Effects of reducing dietary nutrient density after the second dose of a gonadotropin-releasing-factor immunization on growth performance and carcass characteristics of intact male pigs and market gilts

Abstract

Objective

The effects of reducing dietary nutrient density after the second dose of gonadotropin-releasing- factor (GnRF) immunization on growth performance and carcass characteristics of intact male pigs and market gilts were investigated.

Materials and Methods

During this 102-d grow- finish study, one dietary program was formulated to meet the recommended ratio of standardized ileal digestible (SID) lysine to NE for nonimmunized physically castrated males and nonimmunized market gilts, and another dietary program was formulated with greater SID lysine for GnRF-immunized pigs than for physically castrated males (15.0% to 20.0% greater SID lysine). During the final 2 dietary phases (final 46 d), additional treatment diets were formulated for diets fed to GnRF-immunized pigs to evaluate nutrient dilution programs (consisting of diluted AA, vitamins, and trace minerals).

Results and Discussion

There were no significant linear effects of diet dilution for G:F or hot carcass weight (HCW) for either male or female GnRF-immunized pigs. For the overall period, G:F was improved and HCW was greater for male GnRF-immunized pigs when compared with nonimmunized pigs. Additionally, G:F tended to be improved, whereas HCW was not different, for female Gn- RF-immunized pigs when compared with nonimmunized pigs.

Implications and Applications

Diluting nutrient density during the post-second-dose period of GnRF im- munization did not affect growth or carcass attributes, and both male and female GnRF-immunized pigs grew faster and were more feed efficient compared with nonim- munized pigs.