A meta-analysis of dry matter intake in Nellore and Zebu-crosses cattle

José Augusto Gomes Azevêdo,Sebastião De Campos Valadares Filho,Rilene Ferreira Diniz Valadares,Douglas Dos Santos Pina,Mario Luiz Chizzotti

doi:10.1590/s1516-35982010000800024

José Augusto Gomes Azevêdo, Sebastião De Campos Valadares Filho + Show 3 more

Open Access

https://doi.org/10.1590/s1516-35982010000800024

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Abstract

The study was carried out to develop and to evaluate new equations to predict dry matter intake (DMI) of Nellore and Zebu-crosses cattle using meta-analysis procedure. The data used to estimate the parameters were collected from independent performance experiments using growing and fattening Nellore and Zebu-crosses cattle, and they were compiled from 561 experimental units. Before proposing an equation to predict DMI, it was observed that the genetic group was a source of statisticaly significant variation. Therefore, equations to predict dry matter intake in the Zebu-Crosses and Nellore cattle were independently developed. The regression equations for Zebu-crosses cattle were: DMI = -2.6098 + 0.08844BW0.75 + 4.4672ADG - 1.3579ADG2 and DMI = -1.0094 + 0.01608BW + 4.4363ADG -1.2548ADG2. The regression equations for Nellore cattle were: DMI = -2.7878 + 0.08789BW0.75 + 5.0487ADG - 1.6835ADG2 and DMI = -1.3559 + 0.0159BW + 5.6397ADG - 1.8494ADG2. In order to evaluate fitted equations, it was utilized data from independent experiments published from 2005 to 2008 in the Revista Brasileira de Zootecnia. The equations (DMI) for Nellore overpredicted dry matter intake for estimates lower than 7 and higher than 10 kg·d-1. For Zebu-crosses cattle, dispersions of 3 kg d-1 were observed when extreme intakes were evaluated, however, when the equation included BW 0.75, the intercept did not differ from zero and the slope did not differ from 1. It is not possible to fit only one equation for preditcting DMI for beef cattle in tropical conditions, because there are differences between Zebu and Zebu-crosses. Fitted equations that include ADG and BW 0.75 should be used as an alternative method to predict dry matter intake of Zebu-crosses and Nellore beef cattle in tropical conditions.

Highlights

Numerous quantitative intake prediction models have been developed, none has achieved widespread acceptance and none uses a universally applicable and robust prediction model (Pittroff & Kothmann, 2001)
The regression equations for Nellore cattle were: dry matter intake (DMI) = -2.7878 + 0.08789BW0.75 + 5.0487ADG – 1.6835ADG2 and DMI = -1.3559 + 0.0159BW + 5.6397ADG – 1.8494ADG2
Fitted equations that include average daily gain (ADG) and body weight (BW) 0.75 should be used as an alternative method to predict dry matter intake of Zebu-crosses and Nellore beef cattle in tropical conditions

Summary

Introduction

Numerous quantitative intake prediction models have been developed, none has achieved widespread acceptance and none uses a universally applicable and robust prediction model (Pittroff & Kothmann, 2001). The National Research Council guidelines for beef cattle production (NRC, 2000) have been used in Brazil to formulate diets and evaluate feeding programs. These equations were developed mostly with Bos taurus cattle, with a size scaling procedure that is used to adjust differences in mature animal size. A meta-analysis, which incorporates the Study effect and its interaction as random components of a mixed model, must be used This should result in better prediction equations of biological systems and a more accurate description of their prediction errors (St-Pierre, 2001). This study was carried out to develop and evaluate new equations for dry matter intake prediction in Nellore cattle and Zebu-crosses using a meta-analysis procedure

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