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Context In some regions of Australia, the Australian sheep blowfly (Lucilia cuprina) is resistant to some of the pesticides used to control flystrike in sheep. Few pesticide groups are available, so it is important to delay or prevent any increase in resistance. Aims This study examined some of the assumptions in a previously developed model of pesticide resistance and tested the use of pesticide rotations as a means of limiting blowfly resistance to pesticides. Methods A model of sheep blowfly pesticide resistance was added to a previous model of sheep blowfly strike, to allow simulation of a range of pesticide management options for control of flystrike in sheep that might avoid increasing pesticide resistance. Key results The model requires some assumptions of settings that are uncertain, but the effects are not sensitive to a wide range of values for these settings. Resistance may not be obvious for some years after a new product is introduced, but once it has been detected, the frequency of resistance genes will increase rapidly if use of the same pesticide continues. The use of different pesticide groups each year is preferable to continuous use of the same product, but this risks losing efficacy of multiple products rather than one product at a time. However, rotations do provide a longer period of good protection from flystrike before all products used in the rotation fail. The number of years of successful protection against flystrike is extended if there is a fitness disadvantage for resistance to the products used. Conclusions The model may be useful for examining interactions between genes for resistance to different pesticides and the effect of non-chemical methods of control of flystrike, to extend the useful life of the current range of pesticides. Implications By the time resistance is detected on a farm, the level of resistance is high and will increase rapidly if the same pesticides continue to be used. Other non-pesticide methods such as breeding sheep for resistance to flystrike may be long-term solutions where resistance has reduced pesticide protection.

In on-farm animal welfare assessment schemes mortality is a commonly used measure to assess welfare states, as well as to ascertain the effectiveness of different management strategies. While decreases in welfare and mortality are linked it is likely that monitoring and measuring the factors that influence mortality will be key in using this relationship to improve animal welfare. Therefore, this paper aimed to identify various factors that influence mortality in adult ewes. Once identified these factors may then be suitable for inclusion in an on-farm welfare assessment, or for a broader framework designed to manage risks to mortality. The data used in this analysis was collected on an Australian sheep flock from 2007 to 2010, and focused on identifying variables that increase the risk of mortality of ewes from weaning to a mature age (∼ 660 days). Given that neither mortality, nor the factors affecting it, were routinely recorded in this data set an individual ewe was considered dead when she was identified as missing at consecutive regular husbandry events. Analysis of the data indicated that sire (P

Virtual fencing contains and controls grazing cattle using sensory cues rather than physical fences. The technology comprises a neckband-mounted device that delivers an audio cue when the animal nears a virtual boundary that has been set via global positioning system, followed by an electrical stimulus if it walks beyond the boundary. Virtual fencing has successfully been used to intensively graze cattle using a simple virtual front-fence, but a more complex intensive grazing system comprising moving virtual front and back-fences has not been assessed. We studied the effectiveness of virtual fencing technology to contain groups of Angus heifers within grazing cells defined by semi-permanent electric side-fences and virtual front and back-fences, compared to groups of heifers contained in cells defined only by electric fencing. Four groups of 10 Angus heifers were randomly allocated to a “control” (grazed with a conventional electric front and back-fence, n = 2 groups) or “virtual fence” treatment (grazed with a virtual front and back-fence, n = 2 groups). The groups of heifers grazed four adjacent experimental paddocks that were established using TechnoGrazing™ infrastructure. An estimated 9.5 kg pasture DM/heifer.day was offered in each of three 3 day allocations (9 day study period). Data collected include cues delivered by the neckbands, time beyond the virtual boundaries, pasture consumption for each allocation and heifer live weight changes over the study period. The virtual front and back-fences successfully contained one group of heifers in their grazing cell, but the second group of heifers spent an increasing amount of time in the exclusion zone during the second and third allocations and consequently received an increasing number of audio and electrical stimuli. There were no effects of electric or virtual-fence treatment on live weight change or pasture utilization. By grazing heifers in adjacent paddocks our experimental design may have produced a motivation for some heifers to cross the virtual boundary to regain close contact with familiar conspecifics. Despite this, valuable learnings were gained from this study. Most notably, virtual fencing should not be used to manage cattle that have close visual contact to other mobs. We conclude that the successful application of virtual fencing technology needs to accommodate the natural behaviors of cattle.

We investigated how individuality and lameness altered social organisation by assessing food-directed movement patterns in sheep. One hundred and ninety-six mature Merino ewes were walked in 16 different runs around a 1.1 km track following a food source. Flock position and lameness were measured and temperament was assessed using an Isolation Box Test. The mean value for the correlations of position between a run and the run preceding it was r = 0.55 ± SEM 0.03. All correlations between runs were positive (r = 0.08-0.76) and all but two were statistically significant (P 0.05). The weakest and least statistically significant correlations were for run 14: where all 16 runs were conducted approximately 3 times a week, except with an interval of 20 weeks between runs 13 and 14. Additionally, there were differences in overall positions for a lame versus a non-lame individual (all P 0.05) with lame sheep being further back in position when compared to their non-lame mean positions. These results indicate the movement patterns, as measured by flock position during a food-directed forced movement order are relatively stable provided tests occur frequently, possibly on a bi-weekly basis. However, further work will be required to better account for individual animal variation.

