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

Whitening of brown-shelled eggs: mineral composition of uterine fluid and rate of protoporphyrin deposition

Changes in the mineral composition of uterine fluid during shell formation and the rates of color appearance and porphyrin deposition on the shell were measured in two subpopulations of brown egg-laying hens with familial histories of low or high incidences of shell whitening. Increases in shell weight and shell breaking strength were correlated with, and proportional to, time spent by the egg in the uterus and were similar in both subpopulations. Shell reflectance decreased and the amount of porphyrin deposited increased linearly 20 to 24 h after oviposition of the preceding egg. Porphyrin deposition was slightly higher at the 23-h stage in the high whitening population but similar amounts of porphyrin were deposited on the shell during the final stage of shell formation in both groups. The coating on the shell responsible for whitening was deposited during the hour prior to oviposition. Uterine fluid pH, pCO2, bicarbonate, and ionized Ca concentrations changed during shell formation but these changes were not related to the incidence of whitening. A milieu supersaturated with calcite solubility product was observed whatever the stage of shell formation. Inorganic phosphorus was not detectable in the uterine fluid whatever the stage of shell formation. The soluble phosphorus fraction of uterine decreased 22 h after oviposition and phosphorus deposition on the shell increased. At the end of egg formation uterine fluid could not be collected. It was concluded that shell whitening was associated with changes in the kinetics of porphyrin deposition rather than with changes in the amount of porphyrin deposited or modifications of uterine fluid composition.

Effects of vitamin D3 metabolites on physiological traits of White Leghorn hens

This study was conducted to determine the effect of feeding vitamin D3(D3) metabolites on BW of hen, weight of uterus, plasma Ca, jejunal and uterine adenosine triphosphatase (ATPase), and carbonic anhydrase. At 416 days of age each of 7 groups of laying hens was fed the basal ration supplemented with one of 7 concentrations (micrograms per kg) of D3 or its metabolites as treatments: 0 micrograms of D3; 27.5 micrograms of D3; 3, 5, or 7 micrograms of 1,25(OH)2D3; 5 micrograms of 24,25(OH)2D3; and 5 micrograms of 24,25(OH)2D3 plus 5 micrograms of 1,25(OH)2D3. Treatment effects were compared at various periods after the start of the study. Hens fed the unsupplemented ration had lower (P less than .05) values for all traits than hens fed the D3-supplemented ration by 162 days after the start of treatment. In a comparison of all dietary treatments except the one involving 0 micrograms D3, from 154 to 161 days after the start of the experiment, treatment effects were significant (P less than or equal to .05) for BW, uterine ATPase, and carbonic anhydrase; hens fed 5 micrograms of 24,25(OH)2D3 per kg of ration ranked the lowest of all treatment groups for these traits. Hens fed 27.5 micrograms of D3 and those fed 5 micrograms of 1,25(OH)2D3 per kg of ration did not differ (P greater than .05) for any traits studied. The results suggest that 5 micrograms of 1,25(OH)2D3 per kg of ration can replace 27.5 micrograms of D3 per kg of ration but that 5 micrograms of 24,25(OH)2D3 per kg of ration tends to have a negative effect on physiological systems of the hen.