bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of sheep grazing Astrebla grassland in central western Queensland. 2. Effects of seasonal rainfall
Authors: Orr DM
Published: November 2004

The response of Astrebla grassland pasture to summer rainfall was measured at sites in commercially grazed paddocks which were subject to different grazing pressures. The interrelationship between forage use and plant variates was examined by regression analysis. Above-average rainfall resulted in increases in basal area and projected foliage cover of Astrebla spp. under grazing pressures equivalent to 50% forage use of A. lappacea. Increased forage use in the dry period before this rainfall reduced the basal area and projected foliage cover of Astrebla and resulted in lower yields of Astrebla following the rainfall. These lower yields of Astrebla were associated with higher yields of annual grasses and forbs than where forage use had been light. Astrebla yields were highest under light forage use. The frequency of two undesirable species, Amaranthus niitchellii and Tribulus terrestris, was highest under heavy forage use, and was associated with a decline in the number of other annual grass and forb species.
Effects of a water stress on the photosynthesis and respiration of wheat ears
Authors: Marshall B , Sedgley RH , Biscoe PV
Published: November 2004

An experiment was conducted on Huntsman winter wheat to investigate the effects of a water stress applied at anthesis on the carbon dioxide exchange of the ears during grain filling. The water stress was created by excluding rain from the soil, not the foliage, of plants growing in the field. Control plants were well watered throughout the period when the treatment was imposed. At intervals for 32 days after anthesis, detailed measurements were made of the photosynthetic rate of ears at different irradiances and rates of ear dark respiration. The measurements were analysed by using the photosynthesis-light response model developed by Marshall and Biscoe (1980) for wheat leaves with a modification for the pathway of respiration from the grains to the glumes. The model is a non-rectangular hyperbola and uses four parameters: Pn,max (maximum rate of net photosynthesis), Rd (rate of dark respiration), � (photochemical efficiency at low light), and F (ratio of physical to total resistance to diffusion of carbon dioxide). Analysis showed that in wheat ears during grain filling, photosynthesis can be treated as occurring predominantly in the glumes and respiration in the grains. The shape of the photosynthesis-light response curves for ears from both treatments were similar, but differed from those for wheat leaves because the maximum rates of photosynthesis were reached more gradually with increasing irradiance. However, the measured response curves were still better fitted by the model than a rectangular hyperbola which has often been used in the past. The water stress at anthesis decreased the maximum rate of ear photosynthesis by 0.8 g carbon dioxide m-2 h-1 throughout the grain-filling period. Initially, the rates of ear respiration were the same, but 32 days after anthesis the treatment had decreased ear respiration rate from 0.04 to 0.01 g carbon dioxide h-1/grain.
Selenium supplementation of grazing sheep. II. Responses in plasma and erythrocyte activities of lambs and adult wethers
Authors: Peter DW
Published: November 2004

The possibility that apparently healthy lambs in the low selenium region of New England in New South Wales may suffer from subclinical nutritional muscular dystrophy (NMD) was investigated. Further studies of the response in plasma activities of the seleno-enzyme, glutathione peroxidase (GSH-px), to selenium drenching were also included. Changes in the GSH-px and glutathione reductase (GR) activities of erythrocytes and plasma and in the activities of several other plasma enzymes were monitored before and after selenium treatment, by oral drench, of lambs and adult wethers maintained in the field. Similar enzyme measurements were made in adult wethers brought indoors and given a pelleted lucerne ration containing adequate selenium. Selenium treatment caused a large, rapid but transient increase in the initially low plasma GSH-px activities of the lambs. With the exception of one animal, similar changes did not occur in the wethers drenched with selenium. However, in the 14 days prior to treatment the GSH-px activities of all wethers increased and on the day of treatment activities were substantially higher than those of the lambs; increases continued in both grazing and pen-fed wethers irrespective of treatment. The selenium content/availability of the pasture grazed by the wethers was apparently higher than that grazed by the lambs and their dams and the main flock from which the wethers were selected. Plasma activities of glutamic oxalacetic transaminase, creatine phosphokinase and sorbitol dehydrogenase of both lambs and wethers fell within normal ranges at all times. These activities indicated that the lambs, despite a low selenium status prior to treatment, were not suffering from subclinical NMD and that the rapid increase in their plasma GSH-px activity following selenium treatment was not due to acute selenium toxicity and tissue damage. The response in plasma GSH-px activity appeared to depend upon the selenium status of animals at the time when selenium was administered.
Selenium supplementation of grazing sheep. III. Effects of supplementation of ewes before and/or after lambing on the selenium status, blood enzyme activities and the growth of their lambs
Authors: Peter DW
Published: November 2004

