A large-scale experiment using Hi-sex hybrid and J-line Leghorn-type layers was carried out. After rearing under standard management and dietary procedures, birds were housed at 16 weeks in individual cages of a battery unit. The Hi-sex birds were allocated to nutritional treatments thought to be capable of influencing bone metabolism - oystershell (to contribute 50% of dietary calcium), fluoride (200 mg/kg), ascorbic acid (300 mg/kg), 1,25(OH)<SUB>2</SUB>D<SUB>3</SUB> (5 μg/kg), low crude protein + high vitamin K (150 g/kg + 20 mg/kg), low phosphate (4.5 g/kg) plus a control treatment. Two further treatments included a group of Hi-sex birds photo-stimulated to start laying early, and the J-line birds to provide a low production rate strain comparison. Egg records were collected on a daily basis. Blood samples were taken quarterly for analysis of plasma total calcium (Ca), inorganic phosphate (Pi), and alkaline phosphatase activity (AP). Birds were killed after one year in lay, and bone samples (free thoracic vertebra; FTV, and proximal tarsometatarsus; PTM) representative of the axial and appendicular skeleton taken. Wings were also removed for X-ray. There was no effect of treatment on egg production amongst the Hi-sex birds. The J-line birds laid significantly fewer eggs. Fluoride significantly increased plasma Ca, P and AP. Oystershell increased plasma AP. The low crude protein + high vitamin K increased plasma P. Low dietary phosphate and early lighting increased plasma AP. The J-line birds had significantly lower AP activity compared with the control Hi-sex group. Image analysis of bone sections revealed that strain influenced the degree of osteoporosis more than nutrition. J-line birds had more trabecular (load-bearing) bone than any of the Hi-sex birds. Within the Hi-sex birds, oystershell and fluoride significantly increased the amount of medullary bone (labile calcium source) in the PTM only.

This thesis concerns an investigation of the ability of sheep to withstand cold. It includes studies of the initial cold resistance, the ability to acclimatize to cold, and of the variation within and between breeds of sheep. The cold resistance of shorn Scottish Blackface, Southdown and Welsh Mountain sheep, equal numbers on high or maintenance levels of nutrition, was measured by the rate of decline of rectal temperature under acute cold exposure (-20°C; 4 m.p.h. wind). Their ability to acclimatize to cold was determined by the effect of three types of cold exposure on subsequent cold resistance. These were; 2 weeks at a moderately subcritical temperature (+8°C), up to 8 hrs. acute exposure, or a combination of the two. Associated physiological responses such as changes in skin temperature, heart rate, respiration rate and skinfold thickness were also measured. Cold resistance was greatest in the Blackface and least in the Welsh sheep. The mean rates of decline of rectal temperature were 0.6}6, 1.105 and 1.791 °C/100 min. exposure for Blackface, Southdown and Welsh sheep respectively. High plane sheep had greater cold resistance than low plane, but there was no evidence for interactions between breed and nutrition. There was considerable variation between individuals within breeds; coefficients of variation ranged from 25% to 66%. Individual repeatability of performance was high. The cold resistance of all breeds was increased by previous exposure to +8°C, while an increase in cold resistance as a result of acute cold exposure alone was clearly shown by the Blackface sheep. These findings indicated that sheep could acclimatize to cold. Blackface sheep had a much greater capacity for acclimatization than either Southdown or Welsh sheep. The mean rates of decline of rectal temperature were 74%, 19% and 32% slower respectively after acclimatization. In general both high and low plane sheep showed similar amounts of acclimatization. There was some inconclusive evidence for breed x nutritional interactions in ability to acclimatize. It was concluded from indirect evidence and by analogy with previous work on rodents that acclimatization probably resulted from an enhanced capacity of the sheep to maintain high rates of metabolism under cold exposure, while in Blackface sheep a slight change in the site and efficiency of heat production involving a reduction in shivering thermogenesis may also have contributed. Prolonged exposure to +8°C caused an elevation in rectal and skin temperatures and in heart rate when subsequently measured at a thermoneutral temperature. Rectal temperatures were, on average, 0.15 C higher, ear and foot temperatures 3.2 C and 2.5 C higher respectively, while heart rates increased by 40-50%. This evidence implied a considerable increase in the basal metabolic rate. Vasomotor responses under subsequent acute cold exposures were delayed. Vasoconstriction occurred, on average, 4°C and 7°C later respectively in the ears and feet. Acute cold exposure appeared to have a similar effect on basal metabolism. Sheep kept at moderately sub-oritical temperatures for long periods of time allowed, on average, a reduction in body temperature of 0.4 C. This was also shown during initial stages of acute cold exposure. The increase in cold resistance and the associated responses appeared to have slightly different properties. Both were induced by prolonged exposure to +8 C or by acute cold exposure, but apparently only the increased resistance to body cooling was able to persist without continuous low temperature stimulation. Evidence for acclimatization was also found in new born lambs. Lambs born and reared for 2 weeks at 0°C maintained a rate of fall of rectal temperature 30% slower during acute cold exposure than comparable lambs which had been kept at +25 C. The relevance of these findings to sheep in their natural environment and to climatic studies in the laboratory was discussed. The vasomotor responses of Blackface, Southdown and Welsh sheep under mild cold exposure in full fleece were also compared. In general, estimates of the critical temperature, defined as the ambient temperature obtaining immediately after vasoconstriction of both extremities, were in good agreement with those of other workers who used calorimetric determinations. These were +1 C, +3 C and +7 C for the Blackface, Southdown and 7'elsh sheep respectively. Estimates for high plane 3heep were generally 2°C lower than those for comparable low plane sheep. Southdown sheep, by comparison with the two hill breeds, appeared to have a rather low critical temperature relative to their fleece length, wool weight per unit area and bodyweight. This was thought to be due to their more comprehensive fleece cover on the face, ears and feet. It was suggested that vasomotor responses may be useful indices of variation in critical temperature within breeds but their validity in comparisons between breeds seems questionable when the sheep are unshorn.

