title: Genetic analysis of resistance to ticks, gastrointestinal nematodes and Eimeria spp. in Nellore cattle.
abstract: The aim of the present study was to obtain genetic parameters for resistance to ticks, gastrointestinal nematodes (worms) and Eimeria spp. in Nellore cattle, analyze the inclusion of resistance traits in Nellore breeding programs and evaluate genetic selection as a complementary tool in parasite control programs. Counting of ticks, gastrointestinal nematode eggs and Eimeria spp. oocysts per gram of feces totaling 4270; 3872 and 3872 records from 1188; 1142 and 1142 animals, respectively, aged 146 to 597 days were used. The animals were classified as resistant (counts equal to zero) or susceptible (counts above zero) to each parasite. The statistical models included systematics effects of contemporary groups and the mean trajectory. The random effects included additive genetic effects, direct permanent environmental effects and residual. The mean trajectory and random effects were modeled with linear Legendre polynomials for all traits except for the mean trajectory of resistance to Eimeria spp., which employed the cubic polynomial. Heritability estimates were of low to moderate magnitude and ranged from 0.06 to 0.30, 0.06 to 0.33 and 0.04 to 0.33 for resistance to ticks, gastrointestinal nematodes and Eimeria spp., respectively. The posterior mean of genetic and environmental correlations for the same trait at different ages (205, 365, 450 and 550 days) were favorable at adjacent ages and unfavorable at distant ages. In general, the posterior mean of the genetic and environmental correlations between traits of resistance were low and high-density intervals were large and included zero in many cases. The heritability estimates support the inclusion of resistance to ticks, gastrointestinal nematodes and Eimeria spp. in Nellore breeding programs. Genetic selection can increase the frequency of resistant animals and be used as a complementary tool in parasite control programs.
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: tpassafaro@hotmail.com.
authors.forename: Tiago Luciano
authors.initials: TL
authors.lastname: Passafaro
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: juanbotero67@hotmail.com.
authors.forename: Juan Pablo Botero
authors.initials: JP
authors.lastname: Carrera
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: livialoiola@gmail.com.
authors.forename: Livia Loiola
authors.initials: LL
authors.lastname: dos Santos
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: fernandaraidan@gmail.com.
authors.forename: Fernanda Santos Silva
authors.initials: FS
authors.lastname: Raidan
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: dalinne_chrystian@hotmail.com.
authors.forename: Dalinne Chrystian Carvalho
authors.initials: DC
authors.lastname: dos Santos
authors.affiliation: Fazenda Mundo Novo, Uberaba, Minas Gerais, ZIP CODE 38.040-970, Brazil. Electronic address: epcardoso@fazendamundonovo.com.
authors.forename: Eduardo Penteado
authors.initials: EP
authors.lastname: Cardoso
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Medicina Veterinária Preventiva, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: rcleite@vet.ufmg.br.
authors.forename: Romário Cerqueira
authors.initials: RC
authors.lastname: Leite
authors.affiliation: Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil. Electronic address: flbtoral@ufmg.br.
authors.forename: Fabio Luiz Buranelo
authors.initials: FL
authors.lastname: Toral
mesh_terms: D000818:Animals; D001947:Breeding; D002417:Cattle / Q000235:genetics*; D003048:Coccidiosis / Q000662:veterinary*; D060467:Disease Resistance / Q000235:genetics*; D004539:Eimeria / Q000235:genetics / Q000502:physiology*; D005243:Feces / Q000469:parasitology; D005260:Female; D008297:Male; D015233:Models, Statistical; D009348:Nematoda / Q000502:physiology*; D009349:Nematode Infections / Q000662:veterinary*; D010641:Phenotype; D013984:Tick Infestations / Q000662:veterinary*; D013987:Ticks / Q000502:physiology*
keywords: Bayesian inference; Beef cattle; Genetic parameter; Selection