Agriculture and Food Systems - Theses

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    Studies in animal husbandry and agricultural history
    Peel, Lynnette Jean (1938-) ( 1963)
    About 8,000 years ago man began domesticating wild animals and turning their growth and production to his own use. Since this time considerable progress has been made towards the complete utilisation of domesticated animal products but only now is the efficiency of production of these products being investigated. To increase this efficiency a thorough understanding of animal body functions is essential. The importance to the ruminant of one body function - salivation, has not been established although various aspects of this subject have been investigated in recent years . To continue these investigations the development of total salivation in . lambs and the effects of the diversion of saliva on the rumen function in adult sheep were examined. In this second experiment the effects of anaesthesia and lateral recumbency on rumen function were also examined because if the use of these unnatural conditions in some experimental techniques. Some animals have been domesticated but many have not. Nearly 8,000 years have passed since the predecessors of our present day domesticated animals were tamed and conditions have changed considerably. Hence it is feasible that domesticated animals may be less efficient producers of the animal products we now need, than the wild animals. This may be particularly true with regard to protein production in the form of lean meat. To investigate this proposition a body composition study was made on a population of wild kangaroos, and an assessment made of this animal species as a potential producer of lean meat. Not only may the efficiency of agricultural production be increased by re-assessing the livestock potential, but this may also be achieved by re-assessing the agricultural use of any given area of land. In countries settled and developed by people from other countries, the new settlers have applied to the new land the agricultural practices of the old. This has often occurred inspite of vast physical differences between the two countries. The practices have been modified and adapted, the crops and livestock acclimatised, nevertheless the whole range of possible forms of agriculture are usually never investigated. In southern Victoria, for almost a century, vines were grown by European settlers had been familiar with these plants in their own countries. The success and failure of the cultivation of this crop by Europeans in a country very different from their own is examined in the second part of this thesis.
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    Measurement of body composition of lactating ewes using dual energy x-ray absorptiometry
    Hunter, Trepheena Emily ( 2000)
    The measurement of body composition in live animals has previously been limited to subjective methods such as condition scoring and ultrasound. There are now many direct techniques available to estimate body composition. Dual-energy x-ray absorptiometry (DXA) is a technique that offers a rapid and non-invasive analysis of body composition. It should therefore be possible to use DXA technology to measure changes in body composition in ewes throughout lactation. However DXA has not previously been used for measuring body composition in live sheep. Experimental work was undertaken to determine the correlation between body composition given by DXA and chemical body composition. Correlations between DXA and chemical composition were excellent (R2>0.96 for live animal and R2>0.91 for carcass composition). Regression equations for body composition from DXA and chemical analysis were developed: the equations for analysis in position 1 (entire scan placed in the Right Arm region for analysis) were: fat tissue mass by chemical analysis (FTM) = (1.20 x DXA FTM) - 0.067 (R2=97.8) chemical inorganic matter = (1.08 x DXA bone mineral content) + 0.294 (R2 = 97.2) chemical lean tissue mass (LTM) = (0.933 x DXA LTM) + 1.25 (R2 = 98.9) This study concluded that DXA has great potential for use in live sheep and carcass research. The East Friesian is a relatively new breed in Australia and little is known about its productive capacity under Australian conditions. It is thought, on the basis of work undertaken in New Zealand, that the breed will provide excellent prime lamb mothers that produce large quantities of milk over long periods and are highly fecund. Lamb carcass quality is also claimed by breeders to be excellent. East Friesians were first introduced to Australia in 1996 and most ewes are half-cross, commonly East Friesian x Romney. While the East Friesian is reputedly one of the most productive dairy breeds, the lactational performance of East Friesian cross ewes in Australia is unknown. A study was therefore undertaken to compare the performance of single-bearing East Friesian x Romney ewes and the common Australian prime lamb dam, the Border Leicester x Merino. The results of this