The effects of oral selenium administration to ewes during pregnancy and/or following parturition on ewe fertility, the selenium status of the ewes until lambing and of their lambs from birth to 70 days of age, on plasma enzyme activities and on lamb growth were investigated by using four groups of ewes grazing pasture in the low selenium region of New England. Selenium treatment prior to parturition resulted in significantly higher activities of erythrocyte glutathione peroxidase, i.e. a higher selenium status, of both the ewes and their lambs at lambing, though the selenium status of untreated ewes and their lambs was considered adequate. There were significant increases in the activities of erythrocyte glutathione peroxidase of lambs following selenium supplementation of their dams at parturition, whereas activities of lambs with untreated dams declined; depending on the selenium status of the dam, lambs received varying selenium supplements via milk. There were no significant effects of selenium treatment on ewe fertility or on the patterns of growth of the groups of lambs. However, from 49 days of age onwards, lambs whose dams received selenium at parturition were significantly heavier than lambs whose dams did not receive supplementary selenium. The results are discussed in relation to recommended schedules for oral selenium supplementation and the diagnosis of selenium inadequacy in grazing sheep.
Response to partial selection on clean fleece weight in South Australian strong-wool Merino sheep. V. Estimation of genetic gain by contemporary comparison of progeny of sires two years apart in age
Authors: Mann TLJ , Ponzoni RW , Polkinghorne RW
Published: November 2004

Genetic gain per year in clean fleece weight was estimated in a flock under partial selection for that trait by comparing the progeny of 1+,-year-old rams with the progeny of 3+-year-old rams. Three mathematical models were fitted to the data. Model 1 included years, ram ages, type of birth, age of dam and sex as main effects, plus all possible two-way interactions. Model 2 was as model 1, but it included also the sire selection intensity as a linear covariate. Model 3 was as model 1 with the addition of sires as a random effect nested within years and ram ages. The three models fitted gave similar results. The estimate of genetic gain in clean fleece weight was 0.12 kg per year and was statistically significant (PC 0.05) when models 1 and 2 were fitted, while it bordered the 5% level of significance (P � 0.07) when model 3 was fitted. The present estimate of genetic gain is somewhat greater than the one observed in other experiments, even though 70% of the rams were rejected visually before selection for clean fleece weight took place. The results are discussed, and the limitations of the experimental design adopted for the experiment are stressed.
Associated growth of wheat and annual ryegrass. III. Effects of early competition on wheat
Authors: Rerkasem K , Stern WR , Goodchild NA
Published: November 2004

The effects of four factors applied in factorial combination, viz. nitrogen application, time of ryegrass germination relative to wheat, roots together or separate and species proportion, were studied during the first few weeks of the associated growth of wheat and annual ryegrass. The experiment was conducted in boxes in a glasshouse at a total density of 355 plants m-2. Many plant variates were measured at 7, 28 and 49 days from sowing. Nitrogen content was determined at 28 and 49 days. Even at 7 days, measurable treatment effects on root and shoot weights of wheat could be detected. The effects could be discerned subsequently in terms of root length, tillering patterns, shoot weight, and ear development. Effects on ear development were observed in the last tiller and on the most recently developed florets. Some of these responses involved interactions of two or more of the factors studied. Treatments modified the relationship between competitive ability and yield in pure culture, more in ryegrass than in wheat. Although nitrogen effects appeared to have a strong influence on the competitive relations between the species, it is suggested that competition for soil factors other than nitrogen may also have been involved.
Zinc availability to young wheat plants in Darling Downs black earths
Authors: Radjagukguk B , Edwards DG , Bell LC
Published: November 2004

A pot experiment in which wheat cv. Timgalen was grown in a glasshouse for 6 weeks clearly established that some of the 12 Darling Downs black earths investigated were zinc deficient. Rates of application between 1.2 and 3.7 kg zinc ha-1 (as ZnSO4.7H2O) were sufficient to achieve maximum or near-maximum dry matter yield of tops on the deficient soils. Plant zinc concentration and total zinc uptake in the tops increased in all soils with increasing rates of zinc application. The critical zinc concentration in the wheat tops associated with 90% of maximum dry matter yield was 20 �g g-1. Three extraction methods were used to determine the initial available zinc status of the soils. All methods gave lower extractable zinc values in the acid (pH <7 . 0 in 0.01 M calcium chloride) black earths (Mywybilla soils) than in the alkaline black earths. Critical extractable zinc values were much lower in the acid black earths. EDTA-ammonium carbonate (pH 8.6) more effectively separated zinc-deficient and marginally deficient from adequately supplied alkaline black earths than either EDTA-ammonium acetate (pH 7.0) or DTPA (pH 7.3). The critical extractable zinc value for the alkaline black earths with EDTA-ammonium carbonate was 0.61 �g g-1.
Genotype × environment interactions for resistance to Kabatiella caulivora in Trifolium subterraneum subspecies yanninicum
Authors: Beale PE , Goodchild NA
Published: November 2004

Genotype x environment interactions of resistance to clover scorch in Trifoliurn subterraneurn subspecies yanninicum were studied by growing 11 subterraneum clover genotypes at three sites in Western Australia and one site in South Australia. Similar data from the previous year at one site were utilized to study genotype x season interactions. Clover scorch damage was assessed by scoring at fortnightly intervals from which total disease development was calculated. A combination of established methods called by us significant rank order, in which analysis of variance is followed by a ranking process, is developed and discussed. Interactions based on significant rank order are demonstrated, and the implications of these interactions for plant breeding strategies are discussed.
Effects of nutritional state on responses of Hereford steers to enforced exercise in a hot environment
Authors: Murray DM , Schmidt PJ , Yeates NTM
Published: November 2004

