Mycoplasmas are responsible for many important diseases of animals, including contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subsp. mycoides SC and calf pneumonia, arthritis and mastitis caused by Mycoplasma bovis. However, diagnostic techniques currently available are laborious and imprecise. The work described in this thesis concentrates on the critical evaluation of existing techniques and the development of improved procedures. The role of antimicrobial resistance in limiting the options for disease control was also considered. Diagnostic methods for the detection of M. mycoides subsp. mycoides SC in clinical material were critically evaluated during a CBPP outbreak in Portugal. Immunoblotting was more sensitive and specific than CFT or ELISA. The polymerase chain reaction (PCR) was more rapid and sensitive than culture. However immunocytohistochernistry (ICC) was far the best test for detecting M. mycoides subsp. mycoides SC antigen in lungs. A rapid latex agglutination test (LAT) to detect CBPP using a carbohydrate extract of M. mycoides subsp. mycoides SC was developed. Analysis of the carbohydrate extract composition demonstrated that fucose, glucosamine and galactose are present in the ratio of 1:2:16 respectively. N-acetyl neuraminic acid was also detected. Evaluation of the LAT with sera from negative, naturally infected and experimentally infected cattle demonstrates that the test clearly differentiates positive and negative CBPP sera. The LAT compared favourably with the CFT but was not as specific as the immunoblotting; however the LAT had the advantage of being more rapid and robust and could be used in the field. Molecular methods including the polymerase chain reaction (PCR) and 16S rRNA gene sequencing were assessed for their potential use in the diagnostic laboratory. A PCR method for identifying M. bovis was adapted, evaluated and introduced as a routine laboratory test. Using a set of universal 16S rRNA gene primers, amplicons of two serologically untypable isolates, one from a peregrine falcon, and the other from an ostrich were obtained. Results imply that the isolates may be new mycoplasma species. The development of antimicrobial resistance has been seen in many microorganisms but little evidence exists for resistance in mycoplasmas. Consequently, the in vitro effect of five antimicrobials; danofloxacin, oxytetracycline, spectinomycin, florfenicol and tilmicosin on 62 isolates of M. bovis and 20 of M. mycoides subsp. mycoides SC was investigated. Nfinimum inhibitory concentrations (MICs) and mycoplasmacidal (MMC) values were determined. Evidence of antimicrobial resistance by M. bovis is shown. The potential for M. mycoides subsp. mycoides SC to develop antimicrobial resistance against spectinomycin in vitro is also demonstrated.

(1). In this thesis the relationship between eggshell quality and bone biology was examined over the laying life of two strains of hen; a highly selected commercial line and the relatively unselected J.Line. (2). The efficiency of using osteocalcin as a marker of osteoid formation, in collaboration with established markers of bone mineralisation and bone resorption, during eggshell calcification was ratified. (3). It was established that magnesium is actively removed from bone hydroxyapatite during resorption and transported to the shell gland pouch for incorporation into the palisade layer of the eggshell. (4). A relationship was demonstrated between hatched eggshell quality and the bone biology of newly hatched chicks. (5). The association between high egg output and poor bone structure was evident in the commercial laying strain hen. No such deficit in skeletal quality occurred in the relatively unselected J.Line. (6). The commercial line demonstrated a significantly higher rate of bone remodelling at late lay concomitant with osteoporosis. (7). The unselected J.Line demonstrated significantly higher rates of bone remodelling throughout lay. It was hypothesised that this was due to a greater propensity for bone upkeep during the inter-egg interval. (8). The provision of a prelay diet influenced neither bone volume nor mineral composition at the beginning of lay. (9). The feeding of a prelay diet led to a longer period of sustained high production and an earlier increase in egg weight. This was accompanied by a delay in the increase in osteoid formation and decreased levels of blood ionised calcium. This led to high "on farm" seconds at late lay due to abnormally high fracture toughness and the Incidence of type B's within the mammillary layer. (10). The reason for the observed decrease in hatchability associated with poorly pigmented eggshells in a commercial guinea fowl flock was related to premature expulsion of the egg. These thinner shelled eggs may have resulted from the process of artificial insemination.

