Entire males are of increasing interest due to their increased feed efficiency, and the negative public opinion on surgical castration. Entire males have an increased feed efficiency and carcass lean yield compared to barrows, although their growth rate is slightly less.  Entire males are currently not allowed in pork production due to boar taint, but immunocastration by the product Improvest^TM  may allow similar feed efficiency to be achieved. After the second dose of Improvest^TM, fat deposition and feed intake increase, and carcass lean yield is lower than in entire males (but still higher than barrows).  Other methods to control boar taint could be through selection, if the genes responsible for it can be identified. As well, controlling protein and fibre could control the level of androstenone and skatole – which are responsible for boar taint. The use of entire males could provide improved feed efficiency, but changes in pig management and feeding regimes would be required beforehand.