School of Agriculture, Food and Ecosystem Sciences - Theses

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Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows

Eagles, Vicki Maree. (University of Melbourne, 2000)

Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.
Studies on resynchronisation of oestrus with progesterone and oestradiol benzoate in Holstein cows

Eagles, Vicki Maree. (University of Melbourne, 2000)

Resynchronisation of return-to-service in cows using progesterone and oestradiol benzoate is an integral part of current recommendations for Controlled Breeding Programs and the treatment of postpartum anovulatory anoestrus to improve herd reproductive performance. This thesis describes the results of a series of three experiments designed to test some of the hypotheses on the principles of resynchronisation based on each of the following questions: a) What concentrations of plasma progesterone are sustained by re-using a CIDR device for resynchronisation as compared to concentrations sustained by a new device? b) What proportion of the cows that are not confirmed pregnant to first insemination can be successfully resynchronised; and, do any pregnant cows show overt symptoms of oestrus as a consequence of the resynchronisation treatment? c) Does the type of the resynchronisation treatment for cows originally diagnosed with anovulatory anoestrus affect the efficacy of treating this common condition in Holstein cows? Experiment 1: To identify changes in plasma progesterone concentration, a sequence of treatments with a new or recycled CIDR device in ovariectomised cows was used to model the respective plasma progesterone profiles in treated cycling or anoestrous cows. A total of 9 ovariectomised non-lactating Holstein cows were each treated sequentially with a new CIDR device inserted for 6 days (Round 1); then a new CIDR device was inserted 4 days after the first device was withdrawn, with an insertion period of 6 days (Round 2); and finally, the same device initially used in Round 1 was re-inserted for a period of 7 days (Round 3). A 1mg oestradiol benzoate injection was administered 24 hours after device removal at the conclusion of each Round. Every cow was observed for signs of behavioural oestrus during the subsequent 72 h period. Blood samples were taken at specified intervals during the period of device insertion (3 hours, Day 1 and Day 6 post-insertion), as well as immediately preceding device insertion and following removal 6 or 7 days later. The average plasma progesterone concentrations over the 6-day insertion period for each Round 1, 2 and 3 were: 3.2, 2.2 and 1.7 ng/mL, respectively. Concentrations were significantly higher in Round 1 (P<0.01), but were similar in Rounds 2 and 3. The highest progesterone concentrations in Round 1 were those measured 3 and 24 hours after device insertion. This reflected the delay in the induction of hepatic enzymes that metabolise progesterone and are not normally required by ovariectomised cows. The progesterone content of a CIDR device declined by 23% (1.83g 1.41g) over the first 6 days of insertion and by a further 20% (1.41g -� 0.98g) over the second 7 days of insertion. Every cow displayed obvious overt symptoms of behavioural oestrus within 48 hours of being injected with oestradiol benzoate in each Round. In conclusion, ovariectomised cows were a suitable model to characterise subtle changes in the concentration of plasma progesterone which occurred in response to administration of a new or recycled CIDR device per vaginum for 6 or 7 days. The profile of changes in plasma progesterone as a consequence of device insertion and removal was rapid and was influenced by previous exposure to progesterone. Similar plasma progesterone profiles were associated with the use of a new CIDR device or a recycled device when animals had been previously exposed to elevated levels of progesterone. Experiment 2: The characterisation of the profile of changes in plasma progesterone concentration in response to a resynchronisation treatment initiated during middioestrus and subsequent to a synchronised first oestrus, in lactating Holstein cows involved in a commercial Controlled Breeding Program. It was also to determine if a recycled device could elevate plasma progesterone concentration to delay the onset of oestrus and synchronise returns-to-service. Plasma progesterone concentrations were measured before, during and following the resynchronisation treatment with a recycled CIDR device. Every enrolled cow (n=42) which had been initially synchronised using progesterone, prostaglandin F2a and oestradiol benzoate along with about 160 herd mates, had a recycled CIDR device re-inserted per vaginum 13 days after its first insemination. Most (n=30) of these cows were also injected with 1mg oestradiol benzoate (Group 2 & Group 3) at device re-insertion and every one of them was injected with the same dose of oestradiol benzoate 24 hours after device removal occurring 7 (Group 2) or 8 (Group 1 & Group 3) days after re-insertion. These variations in resynchronisation treatment did not affect any of the measured responses. There were two distinct populations of progesterone concentrations based on 4 blood samples taken 24 hours following device removal. The High progesterone sub-group (n=23) averaged 4.15 ng/mL (range=1.42 to 6.77 