Curva de lactação de vacas primíparas da raça Jersey

Abstract

The study aimed to analyze the format of the lactation curve and the implications on the average production of primiparous Jersey breed cows. Were used 3,531 registers of production from 620 cows, production registrations of cows with calving between 1986 and 2002 and first calving age between 20 and 48 months were used. Production records inferior of 2.0 Kg/day and superior of 38.0 Kg/day were eliminated, the collected production period started on the 3o day after calving and ended on the 305o totalizing 43 weeks of lactation. The parameters of the 15 tested models were estimated throughout non-linear regression (Gauss Newton method). The criteria to elect the best model were: medium square waste (QMR); absolute average deviation (DMA); best adjustment index; visual evaluation comparing the estimated and observed curves and graphs of the distribution of residuals. The model of Wood (1967) has satisfied the most the lactation curve of primiparous Jersey breed cows, presenting a curvilinear behavior with DMA of 0.49 and QMR of 24.93, index of 5.48, lower residual amplitude (between 0.3 and -0.5 Liters) and estimated curve suitable with the observed. Beyond being possible to calculate from its parameters the milk production at the lactation peak, the period of lactation peak and persistence, with 16.6 kg/day, 45 days, 61.11% respectively. The study also allowed the previous detection of errors or vantages on the management, selection or diseases that affects the dairy herd.