maintained by removing diseased plants whenever the number of infected plants exceeded a given threshold, the numbers of diseased plants detected each inspection were positively correlated with the infection threshold, but the numbers of inspections required to maintain control increased markedly as the infection threshold was decreased. A practice of removing apparently healthy plants within 5 m of plants detected with bunchy top disease symptoms in five or more leaves was found to locate about 30% of the remaining undetected infected plants when disease was first detected in a plantation. However, its use as a routine control measure was ineffective in reducing the number of inspections required to maintain control or in reducing the risk of disease spreading to adjoining plantations. Removal of apparently healthy plants within 5 m had some bearing on disease control when applied around plants with disease symptoms in two leaves or less, but also caused a significant loss of healthy plants.
Effects of previous and current anthelmintic treatments on productivity in Merino hogget sheep
Authors: Thompson RL , Callinan APL
Published: November 2004

The effects of various drenching programs for hogget (2-year-old) sheep, on productivity in subsequent years was studied at the Pastoral Research Institute at Hamilton during 1976-78. In 1976, liveweight gains and fleeceweights in hoggets were significantly (P < 0.01), dependent on drenching programs in their first year after weaning. Sheep which had been drenched at weekly intervals as weaners in 1975 had significantly (P < 0.01) reduced liveweight gains as hoggets during 1976, regardless of whether they were drenched or not in that year. In 1977 and 1978 previous drenching had a significant effect on liveweight gain in hoggets (P < 0.01) but not fleeceweights (P > 0.12). Sheep drenched at weekly intervals as weaners, then left undrenched as hoggets, had the lowest liveweight gains of any group. Liveweight gains and fleeceweights measured at the end of the third year were unaffected by previous drenching history (P > 0.15). Frequent drenching of weaners may not increase their productivity, and productivity losses due to underdrenching weaner sheep may be compensated for in subsequent years.
Physiological relationships with production measures in White Leghorns subjected to restricted feeding from 18 weeks of age
Authors: Glatz PC , Polkinghorne RW , Howard B
Published: November 2004

The relationships between 22-42 week production measurements (egg number, egg weight, feed conversion efficiency, carcass fat, shell thickness and body weight) and a number of physiological measures (metabolic rate, water turnover, thyroxine secretion rate and plasma thyroxine concentration) were examined in purebred and strain-cross White Leghorn hens. Feed intakes were restricted to 80, 90 or 100 g 24h-1 and comparisons made with birds allowed free access to feed (average 127 g 24h-1). Restricted feeding significantly depressed all production measures except egg weight and shell thickness, and also reduced metabolic rate but elevated the plasma thyroxine concentration. Strain-cross hens laid more and heavier eggs, and showed a better feed conversion efficiency than purebreds in association with reduced metabolic rates, thyroxine secretion rates and plasma thyroxine concentrations. Water turnover was the only physiological measure to be consistently related to production measurements, and in the case of egg number, egg weight and shell thickness, different relationships were demonstrated in restricted compared with fully fed birds.
Effects of foliar applied nitrogen fertilizer on cotton waterlogged in a cracking grey clay
Authors: Hodgson AS , MacLeod DA
Published: November 2004

Foliar-applied nitrogen (N) fertilizer was investigated as a means of ameliorating the damage to cotton of waterlogging associated with extended furrow irrigation of a cracking grey clay. Dissolved urea was applied at 0, 5, 10 and 20 kg N ha-1 to the cotton foliage one day before furrow irrigations lasting 4, 8, 16 and 32 h. Treatments were repeated at three crop irrigations. Storms following the first two irrigations delayed the recovery from waterlogging and reduced treatment differences. However, foliar-applied N significantly increased late square and green boll numbers after the third irrigation, and produced more open bolls and heavier lint yields than the control treatment at harvest. Lint yields increased by 2.8, 5.9, 8.4 and up to 10.5 kg ha-1 per kg of foliar N applied before irrigations lasting 4, 8, 16 and 32 h, respectively. From this interaction it was concluded that foliar-applied N ameliorated the effects of waterlogging. Nevertheless, in the most severe waterlogging treatment, yield response to foliar N reached a limit, indicating that some other factor had become limiting.
Seasonal variation in the infectivity of VA mycorrhizal fungi in annual pastures in a Mediterranean environment
Authors: Scheltema MA , Abbott LK , Robson AD
Published: November 2004

The seasonal variation in the rate and extent of formation of mycorrhizas in pasture soils from two sites in south-west Australia was examined. Undisturbed soil cores were taken on eight occasions throughout the year, sown with Trifolium subterraneum L. and maintained in a glasshouse. At each collection time the extent of formation of mycorrhizas was measured 3 and 6 weeks after sowing.There was no seasonal variation in the extent of mycorrhizas formed in undisturbed soil cores at one site, hut at the other site the extent of mycorrhizas decreased over time. The rate of formation of mycorrhizas was most rapid when cores were collected immediately after the opening rains of the season.Similar species of fungi were present at both sites; however, the rate and extent of infection formed by each species differed between the sites. At both sites the infectivity of A. laevis and fine endophyte decreased throughout the winter months, but the infectivity of Glomus spp. did not change. Neither the total spore number nor an estimate of the number of infective propagules reflected the infectivity of the total population of VA mycorrhizal fungi measured simultaneously at the two sites.