Academic literature on the topic 'Animal production (pests and pathogens)'

Productivity of crops grown for human consumption is at risk due to the incidence of pests, especially weeds, pathogens and animal pests. Crop losses due to these harmful organisms can be substantial and may be prevented, or reduced, by crop protection measures. An overview is given on different types of crop losses as well as on various methods of pest control developed during the last century.Estimates on potential and actual losses despite the current crop protection practices are given for wheat, rice, maize, potatoes, soybeans, and cotton for the period 2001–03 on a regional basis (19 regions) as well as for the global total. Among crops, the total global potential loss due to pests varied from about 50% in wheat to more than 80% in cotton production. The responses are estimated as losses of 26–29% for soybean, wheat and cotton, and 31, 37 and 40% for maize, rice and potatoes, respectively. Overall, weeds produced the highest potential loss (34%), with animal pests and pathogens being less important (losses of 18 and 16%). The efficacy of crop protection was higher in cash crops than in food crops. Weed control can be managed mechanically or chemically, therefore worldwide efficacy was considerably higher than for the control of animal pests or diseases, which rely heavily on synthetic chemicals. Regional differences in efficacy are outlined. Despite a clear increase in pesticide use, crop losses have not significantly decreased during the last 40 years. However, pesticide use has enabled farmers to modify production systems and to increase crop productivity without sustaining the higher losses likely to occur from an increased susceptibility to the damaging effect of pests.The concept of integrated pest/crop management includes a threshold concept for the application of pest control measures and reduction in the amount/frequency of pesticides applied to an economically and ecologically acceptable level. Often minor crop losses are economically acceptable; however, an increase in crop productivity without adequate crop protection does not make sense, because an increase in attainable yields is often associated with an increased vulnerability to damage inflicted by pests.

Production of medicinal plants is accompanied by many problems, out of which some are overcome. Problems in medicinal plant production, including the production of sage and lemon balm that cannot be avoided are pathogens, the presence of insects and weeds. During the summer of 2003 and 2004, the occurrence of animal pests and pathogens was investigated in the medicinal plants lemon balm (Mellisa officinalis) and garden sage (Salvia officinalis). The pathogens Alternaria alternata and Fusarium moniliforme and the insects Eupterix atropunctata and Empoasca pteridis (Homoptera, Cicadelidae) were identified as the cause of various damages to medicinal plants.

AbstractBiological control is defined broadly as the “use of natural or modified organisms, genes, or gene products” to reduce the effects of pests and diseases. Physical control is the use of tillage, open-field burning, heat-treatment (pasteurization), and other physical methods, usually to eliminate pests or separate them from the crop. Chemical control is the use of synthetic chemical pesticides to eliminate pests or reduce their effects. The many approaches to biological control can be categorized conceptionally into 1) regulation of the pest population (the classical approach), 2) exclusionary systems of protection (a living barrier of microorganisms on the plant or animal that deters infection or pest attack), and 3) systems of self-defense (resistance and immunization). The agents of biological control include the pest- or disease-agent itself (sterile males or avirulent strains of pathogens), antagonists or natural enemies, or the plant or animal managed or manipulated (immunized) to defend itself. The methods range from 1) conserving and making maximum use of indigenous (resident) biological control through cultural practices, 2) making one-time or occasional introductions of genes or natural enemies that are more or less self-sustaining and 3) making repeated introductions of a biocontrol agent (e.g. a microbial pesticide). Biological, physical, and chemical treatments and pest controls can be integrated into holistic plant-health care also known as integrated crop and pest management. Eight principles of plant health care are offered: 1) know the production limits of the agroecosystem; 2) rotate the crops; 3) maintain soil organic matter; 4) use clean planting material; 5) plant well-adapted, pest-resistant cultivars; 6) minimize environmental and nutritional stresses; 7) maximize the effects of beneficial organisms; and 8) protect with pesticides as necessary.

The introduction of intensive technologies in modern agricultural production involves the widespread use of chemicals to protect plants and animals, including insecticides and acaricides. However, the development of arthropods resistance to the used drugs significantly reduces the efficiency of the chemical method of controlling insects and mites. The article describes the basic mechanisms of the development of resistance on which the study of a comprehensive strategy of combating pests and pathogens in plants and animals based on. Multiple resistance in case of revealed resistance of target objects to multiple substances is of particular importance. Necessity for the development of new insecticidal and acaricidal preparations as well as the improvement of the principles of their application to slow down the development of resistance in arthropods is required. In animal husbandry, the problem is compounded by developing parallel resistance of infectious agents to antimicrobial agents. This requires the development of a scientific-based methodology of pharmacological prevention and treatment of infectious and parasitic diseases of animals, as well as chemical protection of plants against pests and diseases.

Green cane harvesting is a new agricultural practice that provides many benefits to sugar cane production in Brazil by allowing cane straw to remain on the soil surface. However, this system has complicated the management of weeds, pests and diseases. This review will highlight the impact of green cane harvesting on the management of weeds, insect pests, and pathogens in sugar cane production, and cover novel techniques and practices used to manage pests in this production system. Brazil has a unique agroecosystem that includes tropical and subtropical climates and distinct technical challenges relative to other agricultural regions around the world. Sugarcane stands out as an economically important crop in Brazilian agriculture, both in terms of its planting area and the complexity of the production system (e.g., constant changes in planting, cultural practices, and harvest managements). Brazilian sugarcane production in the 2018/2019 season was 620.44 million tons produced over more than 8.5 million hectares distributed mainly in the states of São Paulo, Goiás, and Minas Gerais. Currently, 38% of this production is intended to produce sugar and 62% to ethanol, generating 29.04 million tons of sugar and 33.14 billion liters of ethanol, making Brazil the largest sugar and ethanol producing country in the world. The sugarcane agroindustry continues to expand in Brazil, showing a great capacity to aggregate value to byproducts of ethanol and sugar, such as vinasse (fertilizer), filter cake (fertilizer and soil conditioner), bagasse (raw-material for industries; animal feed; and electrical energy generation), and plant straws (electrical energy generation). The adoption of mechanized harvests without burning has allowed accumulation of sugarcane straw residues over the cropping area (green cane harvesting). Approximately 84% of the sugarcane production area in Brazil follows green cane harvesting practices. This harvesting system has made the management of weeds, pests and diseases even more complex in sugarcane fields than before. Green cane harvesting has made pest and weed management (mainly) more complex. The presence of residues on the soil directly affects the action of pre-emergent herbicides that are most commonly used in sugarcane and increases the incidence of some important pests such as S. levis and M. fimbriolata. Integration of management programs for weeds, pests, and diseases generates economic benefits and control efficacy (broad spectrum action), maximizing their individual efficacy level, reducing the dependence on only one of them and the risk of selection of resistant pest populations. Monitoring, planning, and evaluation of the history of the sugarcane fields are essentials and assist in decision making regarding the method and time of control to be used. The efficiency of this system assists in the maintenance of high yields, health, and longevity for sugarcane fields.

Asexual Epichloë spp. fungal endophytes have been extensively studied for their functional secondary metabolite production. Historically, research mostly focused on understanding toxicity of endophyte-derived compounds on grazing livestock. However, endophyte-derived compounds also provide protection against invertebrate pests, disease, and other environmental stresses, which is important for ensuring yield and persistence of pastures. A preliminary screen of 30 strains using an in vitro dual culture bioassay identified 18 endophyte strains with antifungal activity. The novel strains NEA12, NEA21, and NEA23 were selected for further investigation as they are also known to produce alkaloids associated with protection against insect pests. Antifungal activity of selected endophyte strains was confirmed against three grass pathogens, Ceratobasidium sp., Dreschlera sp., and Fusarium sp., using independent isolates in an in vitro bioassay. NEA21 and NEA23 showed potent activity against Ceratobasidium sp. and NEA12 showed moderate inhibition against all three pathogens. Crude extracts from liquid cultures of NEA12 and NEA23 also inhibited growth of the phytopathogens Ceratobasidium sp. and Fusarium sp. and provided evidence that the compounds of interest are stable, constitutively expressed, and secreted. Comparative analysis of the in vitro and in planta metabolome of NEA12 and NEA23 using LCMS profile data revealed individual metabolites unique to each strain that are present in vitro and in planta. These compounds are the best candidates for the differential bioactivity observed for each strain. Novel endophyte strains show promise for endophyte-mediated control of phytopathogens impacting Lolium spp. pasture production and animal welfare.

