School of Agriculture, Food and Ecosystem Sciences - Theses
Permanent URI for this collection
Search Results
1 - 10 of 21
-
Item
-
Item
-
ItemControl of vegetative vigour of peach orchards( 1996)In the Goulburn/Murray Valley of South-Eastern Australia, orchard management aims to maximise productivity and ensure sustainability. Achievement of this objective relies on the control of excess vegetative vigour, minimisation of salinity and waterlogging damage and improvement of irrigation efficiency. The overall aim of this study was to identify the major controls over vegetative vigour under varying environmental conditions with a view to providing practical management strategies. Options which are currently available for control of vegetative vigour include dwarfing rootstocks, chemical growth regulators and summer pruning. Alternative systems which may be more suitable are Regulated Deficit Irrigation (RDI), saline irrigation and Restricted Root Volume (RRV). Regulated Deficit Irrigation (RDI) applied in a high-density peach orchard controlled vegetative growth (reduction of 50%) and maintained yield. RDI trees used less water than traditionally irrigated trees during the RDI period. This was attributed to reduced water availability and plant water status. Differences in water use continued after RDI due to a combination of tree size, leaf area and micro-advection. Irrigation with water of EC greater than 0.5 dS m-1 combined with RDI, reduced vegetative and fruit growth, yield and tree water use. Yield declined as a consequence of smaller leaf area, decreased photosynthetic activity and overall poor tree health. The adverse effects were largely attributed to chloride toxicity with leaf CI concentration approaching 3% dry matter. In a saline environment, RDI will require the inclusion of strategic leaching. A shallow non-saline water table combined with RDI initially enhanced vegetative growth. However, in the second season, adverse effects of both non-saline and saline water tables on tree growth and productivity were demonstrated. Tree water use was initially greater over the non-saline water table which contributed approximately 28% of total water used. Chloride concentrated in the leaves and fruit, while Na concentrated in the bark, butt wood and structural roots. These results demonstrate the need for both leaching of the soil and limiting drainage to the water table. Artificial drainage and/or accurate irrigation scheduling will be essential features of successful management. Restricted root volume (RRV) reduced tree growth although the effect decreased in the third and fourth seasons. Water stress (RDI) had little effect on tree growth despite considerable differences in plant water status. Trees in the smallest soil volume demonstrated difficulty in achieving adequate fruit size. There were significant differences in water use in response to soil volume and RDI management. Water use followed similar seasonal patterns as previously established. In summary, RDI is a viable management option for the control of vegetative growth in high density peach orchards and RRV is effective in controlling vegetative growth. More research is required, however, before RRV can be adopted by growers. Saline irrigation reduced vegetative growth and also productivity and is therefore not considered an option for control of vegetative vigour. Salinity and water tables should be managed to minimise their effect.
-
ItemThe use of raw soybean as a means of biological control of Eimeria acervulina infection in broiler chickens( 1996)Avian coccidiosis has long been recognised as a disease of major consequence in the poultry industry. It occurs world-wide and causes major losses in the industry. It is caused by a protozoon belonging to genus Eimeria. Many studies have been conducted to investigate means to control this disease. Nutrition has been established to have an impact on the severity of the disease and the disease affects nutrient absorption and utilisation. One phase in the life cycle of the parasitic agent is dependent on digestive proteases and this was the basis in developing the hypothesis of this study. Raw soybean, which contains protease inhibitors, was investigated as an inhibitor of the protease required by the coccidia in the excystation process of its oocyst. In this study, different levels of raw soybean inclusion in the diet of broiler chickens infected with Eimeria acervulina were utilised to substitute for the processed soybean meal in the rations as a main protein source for the birds. Two hundred and fifty two day old male broiler chicks were maintained under uniform management throughout the experiment. They were exposed to two different E. acervulina inoculation levels (100,000 and 300,000 oocysts) at 17 days of age. Three dietary treatments providing raw soybean inclusion of 7, 14 and 21% of the total diet, were compared with a commercial coccidiostat-free diet. The results of this experiment demonstrated that raw soybean can reduce the severity of the coccidia infection, as evidenced by reduced intestinal lesions in the birds given raw soybean inclusion compared with the commercial diet groups. The number of oocysts produced, as measured in the droppings, was also substantially lower in the former groups. The live weight gain of those birds given raw soybean was also higher than that of the birds given the commercial diet. In addition, there was no reduced feed conversion ratio or difference in digesta viscosity observed among treatment groups. However, the pancreas of the birds provided with raw soybean diets was enlarged when compared to that of birds fed the commercial diet. These results indicate that there was a physiological response to the raw soybean diet, as evidenced by the positive effect of the soybean inclusion in reducing the severity of the coccidia infection, and this beneficial effect offset any adverse nutritional effects. Further studies are required to provide a strategic basis for use of natural dietary protease inhibitors during a period of development of tolerance or resistance to coccidial infestation. These might include studies on the alternative age of the chickens when given the natural inhibitors and the optimum concentration of the raw soybean at which it produces no adverse effect whilst reducing the severity of coccidiosis.
