School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemEffects of adding nutrients on soil chemistry and tree growth in native Eucalyptus forests of south-eastern Australia( 2007)The decreasing area available for timber extraction in south-eastern Australia, due largely to social pressure to reserve greater areas of forest, has led to the consideration of fertiliser-application to increase wood output from the remaining available forest. Potentially deleterious effects of fertilising on water quality must be assessed before implementation on a wide scale. This is in accordance with relevant forest management policies. This study examined the effects of applying fertilisers containing nitrogen and phosphorus, on soil and soil-water chemistry in two pole-sized stands of mixed Eucalyptus spp in the Wombat Forest, in the Midlands Forest Management Area, Victoria, Australia. The findings are synthesised and discussed in relation to management of regenerating mixed-eucalypt forests in south-eastern Australia. Fertiliser treatments were none (R); 400 kg N ha-1 as ammonium-sulphate (N); or 400 kg ha-1 plus 202 kg P ha-1 as triple superphosphate coated with 10% sulphur (NP). It was calculated that incidental additions of S were 1371 kg ha -1 (N treatments), and 1696 kg ha-1 (NP treatments). It was expected that P would be principally adsorbed on soil surfaces; N immobilised in the soil organic pool and that metallic cations would enter the soil solution to varying degrees. Fertiliser-addition increased both plot-basal-area (BA) growth and the rate of stand self-thinning. In 3.8 years, BA in reference (R) plots at two sites increased by 7.3% and 23.4%. Where N alone was added, BA increased by 14.2% and 27.1%, while in NP plots BA increased by 17.1% and 42.7% respectively. Mortality was 9% in untreated plots compared to 14% in NP plots. Estimated increases in biomass growth equated to additional above-ground nutrient accumulation of 0.4 to 1.5 kg ha-1 of P, and 5.5 to 20.8 kg ha-1 of N. This represented only 0.2 to 0.7% of added P, and 1.4 to 5.2% of added N. Soil solution was extracted from 10 and 50 cm with porous-ceramic-cup tension-lysimeters (-0.6 kPa). Concentrations of P and N were low both before and after adding fertiliser. Across all treatments the maximum median PO43- concentration in soil-water at 50 cm was 0.12 ppm (mean 0.28 ppm). Typically PO43- concentrations were not higher than 0.03 ppm. The 400 kg ha-1 of added N was rapidly immobilised in the soil organic pool. The greatest mean NH4' concentration from a single sampling occasion was 1.1 ppm. The mean NO3 concentration at 50 cm was never higher than 0.26 ppm. After adding N in fertiliser the proportion of NO3- relative to NH4* in soil-water increased and was correlated with decreasing soil-water pH. Less than 1% of added P and N was recovered from soil solution at 50 cm. The largest pool of added P recovered was PO43- adsorbed to soil between 0 and 20 cm, due to the soil adsorption capacity being well in excess of the applied 202 kg P ha-1. Phosphate desorption using sequential extractions with a mild acid extractant (0.3M NH4F, 0.1M HCI) recovered between 25% and 116% of added P. Differences were attributed to both the amount of P added and the effect of time since treatment at different sites. Soil disturbance during sampler installation was found to be more likely to raise soil-water P concentrations at 50 cm than would adding up to 202 kg P ha-1. Among the ions in solution. SO42- and CI' were the dominant anions while Cat+ dominated the cation chemistry. In untreated forest 5042- in soil-water ranged from 7.7 to 16.0 ppm at 10 cm and 7.9 to 12.2 ppm at 50 cm. In fertilised plots up to 100.5 ppm SO42 was measured in soil-water at 50 cm depth. In the N treatment at 50 cm, SO42- in soil-water accounted for 9.4 % of applied S. compared to 14.0 % in NP. In untreated forest, soil-water Cl- and SO42- accounted for over 98% of the total soil-water anions, in roughly equal proportions at 10 cm, and CI- slightly higher at 50 cm. Following fertiliser-application soil-water pH at 10 cm fell from 6.3 in R to as low as 4.81 (N) and 4.45 (NP). At 50 cm pH never dropped below 6 and there were no visible departures from reference concentrations. Relative activities of K+ and Mg2+ in solution increased with decreasing pH, indicating increased leaching potential. Sulphate in soil-water increased total anion charge further in NP than in N. Total charge (cmolc L-1) for cations followed anions. A slight deficit in anion charge was likely due to the unquantified contribution of organic anions. These results confirm that despite the quantity of fertilisers added in this trial being double likely operational quantities, the forest and associated soils had the capacity to retain these nutrients through a variety of processes. The study validates the environmental sustainability of proposed intensive management practices including fertiliser-application in this forest type. It also emphasises the importance of understanding fundamental forest nutrient cycling processes when aiming to carry out intensive forest management practices in an environmentally sensitive manner.