The use of maize (Zea mays) as a co-substrate with cattle slurry for the production of biogas was investigated in detail by running several long term digestion trials under different operational conditions in laboratory scale semi-continuous digesters. These conditions included varying the organic loading rate (OLR) from 2 to 6 g VS l-1 d-1, the proportion of cattle slurry from 25 to 100%, and the recirculating regime. Results indicated that the co-digestion of cattle slurry and maize was viable at all loading rates tested with the greatest volumetric methane yield, 1.46 l l-1 d-1, produced at a 5 g VS l-1 d-1 OLR consisting of 40% cattle slurry; this corresponded to a specific methane yield of 0.26 l g-1 VS added. Successful digestion was shown at retention times as low as 15 days where a volumetric methane yield of 1.26 l l-1 was produced. Co-digestion had a pronounced effect on the volumetric methane yield with improvements of up to 355% when compared to the digestion of cattle slurry alone. Additionally, the OLR could be doubled by the addition of an equal quantity of maize, on a VS basis, with the volumetric methane yield increasing by over 200% without a great loss of the methane potential of the maize. For each trial undertaken in this research the actual methane yield produced from co-digestion was compared to that calculated to be produced. Support for synergy was shown in the first two trials where the actual methane yield exceeded that predicted however, the method used to calculate the predicted yield was suggested to be an inaccurate determination. To address this inaccuracy a trial was designed testing the digestion of the two substrates alone and together under the same operational conditions and methodology. A comparison between the mono and co-digestion trials indicated that the addition of maize to cattle slurry produced a methane yield that more or less equalled that calculated from the sum of the cattle slurry and maize alone. This brought the early indications of synergy into doubt with suggestions that they were the result of an inaccurate determination of the predicted yield and of inhibition washout. In the final part of the research an attempt was made to improve the volumetric methane yield by introducing solids recirculation to the co-digestion process with the objective of maintaining the slowly degradable fraction of the maize and cattle slurry in the digester for longer periods. This proved not to be a viable option with the methane production showing a decline; at an OLR of 5 g VS l-1 d-1, consisting of 50% cattle slurry, a decline of 0.31 l l-1 d-1 occurred. Solids recirculation was also introduced to the mono-digestion process to determine whether the differences shown in the co-digestion trial were a result of recirculating the solids of the cattle slurry, the maize or a combination of the two. Results showed that both substrates produced unstable conditions indicating that the co-digestion trial was not the result of just one substrate failing. Liquid recirculation was also tested on the co-digestion of the substrates and while no decline was observed no improvement was produced. KEYWORDS: Anaerobic digestion, co-digestion, cattle slurry, maize, solids recirculation

In a series of experiments, ewe milk production and associated plasma hormone and blood metabolite status were investigated. Separate comparisons were made between ewes suckling either single (S ewes) or twin (T ewes) lambs, ewes lambing in either January or April, ewes fed either 150 g (low) or 210 g (high) of crude protein/kg DM in the diet and between ewes of the East Friesland (EF) and Scottish Blackface (SBF) genotypes. In all comparisons milk yields, live weight, body condition score changes, fat, protein and ash contents and energy values of milk were determined weekly. Blood samples were collected on one day each week, at 20 minute intervals for 2 hours, prior to feeding. Samples were pooled within each week and each animal. Plasma glucose, non- esterified fatty acids (NEFA), 3-hydroxybutyrate (3-OHB), urea, albumin, protein, insulin, growth hormone (GH), cortisol, prolactin, triiodothyronine (T3) and thyroxine (T4) concentrations were determined. During weeks 2, 4 and 10 (and 14; genotype comparison only) of lactation blood samples were collection at 20 minute intervals for 8 hours and individually assayed for plasma insulin, GH, cortisol and prolactin concentrations. Ewes rearing twin lambs had higher milk yields than those rearing single lambs. This was associated with higher NEFA, 3-OHB, GH and cortisol concentrations and lower insulin concentrations in the plasma of twin-rearing ewes. There were no consistent differences in prolactin or thyroid hormone concentrations of the plasma of single and twin rearing ewes. The decline in milk production with advancing lactation was associated with an increase in the post prandial insulin:GH and insulintcortisol ratios and T4 levels and a decrease in prolactin levels. Feeding was followed by significantly higher insulin levels and slightly higher GH levels Ewes fed the high protein diet had higher milk yields and milk protein contents compared with ewes fed the low protein diet. This, however, was not apparently associated with a higher degree of adipose tissue mobilisation. There were no significant differences between the two protein treatments in any of the plasma hormones measured. Change in milk production with stage of lactation was associated with an increase in the insulin:GH and insulinrcortisol ratios and in circulating T4 levels, and a decrease in plasma prolactin levels. During early lactation, feeding was followed by a rise in insulin and GH levels but during late lactation only insulin levels increased. In contrast to previous observations there was no difference in milk yield or pattern of milk production between the ewes of the EF and SBF genotypes. SBF ewes produced milk of higher fat content compared with EF ewes. All ewes gained similar amounts of live weight throughout lactation. However, plasma albumin and protein levels were lower in EF compared with SBF ewes; plasma insulin, cortisol, prolactin and T3 levels were consistently lower in EF than in SBF ewes. The decline in milk production in late lactation was associated with an increase in the insulin:GH ratio and in T4 levels while prolactin levels decreased. Feeding was followed by increased insulin levels and cortisol levels (EF ewes only) and lower GH levels (during late lactation). The role of these hormones in the control of milk production is discussed and in particular the hormonal inter-relationships in relation to level and pattern of milk production and associated nutrient status throughout lactation.

