Effect of rearing cross-fostered piglets in litters of either uniform or mixed birth weights on pre-weaning growth and mortality

Cross-fostering is a practice commonly used in the swine industry to equalize litter sizes, however, there is limited understanding of the optimum cross-fostering methods that will maximize piglet preweaning growth and survival. This study evaluated the effects of within-litter variation in birth weight after cross-fostering on piglet preweaning mortality (PWM) and weaning weight (WW) using litters of 15 piglets. A hierarchical incomplete block design was used (blocking factors: day of farrowing and sow parity, body condition score, and number of functional teats) with a 3 × 2 factorial arrangement of treatments: 1) Birth Weight Category (BWC): Light ( 0.05) PWM and WW in UNIFORM and MIXED litters. The results of this study, which involved large litter sizes typical of current commercial production, suggested that for piglet survival to weaning, using cross-fostering to form litters of piglets of similar birth weight was beneficial for light piglets, detrimental for heavy piglets, and neutral for medium piglets.