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ItemA study of weight-loss and compensatory gain in sheep( 1971)Two experiments of similar nature were conducted. In the first experiment 49 Corriedale wethers at approximately 8 months of age were allocated to four experimental groups and, within groups, to various slaughter weights which were spaced at 5 kg intervals. Group I animals were fed ad libitum and slaughtered - over a body weight- range of 38 - 63 kg inclusive. Groups II and III animals were fed ad libitum until 48 kg body weight hereupon intake was restricted to achieve a body weight loss of 0.9 kg/week until body weights were reduced to 38.5 kg and 34.5 kg, respectively. Ad libitum feeding was then resumed and animals were slaughtered up to 63 kg body weight at the same weight intervals as in Group I. Group IV animals were fed ad libitum until 48 kg body weight and then, food was adjusted to maintain body weight at 48 kg. Four animals were slaughtered after 60 days and a further four after 120 days of maintenance of body weight. In the second experiment, 15 wethers of similar age, breed and nutritional history as those used in Experiment 1, were allocated to four slaughter groups in a treatment similar to that of Group III in Experiment 1. Four animals were slaughtered at 33 kg body weight at the beginning of the first period of ad libitum feeding; three animals slaughtered at 45.5 kg at the end of the first period of ad libitum feeding; three animals slaughtered at 33.5 kg at the end of the weight loss phase; and five animals slaughtered at 46.5 kg at the end of the second period of ad libitum feeding. The compensatory growth rates of animals in Groups II and III were greater than those of Group I in each of the successive 5.5 kg increments in body weight. By maintaining higher growth rates over the entire weight range, the largest animals of Groups I I and III were slaughtered at a similar age to those, of Group I. Similarly, in Experiment 2, the compensatory growth rates (Group VI) were greater than continuous growth rates (Group V) over the body weight range used in this experiment. The data was transformed to logarithms in order to use Huxley's (1932) allometric growth equation in the linear form for an analysis of covariance. During continuous growth (Groups I and V), the empty body weight (EBW) increased as a proportion of full body weight (FEW) whilst during the compensatory growth which followed weight loss (Groups II, III and VI) the proportion of EBW remained constant. At the same FEW the EBW of Groups I I and III was less than that of Group I. Similarly, the EBW of animals maintained at a constant body weight (Group IV) was less, at the same FBW, than that of Group I. Carcass weight (CW) increased as a proportion of EBW as EBW increased in Groups I and V but the proportion remained constant in Groups II, III and VI. At the geometric mean FEW, treatment did not affect CW. However, the apparent dressing percentage (CW / FBW x 100) was 2% less during compensatory growth compared with that during continuous growth. The carcass length of animals in Groups II, III and IV was greater than that of animals in Group I.
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ItemGrowth, body composition and related studies of farm animals( 1975)The publications included in this thesis report experiments done while the candidate has been a member of staff at the University of Melbourne (1957-1975) . The thesis is divided in five sections, as follows:- (Paper Nos.) Growth and development of farm animals 1-20. Physical studies of the alimentary tract of dairy cattle 21-24. Investigations of the skin of cattle 25-27. Animal behaviour 28-29. Miscellaneous papers on animal production 30-33. The section entitled "Growth and Development of Farm Animals" begins with a review (Paper No. 1) of the results of some of the papers in this section. It is followed by two papers (2, 3) which re-analyse the data of other authors and present hypotheses which are later developed and tested (in papers 4 to 20) . Papers numbered 4, 7, 25, 26, 27, 28, 29 were presented as part of the candidate's Ph.D. thesis. They are included, not for examination, but because they are related to other work in this thesis. Papers numbered 2, 3, 5 are related to material in the same Ph.D. thesis. In all papers where authorship is shared, the joint authors were either scientific colleagues, research assistants or graduate students. In all cases, the candidate made a contribution in the collection of the data, and was responsible for the design of the experiments. He was also responsible for the supervision of the work and played a major role in preparing it for publication. Where the candidate's name appears either as sole author or as senior author, he was directly responsible for and involved in all aspects of each experiment.
