The aim of this study was to analyze the milk production and characteristics of the lactation curve of six sheep genetic groups. Were analyzed 863 weekly milk production records of 70 lactations of six genetic groups: East Friesian (EF), Criollo (Cr), EF ½ Cr ½ (EF50Cr50), EF ¾ Cr ¼ (EF75Cr25), Suffolk ½ Cr ½ (Suffolk50Cr50), and Corriedale (C). The function of Wood (WD) was used to estimate the actual total milk yield (PLTobs) and estimated total milk yield at day 180 (PLT180), peak lactation (PL), time at peak lactation (tPL) and persistence (Per). The genetic group influenced significantly (P < 0.05) on PLTobs, PLT180, PL and parameter b of WD model, with highest values of EF50Cr50 sheep. The observed differences in productive performance in relation with the genetic group could be associated with deficiencies in the adaptability of EF sheep to local agro-climatic conditions.Al proyecto PAPIME 204411, Asuntos de Personal Académico General de la UNAM. Al Consejo Nacional de Ciencia y Tecnología (CONACYT) por las becas otorgadas a Diana Arely Solís, Juan Carlos Ángeles y Araceli Guerrero. A Arturo Arellano su apoyo y a la Srta. Liz Hopper, de la Universidad del Norte de Texas por la revisión crítica del presente manuscrito
