Testosterone secretion in mammals typically occurs in random pulses such that a single blood samp... more Testosterone secretion in mammals typically occurs in random pulses such that a single blood sample provides limited information on reproductive endocrine status. However, it has been shown in several species that an index of the prevailing testosterone biosynthetic capacity of the testes can be obtained by measuring the increase in circulating testosterone after injection of a GnRH agonist or human
The ability to predict the effects of ex- treme climatic variables on livestock is important in t... more The ability to predict the effects of ex- treme climatic variables on livestock is important in terms of welfare and performance. An index combining temperature and humidity (THI) has been used for more than 4 decades to assess heat stress in cattle. However, the THI does not include important climatic variables such as solar load and wind speed (WS, m/s).
The aim of this study was to investigate how a moderate increase in dietary meat content combined... more The aim of this study was to investigate how a moderate increase in dietary meat content combined (or not) with soluble fibre would influence protein digestion as well as digesta characteristics and flow. Four groups of pigs were fed Western-style diets (high-protein/high-fat) containing two types of barbecued red meat, one with and one without a wheat arabinoxylan-rich fraction. After 4 wk, digesta samples were collected from small and large intestinal sites and analyzed for protein, amino acids, dry matter, and acid-insoluble ash. Tissue samples were also collected from each site. Arabinoxylan consumption led to somewhat lower apparent protein digestibility within the small and large intestines as well as shorter mean retention times. This suggests that the lowered protein digestibility is due, at least partly, to shorter access time to digestive proteases and absorptive surfaces. Additionally, digesta mass was higher in pigs fed arabinoxylan while dry matter (%) was lower, indicating an increased digesta water-holding capacity due to the presence of a soluble dietary fiber. Data showed that solubilized wheat arabinoxylan provides potential health benefits through decreased protein digestibility, increased digesta mass, and reduced mean retention time, even for diets with a moderately higher protein content. These factors are associated with efficiency of digestion and satiety, both of which have implications for prevention of obesity and other health disorders.
ABSTRACT Effective management of any population involves decisions based on the levels of abundan... more ABSTRACT Effective management of any population involves decisions based on the levels of abundance at particular points in time. Hence the choice of an appropriate method to estimate abundance is critical. Deer are not native to Australia and are a declared pest in some states where their numbers must be controlled in environmentally sensitive areas. The aim of this research was to help Australian land managers choose between widely used methods to count deer. We compared population estimates or indices from: distance sampling, aerial surveys, spotlight counts, and faecal pellet counts. For each we estimated the labour input, cost, and precision. The coefficient of variation varied with method and time of year from 8.7 to 36.6%. Total labour input per sampling event varied from 11 to 136 h. Total costs of vehicles and equipment per sampling event varied from AU$913 to $2966. Overall, the spotlight method performed the best at our study site when comparing labour input, total cost and precision. However, choice of the most precise, cost effective method will be site specific and rely on information collected from a pilot study, We provide recommendations to help land managers choose between possible methods in various circumstances.
Postharvest flower abscission is an ethylene-mediated process that can reduce the marketability o... more Postharvest flower abscission is an ethylene-mediated process that can reduce the marketability of cut Chamelaucium Desf. (Myrtaceae) flowers. The sensitivity of 51 Chamelaucium cut flower genotypes to ethylene was evaluated. Sensitivity varied among genotypes both between and within different species and crosses. Chamelaucium uncinatum × Chamelaucium micranthum cv. ‘Sweet Georgia’ and C. uncinatum cvv. ‘Early Nir’, ‘Paddy’s Late’, ‘Purple Pride’, ‘CWA Pink’ and ‘Early Hard’ flowers were highly sensitive to ethylene. These genotypes shed 10% of their flowers in response to a 12h treatment with <0.01μll−1 ethylene at 20°C. In contrast, C. megalopetalum ‘Winter White’ and ‘Iceberg’ flowers were insensitive to ethylene even at 100μll−1 for 12h at 20°C. Sensitivity to ethylene varied between harvests during the flowering season and for the same genotypes harvested from different farms. Sensitivity of C. uncinatum cv. ‘Purple Pride’ flowers to treatment with 1μll−1 ethylene also decreased towards the end of vase life in association with slight dehydration. Variation in ethylene-induced abscission responses highlights the need to screen flowers from multiple harvests and varying growing conditions when assessing ethylene sensitivity. Screening genotypes for ethylene sensitivity should facilitate selection of Chamelaucium species with greater durability for export handling.