ng/mL); the Low progesterone sub-group (n= 19) averaged 0.08 ng/ml (range 0.03 to 0.14 ng/mL). Every one of the latter sub-group was detected in oestrus and inseminated from 24 to 96 hours after device removal. None of the animals in the former subgroup was detected in oestrus. However, 4 of these 23 animals (17%) were subsequently found to have not established a normal pregnancy, even though they had progesterone concentrations at 26 days after their first insemination which were indistinguishable from their 19 contemporaries who were confirmed pregnant to first insemination. These 4 cows were typical of those described as "Phantom Cows." In conclusion, resynchronisation treatment with a recycled device was effective in extending the oestrous cycle and stimulated return-to-service of animals with low plasma progesterone concentrations during the expected period of return within 96 hours after device removal. The treatment was less efficient at synchronising oestrus in animals which were retrospectively diagnosed not pregnant at pregnancy diagnosis 6 to 8 weeks after the conclusion of the Al period ("Phantom Cow Syndrome") but which had high plasma progesterone concentrations throughout the resynchronisation period. Experiment 3: To evaluate the reproductive responses of varied resynchronisation methods initiated during mid-dioestrus (Day 13 post-insemination) with progesterone and oestradiol benzoate to synchronise returns-to-service in cows which had initially received a standard treatment for anovulatory anoestrus; and to demonstrate the reproductive impact on the 6-week in-calf rate of these cows compared to their untreated cycling herd mates. A total of 810 cows which were diagnosed as anoestrus in 16 seasonally calving (3556 total cows) herds serviced by the Maffra Veterinary Clinic in 1998 were initially treated with progesterone by inserting a CIDR device for 6 days, and then injecting oestradiol benzoate (1mg) at 24 hours after device removal. Within 72 hours of this injection, 691 of these cows (85.3%) were detected in oestrus and inseminated. Each of these 691 cows had a recycled CIDR device re-inserted 16 days after initial device removal (13 � 1 day post-first insemination) and was also injected with 1mg oestradiol benzoate. The re-inserted device was withdrawn after 7 days. On the eighth day, half of these cows (n=334) were injected with 0.5mg oestradiol benzoate (2 x ODB; Group 2) while the other half (n=357) received no further treatment (1 x ODB; Group 1). a) The improved reproductive performance of cows in Group 2 occurred because more cows returned for a second insemination over the 4-day period following the second oestradiol benzoate injection (post-device removal) (44.6% versus 28.3%); b) the re-submission rate among cows subsequently confirmed as not conceiving to first insemination was greater (65.3% versus 40.1%); c) and the conception rates to first or second inseminations were similar for cows in the two Groups (1St = 29% versus. 32%; 2nd = 44.5% versus. 46.4%). The pregnancy rate for cows in Group 2 increased from 33.4% on Day 22 of inseminating to 55.4% by Day 26 compared to changes from 31.9% to 48.7% for cows in Group 1. The median interval from mating start date to conception for cows in the Group 2 was 23 days compared to 42 days for cows in Group 1 and 25 days for cycling herd mates. Comparable mean intervals to conception for these Groups were 31.2, 34.0 and 27.8 days respectively. Final in-calf figures for those animals in Group 2 were similar to those for cycling cows (86.5% versus. 85.4%), and higher than those for cows in Group 1 (82.9%; P<0.05). The results of this trial showed that the form of resynchronisation treatment had a significant effect on the outcome and the efficacy of treating cows for anovulatory anoestrus. In summary, this series of trials showed that: a) recycled CIDR devices released sufficient progesterone to resynchronise oestrus in previously synchronised cows; b) the resynchronisation treatments used in a Controlled Breeding Program achieved the desired objective among cows in which luteolysis had occurred spontaneously during the period of re-treatment without producing a false oestrus in cows with high plasma progesterone concentrations following resynchronisation; c) the resynchronisation treatment used in cows with anovulatory anoestrous requires oestradiol benzoate (0.5mg) to be injected after device removal to increase submission rates to the second insemination; and, d) that the resynchronisation treatment was ineffective with "Phantom Cows" Further studies are still required for improvement to be gained in the fertility of the first oestrus following hormonal treatment and the subsequent resynchronised inseminations of treated anovulatory anoestrous cows to achieve similar reproductive performance to their untreated cycling herd mates. In addition, a better understanding of the characteristics of the "Phantom Cow" following a first insemination is required to develop both management strategies and effective hormonal therapy to reduce their impact on herd fertility. These two factors combined are major limitations resulting in compromised reproductive performance in lactating Holstein cows in the commercial seasonally calving herds in Victoria.
Economic evaluation of feeding grain to dairy cows in Western Victoria

