COMPARATIVE STUDY OF CATTLE TICK RESISTANCE USING GENERALIZED LINEAR MIXED MODELS

Amanda Marchi Maiorano,Thiago Santos Mota,Beatriz Pressi Molina Da Silva,Ana Carolina Verdugo,Josineudson Augusto Ii De Vasconcelos Silva,Márcia Cristina De Sena Oliveira,Ricardo Antonio Da Silva Faria,Joslaine Noely Dos Santos Gonçalves Cyrillo

doi:10.28951/rbb.v37i1.341

Abstract

Comparison of tick resistance in Bos taurus indicus (Nelore) and Bos taurus taurus (Simmental and Caracu) subspecies was investigated utilizing generalized linear mixed models (GLMMs) with Poisson and Negative binomial distributions. Nelore animals (NE) are known to present greater resistance than t. taurus. Difference between tick resistance in Simmental (SI) and Caracu (CA) breeds has never been reported previously. Three artificial tick infestations were conducted to evaluate tick resistance in these breeds. The statistic point of the present study was to show alternative models for the evaluation of tick count data, the GLMMs. Analysis for tick resistance by GLMM with Negative binomial distribution has never been assessed previously. The analyses were performed by the use of the PROC GLIMMIX procedure of the SAS program. The results showed that GLMM with Negative binomial distribution is appropriated to evaluate tick count data with excess of zero observations avoiding overdispersion problems. Finally, considering multiple comparisons with the Bonferroni test, different pattern of tick infestation was observed for the studied breeds, suggesting that NE is the most resistant breed followed by CA.

Highlights

The cattle tick, Rhipicephalus microplus, is a blood-sucking parasite originally from Asia, it may be found largely distributed between the parallel 32oN and 32oS (JONSSON et al, 2000), affecting bovine herds from America, Africa, Asia, and Oceania
The objective of this study was to compare tick resistance of Bos taurus indicus (Nelore) and Bos taurus taurus (Simmental and Caracu) subspecies raised in the southeast of Brazil utilizing generalized linear mixed models (GLMMs) with Poisson and negative binomial distributions
For CA breed, high tick resistance was observed for some animals, in addition, the pattern of tick infestation that can be observed for animals of this breed was low, intermediary and high

Summary

Introduction

The cattle tick, Rhipicephalus microplus, is a blood-sucking parasite originally from Asia, it may be found largely distributed between the parallel 32oN and 32oS (JONSSON et al, 2000), affecting bovine herds from America, Africa, Asia, and Oceania. The tick R. microplus can be found across the Brazilian territory (GONZALES, 1993), and it is one of the major causes of detriment for cattle producers (PARIZI et al, 2009). Zebu cattle (Bos taurus indicus) are resistant, while less productive, and have been used as an alternative for Brazilian producers to minimize parasitism problems. Adaptation to tropical environmental conditions and its contact with parasites since early domestication (O’NEILL et al, 2010) may have contributed to development of natural resistance against tick in zebu cattle

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