Foot-and-mouth disease (FMD) is endemic in Kenya where serotypes A, O, SAT1 and SAT2 are frequently encountered. Despite the importance of the dairy industry and the frequent reporting of disease, the epidemiology of FMD and field-based vaccine effectiveness has been poorly described in these endemic settings. Additionally, the disease impact has been inadequately characterised, despite the importance of such information when allocating scarce resources for animal health in national disease control strategies. The objectives of this doctoral thesis were to gain field experience of FMD in endemic settings and to use appropriate outbreaks to assess the vaccine effectiveness, gather evidence to optimise the use of vaccines and inform national policy, and to estimate disease impact. Outbreaks on two large-scale dairy farms located within Nakuru County, Kenya, were investigated and detailed descriptions of the outbreaks are presented. Both farms regularly used locally produced, aqueous adjuvanted, non-NSP purified quadrivalent (A, O, SAT1, SAT2) vaccine every 4-6 months. The first attended outbreak was caused by serotype SAT2 and evidence was found of limited or no vaccine effectiveness. At the second outbreak, due to serotype O, there was evidence of increasing protection with increasing number of doses. The reasons behind the vaccine poor effectiveness are discussed and are likely to include poor match with the field strain and inappropriate schedules in youngstock. Virus neutralisation test data were made available from the vaccine manufacturer who sample animals on farms using routine prophylactic vaccination. The influence of maternally derived antibody on the response to vaccination was investigated with these data and recommendations on vaccine schedules and future research priorities are made based on the evidence presented. On the farm that had SAT2, analysis of the disease impact was performed using individual animal data. Longitudinal analysis of individual milk yields utilising generalised estimating equations and an autoregressive variance structure to account for the correlation of yields for individual animals was performed. Predictions of 305-day milk yields were made based on previous lactations in the same herd. Despite a clear herd level impact, no difference was found between recorded clinical FMD cases and non-cases. More detailed analysis revealed significant reductions among older animals in earlier stages of lactation but younger cows were able to recover sufficiently so that no overall impact was seen. The impact of clinical disease on the rate of clinical mastitis and culling was analysed utilising a historical cohort approach with survival analysis over a 12-month period after the commencement of the outbreak. Hazard ratios (HR) were generated using Cox regression accounting for nonproportional hazards by inclusion of time-varying effects. There was good evidence of an increased rate of mastitis in the first month after the onset of the outbreak (HR=2.9, 95%CI 0.97-8.9, P=0.057) although the effect on culling was less clear. The implications of these findings for policy and further research are discussed.