Kelly, Hugh D. (University of Melbourne, 1999)

This study is set in Western Victoria, where the dairy farming systems are characterized by springdominant pasture growth, low pasture growth in summer and moderate growth of pasture in autumn. This, coupled with either late winter calving or early autumn calving, creates pasture deficits, which occur in early and late lactation. The challenge for farmers in Western Victoria is to fill those feed gaps with supplements with the aim of maintaining or increasing profitability. Over a production year, feed supply is provided by a mix of fixed and variable inputs. Variable inputs such as working capital, fertilizers, seed, rainfall, irrigation, conserved fodders and concentrate feeds are added to the land, cows, labour and capital infrastructure. The worth of any one of these variable inputs is determined by the amount it contributes to the farm profitability during the production year. The aim of this study is to evaluate the economic effects of different grain feeding regimes on dairy farms in Western Victoria and determine whether net benefits could be gained from implementing a range of possible grain feeding regimes. Pasture based animal production systems are complicated because of the way the animals, water, pasture, fodder and concentrates interact during different stages of the production year. This means that both a short and medium term view has to be taken to make decisions about feed supply. There is also a need to evaluate the effect of unexpected changes to variable input supply and contingency measures that can be adopted to minimise negative impacts on the system. Further complications arise when trying to evaluate the changes to dairy farming systems because the production response function of each cow and the herd cannot be exactly known with great accuracy before the feed decisions are taken. As well, the law of diminishing marginal returns is at work all the time. The research undertaken in this project was based on a series of case studies of dairy farms in different areas throughout Western Victoria. These farms were selected to represent the different types of farming systems and areas within the region. The operation of the farms was studied at considerable depth to gain a thorough understanding of how each farming system operated. The operation of the farm was modeled using the dairy farm simulation program called UDDER, which can be used to simulate water-animal-pasture- fodder-concentrate interactions for different types of feeding strategies. Their effects on milk production over a year can be evaluated. A series of changes to the grain feeding regime were simulated on each farm to evaluate whether gains could be achieved from altering the timing and quantity of grain fed during the year. The technical information from the model UDDER was then analysed in an economic context using a partial budget model that was developed. This partial budget decision support tool helps farmers identify the essential feeding factors that affect the viability of a farming system and the relative merit of alternative grain feeding tactics and strategies. In this project it was identified that net gains could be made with strategic increases in grain feeding on the individual farming systems. Generally, if the grain fed to the dairy herd was increased during early and late lactation, extra gains were predicted to be achievable. However, substantial gains were also predicted if extra grain was fed to the herd during mid-lactation. When grain feeding levels were reduced, large losses were experienced. This indicates the reliance of the case study dairy herds on grain to produce milk if they are to maintain their current levels of profitability. This study shows that farmers may be able to earn larger profits with greater precision in quantity and timing of grain feeding. However, increases in some grain feeding will not always provide immediate extra gains. Like farm management in general, dairy feed management involves finding and mastering the key pieces of information and processing it in the whole farm context with both tactical and strategic perspectives in mind.
Economic evaluation of feeding grain to dairy cows in Western Victoria

Kelly, Hugh D. (University of Melbourne, 1999)

