Nutrient Retention in Entire Male Pigs Immunized Against Gonadotropin-Releasing Hormone

Immunization against gonadotropin-releasing hormone (GnRH) reduces boar taint occurrence in male pigs and likely alters the rate and composition of body weight gain. Serial slaughter and nitrogen-balance studies were conducted to evaluate dynamics and hormonal control of body protein deposition (PD) and body lipid deposition (LD) in entire male pigs (EM), entire male pigs immunized against GnRH with IMPROVEST (IM), conventional, early castrates (EC), and male pigs surgically castrated between 25 and 40 kg body weight (late castrates; LC). Growth performance and physiology were similar in EC and LC. The PD was highest and LD was lowest in EM, while LD was highest in IM. Following immunization, PD in IM gradually changed from that in EM to that in EC and LC. Changes in PD and LD were consistent with changes in the animal’s physiology. Dynamics of PD and LD should be considered when optimizing feeding programs for IM.