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Three experiments were carried out to assess the energy and protein requirments of single and twin-bearing beef cows during the last three months of pregnancy and also to observe the effects of pregnancy nutrition on the subsequent lactational performance of cows and calves. A wide range of energy level was applied to single and twin-bearing cows. As assessed from body weight change, calf birthweight, milk yield, calf growth rate and blood parameters, it was found that there was no benefit in giving high levels of dietary energy to cows during pregnancy. It was concluded that feeding 50 and 70 MJ ME/day to single and twin-bearing cows respectively together with a high proportion of UDP may be acceptable levels during the latter part of gestation, provided that the cows are in good body condition at the start of the last trimester of pregnancy and they are given adequate nutrition during early lactation. Another three experiments were conducted with pregnant ewes, wethers, pregnant heifers and steers to measure the digestibility and to determine the metabolisable energy value of two mixed diets which differed in rumen degradability of protein. Such diets were used in experiments with pregnant cows. A comparison was made between the digestive capacity in different species and sex of animals. Digestibility co-efficients of two diets, two sexes and two species did not differ significantly. Therefore, it was concluded that metabolisable energy value determined for mixed diets using sheep can be used for cattle. ME value of mixed diets was less than that calculated in these experiments but the extent of the decrease may be acceptable under farm conditions.

One of the reasons for persistence of information security challenges in organisations is that security is usually seen as a technical problem. Hence the emphasis on technical solutions in practice. However, security challenges can also arise from people and processes. We therefore approach the problem of security in organisations from a socio-technical perspective and reason that the design of security requirements for organisations has to include procedures that would allow for the design time analysis of the system behaviour with respect to security requirements. In this thesis we present a computational approach to the verification and validation of elicited security requirements. This complements the existing approaches of security requirements elicitation by providing a computational means for reasoning about security requirements at design time. Our methodology is centered on a deontic logic inspired institutional framework which provides a mechanism to monitor the permissions, empowerment, and obligations of actors and generates violations when a security breach occurs. We demonstrate the functionality of our approach by modelling a practical scenario from health care domain to explore how the institutional framework can be used to develop a model of a system of interacting actors using the action language InstAL. Through the application of the semantics of answer set programming (ASP), we demonstrate a way of carrying out verification of security requirements such that it is possible to predict the effect of certain actions and the causes of certain system states. To show that our approach works for a number of security requirements, we also use other scenarios to demonstrate the analysis of confidentiality and integrity requirements. From human factor point of view compliance determines the effectiveness of security requirements. We demonstrate that our approach can be used for management of security requirements compliance. By verifying compliance and predicting non-compliance and its consequences at design time, requirements can be redesigned in such a way that better compliance can be achieved.