A 4 x 2 factorial experiment with 4 dietary energy levels (2,719, 2,798, 2,877, and 2,959 kcal of ME/ kg) and 2 strains (Bovans White and Dekalb White) was conducted to determine the effect of dietary energy on reproductive performance, egg composition, and profits of 2 strains of commercial Leghorns. This experiment lasted 16 wk. Bovans White hens (n = 768) and Dekalb White hens (n = 768) in phase I (21 wk of age) were randomly assigned into 8 treatments (16 replicates of 12 birds/treatment). Bovans White had significantly higher feed intake, egg production, egg mass, body weight, percentage egg yolk, and yolk/albumen ratio than Dekalb White. Bovans White had significantly lower feed conversion, egg weight, egg specific gravity, percentage of albumen weight, percentage of shell weight, and Haugh unit than Dekalb White. When dietary energy increased from 2,719 to 2,956 kcal of ME/kg, hens adjusted feed intake from 107.6 to 101.1 g/hen per day to achieve a constant energy intake so that the same amount of dietary energy (5.8 kcal) was used to produce 1 g of egg. Increasing dietary energy by the addition of poultry oil increased early egg weight, which was mostly due to increased yolk weight. Increasing dietary energy by addition of poultry oil significantly decreased feed conversion and egg specific gravity but had no effect on egg production, egg mass, body weight, or mortality. Increasing dietary energy by addition of poultry oil to a ratio of 282 kcal of ME/g lysine maximized egg weight during phase I. The energy per lysine ratio required for optimal profits varied with egg price and feed ingredient prices, which were variable.

beta-Mannanase (Hemicell) is a unique enzyme-based feed ingredient that can hydrolyze beta-mannan, an antinutritional fiber in feed. Because soybean meal contains beta-mannan and its derivatives, addition of beta-mannanase may improve soybean-meal utilization. The purpose of this study was to evaluate the effect of beta-mannanase on performance of commercial Leghorns fed corn-soybean meal based diets. In this experiment, 3 diets were formulated. The metabolizable energy content for diet 1 (high-energy diet) was 2,951 kcal/kg, which was 120 kcal/kg higher than diet 2 (low-energy diet supplemented with beta-mannanase) and diet 3 (low-energy diet without beta-mannanase). Hy-Line W-36 hens (n = 720, 98 wk old) were randomly divided into 3 dietary treatments (16 replicates of 15 hens per treatment). The trial lasted for 12 wk. Overall average feed conversion of hens fed the low-energy diet supplemented with beta-mannanase was similar to that of hens fed the high-energy diet, and both were significantly lower than that of hens fed the low-energy diet without beta-mannanase. There were no significant differences in overall average egg production and egg mass among 3 dietary treatments for the 12-wk period. However, the addition of beta-mannanase significantly increased average egg production and egg mass of hens fed the low-energy diet from wk 5 to 8. There were no significant differences in feed intake, egg specific gravity, egg weight, mortality, body weight, and body weight variability among the 3 dietary treatments. beta-Mannanase supplementation improved energy utilization of corn-soybean layer diets and has potential to reduce the cost of practical laying hen diets containing beta-mannan.

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.

The objective of this experiment was to compare the effects of 2 sources of phytase on performance of commercial Leghorns fed corn-soy diets. Seven diets were fed to Hy-line W-36 hens (n = 840; 8 replicates of 15 hens per treatment) from 21 to 33 wk of age. The treatments consisted of a control diet containing 0.38% nonphytate P (NPP) and a 2 x 3 factorial arrangement of 2 dietary NPP concentrations (0.11 and 0.26%) with 2 phytase sources [Natuphos (BASF, Mt. Olive, NJ) and Phyzyme (Danisco Animal Nutrition, Carol Stream, IL)] and without phytase. Dietary NPP had significant effects on feed intake, NPP intake, total P intake, egg production, egg weight, egg mass, egg specific gravity, and excreta P. The addition of Phyzyme or Natuphos significantly increased egg production and egg mass of hens fed the P-deficient diet (0.11% NPP) to levels that were similar to hens fed the control diet containing 0.38% NPP. Feed intake of hens fed the diets supplemented with Phyzyme or Natuphos was significantly less than that of hens fed the control diet containing 0.38% NPP. Phyzyme or Natuphos supplementation in the diets containing 0.11% NPP had significantly reduced excreta P of the control diet (approximately 58 and 54%, respectively) with no adverse effect on egg production and egg mass. There were no significant differences in feed intake, NPP intake, total P intake, egg production, egg weight, egg mass, feed conversion, egg specific gravity, mortality, BW, and excreta P between the diets supplemented with Natuphos and the diets supplemented with Phyzyme. In conclusion, Phyzyme had the same positive effects on performance of commercial Leghorns fed corn-soy diets as Natuphos.

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