The aim of this project was to examine the effects of housing on the behaviour of the overwintered lowland ewe, to see which if any aspects of this husbandry practice give rise to changes associated with a reduction in welfare, and where possible suggest changes to housing design and management practices which could alleviate this. To facilitate the discussion of the practical work of this thesis, the role of behaviour in the assessment of welfare is pointed out, illustrating the effects of housing on the behaviour and welfare of other species, along with a brief resume of the nature of sheep housing and the behavioural repertoire of sheep in their natural environment. The practical work was made up of three main parts. These were: 1. A series of studies on sheep kept outdoors inextensive conditions similar to the environment in which sheep are thought to have evolved, in order to establish a basic ethogram and time budgeting for comparison with later indoor work. 2, A series of studies on sheep kept indoors in conditions typical of farm housing in order to establish changes in behaviour which could be associated with a decrease in welfare. 3. A series of studies on sheep kept in pens modified from previous results to establish whether these modifications could alleviate the welfare problems seen. The behaviour of the sheep in extensive conditions was found to be similar to that given in the literature. The main effects of typical housing on their behaviour was a considerable increase in proximity of other sheep, levels of alertness and aggressive competition for resources within the pen, in particular far space to feed and to lie near to a solid barrier or wall. There was also a decrease in time spent feeding and resting seen and in the allelomimicry seen in these activities. These changes are considered indicative of a lack of welfare in housed sheep. By including extra pen edges or walls in the form of solid barriers within the pen and allowing extra space up to 7n2per head many of these welfare problems are alleviated. While there were many restrictions on the practical work of this thesis, a number of recommendations are made concerning the welfare and design of housing for sheep on the basis of these results.

The literature concerning the nutritional content of white clover as a grazed herbage or conserved crop offered to dairy cattle and aspects of frothy bloat are reviewed. In the first nine week change-over design experiment the effect on milk production and behaviour of spring calving dairy cows grazing white clover/grass swards at contrasting sward heights were examined. Grazing the clover/perennial ryegrass sward to a height of 4 cm increased clover content, but reduced milk production. The 8 cm sward increased milk yields by 15.8%. This was accompanied by an increase in fat and protein yields. Grazing time and biting rate were increased on the 4 cm sward. Cows offered choice between sward types produced intermediate milk production values. A second change-over design experiment conducted over 12 weeks examined milk production and behaviour of spring calving dairy cows in early lactation grazing perennial ryegrass or White clover/perennial ryegrass swards alone or offered a choice between the two sward types or grazed on clover/perennial ryegrass during the day and perennial ryegrass at night. The inclusion of clover in the diet of the dairy cows significantly increased milk production, but reduced fat content. Protein content, fat and protein yields were increased. Cows offered a choice or mixed day and night grazing regime produced similar results, which were intermediate between the clover/ryegrass and perennial ryegrass treatments. Grazing time was increased on clover/perennial ryegrass swards. This experiment also 1 demonstrated the ability of cows to adjust their grazing time to maximise herbage intake. The third experiment compared the value in relation to milk production of three different buffer forages fed to spring calving dairy cows in late lactation grazing either clover/ryegrass or ryegrass swards. The forages were ryegrass and ryegrass/clover silages and ryegrass hay. Milk yield and composition were not affected by forage type, but intakes were higher for grass silage for cows grazing clover/ryegrass swards and visa versa. Hay OM intake was low. The final experiment conducted over the first 15 weeks of the grazing season studied the effect of energy:protein concentration of strawmix supplements on the productivity of spring calving dairy cows grazing a high white clover sward. Milk yields were increased by the provision of a strawmix supplement. The energy:protein ratio had a significant effect on milk composition except fat content. The high energy:high protein supplement tended to precipitate ruminal tympany (bloat), while the low energy:high protein supplement tended to reduce ruminal tympany on this clover based sward. These experiments have given some insight into the use of clover and stimulated questions which require further investigation to enable the farmer to safely incorporate clover into dairy farming systems.

Voluntary automatic milking is a system whereby dairy cows can be milked as the cow desires without routine human intervention. Motivation to be milked was studied in a Y -maze and an automatic milking system (AMS). In both motivation to be milked was variable. In the Y -maze some early lactation cows chose to be milked every 31/ 2 hours five times per day, but there was much individual variation. Late lactation cows did not choose to be milked less often than the early lactation cows. When given the choice to be milked or fed concentrate in the Y -maze, early lactation cows always chose to eat. In the AMS mean attendance increased from 1.1 visits/ cow / day when they were not fed concentrate to 2.8 visits/cow/day when they were fed concentrate. The effects of feeding in the AMS on attendance were studied. Feeding concentrate in the parlour had no effect on attendance or the number of milkings. The AMS exit area feed type (where the cows had to visit the AMS to reach the food; either forage or concentrate) however, had a significant effect on attendance (forage: 6.0 visits/cow/day, concentrate: 4.1 visits/cow/day, s.e.d=0.25) but only a small effect on the frequency of milkings (forage: 2.6 milkings/cow/day, concentrate: 2.4 milkings/cow/day, s.e.d=0.06). Feeding forage in the exit area, as opposed to freely available in the bedded area, significantly reduced the total forage feeding time (209 vs 289 minutes/cow/day, s.e.d=33.6), and the number of bouts (4.9 vs 7.9 bouts/cow/day). Feeding cows in the parlour increased the level of shuffling during the automatic teat cup attachment process (6.7 vs. 3.4 shuffles/cow/milking, s.e.d 2.07). There were no other behavioural effects or any effects on their milking characterisitcs. Future automatic milking systems could feed concentrate in the exit area as the lure to attract cows into the system. There is no requirement to feed cows while they are being milked.

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