The physiological responses of two groups of steers to enforced exercise (walking) in a warm environment were studied on four consecutive days. Prior to the walking trials, the groups were fed to either lose (low plane) or gain (high plane) weight. On day 1 and the morning of day 2, the low and high plane groups were fed, respectively, on a restricted amount of oaten hay or a lucerne chaff-wheat mixture ad libitum. At the afternoon feeding and after exercise on day 2, the diets were reversed for the remainder of the study. Thus, physiological measurements on days 1 and 2 were made before, and those on days 3 and 4 after, the reversal of diets. On days 1 and 2, high plane animals exhibited a lower walking endurance and higher rectal temperatures and respiratory rates after 2 h of exercise than low plane animals. Sweating rates immediately after exercise were also greater in high plane animals, which suggests that their inferior walking ability was not due to a lower cutaneous heat loss. Between-group differences in walking ability are postulated to have resulted from differences in heat production on the two diets. On days 3 and 4, walking endurance, and rectal temperatures and respiratory rates after 2 h of exercise were similar in both groups although high plane animals recorded greater sweating rates after exercise on both days. Contrary to expectations, low plane animals showed lower physiological responses to exercise when they were fed on the lucerne chaff-wheat ration. A possible explanation is offered for these lower responses of low plane animals.
Egg weight responses to dietary supplementation with sunflower oil and rice pollard
Authors: Srichai Y , Balnave D
Published: November 2004

Maximum egg weight was not attained by feeding a layer diet based on wheat, sorghum and meat meal to White Leghorn x Australorp pullets and second year hens, but substantial increases were obtained by substituting sunflower oil or rice pollard on an equi-energetic basis. This effect was most marked when high dietary concentrations of rice pollard were used. The improvement in egg weight was associated with increases in dietary linoleic acid concentration and intake, but not with the intakes of other major nutrients, including metabolizable energy and essential amino acids. It appears that the linoleic acid content of rice pollard was the major, if not necessarily the only, factor responsible for the observed beneficial responses in egg weight.
Genetic analysis in the pasture grass Setaria sphacelata. II. Chemical composition, digestibility and correlations with yield
Authors: Bray RA , Hacker JB
Published: November 2004

The progeny of a 7 x 7 diallel cross between plants randomly selected from a segregating tetraploid population (Setaria sphacelata var. sericea and var. splendida) was studied at Lawes, south-east Queensland, over a two year period, together with the parent clones. Plants were harvested at 6-week intervals (9-10 weeks in winter), dry weight was recorded, and family rows were bulked for analysis of in vitro digestibility (DMD) and for multi-element analysis. Concentrations of nitrogen, phosphorus, magnesium and calcium tended to be low in summer, and potassium concentration decreased during the two years of the experiment. In contrast magnesium, calcium and sodium increased. Genetic variance for digestibility was detected for only two of 14 harvests. Additive genetic variance was statistically significant, and generally consistent over harvests for nitrogen, potassium, sodium, calcium and magnesium. Family by season and family by year interactions were of a low order, showing that the expression of genetic variance was not strongly influenced by seasonal effects. Additive variance effects were erratic for phosphorus, sulfur, manganese, copper, zinc, silicon, iron, aluminium and boron, and selection for higher or lower concentrations of these elements would be unlikely to be successful. Nitrogen, potassium, calcium, magnesium and sodium were negatively and consistently correlated with dry matter yield. Over all harvests r was - 0.64, - 0.16, - 0.77, - 0.30 and - 0.44 respectively. With the possible exception of potassium, selection for higher concentrations of any of these minerals would result in a decrease in yield. Sodium was negatively correlated genetically with nitrogen, potassium, calcium and magnesium on an individual harvest or a season basis. For the total of all 15 harvests values for rg were -0.76, -0.88, -0.21 and -0.73 respectively. Nitrogen, potassium, calcium and magnesium were consistently positively correlated (for all harvests rg - 0.69 for all combinations), and selection for high concentration of any of these elements would result in an increase in the others, but a decrease in sodium. Significant genetic variation was detected for the mineral ratios K:(Ca + Mg) and calcium: phosphorus. However, these ratios are not known to adversely affect production in setaria pastures, and manipulation by breeding is not warranted. These examples show that there is the potential for breeding for mineral ratios in tropical forages.
Histological studies of the pre-penetration development and penetration of soybeans by rust, Phakopsora pachyrhizi Syd
Authors: McLean RJ , Byth DE
Published: November 2004

Comparisons were made between susceptible, resistant and highly resistant soybean lines of pre-penetration development and penetration of uredospores of rust, Phakopsora pachyrhizi, at intervals after inoculation. Differences between lines were found in the percentage of uredospores which germinated on leaves, and smaller differences were found between lines in appressorium formation and penetration from germinated uredospores. The differences between lines were not related to infection type.
The influence of weather on the quality of tropical legume pasture during the dry season in Northern Australia. I. Trends in sward structure and moulding of standing hay at three locations
Authors: McCown RL , Wall BH , Harrison PG
Published: November 2004