This study is set in Western Victoria, where the dairy farming systems are characterized by springdominant pasture growth, low pasture growth in summer and moderate growth of pasture in autumn. This, coupled with either late winter calving or early autumn calving, creates pasture deficits, which occur in early and late lactation. The challenge for farmers in Western Victoria is to fill those feed gaps with supplements with the aim of maintaining or increasing profitability. Over a production year, feed supply is provided by a mix of fixed and variable inputs. Variable inputs such as working capital, fertilizers, seed, rainfall, irrigation, conserved fodders and concentrate feeds are added to the land, cows, labour and capital infrastructure. The worth of any one of these variable inputs is determined by the amount it contributes to the farm profitability during the production year. The aim of this study is to evaluate the economic effects of different grain feeding regimes on dairy farms in Western Victoria and determine whether net benefits could be gained from implementing a range of possible grain feeding regimes. Pasture based animal production systems are complicated because of the way the animals, water, pasture, fodder and concentrates interact during different stages of the production year. This means that both a short and medium term view has to be taken to make decisions about feed supply. There is also a need to evaluate the effect of unexpected changes to variable input supply and contingency measures that can be adopted to minimise negative impacts on the system. Further complications arise when trying to evaluate the changes to dairy farming systems because the production response function of each cow and the herd cannot be exactly known with great accuracy before the feed decisions are taken. As well, the law of diminishing marginal returns is at work all the time. The research undertaken in this project was based on a series of case studies of dairy farms in different areas throughout Western Victoria. These farms were selected to represent the different types of farming systems and areas within the region. The operation of the farms was studied at considerable depth to gain a thorough understanding of how each farming system operated. The operation of the farm was modeled using the dairy farm simulation program called UDDER, which can be used to simulate water-animal-pasture- fodder-concentrate interactions for different types of feeding strategies. Their effects on milk production over a year can be evaluated. A series of changes to the grain feeding regime were simulated on each farm to evaluate whether gains could be achieved from altering the timing and quantity of grain fed during the year. The technical information from the model UDDER was then analysed in an economic context using a partial budget model that was developed. This partial budget decision support tool helps farmers identify the essential feeding factors that affect the viability of a farming system and the relative merit of alternative grain feeding tactics and strategies. In this project it was identified that net gains could be made with strategic increases in grain feeding on the individual farming systems. Generally, if the grain fed to the dairy herd was increased during early and late lactation, extra gains were predicted to be achievable. However, substantial gains were also predicted if extra grain was fed to the herd during mid-lactation. When grain feeding levels were reduced, large losses were experienced. This indicates the reliance of the case study dairy herds on grain to produce milk if they are to maintain their current levels of profitability. This study shows that farmers may be able to earn larger profits with greater precision in quantity and timing of grain feeding. However, increases in some grain feeding will not always provide immediate extra gains. Like farm management in general, dairy feed management involves finding and mastering the key pieces of information and processing it in the whole farm context with both tactical and strategic perspectives in mind.
Fallow-crop water balance and recharge relationships in the Victorian Mallee

O'Connell, M. G. (Mark Glenn) (University of Melbourne, 1998)

