Males have different nutritional requirements than female breeders. As they do not produce eggs, their requirement for both calcium and protein is lower than the requirements of females.
When we give male and females the same feed, males actually get more protein and calcium than they need. Not only is the extra calcium and protein a cost factor that is wasted on these birds, but the oversupply actually puts pressure on them, as they have to get rid of it.
With sex-separate feeding, we can feed males a special diet, more suited for their needs. An adequate diet for adult males has a protein level of approximately 13%, and a calcium level of 1-1.5%. Some research has shown that with these feeds, mortality of males can actually be reduced and performance increased.
Although in theory this beneficial effect can be expected, in the field we seldom see this. When male feeds are used, normally we do not see beneficial effects on mortality or fertility. Sometimes less dense diets are used (energy and protein), which can help to control bodyweight of males better, as they can be fed in higher quantities with a better feed distribution. This effect can have a positive influence on male performance.
The cost of the feed can be another reason for separate male feed. In theory, feeds with lower calcium and protein are cheaper, but this effect can dissolve when the feeds have to be made in small quantities and stored separately. In large integrations, a special male feed can be cost effective. Another practical solution for the small quantities needed can be to use grower feed (rearing) with a double amount of premix as male feed.