In seasonally dry tropical climates, animal production is severely constrained during the dry season by the low nutritive value of dry grass forage. Introduction of a legume such as Caribbean stylo can provide a valuable alternative forage during this period, mainly in the form of leaf litter and accompanying seed. The actual contribution of dry legume is closely dependent on its moisture regimen, which determines the degree of mould growth, an important palatability factor. This paper reports a 2-year study conducted at Katherine, Darwin and Townsville of the environmental control of both the timing and rate of leaf shed and of the subsequent moulding of leaf litter. At Katherine and Darwin, leaf was shed early and rapidly; at Townsville, much lower evaporation rates and small rainfalls delayed and prolonged leaf shed by several weeks. The data provide a model for predicting leaf shed by using standard weather data to aid the assessment of the risk of forage damage by precipitation.
Genetic studies of South Australian Merino sheep. I. Genetic change in fleece and body traits
Authors: Gregory IP , Ponzoni RW
Published: November 2004

During the years 1953-67 one flock of South Australian Merinos was selected on clean fleece weight (the Index flock) and another on the basis of visual appraisal (the Visual flock). A large number of qualitative and quantitative traits were recorded. Linear regressions of differences between flock means on time were estimated for each trait; not many of the regressions were significant. However, greasy and clean fleece weights of Index animals increased significantly faster than those of Visual animals, and body weights of Visual animals increased significantly faster than those of Index animals. Realized selection differentials were estimated for all traits. There were significant selection differentials for greasy and clean fleece weights and yield in the Index flock, and for body weight and greasy fleece weight in the Visual flock. The response to selection was estimated for all traits by using two methods; regression of the trait on an individual's generation number, and comparison of the deviation from the overall mean of the mean of the progeny of a 3+-year-old sire with the deviation of the progeny of the same sire as a 2+-year-old. The estimate of genetic change in body weight was higher and genetic changes in clean and greasy fleece weights lower in Index animals, which was in contrast with an earlier result. However, when the least-squares means of these traits were compared, it was concluded that the Index flock did, in fact, achieve significantly greater responses in greasy and clean fleece weights and a significantly lower response in body weight than the Visual flock. It was therefore considered that, in these particular experiments, both methods of estimating genetic change had serious limitations.
Genetic studies of South Australian Merino sheep. 2. Environmental effects on wool and body traits at 15-16 months of age
Authors: Gregory IP , Ponzoni RW
Published: November 2004

The effects of years, sex, type of birth (i.e. whether or not multiple birth) and age of dam on 26 wool and body traits of South Australian Merino sheep were estimated by least-squares analysis. Years and sex had highly significant effects on all traits. Of the main production traits, type of birth had a significant effect on body weight, greasy and clean fleece weight and total wool follicle number, while age of dam only had a significant effect on body weight and greasy fleece weight. The possible consequences of failing to correct body weight and greasy and clean fleece weights for type of birth and age of dam were considered and it was concluded that, although in some years correction of these traits may not be warranted, in other years correction may be necessary to prevent selection against fecundity and an increase in the generation interval. The main components contributing to the 6.0 % difference between fleece weights of singles and twins were surface area, total follicle number and wrinkle score. The difference between fleece weights of animals from older ewes and animals from maidens was only 1.5 %; surface area was the main contributor to this deviation.
The analysis of the distribution of conception times in beef heifers
Authors: Cunningham RB , Axelsen A , Morley FHW
Published: November 2004

A statistical model, developed by Bartlett for the analysis of grouped survival data, is presented as a method for analysis of data on times to conception. It is shown, for 458 15-month-old heifers, that conception times can be described by a Weibull distribution, the parameters of which depend strongly on breed, age and nutrition group. Liveweight at the start of joining accounted for almost all of the variation explained by the factor 'nutrition'. Conception rate was low and delayed in the lightest heifers (<181 kg at the start of joining), but Angus (A) heifers of this weight were more likely to conceive than were Angus x Friesian (AX F) or A x (A x F) heifers. Also, at a given liveweight younger heifers were less likely to conceive. Overall, conception rates were high for heifers > 210 kg at the start of joining. Graphs are presented relating probabilities of conception with breed, age and liveweight at the start of joining.
Selection for efficient lean growth in a pig herd
Authors: McPhee CP
Published: November 2004