Feline coronavirus (FCoV) infection is ubiquitous in multicat households in the UK. In the majority of cases, the infected cat remains healthy but a small percentage of cases develop the fatal disease of feline infectious peritonitis (FIP). This thesis describes the identification of genomic mutations that may account for the difference between the virulent and avirulent forms of FCoV. Complete FCoV genome sequences were obtained from two pairs of FCoV infected siblings, in which one of each pair died due to FIP whilst the other remained healthy. Virus-specific oligonucleotide primers were used to convert and amplify the FCo V genome RNA from each sample into cDNA fragments, which then underwent next generation sequencing. The de novo assembled genomes were compared and nucleotide differences between the genomes were identified. Thirty two nucleotide differences, which may be related to the development of FIP, were observed between the first pair of samples. The second pair of samples were found to represent only distantly related FCoV genomes. Recent evidence has suggested that one of the amino acid changes identified in this study, a methionine to leucine substitution at position 1058 in the spike protein may be associated with the development ofFIP. However, pyrosequencing analysis of a collection of well-defined clinical samples led to the conclusion that this amino acid change is linked to the tropism of the virus, rather than its ability to cause FIP. Finally, an initial step was taken towards exploring the host response to FCoV infection by comparing the levels of cellular transcripts between infected and mock infected feline cell lines. The experiments described in this thesis will help further our understanding of the roles played by the virus and the host in the pathogenesis of FCoV infections.

This PhD aimed to test and identify existing and new strategies that can be used by key motivators such as vets and farm assurance assessors to spread best practice and promote continuous animal welfare improvement. The first experimental chapter focussed on the development of an online tool for the acquisition of the basics of communication skills. The online tool was aimed at veterinary undergraduates and proved to effectively improve the students' ability to start a consultation, listen actively to the client and display empathy and understanding. The second experimental chapter aimed to identify strategies used by key motivators to promote discussion with animal owners about the welfare of their animals by running facilitated workshops with veterinary undergraduates, farm assurance assessors and staff of re-homing centres. A variety of strategies were identified during the workshops and were later mapped onto the principles behind the spirit of Motivational Interviewing. This was done in order to determine whether it is at all possible to include elements of MI within the aim of spreading best practice amongst animal owners and promoting uptake of animal welfare advice. It was concluded that key motivators do not lack strategies but rather might be in need of ways to implement them. Finally, the last experimental chapter aimed at monitoring a new-style animal welfare assessment that was developed as part of the AssureWel project. The monitoring process was carried out via telephone interviews with both FF and SA producers, some of which had been assessed using the new-style assessment and some of which hadn't. The results indicated that there was not a big variation in responses between those producers that had received the new-style assessment and those that hadn't. Some gaps were also identified with regards to the assessors initiating a discussion with the producers and offering referral for advice from animal welfare advisors Ca role specifically designed for the AssureWel project). The results of the study were fed back to the AssureWel project.

It is now accepted that gut microbiota are crucial for the development of the mucosal immune system. It has been suggested that differences in early life microbial colonisation may be associated with variable predisposition to allergic, auto immune, and inflammatory diseases. The exact underlying mechanisms are difficult to study in human infants, however, the similarities in physiology and nutritional requirements between pigs and humans suggest that piglets can be good models to elucidate the pathways involved. The aim of this PhD project was to investigate how differences in microbiota, early on in life, could affect immune regulation in telms of regulatory T cells (Tregs), a cell type fundamental for immune homeostasis. Manipulation of gut microbiota was attempted using different housing conditions [specific pathogen-free (SPF) facility and farm], birth environment (indoor and outdoor fmm) as well as with administration of antibiotics and specific microbiota inocula (with simple and complex composition). Furthermore, the effect of nutritional interventions, (inulin, starch and medium-chain triglycerides) with the potential to manipulate gut microbiota, was also studied. The effect of these manipulations on small intestinal Tregs was examined using fluorescent immunohistology. Furthermore, activation-induced Foxp3 expressions on gut and blood CD4 T cells was also investigated using flow cytometry. It was observed that indoor-born piglets were more susceptible to a reduction in Tregs when transfened to an SPF facility than outdoor bom piglets, but treatment with antibiotics reduced gut Tregs of outdoor-bom piglets at the level of those born indoor. On the other hand, colonisation of new-bom piglets with a complex microbiota inoculum reduced gut Tregs in comparison to the simple microbiota inoculum. However, none of the nutritional interventions had a significant effect on Tregs. Furthermore, no activation induced expression ofFoxp3 was observed in either gut or blood CD4 T cells of 5-month old piglets. The results of this Thesis suggest that both environment and direct manipulation of gut microbiota can affect levels of small intestinal Tregs, whereas the effect of nutrition is less clear. A more detailed analysis of small-intestinal microbiota is necessary to confirm that these observations are a result of differences in the microbiome between the groups or whether other possible factors are also involved.

