Mixed nonlinear models in ruminal in situ degradability trials

Authors

  • Simone Daniela Sartorio de Medeiros Universidade Federal de São Carlos - UFSCar, Centro de Ciências Agrárias, Departamento de Tecnologia Agroindustrial e Socioeconomia Rural, Caixa Postal 153, CEP: 13604-900, Araras, São Paulo. https://orcid.org/0000-0001-6455-8319
  • Cesar Gonçalves de Lima Universidade de São Paulo - USP, Faculdade de Zootecnia e Engenharia de Alimentos - FZEA, Departamento de Ciências Básicas, Caixa Postal 23, CEP: 13635-900, Pirassununga, São Paulo. https://orcid.org/0000-0002-7244-4845
  • Taciana Vilella Savian Universidade de São Paulo - USP, Escola Superior de Agricultura Luiz de Queiroz - ESALQ, Departamento de Ciências Exatas, Caixa Postal 9, CEP: 13418-900, Piracicaba, São Paulo. https://orcid.org/0000-0002-3309-6075
  • Euclides Braga Malheiros Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências Agrárias e Veterinárias, Departamento de Ciências Exatas, Caixa Postal ???, CEP: 14884-900, Jaboticabal, São Paulo. https://orcid.org/0000-0003-4179-0064
  • Simone Silmara Werner Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina - EPAGRI, Estação Experimental de Lages - EEL, Caixa Postal 181, CEP: 88502-970, Lages, Santa Catarina. https://orcid.org/0000-0002-3973-4605

Abstract

Classical methods of analysis of nonlinear models are widely used in studies of ruminal degradation kinetics. As this type of study involves repeated measurements in the same experimental unit, the use of mixed nonlinear models (MNLM) is proposed, in order to solve problems of heterogeneity of variances of the responses, correlation among repeated measurements and consequent lack of sphericity in the covariance matrix. The aims of this work are to present an evaluation of the applicability of MNLM in the estimation of parameters to describe the in situ ruminal degradation kinetics of the dry matter of Tifton 85 hay and to compare the results with those obtained from the usual analysis in two-phases. The steers used in the trial were fed diets composed of three different combinations of roughage and concentrate and two hays with different nutritional qualities. The proposed approach was proven as effective as the traditional one for estimating model parameters. However, it adequately models the correlation among the longitudinal data, which can affect the estimates obtained, the standard error associated with them and potentially change the results of the inferences. It is quite attractive when the research seeks to understand the behavior of the process of food degradation throughout the incubation times.
Keywords: Ruminal degradation kinetics; Longitudinal data; Covariance matrix; Random effects; Dry matter.

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Published

2020-06-16

How to Cite

MEDEIROS, S. D. S. de; LIMA, C. G. de; SAVIAN, T. V.; MALHEIROS, E. B.; WERNER, S. S. Mixed nonlinear models in ruminal in situ degradability trials. Brazilian Animal Science/ Ciência Animal Brasileira, Goiânia, v. 21, 2020. Disponível em: https://revistas.ufg.br/vet/article/view/57596. Acesso em: 16 aug. 2024.

Issue

Vol. 21 (2020): Continuous publication

Section

ZOOTECNIA

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