Reproduction Indicators Related to Litter Size and Reproduction Cycle Length Among Sows of Breeds Considered Maternal and Paternal Components Kept on Medium-Size Farms.

The present research aimed to study twelve reproductive indicators related to litter size and the farrowing interval for three maternal (Polish Large White, Polish Landrace, and Yorkshire) and three paternal (Duroc, Berkshire, Hampshire) breeds, raised on two farms in Poland and a farm in the United States. The study included 196 sows (45 Polish Large White, 37 Polish Landrace, 26 Berkshire, 33 Duroc, 40 Yorkshire, and 15 Hampshire), which altogether gave birth to 736 litters. The Kruskal-Wallis test was used to verify the influence of the breed on the reproductive traits, with a post-hoc procedure for pairwise comparisons implemented in the pgirmes of R. The adegenet, ade4, and factoextra packages of R were used to conduct multivariate analysis of the traits by means of principal component analysis. The breed significantly (p ≤ 0.05) influenced the following traits related to litter size: the total number of piglets born per litter, the number and percentage of piglets born alive per litter, the percentage of stillborn piglets per litter, the number and percentage of weaned piglets per litter; and those related to the farrowing interval: the lengths of gestation, lactation, the farrowing-to-conception interval, and the farrowing interval. The breed did not statistically significantly influence the number of stillborn piglets per litter and the length of the weaning-to-conception interval. Polish Landrace and Polish Large White sows had the highest numbers of born (for both, the mean of 14.0), born alive (12.9 and 12.7), and weaned piglets (11.5 and 10.5), which statistically significantly differed from these parameters in the other breeds. Polish Landrace sows significantly differed from all the other breeds in terms of the percentage of weaned piglets (84.1%), while Berkshire sows in terms of gestation length (118.4 days).