Animal health measures mainly rely on vaccination or chemical control for major pests and pathogens, causing issues of residue, toxicity and development of resistance. For example, control of Sheep flystrike and lice-infestation affecting the Australia’s sheep/wool industry (>3.5 B) have developed resistance to nearly all control chemicals used in the past. Topicals RNAi provides an innovative clean-green, non-toxic, environmentally sustainable biological control solution. Biodegradable clay particles as carriers can be used to deliver double stranded RNA (dsRNA), the key trigger molecule of RNA interference pathway. As an early proof of concept, we investigated the stability dsRNA loaded on two types of Clay particles: Clay 1 (releases dsRNA under acidic conditions) and Clay 2 (releases dsRNA under alkaline conditions) on cattle hide. Cattle skin was treated with Cy3 labelled dsRNA alone and Cy3 labelled dsRNA loaded on Clay1 or Clay2. The skin samples treated with the Cy3 formulations were imaged using confocal microscopy. Once imaged, the skin samples were washed and stored at room temperature for 5 days, later the samples were re-imaged to detect the fluorescent signal (Figure 1). The dsRNA loaded on clay particles was stable unlike naked Cy3-dsRNA which degraded and was not visible after washing. This increased inherent stability of the dsRNA molecules, combined with the environmental stability afforded by the Clay particles, offers promise to provide a sustainable solution for animal health. Topical RNAi can reduce reliance on trade withholding periods of meat/wool without chemical residues, enhance animal welfare and increase production of premium quality meat/wool, improve export potential, competitiveness and long-term profitability of livestock industry.

Climate change has already affected food security in many parts of the world, and this situation will worsen if nothing is done to combat it. Unfortunately, agriculture is a meaningful driver of climate change, through greenhouse gas emissions from nitrogen-based fertilizer, methane from animals and animal manure, as well as deforestation to obtain more land for agriculture. Therefore, the global agricultural sector should minimize greenhouse gas emissions in order to slow climate change. The objective of this review is to point out the various ways plant growth promoting microorganisms (PGPM) can be used to enhance crop production amidst climate change challenges, and effects of climate change on more conventional challenges, such as: weeds, pests, pathogens, salinity, drought, etc. Current knowledge regarding microbial inoculant technology is discussed. Pros and cons of single inoculants, microbial consortia and microbial compounds are discussed. A range of microbes and microbe derived compounds that have been reported to enhance plant growth amidst a range of biotic and abiotic stresses, and microbe-based products that are already on the market as agroinputs, are a focus. This review will provide the reader with a clearer understanding of current trends in microbial inoculants and how they can be used to enhance crop production amidst climate change challenges.

Plant pests and pathogens have been a serious problem for farmers for many years and have been a major threat to plant health and food production. Farmers use synthetic chemicals to improve crop yields and to control plant pathogens from destroying their crops. Chemical-based fertilizers provide immediate relief, but their excessive use also causes severe environmental problems and can have adverse effects on groundwater, plants, animals and even entire ecosystems. Many countries have banned highly toxic chemicals which are harmful to the environment. One of the key challenges facing plant biologists is the development of new technologies and environmentally friendly alternatives to chemicals for combating crop diseases. An increase in world population has resulted in a reduction in agricultural land area. However, this area will be required to produce 50% more food by 2050 to feed the 10 billion people living on the planet. Biological control plays an important role ...

Owing to growing population of world, efforts are being made to maximise food production. Food safety should not be compromised to meet the food requirement of increasing population. Biosecurity is the imperative approach to ensure food safety. This is a holistic approach that interlinks health, environment, security and trade. Increased incidents of foodborne diseases led to promotion of biosecurity as a major priority policy worldwide to curtail such incidents and ensure food safety. Microbial risk management is an essential component of food safety. National biosecurity programmes are essentially required to identify the prospective modes of introduction and spread of a disease in a country or region and to specify the control measures to curtail the risk associated with the disease. International standards for various biosecurity sectors are set mainly by Codex Alimentarius Commission, the World Organisation for Animal Health and Commission on Phytosanitary Measures, which are implemented through the Sanitary and Phytosanitary Agreement, 1995 of World Trade Organisation. Agricultural biosecurity is of utmost importance in the countries that are large crop and animal producers, and these countries are at risk from alien pests and pathogens. Adequate biosecurity programmes are essential in all the countries to protect global environment, agriculture and biodiversity. Developing countries, particularly with large populations aiming maximised food production require stringent biosecurity approaches to provide safe and nutritious food to the people.

This thesis is concerned with the application of recently developed epidemiological and statistical tools to inform the optimisation of a national surveillance strategy of considerable importance to human health. The results of a series of epidemiological investigations of surveillance strategies for zoonotic Salmonella are presented. Salmonella are one of the most common and serious zoonotic foodborne pathogenic bacteria globally. These studies were motivated by the increasing focus on the cost-effectiveness of surveillance while maintaining consumer confidence in food supply. Although data from the Danish Salmonella surveillance and control programme has been used in these investigations, the techniques may be readily applied to other surveillance data of similar quality. The first study describes the spatial epidemiological features of Danish Salmonella surveillance and control programme data from 1995 to 2004, using a novel method of spatially adaptive smoothing. The conditional probability of a farm being a case was consistently high in the the south-west of Sonderjylland on the Jutland peninsula, identifying this area for further investigation and targeted surveillance. The identification of clustering of case farms led into the next study, which closely examines one year of data, 2003, for patterns of spatial dependency. K-function analyses provided evidence for aggregation of Salmonella case farms over that of all farms at distances of up to six kilometres. Visual semivariogram analyses of random farm-level effects from a Bayesian logistic regression model (adjusted for herd size) of Salmonella seropositivity, revealed spatial dependency between pairs of farms up to a distance of four kilometres apart. The strength of the spatial dependency was positively associated with slaughter pig farm density. We describe how this might inform the surveillance programme by potentially targeting herds within a four kilometre radius of those with high levels of Salmonella infection. In the third study, farm location details, routinely recorded surveillance information, and industry survey data from 1995 were combined to build a logistic seroprevalence model. This identified wet-feeding and specific pathogen free herd health status as protective factors for Salmonella seropositivity, while purchasing feed was a risk factor. Once adjusting for these covariates, we identified pockets of unexplained risk for Salmonella seropositivity and found spatial dependency at distances of up to six km (95% CI: 2–35 km) between farms. A generalised linear spatial model was fitted to the Jutland data allowing formal estimation of the range of spatial correlation and a measure of the uncertainty about it. There was a large within-farm component to the variance, suggesting that gathering more farm level information would be advantageous if this approach was to be used to target surveillance strategy. The fourth study again considers data from the whole study period, 1995 to 2004. A detailed temporal analysis of the data revealed there was no consistent seasonal pattern and correspondingly no benefit in targeting sampling to particular times of the year. Spatiotemporal analyses suggested a local epidemic of increased seroprevalence occured in west Jutland in late 2000. Lorelogram analyses showed a defined period of statistically significant temporal dependency, suggesting that there is little value in sampling more frequently than every 10 weeks on the average farm. The final study uses findings from the preceding chapters to develop a zero-inflated binomial model which predicts which farms are most at risk of Salmonella, and then preferentially samples these high-risk farms. This type of modelling allows assessment of similarities and differences between factors that affect herd infection status (introduction) and those that affect the seroprevalence in infected herds (persistence and spread). The model suggested that many of the herds where Salmonella was not detected were infected but at a low prevalence. Using cost and sensitivity, we compared the results with those under the standard sampling scheme based on herd size, and the recently introduced risk-based approach. Model based results were less sensitive, but showed significant cost savings. Further model refinements, sampling schemes, and the methods to evaluate their performance are important areas for future work, and should continue to occur in direct consultation with Danish authorities.

