Three experiments were conducted to determine possible mechanisms involved in improving eggshell quality with sodium zeolite A (SZA) (trade name Ethacal feed component), and cholecalciferol (vitamin D3) by studying the effect of dietary supplementation of SZA and vitamin D3 on plasma 1,25-dihydroxycholecalciferol [1,25-(OH)2 D3], ionic calcium (Ca++), normalized calcium (nCa++), total calcium (TCa), percentage Ca++ to TCa (PCa++), pH, and phosphorus (P). In Experiment 1 (2 x 2 factorial arrangement of treatments), two levels of SZA (0 and .75%) and two levels of vitamin D3 (0 and 175 ICU/kg) were fed. In Experiment 2, five levels of vitamin D3 (100 to 500 ICU/kg) and two levels of SZA (0 and .75%) were fed using a 2 x 5 factorial arrangement of treatments. In Experiment 3, hens were fed two levels of SZA (0 and .75%). Blood samples were collected at 0 (Experiments 1, 2, and 3), 7, 14, and 21 h (Experiment 3) postoviposition (POP). In Experiments 1 and 2, decreasing vitamin D3 decreased plasma 1,25-(OH)2 D3 and P. Plasma TCa decreased when 0 ICU vitamin D3 was fed (Experiment 1), but was not affected by vitamin D3 level in Experiment 2. Supplemental SZA had no effect on plasma 1,25-(OH)2 D3, TCa, or P in Experiments 1 and 2. In Experiment 3, plasma 1,25-(OH)2 D3 and P peaked at 14 h POP, but Ca++ was lowest at 14 h POP. Circadian rhythms for plasma 1,25-(OH)2 D3, Ca++, and P were not affected by SZA. There were no significant effects due to dietary SZA on plasma 1,25-(OH)2 D3, TCa, Ca++, PCa++, nCa++, pH, or P.(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were conducted to determine whether 1) serum Si and Al is increased in hens intubated with sodium zeolite A (SZA); and 2) dietary cholecalciferol (vitamin D3) influences the absorption of Si or Al by hens fed SZA. In Experiment 1, hens were intubated at oviposition with 0, 1, or 2 g of SZA. Blood samples were collected from the brachial vein at oviposition, and 4, 8, 12, 16, and 20 h postoviposition. Serum samples were analyzed for Si and Al. Peak serum Si and Al were observed at 4 and 8 h postoviposition, respectively. In Experiment 2, hens consumed commercial layer diets ad libitum containing five levels of dietary cholecalciferol (100 to 500 IU/kg) with or without .75% SZA for 6 wk. Blood samples were collected at the end of the 6-wk period by cardiac puncture at oviposition. When dietary cholecalciferol was increased from 100 to 200 IU/kg of diet there was an increase (P < .05) in serum Si but not Al. Levels of cholecalciferol above 200 IU/kg did not produce an additional increase in serum Si. The results showed increased (P < .01) serum concentrations of Si and Al for hens intubated with or fed SZA. It was concluded that Si and Al from SZA are absorbed by commercial Leghorn hens, and a possible involvement of Si or Al should be considered in the mechanism of action of SZA associated with improved eggshell quality and bone development.

Two experiments were conducted to elucidate possible explanations for the adverse interaction of sodium aluminosilicate (ZA) and low phosphorus on egg production. In Experiment 1, hens were fed available phosphorus at two levels (.40 and .31%) and from three sources (dicalcium phosphate, defluorinated phosphate, and meat and bone meal). Two levels (0 and .75%) of ZA were concomitantly fed with these treatments. In Experiment 2, hens were fed two levels (.30 and .20%) and two sources (dicalcium phosphate and defluorinated phosphate) of phosphorus with and without ZA (0 and .75%). In both experiments, egg production, egg specific gravity, feed consumption, and egg weight were measured. In Experiment 2, plasma sodium, potassium, chloride, total and free calcium, and phosphorus were also monitored. Results of both Experiments indicated that ZA significantly increased egg specific gravity; whereas, phosphorus level and source had no effect on egg specific gravity. Egg production was influenced by ZA level, phosphorus source, and phosphorus level with significant phosphorus source by phosphorus level interactions. In Experiment 1, ZA reduced egg production at the higher phosphorus level when dicalcium phosphate or defluorinated phosphate was used but not at the lower phosphorus level. Egg production was not influenced by ZA when meat and bone meal was the source of phosphorus. In Experiment 2, ZA reduced egg production more at the lowest level of phosphorus and more when the phosphorus source was defluorinated phosphate than when it was dicalcium phosphate but the interaction was not significant. Sodium aluminosilicate had no influence on egg weight, but it did reduce feed consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

To determine whether particle size of CaCO3 influences the hen's response to sodium zeolite A (ZA), two experiments were conducted. In Experiment 1, hens were fed 0, .75, and 1.50% ZA for 6 wk with and without a Na correction. At the end of the 4th wk, pullet-sized limestone was substituted for 50% of the added fine granular limestone in the diet containing no ZA. In Experiment 2, hens were fed diets containing 0, .68, and 1.36 ZA for 8 wk with and without one-half of the added fine granular limestone substituted for oyster shell. No correction for Na was made. A dietary calcium concentration of 2.75% was used in Experiment 1 and 3.5% in Experiment 2. Egg specific gravity, egg production, feed consumption, and egg weight were measured. Sodium zeolite A increased egg specific gravity, and the beneficial effects of ZA were maintained during Weeks 5 and 6 when pullet-sized limestone was added to the control diet containing no ZA (Experiment 1). Oyster shell and ZA improved egg specific gravity in Experiment 2 and the effect was additive. Dietary treatments had no effect on egg production or egg weight in Experiments 1 or 2 and there was no effect on feed consumption (Experiment 1). Feed consumption was reduced by ZA, when hens were fed oyster shell, but not when they were fed ZA with fine granular limestone (Experiment 2). It was concluded that the beneficial effect of ZA on egg specific gravity was independent of particle size of CaCO3 in the diet.

The mechanism of action of zeolite A (ZA) on eggshell quality could be related either to its ion-exchange properties or to individual ZA elements (Al or Si). Two experiments were conducted to determine 1) whether any ZA passes through the digestive system in its original form; and 2) whether any Al and Si absorption occurs. In Experiment 1, unfed hens were intubated with either 0 or 5 g ZA at oviposition. In Experiment 2, fed and unfed hens were intubated at oviposition with 0, 1, or 2 g ZA. At the subsequent oviposition, liver and kidney tissues, excreta, urine, bile, and plasma were collected and analyzed for Al, Si, Na, K, and P. The results indicated that approximately 7% of the intubated ZA passed through the digestive system in its original form (Experiment 1). As the intubated level of ZA increased, excreta Al and Si (P < .0001), urine Si (P < .005), and urine Al (P < .07) also increased (Experiment 2). Aluminum recovery from excreta ranged from 75 to 93% of the quantity intubated in all treatments. Corresponding values of Si from excreta of unfed and fed hens ranged from 76 to 81% and 58 to 60%, respectively. The P content of excreta was not influenced by ZA. However, excreta P was greater (P < .0001) in unfed than in fed hens. Neither plasma electrolytes (Na, K, and P) nor Al or Si levels in either liver or kidney were influenced by ZA.(ABSTRACT TRUNCATED AT 250 WORDS)