79 Determination of Optimal Timing of Marketing for Carcass Quality Measurements in Gilts Administered Improves

Abstract

Abstract Gilts immunized against gonadotropin-releasing factor (GnRF) have reported improvements in carcass characteristics including increased belly weights and thickness, and increased loin intramuscular fat (IMF) compared with controls. The objective was to determine the optimal market timing post second dose (PSD) for anti-GNRF-treated gilts for carcass characteristics. Treatments were arranged as a 2×4 factorial: control vs anti-GnRF (d7 and 77; d0 = 8 wk of age) and marketing time PSD anti-GnRF: (first cut: 10 heaviest gilts; last cut: remaining gilts): d18 and 39 PSD; d25 and 46 PSD; d32 and 53 PSD; and d39 and 60 PSD. Pen (n=120) was the experimental unit (12-18 pens per treatment; 21 gilts per pen). Carcass data were determined from 107-188 gilts per treatment per day PSD with primal data collected from 39-54 carcasses per treatment per day PSD. At 25 wks of age, 52.5±0.05% of control gilts vs. 0.92±0.01% of anti-GnRF gilts were cycling based on ovarian structures. Regardless of cut, anti-GnRF increased (P ≤0.05) HCW, backfat, and belly depth. Loin depth and belly weights were greater (P ≤0.05) in second cut anti-GnRF gilts compared with control. Calculated percent lean was decreased in both marketing events in anti-GnRF gilts compared with control. While belly yield was similar, iodine value was decreased in anti-GnRF gilts compared with control, regardless of marketing event. Trimmed loins were lighter (P = 0.02) in second cut anti-GnRF gilts, but had greater (( P < 0.01) IMF compared with control gilts. Shear force was similar between treatments. Use of anti-GnRF in gilts results in heavier carcasses and several primal weights. The time PSD to market anti-GnRF-treated gilts does not appear to impact carcass quality indicating that it is best to focus on optimal timing based on performance traits.