Animal health surveillance is an important part of animal health care, particularly in countries dependent on livestock for food production and international trade. There are two major issues related to the provision of e®ective surveillance activities. Firstly, for good information to become available, the design and conduct of data collection activ- ities should be carried out following sound statistical principles. In reality, constraints such as imperfect tests and unavoidably-biased sampling strategies hinder straightfor- ward analysis and interpretation of survey results. Risk-based surveillance is used to target high-risk sub-populations to increase e±ciency of disease detection; however, biased datasets are generated. This thesis develops methodologies to design risk-based surveillance systems and al- low statistically valid analysis of the inherently biased data they generate. The ¯rst example describes the development of a method to analyse surveillance data gathered for bovine spongiform encephalopathy (BSE). The data are collected from four dif- ferent surveillance streams of animals tested for BSE, with each stream containing unavoidable biases and limitations. In the BSurvE model, these data are combined with demographic information for each birth cohort to estimate the proportion of each birth cohort infected with BSE. The prevalence of BSE in a national herd can then be estimated using the method of moments, whereby the observed number of infected animals is equated with the expected number. The upper 95% con¯dence limit for the prevalence is estimated both for infected countries and for those where no BSE has previously been detected. A similar approach to that used in BSurvE is then applied to surveillance data for trichinellosis, for which risk-based post-mortem testing is also performed. Negative results from multiple species using di®erent, imperfect tests are combined to give an estimate of the upper 95% con¯dence limit of the national prevalence of trichinellosis in a reference population. This method is used to provide support for freedom from trichinellosis in Great Britain. A di®erent approach to risk-based surveillance is explored as the surveillance strategy for detection of exotic causes of abortion in sheep and goats in New Zealand is examined. Using a geographic information system (GIS) maps of disease risk factors were overlain to produce a risk landscape for the lower North Island. This was used to demonstrate how areas of high- and low-risk of disease occurrence can be identi¯ed and used to guide the design of a risk-based surveillance programme. Secondly, within one surveillance objective there may be many ways in which the available funds or human resources could be distributed. This thesis develops a method to assess BSE surveillance programmes, and provides tools to facilitate BSE detection on the basis of infection risk and to increase the e±ciency of surveillance strategies. A novel approach to allocation of resources is developed, where portfolio theory con- cepts from ¯nance are applied to animal health surveillance. The example of surveil- lance for exotic causes of sheep and goat abortion is expanded upon. Risk of disease occurrence is assessed for a population over di®erent time periods and geographical areas within a country, and portfolio theory used to allocate the number of tests to be carried out within each of these boundaries. This method is shown to be more likely to detect disease in a population when compared to proportional allocation of the available resources. The studies presented here show new approaches that allow better utilisation of imperfect data and more e±cient use of available resources. They allow development of surveillance programmes containing an appropriate balance of scanning and targeted surveillance activities. Application of these methods will enhance the implementation and value of surveillance in animal health.

This thesis describes a series of three experiments designed to estimate the nutritional cost of the immune response to the gastrointestinal nematodes Trichostrongylus colubriformis and Teladorsagia circumcincta in sheep. For each experiment, animals were allocated hierarchically by liveweight into one of four groups that were either infected (group IF), similarly infected and concurrently immuno-suppressed with weekly intramuscular injections of 1.3mg kg liveweight (LW)⁻¹ of methylprednisolone acetate (group ISIF), immunosuppressed only (group IS) or remained as controls (group C). Body composition of all animals was estimated using x-ray computer tomography prior to infection and at the conclusion of each study with bodyweight and faecal nematode egg counts (FEC; eggs gram⁻¹ of fresh faeces (epg)) measured along with blood samples taken for the determination of levels of serum proteins, phosphate and antibodies. In the first trial (Chapter 3), the nutritional cost of both the acquisition and maintenance of immunity to gastro-intestinal nematodes was investigated using immunologically naive 5-month-old lambs and immunologically competent 17-month-old ewes during infection with 2,000 and 4,000 L3 infective T. colubriformis larvae d⁻¹, respectively (80 L3 T. colubriformis larvae kgLW⁻¹ d⁻¹). Profiles of FEC and comparative worm burdens at slaughter indicated an effective immune response was maintained in IF ewes and developed in IF lambs while successfully suppressed in both ISIF lambs and ISIF ewes and was confirmed by serum antibody titres. The typical reduction in voluntary feed intake as a consequence of infection was observed in IF lambs (0.30, p<0.001) but not in IF ewes, ISIF lambs or ISIF ewes, and appeared to be associated with L3 IgA. Gross efficiency of use of metabolizable energy (ME) for net energy (NE) deposition was reduced by 0.20 in lambs during acquisition of immunity and by 0.16 in ewes maintaining an established immunity. Infection in immuno-suppressed animals reduced efficiency by 0.05 and 0.15 for lambs and ewes. These findings allowed the hypothesis that the reduction in feed intake and nutrient utilization in young parasitized sheep is caused by physiological signalling associated with the acquisition phase of the host immune response to infection, rather than simply the damage caused by the parasite per se. The second trial (Chapter 4) investigated the influence of metabolizable protein (MP) supply on the metabolic disturbances associated with the acquisition phase of the immune response during infection with 2,000 L3 T. colubriformis d⁻¹. Groups of lambs were offered either a low protein (L; 62g MP kgDM⁻¹) or high protein diet (H; 95g MP kgDM⁻¹). Patterns of total daily egg excretion indicated that an effective immune response was developed in HIF, but not LIF, HISIF nor LISF and was confirmed by comparative worm burdens. The proportionate reduction in feed intake in immunologically normal animals was reduced through the provision of additional protein, being 0.12 in HIF and 0.23 in LIF. Regardless of diet, infection did not cause a reduction in feed intake in immuno-suppressed animals (p>0.05). Infection proportionately reduced the gross efficiency of ME utilization in immunologically normal animals by 0.23 in HIF (p=0.09) and by 0.51 in LIF (p=0.01), but not in immuno-suppressed animals. Immuno-suppression did not suppress serum L3 IgA levels in seven of the eight HISIF and four of the eight LISIF animals. Furthermore, only four out of the eight immunologically normal animals from both the HIF and LIF groups displayed an L3 IgA response. Consequently, regardless of immunosuppression treatment, animals were termed as IgA responders (HR or LR) or non-responders (HN or LN). Feed intake was proportionately reduced from day 22 by 0.15 in HR (p=0.03) and by 0.32 in LR (p=0.01), but was not significantly reduced in HN or LN. Gross efficiency of ME utilization was significantly reduced for LN animals only, being proportionately 0.59 (p<0.01). These findings allowed the conclusion that additional MP reduced the consequence of immunological signalling that was displayed in reduced feed intake and in nutrient utilization, both of which appeared to be associated with an IgA response. It is hypothesized that the lessening of nutritional disturbance observed in high protein and immuno-suppressed animals could be a consequence of altered physiological signalling during the immunological cascade. The third trial (Chapter 5) utilized lambs infected with the abomasal parasite T. circumcincta to explore the possibility that the reduction in feed intake and nutrient utilization is a universal phenomenon of the acquisition phase of the immune response to nematode parasites inhabiting different organs along the gastrointestinal tract. In addition, immunological changes at the site of parasite infestation in the abomasal mucosa were measured from serial biopsy tissue samples taken from a further twelve animals that were surgically fitted with an abomasal cannula and either infected (CIF) or concurrently infected and immuno-suppressed as described previously (CISIF). The development of immunity in IF animals was accompanied by a 0.17 proportional decrease in feed intake between days 15 to 28 of infection (p<0.05) and a 0.20 proportional reduction in nutrient utilization (p=0.07), none of which were observed in ISIF animals. While FEC and worm burdens indicated successful immunosuppression in ISIF animals, both serum IgA and total antibody production were not reduced. The development of immunity in CIF was reflected in an increase in both mast cells and globule leukocytes in serial abomasal tissue biopsies, both of which were reduced in CISIF (p<0.01 for both). In serial biopsy tissue, immuno-suppression did prevent a rise in tissue IgA that was apparent in CIF animals (p<0.01) although these changes were not reflected in serum IgA levels. It appears that the alleviation of the reduction in feed intake and nutrient utilization in young lambs through the use of corticosteroid induced immuno-suppression may be a universal phenomenon for both intestinal and abomasal parasites, but the association with and/or role of IgA during infection with T. circumcincta is unclear. In summary, the reduction in feed intake and nutrient utilization in sheep during infection with both the abomasal nematode T. circumcincta and the small intestine nematode T. colubriformis appears to be associated with a component(s) of the acquisition phase of the host immune response, rather than, as conventionally assumed, the direct mechanical damage of the parasite per se. It is hypothesised that the nutritional disturbance as a consequence of infection in young lambs may be the result of pro-inflammatory cytokines involved in immunological signalling that may also be associated with the production of IgA, the effects of which can be reduced through the provision of adequate MP. These studies provide evidence that the immune response to gastrointestinal parasites is nutritionally costly to the animal and have implications for application of manipulations that are intended to promote the development of a strong immune reaction in high producing animals.

