Investigational research is required to support the development of a new technology called immunological castration, which addresses the issue of boar taint in male pigs and allows for increasing growth efficiency. There is a knowledge gap in the understanding of the nutritional requirements for immunological castrates (IC). Therefore, the objective of this thesis was to extend the current knowledge of immunological castration in the pig as it relates to growth performance, nitrogen and phosphorus retention, and pork quality. Forty six pigs were used in the first experiment, 11 each of IC and physical castrates (PC) and 12 each of gilts (G) and entire males (EM). Entire males and IC had overall superior ADG compared to PC and G, PC and IC consumed the most feed, and EM were the most feed efficient. Fourteen days after the second injection, nitrogen retention in IC was intermediate between EM and PC and phosphorus retention for IC was similar to EM. Quality characteristics were similar from pork produced by all 3 pig sexes except for marbling. Pork from IC and PC provided similar sensory characteristics. Three hundred pigs were used in the second experiment, 150 each of IC and PC, and each sex was fed 5 diets with differing standardized ileal digestible (SID) lysine amounts for 3 growth phases. The experimental SID lysine levels were determined from the nitrogen retention results from the first experiment. For each growth phase, IC had a greater SID lysine requirement, including after the second injection, compared to PC. In order for feeding programs to be developed for IC, nutritionists need to understand the nitrogen, phosphorus, and SID lysine requirements in order to optimize the use of the technology.