A pig herd was selected for 6 years by using an economic index combining growth rate, food conversion efficiency and carcass leanness. These three traits were all measured in a performance test which permitted appetite variation between pigs to be expressed. Boars selected with an intensity of 118 were used for 6 months, and sows with an intensity of 114 were kept for two farrowings. An unselected control herd was maintained concurrently. To measure selection response, selected (S) and control (C) pigs were compared as they grew from 25 to 90 kg liveweight on ad lib. and restricted feeding during the last 2 years of selection. The following significant (P < 0.05) responses occurred in the selection herd: (i) A slight increase in growth rate on restricted feed, balanced by a similar decrease on ad lib, feeding. (ii) A decline in food conversion ratio of 5 % (C, 2.79; S, 2.65) due mainly to a reduction in appetite. (On ad lib. feeding, food intake per day declined by 6 % (C, 2.30 kg/d; S, 2.16 kg/d.)). (iii) A decline in average subcutaneous fat depth by 11 % (C, 27.8 mm; S, 24.7 mm) and in fat dissected from the ham by 7 % (C, 2.80 kg; S, 2.61 kg). (iv) An increase in estimated lean in the carcass by 2% (C, 30.3 kg; S, 31.0 kg). (v) A decline in dressing percentage of the carcass by 1 % (C, 77.1 %; S, 76.2 %). There was no change in eye muscle area or carcass length. The results are discussed in terms of changes in the ratio of food intake to lean growth. In the group fed ad lib., this ratio declined by 7 %, mainly because of a decline in food intake. On restricted feeding it fell by 6 %, mainly owing to an increase in lean growth. That portion of the selection effort absorbed in reducing food intake may have been more profitably directed to increasing lean growth by suppressing appetite variation during performance testing, rather than allowing it to be expressed.
Yield losses in wheat from yellow spot: a disease-loss relationship derived from single tillers
Authors: Rees RG , Mayer RJ , Platz GJ
Published: November 2004

The effect of yellow spot (Pyrenophora tritici-repentis) on wheat yield has been examined with a single-tiller technique. The disease was assessed on c. 1000 tagged main stems in each of five wheat crops. Grain yield, its components, and harvest index were measured on each tiller. In most cases these response variables were significantly correlated with yellow spot levels. The disease-loss relationship, L = 0.26X, was developed where L is the percentage loss in grain yield per main head and X is the average level of yellow spot on the top two leaves at around the milk stage of grain development. From four of the crops examined, an average loss of 12.7 % in grain yield per main head was estimated. Under environmental conditions which particularly favour disease development, the losses derived from this relationship are probably underestimated.
Ecological field studies on Anguina funesta, the vector in annual ryegrass toxicity
Authors: McKay AC , Fisher JM , Dube AJ
Published: November 2004

Entry of second-stage juveniles (J2) of Anguina funesta into the apex of Lolium rigidum was dependent on environmental conditions and so varied in 1978 and 1979. Penetration and initiation of galls dependent on stage of development of the plant, was more consistent and occurred in late August-early September. Two to three nematodes initiated each gall. The first egg was deposited at the end of September and the first J2 hatched in mid-October. The implications of these observations for control are discussed. Mowing and grazing, the fungus Dilophospora alopecuri, and good clover growth all showed promise in reducing numbers of the nematode.
Breeding systems in Stylosanthes. I. Observations of outcrossing in S. scabra at an alcohol dehydrogenase locus
Authors: Stace HM
Published: November 2004

A polymorphism for seed alcohol dehydrogenase (ADH) occurs in Stylosanthes scabra CPI 40205, a species currently being evaluated for cattle grazing in North Queensland. S. scabra (2n = 40) is normally a true breeding fixed heterozygote at the Adh locus, consistent with it being a partial or complete allotetraploid. The polymorphic population contains fixed heterozygotes (typical for the species), simplex heterozygotes and slow homozygotes. An estimate (� s.e.) of outbreeding amongst the progeny of homozygotes is t = 1.8 � 0.45 %. The origin of the polymorphism is unclear, but it is suggested that an event (possibly some form of hybridization) during the seed multiplication phase broke down the preferential pairing which is presumed to be the basis of the stabilized heterozygosity of the allotetraploid.
Effects of a concurrent infection of Trichostrongylus colubriformis on the productivity and physiological and metabolic responses of lambs infected with Ostertagia circumcincta
Authors: Steel JW , Jones WO , Symons LEA
Published: November 2004

Weaner lambs were infected for 16 weeks with 900 or 3000 Trichostrongylus colubriformis larvaelweek alone, with 38 000 Ostertagia circumcincta larvaelweek alone, or with the two parasites concurrently at these dose levels. Concurrent infections with T. colubrifovmis, which when given alone had no significant effect, reduced liveweight gain by 15 kg over the 16-week infection period compared with a 6-kg reduction in liveweight of lambs infected with O. civcumcincta alone. T. colubvifovmis when given alone did not affect wool growth, but with concurrent infections wool growth was reduced by up to 66% compared with a 25 % reduction in lambs infected with O. circunzcincta alone. This greater loss of productivity in concurrent infections was principally due to reduced food consumption, and was exacerbated by a substantial decrease in the efficiency of retention of apparently digested nitrogen. These effects were accompanied by an elevated gastroenteric plasma loss, and a concomitant decrease in albumin synthesis which together were considered responsible for the more pronounced hypoalbuminaemia observed in lambs with concurrent infections. Reasons for impaired nitrogen utilization in concurrently infected lambs are discussed.
A comparative study of Hereford and Friesian steers. 1. Growth, feed conversion and body dimensions
Authors: Taylor DG
Published: November 2004

