The objective of the computer simulation was to assess the influence of herd structure on piglet production and some other production traits in a pig nucleus herd. As stated, the culling rate changes the herd structure and the length of staying in a herd. With increasing culling rate the average age of sows decreases, the number of weaned piglets per sow drops, total production of piglets is lower while the cost per piglet until 20 kg of live weight rises. The total profit in a herd per sow per year decreases, the total costs and returns also decrease. The trend of increasing the number of barren days of sows with increasing culling rate is confirmed. With increasing culling rate, sows of low parities become dominant in the herd and a higher percentageof sows is removed before their production peak. The comparison of various culling rates help to define the most suitable herd structure in terms of breeding plans.