Effect of Pre-Breeding Boar Exposure on Gilt Estrus

Abstract Text: Current research suggests that boar habituation reduces the frequency and length of estrus in sows. Similar studies utilizing gilts have had inconsistent results. A trial was proposed to evaluate the effect of boar habituation on breeding gilts. A total of 22 gilts (Yorkshire; Yorkshire x Landrace) were blocked by age, breeding, and litter. Gilts were allotted to one of two treatments resulting in three replicates. Eleven gilts were divided into three pens (3-4 gilts each) and housed adjacent to a boar (contact group). The remaining 11 gilts were divided into three pens (3-4 gilts each) and housed in a room isolated from the boars (isolation group). Gilts were heat checked for 23 consecutive days in their pens using a teaser boar. All gilts in both treatments were moved to a breeding pen when estrus was detected and again exposed to a teaser boar for artificial insemination. At the time of insemination (day 1) all gilts were scored (1 = excellent, 2 = moderate, and 3 = poor) based on; initial standing reflex, maintaining standing reflex, and semen acceptance. All gilts were then re-bred approximately 24 hours later (day 2). Estrus expression was more prevalent in the isolation group (91% vs. 64%, P > 0.13). Initial reflex had a tendency to be stronger (1.42 vs. 2.17, P = 0.09) in gilts housed in isolation on day 1. Day 1 maintenance of reflex was unaffected by treatment but semen acceptance had a tendency to be stronger in the contact group (1.17 vs. 1.97, P = 0.07). The isolation group had a higher rate of gilts that would not produce a standing reflex on the second day, 27% versus 9% in the contact group. Both the initial reflex (2.33 vs. 1.00, P = 0.013) and maintenance of reflex (2.00 vs. 1.00, P = 0.045) were stronger in the isolation group. Day 2 semen acceptance was unaffected by treatment (P = 0.59). Breeding scores were not different between age groups (P > 0.15) nor was there an interaction between treatment and age (P > 0.46). The isolation group only achieved a 70% conception rate versus an 83% conception rate for the contact group (P = 0.55). These results show that boar habituation does have the potential to negatively affect some aspects of estrus expression in gilts.

Keywords: estrus, gilts, habituation