AbstractThe preweaning mortality of 382 litters, comprising 3,841 pigs from different purebred and crossbred sows, was studied. The average mortality was 35.7 percent. Around 70 percent of the deaths were attributable to still-born pigs or to weak ones that died within the first week after farrowing. Congenital weakness was outstanding among the causes of death. Some factors influencing preweaning mortality were considered. Summerborn pigs had lower mortality than pigs born in other seasons of the year. Crossbred pigs had lower mortality than purebred. Litters from sows 16 to 23 months old had lower mortality than litters from older sows. Second fitters were similarly more vigorous than succeeding fitters. Farrowing weight was found to exert an important influence on preweaning mortality; fewer of the heavier pigs died. Litters of 12 or more pigs had higher mortality than smaller litters. The interrelationship of age, litter number, farrowing weight, and litter size was studied statistically. Age and litter number influenced preweaning mortality mainly through their effect on the litter size, and the fitter size through its relation to farrowing weight. Farrowing weight exerted relatively the most important direct effect on mortality.
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