The effects of feeding the direct-fed microbial, primalac, on growth parameters and egg production in single comb white leghorn hens.

Two commercial strains of Single Comb White Leghorn hens, HyLine W-36 and DeKalb XL, were reared separately as pullet flocks in an enclosed, environmentally controlled brood-grow house with three banks of quad-deck cages (310 cm2 per bird). There were 1,800 hens of each strain, which were divided into two groups, control feed and a direct-fed microbial (DFM) feed treatment. During the pullet-rearing phase to 18 wk of age, the DeKalb birds had greater parameters of growth and overall feed cost than the HyLine birds. The overall feed cost of the DFM treatment was $0.02 per bird greater than controls. However, the DFM-treated feed improved the livability of the DeKalb birds by 2.68%. At 18 wk of age, 3,528 hens were transferred to an enclosed, mechanically ventilated layer house. The two strains were placed in two differently sized quad-deck layer cages with seven birds per cage; the cage sizes were 35.56 cm x 60.96 cm (2,267.73 cm2 or 310 cm2 per bird) and 14 cm x 32 cm (2,890.32 cm2 or 413 cm2 per bird). There were a total of 144 replications with each strain and DFM treatment combination made up of 36 replications equally divided between the high and low density cages. At 70 wk of age, hens receiving the DFM treatment exhibited greater mean egg weights (61.72 g) and percentages of extra large eggs (XLE, 52.06%) compared to that of controls (61.12 g and 48.98%, respectively). The treatment of 310 cm2/hen DFM produced the least (P < or = 0.05) large eggs; however, this treatment group produced the most (P < or = 0.05) XLE. The use of DFM resulted in a shift from smaller to larger eggs. Regardless of density, the DFM hens had lower (P < or = 0.05) feed cost (FC) compared to FC of the controls (a savings of $0.46/bird between the DFM and control in the 310 cm2 /hen treatment and a $0.83 savings/bird between the DFM and control in the 413 cm2/hen treatment). It was concluded that PrimaLac can improve egg size and lower feed costs, regardless of the bird density used in the present study.