| Autor: |
Mapholi NO; Department of Life and Consumer Sciences, University of South Africa, Private Bag X6, Florida, 1710, South Africa. maphon@unisa.ac.za., Maiwashe A; Agricultural Research Council, Private Bag X2, Irene, 0062, South Africa.; Department of Animal Sciences, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa., Matika O; The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK., Riggio V; The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK., Banga C; Agricultural Research Council, Private Bag X2, Irene, 0062, South Africa., MacNeil MD; Agricultural Research Council, Private Bag X2, Irene, 0062, South Africa.; Department of Animal Sciences, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa.; Delta G, 145 Ice Cave Road, Miles City, MT, 59301, USA., Muchenje V; University of Fort Hare, Private Bag X 1314, Alice, South Africa., Nephawe K; Department of Animal Sciences, Faculty of Science, Tshwane University of Technology (TUT), P/Bag X680, Pretoria, 0001, South Africa., Dzama K; Department of Animal Science, University of Stellenbosch, P Bag X1, Matieland, 7602, South Africa. |
| Abstrakt: |
The objective of the study was to characterise genetic parameters across months for different tick species and anatomical locations in South African Nguni cattle. Tick counts were conducted monthly, over a 2-year period, on 586 Nguni cattle under natural infestation, from four herds located in different provinces of South Africa. The counts were recorded for six species of ticks (Amblyomma hebraeum, Rhipicephalus evertsi evertsi, Rhipicephalus decoleratus and microplus (Boofilids), Rhipicephalus appendiculatus, Rhipicephalus simus and Hyalomma marginatum) attached on eight anatomical locations on the animals and were summed by species and anatomical location. Heritability estimates, phenotypic and genetic correlations were estimated on a monthly basis using mixed linear models, fitting univariate and bivariate sire models. Fixed effects considered were location, sex, year and age as a covariate. Tick counts were higher in the hot months, and A. hebraeum was the most dominant tick species. Heritability estimates for tick count varied by month and trait and ranged from 0 to 0.89. Genetic correlations were mostly positive, and low to high, with some negative correlations with high standard error. Phenotypic correlations were low to moderate. In general, high genetic correlations were observed between whole body count and the anatomical location counts, suggesting that it may not be necessary to conduct whole body counts. Counts from the belly and perineum appeared to be the most suitable surrogate traits for whole body count. These findings provide useful information for developing strategies for the practical implementation of genetic selection, as a supplement to the traditional tick control measures. |
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