Impact of Layer Breeder Flock Age and Strain on Mechanical and Ultrastructural Properties of Eggshell in Chicken

Transcription

1 Interntionl Journl of Poultry Science 9 (): , 010 ISSN Asin Network for Scientific Informtion, 010 Impct of Lyer Breeder Flock Age nd Strin on Mechnicl nd Ultrstructurl Properties of Eggshell in Chicken G.N. Ryn, A. Gll, M.M. Fthi nd A.H. El-Attr Deprtment of Poultry Production, Fculty of Agriculture, Ain Shms University, Ciro, Egypt Astrct: This investigtion ws crried out to study mechnicl eggshell trits (weight, specific grvity, eggshell thickness nd eggshell reking strength) nd ultrstructurl properties from lyer reeder hens t different ges (5, 47 nd 61 weeks). The present results showed tht the rown eggshell hd significntly higher specific grvity, shell thickness nd reking strength compred to white eggshell. Concerning reeder flock ge, it could e noticed tht the ge of hen significntly ffected mechnicl eggshell trits, where specific grvity, shell thickness nd reking strength decresed significntly s the reeder ge ws dvnce. With respect to eggshell ultrstructurl properties, the rown eggshell hd significntly higher effective thickness (plisde %) compred to white ones. Opposite trend ws oserved for reltive cp thickness. With regrd to lyer reeder flock ge effect, the results indicted tht the effective thickness (plisde %) ws significntly decresed s the lyer reeder flock ge incresed. Conversely, the reltive cp thickness ws incresed with ge incresed. With respect to confluence trit, the present results oserved tht oth rown nd white eggs owned shells with similr vlues of confluence. Significnt difference oserved etween strins regrding fusion (erly or lte) trit. Type B's, type A's nd lignment trits in eggshell produced from older reeders ws significntly higher tht of younger reeders. Key words: Eggshell trits, reeder hen ge, older hens INTRODUCTION The reeding progrmme for lying trits pid considerle interest to the shell qulity. Economic losses ssocited with the incidence of eggshell defects re importnt when evluting the profitility of lyer opertion (Bell, 1998; Flock, 1995; Seelnd et l., 1995). Low egg qulity lmost leds to 5-8% loss in production (Krshvrz, 1994). The frequency of defective eggs my increse from 7-11% during the lying, collecting nd pcking stges of egg production. Thus shell qulity is one of the mjor prolems of egg production. Mintining qulity eggshells throughout the production cycle is desirle. Avin eggshell contins orgnic (3.5%) nd inorgnic (95%, lmost clcium cronte) frctions; it weighs out 5 g nd contins. g clcium, which represents out 38% of its weight (Nys et l., 1999). Mny fctors hve een found to ffect eggshell qulity, such s disese, nutritionl sttus of the flock, het stress nd ge (Roerts, 004). A decrese in eggshell qulity of older hens hs een reported y Elroussi et l. (1994). Egg production rte decreses nd egg weight increses s ge dvnces, lso egg composition chnge nd shell thickness decrese with production level nd ge of lyer (Summers nd Leeson, 1983; Seelnd et l., 1995; Mchl nd Simeonovov, 00). The decline in eggshell qulity s the hens ge my in prt e ttriuted to reduced intestinl clcium uptke s well s to incresed egg size (Al-Btshn et l., 1994). The increse in shell weight s hens ge ws not sufficient to compenste for the increment of egg weight, so tht the rtio of shell weight to egg weight decresed (Roerts nd Blney, 000). Ultrstructurl studies hve demonstrted tht the eggshell is comprised of there morphologiclly distinct clcified lyers (Solomon, 1991; Dennis et l., 1996; Frser et l., 1999). Bin (1991) suggested tht the orgniztion of the plisde columns is mjor determinnt of shell stiffness nd therefore of shell strength. Shell strength is directly relted to shell thickness (Khtkr et l., 1997) nd the plisde lyer comprises pproximtely two-thirds of the eggshell (Prsons, 198). Therefore, it is likely tht ltertions in the thickness of the plisde lyer, independent of structurl reorgniztion of the plisde columns, could ffect shell strength. Recent Trnsmission Electron Microscopy (TEM) studies (Dennis et l., 1996; Frser et l., 1999) hve reveled columnr clcite crystls in verticlly ligned mtrix ssocited with the verticl crystl lyer. Therefore, the ojectives of this reserch were to investigte the effects of reeder hen ge nd strin on mechnicl nd ultrstructurl of eggshell in lying hen reeder hens under previling Egyptin conditions. Corresponding Author: G.N. Ryn, Deprtment of Poultry Production, Fculty of Agriculture, Ain Shms University, Ciro, Egypt 139

