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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. [ABSTRACT FROM AUTHOR]

A 4 × 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 I 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. [ABSTRACT FROM AUTHOR]

β-Mannanase (Hemicell) is a unique enzyme-based feed ingredient that can hydrolyze β-mannan, an antinutritional fiber in feed. Because soybean meal contains β-mannan and its derivatives, addition of β-mannanase may improve soybean-meal utilization. The purpose of this study was to evaluate the effect of β-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 β-mannanase) and diet 3 (low-energy diet without β-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 β-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 β-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 β-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, β-Mannanase supplementation improved energy utilization of corn-soybean layer diets and has potential to reduce the cost of practical laying hen diets containing β-mannan. [ABSTRACT FROM AUTHOR]

The article presents an abstract of the study "Effect of Increasing Dietary Energy While Maintaining a Constant Energy/Lysine Ratio on Performance, Egg Components, Egg Solids, Egg Quality and Profits in Seven Commercial Leghorn Strains During Second Cycle," by P. K. Gunawardana and colleagues.

The article presents an abstract of the study "Molting 16 White and Brown Egg Laying Strains Without Feed Withdrawal," by M. M. Bryant and colleagues.

An abstract of the article "Production Control I: The Key to Profits," by D. A. Roland and colleagues is presented.

The article presents an abstract of the study "Effect of Peptides on Performance, Egg Components, Egg Solids and Egg Shell Quality of Hy-line W-36 Hens Fed Different Protein Levels in Second Cycle," by P. K. Gunawardana and colleagues.

The article presents an abstract of the study "Performance Comparison and Nutrition Requirement of Eight Commercial Brown Egg Layer Strains ," by P. K. Gunawardana and colleagues.

Two experiments of 4 × 2 × 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. [ABSTRACT FROM AUTHOR]

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 fly-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 × 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. [ABSTRACT FROM AUTHOR]

Four experiments were conducted to determine whether synthetic lysine, isoleucine, threonine, and tryptophan (LITT) or TSAA supplementation to diets formulated based on lysine improved egg weight (EW) and hen performance. In Experiment 1, diets were formulated with three TSAA levels (0.65,0.72, and 0.81%). These diets were fed with and without adding lysine and isoleucine each at 0.055% and threonine and tryptophan each at 0.022%. Treatments were randomly assigned to 960 Hy-Line W-36 hens in eight replicates per treatment (20 birds/replicate). Inclusion of LITT improved (P < 0.05) EW within 2 wk with no TSAA x LITT interaction. Inclusion of LITT also increased average feed consumption (FC) by 1.4 g/d (P < 0.01). However, no effect (P > 0.05) of LITT was observed on egg production (EP), egg specific gravity (SG), or BW. The EW, EP, and FC increased linearly (P < 0.05) as dietary TSAA increased. The TSAA had no effect on SG or BW. In Experiment 2, supplemental LITT were removed to determine how rapidly hens lose the effect of LITT on performance. Within 2 wk, the effect of LITT on EW was lost. Average EW, EP, and FC of hens fed higher TSAA levels remained higher (P < 0.05) than hens fed 0.65% TSAA. In Experiment 3, all hens were fed a diet containing 0.65% TSAA to determine the time it takes to lose the effect of TSAA supplementation. The TSAA supplementation effect on EW, EP, and FC observed in the previous two experiments was lost within 1 wk. In Experiment 4, hens were again fed diets similar to Experiment 2 to confirm the time required for TSAA supplementation to improve EW. Within 1 wk, hens fed 0.72 or 0.81% TSAA improved (P < 0.05) EW over hens fed 0.65% TSAA. It was concluded that hens fed diets formulated based on lysine were deficient in LITT. Hens responded to the inclusion or removal of supplemental LITT and TSAA within 1 to 2 wk.

