Growth, food conversion and carcass characteristics in castrated and entire male pigs fed three different dietary protein levels

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Abstract
A total of 72 pigs comprising 36 boars and 36 castrates of 22 kg live weight were allocated to one of three protein levels in the diet. The crude protein concentrations were 16·0, 18·0 and 20·0%. The diets were fed to appetite for three half-hour periods per day from 22 to 90 kg live weight.Up to 55 kg live weight both boars and castrates showed an initial positive response to the increased protein concentration. This was followed by a negative response during the 55–90 kg period for both food conversion and daily live-weight gain. For the overall period the differences in performance were not significant. From 22 to 55 kg, and from 55 to 90 kg the average daily feed intake of boars was significantly less than that of the castrates.Boars had a significantly better overall food conversion, larger eye muscle area and decreased back fat.This experiment indicated that there was no advantage in feeding boars a protein concentration higher than that generally used for gilts or castrates while on a semiad libitum feeding system.