Abstract
ABSTRACT: This research identified the animal model that best describes the genetic and residual variations for tick counts in yearlings from a crossbred Angus-Nellore population of 6,951 animals that are progenies of 382 bulls and 6,198 cows. Genetic values were predicted by the Bayesian inference methodology. The models tested were: Traditional Animal, and Crossbred Animal with and without segregation, considering residual homoscedastic and heteroscedastic variances. The criteria of choice were the number of parameters, deviance information, and predictive order, which indicated the best fitfor the Traditional Animal model and Crossbred Animal model (with segregation), both with residual heteroscedastic Gaussian variance. The mean values of fixed genetic effects were positive and similar in the both models, indicating that animals with higher proportion of the Angus breed had greater infestation, and the Nellore breed was an important addition for resistance to ticks. The estimated genetic variation by the heteroscedastic Gaussian Animal model for the Nellore breed was 4.54-fold higher than that estimated for the Angus breed. The estimates of heritability of the different genetic groups ranged from 0.12 to 0.15 and from 0.01 to 0.35, respectively, for the Traditional Animal model and for the heteroscedastic Gaussian crossbred model. The Spearman’s rank-order correlation for the predicted genetic values was 0.94, considering all sires. However, when considering the top 10%, 20%, and 30% sires, differences in ranking were more evident (0.28 to 0.67). The Crossbred Animal model with segregation and heterogeneous residual variances was the most appropriate for genetic evaluation of tick counts on animals from Angus-Nellore crossings.
Highlights
IntroductionV.51, n.10, The economic losses to the Brazilian livestock caused by ticks in bovine animals reach U$ 968 million (GRISI et al, 2014)
Rhipicephalus (Boophilus) microplus is an ectoparasite that attacks bovine animals, hinders significantly their performance by causing stress, interferes on weight gain, favors the occurrence of myiasis, depreciates the skin quality, and transmits protozoans that cause diseases such as anaplasmosis and babesiosis.Approved 01.05.21 Returned CR-2020-0500.R2 by the authorRural, v.51, n.10, The economic losses to the Brazilian livestock caused by ticks in bovine animals reach U$ 968 million (GRISI et al, 2014)
The objective of this research was to identify the animal model that better describes genetic and residual variations, to evaluate the genetic variability, and rank the best sires according to the genetic evaluation for tick counts in yearlings from a crossbred Angus-Nellore population
Summary
V.51, n.10, The economic losses to the Brazilian livestock caused by ticks in bovine animals reach U$ 968 million (GRISI et al, 2014). The consumer market demands bovine meat free from chemical residues, which can have negative impacts on the environment and human health (MOTA et al, 2016). The use of acaricides to control tick infestations is the most common management adopted by producers. This is seldom done strategically and with a technical follow up, generating consequences by incorrect use that increase the parasite resistance to commercial molecules. The incorrect disposal of bottles, and residues of antibiotics in meat products are undesirable
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
