Sheep raising is usually done under traditional systems in the Northeast of Brazil and particulary in the State of Piauí. The weight gains and the reproductive efficiency of these systems are low, and the lamb mortality high. In the sheep industry, it is essential to have a good reproductive efficiency and an offspring high surviving rate to be well succeed economically. The objective of this work was to study the mortality rate of Santa Inês lambs, from birth to weaning at 120 days. The herd was raised in rangeland, with feed suppiementation in the critical season, under two reproductive management systems: one parturition per year and three parturitions in two years. The lamb mortality rate was evaluated considering parturition type, reproduction management system, year and the birth season The mortality rate was 15.18% for the simple births, increasing to 24.74% for the twin births (P<0.01).The reproduction management system influenced the twin lamb mortality rate (P<0.05), with a higher rate (29.74%) in the lambs from the three parturition system in two years. Birth season influenced (P<0.01) the lamb mortality rate, with higher rate when the births occurred in the dry season.
sheep; mortality; lambs; sheep management systems
