INFLUENCE OF THE SIRE ON LITTER SIZE IN SWINE

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Abstract
The direct effect of the sire on the total number of pigs born (including stillborn, excluding necrotic), the number born alive, and the number weaned was studied in 277 Yorkshire and 356 Lacombe litters sired by 131 Yorkshire and 163 Lacombe boars. At mating, the average age of the males was 250 ± 18 days and of the females 248 ± 18 days. The Yorkshire and Lacombe sires produced an average of 2.11 and 2.18 litters, respectively. For the Yorkshire litters the total number of pigs born, number born alive, and number weaned were 9.43, 9.07, and 8.15, respectively. Corresponding averages for the Lacombes were 9.09, 8.38, and 6.97. In both the Yorkshire and Lacombe populations there was a significant sire effect on the total number of pigs born, the number born alive, and the number weaned. Intra-sire correlations (repeatability) for total number born, number born alive, and number weaned were 0.174 ± 0.082 (P < 0.05), 0.163 ± 0.081 (P < 0.05), 0.194 ± 0.081 (P < 0.01) in Yorkshires and 0.242 ± 0.070 (P < 0.01), 0.208 ± 0.071 (P < 0.01), and 0.167 ± 0.072 (P < 0.05) in Lacombes. Linear regression coefficients of litter size (number born, number born alive, number weaned) on number of females settled by the sire are presented.