The aim of this study was to determine the productive and metabolic response in Chilota lambs grazing Calafatal or naturalized pasture. The experiment was conducted at the Experimental Station Butalcura (INIA, Chilo,) during October, November, and December 2011. Eight Chilota and six Suffolk Down 2-month-old lambs, uncastrated males, no twin, were located to graze a typical secondary succession of the Chilo, Archipelago, as a Calafatal (a secondary succession which derivates from human intervention on native forest in Chilo, Archipelago). Simultaneously, eight male 2-month-old Chilota lambs were located to graze a naturalized pasture, another secondary succession derived from human intervention on native forest in Chilo, Archipelago. Animals had free access to water sources. Measurements were performed one time a month, for three consecutive months for productive indicators: live weight, average daily gain and body condition score, and blood indicators of protein and energetic metabolism. Productive and metabolic response was similar between both types of pastures (P > 0.05). However, Chilota and Suffolk Down lambs grazing Calafatal showed higher plasma concentrations of beta OH-butyrate, but lower non-esterified fatty acids (NEFA) than Chilota lambs grazing naturalized pasture (P < 0.05). Chilota lambs grazing naturalized pasture showed the highest plasma concentrations of NEFA and urea (P < 0.05). It was concluded that, under the conditions of the study, Chilota lambs grazing naturalized pasture, which had higher contents of crude protein and metabolizable energy, showed better metabolic balance, but not performance, than Chilota and Suffolk Down lambs grazing Calafatal.