Low retention rate of female pigs associated with gilt development, lifetime performance and culling pattern in commercial swine herds

The objectives of this study were to characterize swine herds that had a low retention rate by parity 3 (LRR herds) in terms of gilt development and lifetime reproductive performance and to examine management factors associated with low retention of females. The retention rate by parity 3 was defined as the number of females first-mated and successfully reaching the third parity. Questionnaires were sent to 115 herds that use the same recording system requesting information about gilt development and herd management procedures in 2008 : (1) whether or not there was restricted feeding for prepubertal gilts ; (2) type of gilt development diet ; and (3) percentage of home-grown gilts in the herd. Data of 81 completed questionnaires (70.4%) and herd productivity measurements were coordinated with the performance data of 15,678 gilts that entered into those herds in 2008. Herds were categorized into LRR herds and ordinary herds on the basis of the lower 25th percentile of retention rate by parity 3 (71.6 %). Herd level analysis showed that the LRR herds had 3.4% lower farrowing rates and 7.7% higher culling rates than ordinary herds (P<0.05). In addition, more LRR herds used restricted feeding and a gestation diet than ordinary herds (P<0.05). Furthermore, LRR herds had 29.2% higher percentage of home-grown gilts in their herds than ordinary herds (P<0.05). Individual female level analysis showed that first-mated females in LRR herds had 6.2-11.2% higher culling risk by parity 1-3 for reproductive failure than those in ordinary herds (P<0.05). However, no difference was found between the herd groups for lifetime average pigs weaned (P=0.79). In a multilevel proportional hazard model, the hazard of culling for a female was associated with the restricted feeding and higher percentage of home-grown gilts in their herds (P<0.05), but not with the types of gilt development diet (P=0.21). The survival probabilities at 60 weeks from first-mating were 80.1 and 84.1% for females that had restricted and unrestricted feeding as pre-pubertal gilts, respectively. In conclusion, too much restricted feeding during pre-pubertal periods is not recommended to improve female longevity. Additionally, strict selection procedures for reproductive soundness are recommended for home-grown gilts on entry to their herds.