Passafaro Tiago Luciano, Carrera Juan Pablo Botero, dos Santos Livia Loiola, Raidan Fernanda Santos Silva, dos Santos Dalinne Chrystian Carvalho, Cardoso Eduardo Penteado, Leite Romário Cerqueira, Toral Fabio Luiz Buranelo
Universidade Federal de Minas Gerais, Escola de Veterinária, Departamento de Zootecnia, Belo Horizonte, Minas Gerais, ZIP CODE 30.161-970, Brazil.
Fazenda Mundo Novo, Uberaba, Minas Gerais, ZIP CODE 38.040-970, Brazil.
Vet Parasitol. 2015 Jun 15;210(3-4):224-34. doi: 10.1016/j.vetpar.2015.03.017. Epub 2015 Mar 30.
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.
本研究的目的是获得内洛尔牛对蜱、胃肠道线虫（蠕虫）和艾美耳球虫属的抗性遗传参数，分析内洛尔牛育种计划中抗性性状的纳入情况，并评估遗传选择作为寄生虫控制计划中的一种补充工具。对每克粪便中的蜱、胃肠道线虫卵和艾美耳球虫属卵囊进行计数，分别使用了来自1188头、1142头和1142头年龄在146至597天的动物的4270条、3872条和3872条记录。将动物分为对每种寄生虫抗性（计数等于零）或易感（计数高于零）。统计模型包括当代组的系统效应和平均轨迹。随机效应包括加性遗传效应、直接永久环境效应和残差。除艾美耳球虫属抗性的平均轨迹采用三次多项式外，所有性状的平均轨迹和随机效应均用线性勒让德多项式建模。蜱、胃肠道线虫和艾美耳球虫属抗性的遗传力估计值为低到中等水平，分别为0.06至0.30、0.06至0.33和0.04至0.33。不同年龄（205、365、450和550天）同一性状的遗传和环境相关性的后验均值在相邻年龄时有利，在相隔较远年龄时不利。一般来说，抗性性状之间的遗传和环境相关性的后验均值较低，高密度区间较大，且在许多情况下包含零。遗传力估计结果支持在内洛尔牛育种计划中纳入对蜱、胃肠道线虫和艾美耳球虫属的抗性。遗传选择可以提高抗性动物的频率，并可作为寄生虫控制计划中的一种补充工具。
