Calcium and Phosphorus Metabolism and Eggshell Thickness in Laying Hens Producing Thick or Thin Shells

Abstract

Two experiments were carried out to investigate the Ca and P metabolism of hens laying thick- (THK) or thin-shelled (THN) eggs on shell-forming days (SF) and days on which shell formation does not occur (NSF). In Experiment 1, 10 hens identified as producing THK or 10 hens producing THN eggs were offered a diet containing 3.5% Ca and .4% available P. Feed consumption, egg production, egg weight, egg deformation, and shell weight were recorded over 8 days. Shells and excreta were collected daily for Ca and P analysis. Feed, Ca, and P intake did not differ significantly (P greater than 0.5) between the two groups of hens, however, feed intake and Ca retention increased significantly (P less than .05) on SF compared with NSF days. The THK hens retained significantly (P less than .05) more Ca compared with THN hens. No differences (P greater than .05) were recorded for egg production, although there were differences (P less than .05) in egg weight and shell deformation between the two groups of hens. Increased egg weight did not account for differences (P less than .05) in eggshell deformation. Although percentage shell Ca was not significantly different (P greater than .05), total shell Ca was different (P less than .05) between the two groups. In Experiment 2, both groups of birds (THK and THN) were allowed simultaneous access to two different diets, a high-energy, high-protein diet low in Ca and P, and a low-energy, low-protein diet high in Ca and P.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium levels and limestone particle size in the diet of commercial layers at the end of the first production cycle

“…The difference between results obtained by Clunies et al (1992), who worked with similar dietary Ca levels as the present study, and those verified here may be due to higher feed intake of the birds of Clunies' study, and therefore higher Ca intake, as compared to our birds. Faria (2002) observed that dietary Ca levels need to be increased as limestone particle size is reduced in order to maintain eggshell percentage.…”

“…However, Cheng & Coon (1990b) and Ito et al (2006) showed that coarser limestone particle size improved (increased) egg specific gravity as compared to finer particles. Clunies et al (1992) increased dietary Ca level from de 3.5 to 4.5%, and observed an increase in eggshell percentage. Chowdhury & Smith (2002) found an increasing linear effect of Ca level on eggshell weight.…”

Effect of limestone particle size on egg production and eggshell quality of hens during late production

“…A micrometer (0.01 mm) was used to make three shell thickness measurements per measurement point on the blunt end, equator and sharp end of individual eggs, resulting in a total of nine measurement readings per egg (Ehtesham & Chowdhury, 2002;Ahmad & Balander, 2003). After recording eggshell thickness, individual shells were stored for the determination of dry shell weight and shell ash content (Clunies et al, 1992). Eggshell quality variables such as egg surface area (Carter, 1975), shell weight per unit surface area (SWUSA) (Wells, 1967), percentage eggshell (Orban & Roland, 1990) and eggshell Ca (g) were calculated.…”

Critical points on egg production: causes, importance and incidence of eggshell breakage and defects

“…As indicated by Clunies, Parks and Leeson (1992), the skeleton is the only major alternate source of calcium available to the hen during shell formation though, previously, Buss and Guyer (1984) showed that the skeletal metabolism was not a limiting factor in determining whether a hen produces a "thick" or "thin" eggshell. The previous authors conducted a study to make comparative measurements of bone parameters in lines of hens genetically divergent producing thick and thin eggshells.…”

“…An interesting study was carried out by Clunies, Parks and Leeson (1992) to investigate Calcium and Phosphorus metabolism of hens laying thick or thinshelled eggs on shell forming days and days on which shell formation does not occur. Results indicated that the amount (in grams) of shell Ca (but not Phosphorus) were significantly greater (P<0.05) from hens producing thick eggshell compared with those selected to produce thin shelled eggs.…”