Two trials were carried out to investigate the beef producing potential of Hereford and Friesian steers, representatives of the traditional 'beef' and 'dairy' types respectively. Four Hereford and four Friesian steers were individually fed on a high grain ration to achieve an average liveweight gain of 0.68 kg/day. A similar group of steers were given the same ration ad libitum to enable a study of the growth rate potential of the two breeds to be made. Amongst the ad libitum fed animals the Friesians exhibited a significantly greater average daily gain than the Herefords. The Herefords, exhibiting their early-maturing capabilities, began a period of accelerated subcutaneous fat deposition at about 11 months of age, while the Friesians showed only a slight and constant increase in fat thickness up to slaughter at 12.5 months of age. No significant between-breed differences in feed conversion ratio were detected in either the controlled fed or ad libitum fed steers. At 15 months of age, marked differences in body size were recorded, the Friesian being taller and longer than the Hereford. The Hereford displayed the more desirable 'beef type' conformation, as measured objectively by the Muscle/Skeletal Index.
Phenology of sunflower cultivars. I. Classification of responses
Authors: Goyne PJ , Hammer GL , Woodruff DR
Published: November 2004

The phenology of commercial sunflower cultivars available to Queensland growers in 1979 was studied in monthly plantings over a 12-month period at Toowoomba in southern Queensland. By using pattern analysis procedures, the cultivars were classified into three maturity groups, viz. 'Very Quick', 'Quick' and 'Medium', based on the number of days from emergence to the head-visible stage of growth. Most of the cultivars belonged to the Quick and Medium maturity groups. Cultivar differences were most obvious for plantings in the cooler months (March to October). To classify new releases, one or two plantings during this period as well as one planting in summer is recommended. Sunfola 68-2 and Hysun 30 should be included in these plantings as cultivars representative of the two major maturity groups. The study showed that there was very little genetic variability in phenology in the present commercial cultivars and there was little difference in phenology among cultivars in the main summer planting period.
Effect of breed of dam and lamb, and of lamb sex on efficiency of conversion of food to lamb and wool in Merino and first-cross Merino ewes
Authors: Kleemann DO , Dolling CHS , Ponzoni RW
Published: November 2004

The effects of breed of dam (Merino (M), Border Leicester x Merino (BL x M) and Poll Dorset x Merino (PD x M)), breed of lamb (Suffolk sired (S)) and sex of lamb (castrate male, female) on the efficiency of the ewe (organic matter intake per unit metabolic weight and clean wool weight per unit intake) and on the efficiency of the ewe-lamb unit (liveweight and carcass weight per unit intake) were examined. The effects of breed of dam and breed of lamb were differentiated by a system of cross-mothering of all lambs at birth. Each lamb was slaughtered at = 35 kg liveweight. The two crossbred types ate less organic matter per unit metabolic weight than did M dams during late pregnancy, but there were no differences during lactation. Compared with the absolute intake of M dams, PD x M and BL x M ewes ate 11 and 18 % more throughout the experimental period (224 days). The conversion efficiencies of food to wool of PD x M and BL x M dams were 59 and 66 % of that of Merinos. There were no significant differences between breeds of lamb or between lamb sexes for either intake per unit metabolic weight or clean wool growth per unit intake of the ewe. There were no significant differences between breeds of dam or between lamb sexes for either lamb liveweight or carcass weight per unit intake. This applied whether the lambs were at the same age or at the same liveweight. Ewes rearing S x (PD x M) and S x (BL x M) lambs had higher carcass weights per unit intake than did those rearing S x M lambs.
The use of multidimensional scaling in analysing multi-attribute genotype response across environments
Authors: Basford KE
Published: November 2004

Three-way Multidimensional Scaling is presented as a single analysis of genotype x environment x attribute data. The concept and underlying model of this technique are discussed, and its usefulness is investigated by applying the analysis to a well-known soybean data set. The measured attributes were considered to represent the line response in each environment. It was assumed the lines could be considered in an underlying space of r dimensions. The environments were able to perceive different response patterns in that different importances could be placed on these underlying dimensions. By applying this technique a spatial representation of the lines in a low-dimensional space was obtained. Thus a single multi-attribute analysis is achieved rather than attempting to combine separate analyses for each attribute. The resulting line response pattern was examined in relation to previous reports on this data set. The inclusion of all six attributes revealed information not previously obtained by separate analysis of two of these attributes. If general inference about genotype response is to be made rather than inference on one particular attribute, then the use of a technique such as this is recommended.
The effect of temperature on growth and dry matter production of avocado plants
Authors: Lahav E , Trochoulias T
Published: November 2004

