In Australia, free-range layer pullets are typically reared indoors, but adult layers go outdoors, and this mismatch might reduce adaptation in laying environments. Enrichments during rearing may optimise pullet development and subsequent welfare as adult free-range hens. In the outdoor environment, hens may have greater opportunities for exercise and natural behaviours which might contribute to improved health and welfare. However, the outdoor environment may also result in potential exposure to parasites and pathogens. Individual variation in range use may thus dictate individual health and welfare. This study was conducted to evaluate whether adult hens varied in their external and internal health due to rearing enrichments and following variation in range use. A total of 1386 Hy-Line Brown® chicks were reared indoors across 16 weeks with three enrichment treatments including a control group with standard housing conditions, a novelty group providing novel objects that changed weekly, and a structural group with custom-designed structures to increase spatial navigation and perching. At 16 weeks of age the pullets were moved to a free-range system and housed in nine identical pens within their rearing treatments. All hens were leg-banded with microchips and daily ranging was assessed from 25 to 64 weeks via radio-frequency identification technology. At 64–65 weeks of age, 307 hens were selected based on their range use patterns across 54 days up to 64 weeks: indoor (no ranging), low outdoor (1.4 h or less daily), and high outdoor (5.2–9 h daily). The external and internal health and welfare parameters were evaluated via external assessment of body weight, plumage, toenails, pecking wounds, illness, and post-mortem assessment of internal organs and keel bones including whole-body CT scanning for body composition. The control hens had the lowest feather coverage (p < 0.0001) and a higher number of comb wounds (P = 0.03) than the novelty hens. The high outdoor rangers had fewer comb wounds than the indoor hens (P = 0.04), the shortest toenails (p < 0.0001) and the most feather coverage (p < 0.0001), but lower body weight (p < 0.0001) than the indoor hens. High outdoor ranging decreased both body fat and muscle (both p < 0.0001). The novelty group had lower spleen weights than the control hens (P = 0.01) but neither group differed from the structural hens. The high outdoor hens showed the highest spleen (P = 0.01) and empty gizzard weights (P = 0.04). Both the rearing enrichments and ranging had no effect on keel bone damage (all P ≥ 0.19). There were no significant interactions between rearing treatments and ranging patterns for any of the health and welfare parameters measured in this study (P ≥ 0.07). Overall, rearing enrichments had some effects on hen health and welfare at the later stages of the production cycle but subsequent range use patterns had the greatest impact.

The development of anthelmintic resistance by helminths can be slowed by maintaining refugia on pasture or in untreated hosts. Targeted selective treatments (TST) may achieve this through the treatment only of individuals that would benefit most from anthelmintic, according to certain criteria. However TST consequences on cattle are uncertain, mainly due to difficulties of comparison between alternative strategies. We developed a mathematical model to compare: 1) the most 'beneficial' indicator for treatment selection and 2) the method of selection of calves exposed to Ostertagia ostertagi, i.e. treating a fixed percentage of the population with the lowest (or highest) indicator values versus treating individuals who exceed (or are below) a given indicator threshold. The indicators evaluated were average daily gain (ADG), faecal egg counts (FEC), plasma pepsinogen, combined FEC and plasma pepsinogen, versus random selection of individuals. Treatment success was assessed in terms of benefit per R (BPR), the ratio of average benefit in weight gain to change in frequency of resistance alleles R (relative to an untreated population). The optimal indicator in terms of BPR for fixed percentages of calves treated was plasma pepsinogen and the worst ADG; in the latter case treatment was applied to some individuals who were not in need of treatment. The reverse was found when calves were treated according to threshold criteria, with ADG being the best target indicator for treatment. This was also the most beneficial strategy overall, with a significantly higher BPR value than any other strategy, but its degree of success depended on the chosen threshold of the indicator. The study shows strong support for TST, with all strategies showing improvements on calves treated selectively, compared with whole-herd treatment at 3, 8, 13 weeks post-turnout. The developed model appeared capable of assessing the consequences of other TST strategies on calf populations.

