School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemAn evaluation of the role of extension in the Australian pig industry( 1978)Australian agriculture is adjusting to changes in technology, economic circumstances and markets. Extension services as much as the producers' need to change in response to changing industry needs, market trends and consumer demands. There has been much discussion on the problems that these changes present for extension, but none on the basis of empirical research or social science theories. A research program was developed to define the changes taking place in the structure and organisation of the Australian pig industry, and to identify the implications of these changes for pig producers and for extension agencies such as State Departments of Agriculture. The conclusion drawn from the review of the industry situation and from a Delphi survey of 10 experts in the pig industry was that the industry will become more technical and commercialised requiring continual adaptation by the producers to technical and economic changes in order to maintain and increase production efficiency. The survey results showed that a degree of assistance from research and extension was expected by producers to help them maintain and improve production efficiency. Based on the Theory of Personal Constructs, Kelly (1955) an interactive psychological testing procedure known as the Repertory grid was used to record producers' and extension officers' perceptions of each other and of extension services. Twenty pig industry officers, 16 non extension users, 20 extension users and 16 large commercial producers were interviewed. Separate analyses were carried out on the grids of individual subjects, providing profiles of constructs typically used by the subjects in relating to and evaluating people. The results clearly identified the constructs which farmers used in relating to extension advisers and advice. In general, all groups of subjects tended to stereotype people with whom they associated. Combination of both the results within subject groups revealed evidence of commonality within and between the groups in their perceptions. The extension officers saw themselves as progressive and useful while a large number of the producers saw them as theoretical and irrelevant. Extension users held favourable attitudes towards professional agricultural advisers, while large commercial producers and non extension users criticised them on the grounds that they were difficult to communicate with and lacking practical experience. As a group, extension officers were not aware of the questioned relevance of their advice nor of the difficulty experienced by producers in communicating with them. Owing to their practical background and shared experiences, all producers saw other producers as useful and as the most relevant source of advice. The roles they expect him to perform and the characteristics that producers expect from a professional extension adviser have been identified and their implications for the extension officer are discussed. The most obvious implications of the findings are that extension advisers fail to establish the relevance of information within the farmers' context of what is relevant. Based on the findings of the research the theory is proposed that extension programmes will be most successful when producers and extension workers share common perceptions of relevant problems. A philosophy and practice of extension is proposed to meet the farmers' own perception of needs. The interpretation of the results in terms of Personal Construct theory leads to the development of the model of human behaviour, that is, "man as an actor" instead of "man as something being acted upon". A philosophy of extension is developed based on the belief that extension can only be successful if it provides what farmers want. The philosophy states that extension should provide a helping role by facilitating, developing and supporting "man the actor" without dominating or controlling his actions. A practice of extension operating within the boundaries of the proposed new philosophy is developed from the helping relationship model of Carkhuff (1969). The goals of extension are defined as exploration, understanding and action which lead directly to the need for skills which are defined as the "interface skills" of attending, responding, personalising and initiating. The need for and the nature of extension training to provide extension officers with "interface skills" is discussed.
