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Effects of dietary metabolizable energy and standardized ileal digestible lysine content of the diet on performance and egg quality of brown-egg laying hens from 18 to 41 weeks of age

Scappaticcio, R., H. Herrera, G. Fondevila, A. de Juan, L. Cámara and G. Mateos

The influence of energy (AMEn, kcal/kg) and standardized ileal digestible lysine (SIDLys) content of the diet on egg production and egg quality traits was studied in brown-egg laying hens from 18 to 41 wk of age. The experimental design was completely randomized with 10 treatments organized as a 2 x 5 factorial with two energy concentrations (2,750 and 2,700 kcal/kg) and five AMEn to SIDLys ratios (3.48, 3.62, 3.77, 3.93, and 4.10). Each treatment was replicated 10 times and the experimental unit was the cage with 10 hens for all measurements. To ensure that the SIDLys content of the diet was limiting hen production in all cases, all diets were formulated to exceed by at least 2 percent units the desired ratio between key indispensable AA and SIDLys content. Birds had free access to feed and water throughout the trial. Production data (egg rate, feed intake, egg weight, egg mass, FCR, BW gain, and mortality) were collected and analyzed by period (6 periods of 4 wk each) and cumulatively (18 to 41 wk of age). Egg quality traits (egg weight, Haugh units, and shell resistance to breakage) were measured in 8 eggs randomly selected from each replicate in the last 2 days of each of the 6 experimental periods. Data were analyzed as a completely randomized design using the MIXED procedure of SAS, with energy concentration, AMEn to SIDLys ratio, and the interaction as main effects. In addition, the effects of the level of SIDLys on the variables studied were partitioned into its lineal (L) and quadratic (Q) components. All differences were considered significant at P < 0.05. No interactions between AMEn and SIDLys level of the diet were found for any of the variables studied and therefore, only main effects are presented. An increase in the AMEn content of the diet from 2,700 to 2,750 kcal/kg increased egg weight (P < 0.05) but did not affect the number of eggs produced or feed conversion ratio. A decrease in the AMEn to SIDLys ratio, increased linearly egg weight (P < 0.05) and egg mass production (P < 0.05) and tended to improve feed conversion ratio (P = 0.100). Feed intake and BW gain, however, were not affected. Neither energy nor AMEn to SIDLys ratio affected any of the egg quality traits studied. However, shell resistance to breakage increased linearly (P < 0.05) as the AMEn to SIDLys ratio of the diet decreased. In conclusion, an increase in the energy content of the diet from 2,700 to 2,750 kcal AMEn/kg did not affect egg production but increased egg weight and egg mass production.

The data indicate that brown laying hens require no more than 769 mg SIDLys/d to optimize egg production. However, when the objective is to maximize egg weight, at least 806 mg SIDLys/d are needed.