Phosphorus phase feeding and uterine and isthmus mucosal enzymes and minerals in relation to soft-shelled and shell-less egg production.

The relationships among phosphorus phase feeding, egg shell quality, and the activities and concentrations of several enzymes and minerals in the uterine and isthmus mucosae of hens at the time of oviposition were investigated. During the first 8 months of production (Phase 1), layer diets contained .3, .5, or .7% available phosphorus. Between 9 and 12 months of production (Phase 2), dietary available phosphorus was either increased or decreased by .2% phosphorus, or was left unchanged. No significant differences due to Phase 1 diets were demonstrated for hard-shelled (HS), soft-shelled (SS), or shell-less (SL) egg production, livability, egg weight, or specific gravity. Phase 2 diets had no significant effect on SS or SL egg production, livability, or egg specific gravity; however, decreasing dietary phosphorus reduced egg weight. Levels as high as .9% had no effect on specific gravity or HS egg production, while .1% dietary phosphorus was detrimental to HS egg production and feed consumption. No significant differences due to dietary available phosphorus or egg type (SS vs. HS) were demonstrated for uterine or isthmus mucosal enzyme activities or mineral contents, with one exception. Higher inorganic phosphorus concentrations were found in the uterus of HS egg layers when compared to levels in the uterus of SS egg layers and the isthmus of HS and SS egg layers. Acid phosphatase and carbonic anhydrase activities, and total calcium levels were significantly higher in the isthmus than the uterus, while alkaline phosphatase and pyrophosphatase activities, and inorganic phosphorus levels were significantly higher in the uterus than the isthmus.(ABSTRACT TRUNCATED AT 250 WORDS)