Tick Resistance in Indigenous Nigerian Cattle Breeds: Genetic Architecture, Immunological Mechanisms, and Breeding Programme Implications

This dissertation provides an original genetic and immunological characterisation of tick resistance in indigenous Nigerian cattle breeds, identifying the genetic architecture and immunological mechanisms underlying natural tick resistance and their implications for marker-assisted selection in tick management breeding programmes. Ticks and tick-borne diseases are the most economically important livestock health constraints in Nigeria, and tick-resistant breed selection offers a sustainable alternative to acaricide-dependent control, yet the genetic and immunological basis of tick resistance in Nigerian indigenous breeds is uncharacterised. The dissertation employs a multi-phase experimental design involving 600 indigenous cattle (White Fulani, Muturu, and Ndama breeds) and 200 exotic crossbreds selected from the North West, South East, and South South geopolitical zones. Tick challenge experiments using standardised Rhipicephalus microplus larval infestations are performed under controlled conditions. Resistance phenotypes are assessed by tick attachment rates, engorgement rates, and reproductive indexes. Whole genome SNP genotyping using the BovineHD BeadChip is performed on all animals. Genome-wide association studies (GWAS) identify QTLs significantly associated with tick resistance phenotypes. Transcriptomic analysis of skin from resistant and susceptible animals identifies differentially expressed immune pathway genes. The dissertation proposes the Tick Resistance Genomic Index (TRGI) as an original selection tool. Primary findings indicate that Ndama and Muturu breeds show significantly superior tick resistance mediated by enhanced basophil degranulation, complement activation, and IL-6 skin immunity responses. Keywords: tick resistance, indigenous cattle, genomics, GWAS, Nigeria.