Two studies were conducted to determine whether cage density and prior dietary nonphytate P (NPP) level affect hens' P requirements. In Experiment 1, hens were housed at three cage densities (300, 400, and 600 cm2 or 46.5, 62.0, and 93.0 inches2/hen) and fed four levels of NPP (0.15, 0.25, 0.35, and 0.40%) for 6 wk to determine the effect of cage density on the P requirement. Egg production (EP), feed consumption (FC), egg weight (EW), and egg specific gravity (ESG) were measured to evaluate performance. Cage density influenced EP within Week 1 (P < 0.01), and during Weeks 5 and 6, there was a cage density x NPP-level interaction (P < 0.05). At 300 cm2, EP was more severely affected by 0.15 and 0.25% NPP than at 400 and 600 cm2. A linear decrease (P < 0.001) in FC was observed because of decreased NPP. Hens at 300 cm2 consumed 4 g less feed/hen per d than hens at 400 cm2. A linear decrease in EW was observed as the NPP level decreased (P < 0.01) from 0.25 to 0.15%, and there was no effect of cage density. Experiment 2 was conducted to determine the effect of prior dietary P levels on time required to create a P deficiency. Hens fed 0.4% NPP were divided into two groups and fed 0.25 and 0.4% NPP for 4 wk. At the end of 4 wk, hens fed 0.25% NPP were further divided into three groups and were fed diets containing 0.09, 0.25, and 0.30% NPP for an additional 6 wk. Hens fed 0.4% NPP were divided into three groups and fed diets containing 0.09, 0.4, and 0.45% NPP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced EP by 8.5 and 6.8%, respectively, within 3 wk. Prior NPP levels had no influence on time required to create a P deficiency in terms of EP. Reduction of NPP from 0.4 and 0.25% to 0.09% reduced (P < 0.05) FC. A decline in FC occurred 2 wk earlier in hens previously fed 0.4% than those fed 0.25% NPP. This result indicates that hens fed 0.4% NPP became P deficient more quickly than hens fed 0.25%. We concluded that cage density and prior NPP level affect the hen P requirements or time required to create a P deficiency.

An experiment was conducted to determine the effect of feeding method (constant vs variable) and method of formulation (lysine vs protein) on the performance and profits of first cycle, phase 2 DeKalb Delta hens from 40 to 52 wk of age as influenced by egg and feed prices. Treatments 1 to 5 were formulated based on lysine to contain 0.65 to 0.81% TSAA and fed continuously regardless of feed consumption (constant feeding). Treatments 6 to 10 and 11 to 15 were formulated based on lysine to supply 570 to 650 mg TSAA and protein to supply 580 to 660 mg TSAA per hen per d, respectively, and fed based on feed intake. Dietary TSAA level had no overall significant effect on feed consumption, egg production, egg weight, mortality, or body weight. Hens fed diets using the constant method of feeding had significantly higher egg production, egg weight, egg specific gravity, and body weight than hens fed diets formulated based on lysine or protein using the variable method of feeding. When the treatments in the two variable feeding methods were compared, feed consumption was significantly higher for hens fed diets formulated based on protein whereas egg production, egg weight, egg specific gravity, and body weight were not different. It was concluded that method of formulation (lysine vs protein) and TSAA levels required for maximum profits can vary from at least 570 to 821 mg per hen per d depending upon energy and protein cost.

An experiment was conducted to determine whether optimizing profits, as well as eggshell and skeletal strength, by manipulation of dietary Ca level has any influence on either egg weight, egg production or feed consumption during the first 12 wk of production (Weeks 20 to 32, Phase 1). Hens were housed at two environmental temperatures (15.6 to 23.3 and 21.1 to 28.9 C) and fed six diets from 20 to 32 wk of age containing 2.5 to 5.0% Ca with increments of 0.5% and with ME levels ranging from 2,719 to 2,950 kcal/kg, respectively. Egg specific gravity, egg production, egg weight, and feed consumption were determined at weekly or biweekly intervals. At 32 wk of age, plasma Ca, bone density, and bone breaking strength were determined. Results indicated that environmental temperature had no influence on egg production but hens housed at the lower environmental temperature had an increase in egg weight, egg specific gravity, and feed consumption. Increasing dietary Ca level increased egg production, egg specific gravity, feed consumption, ionic plasma Ca, bone density, and bone breaking strength and had no adverse effect on egg weight. It was concluded that Hy-Line W-36 hens could be fed diets containing as much as 5% Ca with no adverse effect on egg production, egg weight, or feed consumption and that Hy-Line W-36 hens (Phase 1) under conditions described should be fed diets containing a minimum of 4.25% Ca (3.4 to 3.6 g per hen per d) to 4.5% Ca (3.6 to 3.8 g per hen per d). Calcium intake should range from 3.0 g per hen per d at 21 wk of age to 4.2 g per hen per d at 32 wk of age.

