GROWTH AND FAT DEPOSITION CURVES IN SWINE

Within-pig regressions of probed backfat thickness (BF) on liveweight (WT) and log 10 of age (AGE) on log 10 liveweight (LWT) were analyzed to: (1) assess the effects of farrowing season (spring, late summer-early fall), breed (Lacombe and Yorkshire), and sex (boar and gilt); and (2) if warranted, derive, test, and comment on alternative adjustment factors to the ROP adjustment factors currently in use. Results indicated that the interactions involving farrowing season, breed, and sex were significant for the regression parameters (slope, x− and y− intercept). Evaluation of adjustment factors led to the following observations: (1) a regression approach was more appropriate for adjusting age to a specific weight and for adjusting backfat probes at weights below the specific weight and (2) the ROP adjustment was more effective in adjusting backfat probes from weights above the specific weight. It was concluded that research on adjustment factors was required with season of the year, breed, and sex being considered. Any new adjustment factors should be flexible in order to accomodate shifts in the liveweight being adjusted to. Key words: Pigs, backfat, growth, breed, sex