Background: The Victorian Mallee has a semi-arid climate and cereal production is the major agricultural landuse. Alkaline calcareous soils dominate the region. Cropping in the Mallee is subject to variation in growing season rainfall. Long (winter) fallows are a robust and common practice prior to wheat. Fallows may be viewed as a drought prevention strategy in the rainfed Mallee. Water conserved by fallows supplements growing-season rainfall and thereby reduces annual yield variability. The risk is wind erosion and deep drainage beyond the rootzone of crops. Deep drainage represents incomplete utilisation of water for crop production and contributes to dryland salinity when it enters saline groundwater (potential groundwater recharge) (Chapter 1). This thesis presents work conducted in the field by experimentation and by simulation modelling. A field study at Walpeup (35� 07' S., 141� 58' E.) was conducted over 5 years (1993-1997) to investigate substituting mustard (Brassica juncea) for 18-month long-fallows. Two crop sequences (fallow-wheat-pea [FWP] v. mustard-wheat-pea [MWP]) were examined. The field experiments were designed to appraise FWP v. MWP sequences by investigating soil-water balance, productivity, potential recharge to groundwater and episodic drainage (Chapters 2 & 3). Determination of crop interception and utilisation of photosynthetically active radiation (PAR) were investigated in the field (Chapter 4). Simulation modelling was used to identify cropping practices conducive to longterm productivity and minimal drainage in the region. The O'Leary-Connor model (O'Leary and Connor 1996a,b) was appraised against observed measures (1993- 1998) of growth and yield of wheat, and rootzone soil-water balance under wheat and fallow (Chapter 5: Experiment I). Effects of crop rotation, stubble and tillage management on deep drainage of light (sandy loam) and heavy (clay) textured soils were then investigated by running the O'Leary-Connor model using 58 y of historical climatic data (Chapter 5: Experiment II). Field experimentation: The field experiment demonstrated effects of substituting mustard for fallowing. Aspects of water balance, growth and yield of FWP and MWP sequences were investigated in Chapter 2. Water limited crop production in each growing-season throughout the study. Rootzone soil-water conservation from fallowing in sequence FWP increased wheat growth, yield and water use under severe drought. By contrast, the data reveal that pea water relations and productivity was not influenced by crop sequence. Mustard growth was variable with low yields. Deep drainage was investigated (1993-1998) under FWP and MWP sequences by measuring changes in subsoil-water and by drainage lysimetry (Chapter 3). The former showed greater drainage of FWP (12 mm/y) compared to MWP (5 mm/y). Two major drainage events were confined to a specific phase of the FWP sequence (5.0 mm & 4.3 mm), illustrating the difficulty of reconciling drainage estimates by alternative approaches in a semi-arid environment over a relatively short period 5 y). Radiation interception by wheat, pea and mustard was investigated in Chapter 4. The fraction of intercepted PAR (f), canopy extinction coefficient and radiation-use efficiency were determined for each crop. Aridity resulted in incomplete canopy cover. Fallowing increased f of wheat under favourable (1996) and drought (1994) growing seasons. Estimates of extinction coefficient for wheat, pea and mustard were 0.82, 0.76 and 0.68, respectively. Estimated pre-anthesis radiation-use efficiency for wheat, pea and mustard were 1.75, 1.47 and 1.85 (g aboveground biomass/MJ intercepted PAR), respectively. Simulation modelling: The O'Leary-Connor model provided a good representation of wheat growth, and rootzone soil water (Chapter' 5: Experiment I), justifying use of the unadjusted model, as a tool for examination of water balance under agronomic scenarios in this study (Chapter 5: Experiment II). The investigation suggested greater soil-water conservation under fallowing compared to continuous cropping. Simulated grain yield responded to trends in soil water in accordance with water limitations imposed by the rainfed environment. Simulated drainage was episodic. Soil hydraulic properties and agronomic management influenced total drainage. Least drainage occurred on the heavy textured clay, reflecting soil-water holding capacity and water use associated with crop production. No direct relationships between drainage and rainfall were evident. Continuously cropped (WW) sequences drained less than fallow-wheat (FW). Fallow management influenced water storage and drainage. Stubble-retained zerotilled fallows conserved more soil water and subsequently had greatest drainage. Conventional tillage and stubble burning decreased drainage, but increased runoff and soil surface evaporation. On the lighter soil type, WW and FW drained ~6 % of years without stubble retention, but 10-70 % of years when stubble was retained, with a increase in drainage from 0.5 mm/y to 10-20 mm/y, respectively. By contrast, the heavier clay failed to drain without stubble, and drained in the range, 5-24 % of years when stubble was retained (range, 2-17 mm/y). Overall, fallowing reduced yield failure, but, in conjunction with stubble retention, increased episodic and total drainage on both soil types under the climatic conditions experienced in the Mallee. Conclusion: Outcomes of both field and simulation studies confirms that fallowing increases drainage (potential groundwater recharge). Although, non-fallow annual cropping sequences failed to provide a dry soil profile at sowing for prevention of drainage, especially in wet years. Strategies that use agronomic perennials to dewater subsoils prior to sowing require further investigation.
Fallow-crop water balance and recharge relationships in the Victorian Mallee

O'Connell, M. G. (Mark Glenn) (University of Melbourne, 1998)