2 MATERIALS AND METHODS Three hundred eggs (150 Brown nd 150 White) were otined from three lyer reeder flocks differed in stge of lying seson: erly stge (5 wk), mid stge (47 wk) nd lte stge (61 wk). Ech stge contining fifty eggs from ech of the three lying stges either for Brown nd W-36 lyer reeder flocks were rndomly tken to evlute the effect of strin nd reeder flock ges on mechnicl nd ultrstructurl properties of eggshell. Eggshell mechnicl trits: Eggs were individully weighed to the nerest 0.01 g using n electronic digitl lnce. Eggshell qulity mesurements were conducted using 60 eggs (10 eggs from ech lying stge within strins). Length nd width of egg were individully recorded y using digitl cliper. Shpe index, then, ws clculted y (width/length) x 100 ccording to (Crter, 1968). Specific grvity ws determined using the sline flottion method of Hempe et l. (1988). Briefly, Eggs re immersed sequentilly into series of sline solution of scending SG. Slt solutions were mde in incrementl concentrtion of in the rnge from The SG of ny egg is equl to SG of the SG of the solution in which it first flots. Egg volume ws estimted y mesuring the 3 quntity of wter dislodged in cm fter immersing the egg into known wter volume. The egg surfce in cm ws clculted y dividing shell weight on weight of 1 cm re ccording to (Hmilton, 1978). The strength of eggshell ws determined ccording to Fthi nd El- Shr (1996) using eggshell strength pprtus. The shell percentge ws clculted ccording to following eqution: Wet shell weight Shell percentge (%) = x100 Egg weight Shell thickness (mm) ws mesured t three different points in the middle prt of the egg (the equtor) using dil guge micrometer. Shell index (g/100 cm ) ws clculted ccording to following eqution: Shell weight (g)/shell surfce (cm ) x 100 (Suveur, 1988). Scnning Electron Microscopy (SEM) technique: 48 smples of eggshell were rndomly tken from Hy-Line Brown nd W-36 lyer reeder flocks t erly nd lte lying stge to investigte ultrstructurl vritions. The specimens were prepred y cutting piece (1 cm ) of shell from equtoril region of ech egg. The shell memrnes were crefully removed y first soking in wter. The loosely dhering memrnes were then gently peeled from the edge of the smple inwrds. To remove the remining tightly ound memrne fiers, ech smple ws then immersed overnight in 6% sodium hypochlorite, 4.1% sodium chloride nd 0.15% sodium hydroxide. Therefter the specimen ws rinsed with wter nd left to dry t room temperture. Following these preprtive tretments, two smples from ech egg were mounted in inner side uppermost nd in verticlly mnner on luminum stus, coted with gold for 3 min in n Emscope Sputter Coter. These smples were exmined using JEOL JSM-T330A scnning electron microscopy t 15 Kv. The incidence of ultr structurl vrints t the level of the mmmillry lyer ws ssessed ccording to the methodology nd terminology developed y the Poultry Reserch Unit, University of Glsgow (Bin, 1990,199; Solomon, 1991). The cross-sectionl lengths of plisde nd mmmillry lyers were directly mesured in µm using scling softwre provided with the SEM t mgnifiction of x 00. The totl thickness of ech specimen ws mesured s the distnce from its outermost surfce to the point where the sl cps inserted into the shell memrnes. The thickness of mmmillry lyer ws lso ssessed, this eing the distnce from the sl cps to the point t which the plisde columns first fused. Sutrction of these two mesures provided length of the plisde thickness or effective thickness (Bin, 1990; Solomon, 1991). Triplicte mesures were performed in ech cse nd the men vlues were used for the sttisticl nlysis. Sttisticl nlysis: Dt were sujected to two-wy nlysis of vrince with strin nd reeder flock ge using the Generl Liner Model (GLM) procedure of SAS User's Guide (000) ccording to the following model: Yij = µ + Si + Aj + (S*A)ij + eijk Where: µ = Overll mens Si = Strin effect (i = 1, ) Aj = Breeder flock ge effect (j = 1,, 3) (S*A)ij = Interction etween strin nd reeder flock ge eijk = Experimentl error When significnt differences mong reeder flock ge were found, mens were seprted using Duncn's multiple rnge tests. RESULTS AND DISCUSSION Egg weight nd dimension: Dt summrized in Tle 1 showed tht the effect of strin, reeder flock ge nd their interction on egg weight nd dimension. The rown reeder hens produced significntly hevier egg weight compred to the white ones. Similr results were otined y Potts nd Wshurn (1983); Curtis et l. (1985); Wshurn (1990) nd Bdwe (006). They reported tht the rown egg strins lid hevier eggs 140

3 Tle 1: Egg weight nd egg dimension trits s ffected y strin, reeder flock ge nd their interction (Mens±SE) Breeder flock ge (wk) Pro Trit Strin Overll S A S*A Egg weight (g) Brown 51.34± ± ± W ± ± ± Overll c NS Egg shpe index (%) Brown 77.13± ± ± W ± ± ± Overll NS 0.01 NS 3 Egg volume (cm ) Brown 49.0± ± ± W ± ± ± Overll NS Eggshell re (cm ) Brown ± ± ± W ± ± ± Overll NS Eggshell index (g/100 cm ) Brown 8.15± ± ± W ± ± ± Overll thn white egg ones. With respect to reeder flock ge effect, the present results showed tht the egg weight incresed s lyer's ge ws dvnced. Bumgrtner et l. (007) pointed out significnt effect of ge on egg weight in the Leghorn type hens. Also, Lukáš Zit et l. (008) found tht egg weight incresed with the lyer s ge. Concerning eggshell dimension trits, our results showed tht the rown lyer reeder hens produced eggs with higher shpe index compred to the white ones. Brnd et l. (004) found tht the egg shpe index for rown Is Wren Lyers ws 75.60% nd this vlue ws higher thn tht of white eggs produced from White Rock lyers (74.10%). Monir et l. (003) demonstrted to significnt decrese in egg shpe index with dvnced of reeder flock ge. Gunlu et l. (003) nd Brnd et l. (004) reported tht shpe index of the eggs decresed with ge ecuse shpe index is directly proportionl to egg width nd it is inversely relted to egg length, which implies tht with incresing ge, the rte t which eggs ecomes longer is fster thn rte of eing wider. The rown eggshell hd higher volume compred to white ones. With respect to ge effect, the present results showed tht the egg volume significntly incresed s reeder flock ge incresed. This result could e ttriuted to the egg weight drmticlly incresed with ge. The eggshell surfce plys n importnt role during the incution period especilly for the reeds which hd comprtively thin nd high porosity shells. The surfce re of egg ffected the porosity of shell nd hence the degree of evportion from the shell. No significnt difference etween strins for eggshell re ws detected. Inversely, the eggshell re ws significntly increses with dvncing ges. The lst results could e ttriuted to the increse egg size s the lyer's ge ws dvncing. The true eggshell re ws significntly ffected y interction etween strin nd reeder flock ge. The effect of ge on true eggshell re ws more pronounced in rown eggs rther thn white eggs, wheres the true eggshell re of rown eggs ws increses with dvncing ge. Similr direction did not oserved in white eggs. Results of pplying eggshell index showed presence highly significnt difference etween strins for eggshell index trit. The rown eggs recorded significntly higher eggshell index compred to the white eggs. Concerning reeder flock ge effect, it could e noticed tht eggshell index ws significntly ffected y reeder flock ge, wheres eggshell index significntly decreses s ge incresed. Eggshell index ws highly significntly ffected y interction etween strin nd reeder flock ge. The pervious result could e ttriuted to the eggshell index incresed with dvncing ge in rown strin. Opposite trend ws noticed in white strin. Mechnicl eggshell trits: Eggshell qulity trits s ffected y strin, lyer reeder flock ge nd their interction re presented in Tle. Specific grvity hs een recommended s n ccurte indictor of shell strength (Well's, 1968). Despite eing n indirect mesure, it correltes well with direct methods ut is non-destructive nd hs the prcticl dvntge of speed nd simplicity. Specific grvity considered s n ccurte predictor of shell