... of activity was recorded for grey kangaroos (Macropus giganteus) and assumed for red-neckedwa... more ... of activity was recorded for grey kangaroos (Macropus giganteus) and assumed for red-neckedwallabies (Macropus rufogriseus) at Wallaby Creek, northern ... Thanks to Dr Greg Baxter for discussions and reviews of the manuscript and also to Mr Ed Sharrock for assistance in the ...
Urban encroachment on dense, coastal koala populations has ensured that their management has rece... more Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 ~30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.
The aims of the present study were to examine the variability of testosterone secretion in the Vi... more The aims of the present study were to examine the variability of testosterone secretion in the Virginia Opossum over a 24 h period and to develop a testosterone stimulation test that would provide an index of the prevailing testosterone biosynthetic capacity of the testes; the latter was used to clinically evaluate the efficacy of a gonadotrophin-releasing hormone agonist contraceptive. Sexually-mature captive opossums (n = 12) located in Africam Safari (Mexico) sampled every 12 h over 24 h consistently showed basal (&lt;0.21 ng mL(-1)) blood testosterone concentrations. Intra-muscular injection of buserelin (2 microg mL(-1)) and human chorionic gonadotrophin (hCG; 1000 IU) resulted in an increase (P &lt; 0.05) of plasma testosterone concentrations with maximal concentrations (3.9 ng mL(-1) and 5.8 ng mL(-1) respectively) occurring 120 min after injection. Plasma testosterone declined relatively rapidly to basal concentrations after 240 min with hCG but remained elevated after the same period of time with buserelin. Male opossums treated with (n = 6) and without (n = 6) a controlled-release deslorelin implant (Suprelorin; 4.7 mg deslorelin) were evaluated over a 10-week period for changes in testosterone secretion (hCG stimulation test) and sperm production (spermatorrhea). At the end of this period, the animals were hemi-castrated and their relative testicular quantitative histology compared. Testosterone concentration decreased over the course of the study in both treated and control animals (P &lt; 0.0001) but there was no apparent effect of deslorelin on testosterone secretion, testicular histology (relative proportions of testicular cell types and seminiferous tubule diameter), or sperm production (presence of sperm in the cauda epididymis or urine).
The aim of the present study was to determine whether analogues of gonadotrophin-releasing hormon... more The aim of the present study was to determine whether analogues of gonadotrophin-releasing hormone (GnRH) could be used to both induce an acute testosterone response and suppress anterior pituitary function in male koalas, and induce a luteal phase in female koalas. Experiment 1 characterised the steroidogenic response of male koalas to administration of 30 microg (4.3 microg kg(-1)) natural-sequence GnRH. Intra-muscular injection of natural-sequence GnRH induced the release of LH and testosterone with peak concentrations at 30 min (3.7 +/- 1.9 ng mL(-1)) and 2 h (5.4 +/- 0.5 ng mL(-1)), respectively. In Experiment 2, a single injection of the GnRH antagonist acyline (100 microg (14.3 microg kg(-1)) or 500 microg (71.4 microg kg(-1))) did not influence the testosterone response to subsequent injections of natural-sequence GnRH. In Experiment 3, 4 microg (~0.67 microg kg(-1)) of the GnRH agonist buserelin induced a luteal phase in five female koalas based on a LH surge, secretion of progestogen, and a normal-length oestrous cycle. The findings have shown that (1) natural-sequence GnRH can be used to test gonadotroph cell function and determine the testosterone-secreting capacity of male koalas, (2) the GnRH antagonist, acyline, at the dose rates used, does not suppress the pituitary-testis axis in male koalas, and (3) the GnRH agonist, buserelin, induces a normal luteal phase in female koalas.
