22 Poor management of breeding herd replacements is a key factor in poor sow lifetime productivity: Gilty as charged

Abstract

Abstract Recently published research on gilt development using contemporary commercial dam-lines has confirmed: 1) That the growth performance of gilts is rarely below the lifetime growth rate of 0.55 kg.d that would limit the onset of sexual maturity; 2) The majority of gilts provided direct daily contact with mature boars from 160 days of age reach puberty by 200 days of age and represent a normal distribution of “early responders”; 3) Gilts that respond later to boar stimulation have poorer lifetime fertility and tend to be over weight at breeding; 4) Pubertal responses to direct boar contact are significantly higher than responses to fenceline contact with boars; 5) Even if pubertal responses to direct boar contact are delayed in particular cohorts of gilts, good pubertal responses to exogenous, low-dose eCG/hCG treatments (PG600) allow efficient replacement gilt flows to be maintained in most commercial situations; 6) Delaying breeding until second observed estrus, and providing at least 10 days of acclimation to individual stall accommodation, maximizes first litter performance. When gilts were managed in purpose designed facilities that allowed daily records of vulval and behavioral responses to effective boar stimuli to be recorded, the lifetime reproductive performance of know pubertal gilts entering the breeding herd exceeded industry benchmarks. Of 2,374 naturally cyclic and 741 PG600-induced gilts delivered to the breeding herd, 97.6 and 95.7%, respectively, were bred, 94.7 and 92.0%, respectively, farrowed a first litter and 70.6 and 65.3%, respectively, farrowed a fourth litter. In terms of key factors other than reproductive performance that affect retention rate, another recent large-scale study of commercial replacement gilts derived from multiplication sows with a known litter birth weight phenotype confirmed data based on individual gilt birth weight, in that high growth rates linked to heavy weights at breeding were a major risk factor for early removal from the breeding herd. Therefore, poor gilt management must still be viewed as a major factor limiting breeding herd performance.