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ItemPredicting the grain protein concentration of wheat from non-destructive measurements of the crop at anthesis( 2005)Grain protein concentration is an important specification for wheat, which determines the quality grade and price received by growers. It is difficult to achieve target grain protein concentration in semi-arid southern Australia, because of the low and variable rainfall. Growers may benefit from being able to predict grain protein concentration before harvest, especially where there is a threshold or `window' requirement for a particular grade. Grain outside specifications could be forward sold into other grades while prices were good. Spatial predictions of grain protein concentration would allow the pattern of harvest to be managed to optimise profit. This thesis proposed a method for predicting grain protein concentration from non-destructive measurements of the crop (spikes, spikelets) at or after anthesis. The theoretical propositions underlying the method were then evaluated using data from nitrogen fertiliser experiments, data from the literature, and a simulation exercise. The proposed method was to estimate grain number from spike or spikelet number. Variance in grain number, together with the diminishing returns response of grain number to nitrogen, would then be used. to estimate maximum grain number. Maximum grain number would be linked to a unique `critical' grain protein concentration, from which grain protein concentration at other grain numbers could be estimated. Spike and spikelet number were counted throughout grain-filling in nitrogen fertiliser experiments to determine the importance of time of counting. The time of counting was important for absolute, but not relative spike and spikelet numbers: Spike and spikelet number varied, throughout grain-filling, but interactions with nitrogen treatments were rare. Inclusion of spikelets in counting was based on glume length, which interacted with time of counting. Spike death was frequently observed and occurred in proportion to post-anthesis growth, at 0.187(±0.018) spikes/g. The rate with respect to grain yield was similar, at 0.190(±0.038) spikes/g. An analysis of mass/number relationships between grain, spike and spikelet number, and crop and spike biomass at anthesis, showed that grain number was better related to spike biomass, and that spike and particularly spikelet number, were better related to crop biomass. Spikelet number changed at .a rate of between 6.6 and 9.3 spikelets/g biomass across 'a range of experiments; spike number changed at a rate between 0.14 and 0.62 spikes/g. The interrelationships showed grain number should be related to spikelets/spike, and proportion of crop biomass in the spike. The relationships, however, only existed in some experiments and were not universal. An alternative suggested by the analysis was use of spike number as a direct proxy for grain number (ie. assuming constant grains per spike). Spike number was tested as a proxy for grain number initially by analysing the components of variance of grain number across nitrogen, rotation and plant density experiments. Spike number was the main component of variance in grain number (59.8- 71.0% of log(variance)) in nitrogen experiments, with no significant covariance between spike number and grains per spike. Grains per spike and covariance were much greater components of variance in plant density experiments, and grains per spike and spike number were equal sources of variance in rotation experiments, with small positive covariance. Spike number would be an unbiased, but not perfect proxy for grain number when nitrogen was the main factor varying, but not for factors related to rotation or plant density. Spike number and crop biomass at anthesis were compared as estimators of grain number in nitrogen experiments, in an analysis of the nature of the responses to nitrogen fertiliser. Grain number as an estimator of grain yield was included in the analysis to understand the likely effect of using grain number rather than yield as a predictor of grain protein concentration. Crop biomass at anthesis, spike number and grain number all reached maxima at similar nitrogen fertiliser rates, but crop biomass at anthesis was a more precise estimator for the maximum rate required for grain number (RMSE of nitrogen for maximum, 2.4 kg N/ha vs. 26.4 kg N/ha). Grain number had a maximum consistently higher (+32.6±8.0 kg N/ha) than the maximum for yield. Once nitrogen fertiliser rates were corrected for the different maxima, grain number and yield had identical relative response rates to nitrogen. The response rates of crop biomass at anthesis and spike number were both related to the response rate of grain number by a power relationship with exponent 0.6. The lack of methods for anticipating phase differences caused by late nitrogen application and pre-anthesis water deficit will prevent exploitation of these relationships in all environments. The estimation of maximum spike number from its variance was simulated across the width of an air-seeder, using consistent variations in nitrogen fertiliser rate between tynes to drive variance in spike number. Nitrogen fertiliser was normally distributed. It was possible to extrapolate the variance/spike number relationship to estimate the maximum only where the slope of the relationship was negative. Slopes close to zero caused errors. of fitting, where the `signal' from the