Koala sperm mitochondria were examined by cryomicroscopy using the fluorescent probe JC-1, which ... more Koala sperm mitochondria were examined by cryomicroscopy using the fluorescent probe JC-1, which distinguishes high (red) and low (green) mitochondrial membrane potential (MMP). At normal body temperature, approximately 70% of live and untreated spermatozoa exhibited high MMP whereas &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;3% of live untreated spermatozoa exhibited low potential. A third class, in which single midpieces contained mixed mitochondrial populations, was also detected. Heterogeneity was noted in the level of MMP between individual koalas, individual spermatozoa and even between mitochondrial gyres within single midpieces. MMP of the live sperm population was not significantly affected by glycerol but was suppressed by freezing and thawing treatments. After thawing, MMP declined significantly during rewarming, especially as the temperature increased from 5 to 35 degrees C. The distribution of the ganglioside GM1 was examined using fluorescent-labelled cholera toxin B. In fresh, untreated koala spermatozoa GM1 was detected on the head and midpiece, but not on the principal piece. No significant redistribution of GM1 was observed after chilling and cryotreatment. Phosphatidylserine translocation across the plasma membrane was examined using fluorescent-labelled annexin V. Few fresh spermatozoa exhibited phosphatidylserine translocation (approximately 1%); this was not increased by chilling or cryopreservation, thus implying that cryotreatment had little effect on plasma membrane lipid asymmetry.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Journal of the Science of Food and Agriculture, 2005
Solid phase microextraction (SPME) offers a solvent-free and less labour-intensive alternative to... more Solid phase microextraction (SPME) offers a solvent-free and less labour-intensive alternative to traditional flavour isolation techniques. In this instance, SPME was optimised for the extraction of 17 stale flavour volatiles (C3-11,13 methyl ketones and C4-10 saturated aldehydes) from the headspace of full-cream ultrahigh-temperature (UHT)-processed milk. A comparison of relative extraction efficiencies was made using three fibre coatings, three extraction times and three extraction temperatures. Linearity of calibration curves, limits of detection and repeatability (coefficients of variation) were also used in determining the optimum extraction conditions. A 2 cm fibre coating of 50/30 µm divinylbenzene/Carboxen/polydimethylsiloxane in conjunction with a 15 min extraction at 40 • C were chosen as the final optimum conditions. This method can be used as an objective tool for monitoring the flavour quality of UHT milk during storage.
Understanding P and N dynamics in manure-amended soil is essential for estimating the environment... more Understanding P and N dynamics in manure-amended soil is essential for estimating the environmental impact of manure utilization in land applications. A laboratory incubation study was conducted to assess, (i) the eff ect of feeding a standard Australian commercial diet, and diets modifi ed with phytase supplementation and reduced nonphytase phosphorus (NPP), on the concentrations of P and N (total and soluble) in the manure derived from layer hens (Gallus domesticus L.), and (ii) the change in water-soluble phoshorus (P WSP ) and mineral N (NH 4 -N and NO 3 -N) when used as a soil amendment, applied at rates equivalent to 200 kg ha -1 (200N) and 400 kg ha -1 (400N). Phytase supplementation increased %P WSP by 8 to 12% in the manures, regardless of the levels of NPP in the diets, and in the manure-amended soils by 27 to 30% at the 200N application rate, and up to 54% at the 400N rate. Phytase signifi cantly (P < 0.05) reduced total nitrogen (TN) content (by 12-31%) of the manures but generally produced greater nitrate accumulation in the manure-amended soils. Net nitrifi cation, which commenced 4 wk after incubation, was accompanied by a simultaneous decrease in soil pH (by one pH unit) and a concomitant decline in %P WSP . Th e decline in %P WSP was primarily attributed to P retention by the soil as it became more acidic. Th is study suggests that phytase addition not only reduces manure total N content, and increases watersoluble P, but its eff ects on manure total phosphorus (TP) and 2 mol L -1 KCl extractable mineral N is infl uenced by the NPP level in the diet.
