Differences in production values between high- and low-productivity swine breeding herds

Data were collected from 80 North American users of a computerized health and management software program for the period August 1985 through July 1986. Fifty-four herds were selected for analysis based on selection criteria of 1) stable herd inventory, 2) complete recorded data, 3) weaning-to-first service interval greater than 3 d and less than 20 d, and 4) culling rate greater than 10%. These herds had an average of 18.2 pigs weaned/(female.year) (PWFY), 2.1 litters/(female.year) (LFY), 81% farrowing rate, 10.2 pigs born live/litter and 14.5% preweaning mortality. Compared with the 14 herds with the lowest values for pigs weaned/(female.year), high-productivity herds (i.e., the 14 herds with the highest values for PWFY) had higher LFY, farrowing rate, total and live pigs born/litter and sow-gilt ratio; they also had lower nonproductive female days (NPFD), lower preweaning mortality and fewer gilts as a proportion of female inventory. Herd size and PWFY were not correlated. A negative correlation between herd size and pigs born live remained after controlling for average lactation length (r = -.30). Nonproductive female days was highly correlated with LFY (r = -.87). Increasing herd age, measured by the sow-gilt ratio, was associated mainly with a reduction in NPFD, although there was a slight positive association with pigs born alive (r = .29).