Reproductive performance records for number of pigs born alive (NBA) or stillborn (NSB), litter weight at birth (WT) and litter weight at 21 day (WT21) on 13, 923 litters of 2, 367 sows (238 Landrace (L); 178 Large White (W); 1, 418 LW; 533 WL) raised in 35 farms from 1987 to 1991, were used to analyze the effects of parity and breeds. Analysis of variance included the effects of parity and breeds of sows, regions of farms, partial regressions of year-season effects of farrowings.
The parity and breed effects were significant in all traits, and the interaction effects between parity and breed were significant in NSB and WT21.
The least squares means for NBA showed the largest value at the fifth parity of L and WL litters, and at the fourth parity of W and LW litters. And also the means for NSB showed the lowest values at the second parity in all four breeds litters. Also for WT, the means showed the largest values at the fouth parity except WL litter. The largest means for WT21 were at the second or third parity except L litter.
The least squares means for NBA obtained only from the first to fourth parity were values of 10.59, 10.09, 11.27, 11.21 for L, W, LW, WL litters, respectively, and the performance ranking of sow breed was LW=WL>L>W. The means values of NSB were also 0.91, 0.80, 0.61, 0.71 for L, W, LW, WL litters, and the ranking was L>W>WL>LW. The means values of WT (kg) were also 16.63, 15.12, 16.71, 16.83 for L, W, LW, WL litters, and the ranking was L=LW=WL>W. The means values of WT21 (kg) were also 65.69, 62.42, 62.50, 63.78 for L, W, LW, WL litters, and the ranking was L>WL=LW=W.
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