Quantification of soil seed is an important tool for understanding vegetation dynamics. However, ... more Quantification of soil seed is an important tool for understanding vegetation dynamics. However, determining adequate sample sizes and sampling regimes is problematic. The literature reports highly variable sample sizes and regimes without any generally applicable standards appearing to emerge. This problem is exaggerated by the heterogeneous and patchy nature of arid and semi-arid environments. Species accumulation curves are commonly used
Downloaded from 2 13 14 ABSTRACT: The ability to predict effects of extreme climatic variables on... more Downloaded from 2 13 14 ABSTRACT: The ability to predict effects of extreme climatic variables on livestock is 15 important in terms of welfare and performance. An index combining temperature and humidity 16 (THI) has been used for over 4 decades to assess heat stress in cattle. However, the THI does not 17 include important climatic variables such as solar load and wind speed (WS; m/s). Likewise, it 18 does not include management factors (the effect of shade) or animal factors (genotype 19 differences). Over 8 summers a total of 11,669 Bos taurus steers, 2,344 Bos taurus crossbred 20 steers, 2,142 Bos taurus x Bos indicus steers, and 1,595 Bos indicus steers were used to develop 21 and test a heat load index for feedlot cattle. A new heat load index (HLI) incorporating black 22 Downloaded from 3
A 120-d feedlot study using 164 Angus steers (BW = 396.7 ± 7.0 kg) was undertaken in Queensland A... more A 120-d feedlot study using 164 Angus steers (BW = 396.7 ± 7.0 kg) was undertaken in Queensland Australia (24°84&#39; S, 149°78&#39; N) to determine the effect of shade on body temperature (T(B)) and performance. Cattle were allocated to 20 pens: 16 with an area of 144 m(2) (8 steers/pen) and 4 with an area of 168 m(2) (9 steers/pen). Treatments (10 pens/treatment) were unshaded (NS) vs. shaded (SH). Shade (3.3 m(2)/steer) was provided by 80% solar block shade cloth. Before the study (d -31), 63 steers were implanted (between the internal abdominal muscle and the peritoneum at the right side flank) with a T(B) transmitter. Within each pen, 3 steers had a T(B) transmitter. Individual T(B) was obtained every 30 min. The cattle were fed a feedlot diet and had ad libitum access to water. Water usage and DMI were recorded daily on a pen basis. Average daily gain and G:F were calculated on a pen basis. Climatic variables were obtained from an on-site weather station every 30 min. Individual panting scores (PS) were obtained daily at 0600, 1200, and 1600 h. From these, mean PS (MPS) were calculated for each pen. At slaughter (d 121), individual HCW, loin muscle area (LMA), rump fat depth (P8), 12th-rib fat depth, and marbling score were obtained. Mean T(B) was not affected (P &gt; 0.05) by treatment (SH = 39.58°C; NS = 39.60°C). However, during a 21-d heat wave when cattle were exposed to a mean ambient temperature (T(AM)) &gt; 30°C for 8 h each d (T(AM) between 0800 and 1800 h = 29.7°C, and 23.4°C between 1830 and 0730 h), the T(B) of SH steers (40.41 ± 0.10°C) was less (P &lt; 0.01) than the T(B) of NS steers (41.14 ± 0.10°C). During this period, pen-MPS were greater (P &lt; 0.05) for the NS cattle at all observation times. Over the first 6 d of the heat wave, MPS of NS steers at 1200 h was 2.47 (P &lt; 0.01) vs. 1.39 for SH steers. Hip height, DMI, ADG, and G:F were greater (P &lt; 0.05) for SH cattle. Exit BW (final BW) of SH steers (596.1 kg) was greater (P &lt; 0.05) when compared with NS steers (578.6 kg). During the heat wave, DMI was 51% less for NS steers and 39% less for SH steers when compared with the pre-heat wave period (P &lt; 0.01). The HCW of SH steers (315.4 ± 0.8 kg) was greater (P &lt; 0.05) than for NS steers (321.4 ± 0.8 kg). No treatment differences (P &gt; 0.05) were found for LMA, P8, or marbling score. Access to shade improved (P &lt; 0.05) ADG and G:F, increased HCW, and decreased MPS; however, shade did not completely eliminate the impact of high heat load.
Testosterone secretion in mammals typically occurs in random pulses such that a single blood samp... more Testosterone secretion in mammals typically occurs in random pulses such that a single blood sample provides limited information on reproductive endocrine status. However, it has been shown in several species that an index of the prevailing testosterone biosynthetic capacity of the testes can be obtained by measuring the increase in circulating testosterone after injection of a GnRH agonist or human
The ability to predict the effects of ex- treme climatic variables on livestock is important in t... more The ability to predict the effects of ex- treme climatic variables on livestock is important in terms of welfare and performance. An index combining temperature and humidity (THI) has been used for more than 4 decades to assess heat stress in cattle. However, the THI does not include important climatic variables such as solar load and wind speed (WS, m/s).
