State University of Southwestern Bahia, Itapetinga, BA, 45.000-700, Brazil.
Department of Biological Sciences, State University of Southwestern Bahia, Jequié, BA, Brazil.
Trop Anim Health Prod. 2023 Oct 19;55(6):362. doi: 10.1007/s11250-023-03782-2.
The use of mixed nonlinear models reduces the residual variance by including random effects, thereby improving the estimates in growth curves. Therefore, we tested distinct mixed nonlinear models (Richards, Brody, Gompertz, Logistic, and Von Bertalanffy) to model the growth curves of Zebu cattle herds raised on pasture in Brazil. In addition, we evaluated the diversity among breeds using hierarchical cluster multivariate analysis (full linkage) based on asymptotic weight (A), maturity rate (K), absolute growth rate (AGR), and absolute maturity rate (AMR) adjusted to 205, 365, 550, and 730 days of age. Body weight data from 311,834 males and females of Guzerat, Nellore, Tabapuã, and Polled Nellore breeds provided by the Brazilian Association of Zebu Breeders were used. The Brody model considering breed-sex fixed and animal random effects was the most suitable to describe the growth in the four breeds. The Guzerat and Tabapuã males showed increased precocity (higher K values) when compared to polled Nellore and Nellore males, which were characterized by higher A and AMR values. Females were more precocious than males (high K and low A values), particularly within Tabapuã and Guzerat breeds, respectively. Regardless of sex, the highest AGR values were observed from weaning up to 2 years of age in Tabapuã and Guzerat breeds. The cluster analyses revealed two groups: (1) Polled Nellore and Nellore males with high A, AGR_205, AGR_365, AGR_550, and AGR_730 values, represented by large adult animals, and (2) males and females of Guzerat and Tabapuã, characterized as animals of increased precocity. A subgroup encompassing males of Guzerat and Tabapuã was also observed, with intermediate values for all parameters. This information is useful to help breeders and producers in strategies for feeding management and defining the most precocious beef cattle breed to increase the economic gains in pasture-based raising systems.
使用混合非线性模型通过包含随机效应来减少残差方差，从而改善生长曲线的估计值。因此，我们测试了不同的混合非线性模型（Richards、Brody、Gompertz、Logistic 和 Von Bertalanffy）来模拟在巴西牧场上饲养的瘤牛群的生长曲线。此外，我们还使用基于渐近体重（A）、成熟率（K）、绝对生长率（AGR）和调整至 205、365、550 和 730 天的绝对成熟率（AMR）的全链接层次聚类多元分析（hierarchical cluster multivariate analysis）评估了品种间的多样性。巴西瘤牛饲养者协会提供的 311,834 头古扎拉特、内罗尔、塔帕乌阿和无角内罗尔公母牛的数据用于体重。考虑品种性别固定和动物随机效应的 Brody 模型最适合描述四个品种的生长。与无角内罗尔和内罗尔公牛相比，古扎拉特和塔帕乌阿公牛表现出早熟（较高的 K 值），而无角内罗尔和内罗尔公牛的 A 和 AMR 值较高。与公畜相比，母畜更为早熟（高 K 和低 A 值），特别是在塔帕乌阿和古扎拉特品种中。无论性别如何，Tabapuã 和 Guzerat 品种在断奶至 2 岁期间的 AGR 值最高。聚类分析显示了两个群体：（1）无角内罗尔和内罗尔公畜具有高 A、AGR_205、AGR_365、AGR_550 和 AGR_730 值，代表大型成年动物；（2）古扎拉特和塔帕乌阿的公母畜具有早熟特征。还观察到一个包含古扎拉特和塔帕乌阿公畜的亚组，所有参数的中间值。这些信息有助于饲养者和生产者在饲料管理策略中，以及在确定最早熟的肉牛品种以增加基于牧场的饲养系统的经济收益方面提供参考。