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ItemSocial and sexual factors affecting reproduction of the domestic boar( 1978)This thesis describes the results of work in three general areas; (i) the influence 0f the social environment during rearing and after puberty on the sexual behaviour of the boar, (ii) the role of the courting behaviour of the boar in his reproductive performance, and (iii) the influence of sexual stimulation on the spermatozoan output of the boar. The major portion of the work relates to the importance of the social environment. Boars reared from three weeks of age in the absence of visual and physical contact with pigs had markedly lower copulatory performance and level of courting activity compared with those reared from three weeks in either an all-male or mixed-sex group. Lack of physical contact with pigs during rearing was responsible for approximately 70% of this depression in copulatory performance. The copulatory performance of boars reared from 12 weeks of age in the absence of visual and physical contact with pigs was considerably less than that of boars reared in an all-male group, but the difference was not significant. Boars reared from three or 12 weeks- of age individually in adjacent wire-mesh pens had similar copulatory performance to that of group-reared boars. However, an apparently important feature of courting behaviour, 'nosing activity', was significantly reduced for those boars reared from three weeks individually in adjacent wire-mesh pens. These data were interpreted as evidence of the importance of social contact, particularly physical contact with boars or gilts, during rearing on the level of sexual behaviour of the boar. In addition to the social environment during rearing, the social environment after puberty was demonstrated to have a dramatic influence on the level of sexual behaviour of the boar. Isolation of post-pubertal boars from female pigs for six weeks significantly reduced their copulatory performance and level of courting activity. The stimuli received from the presence of sexually receptive or sexually non-receptive female pigs were equally capable of maintaining the level of sexual behaviour of the boar. Two experiments conducted at a commercial piggery revealed the importance of the courting behaviour of the boar on reproductive performance. A significant positive correlation was found between the observed level of nosing activity during courting and the conception rate record of the boar. The proposal that the nosing activity of the boar may stimulate one or more physiological mechanisms leading to fertilisation in the sow is supported by the results of the second experiment. Brief courting of sows by a boar prior to artificial insemination significantly increased the farrowing rate and litter size of group-housed sows. Finally, sexual stimulation of boars prior to semen collection significantly increased the number of spermatozoa . in the sperm-rich fraction of the ejaculate. The technique of sexual stimulation of the boar involved either allowing the boar a false mount and then briefly restraining him or allowing the boar to observe a semen collection. The former technique failed to maintain a significant increase in the yield of spermatozoa from the sperm-rich fraction over a six-week collection period. Prostaglandin F2a, which may be involved in the mechanism by which sexual stimulation increases the number of spermatozoa in the short term, was also studied. Administration of 20 mg of PGF2a 30 minutes before collection significantly increased the number of spermatozoa in the sperm-rich fraction of the ejaculate. The experiments of this thesis demonstrate that sexual and social factors have a major influence on the reproduction of the domestic boar.
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ItemInvestigation of infertility in mated sows under intensive conditions( 1978)This thesis details a series of experiments investigating infertility in mated sows. The particular problem of delayed return to oestrus in sows following a normal mating to a fertile boar, was studied. The vaginal biopsy and ultrasonic methods of pregnancy diagnosis were tested for use in diagnosis of pregnancy in herds where a large proportion of sows showed a delayed return to oestrus. These methods were found unsuitable in this instance and so plasma progesterone and oestrogen levels were examined in sows,18 days after mating, in an attempt to identify affected sows. Facilities for hormone analysis were established and workable assays for progesterone, oestrogen and corticoid levels developed. Two laboratory experiments accompanied these field trials. The first was to study the temporal relationships between progesterone, oestrogen, and corticoid levels during the oestrous cycle and early pregnancy in sows. The second was to look at the effects of ACTH administration on plasma progesterone, oestrogen, corticoid, and LH levels and upon oestrus and ovulation. These experiments are described and the results discussed in this thesis. An integrating discussion and summary is included to link each section and to combine the conclusions of this thesis.
