In the present work we intend to evaluate the diet used in the fattening of 27 lambs of the dorper race and also measure the daily weight gains and by means of the comparison with different authors to make the decision to return or not to use said diet. The work done in order to evaluate the weight gain of 27 lambs of the Dorper breed in fattening fed with a diet based on hay of oats, alfalfa hay, ground corn, ground sorghum and chicken manure in which were found gains of 333 grams per day, thus having a final market weight of 48 kg on average, this in a period of 3 months of fattening after an early weaning of 2 months. Therefore, the decision was made that this diet based on oats, alfalfa, corn, sorghum and chicken manure generates adequate profits and therefore will be used by the producer in future fattening. The variations of the CA over time were estimated by means of a quadratic equation in the group of sheep.