3Classen H L, Riddell, Robinson F E. Effect of increasing photoperiod length on performance and health of broiler chick- ens [J ]. British Poultry Science, 1991,32( 1 ) : 21-29.
4Appleby M C,Mench J A, Hughes B O. Poultry behavior and welfare [ M ]. London, UK : CABI Publishing, 2004.
5Bessei W. Welfare of broilers:a review[J]. World's Poultry Science Journal, 2006,62 : 455-466.
6Lesson S,Summers J D. Response of growing Leghorn pullets to. long or increasing photoperiods[J]. Poultry Science, 1985,64 (9) : 1617-1622.
7Renden J A,Bilgili S F,Kincaid S A. Researchnote:Compar- ison of restricted and increasing light programs for male broiler performance and carcass yield[J]. Poultry Science, 1993,72(2): 378-382.
8Brown A J,Webster A B, Fairchild B D,et al. Photoperiod effects on broiler behavior[J]. Poultry Science Association Meet- ing Abstract,2008,87(1 ) : 191.
