PHYSIOLOGICAL PARAMETERS REGULATING THE PRODUCTION OF SOFT-SHELLED AND SHELL-LESS EGGS BY LAYING HENS (PHOSPHORUS, MOLT, OVIDUCT ENZYMES)

PHYLLIS M KLINGENSMITH, Purdue University

Abstract

Hard-shelled (HS) egg production and feed consumption were lower and egg specific gravity was higher among hens consuming .2% vs. .3 or .4% available phosphorus diets, while hen livability and the production of soft-shelled (SS) or shell-less (SL) eggs were not significantly affected by diet during 11 months of production. Premature oviposition of HS and SL eggs induced by intrauterine injection of 200 mM phosphate 5 hours (HS egg in utero) or 15 hours (SL egg in utero) prior to expected oviposition. Uterine fluid inorganic phosphorus and total calcium and plasma inorganic phosphorus levels were similar between high and low incidence groups of SS or SL egg layers, 5 hours after the egg entered the uterus. Higher plasma calcium in the high vs. the low incidence group may reflect a differential rate of calcium utilization in utero. Layer diets containing .3, .5, or .7% availabe phosphorus were fed continuously during the first 8 months of production (Phase 1). These diets were increased or decreased by .2% phosphorus or were left unchanged between 9 and 12 months of production (Phase 2). No significant differences due to Phase 1 diets were demonstrated for HS, SS, or SL egg production, feed efficiency, livability, egg weight, or egg specific gravity. Altering dietary phosphorus by .2% during Phase 2 had no significant effect on SS or SL egg production, livability, or egg specific gravity; however, decreasing dietary phosphorus by .2% reduced egg weight. Levels as high as .9% available phosphorus had no effect on specific gravity or HS egg production, while .1% available phosphorus was detrimental to HS egg production, feed consumption, and feed efficiency. Activities of uterine and isthmus pyrophosphatase, acid and alkaline phosphatases, and carbonic anhydrase at oviposition were not related to shell quality or dietary phosphorus. The importance of egg weight and shell thickness in establishing the fundamental relationships between the physical dimensions, air pore characteristics, water vapor conductance, and shell mineral contents of HS and SS eggs laid by force molted and nonmolted hens is described. A molt-induced improvement in shell quality was related to increased shell calcium content, while the thicker shells of afternoon eggs were associated with increased shell phosphorus content.

Degree

Ph.D.

Subject Area

Livestock

COinS