study showed that East Friesian x Romney ewes have the potential to produce significantly more milk over the first nine weeks of lactation (mean milk yield: 2.6 ± 0.1 vs 1.9 ± 0.2 kg/day for East Friesian x Romney and Border Leicester x Merino, respectively). The feed intake and changes in liveweight of the two breeds were not significantly different. Mean feed intake over the nine week experimental period was 3.39 ± 0.20 and 3.10 ± 0.16 kg/day for the EFR and BLM ewes, respectively. Mean liveweight was 76.6 ± 4.0 and 77.4 ± 3.2 kg for the EFR and BLM ewes, respectively. The question arising from this initial study was: can East Friesian x Romney ewes produce more milk by using the available feed more efficiently or by mobilising body reserves? This has significant nutritional implications, both at a research and field level. Having determined correlation equations for use of DXA on live sheep, a study of the changes in body composition (fat, lean and bone mineral) during lactation was undertaken to examine the differences between East Friesian x Romney and Border Leicester x Merino ewes. Differences were observed which indicated some differences in body composition between the EFR and BLM ewes: the EFR ewes had a significantly lower percentage of fat tissue mass and higher percentage of lean tissue mass. Some technical issues were defined and further investigation into DXA including the effect of wool cover and gastrointestinal water contents is required. However the present results indicate that DXA provides a sound basis for examining body composition in live sheep.
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    Measurement of the degree of cell rupture in macerated lucerne
    Williamson, Michael John ( 1978)
    Cell rupture is a critical process in the fractionation of green crops. Despite the importance of this process there is no accepted method for quantitatively describing the degree of cell rupture in a sample of macerated forage. Several methods were investigated and developed as measures of the degree of cell rupture in samples of lucerne leaves macerated by extrusion:- (i) Separation of cells and enumeration of intact cells. (ii) Release of cellular substances:- (a) water soluble carbohydrates (b) potassium (c) sodium (d) electrolytes (e) water (iii) Standard juice expression technique as used by other workers. A total rupture standard was considered to be essential, and was achieved in samples of lucerne leaf tissue macerated initially using a mortar and pestle, followed by ten minutes exposure to ultrasound. The performance of these techniques was evaluated in terms of repeatability and of individual and comparative performance over a large range of degrees of maceration. The cell enumeration method was not developed because a suitable agent for separating the cells of lucerne leaf tissue could not be found. All substance release assays gave repeatable estimates of cell rupture and were highly correlated with each other. It was therefore concluded, that the release of cellular substances gave a reliable estimate of the degree of cell rupture. The standard juice expression technique was insensitive to changes in the degree of rupture and was inaccurate at high levels of rupture. It was concluded that the electrolyte release assay was the most appropriate estimate of cell rupture for use in the future.
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    Production of heavy weight cryptorchid and wether lambs
    Channon, Heather Anne ( 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.
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    Factors influencing the efficacy of the boar effect
    Siswadi, Rachmawati ( 1996)
    Maximizing reproductive efficiency is of high potential benefit to the pig industry. Mature boar contact has proven to be very effective in stimulating gilt puberty, although the results tend to be variable. The experimental work in this thesis was conducted in order to elucidate some of the factors which may be contributing to this variation. Three experiments have been carried out to examine the possibility of improving the efficacy of the boar effect. The first experiment investigated the effects of boar contact and transportation on the stimulation of early puberty attainment in gilts. Gilts were allocated to one of six treatments: control - no boar contact or transportation (C); daily boar contact (B1); daily transportation (T); three times daily boar contact (B3); daily boar contact and transportation (B1+T); and three times daily boar contact plus daily transportation (B3+T). Results show that transport alone has little influence on the timing of gilt puberty (P>0.05), although there was a significant positive interaction between transport and boar contact (P<0.01). Frequent boar contact (three-times daily) stimulated a higher proportion of gilts to attain puberty within 20 days of commencement of treatment (P<0.05) than did either once-daily boar contact or no boar contact. In addition, the proportion of gilts reaching