Grafted cv. Fuerte and cv. Hass avocado plants were grown for 81 days in sunlit growth chambers at day/night temperatures of 17/10, 21/14, 25/18, 29/22, 33/26 and 37/30�C. Stem diameter, length of side branches, the number of leaves, leaf area and plant height, were all greater in the 21/14 to 33/26�C temperature range, than at temperatures of 17/10�C and especially 37/30�C, which restricted growth in both cultivars. Total dry matter accumulation by Fuerte was greatest at 25/18�C, while Hass was less affected by temperature extremes. High temperatures produced maximum dry matter in the leaves, while low temperatures produced it in the roots. Temperatures of 37/30�C reduced root growth and dry matter accumulation by 60-70% as compared with the optimal treatments. It is suggested that under high temperature conditions measures should be taken to cool the soil. The Fuerte plants were more affected by temperature extremes than were the Hass plants which had a broader range of optimal growth response. Therefore cv. Hass could be expected to adapt better to extreme temperature conditions. Hass plants grown under high temperatures exhibited a greater leaf diffusive resistance than Fuerte and are therefore more capable of reducing water loss from the leaves. As temperatures decreased, more red pigment was evident in the young flush of both cultivars.
Jojoba flower buds: effects of preconditioning temperature.
Authors: Dunstone RL
Published: November 2004

The environmental factors which control the reproductive cycle of jojoba (Simmondsia chinensis [Link] Schneider), were studied under controlled conditions. Plants were placed under a warm pretreatment temperature which resulted in the growth of new shoots bearing dormant flower buds. The plants were later moved to lower treatment temperatures which have been shown to break flower bud dormancy. Pretreatment temperature affected the percentage of nodes which produced flower buds. Both the pretreatment and the treatment temperature affected flowering percentage, there being an optimum pretreatment effect at 30/25�C day/night temperatures. Flowering percentage responded to absolute treatment temperature rather than to the drop in temperature from pretreatment to treatment. Flowering percentage increased with decrease in treatment temperature down to 15/10�C (male clone) and 12/7�C (female clone). The lowest pretreatment-treatment temperature combination was associated with the production of female flower parts on the male inflorescences.
The association between lambing status and future reproductive performance of ewes grazing oestrogenic pastures
Authors: Ponzoni RW , Walker SK
Published: November 2004

Eight flocks of ewes grazing improved pastures which contained oestrogenic clover (Trifolium subterraneum cv. Yarloop) were studied. Two data-sets were available for analysis: Data-set 1-four flocks, three with age-structure unknown. Records on the number of ewes lambing per ewe exposed to the ram (EPJ) and the number of lambs born per ewe exposed to the ram (LBJ) were collected during 1972-75. The repeatability of EPJ and LBJ were estimated within flocks by the regression methods. There was considerable variation between flocks in the values obtained. An analysis of variance was conducted including lambing status (0, 1 or 2 lambs at birth) of the ewes in 1972 as a main effect. Class 1 ewes had a better reproductive performance in subsequent years than either class 0 or class 2 ewes. The effects on flock performance of culling barren ewes were simulated, showing that little improvement in subsequent performance would result. Data-set 2-four flocks, age-structure known. EPJ and LBJ were recorded in 1973 and 1974. The repeatabilities of EPJ and LBJ were estimated within age groups of each flock by regression methods. The results were less variable than in data-set 1. An analysis of variance was conducted, including lambing status (0 or 1 lamb at birth) in 1973 as a main effect. Class 1 ewes had a better reproductive performance in 1974 than class 0 ewes. Simulation of the effects of culling ewes which were barren in 1973 showed that only a small improvement in reproductive performance of ewes in 1974 could be obtained. It was concluded that the culling of barren ewes is unlikely to provide a solution to the low reproduction rate of ewes grazing oestrogenic pastures.
Ingestion rates, food utilization and turnover of water and sodium in grazing buffaloes, Bubalus bubalis, and cattle, Bos taurus × B. indicus, in monsoonal Northern Territory
Authors: Williams CK , Dudzinski ML
Published: November 2004

Cows and steers of swamp buffalo and Brahman x Shorthorn cattle grazing freely in a paddock of pangola grass pasture during a monsoonal dry season were compared over 14 days in body composition, rates of sodium and water turnover, and rates of food ingestion by using the isotope dilution method. The cattle, especially the steers, had a higher proportion of body solids than the buffalo and appeared to have a higher proportion of body fat. There were significant interactions of species with either sex, castration or both in the proportions of body water and solids. The differing body compositions had a marked influence in comparisons of physiological rate parameters between the buffalo and cattle. The buffalo had higher rates of water turnover than the cattle and the two species had similar rates of sodium turnover when standardized for body size and composition. The rates of food consumption of the buffalo and cattle were significantly different when expressed per animal and expressed relative to metabolic body mass, with greater rates in the buffalo. When the influence of differing body compositions was removed, the rates of food consumption were not significantly different between species but approached significance. The species showed similar rates of mass gain but the cows of both buffalo and cattle had greater rates than the steers. The conversion efficiency of food to body mass was not statistically different between buffalo and cattle, but the composition of the respective increments may have differed, possibly by different proportions of protein and lipid. This is discussed with respect to the relative efficiencies of nitrogen conservation in buffalo and cattle. It is concluded that buffalo and cattle have different water physiology and broadly similar nutritional efficiencies. The performances of the two species in the monsoonal tropics differ for ecological reasons ensuing from different behavioural adaptations and water physiology.
The migration of sebum and suint components along wool fibres of Merino sheep
Authors: Hay JB , Mills SC
Published: November 2004

