17 Effects of birth traits, physical or fenceline boar exposure and group size on pubertal measures and lifetime fertility of replacement gilts

Abstract

In experiment 1, prepubertal gilts with (n = 264) and without (n = 43) birth records received Fenceline (FBE) or Physical (PBE) Boar Exposure (BE) in a Boar Exposure Area (BEAR). At 185 d of age, gilts (13/pen) received BE for 15 min/d for 3 wk. At the start of Week 3, anestrual gilts received PG600 or no-PG600 (Control). At estrus, females were moved into stalls and inseminated at 2nd heat. Gilts born in larger litters were lighter (r = -0.26) while heavier pigs grew faster to puberty (r = 0.25). PBE increased estrus in Week 1 (38%) over FBE (28%). In Week 3, PBE-PG600 increased estrus (79.9%) compared with PBE- Control (36.2%), while FBE-PG600 and Control did not differ (52.7 vs. 42.5%). By 6 wk, estrus tended to be greater (P < 0.08) for PBE (91.2%) than FBE (83.2%). Reduced fertility associated with: 1) small birth litter; 2) heaviest birthweight; 3) slower growth rate; 4) delayed puberty and age at 1st service; and 5) abnormal estrus interval. Experiment 2 tested the pubertal response to PBE or FBE with 10 or 20 gilts/pen. Gilts (n = 180) at 168 d with 1.8 m2 floor space received BE once/d for 15 min for 1–3 wk. At the start of Week 3, anestrual gilts received PG600. Estrus in Week 1 (7.3%) did not differ, but a BE x Pen effect occurred in Week 2 (estrus range: 15–34%). In Week 3, PG600 increased estrus (P < 0.03) in Pens of 10 (83.7%) compared to Pens of 20 (64.1%). BE method had no effect and Pens of 10 had greater estrus (P = 0.05) than Pens of 20 (88.3 vs 75.8%). These results indicated that use of PBE, a BEAR, smaller group size, and PG600 can be used in combinations to enhance puberty induction. Birth and pubertal measures influenced service and farrowing rate, litter size, and age at removal.

Gilt Management for Fertility and Longevity

“…“White-type” boars most commonly used in commercial production should be a minimum of 10 months of age to ensure that they are secreting adequate levels of the “primer” pheromones and the salivary “froth” that incorporates an essential binding protein for these steroids [69]. Even when using a purpose-designed boar exposure area (BEAR) for stimulating pubertal estrus [75]), direct contact with a boar reduces age at puberty and increases the percentage of gilts cycling, as compared with fence-line contact [69,76]. Furthermore, Patterson et al [77] reported that taking the gilts to the BEAR is more effective in inducing puberty than taking the same boars to group-housed gilts in pens.…”

“…Delaying breeding to second estrus has a positive effect on litter size [69,92,93,94] and is generally accepted as common practice in the industry [5]. The increase in litter size is believed to be a consequence of an improvement in ovulation rate after puberty [76,95,96,97,98] and gilts bred at second estrus produced 1.2 more pigs after four litters as compared with gilts bred at first estrus [92]. No improvement in litter size or farrowing rate resulted from delaying breeding beyond second estrus [92,95].…”