Influence of the lactation length in the subsequent litter size of sows

The aim of this study was to evaluate the in-fluence of lactation length (LL) on the subsequent litter size (LS) in pluriparous and primiparous sows Eighteen commercial hog farms were analyzed over a seven-year period (1996-2003). Feed of the lactating animals was based on commercial ration and water ad libitum, with 79.729 parities grouped into five LL: 8 to 13, 14 to 15, 16 to 17, 18 to 21 and 22 to 25 days. Increased litter size of the subsequent parity (P<0.05) was observed as the lactation period was extended in the pluriparous sows, with 10.70 ± 0.5; 11.16 ± 0.2; 11.15 ± 0.2; 11.34 ± 0.1; 11.87 ± 0.3 for the periods of 8 to 13, 14 to 15, 16 to 17, 18 to 21 and 22 to 25 days, respectively. However, periods of 14 to 15 and 16 to 17 did not show any difference (P>0.05). The primiparous sows produced smaller litter size over the periods of 8 to 13 (10.34 ± 0.9), 14 to 15 (10.41 ± 0.5) and 16 to 17 (10.46 ± 0.6) days, compared to LLs of 18 to 21 (10.68 ± 0.5) and 22 to 25 (11.43 ± 0.8) days. Both the multi-parous and primiparous sows had LL from 22 to 25 days, resulting in higher LS (P<0.05), when compared to other LL. It can be concluded that the lactation pe-riod has an effect on litter size, with the 22 to 25 length providing better results in the litter size of subsequent parity of the female swine.