The aim of this study was to investigate how a moderate increase in dietary meat content combined... more The aim of this study was to investigate how a moderate increase in dietary meat content combined (or not) with soluble fibre would influence protein digestion as well as digesta characteristics and flow. Four groups of pigs were fed Western-style diets (high-protein/high-fat) containing two types of barbecued red meat, one with and one without a wheat arabinoxylan-rich fraction. After 4 wk, digesta samples were collected from small and large intestinal sites and analyzed for protein, amino acids, dry matter, and acid-insoluble ash. Tissue samples were also collected from each site. Arabinoxylan consumption led to somewhat lower apparent protein digestibility within the small and large intestines as well as shorter mean retention times. This suggests that the lowered protein digestibility is due, at least partly, to shorter access time to digestive proteases and absorptive surfaces. Additionally, digesta mass was higher in pigs fed arabinoxylan while dry matter (%) was lower, indicating an increased digesta water-holding capacity due to the presence of a soluble dietary fiber. Data showed that solubilized wheat arabinoxylan provides potential health benefits through decreased protein digestibility, increased digesta mass, and reduced mean retention time, even for diets with a moderately higher protein content. These factors are associated with efficiency of digestion and satiety, both of which have implications for prevention of obesity and other health disorders.
ABSTRACT Effective management of any population involves decisions based on the levels of abundan... more ABSTRACT Effective management of any population involves decisions based on the levels of abundance at particular points in time. Hence the choice of an appropriate method to estimate abundance is critical. Deer are not native to Australia and are a declared pest in some states where their numbers must be controlled in environmentally sensitive areas. The aim of this research was to help Australian land managers choose between widely used methods to count deer. We compared population estimates or indices from: distance sampling, aerial surveys, spotlight counts, and faecal pellet counts. For each we estimated the labour input, cost, and precision. The coefficient of variation varied with method and time of year from 8.7 to 36.6%. Total labour input per sampling event varied from 11 to 136 h. Total costs of vehicles and equipment per sampling event varied from AU$913 to $2966. Overall, the spotlight method performed the best at our study site when comparing labour input, total cost and precision. However, choice of the most precise, cost effective method will be site specific and rely on information collected from a pilot study, We provide recommendations to help land managers choose between possible methods in various circumstances.
Postharvest flower abscission is an ethylene-mediated process that can reduce the marketability o... more Postharvest flower abscission is an ethylene-mediated process that can reduce the marketability of cut Chamelaucium Desf. (Myrtaceae) flowers. The sensitivity of 51 Chamelaucium cut flower genotypes to ethylene was evaluated. Sensitivity varied among genotypes both between and within different species and crosses. Chamelaucium uncinatum × Chamelaucium micranthum cv. ‘Sweet Georgia’ and C. uncinatum cvv. ‘Early Nir’, ‘Paddy’s Late’, ‘Purple Pride’, ‘CWA Pink’ and ‘Early Hard’ flowers were highly sensitive to ethylene. These genotypes shed 10% of their flowers in response to a 12h treatment with <0.01μll−1 ethylene at 20°C. In contrast, C. megalopetalum ‘Winter White’ and ‘Iceberg’ flowers were insensitive to ethylene even at 100μll−1 for 12h at 20°C. Sensitivity to ethylene varied between harvests during the flowering season and for the same genotypes harvested from different farms. Sensitivity of C. uncinatum cv. ‘Purple Pride’ flowers to treatment with 1μll−1 ethylene also decreased towards the end of vase life in association with slight dehydration. Variation in ethylene-induced abscission responses highlights the need to screen flowers from multiple harvests and varying growing conditions when assessing ethylene sensitivity. Screening genotypes for ethylene sensitivity should facilitate selection of Chamelaucium species with greater durability for export handling.
... of activity was recorded for grey kangaroos (Macropus giganteus) and assumed for red-neckedwa... more ... of activity was recorded for grey kangaroos (Macropus giganteus) and assumed for red-neckedwallabies (Macropus rufogriseus) at Wallaby Creek, northern ... Thanks to Dr Greg Baxter for discussions and reviews of the manuscript and also to Mr Ed Sharrock for assistance in the ...