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ItemComposition of commercial pig diets and utilization of piggery wastes( 1977)The work presented in this thesis was part of an integrated study conducted by the School. of Agriculture and Forestry into various aspects of piggery waste utilization. Particular attention was given to the occurrence and source of mineral elements in pig diets and piggery wastes. Results of analysis of commercial pig diets and piggery wastes are discussed in relation to nutritional requirements and toxicities and from environmental and legislative aspects. The Literature Review in Chapter 2 describes how similarities in the atomic orbital configurations of some transition elements and oxy-anions can explain the synergisms and antagonisms displayed by these chemical entities in biological systems. In particular, the concept of orbital equivalence is used to explain some of the better known cases of mineral antagonisms affecting the health and nutrition of livestock. The antagonism between sulphate and molybdate ions is discussed relative to their ionic structures and to their respective involvements in copper metabolism. The interactions of copper, zinc and iron are examined, particularly in relation to pig nutrition. Interactions between copper, zinc and cadmium are related to their orbital structures and to their ability to form metallothioneins. The ability of high levels of copper and zinc to induce selenium deficiency in chicks is discussed and associated with the similar orbital configurations of zinc, copper and selenate ions. Caution is proposed in the formulation and mineral supplementation of multi-constituent diets used in intensive animal production. Procedures used in the development and calibration of analytical techniques for the determination of eleven elements in pig faeces and pig diets are described in Chapter 3. Copper, zinc, iron, cadmium, lead; sodium, potassium, magnesium, calcium and phosphorus were measured from a single sample digestion using a nitric-perchloric acid mixture. Phosphorus content in the digest was determined colorimetrically and the remaining elements by atomic absorption spectrometry. A separate digestion procedure was required for arsenic which was then measured by atomic absorption spectrometry after generation of arsenic as its hydride. Accuracy and precision of the techniques were rigorously tested using standard addition and recovery procedures- and comparison of values obtained after analysis of the U.S. National bureau of Standards Reference Material ''Orchard Leaves". Chapter 4 reports the chemical composition of pig diets, ingredients of diets and mineral-vitamin supplements collected from 24 commercial piggeries in Victoria. An evaluation of the diets relative to the suggested dietary mineral requirements for grower pigs proposed by the Agricultural Research Council (A.R.C.) indicated that mineral imbalances occurred in many of the diets. High levels of cadmium and lead found in some diets originated principally as contaminants of mineral additives and from meat meals, meat and bone meals and fish meals. The mineral content of the diets was found to be highly variable and indicated differences in choice of dietary ingredients and in the practice of mineral supplementation. Copper, zinc, and iron levels in the diets were particularly variable and in the case of zinc and iron were present at concentrations far in excess of the levels suggested by.the A.R.C. Chapter 5 describes the chemical composition and in vitro organic matter digestibility (OMD) of pig faeces samples collected from 24 piggeries in Victoria. Pig faeces are shown to be highly variable in chemical and nutrient content and, in some instances, to contain high levels of potentially toxic mineral elements such as copper, cadmium, lead and arsenic. Wide ranges in in vitro OMD values, proximate constituent concentrations and cell wall composition were also recorded. Multiple regression analysis associated low in vitro OMD with high values of cell wall content, phosphorus, copper and lignin/cell wall. Standard additions of phosphorus and copper to pig faeces samples undergoing in vitro fermentation significantly lowered the OMD values of these samples, contributing further evidence of the possible inhibitory effects of these elements to the digestive processes of the ruminant. Some health aspects of refeeding pig faeces as an ingredient in diets for ruminants are discussed, particularly in relation to the presence of toxic minerals such as copper, cadmium and lead. In Chapter 6 a procedure is described for calculating the chemical composition of pig manure using dietary composition, recommended feed intakes, published retention values for each element and estimated excreta outputs fin. an "average" pig of 45 kg liveweight. The variability in the calculated composition of manure is discussed in relation to existing and proposed guidelines limiting the rates of application of pig manure to land. Some aspects of the proposed guidelines for Victoria are discussed; particularly in relation to the suggested maximum rates of manure application to provide not more than 500 kg of nitrogen or 300 kg of potassium/hectare/ annum. Because of the range in the estimated nitrogen content of pig manures, the quantities of manure supplying 500 kg of nitrogen were calculated to range from 46 - 123 tonnes with an average of 63 tonnes. Included in these quantities were widely varying amounts of other elements which would be applied to land with 500 kg of nitrogen; some of which are known to pose environmental problems through leaching to ground water, as run-off to waterways or through ingestion by grazing animals. The potential environmental hazards of applying large amounts of minerals, including heavy metals, to land are discussed and a method is proposed which would permit a more accurate estimate of manure loading rates to provide 500 kg nitrogen/ hectare of land.
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