relationship was indistinguishable from the `noise' in estimating variance. This coincided with low (below 0.8) relative spike numbers and led to over-estimation of low relative spike numbers. Low spike number because of sub- or supra-optimal nitrogen could be distinguished by the second derivative of the fitted function, which was positive for supra-optimal nitrogen. There was no unique `critical' grain protein concentration (for maximum yield or grain number) in southeastern Australia, but there was a consistent relationship between `critical' grain protein concentration and grain weight. The relationship in terms of grain nitrogen content was a linear function of grain weight. The parameters also varied with genotype, and signed relative grain number, calculated as GRS=1-G/GMax for supraoptimal nitrogen, and GRS=G/GMax-1 for sub-optimal nitrogen, where G is grain number. The best estimation of grain nitrogen across genotypes was: Grain N (mg N/grain) = 0.317 + 1.00 x GRS + (0.0115 -0.0181 x GRS) x W, where W is grain weight in mg/grain. The root mean squared error of grain protein concentration estimated from this function was 0.91%. Grain weight would need to be estimated to estimate grain protein concentration. Errors due to grain weight had more effect at higher GRS, and at lower grain weight. The conclusion was that grain protein concentration may be predicted using crop biomass or spike number as a proxy for grain number. Predictions would be best in the absence of pre-anthesis water deficit or nitrogen applied after Zadoks 32. The predictions would be best for relative grain number greater than 0.8 at sub-optimal nitrogen, and for any relative grain number at supra-optimal nitrogen. A confidence interval could still be provided for grain protein concentration at lower relative grain numbers with sub-optimal nitrogen. Predictions would be most accurate if grain weight was reliably above 35 mg/grain.
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ItemA molecular genetic study of seed dormancy in aegilops tauschii and expression of sprouting resistance in common hexploid wheat( 2004)The wild wheat relative Aegilops tauschii, has been identified as a useful source of preharvest sprouting (PHS) resistance for hexaploid bread wheat. Seed dormancy, a major contributor to PHS resistance, was shown to be partly expressed in hexaploid wheat derived from direct hybridisation between Triticum aestivum and Ae. tauschii. The enhanced seed dormancy possessed by the Ae. tauschii derived direct-cross wheat lines was manifested by embryo and seedcoat related mechanisms. The embryo related mechanism could not confer full expression of dormancy without the presence of seedcoat related factors, suggesting that the two mechanisms may be independently inherited. The presence of seedcoat related dormancy however, was not associated with the red seedcoat phenotype, which has traditionally been associated with PHS resistance in wheat. Red pigmentation of the seedcoat is likely to be "involved in the extreme dormancy possessed by Ae. tauschii but does not preclude partial expression within a white seedcoat background. The ability of Ae. tauschii derived wheat lines to enhance seed dormancy may have potential economic benefit to breeding for PHS resistance in white wheat varieties. Presently, white wheat varieties grown in the sprouting susceptible regions of Australia possess inadequate protection, costing the industry up to $100M annually. Inheritance of seed dormancy in Ae. tauschii was found to be controlled by one or two major genes which were influenced by minor genes and/or environmental factors. These results are consistent with the findings of several previous reports. Inheritance was shown to be dominant at the F3 grain generation, consistent with the generally dominant nature of dormancy possessed by red seeded genotypes. However, preliminary assessment of individual F2 seeds indicated recessive control of dormancy. Because genes possessed by the maternal tissues of the seedcoat do not segregate until the F3 seed generation, the F2 recessive model may be indicative of separate genetic control for the embryo related dormancy mechanism(s). Based on the above inheritance information, a bulked segregant analysis approach was initially undertaken for the development of linked molecular markers for seed dormancy. One microsatellite marker on chromosome 1D produced polymorphism between resistant and susceptible DNA bulks. A mapping approach was subsequently undertaken, revealing two significant QTL mapping to chromosome 1D. The putative QTL for seed dormancy will relate to the embryo component of dormancy, as the trait data employed related to the F2 seed generation, which was segregating for embryo related genes. The D genome of hexaploid wheat presently possesses the fewest QTL for PHS resistance of the three contributing genomes. Within the D genome, chromosome 1D was poorly represented in the literature. As such, 4e. tauschii represents a potential to bolster numbers of QTL for sprouting resistance in hexaploid wheat. Given the homology between the D genomes of Ae. tauschii and T aestivum, the microsatellite markers identified, flanking the putative QTL, will likely be transferable to hexaploid bread wheat. Seed dormancy is strongly influenced by conditions during growth. As such, unambiguous selection through use of molecular markers will expedite the introgression of this economically important trait into elite wheat cultivars.