-
ItemThe influence of concentrations of dietary lysine and energy offered during lactation on the lactation and subsequent reproductive performance of the first-litter sow( 1996)The first-litter sow has lower lactation and subsequent reproductive performance than older parity animals. The experimental work in this thesis was conducted to elucidate the influence of dietary energy and protein concentration during lactation on the lactation and subsequent reproductive performance of first-litter sows, whose litters were weaned at 3-4 weeks of age. In the first experiment, 140 first-litter sows were offered one of five diets, ranging in lysine content from 6.2 to 15.1 g/kg. Voluntary feed intake and sow liveweight loss were unaffected by dietary lysine concentration. However sow backfat loss was lowest for sows offered the lowest lysine diet and tended to plateau at a dietary lysine level of 10.6 g/kg. Piglet preweaning growth responded in a curvilinear manner to increasing lysine concentration. The results also indicated for sows nursing 9 or more piglets, that weaning to mating interval decreased with increasing sow dietary lysine concentration. Subsequent litter size was significantly higher for sows offered the two higher lysine diets during lactation, compared to the two lower lysine diets (10.7 vs 9.6 born alive, P<.05; s.e.d. 0.5). In the second experiment, 175 first-litter sows were offered one of five diets with a similar lysine:digestible energy (DE) ratio (0.88 to 0.85 g/MJ) but ranging in DE content from 12.6 to 15.1 MJ/kg. Voluntary food intake and piglet growth rate during lactation were unaffected by DE content of the diets. Sow liveweight loss during lactation declined with increasing energy content up to 13.8 MJ DE/kg. Backfat loss during lactation tended to be highest for sows offered the diet of lowest DE content and declined with increasing energy content up to 15.1 MJ DE/kg. The subsequent weaning to remating interval and litter size were unaffected by dietary DE content. In the third experiment, 204 first-litter sows were offered diets containing either 8.1 or 13.3 g lysine/kg during lactation. Voluntary food intake in lactation, piglet preweaning growth, sow liveweight and backfat loss during lactation, weaning to mating interval and subsequent litter size, were unaffected by dietary lysine concentration of the lactation diet. The number of corpora lutea and embryos were also not influenced by dietary lysine concentration during the preceding lactation. However, the data from those sows whose preweaning litter growth was in excess of 40 kg demonstrated a significant improvement in number of corpora lutea at the higher dietary lysine level. The results indicate that sow liveweight and fat losses during lactation appear to be more responsive to changes in DE concentration than changes in dietary lysine level. However, lysine concentration may limit piglet growth rate, weaning to mating interval and subsequent litter size. The results also suggest that improvements in subsequent litter size, observed when sows are offered high dietary lysine levels during lactation, may be due to an improvement in ovulation rate. These experiments suggest that current amino acid recommendations for lactating first-litter sows are inappropriate and may be constraining both milk production and subsequent reproductive performance.
-
ItemGenetic improvement in beef cattle : and developing breeding programs for Dookie Agricultural College and for Turkey( 1996)This thesis analyzed performance records for Polled Hereford beef cattle collected over 34 years from Dookie Agricultural College. It uses two sources of information for size traits for the animals: accumulated raw data and BREEDPLAN's Estimated Breeding Values (EBVs). Comparisons were made between the two sets of data. As expected growth rate and size traits are differed between sexes, males were the highest, females were the smallest and steers were in between. Phenotypic correlations among size traits were moderate to high. EBV traits showed very high `genetic' correlations among size traits, but negative genetic correlations with 200-d. Wt Milk EBV. Sires' own EBVs were highly correlated with progeny group mean EBVs. The relationship with progeny adjusted phenotypic means were lower. Heritability values for phenotypic adjusted weights were for sire progeny groups; for Birth Weight (BtWt) female 0.30, male 0.38, for 200-d Wt female 0.42 and male 0.47, and for 400-d Wt female 0.28 and male 0.19; and for dam progeny groups, for BtWt, female 0.78, male 0.59, for 200-d Wt females 1.48 and male 1.66, for 400-d Wt female 1.06 and male 0.32. These values indicate that dams exert a non-genetic maternal effect particularly for 200-d Wt. Although the heritabilities for EBV traits were expected to be 1.00, (estimated from the `genetic' differences between the animals), except for BtWt and 200-d Wt Growth EBV for females, this study's estimates were much higher than 1.00. This suggests that the process of estimating breeding values has been unreliable for evaluating the animals of this herd for 200-d Milk, 200-d Wt Growth for males, 400-d and 600-d growth. The analysis results and supporting literature were used to develop breeding programs for Dookie and for Turkey. Areas of further research are suggested in the. conclusion.