Context Mulesing provides a high degree of protection against beech strike, but wool producers need to be able to predict the level of risk of flystrike if they cease mulesing. Aims To use data from trials of mulesed and unmulesed sheep to estimate the distribution of adult breech scores (wrinkle, breech cover and dag) from mean flock values, and use those scores to estimate the risk of breech strike in Merino sheep flocks. Methods Breech scores and breech strike from flocks with comparable mulesed and unmulesed sheep were examined using logistic functions to relate breech scores in mulesed sheep to those in unmulesed sheep, and to estimate the risk of breech strike in sheep for any given combination of breech scores. Key results Functions are given to estimate whole flock adult breech wrinkle and breech cover using combinations of the breech traits that are available. Unmulesed Merino sheep have a 6-fold increased risk of breech strike compared with mulesed sheep under the same conditions. There were increased relative risks of breech strike of 2.0 for each unit increase in dag score, 2.2 for each unit increase in breech wrinkle score and 1.7 for each unit increase in breech cover score. Mulesing reduced each of these risk factors, but had an additional 3.2-fold benefit independent of these factors. Adult breech wrinkle was most reliably estimated from neck wrinkle or from marking breech wrinkle (before mulesing). Breech cover was estimated from face cover, or from marking breech cover. The risk of breech strike if adult sheep were to be left unmulesed in a commercial flock was predicted using a centred log ratio transformation to estimate the distribution of dag scores in the unmulesed sheep, given the actual distribution in the mulesed flock. If the distribution was not known, then the mean dag score of the mulesed sheep could be used to estimate the distribution of dag scores in unmulesed sheep using a 2/3 power function to transform the mean dag score. Conclusions A flock of unmulesed sheep would need to lower breech wrinkle, breech cover and dag scores by 0.5 for each score to achieve a comparable level of risk of breech strike in mulesed sheep. Implications The use of the model will allow wool producers to selectively breed for sheep with lower risk of breech strike, while continuing to mules the sheep as long as it is necessary to do so. They will be able to estimate what the risk of strike would be if they cease mulesing, due to the proportion of sheep with potentially high wrinkle score, high breech cover or high dag scores at any stage of their breeding program.

Free-range laying hen systems provide individuals a choice between indoor and outdoor areas where range use may be socially influenced. This study used radio-frequency identification technology to track the ranging of individually-tagged hens housed in six experimental free-range pens from 28 to 38 weeks of age (46&ndash, 50 hens/pen). All daily visits to the range were used to study group behaviour. Results showed that 67.6% (SD = 5.0%) of all hen movements through the pop-holes outdoors or indoors were following the movement of another hen (&lsquo, pop-hole-following&rsquo, ) compared to only 50.5% of movements in simulated random data. The percentage overlap in time that all combinations of hen pairs within each pen spent simultaneously outdoors or indoors showed a median value of overlap greater than the 90th percentile of random data. Pens housing hens that had been provided variable enrichments from 4 to 21 days (n = 3 pens) showed higher &lsquo, behaviour and a higher percentage of hen-pair association compared to hens reared in non-enriched conditions (n = 3 pens). These results show that birds in each free-range pen were primarily a cohesive flock and early enrichment improved this social cohesiveness. These results have implications for understanding free-range flock-level behaviour.

Objective: This study used a model of the development of wool damage caused by lice in long wool to examine the conditions under which treatment of the sheep is advisable on an economic basis. Methods: The model uses the proportion of a flock showing visible signs of rubbing and the number of days until the next shearing to compare the cost of treatment (product plus labour) with production losses because of the reduction in wool value caused by lice. From the model output, guidelines are provided to inform producers of the most cost-effective option for lice control. Results: Under normal conditions, if there are any signs of rubbing ≥140 days before shearing, then treatment was the best option. If signs of wool damage are not observed until there are ≤70 days before shearing, then the most cost-effective option is to not treat at all. Between these two periods, the time period in which not treating is the most cost-effective option decreases as the number of sheep visibly affected by lice increases. At higher wool values (A$70/head vs A$35), the option to treat is brought forward approximately 25 days, whereas at a low wool value (A$17.50/head) the period in which no treatment is the most cost-effective is extended by approximately 25 days. Treating only the visibly affected sheep is the best option only for a very short time for all wool values and treatment costs. Conclusion: The model provides guidelines for control of lice in long wool to minimise the net cost of infestation and limit unnecessary pesticide use.

In eight Australian Merino and crossbred sheep flocks, all lamb deaths were recorded, together with the corresponding weather before and after each case. Deaths on the day of birth were not strongly associated with a high chill index, but deaths in the following 3 days were significantly increased by a high chill index in the period between birth and the relevant day. Losses were greater for multiple-born lambs than singles under all conditions, but there was not a significant interaction of chill index with multiple births. A model is given for the risk of loss of lambs after birth, on the basis of birthweight, sex of the lamb, multiple birth and chill index for the ewe before birth and the lamb after birth. However, some of this information is not available until after the lamb is born, so a model is also given using only information available shortly before birth, namely, the expected chill index and whether pregnancy scanning has identified single or multiple lambs.

This study reports a method of measuring sheep activity in confinement based on recording movement of sheep during weighing. The aim was to show that an algorithm to analyse continuous weight records could be used to measure activity quickly and efficiently using commercial weighing equipment and that this measurement is related to animal productivity, specifically liveweight. A prototype method required magnetic switches on the weighing crate to record gate positioning and enclosure of the animal, with data analysis subsequent to the completion of weighing. The method reported here does not require additional equipment, instead using a computer program to analyse weights in real-time to record the degree of sheep movement. The result is summarised as the coefficient of variation of the weight over a period of 8–20 s and reported as an activity score. The real-time method had a higher repeatability (P < 0.05) than the prototype method and gave a stronger association with liveweight with heavier lambs and heavier young sheep being less active under confinement at 6 months and 18 months, respectively (P < 0.05). These findings indicate that a simple system could be developed enabling real-time reporting of activity scores during normal weighing.

In eight closely recorded Australian Merino and crossbred sheep flocks, all lamb deaths were examined and the cause of deaths identified if possible. Dystocia was identified as one of the major causes of lamb death and this study examined factors that could be used to identify ewes at high risk of dystocia, either to avoid dystocia or to assist with early intervention where possible. Dystocia was least common in lambs of ~4.8 kg, but there was a higher risk at both lower and higher birthweights. Dystocia with both low and high birthweight was more common in older ewes, ranging from negligible low birthweight dystocia in ewes less than 3 years old at lambing, to 5% in older ewes. Low birthweight dystocia increased with increasing litter size, with 40% dystocia in ewes at least 4 years of age with triplets. In contrast, high birthweight dystocia was not affected by litter size. A previous record of low birthweight dystocia was a risk factor for future low birthweight dystocia, but the same relationship was not observed for high birthweight dystocia. A high lambing ease score (difficult birth) with high birthweight was a risk factor for future high birthweight dystocia, but this was not the case for low birthweight dystocia. These differences between the risk factors for low and high birthweight dystocia suggest that they have different causes. High ewe liveweight and condition score during pregnancy may be additional indicators of the risk of dystocia, particularly for ewes with high liveweight in the first 60 days of pregnancy. For most ewes dystocia was difficult to predict, but there was a small proportion of ewes with a very high risk of dystocia and if these could be identified in advance they could be monitored much more closely than the rest of the flock.

