Uso de polinômios segmentados para o estudo da curva de lactação de búfalos da raça Murrah e seus mestiços em sistema de criação semi-intensivo, no estado de São Paulo

Abstract

Considering the need to better understand the curve of lactation and the little information of this nature with buffalo, the purpose of this study was to evaluate the use of Polynomials Segments, data from models Quadratic-Quadratic (QQ) and three segments squared (QQQ), the adjustment of lactation curve average of the animals and their crossbred Murrah in a system of farm semi-intensive. For these systems, which are carried twice millings day, records were used to produce three herds, totaling 3.267 lactations for a total of 27.600 test day. The test-day was done at intervals of 30 days, from 1990 to 2001. The lactations used contained at least four and no more than nine controls. For the QQ model, the average curve reached a node in the second month of lactation, as the QQQ model for the node have been estimated for the second and fourth month of lactation. The parameters and each function were estimated by iterative process, using the procedure PROC REG of SAS statistical package. The criteria used for evaluating the quality of adjustment for each function were: Coefficient of Determination Adjusted (R2A), Test Lack of Fit (LOF) and graphics distribution residues. In this production system the QQ and QQQ models, accompanied the changes in yield production during the lactation, with no significant tests LOF and the R2A estimated for both function was over 99%. The QQQ models, estimated minors residues and presented a R 2A=99.98%.