These heavier birds have more muscle. They grow fast and can quic- kly reach a high slaughter weight. This requires plenty of high quality feed. It requires special skills to keep this in good supply and balance. Hybrids or cross-breeds result from combining special lines or strains of chickens developed for this purpose with . a local breed. The hybrids are more productive. In countries in the South, cross-breeding between pure breeds is also common, . White Leghorn crossed with Rhode Island Red. Nowadays hybrid breeds have become very com- mon. .
