Date of this Version
The effectiveness of twice daily (2x) versus once daily (1x) boar exposure (BE) and the possible interaction of frequency of BE and type of BE (physical, PBE, versus fence-line, FBE) for stimulating earlier puberty in gilts was evaluated. Gilts (n=120) from the R-LS line of the gene pool herd at the University of Nebraska-Lincoln were, within litter, assigned randomly to two frequencies of BE (1x versus 2x per day) and two types of BE (PBE versus FBE) plus one additional treatment where gilts were maintained in continuous fence-line contact with boars (CFBE). Treatments were initiated when gilts in each replicate reached 160 days of age. Duration of BE for 1x and 2x BE was 10 minutes per exposure. Two sets of three White Line boars (10 months of age at start) were used to stimulate the gilts. Gilts were maintained in groups of eight per pen and were taken to the boar room for stimulation. Physical boar exposure induced a more rapid and more synchronous first estrous response than FBE. The average interval to first estrus after initial BE was shorter (20.2 versus 29.7 days, P<.01) and age at puberty occurred 8.8 days earlier (P<.02) in PBE than FBE gilts. Interval to first estrus tended to be shorter in gilts receiving 2x versus 1x contact with boars (21.5 versus 28.4 days, P<.08). Puberty also tended to occur earlier in gilts receiving 2x versus 1x BE (182.8 versus 191.1 days, P<.06). Interval to estrus and age at puberty in gilts subjected to CFBE did not differ from the other FBE treatments but were increased compared to gilts receiving PBE. Physical BE is required to achieve maximal pubertal response to boar exposure. Added frequency of BE (2x versus 1x per day) tended to decrease pubertal age overall, but it appears the greatest effect of increasing the frequency of boar exposure occurs when gilts are being stimulated with FBE.