Urban encroachment on dense, coastal koala populations has ensured that their management has rece... more Urban encroachment on dense, coastal koala populations has ensured that their management has received increasing government and public attention. The recently developed National Koala Conservation Strategy calls for maintenance of viable populations in the wild. Yet the success of this, and other, conservation initiatives is hampered by lack of reliable and generally accepted national and regional population estimates. In this paper we address this problem in a potentially large, but poorly studied, regional population in the State that is likely to have the largest wild populations. We draw on findings from previous reports in this series and apply the faecal standing-crop method (FSCM) to derive a regional estimate of more than 59 000 individuals. Validation trials in riverine communities showed that estimates of animal density obtained from the FSCM and direct observation were in close agreement. Bootstrapping and Monte Carlo simulations were used to obtain variance estimates for our population estimates in different vegetation associations across the region. The most favoured habitat was riverine vegetation, which covered only 0.9% of the region but supported 45% of the koalas. We also estimated that between 1969 and 1995 ~30% of the native vegetation associations that are considered as potential koala habitat were cleared, leading to a decline of perhaps 10% in koala numbers. Management of this large regional population has significant implications for the national conservation of the species: the continued viability of this population is critically dependent on the retention and management of riverine and residual vegetation communities, and future vegetation-management guidelines should be cognisant of the potential impacts of clearing even small areas of critical habitat. We also highlight eight management implications.
The aims of the present study were to examine the variability of testosterone secretion in the Vi... more The aims of the present study were to examine the variability of testosterone secretion in the Virginia Opossum over a 24 h period and to develop a testosterone stimulation test that would provide an index of the prevailing testosterone biosynthetic capacity of the testes; the latter was used to clinically evaluate the efficacy of a gonadotrophin-releasing hormone agonist contraceptive. Sexually-mature captive opossums (n = 12) located in Africam Safari (Mexico) sampled every 12 h over 24 h consistently showed basal (&lt;0.21 ng mL(-1)) blood testosterone concentrations. Intra-muscular injection of buserelin (2 microg mL(-1)) and human chorionic gonadotrophin (hCG; 1000 IU) resulted in an increase (P &lt; 0.05) of plasma testosterone concentrations with maximal concentrations (3.9 ng mL(-1) and 5.8 ng mL(-1) respectively) occurring 120 min after injection. Plasma testosterone declined relatively rapidly to basal concentrations after 240 min with hCG but remained elevated after the same period of time with buserelin. Male opossums treated with (n = 6) and without (n = 6) a controlled-release deslorelin implant (Suprelorin; 4.7 mg deslorelin) were evaluated over a 10-week period for changes in testosterone secretion (hCG stimulation test) and sperm production (spermatorrhea). At the end of this period, the animals were hemi-castrated and their relative testicular quantitative histology compared. Testosterone concentration decreased over the course of the study in both treated and control animals (P &lt; 0.0001) but there was no apparent effect of deslorelin on testosterone secretion, testicular histology (relative proportions of testicular cell types and seminiferous tubule diameter), or sperm production (presence of sperm in the cauda epididymis or urine).
The aim of the present study was to determine whether analogues of gonadotrophin-releasing hormon... more The aim of the present study was to determine whether analogues of gonadotrophin-releasing hormone (GnRH) could be used to both induce an acute testosterone response and suppress anterior pituitary function in male koalas, and induce a luteal phase in female koalas. Experiment 1 characterised the steroidogenic response of male koalas to administration of 30 microg (4.3 microg kg(-1)) natural-sequence GnRH. Intra-muscular injection of natural-sequence GnRH induced the release of LH and testosterone with peak concentrations at 30 min (3.7 +/- 1.9 ng mL(-1)) and 2 h (5.4 +/- 0.5 ng mL(-1)), respectively. In Experiment 2, a single injection of the GnRH antagonist acyline (100 microg (14.3 microg kg(-1)) or 500 microg (71.4 microg kg(-1))) did not influence the testosterone response to subsequent injections of natural-sequence GnRH. In Experiment 3, 4 microg (~0.67 microg kg(-1)) of the GnRH agonist buserelin induced a luteal phase in five female koalas based on a LH surge, secretion of progestogen, and a normal-length oestrous cycle. The findings have shown that (1) natural-sequence GnRH can be used to test gonadotroph cell function and determine the testosterone-secreting capacity of male koalas, (2) the GnRH antagonist, acyline, at the dose rates used, does not suppress the pituitary-testis axis in male koalas, and (3) the GnRH agonist, buserelin, induces a normal luteal phase in female koalas.
