Energy Level in the Laying Diet and Its Effects on the Performance of Three Commercial Leghorn Strains

An experiment was designed to investigate the effect of varying the energy level in the diet of three commercial strains of Single Comb White Leghorns. Nine nutritionally adequate base diets were formulated using corn and soybean meal as the only sources of dietary energy. These diets were for hens eating from 77.18 g/hen per day to 113.5 g/hen per day in 4.54-g increments. Each diet supplied .683 g of lysine, .578 g of methionine plus cystine, 3.4 g of calcium, and .315 g of available phosphorus/day. The energy levels resulting from these formulations ranged from 2,710 kcal ME/kg (77.18 g/hen per day) to 2,940 kcal ME/kg (113.5 g/hen per day). These energy values were designated Energy Series 4 (ES 4). Five ES were fed. ES 5 was 100 kcal ME/kg higher in each diet than ES 4; ES 3, ES 2, and ES 1 were 100, 200, and 300 kcal ME/kg, respectively, lower than ES 4. The diets fed were computer formulated with a least-cost model using linear programming. Hens were fed the diet in their ES that most closely matched their dairy feed intake. Hens fed ES 3 and ES 4 had the highest rates of egg production and also the highest egg mass per day. Hens fed ES 3 produced the best economic results. Significant strain differences were present for egg weight; the significance level equaled P<.08 for hen-day production. These findings suggest that three commonly used commercial strains of Leghorns respond similarly to quite drastic changes in dietary energy levels.