In eight well-managed Australian Merino and crossbred sheep flocks the adult ewes were monitored frequently for flystrike. Occurrences of flystrike and severity of strike scores were recorded, whereas bodyweights and condition scores were recorded regularly across two wool production and reproduction cycles. In these unmulesed flocks, 17% of Merino and 5% of crossbred ewes were struck, with 2% of those struck dead within 7 days of detection of the strike. For those adult ewes that survived the immediate period of the strike, the rate of loss over the following year was slightly greater than for ewes that were never struck, particularly for those with a high severity strike. Flystrike also contributed to losses of up to 2.7 (Merino ewes) and 5.2 (crossbred ewes) kg of bodyweight, and 0.3 condition score units at the time of the strike. Bodyweights were still 2 kg lower by 3 months after the strike occurred for Merinos, although condition scores returned to average levels. For ewes struck between mating and lambing, flystrike was associated with significant losses of lambs. Flystrike at severity level 1 (light) had only minor effects on wool production, but severity score 3 (heavy) reduced clean fleece weight.

The significance of brushtail possum, Trichosurus vulpecula Kerr (Diprotodontia: Phalangeridae) carcasses to the succession and production of Diptera species and its relevance to fly strike management in Tasmania, Australia was examined. Calliphora stygia (Fabricius), Lucilia sericata (Meigen) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) were found to be the most abundant and Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) always the least abundant (< 1%) of the putative primary fly invading species to emerge. Carcasses that were left for up to 15 days in the field before being exposed to flies for 2 days also acted as breeding sites for large numbers of all primary fly species, with the exception of L. cuprina. Ordination analysis revealed no relationship between possum carcasses according to their length of exposure but did show significant negative associations between the number of putative secondary invaders (Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae), Chrysomya varipes (Macquart) (Diptera: Calliphoridae) and putative tertiary flies (Hydrotaea rostrata Robineau-Desvoidy (Diptera: Muscidae)) to the number of C. vicina or C. stygia to emerge. There was enormous variability in the numbers of secondary/tertiary fly species to emerge from carcasses (0-11 450) that negatively correlated with the proportion of all flies to emerge that were primary, and with the mean size of adult L. sericata. Although carcass temperatures, especially those with a large larval population, were elevated, this did not appear to result in significant pre-adult fly mortality. The most important primary fly strike species L. cuprina was only found in insignificant numbers, whereas three other members of the fly strike fauna C. stygia, L. sericata and Ch. rufifacies did use possum carrion as an important breeding resource, but left implications for fly strike management inconclusive.

A model of lice management systems was used to investigate the potential benefits of improved fencing against straying sheep, used in conjunction with other management options for lice control. The impact of combined strategies was simulated over a 20-year period. Management options included in the model were: lice eradication rate, lice detection, intervention level, improved fencing to reduce straying sheep, and biosecurity of purchased sheep. The modelling found it was cost-effective to improve fences for an initial average cost of $20 000/property if the number of properties from which strays could enter was reduced by ≥40%, but for average Australian properties this represents less than 20% of the boundary replaced. In order for fencing to be a cost-effective part of lice management, the fencing must target sections of boundary fence that will provide the greatest protection from contact with neighbouring flocks. The model showed that improved biosecurity against straying sheep combined well with improved eradication rates. However, biosecurity for purchased sheep may be the most cost-effective option.

Using a previously developed predictive model, three different management practices were examined in combination with post-shearing chemical treatments for lice, to determine which combinations could provide cost-effective reductions in lice prevalence over a 20-year period. The model included nine sheep production regions across Australia, all of which have different regional flock prevalence of lice and mean numbers of sheep/property. The lice prevalence model simulated the effects of four management options on Australian lice prevalence and on financial return (expressed as net present value) over a 20-year period. Management options modelled in this study were: treatment for eradication, inspection for lice detection, intervention level, and biosecurity of purchased sheep. The costs and benefits of these management options were calculated on the basis of published data or standard industry costs. Combinations of eradication achieved through treatment and biosecurity of purchased sheep provided the greatest modelled reductions in Australian flock lice prevalence at the lowest cost. With current management practices, lice prevalence was estimated as 16.3% of Australian properties infested and lice costs were estimated at 902 cents per sheep over 20 years. The model estimated that with appropriate management, lice prevalence could be reduced to less than 1.5% of properties infested and costs could be halved to 435 cents per sheep over 20 years. With further development, the modelling described herein offers potential guidance for Australian sheep producers in selecting the most effective and cost-efficient combination of management strategies to reduce lice infestation.

Merino sheep infested with lice (Bovicola ovis) and with 8 months’ wool were hand jetted with a commercial spinosad formulation or treated with an α-cypermethrin backline product to examine the effect of long wool treatment on lice numbers and wool damage, relative to untreated controls. Mean lice numbers were reduced significantly (P < 0.05) by treatment and then remained relatively constant until shearing 20 weeks later. Treatment with either product resulted in significant improvements in mean clean and greasy wool cut, yield, staple length, both visually assessed and measured colour, and the proportion of fleeces classed into the main fleece line. There was no significant difference between the two treatments in either efficacy in reducing louse numbers or on production characters. Wool rub score and cotting assessed on the sheep increased slightly after treatment and then did not change until shearing whereas both scores increased significantly in the untreated group. There was a strong relationship between the visual rub score and the loss of wool at shearing, indicating that rub score can be a good predictor of lice-induced reduction in fleece weights.

