Influence of a gonadotropin-releasing hormone vaccine and dietary standardized ileal digestible lysine level on growth performance and carcass quality of grower-finisher pigs.

The aim of this study was to assess the effect of standardized ileal digestible (SID) Lys levels of the diet on the growth performance, carcass characteristics, and meat quality of entire males (EM), surgical castrates (SC), and males vaccinated with a gonadotropin-releasing hormone (GnRH) vaccine (GV). In total, 252 crossbred pigs were fed 6 different experimental diets consisting of 3 sexes (EM, SC, and GV pigs) and 2 dietary SID Lys levels (2008 CVB standard SID Lys recommendation [Std] or 15% extra SID Lys [+15]) according to a 3-phase feeding scheme (d 0 to 35, 35 to 70, and 70 to 105 of experiment) with 6 pens per treatment and 6 pigs per pen. To determine if dietary SID Lys could be reduced for GV males after the second vaccination, an additional dietary treatment was included (GV+15-Std). The GV males on the GV+15-Std were fed the diet with 15% extra SID Lys in the starter and grower phases and the standard SID Lys level in the finisher phase. First vaccination was administered to pigs at the start of the experiment (23.4 kg BW and 63.6 d of age), and the second vaccination occurred 6 wk before slaughter (77.2 kg BW and 126.6 d of age). Until the second vaccination, GV pigs showed a lower (P ≤ 0.05) ADFI than SC but similar to EM. After the second vaccination, GV pigs had an intermediate (P ≤ 0.05) G:F between EM and SC. The GV+15 pigs showed a better G:F (P ≤ 0.05) than GV pigs fed the GV+15-Std diet in the finisher phase. No differences in the growth rate of the pigs were observed. The SC had a greater (P ≤ 0.05) carcass weight and dressing percentage than EM and GV pigs. The GV-Std pigs had a lower (P ≤ 0.05) meat percentage and greater (P ≤ 0.05) backfat thickness than the GV+15 pigs. The GV pigs and SC fed the standard SID Lys diet had a greater (P ≤ 0.05) percentage of SFA in the subcutaneous fat than EM+15 pigs. On the other hand, SC showed the greatest (P ≤ 0.05) concentration of MUFA compared to EM and GV pigs. The SC and GV pigs had a lower (P ≤ 0.05) PUFA percentage in the subcutaneous fat than EM fed the standard SID Lys diet.