thickness, much more relile for this purpose thn percentge shell (Tyler nd Geke, 1961). Our results showed tht rown strin produced eggs ssocited with higher specific grvity compred to white ones. Tht is ment tht rown eggs hd higher eggshell qulity trits compred to white eggs. Concerning reeder flock ge effect, it could e oserved tht the specific grvity decreses with dvncing reeder flock ges. Similr trend ws noticed y Izt et l. (1985) nd Poggenpoel (1986). They demonstrted tht hen ge significntly ffected specific grvity vlues of eggs, where specific grvity decresed significntly with incresing in hen ge. Also, Butcher et l. (1991) reported tht the egg specific grvity decrese s reeder ge ws dvnce. Such phenomen siclly relted to the increment on egg size were 141

4 Tle : Eggshell qulity trits s ffected y strin, reeder flock ge nd their interction (Mens±SE) Breeder flock ge (wk) Pro Trit Strin Overll S A S*A Specific grvity Brown 1.070± ± ± W ± ± ± Overll NS Eggshell (g) Brown 5.03± ± ± W ± ± ± Overll NS Eggshell (%) Brown 10.69± ± ± W ± ± ± Overll NS Shell thickness (mm) Brown 0.35± ± ± W ± ± ± Overll NS Eggshell reking strength Brown 4.79± ± ± Kg/cm W ± ± ± Overll NS NS more quickly thn the shell weight nd lso the increse in egg size reltively higher thn clcium deposition in the eggshell (Curtis et l., 1985). Peeles nd Brke (1987) nd Bennett (199) conformed tht the qulity of eggshells s mesured y specific grvity tends to decline with ge. In view of the fct tht rown eggs hd significntly hevier shell weight compred to the white eggs. With regrd to reeder ge, we cn oserved tht the shell weight incresed with dvncing ge considerly. Shell percentge cn e use to estimte the eggshell qulity (Mertens et l., 006). The present result showed tht the shell percentge ws significntly ffected y reeder strin, wheres the rown eggs were significntly higher shell percentge compred to the white ones. According to Curtis et l. (1986) nd Scott nd Silversides (000) the rown-egg strins produce eggs with greter percentge of eggshell compre to white-egg strin. Likewise, Silversides nd Scott (001) noticed tht the shell, s percentge of egg weight, decresed more for ISA-White eggs with incresing ge of the hen thn it did for ISA-Brown eggs. With respect to reeder ge effect, the shell percentge decreses with dvncing of hen ges. The rown eggs recorded significntly higher shell thickness compred to the white ones. Also, shell thickness ws significntly ffected y reeder flock ge, wheres the shell thickness decreses with dvncing of hen's ges. Such effect ws more pronounced for the rown compred to white reeder strin. Rolnd (1976), Peeles nd Brke (1987) demonstrted tht young hens produce eggs with thicker shells nd longer pores thn older hens i.e. the eggshell generlly thins with ge. Also, Rolnd (1979) reported tht the shell qulity t the end of the ly seson is directly relted to shell qulity t the eginning of ly, the reduction in eggshell thickness s the hen ges een ssocited with n increse in egg size without concurrent increse in clcium cronte deposition. Eggshell strength one of the most importnt egg qulity trits to e considered in poultry reeding progrm is shell strength. Eggshell reking strength of the rown eggs ws higher thn those of white ones, ut the difference did not sttisticlly significnt. On the other hnd, eggshell reking strength ws highly significntly ffected y reeder flock ge, wheres the eggshell reking strength decreses with dvncing of hen's ges. Severl resons hve een presented to explin this chnge in shell strength with ge. It hs een proposed tht the mount of clcium sor, retins nd the skeletl C ville for shell clcifiction decrese with ge. Rolnd et l. (1978) nd Ousterhout (1981) oserved tht egg weight incresed t fster rte thn shell weight resulting in decrese in the mount of shell to cover the egg. In ddition, when stressed with indequte clcium, old hens were le to mintin shell strength s well s young hens, the incresing egg size with progressing ge without concomitnt increse in shell weight s n importnt contriuting fctor to the decresing shell strength with ge. Eggshell ultrstructure properties: Ultrstructurl studies hve demonstrted tht the eggshell is comprised of three morphologiclly distinct clcified lyers. The mmmillry nd plisde lyers comprise t lest 85% of the totl cross-sectionl length of the eggshell (Ruiz et l., 1998). Dt presented in Tle 3 showed tht the effect of strin, reeder flock ge nd their interction on totl, plisde nd cp thickness of eggshell. The present results indicted tht the totl thickness of rown eggshell ws significntly higher thn those of white eggshell. Similr trend ws oserved for plisde thickness (solute nd %), wheres the rown eggshell ws significntly higher solute nd reltive plisde thickness compred to white eggshell. Bin (1991) suggested tht the 14

