Title

Effect of a Partial Replacement of Limestone by a Caso4-Zeolite Mixture Combined With a Slight Protein Reduction on Production Indices, Egg Quality, and Excreta pH in Laying Hens

Document Type

Article

Publication Date

6-20-2012

Description

A control diet (CN diet; 17.4% CP and 4.37% Ca) was compared with an experimental diet with a 0.4-percentage-unit reduction in protein content and a 35% replacement of limestone by a CaSO4-zeolite mixture [5.76% CaSO4 and 1.18% zeolite; reduced-emission diet (RE diet)] in laying hens to evaluate the effects on apparent N retention, egg production, egg composition, and excreta pH measured at excreta collection or after 7 d of storage. In previous studies, it was demonstrated that the RE diet reduced NH3 emissions by 48%. Laying hens (192 total; 48 replicate cages per diet, with 2 hens per cage) were fed experimental diets from 33 to 49 wk of age. Apparent N retention (48.2%), egg production (83.6%), and number of shell-less eggs (0.18%) were not affected by the diet. Eggs tended to be heavier (59.4 vs. 58.8 g/egg, P = 0.06), and yolk percentage (29.7 vs. 29.0%, P = 0.013) was greater with the RE diet. At 48 wk of age, the total solids content per egg was also greater from hens fed the RE diet (13.2 vs. 12.6 g/egg, P = 0.032). Other egg components were not influenced by diet. Thus, a slight reduction in dietary CP content and replacing a portion of the Ca from CaCO3 with CaSO4 did not affect egg production nor did it impair shell quality. At the end of the experiment, excreta were collected from all cages (excreta from 3 cages were mixed and pooled; 16 pools of excreta per diet). At collection, excreta of hens fed the RE diet had lower pH (5.89 vs. 6.54, P < 0.001) than those of hens fed the CN diet. After 7 d of storage, excreta pH of hens fed the RE diet continued to be lower (6.30 vs. 8.36, P < 0.001). The reduction of excreta pH, even after 7 d of storage, may control nitrogenous emissions from excreta by maintaining excreted N as NH4+.

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