A model of sheep lice management incorporating different assumed levels of lice prevalence in different regions of Australia was used to determine the conditions under which it would be cost-effective to treat sheep for lice at shearing when no lice had been detected. The probability that a flock might be infested was calculated from the probability that the previous treatment had failed to eradicate lice, purchased sheep may have introduced lice, or lice may have entered on straying sheep. The model showed that a flock should be treated if the probability of infestation is greater than 10%. It was projected that acceptance of a risk level greater than 10% would reduce treatment of flocks where no lice were present, thus reducing treatment costs. This higher risk level, however, would increase the proportion of louse-infested flocks that remained untreated, resulting in increased direct lice costs and an increase in the regional prevalence of lice, but little overall change in costs to the sheep industry. The model indicated that treatment of sheep at lower levels of risk (less than 10%) would incur unnecessary costs due to treatment of flocks where no lice were present and would not reduce the regional prevalence of lice more effectively than a 10% intervention level. The model suggested that more accurate methods of detecting lice at shearing would allow higher levels of risk, reduce the use of treatment and hence reduce overall costs associated with managing lice, without increasing the prevalence of lice.

Age and size structures were determined in 40 stands of black spruce (Piceamariana (Mill.) B.S.P.) growing on peatlands and transitional peatlands in northeastern Ontario, Canada. Natural and second-growth stands representing several site types were examined. The age structure of natural black spruce stands varied from even aged in young stands (

The blowfly, Lucilia cuprina Wiedemann (Diptera: Calliphoridae), is the primary myiasis (strike) fly of sheep in Australia. Most strike occurs in the anal-perineum area (crutch), but strike to the neck, shoulders, back and withers (body) is also important. Regression analysis was used to determine the extent to which the weekly incidence of flystrike can be explained by variations in fly abundance and/or recent changes in weather, pasture conditions or flock management. Strike and flock management data were collected by questionnaire surveys of 30-60 sheep properties in each of three major sheep-producing areas in southeastern Australia, namely, Gunning (southern New South Wales), Inverell (northern New South Wales) and Flinders Island (Bass Strait). After using simulation modelling to remove effects due to shearing, crutching and/or insecticide treatment, pasture growth index was found to be the most important explanatory variable affecting the incidence of all forms of myiasis. Others were average weekly air temperature, the amount and frequency of rainfall, relative humidity, dung quality index and a factor denoting seasonal effects. Together, these variables accounted for 48.4% of the variation in body strike, 56.8% of that in crutch strike and 51.9% of that in other forms of strike. Prediction was improved by the inclusion of additional lagged variables describing previous strike, fly abundance and fly activity. With these additions, the variation explained increased to 60.4% for body strike, 68.0% for crutch strike and 58.3% for other strikes.

A model of the sheep breeding industry with nucleus flocks, multiplier flocks and commercial sheep flocks was used to examine the value of genomic selection. The model reflected a dual-purpose Merino breeding objective, with genomic information improving selection accuracy by 39% for rams at 6 months of age and by 17% at 18 months. The current level of net dollar benefit to the sheep industry from selection, but without genomic testing, can be improved by 10–14% for a closed three-tiered breeding structure with rams used at 18 months. If the rams are first used at 6–7 months then the dollar gains can be improved by 15–17%, since genomic information can provide proportionately greater gains for young animals that have limited phenotypic information. In a two-tiered breeding system, with nucleus flocks selling rams direct to commercial producers, rather than through multiplier flocks, the dollar gains to industry from genomic testing increased to ~12–13% for rams bred at 18 months, and 20–22% if nucleus rams are used at 6–7 months. The optimal structure requires two-stage selection, with an initial selection based on information available without genomic testing, to limit the cost of testing to only the superior rams. However, the optimum proportion of rams tested depends on the system and the cost of testing. In order to recover the cost of genomic testing, the nucleus flocks must recover up to 5% of the extra genetic gain as extra profit from sale of rams to commercial sheep producers.

The application of preventive treatment against flystrike early in spring (before strike occurs) may reduce the reproductive success of the sheep blowfly, thereby maintaining a low risk of flystrike throughout the fly season. This hypothesis has been examined using a weather-driven model of flystrike (incorporating a reduced risk due to early treatment), based on previous experimental studies. The model indicates that in the Gunning area (with a high flystrike risk), this reduction in seasonal risk would reduce total costs related to flystrike, reduce the overall use of preventive chemical treatment and reduce the number of sheep struck. However, in a lower risk area (Flinders Island), the value of early treatment would depend on the date of shearing and the local risk of flystrike. Under some conditions, no preventive treatment would be necessary in most years because of a regional low risk of flystrike, so there would be no economic benefit from always using early treatment. Early treatment is least likely to be cost-effective when shearing is required soon after the optimal date for early treatment. Further experimental studies are recommended to fully examine whether the previously reported reduction in flystrike resulting from early treatment is consistent over a wider range of climatic conditions.

A deterministic model for predicting the prevalence of lice in sheep flocks was compared with a stochastic model. The stochastic model was based on data from 100 000 simulated farms and encompassed: a range of lice detection levels at shearing, whether or not treatment was applied where no lice were detected, the efficacy of treatments used, and the adequacy of quarantine measures against entering sheep. The deterministic model generated more extreme estimates of the effects of lice management changes, and was judged unsatisfactory for long-term decision making. Predictions based on the stochastic model were consistent with reported survey values, suggesting the stochastic model could be used to predict benefits and costs associated with changes in louse-control methods. According to the stochastic model, the two factors that could provide the greatest reduction in dollar costs were improvement of quarantine by limiting the incidence of lice entering the flock, and improvement of eradication methods. The deterministic model suggested that there would be large benefits from improvement in detection, but the stochastic model only found small dollar benefits with improved detection in the absence of changes such as more effective treatments. Changing the proportion of flocks that were treated when no lice were detected had little effect on the predicted incidence of lousy flocks.