Predicting the effectiveness of parasite control strategies requires accounting for the responses of individual hosts and the epidemiology of parasite supra- and infra-populations. The first objective was to develop a stochastic model that predicted the parasitological interactions within a group of first season grazing calves challenged by 'Ostertagia ostertagi', by considering phenotypic variation amongst the calves and variation in parasite infra-population. Model behaviour was assessed using variations in parasite supra-population and calf stocking rate. The model showed the initial pasture infection level to have little impact on parasitological output traits, such as worm burdens and FEC, or overall performance of calves, whereas increasing stocking rate had a disproportionately large effect on both parasitological and performance traits. Model predictions were compared with published data taken from experiments on common control strategies, such as reducing stocking rates, the 'dose and move' strategy and strategic treatment with anthelmintic at specific times. Model predictions showed in most cases reasonable agreement with observations, supporting model robustness. The stochastic model developed is flexible, with the potential to predict the consequences of other nematode control strategies, such as targeted selective treatments on groups of grazing calves.

Heaping of used poultry litter produces elevations in temperature that lead to a significant reductions in pathogen load, analogous to pasteurisation. The speed and degree of heating varies with depth in the heap and with a range of factors that can be influenced by management. These include heap size, moisture content, turning and covering. In broad terms smaller heaps heat more quickly and are more appropriate for shorter pasteurisation periods. Turning of heaps is only beneficial for pasteurisation periods of longer than 7 days and potentially detrimental for periods of 6 days or shorter. On the other hand the benefits of covering heaps are reduced with longer pasteurisation periods. Addition of moisture is rarely needed and never required if covers are used. This paper summarises the effects and interactions between these practices and concludes with a brief suggested operating procedure.

Estimated breeding values (EBV) for faecal egg count (FEC) and genetic markers for host resistance to nematodes may be used to identify resistant animals for selective breeding programmes. Similarly, targeted selective treatment (TST) requires the ability to identify the animals that will benefit most from anthelmintic treatment. A mathematical model was used to combine the concepts and evaluate the potential of using genetic-based methods to identify animals for a TST regime. EBVs obtained by genomic prediction were predicted to be the best determinant criterion for TST in terms of the impact on average empty body weight and average FEC, whereas pedigree-based EBVs for FEC were predicted to be marginally worse than using phenotypic FEC as a determinant criterion. Whilst each method has financial implications, if the identification of host resistance is incorporated into a wider genomic selection indices or selective breeding programmes, then genetic or genomic information may be plausibly included in TST regimes

This study evaluates the feasibility of developing (or accessing) a sheep nematode epidemiology model for Australian conditions. Following consultation with animal health experts, such a model would need to predict the impact of integrated parasite control strategies (nutrition, grazing management, anthelmintic treatment strategies and selective breeding for resistance) upon productive traits, parasitological traits and the emergence of anthelmintic resistance. Seven existing nematode epidemiology models were reviewed to evaluate their suitability for Australian conditions in their current form, or after customisation. Whilst individually these models were found to be incapable of evaluating integrated parasite control strategies, a composite of these models could achieve this aim. The best functions from the models reviewed were identified and the initial outline of a composite model is consequently proposed. Access to such a model for industry advice, educational or research purposes can be facilitated via its inclusion in the WormBoss website following development of a user friendly interface. Further, providing open-access to the model source code will inform researchers of underlying assumptions, allow for thorough review, remove reliance upon an individual, and facilitate further development. Finally, the potential pathway and cost of developing a validated sheep nematode epidemiology model and advice tool is considered.

Intramuscular fat (IMF) content is an important attribute determining meat quality, with higher contents of IMF resulting in the improved palatability of beef. Currently, IMF content is subjectively determined by visual appraisal of intramuscular fat deposits within the longissimus dorsi (i.e. marbling score). Chemical analysis (ether extraction) provides an objective determination of IMF content. However, this method is destructive and incurs significant financial and diuturnal costs. A number of automated image analysis systems for determining tissue composition from CT scan images have previously been proposed (Thompson and Kinghorn 1992; Alston et al. 2005), but as yet none are capable of estimating IMF content. This abstract outlines a framework for the quantification of IMF from CT scan images of deboned beef primal cuts.