-
ItemProduction of heavy weight cryptorchid and wether lambs( 1996)Declining Iamb consumption remains a major problem facing the Australian prime Iamb industry. For Iamb to retain its market share and to remain a viable commodity in the future, leaner Iambs must be produced and marketed. Recent industry initiatives therefore focussed upon the production and marketing of Iambs to meet carcass specifications of 18-26 kg with a fat depth of 6 to 15 mm at the GR site. Emphasis was placed upon the production of lean carcasses weighing more than 22 kg, which are otherwise referred to as Elite Iambs. The development of production, management and marketing systems to produce and market Iamb carcasses of Elite Iamb specifications, both domestically and overseas, was the focus of this research program. The major objective of this experiment was to determine the potential of producing high and consistent quality meat from cryptorchid and wether Iambs meeting carcass specifications for Elite Iambs when slaughtered from six to eighteen months of age. One hundred and sixty three second cross Poll Dorset x Border Leicester/Merino cryptorchid and wether Iambs, born in May 1991 at Rutherglen Research Institute, Rutherglen, were grown and managed on annual pasture at an average liveweight of 50 kg prior to slaughter. Lambs were allocated to one of seven slaughter groups and finished every two months from 6 to 18 months of age and the influence of sex, age and nutrition on carcass composition, meat quality attributes and fat quality and consistency of cryptorchid and wether Iambs examined. Cryptorchid and wether Iambs slaughtered from 8 to 18 months of age produced carcasses meeting targeted specifications of greater than 22 kg with 6-15 mm of fat at the GR site. Lambs slaughtered at six months of age did not achieve the target liveweight of 50 kg at slaughter due to poor seasonal conditions which influenced the quality and availability of annual pasture in spring 1991. Cryptorchid Iambs had a lower dressing percentage and produced carcasses with a lower GR measurement than wethers at a cold carcass weight (CCW) of 23.5 kg. Cryptorchid Iambs exhibited growth rate advantages over wethers only when nutrition and seasonal conditions did not limit Iamb growth. When compared at the same fasted liveweight, cryptorchid Iambs deposited less internal fat than wethers. Cryptorchid carcasses also had a lower proportion of subcutaneous fat present on all primals, higher proportions of soft tissue and bone in the hindquarter and the EMA of the M. longissimus thoracis was significantly larger compared with wethers at a CCW of 23.5 kg. The proportion of CCW in the leg, chump and ribloin was not significantly influenced by Iamb sex. Nutritional management of lambs significantly influenced the proportion of subcutaneous fat on all primals. Meat quality was significantly influenced by Iamb sex however results obtained did not suggest that meat from cryptorchid Iamb carcasses was of inferior quality compared with wethers as only small differences in tenderness, intramuscular soluble collagen content, meat flavour, meat colour, intramuscular fat content and cooking loss were found. In addition, age and nutrition significantly influenced meat quality, however, consistent relationships were not found. The incidence of yellow soft subcutaneous fat was higher in cryptorchid Iamb carcasses than those from wethers with cryptorchids also producing subcutaneous fat with significantly higher levels of total unsaturated fatty acids and lower levels of stearic, palmitic and total saturated fatty acids compared with wethers. Age and nutrition also influenced the fatty acid composition of subcutaneous fat with Iambs fed lupins having significantly higher linoleic acid levels in subcutaneous fat. However, the magnitude of these differences did not explain differences found in fat quality and consistency between cryptorchid and wether carcasses slaughtered at different ages. Significant, though small, differences were found due to sex in both the triglyceride and phospholipid components of intramuscular fat. As higher levels of polyunsaturated fatty acids were found in the phospholipid component of intramuscular fat compared with cryptorchids, this may affect the keeping quality of meat from wether carcasses. Finally, although significant differences due to age were found in the fatty acid composition of intramuscular fat, these differences were not consistent with age and more likely reflected differences in nutritional management between slaughter groups. This study demonstrated that cryptorchid and wether Iambs turned off at heavy market weights on an improved plane of nutrition over a 12 month period produced carcasses meeting Elite Iamb specifications and yielded high quality, tender meat.