The series of experiments described in this thesis were designed to investigate the role of suckling or late weaning in the response of young lambs to nematode infection. All experiments were conducted outdoors with grazing animals and no supplementation but for suckled groups of lambs whose counterparts were weaned to ryegrass – white clover swards. The parasite of interest was mainly Teladorsagia circumcincta solely but with mixed infection of Trichostrongylus colubriformis in one instance. In Chapter 3 (first experiment), the hypothesis that milk per se may have a direct effect on nematode development, rather than an indirect effect through enhancement of host immunity by superior nutrient supply was tested. Sixty, twinborn lambs were used, allocated to one of eight groups formed by either dosing lambs from 42 days of age or not with the equivalent of 1000 or 250 L₃ T. circumcincta larvae d⁻¹ until five days before necropsy, while a twin was either weaned at 39 days of age, suckled as single or twin until necropsy on day 84. The possibility that weaning one of a twin set onto pasture in close proximity to the ewe would cause abnormal ewe and lamb behaviour was tested by replicating the work in twins maintained as twins but in which one twin received equivalent of 250 and the other 1000 L₃ T. circumcincta larvae d⁻¹. This showed no abnormal ewe nursing or lamb suckling behaviour as a result of weaning a twin in a set. Relatively low faecal egg counts (FEC) and a two to three fold lower worm burdens suggest suckling could reduce larval establishment. Inability to detect peripheral titres of immunoglobulins supports this conclusion. An intra worm-population regulation of T. circumcincta, indicated by a pattern of greater egg-laying by a numerically smaller but physiologically better developed nematode population in suckled lambs measured in eggs 'in utero' and worm length made interpretation of FEC difficult. Suckling significantly improved weight gain and carcass weights, but early weaning did not reduce resilience to infection. In Chapter 4 (second experiment), 40 pairs of twin lambs, average age of 39 days, were either infected with the equivalent of 1000 L₃ T. circumcincta larvae d⁻¹ or not, while one twin was weaned and the other allowed to continue suckling. Necropsy was carried out on groups of five and six lambs from each of the uninfected and infected treatments, respectively, at mean age of 84, 112, and on six lambs from each group at 140 days of age. This serial slaughter allowed further confirmation of the hypothesis in Chapter 3 but also investigated the long-term effect of suckling on resistance or resilience of lambs at the trial when immune responses were anticipated to be developing. An in vitro direct larval challenge (IVDC) study, to monitor larval establishment, was carried out on tissue explants from necropsied lambs. Suckled lambs consistently showed lower FEC (P < 0.05) and worm burdens (P < 0.05) at every phase of the trial. Within the infected groups, % in vitro larval rejection suggested earlier immune responses in the weaned lambs by day 84, which was not consistent with lower worm burdens in suckled lambs but appeared similar in the subsequent necropsies. Lambs continued to show better growth due to suckling while weaning did not reduce the resilience of lambs confirming observations in Chapter 3. The immunoglobulin profile suggested the commencement of immune responses in lambs from the period after the 84th day necropsy, with significantly greater (P < 0.01) IgA titre in the infected groups, and the suckled lambs towards the end of the trial on day 140. A vaccinating effect of early exposure to parasites was coincidentally revealed as a result of unintentional pasture larval contamination, seen in suckled non-infected lambs shedding fewer eggs and harbouring fewer worms during the later necropsies compared with their weaned non-infected counterparts. In Chapter 5 (third trial), 93 pairs of twin lambs, 47 pairs of which received a vaccinating mixed infection of T. circumcincta and T. colubriformis larvae (60 L₃ / kg W / d) at ratio 40:60, respectively during the period 36 – 103 days of age, were either weaned early on day 51 or later on day 108. All lambs were drenched on day 108 and groups received challenge infections from day 116, at same rate with the vaccinating infection, or not, which ceased five days before respective necropsies. Necropsies were carried out on selected lambs on days 108, 184 and 218. The direct effect of milk on larval establishment appeared to feature only in the T. circumcincta populations on slaughter day 108. The long-term benefit of late weaning for development of resistance was conditional on lambs receiving the vaccinating infection, and appeared to be more pronounced in the small intestine, reflected by a greater reduction of T. colubriformis populations in that organ than of T. circumcincta populations in the abomasum. A negative consequence of enhanced immune response was the suggestion of an increased metabolic cost in reduced performance of lambs. In conclusion, the work provides support to the hypotheses that: (a.) suckling may reduce the establishment of nematode larvae through the direct effect of milk, (b.) may enhance rapid development of host immunity to infection, and (c.) it further suggests that lack of larval experience during suckling may have long term negative implications for host resistance. Finally, it suggests that milk may play little role in the enhancement of host resilience to infection and, on the contrary, that additional metabolic cost may be associated with a more rapid development of immunity resulting from larval challenge while suckling.

