TABLE OF CONTENTS ABSTRACT..................................................................................................................................... i ACKNOWLEDGEMENTS ............................................................................................................ ii DECLARATION OF INDEPENDENT WORK............................................................................ iii PREFACE ......................................................................................................................................iv ABBREVIATIONS ..........................................................................................................................v LIST OF FIGURES........................................................................................................................vi LIST OF TABLES.........................................................................................................................vii CHAPTER 1: GENERAL INTRODUCTION.................................................................................1 CHAPTER 2: LITERATURE REVIEW ........................................................................................4 2.1 Factors influencing tick infestation in beef cattle.................................................................4 2.1.1 Introduction ...............................................................................................................4 2.1.2 Breed.........................................................................................................................4 2.1.3 Body Weight..............................................................................................................7 2.1.4 Body Condition .........................................................................................................9 2.1.5 Coat type .................................................................................................................11 2.1.6 Skin thickness..........................................................................................................14 2.1.7 Body Temperature ...................................................................................................17 2.1.8 Host age...................................................................................................................19 2.1.9 Cow size..................................................................................................................20 2.1.10 Season .....................................................................................................................21 2.1.11 Vegetation ...............................................................................................................23 2.1.12 Reproduction ...............................................................................................................24 CHAPTER 3: MATERIALS AND METHODS ...........................................................................26 3.1 Study site........................................................................................................................26 3.2 Animals and Management ............................................................................................27 3.3 Statistical analysis..........................................................................................................28 CHAPTER 4: RESULTS AND DISCUSSION............................................................................30 CHAPTER 5: GENERAL CONCLUSION ..................................................................................60 CHAPTER 6: LITERATURE REVIEW .......................................................................................62 APPENDIX A ................................................................................................................................80 Effect of selected physical and production traits on the tick burdens of beef cattle ABSTRACT The objective of this study was to determine the effect of selected traits such as age, sex, body weight, body length and height, body condition score (BCS), coatscore (CS), skin thickness and average skin surface temperature on tick burdens in beef cattle. Bonsmara cattle (n= 143) were used to measure visible tick counts, body condition score, coat score, skin thickness, body height and length, body weight, body surface temperature, gender and inter calving period. Measurements were taken from April to December. All animals were managed extensively on natural and cultivated pastures near George in the Southern Cape. Female animals had significantly (p<0.05) greater tick infestation (37.98±2.7) compared to male animals (16.52±1.2). Age was a significant factor (p<0.001) with the younger animals below two years having (46.40±5.26) more ticks than those of two years and older (20.15±2.44). A significant negative correlation (p<0.001; -0.29) was reported between the infestation of ticks on the animals and the age of the animal. Animals with an average body weight below 250kg had 42% (p<0.05) more ticks compared to animals with a body weight above 250kg. Age of the animal and weight were highly correlated (r= 0.70); p<0.001), while the correlation between the number of ticks per cow and the mean weight was negatively correlated (r= -0.37; p<0.001). Skin surface temperature significantly influenced tick infestation on the animals (p<0.001). The degree of infestation increased as body surface temperature exceeded 30º C. Coat score, skin thickness, body condition score and inter calving period did not significantly influence tick infestation on the animals. The infestation of ticks on the animals were significantly influenced by body height (p<0.019) and body length (p<0.001). Animals smaller than a 130cm in height had a significantly (p<0.05) greater tick infestation (36.5±5) compared to animals taller than 130cm (21.2±1.5). This trend was also observed for body length. Animals with a body length shorter than 145cm had a greater (p<0.05) average tick infestation of 41.3±4.5 compared to 23.2±1.3 to animals longer than 145cm, indicating a 44% greater tick infestation in favour of the shorter animals. For increased production and tick resistance animals should have smoother coats and be able to dissipate heat effectively. i ACKNOWLEDGEMENTS The author wishes to express his sincere gratitude and appreciation to the following persons and institutions: My Supervisor, Glen Taylor, for the initial inspiration to undertake this study. Without his continual encouragement, competent guidance and constructive criticism, this study would not have been possible. I would like to extent my word of thanks to my co-supervisor, Prof. E.C. Webb for his contribution and concrete suggestions in making this dissertation presentable. National Research Foundation and Port Elizabeth Technikon, for financial support. Mrs M. van der Rijst for the statistical analysis. My parents and family for their continued support and belief in my abilities. Friends and colleagues for their support. Dr. M. Strydom allowing me to use his Bonsmara herd to collect the data and making the data available for this study. Last but not least, I thank God for his unconditional love and for providing me with the strength and guidance to complete my study. ii DECLARATION OF INDEPENDENT WORK I hereby declare that this thesis submitted for the degree of MAGISTER TECHNOLOGIAE: AGRICULTURE is my original work and has not been submitted by me in respect of a degree to any other institution, and the views expressed are my own. …………............. ………………… T C Botha Date iii PREFACE The purpose of this study was to determine whether physical and production traits (body weights at various points in the production cycle) of beef cattle had an influence on tick burdens, by measuring certain traits such as skin thickness, body condition score (BCS), coat score (CS), body surface temperature, body height and body length and body weight. Various researchers reported that ticks can alter production trends of beef cattle by reducing live weight, when severe infestations occur. It is emphasized by several authors that ticks are becoming increasingly resistant to pesticides (dips), and that the dipping of cattle is expensive and often ineffective. Although it is unlikely that acaricides will not continue to be part of an integrated ectoparasite managing program. The most important methods of reducing tick infestations and the use of pesticides include the use of tick resistant breeds or the identification of production traits in cattle that improve their natural resistance against ticks. The improvement of these production traits and the use of tick resistant animals will have economical advantages to beef cattle producers. The thesis is divided into a general introduction, a literature review on the factors affecting tick burdens on beef cattle followed by the materials and methods used in this study. This is followed by a presentation of the most important results and discusses the relationship between some productive traits and tick burdens. Finally conclusions and implications are drawn from the results and presented in the final chapter. iv ABBREVIATIONS BCS Body condition score BVD Bovine viral diarrhea CS Coat score ICP Inter calving period IPM Integrated pest management v LIST OF FIGURES Figure 1: The influence of age on the tick burdens observed on beef cattle 33 Figure 2: The effect of weight on tick burdens observed on beef cattle 37 Figure 3: The effect of BCS on tick burdens observed