The objective of the present study was to determine the effect of Sarcocystis lamacanis experimental infection in young alpacas on body weight gain, hematocrit, and fibre yield. The study was carried out with 63 alpacas, five months old, distributed in three treated and two control groups. The treated groups were formed by 13, 12, and 13 animals, orally infected with 1,000, 2,500, and 5,000 Sarcocystis sp. esporocysts respectively. One control group of 12 animals, under traditional rearing without restriction to the access of dogs, shared the grazing area with the treated groups; whereas the other control group of 13 animals was placed in a separate grazing area with fences that impede dog access to pastures. The inoculum was obtained from dogs that were infected through alpaca heart meat containing Sarcocystis lamacanis microcysts. Body weight was recorded and blood samples were monthly collected. The fleece weight was recorded at shearing time. Body weight gain and hematocrit levels decreased after sporocysts administration, especially in the group infected with 5,000 sporocysts. Furthermore, this group had 92.3% mortality in the first three months post infection.