The major toxins and pathogens in fish meal were investigated because of food industry, public and animal health concerns. The effect of processing, the type of raw material used and storage conditions on the main toxin, histamine which causes gizzard erosion in poultry, and its formation in fish meal were investigated. The results showed that histamine and histamine-like amines in fish meal varied in levels between batches depending on the quality of raw material and type of fish used. The relationship between histamine and histamine-like amines levels was unclear. During laboratory processing of fish meal it was found that most histamine concentrated in the stickwater which had implications for the use of stickwater meal in feeds. Interestingly, histamine was detected in the stickwater meal of cod as well as mackerel. A decrease in histamine in mackerel meal and cod meal during processing was observed with respect to levels in raw material. The decrease maybe originated after the cooking stage especially in the stickwater meal (probably due to bacterial recontamination or enzymatic reactions). The decrease could be due to histamine either adhering to the equipment used or breakdown to its metabolites or derivitising to gizzerosine. Since very low levels of histamine were observed from meals produced from reasonably fresh fish, the control of histamine therefore is best achieved at the raw material stage of production. During storage trials, there was no increase in histamine levels but a decrease occurred gradually with time at 15°C, 70% RH. Rapid loss occurred at 25 and 30°C, 80% RH and heavy mould growth was also observed, although no mycotoxins were detected in analysed samples. Routine analytical methods were studied and compared for the requirements of the fish meal industry and poultry farmers. Problems occurred with the colorimetric method when applied to fish meal and fish samples containing bones due to the presence of calcium. It was modified for routine histamine analysis. Thin Layer Chromatography was the second alternative. Although High Performance Liquid Chromatography was suitable for analysing histamine and histamine-like amines together, it did lack in meeting industrial requirements. Since the modified colorirnetric method was labour intensive, despite its other advantages, there was still a need for a simpler and quicker method of analysis. For this reason, research work was carried out to develop an immunoassay for histamine analysis. The results showed that it was possible to raise antibody against histamine and suggested future research potential. Hygienic conditions of laboratory scale fish meal production were investigated. The presence of Salmonella, which leads to human salmonellosis, and E. coli 0157:H7 which also cause human food poisoning were studied. The results showed that the critical control point of fish meal production was after cooking, since recontamination can occur. Salmonella was present in several batches of commercial and laboratory processed samples, but no E. coli 0157:H7 was detected in analysed samples. Three rapid methods were compared to traditional method for Salmonella analysis particularly in fish meal. The immunoassay method introduced by Institute of Food Research, Norwich was found the most suitable because it was sensitive, specific and took about one day to complete.

A reduction in voluntary feed intake is a major factor in the lost productivity of grazing lambs infected by gastrointestinal parasites yet the mechanisms involved are poorly understood. Potential pathways involved in parasite-induced feed intake depression were investigated in lambs with minimal previous exposure to parasites and artificially infected by the small intestinal parasite Trichostrongylus colubriformis. Six in vivo experiments were conducted on lambs housed in individual pens or metabolism crates with similar feeding and experimental procedures. In Experiment 1 (Chapter 4) the effect of T. colubriformis infection on short term feed intake in lambs and of some pharmacological agents on feed intake depression were investigated. Prior to and for the duration of infection, lambs were fed once per day and feed intake recorded at regular intervals over the day (8 h). Following the onset of feed intake depression in the infected group (9 weeks after commencing dosing), all animals were treated with an analgesic (codeine phosphate per os), an anti-inflammatory agent (indomethacin per os), a CCK antagonist (L364-718 by subcutaneous injection) or saline (control) in a replicated Latin square design (n = 8). Although the pattern of feed consumption was similar in infected and non-infected lambs, average daily intake was reduced 32 % and short term intake (recorded at 10 minute intervals for the first hour of feeding, 15 minute intervals for the second hour and hourly for the next 6 hours of feeding) reduced 40 % by infection. This identified the key component by which intake was depressed and enabled the use of a short term intake model and short duration of action compounds to identify the pathways involved in intake depression in this sequence of experiments. None of the pharmacological treatments increased intake in the infected group. These results suggest a reduction in the rate of consumption due to reduced hunger signals, rather than change of meal eating patterns, is the major cause of feed intake depression. Specific conclusions about the pathways investigated using the pharmacological agents could not be obtained. Experiment 2 (Chapter 5) was designed to investigate the roles of pain and osmolality on feed intake depression. Digesta samples collected prior to and during parasite infection and before and after feeding had similar osmolalities (240-260 mosmol/l) which indicated that feeding or infection had no effect on osmolality of digesta. Following the onset of feed intake depression in infected animals, all animals were treated in a Latin square design (n = 4) with no treatment, saline, local anaesthetic (xylocaine) or analgesic (codeine phosphate) solution 15 minutes before feeding, by slow injection into the duodenum. There was no effect of these treatments on food intake. In the second part of the experiment, hyperosmotic solutions (mannitol and NaCI) markedly depressed short term intake in non-infected animals, suggesting a role for osmoreceptors in intake regulation. However these effects were not blocked by local anaesthetic so the depressed intake may have resulted from generalised malaise rather than from specific osmoreceptor effects. In Experiment 3 (Chapter 6) the role of peripheral CCK on intake depression was examined by a dose-response study utilising the CCK antagonist, loxiglumide. Intravenous injection of 5, 10 or 20 mg/kg LW of loxiglumide to infected lambs 10-15 minutes before feeding (n = 6) had no effect on feed intake at any of the dose levels. In experiment 4 (Chapter 7) loxiglumide was infused intravenously for 10 minutes (30 mg/kg/h) before feeding and for the first 2 h (10 mg/kg/h) after feed was offered to minimise any effect of the rate of clearance of loxiglumide on the lack of feed intake response. As well, the rate of marker disappearance from the abomasum was recorded in both infected and non-infected animals. Continuous infusion of loxiglumide did not attenuate parasite induced intake depression nor did it have any effect on abomasal emptying. Abomasal volume was reduced by infection (66.3 vs 162 ml) as was the fractional outflow rate (2.2 vs 2.8 ml/min) but these differences were accounted for by the lower level of feed intake in the infected animals. In Experiment 5 (Chapter 8) brotizolam, a benzodiazepine appetite stimulant, thought to act on the hypothalamus, was administered in a dose-response study to infected and non-infected animals (n = 4) immediately prior to feeding or following termination of the first meal (45 minutes after feeding) and the feed intake response recorded. Brotizolam elevated both the short term (0-0.75 h), daily (22 h) intake and all time intervals in the first 5 h after feeding in infected and non-infected animals when administered after the first meal but when administered prior to feeding elevated intake only over the first 6 h of feeding. In both cases the magnitude of the response was greater in infected animals than in non-infected animals. Brotizolam appeared to increase the rate of eating without having a major impact on meal eating patterns when administered before feeding. Where administration was after the first meal, the effect was due to an "extra" meal being consumed. These findings showed that infected animals can respond to central stimulators of intake although the mechanism of the response is not known. Opioids were implicated in intake depression as the rate of intake rather than meal patterns appeared to be the major parameter depressed under parasitism. This was examined in experiment 6 (Chapter 9) where animals (n = 6) were fasted for 26 h or not fasted, then treated with saline (control), brotizolam (intake stimulant) or naloxone (opioid antagonist) immediately prior to feeding. Fasting stimulated feed intake in the short term (100 % increase in 75 min) and over the day (12 % increase) in both infected and non-infected animals. Following fasting, infected animals ate a similar amount of feed to the non-infected, fasted animals and more than the non-infected, non-fasted animals. The signals resulting from a one day fast were sufficient in the short term to override parasite induced mechanisms causing feed intake depression. Naloxone suppressed the intake stimulatory effects of a 26 h fast in both infected and non-infected animals, which supports a role for endogenous opioids as hunger signals. Where animals were not fasted, naloxone reduced intake only in the non-infected animals which suggested endogenous opioid levels may be lower in infected animals than in non-infected animals. In the final experiment (Experiment 7, Chapter 10) the role of central hunger and satiety mechanism were investigated. Infected and non-infected animals (n = 6) were treated with naloxone or saline by intravenous injection, or saline and met-enkephalinamide (an opioid analogue) by intracerebral infusion, or naloxone and the opioid analogue simultaneously to investigate the role of central opioids in feed intake depression. To determine the role of CCK induced satiety signals on feed intake at a central level, loxiglumide and CCK were infused separately and in combination for 30 minutes prior to feeding and for the first 60 minutes of feed on offer, into a lateral cerebral ventricle of the brain of infected and control animals (n = 6). The opioid analogue tended to increase intake in infected animals but the effect was not significant probably because the dose used was too low to elicit a response in sheep. Naloxone depressed intake only in the infected animals, which conflicted with the results of Experiment 4. As a consequence these results were inconclusive because of the single low dose of opioid analogue used and the conflicting naloxone responses. CCK alone depressed intake by 39-52 % only in infected animals and this effect of the 90 minute infusion was evident over the 8 h short term recording period. Loxiglumide attenuated the feed intake depressive effects of CCK in the infected animals to the extent that intake was elevated above control levels. Loxiglumide alone was an intake stimulant in both infected and non-infected animals. Intake was increased over the entire 8 h but mostly in the second hour when intake was increased by 188 % in infected animals and by 16 % in the non-infected animals and resulted in almost continuous eating. These results showed loxiglumide will temporarily block the effect of parasite infection on feed intake in sheep when administered centrally and the fact that it blocked the effects of exogenous CCK on intake indicated that the effect is mediated via CCK receptors. In conclusion GIT parasite infection reduced both short term and daily feed intake apparently by a change in rate of intake rather than any alteration in meal patterns. It was further suggested that anyone of a number of potential peripheral pathways, including changes to osmolality, gut emptying, pain and inflammation of the gut, alone is not involved in anorexia in sofar as the compounds used could block these factors and the results support the idea that intake depression is mediated via a central mechanism. Intake in infected animals responded to a much greater extent when fasting, i.c.v. loxiglumide or brotizolam were employed. Feed intake thus appears to be regulated through the same mechanisms in infected and non-infected animals. The results from compounds affecting the central mechanism suggest central CCK receptors are important in parasite induced anorexia, possibly by changing the onset of satiety or by interacting with endogenous opioids to reduce the rate of feed intake. Secondly reduced endogenous opioids may be causing the reduction in the rate of feed consumption alone or as a result of other interactions. It was concluded that intake in parasitised animals could be increased to that of control animals by employing procedures and compounds thought to act on the hypothalamus.