This study was designed to determine the differences in response of early-maturing (EM) and late-maturing (LM) Single Comb White Leghorn pullets within a flock to marginal or low dietary phosphorus. Various levels of dietary phosphorus were fed to EM and LM Leghorn pullets from 18 wk of age until the age of peak egg production (24 wk). The dietary phosphorus levels were 0.40, 0.45, 0.50, 0.55 and 0.70 g total phosphorus (tP)/100 g diet, corresponding to calculated available phosphorus values of 0.18, 0.23, 0.28, 0.33 and 0.48 g/100 g, respectively. At 0.70 and 0.55 g tP/100 g, the plasma inorganic phosphorus, Ca++ and urine calcium concentrations did not differ between EM and LM pullets, whereas LM pullets had a better bone status than EM pullets as reflected by bone mineral content, bone density and bone breaking strength. As dietary phosphorus was lowered from 0.55 to 0.4 g tP/100 g, the plasma concentration of inorganic phosphorus dropped and that of Ca++ increased at greater rates in LM pullets than in EM pullets. The magnitude of decline in bone status was also greater in LM than in EM pullets when dietary phosphorus was lowered from 0.55 to 0.40 g tP/100 g. The maximum incidences of osteoporosis and mortality were observed in LM pullets fed 0.40 g tP/100 g followed by LM pullets fed 0.45 g tP/100 g diet. We conclude that when early layer diets contain marginal or low levels of phosphorus, the severity of adverse effects are greater in LM pullets than in EM pullets.

Two experiments were conducted to determine whether 1) serum Si and Al is increased in hens intubated with sodium zeolite A (SZA); and 2) dietary cholecalciferol (vitamin D3) influences the absorption of Si or Al by hens fed SZA. In Experiment 1, hens were intubated at oviposition with 0, 1, or 2 g of SZA. Blood samples were collected from the brachial vein at oviposition, and 4, 8, 12, 16, and 20 h postoviposition. Serum samples were analyzed for Si and Al. Peak serum Si and Al were observed at 4 and 8 h postoviposition, respectively. In Experiment 2, hens consumed commercial layer diets ad libitum containing five levels of dietary cholecalciferol (100 to 500 IU/kg) with or without .75% SZA for 6 wk. Blood samples were collected at the end of the 6-wk period by cardiac puncture at oviposition. When dietary cholecalciferol was increased from 100 to 200 IU/kg of diet there was an increase (P < .05) in serum Si but not Al. Levels of cholecalciferol above 200 IU/kg did not produce an additional increase in serum Si. The results showed increased (P < .01) serum concentrations of Si and Al for hens intubated with or fed SZA. It was concluded that Si and Al from SZA are absorbed by commercial Leghorn hens, and a possible involvement of Si or Al should be considered in the mechanism of action of SZA associated with improved eggshell quality and bone development.

A study was conducted to determine the appropriate sample size required for various methods used to assess tibial bone status in commercial Leghorn hens. The methods used were in vivo bone mineral content (BMC), in vivo bone density (BD), in vitro BMC, in vitro BD, tibia bone breaking strength (TBS), and percentage bone ash (BA). Dietary total P levels of .4, .45, .5, .55, and .7% were used as treatment source of variation. Twenty hens were sampled randomly to represent each dietary treatment. The CV for each bone status comparison method was estimated and was used in a procedure to estimate the sample size requirement for detecting a difference of delta between treatments. The sample size required to detect the difference between treatment means varied depending on 1) the method used to compare bone status 2) the difference between the treatment means to be detected as significant (delta); and 3) the level of significance (alpha) assumed. The sample size required for various methods are tabulated at .01, .05, and .1 level of significance and for 2.5, 5,7.5, 10, 15, and 20% delta. To detect an actual difference of 5% from the mean to be significant, at the .05 level of significance, a sample size of 44, 22, 31, 23, 47, and 85 hens per treatment would be necessary for in vivo BMC, in vivo BD, in vitro BMC, in vitro BD, TBS, and BA methods, respectively. The estimated sample size values would help researchers in designing experiments that involve bone status comparison of commercial Leghorn hens.