Effect of Dietary Phosphorus Level and Source on Productive Performance and Egg Quality of Two Commercial Strains of Laying Hens

Abstract

An experiment was conducted to study the influence of dietary total phosphorus (TP) level and source on the performance of two strains of commercial layers for two consecutive production years (26 to 68 and 76 to 116 weeks of age, respectively). Diet 1 contained .4% TP; Diets 2, 3 and 4 contained .5, .6, and .7% TP with supplemental P from dicalcium phosphate (DCP); Diets 5 and 6 contained .5 and .6% TP, respectively, with supplemental P from a sample of raw rock phosphate (RRP-1); Diets 7 and 8 contained .5 and .6% TP, respectively, with supplemental P from a second sample of raw rock phosphate (RRP-2). Calcium level was 2.75% in all diets, and crushed oyster shell provided ad libitum to all birds increased the total calcium to about 3.00%. Diet 1 was inferior to the average of all supplemented diets relative to feed consumption rate (P less than .005) and egg weight (P less than .005) during the first year. Diet 1 was also inferior relative to egg production rate (P less than .01), feed consumption rate (P less than .005), and egg weight (P less than .005) during the second year, whereas it was superior in shell quality (P less than .05) during the first year. Increasing TP from DCP resulted in a significant linear increase in feed consumption (P less than .05), feed conversion ratio, and Haugh units (P less than .005). Increasing TP from DCP also resulted in a significant linear decrease in shell quality (P less than .05) and significant linear and quadratic decreases in egg weight (P less than .005) during the first year. During the second year, increasing TP from DCP resulted in a significant linear decrease in egg production rate (P less than .005) and feed efficiency but significant linear (P less than .01) and quadratic (P less than .05) increases in feed consumption, and significant linear and quadratic increases (P less than .005) in Haugh units. Hens receiving RRP diets responded differently during the first and second years. The DCP supported greater egg weight than the RRP during the second year and permitted better feed conversion during both years. Strain A produced larger eggs than Strain B regardless of treatment (P less than .005). When egg production rate and most other response criteria were considered, .5% TP with DCP as the supplemental source gave the best results in both production years. A TP of .6% from RRP-2 gave similar results in both years.

Determination of Phosphorus Requirement for Post Molted Laying Hens using Nonlinear and Multivariate Nonlinear Mixed Effects Models

“…Only two studies by Said et al (1984) and Snow et al (2004) fed different phosphorus levels throughout the second cycle and reported requirement of 0.3 and more than 2 g/kg of diet respectively. Said et al (1984) and Snow et al (2004) have used general linear model and treatment mean differences for determination of AP requirement. In the current study, AP requirement was evaluated using the recently developed method (Robbins et al, 2006) and approaches and various nonlinear models were fitted to the data.…”

“…However, fewer studies have investigated AP requirement of molted laying hens (Holder, 1981;Said et al, 1984;Bar et al, 2002 andSnow et al, 2004). Only two studies by Said et al (1984) and Snow et al (2004) fed different phosphorus levels throughout the second cycle and reported requirement of 0.3 and more than 2 g/kg of diet respectively. Said et al (1984) and Snow et al (2004) have used general linear model and treatment mean differences for determination of AP requirement.…”

“…Only two studies by Said et al (1984) and Snow et al (2004) fed different AP levels throughout the second cycle and reported requirement of 0.3 and more than 2 g/kg of diet respectively. Said et al (1984) and Snow et al (2004) have used general linear model and treatment mean differences for determination of AP requirement.…”

“…Only two studies by Said et al (1984) and Snow et al (2004) fed different AP levels throughout the second cycle and reported requirement of 0.3 and more than 2 g/kg of diet respectively. Said et al (1984) and Snow et al (2004) have used general linear model and treatment mean differences for determination of AP requirement. With multiple range tests, the actual requirement can only be on or between two levels of the nutrient that were fed, and there is no way to tell precisely what it is (Pesti et al, 2009).…”

“…Results from multiple range tests are also dependent on the experimenter's arbitrary adoption of a level of significance. Said et al (1984) and Snow et al (2004) suggested that evaluation of AP requirement of post molted laying hens is necessary because of lacking appropriate studies in this area. Recently, a newly developed nonlinear models and procedures such as non-linear (NLIN) and non-linear mixed effect (NLMixed) allowing us to fit many nonlinear functions for estimating the nutrient requirements of animals accurately.…”