Background: The Victorian Mallee has a semi-arid climate and cereal production is the major agricultural landuse. Alkaline calcareous soils dominate the region. Cropping in the Mallee is subject to variation in growing season rainfall. Long (winter) fallows are a robust and common practice prior to wheat. Fallows may be viewed as a drought prevention strategy in the rainfed Mallee. Water conserved by fallows supplements growing-season rainfall and thereby reduces annual yield variability. The risk is wind erosion and deep drainage beyond the rootzone of crops. Deep drainage represents incomplete utilisation of water for crop production and contributes to dryland salinity when it enters saline groundwater (potential groundwater recharge) (Chapter 1). This thesis presents work conducted in the field by experimentation and by simulation modelling. A field study at Walpeup (35� 07' S., 141� 58' E.) was conducted over 5 years (1993-1997) to investigate substituting mustard (Brassica juncea) for 18-month long-fallows. Two crop sequences (fallow-wheat-pea [FWP] v. mustard-wheat-pea [MWP]) were examined. The field experiments were designed to appraise FWP v. MWP sequences by investigating soil-water balance, productivity, potential recharge to groundwater and episodic drainage (Chapters 2 & 3). Determination of crop interception and utilisation of photosynthetically active radiation (PAR) were investigated in the field (Chapter 4). Simulation modelling was used to identify cropping practices conducive to longterm productivity and minimal drainage in the region. The O'Leary-Connor model (O'Leary and Connor 1996a,b) was appraised against observed measures (1993- 1998) of growth and yield of wheat, and rootzone soil-water balance under wheat and fallow (Chapter 5: Experiment I). Effects of crop rotation, stubble and tillage management on deep drainage of light (sandy loam) and heavy (clay) textured soils were then investigated by running the O'Leary-Connor model using 58 y of historical climatic data (Chapter 5: Experiment II). Field experimentation: The field experiment demonstrated effects of substituting mustard for fallowing. Aspects of water balance, growth and yield of FWP and MWP sequences were investigated in Chapter 2. Water limited crop production in each growing-season throughout the study. Rootzone soil-water conservation from fallowing in sequence FWP increased wheat growth, yield and water use under severe drought. By contrast, the data reveal that pea water relations and productivity was not influenced by crop sequence. Mustard growth was variable with low yields. Deep drainage was investigated (1993-1998) under FWP and MWP sequences by measuring changes in subsoil-water and by drainage lysimetry (Chapter 3). The former showed greater drainage of FWP (12 mm/y) compared to MWP (5 mm/y). Two major drainage events were confined to a specific phase of the FWP sequence (5.0 mm & 4.3 mm), illustrating the difficulty of reconciling drainage estimates by alternative approaches in a semi-arid environment over a relatively short period 5 y). Radiation interception by wheat, pea and mustard was investigated in Chapter 4. The fraction of intercepted PAR (f), canopy extinction coefficient and radiation-use efficiency were determined for each crop. Aridity resulted in incomplete canopy cover. Fallowing increased f of wheat under favourable (1996) and drought (1994) growing seasons. Estimates of extinction coefficient for wheat, pea and mustard were 0.82, 0.76 and 0.68, respectively. Estimated pre-anthesis radiation-use efficiency for wheat, pea and mustard were 1.75, 1.47 and 1.85 (g aboveground biomass/MJ intercepted PAR), respectively. Simulation modelling: The O'Leary-Connor model provided a good representation of wheat growth, and rootzone soil water (Chapter' 5: Experiment I), justifying use of the unadjusted model, as a tool for examination of water balance under agronomic scenarios in this study (Chapter 5: Experiment II). The investigation suggested greater soil-water conservation under fallowing compared to continuous cropping. Simulated grain yield responded to trends in soil water in accordance with water limitations imposed by the rainfed environment. Simulated drainage was episodic. Soil hydraulic properties and agronomic management influenced total drainage. Least drainage occurred on the heavy textured clay, reflecting soil-water holding capacity and water use associated with crop production. No direct relationships between drainage and rainfall were evident. Continuously cropped (WW) sequences drained less than fallow-wheat (FW). Fallow management influenced water storage and drainage. Stubble-retained zerotilled fallows conserved more soil water and subsequently had greatest drainage. Conventional tillage and stubble burning decreased drainage, but increased runoff and soil surface evaporation. On the lighter soil type, WW and FW drained ~6 % of years without stubble retention, but 10-70 % of years when stubble was retained, with a increase in drainage from 0.5 mm/y to 10-20 mm/y, respectively. By contrast, the heavier clay failed to drain without stubble, and drained in the range, 5-24 % of years when stubble was retained (range, 2-17 mm/y). Overall, fallowing reduced yield failure, but, in conjunction with stubble retention, increased episodic and total drainage on both soil types under the climatic conditions experienced in the Mallee. Conclusion: Outcomes of both field and simulation studies confirms that fallowing increases drainage (potential groundwater recharge). Although, non-fallow annual cropping sequences failed to provide a dry soil profile at sowing for prevention of drainage, especially in wet years. Strategies that use agronomic perennials to dewater subsoils prior to sowing require further investigation.
Microwave conditioning and drying of wood veneer