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ItemGrowth rate and body composition of cattle( 1971)A study has been made of the effect on body composition of growing Angus steers at three different rates. On reaching a live weight of 300 kg, animals were allocated to three treatments, viz; (i) a high growth rate (H):- 0.8kg/day (ii) a low growth rate (L):- 0.4kg/day (iii) a high growth rate 0.8kg/day followed by a period during which live weight was maintained constant (HM). The animals in each group were individually penned and the different growth rates were achieved by controlling intakes of a pelleted concentrate feed. Two animals were killed at 300 kg and the remaining 27 animals (nine in each treatment) were killed at common live weights of 330, 363, 400 and 440 kg. Analyses of the data by covariance were made using the logarithmic transformation of the allometric equation y = axb. At the same full body weight (FBW), HM animals had a greater empty body weight (EBW) than L animals, but the differences between H animals and the other groups were not significant. At the same FBW, hot carcass weight (HCW) was greater in the HM group than in both the H and L groups. As a proportion of.EBW, HCW was greater in both the HM and L groups than in the H group, indicating a greater offal component of EBW in the H animals. The loss in weight of the dressed carcass during storage at 2C for 24 hours was similar in all three groups and amounted to 0.98% of HCW. The proportion of HCW in the fore- and hind-quarter was similar in each group. The composite weight of the lungs, trachea, heart and skirt muscle (LTHS) was unaffected by the different growth rates. Liver weight, however, was lower in both the HM and L groups than in the H group. Moreover, the difference in liver weight between the H and L groups increased as liveweight at slaughter increased. Maintenance of live weight in the HM animals caused a reduction in the weight of the kidneys while the low growth rate of L animals was associated with an enhanced growth of the spleen. The weight of the pancreas was similar in the H and L groups while, at the heaviest live weight (440 kg), there was an apparent loss of pancreas tissue during the maintenance period in the HM group. The combined weight of the head, feet and tail (HFT) was greater in the animals from both the HM and L groups than in the H group. This was a reflection of the older age of the HM and L animals at slaughter. Hide weight was similar in both the H and L groups while the weight of the hide in the HM animals showed a differential effect of live weight compared to the H treatment. At the lowest killing weight (330 kg), the hide showed an apparent loss in weight. during the maintenance period while at the highest killing weight (440 kg) it showed an increase in weight. These differences in hide weight may have been related to seasonal effects on cattle coats and on skin thickness.
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ItemAn analysis of the problems of estimating the thyroid hormone level in the blood of domestic animals, and the effects of varying that level on the marketable products of such animals( 1957)In the field of animal husbandry it is becoming increasingly apparent that maximum efficiency of production cannot be attained without careful attention to the health of the animal, and to the balance between the animal and both the internal and external environments. For example, if artificial methods are used to increase production of milk without at the same time increasing, the feed intake the result is generally a decline in the health of the cow which may eventually lead to serious illness. Much recent research in this field has been concerned with the function and activities of specific organs rather than with the body as a whole, showing; that the factors involved in production are much more numerous and varied than was originally thought. Examples of this type of research are the intensive investigations at present being conducted into rumen activity and microflora, wool fibre growth, mammary gland function, reproductive activity and the role of various endocrine glands in production. Of the endocrine glands, apart from those directly concerned in reproduction, the one most studied has been the thyroid which has been shown to play an important part in practically all spheres of animal production so far investigated. It was the aim of this experiment to establish a method for determining thyroid activity which would then allow us to investigate the relationship between this activity and various body processes in the normal animal. In the normally functioning animal the thyroid serves chiefly as a homeostatic mechanism maintaining the body functions at a steady level of activity and, to a certain extent, controlling the response of the body to changes in the external environment. Its effects are more apparent when the thyroid activity is altered in any of the many ways to be considered later. The lowering of the thyroid hormone output produces an animal with typical symptoms - low Basal Metabolic Rate, low body temperature, low reproductive capacity, decreased growth and development in young animals, increased fat deposition, sluggishness, drying and thickening of the skin and falling hair. On the other hand the hyperthyroid animal shows an. increased Basal Metabolic Rate, high body temperature, leanness, restlessness and, in some cases, protruding eyes. These facts have recently been put to practical agricultural use. Raising the thyroid output leads to a significant increase in growth rate, milk yield and egg production. Lowering; the level has proved a successful method of fattening pigs and fowls for meat production. These aspects are dealt with in the review of literature.