-
ItemThe impact of animal manures on the behaviour of sclerotia producing fungi infecting cotton( 1996)An investigation to determine the role of the addition of animal manure into soil on germination of sclerotia of fungi infecting cotton, including Sclerotium rolfsii, Sclerotinia sclerotiorum, Rhizoctonia solani, and Macrophomina phaseolina was conducted at the laboratory of Plant Science of Faculty of Agriculture, Forestry and Horticulture, University of Melbourne. Its effects on growth of cotton seedlings and disease severity caused by S. rolfsii was observed in a growth chamber conditions. Different source of manures affects pathogen behaviour differently. Chicken manure restrict the activity of S. rolfsii and Sc. sclerotiorum by enlarging populations of actinomycetes and bacteria in soils. When sderotia of S. rolfsii were placed on chicken manure-soil mixture, their germination was inhibited. Furthermore, hyphal lysis occurred 14 days after emerging. This manure also decreases the survival of sclerotia of S. rolfsii and Sc. sclerotiorum when the sderotia were buried for 2-3 months in it. Hence, the manure was able to reduce the severity of seedlings disease caused by S. rolfsii. Chicken manure provides a high nutrition for cotton growth when the seeds were sowed at least two months after incorporating. When cotton seeds were sowed in this mixtures soon after incorporated, however, the seedlings were suffered from severe phytotoxicity namely chlorosis and stunting. When seeds were sowed two months after incorporating of chicken manure into soil, there was none of phytotoxicity symptoms appeared. The growth of the seedlings was much better than that in soil. Cow manure, on the other hand, stimulated germination and growth of emerging hyphae of S. rolfsii in the short term of the experiment and increased disease severity. An abundance of readily available nutrients from this manure overcomes the inhibition of sclerotium germination caused by competition and provides nutrients for growth. These results indicate that chicken manure offers a good prospect to improve cotton growth as well as to control cotton seedling disease caused by S. rolfsii and probably other cotton pathogens. This could therefore be incorporated into soil as pre-sowing treatments. The best result is achieved when cotton seed was planted in this media at least two months after incorporating. By this time, some toxic substances which may be exist have degraded and sclerotia of S. rolfsii have disappeared as well.
-
Item
-
ItemFixation mechanisms of copper chrome arsenate (CCA) wood preservative( 1996)The fixation mechanism of copper chrome arsenate wood preservative is investigated. Parameters examined, include: pressure, solution temperature, solution strength, second stage treatment with water and oil, initial vacuum and timber pack design. The influence of these parameters is determined by analysing; basic density, penetration, preservative retention and leaching characteristics. Legislative leachate levels are also investigated. The timber used in the trials is kiln dried, structural grade F5 heartwood and sapwood of Pinus radiata D. Don. Radiata pine roundwood is also used. Two pilot scale treatment plants are utilised during the trials. Processes conducted, are the modified Bethell, Lowry and Alternating Pressure Method (APM). Simulated rainfall is applied to every timber pack after treatment. Significant differences between percentage leachates resulting from the timber packs, are determined by the Friedman test and multiple comparison analysis. Investigation of leachate concentrations revealed no world legislative standard. Concentration of copper leachate was suggested as a way to monitor leaching in the aquatic environment. In the soil environment, concentration of chromium leachate was recommended. Heartwood penetration was improved and leachate concentration was decreased when the treating pressure was increased. Concentration of chromium and copper leachate also appeared to decrease when the solution temperature was increased. In contrast, at the higher temperatures, the concentration of arsenic leachate increased. Chromium leachate concentration also decreased when solution strength was increased in Lowry or APM treatment of roundwood. A similar trend was noted when treated timber was subjected to a second stage treatment that involved water or oil. A plastic wrap applied to the timber pack also reduced the concentration of chromium leachate. Chromium leachate concentration and heartwood penetration were influenced by the alteration of the initial vacuum in modified Bethell treatment. Heartwood penetration was improved when low pressure treatment was conducted using the Lowry process, rather than the modified Bethell process.