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This study was a 3 x 8 factorial arrangement of 3 nutrient densities (low, medium, and high) and 8 commercial Leghorn strains. The objective of this experiment was to determine the effect of increasing both dietary energy and other nutrients (amino acids, Ca, and available P) on performance, egg composition, egg solids, egg quality, and profits in 8 commercial Leghorn strains during phase 1 (from 21 to 36 wk of age). This experiment lasted 16 wk. Eight strains of hens (n = 270 of each strain) at 21 wk of age were randomly divided into 24 treatments (6 replicates of 15 birds/treatment). There were no interactions between strain and diet except for BW. Strain had a significant effect on all measured parameters except mortality, whole egg solids, and yolk color. As nutrient density increased, hens linearly adjusted feed intake to achieve similar energy intakes so that the similar quantities of dietary energy (5.8 to 5.9 kcal) were used to produce 1 g of egg. As nutrient density increased, egg mass linearly increased, and feed conversion linearly improved. Egg-specific gravity and Haugh unit linearly decreased with increasing nutrient density. There was a quadratic response of the percentage of albumen solids to the increased nutrient density. Increasing both dietary energy and other nutrient (amino acids, Ca, and available P) contents significantly increased yolk and albumen weight at the same time, resulting in a significant increase of egg weight during early egg production. Egg weight may be maximized to genetic potential by increasing both dietary energy and other nutrient (amino acids, Ca, and available P) contents during early egg production. Because egg prices and ingredient prices often change, there can be no fixed optimal nutrient density for optimal profits.

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Primary Audience: Egg Producers, Nutritionists, Farm Managers SUMMARY A 4 × 2 × 2 factorial experiment with 4 dietary energy levels (2,776, 2,820, 2,864, and 2,908 kcal/kg) and 2 strains (Bovans White and Dekalb White) with and without Tylosin was conducted to determine the influence of dietary energy and antibiotic on performance, egg solids, and egg quality. The experiment lasted 10 wk. Bovans White hens (n = 768) and Dekalb White hens (n = 768) at 55 wk of age were randomly divided into 16 treatments (8 replicates of 12 birds per treatment). Bovans hens had significantly greater egg production and significantly lower egg weight, egg-specific gravity, and shell weight than Dekalb hens. Increasing dietary energy by the addition of poultry oil had no significant effect on performance, egg solids, or eggshell quality. An ideal dietary energy level for optimal performance could not be determined. There can be no fixed ideal dietary energy level for optimal profits, due to varying feed ingredient and egg price. Although Tylosin supplementation had no effect on performance or egg solids, Tylosin significantly reduced dirty eggs, resulting in a positive effect on egg quality.Key words: strain, dietary energy, Tylosin, egg composition, feed intake DESCRIPTION OF PROBLEMDietary energy, an important nutrient in layer diets, is typically supplied by cereal and protein sources and supplemental fat. Dietary energy level can significantly affect the cost of production, because increasing energy levels by the addition of fat can significantly decrease feed intake, increase egg weight, and improve feed conversion [1][2][3][4][5][6][7]. Protein (amino acid) intake significantly decreases with increasing dietary energy [3]. Because decreasing protein (amino acid) intake can adversely affect hens [8][9][10], there might be an ideal energy:protein ratio for optimal performance [3]. As hens age, protein requirements decrease so that more corn and less soy are included in corn-soy diets, resulting in greater dietary energy levels. Increasing dietary energy by the addition of fat to lowprotein diets may not significantly improve performance, because low-protein diets may have sufficient dietary energy contributed from corn and soy. It is important to have a better understanding concerning the effect of dietary energy on performance.Increasing dietary energy by the addition of poultry oil has been shown to significantly affect percentage of egg components [3]. The

A .ῌ-factorial experiment with four added dietary energy (fat) levels (* (*.*), ,. (*./), .2 (+.*), and 1, (+./) kcal ME/kg (ῌfat)) and three protein levels (+..3, +/./, and +0.+ῌ) was conducted to determine the influence of dietary energy on performance, egg composition, egg solids, egg quality, and profits of Hy-line W--0 hens at di#erent protein levels. The basal diets of the +0.+, +/./, and +..3ῌ protein contained ,,12., ,,2**, and ,,2+/ kcal ME/kg, respectively. This experiment lasted +, weeks. Hy-line W--0 hens (n῍+..*) in phase -(// weeks of age) were randomly divided into +, treatments (2 replicates of +/ birds per treatment). There was no interaction on performance, egg components, egg solids, and egg quality between protein and dietary energy. As protein level increased from +..3 to +0.+ῌ, percent yolk and yolk/albumen ratio linearly decreased and percent albumen linearly increased. Yolk color linearly increased as protein level decreased. Increasing dietary energy by the addition of poultry oil had no significant e#ect on performance, egg composition, egg solids, and egg quality. An ideal dietary energy level for optimal performance could not be determined for Hy-line W--0 hens during phase -. Because feed ingredient prices and egg price vary, there can be no fixed ideal dietary energy level for optimal profits during phase -.

Two experiments of 4 x 2 x 2 factorial arrangements of 4 dietary energy levels, 2 molting methods (feed withdrawal and no salt diet), and 2 strains (Bovans White and Dekalb White) were conducted to determine the effect of dietary energy and molting method on long-term postmolt performance of 2 strains of commercial Leghorns. In experiments 1 and 2, Bovans White hens (n = 576) and Dekalb White hens (n = 576) were randomly divided into 16 treatments (6 replicates of 12 birds per treatment). Experiment 1 lasted from 86 to 96 wk of age, and experiment 2 lasted from 100 to 110 wk of age. Bovans White hens had significantly higher egg production than Dekalb White hens, whereas Bovans White hens had significantly lower egg weight, percentage of eggshell, and egg specific gravity than Dekalb White hens. Based on improved feed conversion, dietary energy of 2,846 kcal of ME/kg appeared to be enough for optimal performance during second cycle phase 2. Based on BW of hens, dietary energy level for optimal performance should be less than 2,936 kcal of ME/kg during second cycle phase 3. There can be no fixed ideal dietary energy level for optimal profits for postmolt egg production. Molting method had no effect on egg production and egg mass during the early and middle stages of the postmolt production period. However, hens molted by feed withdrawal had significantly higher egg production and egg mass during the later stage of the postmolt production period compared with hens molted by a no salt diet. There was no significant difference in egg specific gravity due to molting method. Feeding a no salt diet resulted in reasonable long-term postmolt performance and eggshell quality, rather than optimal performance and eggshell quality.

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