Koala sperm mitochondria were examined by cryomicroscopy using the fluorescent probe JC-1, which ... more Koala sperm mitochondria were examined by cryomicroscopy using the fluorescent probe JC-1, which distinguishes high (red) and low (green) mitochondrial membrane potential (MMP). At normal body temperature, approximately 70% of live and untreated spermatozoa exhibited high MMP whereas &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;3% of live untreated spermatozoa exhibited low potential. A third class, in which single midpieces contained mixed mitochondrial populations, was also detected. Heterogeneity was noted in the level of MMP between individual koalas, individual spermatozoa and even between mitochondrial gyres within single midpieces. MMP of the live sperm population was not significantly affected by glycerol but was suppressed by freezing and thawing treatments. After thawing, MMP declined significantly during rewarming, especially as the temperature increased from 5 to 35 degrees C. The distribution of the ganglioside GM1 was examined using fluorescent-labelled cholera toxin B. In fresh, untreated koala spermatozoa GM1 was detected on the head and midpiece, but not on the principal piece. No significant redistribution of GM1 was observed after chilling and cryotreatment. Phosphatidylserine translocation across the plasma membrane was examined using fluorescent-labelled annexin V. Few fresh spermatozoa exhibited phosphatidylserine translocation (approximately 1%); this was not increased by chilling or cryopreservation, thus implying that cryotreatment had little effect on plasma membrane lipid asymmetry.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Journal of the Science of Food and Agriculture, 2005
Solid phase microextraction (SPME) offers a solvent-free and less labour-intensive alternative to... more Solid phase microextraction (SPME) offers a solvent-free and less labour-intensive alternative to traditional flavour isolation techniques. In this instance, SPME was optimised for the extraction of 17 stale flavour volatiles (C3-11,13 methyl ketones and C4-10 saturated aldehydes) from the headspace of full-cream ultrahigh-temperature (UHT)-processed milk. A comparison of relative extraction efficiencies was made using three fibre coatings, three extraction times and three extraction temperatures. Linearity of calibration curves, limits of detection and repeatability (coefficients of variation) were also used in determining the optimum extraction conditions. A 2 cm fibre coating of 50/30 µm divinylbenzene/Carboxen/polydimethylsiloxane in conjunction with a 15 min extraction at 40 • C were chosen as the final optimum conditions. This method can be used as an objective tool for monitoring the flavour quality of UHT milk during storage.
Understanding P and N dynamics in manure-amended soil is essential for estimating the environment... more Understanding P and N dynamics in manure-amended soil is essential for estimating the environmental impact of manure utilization in land applications. A laboratory incubation study was conducted to assess, (i) the eff ect of feeding a standard Australian commercial diet, and diets modifi ed with phytase supplementation and reduced nonphytase phosphorus (NPP), on the concentrations of P and N (total and soluble) in the manure derived from layer hens (Gallus domesticus L.), and (ii) the change in water-soluble phoshorus (P WSP ) and mineral N (NH 4 -N and NO 3 -N) when used as a soil amendment, applied at rates equivalent to 200 kg ha -1 (200N) and 400 kg ha -1 (400N). Phytase supplementation increased %P WSP by 8 to 12% in the manures, regardless of the levels of NPP in the diets, and in the manure-amended soils by 27 to 30% at the 200N application rate, and up to 54% at the 400N rate. Phytase signifi cantly (P < 0.05) reduced total nitrogen (TN) content (by 12-31%) of the manures but generally produced greater nitrate accumulation in the manure-amended soils. Net nitrifi cation, which commenced 4 wk after incubation, was accompanied by a simultaneous decrease in soil pH (by one pH unit) and a concomitant decline in %P WSP . Th e decline in %P WSP was primarily attributed to P retention by the soil as it became more acidic. Th is study suggests that phytase addition not only reduces manure total N content, and increases watersoluble P, but its eff ects on manure total phosphorus (TP) and 2 mol L -1 KCl extractable mineral N is infl uenced by the NPP level in the diet.
