© © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a i _________________________________________________________________________________________________________ Dedication _________________________________________________________________________________________________________ This dissertation is dedicated to those who have supported me during this thesis. My parents, Lisa and Martin Prior, who have been the pillars of support throughout my long years of study. I would not be standing where I am today without your direction and encouragement to fulfil my dreams, "you lose everything when you don't love yourself". My partner, Dr Brittany Fourie, whose unwavering love and kind-heartedness throughout the writing process kept me motivated, "your beauty is undeniable but everything sacred and ancient in you is even more stunning". My friend, colleague, supervisor, Andrew, whose unfaltering patience, wisdom and benevolence throughout the writing process ensured that I always produced nothing but excellence, "your life is captured in a story, the weak trumps the evil villain, your own story should resonate and fill you within. Your story should be providential, not Darwinian". Most importantly and above all else, I thank my heavenly Father for His love and guidance. "For the Spirit God gave us does not make us timid, but gives us power, love, and self-discipline" -Timothy 1:7. This dissertation is in honour of all of you. © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a ii _________________________________________________________________________________________________________ Declaration of Originality/Plagiarism _________________________________________________________________________________________________________ By submitting this dissertation for the degree MSc (Veterinary Science) at the University of Pretoria, I declare that the entirety of the work contained therein is my own original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that reproduction and publication thereof by Pretoria University will not infringe any third party rights, and that I have not previously in its entirety or in part submitted it for obtaining any qualification at this or any other tertiary institution. Declaration of originality attached as appendix (chapter 8). © © U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a iii