Cost is important when determining preventative treatment for flystrike. This paper presents modelled output comparing two common treatment alternatives; either a fixed annual application date or waiting until a set proportion of the flock is struck. The Inverell, Gunning and Flinders Island regions of Australia, which provide differing strike conditions, were used for analysis. Where the period of annual strike risk was longer than the period of protection provided by chemical treatment, it was economically favourable (by 1–3%) to wait until a pre-determined proportion of the flock were struck before applying preventive treatment, rather than always treating on a fixed date. However, with spring or autumn shearing, where the season of strike risk was a similar length to the protective period, it was preferable to treat on a fixed date. For Flinders Island, with a shorter flystrike season than Inverell or Gunning, there were small benefits in treating at a pre-determined threshold, but selection of the correct intervention point was critical. In areas with lower levels of risk, where treatment may not be required every year, it appeared beneficial to set a threshold at a sufficiently high level to eliminate most treatment intervention except for years with high rainfall and humidity.

Objective To investigate wool organophosphorus concentrations resulting from a range of farm pesticide application methods. Design Random sampling of wool for pesticide residues and on-farm interviews to determine associated treatments. Procedure Tasmanian fleece wool lots were sampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview. Results The residue concentrations showed a large variation that was not accounted for by differences in treatments by growers. Organophosphorus concentrations were proportional to the number of treatments applied, and inversely related to the time between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide residue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused larger residues than the use of jetting races. Conclusions We recommend that plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 months after shearing, provided only one application is administered.

A computer model for flystrike risk was used to predict the expected costs, pesticide used and number of sheep struck, according to time of shearing and crutching, for the regions Flinders Island, Gunning and Inverell. A comparison was carried out between mulesed and unmulesed sheep and the program optimised the preventive chemical treatments required to minimise overall costs associated with flystrike and flock treatments. This study examined cost differences between mulesed and unmulesed hoggets and ewes where the only change in management was in the method and timing of pesticide treatment. The model indicated that unmulesed sheep would require more frequent treatment with longer lasting pesticides. Costs associated with flystrike were estimated to increase by $220 per thousand sheep per year (ewes) or $349 (hoggets) for Flinders Island, $445 or $512 (Gunning) and $363 or $844 (Inverell). For unmulesed sheep the model indicated that dicyclanil might be required rather than cyromazine to provide acceptable flystrike control at a lower cost. Despite this increase in preventive treatment for unmulesed sheep, the predicted number of struck sheep was higher for Gunning and Inverell, but not for Flinders Island, where the model did not always require routine preventive treatment for mulesed sheep. In regions with a flystrike problem, avoiding any increase in strike after ceasing to mules was estimated to double the cost of preventive measures for most shearing dates. The date of shearing had a significant effect on total costs related to flystrike and in some cases shearing during the fly season increased costs and increased strike by interfering with the most efficient use of preventive treatment. Crutching reduced costs in some cases, but in other situations the timing of crutching interfered with the optimum timing of chemical treatment and the model sometimes predicted worse outcomes than with no crutching. The timing of shearing, crutching and treatment must be carefully managed if both costs and the number of struck sheep are to be minimised. Control of flystrike was found to be most efficient when there was a single period of high risk of strike or two equal periods of strike risk, rather than one short and one long period.

An economic model of the costs of sheep flystrike has been modified to examine the effect of a given change in the risk of breech strike as if it applied to the entire wool-producing industry, rather than to individual wool producers. Within each region (high rainfall, sheep/cereal and pastoral zones), the model sets the proportion of the sheep population in low, medium and high risk categories and calculates the estimated level of strike for untreated sheep in those groups. The costs related to breech strike can be calculated according to the original model. The risk of breech strike can then be adjusted to any required level, the proportion of sheep in each category adjusted and the costs recalculated according to the adjusted risk. The model estimated that a 50% reduction in the risk of breech strike would decrease the number of sheep requiring preventive treatment to about one-third of previous levels, but only provide a small reduction in costs related to struck sheep, due to the large increase in the number of sheep no longer receiving preventive treatment. There would be only small reductions in costs related to crutching and mulesing sheep unless much larger reductions in strike risk occurred. The overall benefit of a 50% reduction in the risk of strike would be $0.23–0.27 per sheep. If this reduction in strike risk occurred across all regions this could provide a benefit to the Australian sheep industry of $15 million. The model found that if mulesing was not used in any of the sheep then the use of preventive treatment would increase so that 93% rather than only 60% received chemical treatment, and reduction of the risk of breech strike by 50% provided benefits of $0.40 per sheep. Therefore, the estimated benefits would be greater than $0.27 per sheep in situations where the current level of risk is very high.

A model has been developed for the daily variation in soil temperature at 5 cm depth, for use where both the minimum and maximum temperatures are known or can be estimated. The model is based on data from three Australian sites with minute-by-minute data over 3–7 years. The model uses two sine curves; one for the increase from minimum to maximum and another for the relatively rapid decrease in temperature immediately after the maximum. An exponential decay function is used for the slower decrease in temperature until the minimum is reached. The time of the minimum soil temperature is primarily determined by the time of sunrise and therefore varies depending on the day of the year, whereas the time of the maximum temperature is influenced primarily by the time of the middle of the day (midpoint between sunrise and sunset). The time of the transition point between the maximum and the next minimum is related to the time of sunset. Therefore, the model uses latitude, longitude, and the day of the year to determine the time of sunrise and sunset to adjust the shape of the temperature profile throughout the day. The model has been validated using 3-hourly soil temperature data for 35 other sites in Australia, with a correlation of 0.993 between actual 3-hourly temperatures and those predicted. Its use for degree-day calculations has been validated using hourly data from a site in Victoria, where the model’s estimates of degree-days differ