Footrot is a contagious hoof disease of ruminants. It is endemic in New Zealand and throughout sheep and goat farming regions of the world. The disease results from a mixed bacterial infection, but the essential agent is Dichelobacter nodosus, a Gram-negative, anaerobic bacterium that possesses type-IV fimbriae on its surface. Genetic variation in the fimbriae of D. nodosus was investigated in this study. Using the polymerase chain reaction (PCR), the variable region of the gene encoding the fimbrial subunit (fimA) was amplified from bacterial DNA extracted from footrot lesions. Different fimA amplimers were differentiated by single-strand conformation polymorphism (SSCP) analysis. In conjunction with DNA sequencing, 15 unique sequences of D. nodosus fimA were obtained from 14 footrot samples taken from 6 farming regions throughout New Zealand. When these sequences were compared to fimA of known serogroups, it revealed that there were at least 15 D. nodosus strains, representing 8 serogroups, present on New Zealand farms. The predominant serogroup was B which contained 6 strains, followed by serogroups F, H and G. No strains from serogroups D and I were detected in this investigation. Twelve out of the 15 New Zealand D. nodosus strains had fimbriae different to those previously reported and the presence of multiple strains on a single hoof was common (86% of samples). The fimA sequences from the 12 D. nodosus strains incorporated into the footrot vaccine currently available in New Zealand were determined. A primer set targeting the relatively conserved fimA regions and based on the published sequence of serogroup M Nepalese isolates (designated M-Nep), failed to amplify fimA from the vaccine serotype M strain (designated as M-SPAHL). When the downstream primer was substituted with a primer that was specific for other serogroups of D. nodosus, the fimA gene was successfully amplified. Cloning followed by DNA sequencing, revealed that M-SPAHL fimA was different to M-Nep fimA. The predicted amino acid sequence of M-SPAHL fimA did not show homology to any known serogroups or serotypes. The most similar sequence was from serotype F1, and not M-Nep. The sequence difference between M-SPAHL and M-Nep was larger than that expected within a serogroup. The consequences of serological relatedness and sequence dissimilarity are discussed. Only eight of the 15 New Zealand field strains had fimbriae identical to those of the vaccine strains, while the remaining seven strains possessed different fimbriae. In addition, the vaccine contained two more D. nodosus strains, representing two sera groups, that were not found on the New Zealand farms investigated in this study. This may, to some extent, explain why the current footrot vaccine is at times less efficient in New Zealand. Another 17 footrot samples were screened for new or additional D. nodosus strains. Two PCR amplimers (designated X and Y) derived from footrot samples generated SSCP patterns different to those of previously identified strains. DNA sequencing revealed that these two fragments possessed novel sequences. The upstream of X (nt 1-183) was identical to serotype M1 while its downstream (nt 223-414) was identical to serotype F1; the upstream of Y (nt 1-116) was identical to serotype E1 whereas its downstream (nt 148-423) was identical to serotype F1. A 14-mer sequence consisting of two partially overlapping Chi-like sequences, 5'-GCTGGTGCTGGTGA-3', was also found in these fragments. Two primer sets with the downstream primer specific for serotype Fl and the upstream primer specific for serotype M1 or E1, produced PCR products of the expected sizes from the footrot samples from which fragments X and Y were isolated, respectively. These primer sets did not appear to amplify artificially mixed genomic DNA from serotypes M1 and F1 or E1 and F1. However, when the reactions were re-amplified, PCR recombination artefacts were observed, suggesting that PCR recombination does occur, but at a low frequency. It therefore seems more likely that fragments X and Y reflect genuine fimA sequences of D. nodosus which have resulted from in vivo DNA recombination, than from a PCR recombination artifact. The genetic capability for recombination at the fimbrial subunit locus may therefore endow D. nodosus with the ability to alter its antigenic appearance. D. nodosus strains present in footrot lesions can be genotyped using a PCR-SSCP/sequencing technique. However, this typing technique requires cloning and screening of D. nodosus fimA sequences, which is both laborious and costly. A rapid molecular typing system for D. nodosus was therefore developed in this study. A close examination of available D. nodosus fimA sequences revealed regions that appear to be specific for serogroups and serotypes. These regions were used to design a panel of sequence-specific oligonucleotide probes (SSOPs), and a rapid and accurate D. nodosus typing system using PCR and reverse dot-blot hybridisation (PCR/oligotyping) was subsequently developed. The variable region of D. nodosus fimA, amplified and labelled with digoxigenin (DIG) in a single multiplex PCR amplification, was hybridised to a panel of group- and type-specific, poly-dT tailed oligonucleotides that were immobilised on a nylon membrane strip. A mixture of positive control poly-dT tailed oligonucleotides was also included on the membrane. After hybridisation the membrane was washed to a defined specificity, and DIG-labelled fragments that had hybridised were detected. The specificity of the oligonucleotides was verified by the lack of cross-reactivity with D. nodosus fimA sequences that had a single base difference. DNA from 14 footrot samples previously genotyped by PCR-SSCP/sequencing, was assayed using the PCR/oligotyping technique. All types of D. nodosus which had been detected previously with a PCR-SSCP/sequencing method were detected by this procedure. However, for three of the 14 footrot samples, PCR/oligotyping detected additional types of D. nodosus. Further PCR amplification using type-specific primers, confirmed that these types were present in the original footrot samples. These results indicate that PCR/oligotyping is a specific, accurate, and useful tool for typing footrot samples. In combination with a rapid DNA extraction protocol, D. nodosus present in a footrot sample can be accurately genotyped in less than two days. Individual animals from the same farm, or the same paddock, were often infected by different strains of D. nodosus. This suggests a host role in mediating footrot infection, or that the interaction between the pathogen and the host is important. In order to better understand the interaction between the bacterium and the host, two polymorphic ovine class II MHC genes DQA1 and DQA2, which have been previously shown to be important in footrot infection, were also investigated in this study. PCR-SSCP/sequencing analysis of the DQA1 locus revealed ten unique ovine DQA1 sequences, with five of them being newly identified. This increases the number of known ovine DQA1 alleles from 8 to 13 (including a null allele), implying a high level of polymorphism at the ovine DQA1 locus. D. nodosus present on 20 footrot infected sheep from the same flock were genotyped, together with the ovine DQA1 and DQA2 genotypes of their hosts. Preliminary results showed that sheep with the same DQA1 and DQA2 genotypes tended to be infected by similar types of D. nodosus. Different types of D. nodosus were generally found on sheep with different genotypes at either the DQA1 or the DQA2 locus. This suggests the diversity in D. nodosus infection may be associated with the heterogeneity in the host MHC. However, as only a small number of animals from the same sire were analysed, further investigation is needed to gain a better understanding of the interaction between D. nodosus and the host MHC.

