ABSTRACT
The influence of long-bright and increasing-dim photoperiods on live and processing performance was investigated in 2 broiler strains. Fifty males of moderate (M) and high (H) yield strains were placed by strain in 2 pens in each of 12 rooms. Six rooms were provided a long-bright photoperiod (LB treatment) of 23L:1D with 2 footcandles of intensity. The other 6 rooms were provided an increasing-dim photoperiod (ID treatment) of 20L:4D from 1 to 10 d, 12L:12D from 10 to 21 d, 15L:9D from 21 to 28 d, 18L:6D from 28 to 35 d, and 20L:4D from 35 to 54 d, with 0.1 foot-candle throughout. Relative to LB, the ID treatment had lower BW from 7 to 28 d, feed consumption from 7 to 35 d, and feed conversion from 7 to 42 d; however, these variables did not differ between treatments at 54 d. The M strain had consistently greater BW and feed consumption than the H strain. However, M strain feed conversion was only greater from 7 to 35 d. Mortality was unaffected by treatment or strain. Total breast weights and yields were 42 g or 5.1% greater, respectively, in the LB than the ID treatment. Fillet weights and yields, and tender yields, were greater in the LB than ID treatment. Leg weights and yields, and wing yields, were greater in the ID than LB treatment. Total breast weights of M and H strains were similar; however, yield was 3.3% greater in the H than M strain. Fillet yields were greater in the H than M strain. Wing and leg weights and yields were greater in the M than H strain. There was an interaction effect on fat pad weights and yields, which were greater in H strain subjected to ID treatment than other strain and treatment combinations. These results indicate that increasing photoperiods and dim intensities, which often improve broiler live performance, may have a greater negative effect on breast meat production than differences in strains.
