Logistic regression was used to develop models predicting preweaning survival in 334 neonatal swine. Measured risk factors included birth weight, litter size (live born), dam parity, serum IgG concentration, serum ELISA titers recognizing common gram-negative core antigens, and serum concentrations of the third component of complement. Larger birth weights were associated with increased probability of preweaning survival. The highest mortality was observed in litters with more than 12 pigs. Pigs with serum concentration of the third component of complement (C3) in the lowest stratum, < 20% adult pooled C3 standard (APC3), had reduced mortality, compared with high (> 38% APC3) and middle (20 to 38% APC3) groups. Associations between all other variables, including total serum IgG concentration and preweaning survival were not significant. Few pigs had hypogammaglobulinemia, < 3% of the study population had serum IgG concentrations < 1 g/dl. Of all measured variables, only birth weight and dam parity were significant predictors of preweaning gain. Larger pigs and pigs born to third or greater parity dams had more preweaning gain than other pigs.

In the conditions of the swine breeding complex in the Republic of Belarus where had been applied the three-way crossing and self-replacement of swine herd there was studied the productivity of swine depending on duration of their embryonic development. There was developed new method of selection replacement gilts which made it possible to select a breeding swine flock with high adaptation abilities to the industrial housing conditions. Research results showed that the duration of pregnancy in the conditions of three-way rotational crossbreeding and self-replacement of swine herd was 114,5 +/- 0,03 days with variance between 103 and 121 days. In the majority of breeding sows (93%) the duration of pregnancy period was within the limits from 112 up to 117 days. Season of a year rendered influence on the duration of sow pregnancy: the longest one was in winter and spring, the shortest – in summer and autumn. With advancing age there was stated the increased duration of pregnancy period. Difference in duration for first-pregnant sows and sows with 8 farrows was 0,51 days. With increase of pregnancy duration there was noted the lowering of multiple fetation, but there was the increasing of live weight of piglets at birth, their growth energy and viability