An experiment was conducted to characterise population dynamics of lice and associated production loss in extensively grazed flocks infested at different times after shearing. Merino wethers were allocated to six groups of 31 sheep. In the first year (Y1), one sheep in each of two groups was infested with 2500 lice at 6 weeks after shearing (September), sheep in two groups were infested at 4 months (December) and two groups remained uninfested. In year 2 (Y2), infestations carried over from Y1, but a lousy sheep was added to each 6-week infestation mob. In year 3 (Y3), the infested mobs were treated and remained lice free, while lousy donor sheep were added to the two previously uninfested mobs. In Y1, lice appeared to die out in one 6-week-infestation group and were found on only two sheep before next shearing in the other. Lice persisted and spread in the two 4-month-infestation flocks, reaching mean counts (±s.e.) of 0.5 (±0.2) and 0.2 (±0.1) per part before shearing. In Y2 and Y3, lice persisted and increased in all infested flocks, reaching mean counts of 2.3 (±0.6), 8.5 (±1.5), 3.6 (±0.6) and 2.8 (±0.7) per part in Y2 and 1.0 (±0.2) and 1.2 (±0.4) per part in Y3. The count of 8.5 was in the flock with both a carry-over infestation and an infestor sheep. Exponential and logistic models were fitted to describe lice increase; differences in fleece derangement reflected louse numbers. Clean fleece weight was higher in flocks without lice in all years (0.12 kg/head in Y1; 0.22 kg/head in Y2 and Y3; P < 0.05). Classer-assigned colour scores (although not measured colour), cott score and line into which the wool was classed also differed significantly (P < 0.05) between infested and non-infested flocks and there was an indication that staple length was reduced in more heavily infested flocks. In spring-shorn flocks in environments with high solar radiation and no lice present at shearing, even if lice subsequently enter the mob, it appears unlikely that they will increase to levels where serious economic loss will be experienced before next shearing. The study also indicated that lice could persist in flocks at levels unlikely to be detected by most commercial wool producers for extended periods, possibly through one season, which may help to explain reports of new infestations with no apparent source.

Soil temperatures are related to air temperature and rainfall on the current day and preceding days, and this can be expressed in a non-linear relationship to provide a weighted value for the effect of air temperature or rainfall based on days lag and soil depth. The weighted minimum and maximum air temperatures and weighted rainfall can then be combined with latitude and a seasonal function to estimate soil temperature at any depth in the range 5–100 cm. The model had a root mean square deviation of 1.21–1.85°C for minimum, average, and maximum soil temperature for all weather stations in Australia (mainland and Tasmania), except for maximum soil temperature at 5 and 10 cm, where the model was less precise (3.39° and 2.52°, respectively). Data for this analysis were obtained from 32–40 Bureau of Meteorology weather stations throughout Australia and the proposed model was validated using 5-fold cross-validation.

The FlyBoss system consists of comprehensive information on flystrike management and control, programs for assisting decision making, and sortable lists of products for preventing and treating flystrike. Readily accessible, up-to-date, best-practice information on flystrike is essential for effective, humane and economic management of flystrike by Australian wool producers, particularly those who are phasing out mulesing and those looking to adopt optimal insecticidal fly-control strategies. FlyBoss provides information on breeding and management to reduce flystrike susceptibility, effective methods of treating existing flystrike and flystrike prevention programs. The FlyBoss decision aids, which are based on simulation models and incorporate local weather data and sheep susceptibility factors, can assist sheep farmers who wish to optimise sheep management, chemical treatment and non-chemical options to minimise the risk of flystrike. FlyBoss also contains comprehensive information on fly biology, sheep and environmental factors associated with flystrike and information on appropriate chemicals for various situations. FlyBoss draws on expertise from organisations throughout Australia to provide the sheep industry with easily accessible, current and locally targeted information on flystrike management. The present report briefly describes the development of FlyBoss and associated workshops and provides an overview of current recommendations for the control and prevention of flystrike.

This paper describes the development of a model, based on Bayesian networks, to estimate the likelihood that sheep flocks are infested with lice at shearing and to assist farm managers or advisers to assess whether or not to apply a lousicide treatment. The risk of lice comes from three main sources: (i) lice may have been present at the previous shearing and not eradicated; (ii) lice may have been introduced with purchased sheep; and (iii) lice may have entered with strays. A Bayesian network is used to assess the probability of each of these events independently and combine them for an overall assessment. Rubbing is a common indicator of lice but there are other causes too. If rubbing has been observed, an additional Bayesian network is used to assess the probability that lice are the cause. The presence or absence of rubbing and its possible cause are combined with these networks to improve the overall risk assessment.

A comparison was made of a range of different models of wool pesticide breakdown. Linear models, with a constant rate of breakdown as the wool grows, were always inferior to models that allowed the breakdown rate to decrease as the length of wool increased. Two-pool models were usually satisfactory and only minor or no improvement was gained by inclusion of additional pools or more complex models. There was little difference in fit between models with two-way diffusion compared with one-way transfer. The ‘standard’ model, reported previously, uses two exponential functions rather than multiple pools and was usually the best fit or at least as good a fit as the two- or three-pool models. We recommend that this model continue to be used, although the two-pool model is adequate and may be easier to implement and visualise. However, the three-pool model without transfer is also satisfactory and much faster to evaluate.

Summary. Several surveys have examined the relationship between organophosphate and synthetic pyrethroid residues in wool and associated treatments. These have been combined and summarised using a model of on-farm survey data. The model estimated the amount of chemical taken up by the wool at application. This was based on experimental breakdown rates of these pesticides on wool determined in controlled trials. For about 10% of survey results the chemical measured on the wool did not match the chemical the producer said was applied. A further 5% of results were excluded because the amount of chemical detected on the wool was inconsistent with the stated time of treatment and shearing. With the remaining results there was a very high variation in residues resulting from the same (stated) treatment. It is clear that many producers do not know what chemicals they have used or how much they applied. The wide variation in results suggests that some producers may apply excessive amounts of pesticides while others use too little to have a useful effect. The model estimated the amount of pesticide taken up by the fleece using the residue left at shearing and the known breakdown rate for a given method and chemical group. When organophosphates were applied by dipping, the amount of chemical taken up by the fleece appeared to increase as the length of the wool increased. This was generally higher than would be anticipated from label dose rates but was consistent with the stripping characteristics of these chemicals. Therefore dipping as soon as possible after shearing left much lower residues (