Quantification of soil seed is an important tool for understanding vegetation dynamics. However, ... more Quantification of soil seed is an important tool for understanding vegetation dynamics. However, determining adequate sample sizes and sampling regimes is problematic. The literature reports highly variable sample sizes and regimes without any generally applicable standards appearing to emerge. This problem is exaggerated by the heterogeneous and patchy nature of arid and semi-arid environments. Species accumulation curves are commonly used
Downloaded from 2 13 14 ABSTRACT: The ability to predict effects of extreme climatic variables on... more Downloaded from 2 13 14 ABSTRACT: The ability to predict effects of extreme climatic variables on livestock is 15 important in terms of welfare and performance. An index combining temperature and humidity 16 (THI) has been used for over 4 decades to assess heat stress in cattle. However, the THI does not 17 include important climatic variables such as solar load and wind speed (WS; m/s). Likewise, it 18 does not include management factors (the effect of shade) or animal factors (genotype 19 differences). Over 8 summers a total of 11,669 Bos taurus steers, 2,344 Bos taurus crossbred 20 steers, 2,142 Bos taurus x Bos indicus steers, and 1,595 Bos indicus steers were used to develop 21 and test a heat load index for feedlot cattle. A new heat load index (HLI) incorporating black 22 Downloaded from 3
A 120-d feedlot study using 164 Angus steers (BW = 396.7 ± 7.0 kg) was undertaken in Queensland A... more A 120-d feedlot study using 164 Angus steers (BW = 396.7 ± 7.0 kg) was undertaken in Queensland Australia (24°84&#39; S, 149°78&#39; N) to determine the effect of shade on body temperature (T(B)) and performance. Cattle were allocated to 20 pens: 16 with an area of 144 m(2) (8 steers/pen) and 4 with an area of 168 m(2) (9 steers/pen). Treatments (10 pens/treatment) were unshaded (NS) vs. shaded (SH). Shade (3.3 m(2)/steer) was provided by 80% solar block shade cloth. Before the study (d -31), 63 steers were implanted (between the internal abdominal muscle and the peritoneum at the right side flank) with a T(B) transmitter. Within each pen, 3 steers had a T(B) transmitter. Individual T(B) was obtained every 30 min. The cattle were fed a feedlot diet and had ad libitum access to water. Water usage and DMI were recorded daily on a pen basis. Average daily gain and G:F were calculated on a pen basis. Climatic variables were obtained from an on-site weather station every 30 min. Individual panting scores (PS) were obtained daily at 0600, 1200, and 1600 h. From these, mean PS (MPS) were calculated for each pen. At slaughter (d 121), individual HCW, loin muscle area (LMA), rump fat depth (P8), 12th-rib fat depth, and marbling score were obtained. Mean T(B) was not affected (P &gt; 0.05) by treatment (SH = 39.58°C; NS = 39.60°C). However, during a 21-d heat wave when cattle were exposed to a mean ambient temperature (T(AM)) &gt; 30°C for 8 h each d (T(AM) between 0800 and 1800 h = 29.7°C, and 23.4°C between 1830 and 0730 h), the T(B) of SH steers (40.41 ± 0.10°C) was less (P &lt; 0.01) than the T(B) of NS steers (41.14 ± 0.10°C). During this period, pen-MPS were greater (P &lt; 0.05) for the NS cattle at all observation times. Over the first 6 d of the heat wave, MPS of NS steers at 1200 h was 2.47 (P &lt; 0.01) vs. 1.39 for SH steers. Hip height, DMI, ADG, and G:F were greater (P &lt; 0.05) for SH cattle. Exit BW (final BW) of SH steers (596.1 kg) was greater (P &lt; 0.05) when compared with NS steers (578.6 kg). During the heat wave, DMI was 51% less for NS steers and 39% less for SH steers when compared with the pre-heat wave period (P &lt; 0.01). The HCW of SH steers (315.4 ± 0.8 kg) was greater (P &lt; 0.05) than for NS steers (321.4 ± 0.8 kg). No treatment differences (P &gt; 0.05) were found for LMA, P8, or marbling score. Access to shade improved (P &lt; 0.05) ADG and G:F, increased HCW, and decreased MPS; however, shade did not completely eliminate the impact of high heat load.
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