Estimation of lactation curves of Gyr cattle and some associated production parameters in the Colombian low tropic

Background: The Gyr breed is widely used in Colombian low tropic dairy production systems. During the last 10 years, Asociación Colombiana de Criadores Ganado Cebú† - ASOCEBU, has been leading a milk control program which led to creation of dataset that permits carry out first analysis yield cattle country using records from several herds. Objectives: To study dynamics through estimation lactation curves and four derived parameters: total between 5 305 days (TMY305), peak (PMY), at (DP) persistency (P). Methods: 13,798 daily 1,510 cows performing 103 herds were used; number lactations was 2,480. Four models considered: Wood, Wiltmink, Papajcsik & Bordero, second-degree polynomial. Mean square error, mean absolute error prediction, Akaike Bayesian information criteria select model better describing each majority rule, is, selected by most chosen one. shape fitted curve checked basic results calculus permitted classification estimated into two groups: typical atypical; only functions compute aforementioned parameters. Results: second-order polynomial frequently selected, while Bordero had lowest frequency. Average TMY305, PMY, DP P 3,489.86 kg, 17.28 57.17 days, 0.83, respectively, with coefficients variation: 0.27, 0.21, 0.41, 0.16. Conclusions: This identify individuals outstanding phenotypic performance. best our knowledge, this kind involving thousands regions tropic.