Surveys have examined the relationship between louse and flystrike treatments on farms and the resulting residues of insect growth regulators on greasy wool. These results have been summarised using a model of the on-farm survey data. The model estimated the amount of chemical taken up by the wool at application. This was based on experimental breakdown rates of these insecticides on wool determined in controlled trials. The data indicated that the backliner, triflumuron, when used off-shears within 24 h of shearing, was normally applied at slightly higher than the recommended rate on-farm and left an average residue of 30 mg/kg greasy wool at the following shearing 12 months later. Diflubenzuron, applied by dipping or jetting, was usually applied at lower than the recommended rates, and left an average residue of 40 mg/kg on the wool at shearing 12 months later. When treatment was applied to very short wool (

A model has been used to predict expected pesticide residues on wool at shearing after normal on-farm treatments. If wool producers keep accurate records of treatments at the time they are carried out, the model can predict the residue with greater accuracy and precision than if treatment records are less specific. The expected range is halved and the predicted residue is lower where wool producers have kept treatment records, compared with wool from previous surveys where only the usual farm information was available. If declarations by wool producers are used to assist wool buyers who require wool with low pesticide residues, these declarations will have more value if they are supported by documentation of treatments used on the sheep.

Summary. A model has been fitted to results from experimental application of organophosphates, synthetic pyrethroids and insect growth regulators to sheep mostly in long wool. The model relates the rate of breakdown of pesticide to the chemical used, the method of application and the length of wool at the time of treatment. A genetic algorithm was used to combine a range of experimental results for each chemical group to determine the rate of breakdown, and also the effect of application method and length of wool on breakdown. Organophosphates break down very quickly when applied to the surface of the wool (initial half-lives of 9–12 days), but the rate of breakdown gradually slows as the proportion of pesticide near the surface of the wool decreases. When the pesticide is applied deep into the wool by hand jetting or dipping, the rate of breakdown is slower (average half-lives of 27–42 days) and more uniform. Synthetic pyrethroids applied by hand jetting or backliner to sheep with 6–9 months wool growth initially break down with half-lives of 32–39 days, but the rate of breakdown decreases to 59–215 days giving average half-lives of 48–103 days over the 3–6 months between application and shearing. Cyromazine applied by hand jetting to sheep with 6–8 months wool growth has an average half-life of 79–96 days, but less if applied by automatic jetting race. The other insect growth regulators have longer half-lives: triflumuron, off-shears backliner, 119 days; and diflubenzuron, long wool jetting on to 7–9 months wool, >119 days. The model allows for different breakdown rates due to the method of application and length of wool and for changes in the rate of breakdown between application and shearing. It can be used to estimate the expected residue on wool at any time after a specified treatment, provided the amount of chemical applied is known. Conversely, the amount applied can be estimated from the residue and treatment details.

A genetic algorithm was evaluated as a means of using a computer model to determine the optimum structure of the Australian sheep breeding industry. The model simulates an open-nucleus 3-tiered sheep breeding system to investigate the benefit of strategies such as multiple ovulation and embryo transfer (MOET) and artificial insemination (AI) in terms of both genetic improvement and dollar values. The model indicated that both MOET and non- MOET systems benefit from an open nucleus, and both could also benefit from the promotion of some ewes from the commercial flocks. However, MOET systems require a relatively large number of rams, whereas non- MOET systems should have a smaller number of rams despite the much larger number of ewes needed. Under the conditions studied here, there was only limited advantage of MOET over non-MOET schemes. The optimum structure of the MOET, non-MOET and closed systems differ substantially. A genetic algorithm is a simple method for considering a single change (such as reproductive rate, or open v. closed) that may require major changes in the industry structure to achieve the full benefits. The method could also be of value in many other situations requiring optimisation of complex models.

Tasmanian Merinos and Polwarths were mated in each of 2 years to produce 2 drops of Merino, Polwarth, and F1 reciprocal cross progeny. Polwarths had weaning weights similar to Merinos but were 14% heavier as hoggets. Polwarths grew a similar amount of wool of 11% greater (P

The feeding pattern of rats fed the carcinogen 2‐acetylaminofluorene (AAF) ad libitum was investigated using a continuous‐recording electronic balance. Although a regular rhythm of eating was maintained, the timing of this rhythm was moved forward by 2–8 hrs. The extent of this shift increased with higher levels of dietary AAF, and with increasing time of AAF feeding. However, the degree of this change varied from rat to rat. As a result of the change in the timing of the diurnal rhythm of feeding, the rhythm of the AAF‐treated rats was no longer related to the controlled lighting conditions. There was also no relationship between the timing of the rhythm in any particular rat and the rhythms of rats in adjacent cages.

Causes of preweaning mortality were examined on a large intensive piggery. Diagnosis was made using comprehensive clinical histories combined with post-mortem data. Two thousand four hundred and twenty-six piglets were born in 238 litters. Pre-parturient and parturient losses were 2.9% and 5.4% of the total numbers of piglets born. Birth to weaning mortality was 11.3%. Among piglets born alive, overlaying was the most frequent cause of death (2.1%), followed by deaths due to diarrhoea (1.7%), anaemia (1.2%), savaging (1.1%) and losses of small weak piglets (0.9%). Most deaths, including stillbirths, were associated with below average birth weight, and two-thirds of all deaths of liveborn pigs occurred within 4 days of birth. Increased litter size resulted in decreased birth weights, an increased percentage of stillborn piglets and mummified foetuses, but duration of parturition was not affected. Stillborn piglets were born late in the litter and after a longer interval between pigs born (interpig interval). Over 70% of deaths due to overlay were in previously healthy piglets, but some were associated with illness of the sow (18%) or both sow and piglet (3%). Savaging was confined mainly to first parity sows and was responsible for 20% of all deaths in these litters. Sixty-two per cent of all piglets with a birth weight of less than 800g were stillborn or died before weaning compared with 18.7% mortality for all piglets. Anaemia in piglets was considered to be due to umbilical haemorrhage. Anaemic piglets had a 36% mortality to weaning compared with 10% for non-anaemic piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