puberty was significantly lower when gilts were exposed to daily boar contact, compared to three times daily boar contact. The second experiment studied the efficacy of the boar effect when conducted in a modified Detection and Mating Area (DMA), with or without full boar contact, or in a pen which was not the boar's own. Gilts were assigned to treatments of: no boar contact (C); once daily boar contact (B); DMA exposure (DMA); and boar exposure plus DMA exposure (B+DMA). Mean days taken from the start of the experiment to puberty attainment were significantly fewer (P<0.01) for gilts receiving daily boar contact than for gilts not exposed to boars (36.1 vs. 56.8 days), although boar exposure in addition to DMA exposure tended to produce the lowest mean days to puberty (20.6 days). However, neither days taken to reach puberty, gilt age at puberty, nor gilt weight at puberty was significantly affected by daily exposure to a DMA. The third experiment examined the stimulatory effect of the presence of cycling females on puberty attainment in gilts, and whether the effect was a direct one, or whether it operated via an increase in the stimulus value of the boar. The gilt treatment groups in this experiment were: control - no contact with boars or cycling females (C); contact with cycling females, but not with boars (F); contact with boars, but not with cycling females (B); contact with both boars and cycling females, where the boars were not exposed to the cycling females (BF-1); and contact with both boars and cycling females, where the boars were exposed to the cycling females (BF-2). The proportion of gilts reaching puberty was not significantly influenced by treatment in this study. However, the mean days taken from commencement of treatment until puberty attainment were significantly fewer for those boar exposed gilts not exposed to cycling females than for those gilts receiving neither boar contact nor being exposed to cycling females. Cycling females may exert a minor stimulatory effect on the timing of gilt puberty in non-boar exposed gilts, but this effect is not significant. Results from these studies confirm the efficacy of mature boar contact as a means of inducing early puberty attainment in the young gilt (i.e. the boar effect). Transport did not exert a significant effect on days taken to reach puberty, although transport may be slightly stimulatory to puberty attainment in gilts when used in combination with frequent boar contact. Full boar contact, when given in a DMA, may be a more effective form of gilt puberty stimulation than full boar contact in an isolated pen. Preliminary data also suggest a possible negative interaction between puberty stimuli from the boar and those from cycling females which, if substantiated, may have implications for the management of the replacement gilt.
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    Boar contact frequency and the timing of puberty in gilts
    Philip, Geogy ( 1995)
    The literature relating to the natural attainment of puberty and those factors involved in the early induction of puberty in gilts is reviewed. The first two experiments suggested that motivated/high stimulus value boar(s) may release sufficient stimuli to overcome the seasonal change that mediates the ability of the gilt to attain natural puberty. These experiments also demonstrated that increasing the, frequency of daily boar contact provided sufficient 'cumulative stimulus' to initiate earlier pubertal development, when compared with once-daily contact (P<0.05). In fact, boar exposure three times daily significantly reduced mean gilt age at puberty relative to once-daily boar exposure (183.2 � 2.71 vs. 196.0 � 3.00 days of age respectively, P<0.01). Twice-daily boar contact resulted in an intermediate mean gilt age at puberty (190.3 � 3.01 days). There was also a trend towards a higher proportion of gilts reaching puberty earlier with increasing frequency of boar contact but this effect became less evident after day 20 of commencement of treatment. In a third experiment increasing boar contact frequency to 8 times per day failed to improve the proportion of gilts attaining precocious puberty compared with 4 times daily contact. This suggests that maximum response to boar contact is achieved using 3-4 times exposure per day. The fourth experiment again confirmed that the boar effect is enhanced when boar contact occurs several times each day. It also indicated that transport 'stress' in conjunction with frequent boar contact may further reduce gilt age at puberty. However, transport alone did not significantly advance the timing of gilt puberty attainment. A final experiment suggested that the efficacy of the boar effect can also be maximised by increasing the frequency of boar - contact when large gilt group sizes are involved. However, it may be necessary to increase exposure times (>20 minutes per exposure) to obtain this benefit. No advantage of increasing the number of boars in the exposure groups from 2 to 4 or 6 was apparent in this study.