Content removed due to copyright restrictions: Okeoma, C. M., Stowell, K. M., Williamson, N. B., & Pomroy, W. E. (2005). Neospora caninum: Quantification of DNA in the blood of naturally infected aborted and pregnant cows using real-time PCR. Experimental Parasitology, 110(1), 48-55. Okeoma, C. M., Williamson, N. B., Pomroy, W. E., Stowell, K. M., & Gillespie, L. M. (2004). Isolation and molecular characterisation of neospora caninum in cattle in new zealand. New Zealand Veterinary Journal, 52(6), 364-370. Okeoma, C. M., Williamson, N. B., Pomroy, W. E., Stowell, K. M., & Gillespie, L. (2004). The use of PCR to detect neospora caninum DNA in the blood of naturally infected cows. Veterinary Parasitology, 122(4), 307-315. Okeoma, C. M., Williamson, N. B., Pomroy, W. E., & Stowell, K. M. (2004). Recognition patterns of neospora caninum tachyzoite antigens by bovine IgG at different IFAT titres. Parasite Immunology, 26(4), 177-185.
The objective of this research was to investigate neosporosis in New Zealand cattle using experimental and molecular tools. The research also aimed to isolate and characterise an indigenous New Zealand isolate of Neospora caninum. A series of discrete projects were conducted to achieve the set objectives. A pilot study was first conducted and a wild-type strain of non-cytopathic bovine viral diarrhoea virus (BVDV) type 1 virus was isolated in vitro from a persistently infected heifer. The isolate was used to challenge heifers and the effect of experimental BVDV infection on heifers naturally infected with N. caninum was investigated. Results showed that heifers that were both BVDV and N. caninum seropositive produced 44.4% (8/ 18) damcalf pairs that were both BVDV and N caninum seropositive. Serologically, 66.7% (12/18) dam-calf pairs were seropositive to N. caninum antibodies, while 80% (8/10) dam-calf pairs were BVDV seropositive. A Polymerase Chain Reaction (PCR) study was also conducted and N. caninum DNA was detected in the blood of naturally infected aborting and pregnant heifers. Real-time quantification of N. caninum DNA in the blood of infected heifers showed a decrease of N. caninum DNA after abortion in the aborting group and an increase through gestation in the pregnant group. A study of antigenicity recognised 7 immunodominant (~18, ~25, ~33, ~35~36, ~45~46, ~47 and 60-62 kDa) and 5 minor antigens of N. caninum by cow sera. Three isolates of N. caninum (NcNZ 1 ,NcNZ 2 and NcNZ 3) were isolated from the brains of an infected cow, her calf and a stillborn calf. These isolates were confirmed as N. caninum by PCR, immunofluorescence antibody test and immunohistochemistry and were pathogenic to BALB/c mice.

Flavour is a factor that has a large influence on meat quality. Pastoral flavour that results from the grazing of pasture is an undesirable characteristic of meat flavour for consumers more accustomed to meat produced by grain and concentrate feeding systems. In New Zealand there is a reliance on grazing systems for sheep meat production, however the resulting meat flavour is one factor that impedes the increase of sheep meat exports to discerning markets. Correlation of chemical analyses to sensory evaluations of sheep meat has identified that a high concentration of indole and skatole in the fat is associated with pastoral flavours. Indole and skatole are formed in the rumen from the microbial fermentation of tryptophan. New Zealand pasture is high in protein, which is both highly soluble and rapidly degraded in the rumen. As such, pasture diets provide a rich and ready source of tryptophan for the formation of indole and skatole in the rumen. Condensed tannins are known to slow the degradation of protein in the rumen. Therefore, one of the objectives of this study was to establish if dietary condensed tannin can reduce the ruminal biogenesis of indole and skatole and consequently, ameliorate pastoral flavour in sheep meat. White clover usually comprises up to 30% of the botanical composition of pastures in New Zealand, is highly degradable in the rumen and likely to result in a high availability of tryptophan in the rumen for conversion to indole and skatole. Therefore, another objective of this study was to determine if feeding white clover gave a significant increase in the formation of indole and skatole in the rumen compared to perennial ryegrass and if this has an effect on pastoral flavour in meat. These hypotheses were tested using a series of in vitro rumen fermentations that incorporated the use of fresh forages (Chapter 3 and 6). In vivo experiments were utilised to assess rumen formation of indole and skatole with different forages (Chapter 4) and to assess effects of dietary condensed tannin (CT; Chapter 5 and 7). Meat and fat samples from lambs used in Chapters 5 and 7 underwent sensory evaluation to determine if forage or CT treatments were having an effect on the fat odour or meat flavour. From the in vitro and in vivo experiments of (Chapter 3, 4, 6 and 7) it was calculated that the formation of indole and skatole with perennial ryegrass is generally only 6-41% of that formed with white clover. A higher concentration of indole and skatole was also observed in the blood plasma of lambs that were fed white clover compared to those that were fed perennial ryegrass (Chapter 7) and white clover gave an overall more intense flavour in the meat. Comparison of forages fermented in vitro (Chapter 3) showed that with forage legumes of a higher CT concentration, such as Lotus pedunculatus (98 gCT kg-1 DM) and Dorycnium rectum (122 gCT kg-1 DM), the indole and skatole formed was only 7-21% of that formed with white clover. With forages of an intermediate CT concentration such as sulla (Hedysarum coronarium) and Lotus corniculatus the indole and skatole concentration formed was 53-68% of that of white clover. From in vitro rumen fermentation of mixtures of white clover and Lotus pedunculatus it was concluded that the CT in Lotus pedunculatus was not reacting with the protein in white clover. Fermentation of fresh white clover in the presence of an increasing concentration of added CT extract showed that at a higher CT, indole and skatole formation were reduced to low levels. It was inferred that this was due to optimal protein binding and the availability of free condensed tannin to bind other sources of protein, including rumen microbes. However, in vivo dosing with a CT extract resulted in only a small reduction in rumen indole and skatole concentration. This indicated that when CT was dosed into the in vivo rumen of lambs fed fresh forages the CT probably passed from the rumen before adequate protein release from the forage had taken place. Thus, in the grazing situation it will be optimal to provide CT in planta to maximise protein binding and this, in combination with the high CT concentration needed (approximately 80 gCT kg-1 DM), makes Lotus pedunculatus or Dorycnium rectum the prime candidates for further grazing trials into pastoral flavour amelioration using CT forages. Grazing Lotus corniculatus (40 gCT kg-1 DM) in a field experiment resulted in a lower rumen and blood plasma and fat concentration of indole and skatole in comparison to the grazing of perennial ryegrass/white clover pasture. However, a change in the pastoral odour of the fat was not perceived by the sensory panel when comparing fat samples from lambs that had grazed Lotus corniculatus and perennial ryegrass/white clover pasture. The concentration of skatole in the body fat was less variable in the lambs that had grazed Lotus corniculatus and resulted in no lambs with a high outlying concentration (>100 ng g-1) of indole and skatole. This finding holds some potential for reducing pastoral flavour for consumers sensitive to high indole and skatole concentration in the fat. When condensed tannin was dosed to lambs that were fed white clover or perennial ryegrass in the form of a grape seed extract the intermittent supply of CT slightly reduced indole and skatole formation in the rumen and reduced the plasma concentration of indole and skatole. Flavour assessment of meat from the lambs fed white clover or perennial ryegrass with or without CT suggested that CT reduced the intensity of pastoral flavours. However, there were minimal effects on indole and skatole concentration in the body fat. It was possible that other pastoral flavour related compounds derived from the degradation of amino acids, in addition to indole and skatole that were measured, were having an effect on the meat flavour. It was concluded that dietary condensed tannin is able to reduce the formation of indole and skatole in the rumen and can alter the sensory attributes of sheep meat including reducing pastoral flavours. A higher CT concentration present within the forage plant (approximately 80 g kg-1 DM) will be best to minimise indole and skatole formation in the rumen and reduce pastoral flavours in the meat. Further research is required to confirm this in the grazing situation. Feeding white clover results in a greater rumen biogenesis of indole and skatole compared to perennial ryegrass and therefore, may be the primary contributor to pastoral flavours when ruminants graze conventional pastures. Further research is required to evaluate the flavour attributes that result from feeding white clover to meat producing ruminants in the New Zealand grazing situation.