A model was used to investigate two mechanisms describing reductions in food intake (anorexia) observed during gastrointestinal parasitism in lambs, and to explore relationships between anorexia and food composition. The mechanisms were either a reduction in intrinsic growth rate, leading to a consequent reduction in food intake (mechanism 1; M1), or a direct reduction in food intake (mechanism 2; M2). For both mechanisms, lambs growing from 2 to 6 months of age were modelled, with one of three levels of trickle challenge with 'Teladorsagia circumcincta'. Scenarios were simulated for feeds varying in either protein or energy content, or both. Major differences were found between the predictions resulting from M1 and M2 on low-energy foods that constrained the intake of uninfected lambs through bulk. With M1, food intake was governed by the first operating constraint, whereas with M2 an additivity of constraints was observed. On the other foods, the duration of anorexia increased with increasing energy content of feed for M1, whilst the duration of anorexia decreased with increasing protein content of feed for M2. For foods that did not have an impact upon lambs' gastrointestinal tract capacity, published data were consistent with predictions of M2. Due to an absence of experimental data, no conclusions could be drawn for relationships between anorexia and food composition in the presence of other limiting constraints, such as bulk for low-energy foods. In conclusion, available experimental data and model predictions were consistent with anorexia having an impact directly on food intake, and with impacts of anorexia increasing with decreasing protein content.

Energy (E) and amino acids (AA) are two of the most expensive components in broiler diets. There is no general consensus regarding the interaction of E and AA on broiler performance and this requires further investigation. Phosphorus (P) is the third most expensive diet component after E and AA (Woyengo and Nyachoti, 2011). Phosphorus plays a vital role in E and AA metabolism, and protein synthesis while P requirement has not been established with certainty. It was hypothesized that the requirements of digestible lysine (dLys, based on the ideal ratio as suggested by Baker and Han, 1994), AMEn and available P (avP) for broilers are not in the same proportion and these nutrients may interact with each other to affect broiler performance. To test this hypothesis, an experiment was conducted using a 3-factor-3-level Box-Behnken design that included dLys (9.5, 10.5, 11.5 g/kg), AMEn (12.77, 13.19, 13.61 MJ/kg) and avP (3.0, 4.0, 5.0 g/kg) generating a total of 15 treatments with 5 replicates of 12 birds. A total of 1050 d-old Ross 308 male broiler chicks were fed a common starter diet (dLys 12.0 g/kg, AMEn 12.77 MJ/kg, avP 4.5 g/kg) up to d 14 and allocated to treatment diets from d 14-34. Response surface was fitted by first, second or third degree polynomial regressions in JMP statistical software v. 12.0.1.

Gastrointestinal parasites cost the Australian sheep industry AU$436 million annually. Early warning of impending worm risk may reduce this cost by providing producers sufficient time to implement control strategies. The provision of 90 day weather forecast data at a 6km grid resolution across Australia (Australian Bureau of Meteorology) has enabled the development of a mathematical model to predict the risk arising from nematode pasture infectivity for inclusion in the Sheep CRC's 'AskBill' application. A biophysical modelling approach was used to simulate the on-pasture lifecycle stages of 4 nematode species (Haemonchus contortus, Teladorsagia circumcincta, Trichostrongylus colubriformis and Trichostrongylus vitrinus). Mortality and development/migration rates of each lifecycle stage were described using modified β-distribution functions to account for the impact of temperature and water availability. The model was parameterised against point estimates from available literature and experimental data for the 4 species (H.contortus: R 2 = 0.88, n = 1409; T.circumcincta: R 2 = 0.56, n = 243; T.colubriformis: R 2 = 0.61, n = 355; T.vitrinus: R 2 = 0.66, n = 147). In the absence of a model predicting the quantity of eggs deposited, a probabilistic approach was used assuming 1 egg species-1 sheep-1 day-1 (thereby accounting for stocking rate). The impact of anthelmintic treatments were accounted for by assuming that no eggs were deposited for the duration of claimed efficacy. Risk was calculated by summing the proportion of infective larvae available for ingestion for each nematode species across each day of prior egg deposition and adjusting for herbage availability, species fecundity and productive impact.