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    Effects of irrigation on the roots of pastures
    Cullen, Peter (1943-) ( 1969)
    An experiment was conducted in order to investigate the effects of wetting the soil to a range of depths, on the root growth and top growth of some pasture species. The experiment was done within a glasshouse, using a sandy loam soil; the pasture species studied were white clover, ryegrass and subterranean clover. Gypsum block readings, and visual assessment of the moisture status of the soil (as seen through the transparent walls of the containers) were used to decide when to apply water. The soil was maintained within the wetter 2/3 of the available moisture range, so that the effects of drying cycles were avoided. For each species the depth of wetting had a marked effect on the depth of roots; in all treatments, the roots completely occupied the depth of wetted soil. With the deeper wetting treatments both of the perennial species showed a marked increase in the weight of tops, but the annual subterranean clover showed no significant differences. On the other hand, the effect of deeper wettings on the weight of roots was significantly greater for white clover; it was not significantly different for ryegrass; but it was significantly less for subterranean clover.
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    The digestion of ruminant feeds in vitro
    Clark, Jennifer ( 1974)
    Systems of feed evaluation require the determination of the digestibility of the components of the feeds. The determination of digestibility in vivo is laborious and expensive, thus considerable research effort has been directed towards the determination of techniques to measure digestibility in vitro. The development of laboratory methods for assessing the digestibility of ruminant feeds is discussed. A two- stage technique, composed of microbial and enzymatic digestion stages, has currently been applied to the analysis of herbages, mixed forages, wood, brassicas, concentrates and silages. The digestibility of substrates determined by means of the two-stage in vitro method may be affected by the method of preparation of the substrate, the pH and duration of the microbial digestion, and the ratio of the rumen fluid to the buffer solution. The source of the rumen fluid may also affect digestibility in vitro , since the activity of this. fluid varies between species, individuals within species and the diet of the donor animals. Variation due to the diet of the donor may be minimized by means of a diet with an adequate crude protein content. Regression analyses are presented relating in vivo digestibilities to values of digestibility estimated by various laboratory procedures. In vivo digestibility may be predicted more accurately by the in vitro digestibility technique than by the nylon bag technique or by chemical methods of evaluation. However, methods incorporating the digestibility of cell wall material, digestion by fungal cellulase or summative equations of chemical constituents may be used as alternatives to the two-stage digestibility technique. The review is concluded with a discussion of the relationships between in vitro digestibility values of feeds and the values of total digestible nutrients, index of nutritive value, starch equivalent, voluntary intake, digestible energy and metabolizable energy , the last two of which are currently used to formulate rations for ruminants.
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    Acute prenatal androgen treatment in sheep
    Gill, Jeffrey William ( 1994)
    The steroid environment of the cell nucleus in differentiating mammals is a major determinant of subsequent cellular function. The exogenous manipulation of this environment has resulted in permanent changes in metabolism, behaviour, reproduction, endocrinology and growth. The experiments described in this thesis suggest that an acute exposure to exogenous androgen, established as an intramuscular depot in the gravid ewe, can effect these changes. The growth responses resulting from acute prenatal androgen treatment (APAT) are similar to those reported for chronic androgenization.The undesirable side effects of androgenization, e.g. reduced birthweight, deformed external female genitalia and masculine urination posture, can be avoided with APAT. The literature and the experimental data indicate that mammalian development is strongly influenced by tissue steroid status. Furthermore, the literature and the experimental data suggest that both the timing and duration of the modification of mammalian developmental steroid status (MDSS) affect the response of ovine tissues to androgens. Some of the observed responses appear refractory in nature. The periods of sensitivity to MDSS manipulation differ between tissues and between species. MDSS manipulation via APAT is capable of effecting changes to tissues not normally considered sexually dimorphic, including the ovine pancreas, liver, brain, kidney, bone and wool follicle.
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