Influence of limestone particle size in diets for hens and oviposition time on eggshell quality

Abstract

Eggshell quality was studied in three groups of Issa Brown hens, from 73 to 78 weeks of age. Group 1 (control) received a basal diet with 3,8 % Ca and 0,35 % available P, in which pulverized limestone (particle size 0,02 mm) was the main source of Ca. The other two groups of hens were fed diets of the same composition but differing in the supplemented limestone particle size. In group 2 and 3 60 % of the pulverized limestone was substituted with a granular form, of particle size 1,10-1,40 mm. and 1,42-2,80 mm respectively. Eggs for examination were collected at three periods of time: 7-9 hours, 11-13 hours and 15-17 hours. There were significant effects of particle size and oviposition time on eggshell quality. Egg mass and shell deformation decreased, while shell breaking force, shell thickness and shell mass increased with increasing oviposition time. At the afternoon period of laying, significantly higher (p (lt) 0,05) breaking force (5,0 kg) and lower shell deformation (21,9μ) were obtained in eggs of hens fed on the diet incorporating the granular form of limestone (particle size 1,10-1,40 mm) than eggs of hens fed only pulverized limestone. It was shown that there are possibilities for improving eggshell quality, in older hens, by a combination of pulverized and granular limestone in the diet, as a source of calcium.

Ispitivanje je obavljeno na 90 nosilja Issa Brown, u uzrastu od 73-78 nedelja, podeljenih u tri grupe. Sve grupe su za ishranu dobijale smeše istog sastava, u kojima je glavni izvor kalcijuma bio mleveni mermer. Razlike između grupa su bile u veličini čestica mermera dodatog u hranu. Grupa 1, (kontrola), je dobijala smešu sa praškasto mlevenim mermerom (kreda), veličine čestica 0,02 mm. U smeši za grupu 2 oko 60 % mermera je bilo sa krupnijim česticama (1,10-1,40 mm), a 40 % u obliku krede. U smeši za grupu 3 oko 60 % mermera je bilo sa još krupnijim česticama (1,42-2,80 mm), a 40 % u obliku krede. Za ispitivanje kvaliteta ljuske jaja su sakupljana svakodnevno u tri vremenska intervala (vreme ovipozicije): 7-9 sati, 11-13 sati i 15-17 sati. Ustanovljeno je da sa vremenom ovipozicije opada masa jaja i deformacija ljuske, dok se vrednosti sile loma, debljine i mase ljuske povećavaju. Veličina čestica mermera dodatog u hranu, ispoljila je značajan uticaj na kvalitet ljuske jaja, izražen kroz deformaciju i silu loma. Jaja nosilja iz 2. i 3. grupe (krupnije čestice mermera), snesena popodne, imala su značajno (p (lt) 0,05) manje vrednosti deformacije (21,9 μ; 19,9 μ) i veće vrednosti sile loma ljuske (5,0 kg; 4,6 kg) u odnosu na jaja nosilja iz 1. grupe. U toku prepodnevnog perioda nošenja, jaja nosilja 1. i2. grupe su ispoljila veću silu loma u odnosu na jaja nosilja 3. grupe. Generalno, može se zaključiti da je 2. grupa nosilja (veličina čestica mermera 1,10-1,40 mm) pokazala najbolje rezultate i da je moguće poboljšati čvrstoću ljuske jaja, kod starijih nosilja, dodatkom u hranu izvesne količine mermera krupnijih čestica.