Wahyudi ( 2000)

Several aspects of microwave veneer drying are described. The final moisture content profiles and quality of two dried veneer thicknesses A and B (3 and 1.5 mm in thickness respectively) are determined. Veneer gluability of the two veneer thicknesses, dried by two different methods, are examined. The dimensional stability of veneer and plywood samples made from these dried veneers are also examined. Green weight per unit area was used as an indicator of moisture content during drying. A wide variation in final moisture content of dried veneer was found to be due to the presence of earlywood and latewood in veneer sample A and juvenile wood in veneer sample B. Green veneer sorting, based on water content per area or volume, green weight per area and percent saturation, can be used to improve drying performance. Statistical analysis indicates that the final veneer moisture content profiles estimated from green weight per unit area for two dried veneer thicknesses A and B dried by microwave, are not significantly different from those under conventional drying. However, the result indicates that microwave drying resulted in a higher degree of moisture content uniformity for both veneer thicknesses, whereas excessive drying occurred on the outer sections for both veneer thicknesses under conventional drying. A dark color was found in the dried veneer of both thicknesses under microwave drying compared to those of conventionally dried veneers. Statistically, both drying methods resulted in similar veneer quality, except microwave drying resulted in better veneer quality with respect to flatness, and has a low flatness ratio. Microwave dried veneer also had low percent shrinkage for both veneer thicknesses compared to conventionally dried veneer samples. Veneer gluability for veneer A is better than for veneer B, higher in the percentage of wood failures and greater glueline shear strength. Microwave drying resulted in better veneer gluability. Although microwave-dried plywood samples had a higher percentage of water absorption for both veneer thicknesses compared to conventional samples, they had lower percentage thickness swelling. In addition, the percent failure did not represent the glue bond quality of plywood samples.
Adoption of agronomic technologies by farmers

Konstantinidis, Jim ( 1999)
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.
Vegetative propagation of Acacia melanoxylon R. Br. through root cuttings

Summers, Jason ( 2000)

A method of vegetative propagation of Acacia melanoxylon using root cuttings was trialed to identify the best treatment combinations. Ten individual trees from three distinct provenances were selected. The other factors were pre-treatments including hormones and season of collection of root cuttings. Provenances were from near Canberra and the East Gippsland and the Otways region of Victoria. The different media trialed included a commercial propagation mix, sand, and a mixture of perlite and vermiculite. Five different pre-treatments were investigated to determine if they boosted the number of shoots produced from a root cutting. The whole trial was repeated over four seasons in one year. Results showed that the provenance varied significantly in the number of shoots produced from root cuttings. One medium (Burnley Mix) also gave significantly better results than the other two media. One of the pretreatments the hormone (IBA) retarded shoot growth significantly. Season of collection had the most significant impact on shoot production. Cuttings set in autumn produced more than twice as many shoots as the cuttings set in the other seasons. A histological investigation was undertaken to determine the origin of the shoots. It was found that the cells originated from the vascular cambium region of the root sections. This thesis has demonstrated that mature Acacia melanoxylon trees can be vegetatively propagated successfully and produce morphologically juvenile plants. The method if further refined could produce the consistent results required to allow commercial propagation of Acacia melanoxylon.

School of Agriculture, Food and Ecosystem Sciences - Theses

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