The relative rates of sterol synthesis in the liver, ileum, and lung of the guinea pig have been studied by measuring the incorporation by tissue slices of 14C-labeled acetate into digitonin-precipitable sterols. The liver showed maximum incorporation of acetate at pH 6.5, the ileum at pH 7.5, and the lung at pH 6.0. The incorporation of acetate approached the maximum rate at a concentration of 10 mM with the liver and lung and 5 mM with the ileum. Using these conditions of assay, sterol synthesis was measured in the liver, ileum, and lung of four groups of guinea pigs killed at 6-hourly intervals. Depending on the time of day, the rate of sterol synthesis in the ileum was from 6 to 14 times that in the liver, while in the lung the rate was up to 3 times that shown by the liver, Additional studies showed that all regions of the small intestine synthesized sterol at a higher rate than the liver, with the highest rate of synthesis occurring in the ileum. The rates observed in the adrenal, testis, muscle, adipose tissue, and skin indicated that these tissues are not quantitatively important sites of sterol synthesis in the guinea pig.

SUMMARY Polioencephalomalacia (PEM) induced in sheep was compared with the disease found in naturally occurring cases. Blood biochemical indicators measured were pyruvate, lactate, glucose, erythrocyte transketolase (TK) and stimulation of TK by addition of thiamine pyrophosphate (TPP effect). Faeces and rumen contents were assayed for thiaminase activity. The effect of treating affected sheep with thiamine was also noted. It was found that amprolium treatment could induce thrombocytopenia, but once the sheep became accustomed to amprolium in the diet they seemed to be resistant to this effect. In sheep receiving amprolium significant weight losses preceded the onset of clinical signs. Further weight loss continued throughout the recovery period despite removal of amprolium from the diet and treatment with thiamine. Blood glucose was variable, and was elevated only when marked clinical signs were present. Pyruvate and lactate levels showed marked variation throughout the trial. TK values were depressed and TPP effects increased well before the onset of clinical signs, although some naturally occurring cases had normal levels. Faecal thiaminase activity was negligible in all the sheep on the amprolium trial but most field cases had a high level. High faecal thiaminase was observed in about 5% of clinically normal animals from affected flocks. Depression of erythrocyte TK activity coupled with the presence of faecal thiaminase appeared to be the most reliable diagnostic biochemical parameters for PEM. Treatment of PEM affected sheep with thiamine rapidly brought the biochemical status of the animals to normal. However where advanced brain lesions were present the damage was permanent and such sheep treated with thiamine remained partially decorticate. Copyright © 1981, Wiley Blackwell. All rights reserved

Laboratory rabbits maintained under controlled lighting and fed ad libitum exhibit a weak but consistent diurnal fluctuation in feed intake. There are two major periods of eating; at the beginning and the end of the light period. This results in similar feed consumption for the light and dark periods. Water intake shows a similar diurnal variation to that of feed intake. If the normal lighting cycle is retarded by 6 hours, the animals adjust their diurnal rhythm of feeding behaviour to the new lighting cycle within 8 to 15 days. Comparative studies on rats are included.

1. 1. We have examined the validity and usefulness of an assay for liver cholesterol synthesis using the inhibitor AY-9944, which inhibits only the conversion of 7-dehy-drocholesterol to cholesterol. 2. 2. In rats treated with a single dose of AY-9944 the level of 7-dehydrocholesterol in the blood 24 h after treatment is representative of the cholesterol which would have been synthesised by the liver had the inhibitor not been present. 3. 3. The assay has been tested under a variety of conditions known to alter liver cholesterol synthesis, and was found to correlate closely with values obtained when liver synthesis was measured in vitro. 4. 4. Consistent results were obtained with repeated assays, which can be carried out at weekly intervals on the same animals.

We have examined, both in vivo and in vitro, various aspects of the control of cholesterol and fatty-acid synthesis in the livers of rats fed the hepatocarcinogen, N-2-fluorenylacetamide. Within 1–4 weeks of beginning carcinogen treatment “feedback” control of cholesterol synthesis was partially or completely lost. Other controls over lipogenesis, however—fasting inhibition of cholesterol synthesis and dietary control of fatty-acid synthesis (fasting, refeeding after fasting, high-fat diet)—were retained. The normal diurnal rhythm of hepatic cholesterol synthesis was missing from carcinogen-treated animals, but this was due to an alteration in their daily pattern of voluntary food intake. The loss of “feedback” control of cholesterol synthesis was found to be not due to the reduction in food intake that accompanied carcinogen feeding. This work is further evidence in support of the hypothesis that a breakdown in “feedback” control of cholesterol synthesis is an important feature in the development of liver cancer.

The diurnal variation in cholesterol synthesis exhibited by rat liver has been examined in fed, fasted, and adrenalectomized animals. Fasting for 3 days caused a lowering of the rate of synthesis but did not abolish the diurnal rhythm. Adrenalectomy abolished the diurnal variation, and caused synthesis to re- main at a uniformly high level. We suggest that corticosterone may play an essential role in the daily rhythm of cholestero- genesis.

We have examined the Morris hepatomas 7794 A and 9618 A for the presence of a diurnal variation in cholesterol synthesis such as is observed in the livers of normal rats. Whereas the livers of the tumour-bearing animals showed a 3–5 fold increase in rate of cholesterol synthesis from acetate between midday and midnight, no such increase occurred in the hepatomas. Furthermore, adrenalectomy resulted in a 3 -fold increase in cholesterol synthesis (as measured at midday) in the host liver, but not in hepatoma 7794 A. Work by others has indicated that diurnal variations in cholesterol synthesis in normal liver are due to variations in the amount rather than in the specific activity of the ratecontrolling enzyme of the cholesterogenic pathway, namely β-hydroxy-β-methylglutaryl co-enzyme A reductase. Our work has now demonstrated that at least two of the "minimal-deviation" hepatomas exhibit a defect in control over the synthesis and/or degradation of this enzyme, i.e. in addition to the defective "feedback" control of its activity that has been shown in many previous reports.