When piglets are born it is recommended that they be castrated in their first 2-14 days. Pigs that are not castrated have better growth performance and more lean meat, but they are also more more aggressive which increases the chances of fighting with pen mates, causing carcass damage, and they are more susceptible to having boar taint in the meat which reduces its quality. This project looks at immunization against gonadotropin-releasing (GnRF) factor as an alternative to castration. The objective is to determine the impact immunization against GnRF, using Pfizer’s boar taint vaccine on the dynamics and control of whole body protein deposition,  dynamics of plasma levels of androgens, estrogens and growth regulating hormones, mean body lipid and body protein deposition, and carcass and meat quality. Thirty six pigs were used on four different trials: conventional castration, no castration, no castration with immunization ( at 30 and 70 kgs body weight), and late castration at 25-40kgs body weight. The study noted that there was a dramatic change in feed intake and nutrient metabolism after the pigs became immunized, after immunization pigs were able to attain the same levels as castrated pigs. The study also showed the close relationship between changes in nutrient metabolism and hormones that are involved in regulating growth and nutrient metabolism in growing pigs. It was confirmed that immunization of male pigs against GnRF is effective at controlling boar taint from male pigs at high slaughter weights. These finding allow producers to avoid castration and raise “entire” male pigs with improved meat quality and consistency.