It has been shown that isotopically labelled sheep wool wax is carried passively along the wool fibre as a band by growth of the wool, and that it does not flow along the fibre to any large extent during experiments of several months. This supports the view that the function of sebum, in mammals in general, is to protect the hair (wool) fibre and the condition of the coat, and contrasts with the reported rapid spread of sebum over the human skin surface. It also seems unlikely that wax lost from the fleece during exposure to rainfall is replenished with sebum freshly secreted onto the surface, since sebum does not migrate. Two methods were used to obtain labelled wax, direct application of labelled cholesterol to the skin surface and intradermal injection of labelled sebum substrate. Prior washing of the wool with detergent showed that wax already on the fibre was not the cause of the observed lack of flow of newly formed wax. Isotopically labelled suint components were also carried passively by wool growth. It is unlikely that wax is transported to any extent by suint in the wool; this is in contrast to the suggested role of sweat in facilitating the spread of sebum over the human skin surface. Some spreading of radioactive wax and suint bands was noted however, possibly because of diffusion and mechanical disturbance of the wool.
Identification of the oestrogenic isoflavones in fresh and fermented berseem clover (Trifolium alexandrinum)
Authors: Shehata MN , Hassan A , El-Shazly K
Published: November 2004

A thin layer chromatography technique was used to identify and semiquantitate the oestrogenic isoflavones in berseem clover (Trifolium alexandrinum). Biochanin A and genistein were the most prominent isoflavones in all the three cuts of fresh berseem clover. Low concentrations of formononetin and daidzein were also detected. The concentrations of the all oestrogenic isoflavones gradually decreased in the successive cuts. Fermentation of all three fresh cuts in silo or in rumen fluid increased the concentrations of these isoflavones. Incubation of the silage materials with rumen fluid had little effect on the concentrations of the isoflavones. The concentrations of the oestrogenic isoflavones in fresh or fermented materials considered were too small to have any adverse effects on growth or reproduction of farm animals.
The effect of stage of maturity in sheep upon intake and digestion of roughage diets
Authors: Egan JK , Doyle PT
Published: November 2004

In two experiments, weaner (15-17 kg liveweight) and mature (40-45 kg) Merino wethers were fed ad libitum on three chopped hays of varying quality. Measurements were made of intake and digestion of organic matter (OM) and cell wall content (CWC), retention time of a digesta marker, and the particle size distribution of CWC recovered in the faeces. When offered subterranean clover hay (OM digestibility 70 %) the weaners consumed 19 % more OM (g/kg0.75) than did the mature wethers, but the digestibilities of OM and CWC were similar for each age group. Possible reasons for this variation in intake are discussed. Intake and digestion of OM and CWC were similar for both groups given the two poorer hay diets (OMD, 56 and 46 %), but several weaners could not be sustained for long periods on the poorer of the two diets. Implications for young sheep grazing dry pastures are discussed.
Manipulation of leaf area and its effect on grain yield in droughted wheat
Authors: Richards RA
Published: November 2004

Modification of crop leaf area could have considerable consequences on grain yield where soil water is limited. To test this, leaf area was artificially reduced to examine the effect on three wheat cultivars in two different drought situations-one where all the water was supplied just prior to sowing, and the other where half of the water was supplied before sowing and half after sowing on eight separate occasions. Leaf area was modified by detillering and two leaf-cutting treatments, Plants were grown individually in pots 1 m tall by 0.1 m diameter at a crop density of 100 plants/m2. Leaf area and water use were measured weekly for all plants, and at maturity the yields of grain, straw and leaves, and the yield components, were measured. The defoliation treatments reduced total cumulative leaf area by about one-half. This in turn reduced the rate of early water use and resulted in the highest grain yields and harvest indices. The ratio of leaf weight to total plant weight was inversely associated with yield both within and across treatments, suggesting an excessive investment in leaves. This was also indicated in an adjacent experiment where the same cultivars, watered daily, had a similar leaf weight to that of the droughted plants, yet yielded considerably more grain. Water use efficiency (the ratio of above-ground dry weight to total water used) also had a significant influence on grain yield. These results suggest that it may be worth while modifying leaf area development in wheat genetically to improve yields under some dryland conditions.
A model of the survival of larvae of the cattle tick, Boophilus microplus, on pasture
Authors: Utech KBW , Sutherst RW , Dallwitz MJ , Wharton RH , Maywald GF , Sutherland ID
Published: November 2004

Larvae of Boophilus microplus were released onto pasture in south-eastern and central Queensland and their survival was measured using destructive sampling. In summer 50% of the larvae survived for 2 weeks and 10% survived for 4 weeks. Comparable values for winter were 3-4 and 6-11 weeks respectively. A chart was prepared to relate larval survival to maximum temperatures in summer, when pasture spelling for tick control is most likely to be successful. A computer simulation model was developed to describe the survival of the larvae in relation to meteorological conditions. The parameter values were fitted using the data from south-eastern Queensland and tested against observations made in central Queensland. Maximum temperature and saturation deficit at 1500 hours proved to be the best predictors of survival, but it was not possible to distinguish between their effects.