2008 Volume 12 Issue 1 Pages 36-42
The objectives in this study were to compare salivary progesterone (PRG) concentrations between sows weaned one litter and sows used for nursing piglets after weaning their own piglets (nurse sows), and to investigate the associations between PRG concentrations, backfat thickness (BF), and reproductive performance. A farm with approximately 300 female pigs (females) was visited 13 times from 2005 to 2006 to collect saliva samples at weaning from 138 sows weaned one litter and 42 nurse sows. Reference samples were also collected from 15 gestating females. The reproductive performance was recorded for each sow. The weaned sows were categorized into two groups on the basis of the upper 25 percentile of PRG concentrations : >3.1 (HIGH) and<3.0ng/ml (OTHER). Statistical mixed-effects models were used and statistical power was calculated. Sows weaned one litter and nurse sows had lower PRG concentrations than gestating females (2.1 and 3.0 vs. 4.1ng/ml ; P<0.01). No differences were found in any reproductive performance between sows weaned one litter and nurse sows. HIGH group had 0.7 fewer pigs born alive at subsequent farrowing than OTHER group (P<0.05). Sows with increased BF during lactation tended to have 17.1% higher in the percentages of sows having high PRG concentrations (P=0.068 ; Power=0.373) and 0.8 days longer weaning-to-first-mating interval than those with decreased BF (P<0.05). High PRG concentrations at weaning were associated with few pigs born alive at subsequent farrowing. This association may be partially related to increased BF during lactation.
