The objective was to determine the best nonlinear and linear model to estimate the body weight (BW) of males and females of Holstein (Ho) and Brown Swiss (BS) crossed with Zebu (Z) cattle under two management systems, measuring the thoracic perimeter (TP). 1577 observations of BW and TP measurements from the male and female BS and Ho crossed with Z cattle under two management systems (Estación Experimental La Posta and Matias Romero). Measurements were taken every 28 days from 2006 to 2008 year. An analysis of nonlinear regression of the models, Gamma Function, Brookes and the multiplicative was performed with the software Scientist, which obtained the coefficients a, b, c and the indicators of goodness of fit MSC, R, R², C and multiple linear regression of the body weight (BW) vs thoracic perimeter (PT) in its linear and quadratic form. To the nonlinear model variables a completely randomized experimental design was applied, having the factors: model, gender and management systems. The results showed that there was no statistically significant difference (P≥0.05) among the factors, models and management systems for the analyzed variables, although for the factor gender, male data adjusted better than females data in predicting body weight from thoracic perimeter. TP and TP² were significant (P≤0.05) in the estimation of body weight. The nonlinear model of the gamma function and linear TP-TP² properly estimate the body weight from chest circumference for cattle in the Mexican tropics.