A variety of stressors cause hens to delay oviposition and this can result in characteristic eggshell abnormalities which are commercially undesirable. This project examined the duration of stress-induced oviposition delays in medium-hybrid hens and investigated their underlying physiological causation. Social stress (relocation of hens from individual to group cages) was used to induce the oviposition delays. From behavioural observations of stress-induced oviposition delays, it was found that eggs were laid either before a threshold of approximately 3 h delay or after at least 7 h delay. This distinction between short- and long-term delays accounts for different types of eggshell abnormality. As oviposition is associated with ovulation of the subsequent egg, it was important to establish whether stress-induced oviposition delays were a consequence of ovulation delays. From investigations of the stage of formation and position of the subsequent egg in the oviduct, it was concluded that stress can cause short delays in ovulation but this is not associated with all oviposition delays. Oviposition is caused by uterine contractions induced by release into the circulation of ovarian prostaglandins and neurohypophysial arginine vasotocin (AVT). Two possible physiological mechanisms which may account for the stress-induced oviposition delays were examined. First, opioid peptides released in response to stress may inhibit AVT release. Second, adrenaline released in response to stress may directly suppress uterine contractions. Plasma AVT concentration was elevated at the time of delayed oviposition, but not during the delay, and AVT injection rapidly ended delays, thus supporting the hypothesis that delays are caused by inhibition of AVT release. The possible role of opioid release in causation of stress-induced oviposition delays was investigated by treating hens with appropriate receptor antagonist and agonist compounds.

No description available.

Using ewes with an ovarian autotransplant, the diameter of individual follicles and corpora lutea was measured by ultrasound scanning, to characterise the pattern of development of antral follicles over 2.5 mm, in relation to gonadotrophin and ovarian hormone concentrations in jugular and ovarian venous blood. Studies were conducted to investigate the effects of season, age and the action of a major gene involved in increased prolificacy in sheep (Fec<SUP>B</SUP>) on the dynamics of follicular growth and its hormonal regulation. The results showed that the final stages of maturation of dominant follicles in sheep during the oestrous cycle and anoestrus occurs in a succession of waves of follicular growth. During the luteal phase 3 waves emerge on day 2, 7 and 11 post-LH surge. During the follicular phase, most of the follicles that ovulate after the LH surge originate from follicles above 5 mm in diameter at the time of luteal regression, but additional smaller follicles can be recruited during the follicular phase. During the follicular and early luteal phase, when LH pulse frequency is elevated, follicles achieved dominance by secreting large amounts of oestradiol and inhibin A, depressing FSH concentrations below threshold levels. During the second and third wave of follicular development of the luteal phase a similar pattern of FSH secretion was evident but the relationship between the secretion of oestradiol and inhibin A was less clear. Despite these endocrine differences, the mechanism of follicular selection operated in each of these waves as the number of dominant follicles was similar to the ovulation rate. Similar investigations in ewes carrying the Booroola Fec<SUP>B</SUP> gene, showed that gene carrier ewes produce more follicles that mature earlier at smaller size, without any differences in the concentration of FSH and the ovarian secretion of oestradiol, androstenedione and inhibin A compared to non-carrier animals. This suggests that the Booroola gene acts at an ovarian level modulating the gonadotrophin signal to increase the number of follicles selected. In order to study the effect of age in pituitary-ovarian function, the dynamics of follicular diameter were studied in old ewes (12-13 years) with ovarian autotransplants and the results of gonadotrophin and ovarian hormone concentrations compared to those obtained from the same animals 6 years previously.

No description available.