The objective of this study was to examine the influence of generation, parity number and year on sow prolificacy in the nucleus herd of the closed population of old genotype Lithuanian White pigs. Data on farrowing and litter size (total born, born alive, including sex of piglets, stillborn) were available per parities for individual sows from 2000 to 2011. The piglets originated from 395 litters (104 dams and 28 sires) of five generations. The generation showed effects on the number of total born piglets, piglets born alive, including males (p<0.01) per litters and did not appear to affect the number of stillborn piglets. The parity showed overall effects on the numbers of total born and stillborn piglets (p<0.01). Least square means for these traits increased with increasing parity number and reached significant (p<0.05) increase in parity 5. The year of farrowing showed the overall effect on the numbers of total born (p<0.01), born alive (p<0.001), including their sex and stillborn piglets (p<0.05). The decline in the numbers of piglets born alive was observed from 2008. This study showed that breeding of old genotype Lithuanian White pigs in a small closed population over the first four generations had no clear negative influence on sow prolificacy.
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