Abstract This book contains a series of chapters reviewing the current scientific knowledge on RNAi, methods for developing RNAi systems in transgenic plants and a range of applications for crop improvement, crop production and crop protection. Some chapters examine both endogenous systems in transgenic plants and exogenous systems where interfering RNAs are applied to target plants, pests and pathogens. The biosafety of these different systems is examined and methods for risk assessment for food, feed and environmental safety are discussed. Finally, aspects of the regulation of technologies exploiting RNAi and the socioeconomic impacts of RNAi technologies are discussed.

Abstract This book contains 19 chapters on the application of animal nutrition science, including nutrients and important feed constituents and their functions, drinking water, feed digestion, feed digestibility, feed nutritive value, animal feeds, feed intake, nutrient requirements, ration formulation, nutritional models, feed additives, feed-borne pathogens/toxins/nutrient deficiencies, feed-related non-infectious diseases, grazing behaviour, grazing management, assessing nutritional status and nutrient supplements for grazing animals, feed storage and handling, feed processing and the environmental impact of animal production. It is intended for undergraduates taking courses in animal nutrition, farmers and advisors who want to broaden their understanding of animal feeding and management and scientists who would like to see how their research interests integrate into practical animal feeding.

Abstract This book contains 12 chapters focusing on the current trends in sweet cherry production, cherry flowering, fruiting and cultivars, sweet cherry rootstocks, planning a new cherry orchard, orchard establishment and production, the fundamentals of sweet cherry pruning, various sweet cherry training systems, management of the orchard environment, fruit ripening and harvest and management of orchard pests, pathogens and disorders. The promising future of cherry production is also discussed.

Our capacity to maintain world food production depends heavily on the thin layer of soil covering the Earth's surface. The health of this soil determines whether crops can grow successfully, whether a farm business is profitable and whether an enterprise is sustainable in the long term. Farmers are generally aware of the physical and chemical factors that limit the productivity of their soils but often do not recognise that soil microbes and the soil fauna play a major role in achieving healthy soils and healthy crops. Soil Health, Soil Biology, Soilborne Diseases and Sustainable Agriculture provides readily understandable information about the bacteria, fungi, nematodes and other soil organisms that not only harm food crops but also help them take up water and nutrients and protect them from root diseases. Complete with illustrations and practical case studies, it provides growers and their consultants with holistic solutions for building an active and diverse soil biological community capable of improving soil structure, enhancing plant nutrient uptake and suppressing root pests and pathogens. The book is written by scientists with many years' experience developing sustainable crop production practices in the grains, vegetable, sugarcane, grazing and horticultural industries. This book will be useful for: growers, consultants, agronomists and soil chemists, extension personnel working in the grains, livestock, sugarcane and horticultural industries, professionals running courses in soil health/biological farming, and students taking university courses in soil science, ecology, microbiology, plant pathology and other biological sciences.

The types of damage caused by wildlife are many and varied, and can be costly and far-reaching. Until now, there has been little effort to identify and evaluate generalities across that broad range of species, methods and topics. Wildlife Damage Control promotes principle-based thinking about managing impact. It documents and discusses the key principles underlying wildlife damage and its control, and demonstrates their application to real-life topics – how they have been used in management actions or how they could be tested in the future. It synthesises the wide but diffuse literature dealing with the impacts of vertebrate pests and encourages readers to adopt a more theoretical framework for thinking about pest impacts and ways to manage them. The book is organised around key principles that apply across species, rather than looking at individual species, and is damage-based not pest animal-based. Within each chapter there are exercises designed to help readers learn and evaluate key principles. Conservation biologists, ecologists and others involved in wildlife management will find the sections covering principles in biodiversity conservation, of production such as agriculture, and in human and animal health of real value.

AbstractThe threat of climate change and global warming is gaining worldwide recognition. The African continent, because of its size, diversity, and its new status as a “hub” of livestock production, need to gear up to mitigate the possible impacts of climate change on animal health. The aim of this review article is to summarize the current state of knowledge regarding the influence of climate and climate change on the health of food-producing animals. Depending on its intensity and duration, heat stress may directly affect livestock health by causing metabolic disruptions, oxidative stress, and immune suppression, causing increased disease susceptibility, and death. Animal health could also be affected by emergence and re-emergence of vector- and non-vector-borne pathogens that are highly dependent on climatic conditions. The response to these challenges requires community participation in the adaptation of animal production systems to new environments and strengthening the efficiency of veterinary services delivery combined with well-coordinated public health services, since many emerging human diseases are zoonotic.

Maize is one of the world’s most widely grown and consumed cereal. It is known for its multipurpose use; it provides food and fuel to humans, feeds to animals and used as raw material in manufacturing industries. Globally, maize production is a large and significant market which produced 1,116.41 million tons in year 2020 and it’s expected to increase by 1.57% in year 2021. Pests and disease of maize cause significant damage to maize thereby reducing its’s yield and quality. There are many methods of controlling maize disease and pests; they include cultural, biological and chemical methods etc. Recent research studies have discovered an alternative agricultural practices that are sustainable and safe as compared to chemical control of pests and disease. However, biological control has gained large acceptance and its believed to yield positive outcome as compared to chemical control. Various microorganisms are used to control pathogens of maize and thus, there is a need to understand better their interactions with plants. Furthermore, microorganism known as entomopathogens are used to control arthropods. They are biopesticides that play integral role in Pest Management. This section focuses on microbiological control of pathogens and arthropods, their mechanisms of action, applications and the future of entomopathogenic microorganisms and microbiological control of pathogens.

The Climate Indicators for Agriculture report presents 20 indicators of climate change, carefully selected across multiple agricultural production types and food system elements in the United States. Together, they represent an overall view of how climate change is influencing U.S. agriculture and food systems. Individually, they provide useful information to support management decisions for a variety of crop and livestock production systems. The report includes multiple categories of indicators, including physical indicators (e.g., temperature, precipitation), crop and livestock (e.g., animal heat stress), biological indicators (e.g., pests), phenological indicators (e.g. seasonality), and socioeconomic indicators (e.g., total factor productivity).