The material consisted of the data concerning reproductive performance traits of the Polish Large White sows, which was used in the breeding value estimation using the BLUP method in second half of May 2008. The analysis covered sows, which gave from one to eight litters. The following two indexes were computed: WI – total number of days from sow birth date to last litter delivery day over the sum of piglets born, and WII – total number of days from sow birth date to last litter delivery day over the sum of piglets in day 21 of live. The values of both indexes decreased with successive litters. Regression coefficients were estimated on the basis of correlation between individual reproduction traits and indexes. The impact of individual traits upon the indexes changed in successive litters during the period of the use of a sow. The impact of total number of piglets in a litter decreased, and the impact of the period between first farrowing and last litter delivery increased. Considering this,longevity of sows may affect pork production profitability.
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