5 Tle 3: Asolute nd reltive thickness of individul egg lyer s ffected y strin, reeder flock ge nd their interctions (Mens±SE) Breeder flock ge (wk) Pro Trit Strin 5 61 Overll S A S*A Totl thickness (µm) Brown 86.33± ± W ± ± Overll NS Plisde thickness (µm) Brown 3.73± ± W ± ± Overll Cp thickness (µm) Brown 53.60± ± W ± ± Overll Plisde (%) Brown 81.8± ± W ± ± Overll NS 0.05 Cp (%) Brown 18.7± ± W ± ± Overll orgniztion of the plisde columns is mjor Solomon (1999) found good shell ultrstructurl determinnt of shell stiffness nd therefore of shell eneficil high confluence reflects good ttchment with strength. Shell strength is directly relted to shell memrnes nd cps. Concerning fusion trit, thickness (Bin, 1991; Khtkr et l., 1997) nd the significnt differences oserved etween strins plisde lyer comprises pproximtely two-thirds of the regrding fusion (erly or lte). Where, white eggshell eggshell (Prsons, 198). Therefore, it is likely tht hve superior vlue thn rown eggshell (Fig. ). Also, ltertions in the thickness of the plisde lyer, the eggs produced from older reeders hve owned independent of structurl reorgniztion of the plisde fusion vlue higher thn tht of other produced from columns, could ffect shell strength. In contrst, the younger reeders. Thus where fusion is lte, crck rown eggshell ws significntly thinner solute nd propgtion through the shell wll nd therefter reltive cp thickness compred to white eggshell. outwrds from the lod point will occur more rpidly. Therefore, reduction in the cross-sectionl length of Bin (1990) stted tht the decline in frcture toughness these lyers my increse eggshell porosity resulting in cn e explined in terms of n increse in lte fusion excess wter loss during incution. With respect to of djcent mmmillry columns (nd the types of reeder ge effect, it could e noticed tht ll eggshell normlity which ccompny this). lyer were significntly reduced s the ge of reeder No significnt differences etween rown nd white ws dvnced. Incresed erosion of the clcium reserve strin s for type B's structure. Inversely, the Type B's ssemly region of the mmmillry lyer s the reeder trit ws significntly ffected y reeder flock ge, hen ges (Nscimento et l., 199) could potentte where Type B's in eggshell produced from older seprtion of the mmmillry lyer nd shell reeders ws significntly higher thn tht of younger memrnes. hens. Figure 3 showed extensive type B's in rown Solomon (1991) nd Bin (005) descried twelve eggshell t lte ges (61 wk), tht's reduced the structurl vritions in the mmmillry lyer of wek nd eggshell qulity s hrmful figure disjoined djcent poor qulity eggshells. Dt from Tle 4 clrified the columns dhesion. Nscimento et l. (199) stted tht vrious constructions present in the interior surfce of the errnt crystl forms of type B s provide no eggshell fter removing shell memrnes viz it eing in meningful contriution to the plisde lyer nd like the mmmillry lyer which cn ffecting on eggshell poor cp modifictions, which do not offer ny stiffness. Our results showed tht the depression, cuic, nchorge point. In ccordnce to erosion trit, our rgonite, cps nd chnged memrne did not results showed tht the erosion trit vlue of white strin significntly ffected y strin, reeder flock ge nd ws significntly higher thn tht of rown ones. Also, their interction. With respect to confluence trit, the the older reeders produced eggs hve owned higher present results oserved tht oth rown nd white erosion trit thn tht other produced from younger eggs owned shells with similr vlues of confluence. reeders. Figure 1 presented the confluence figures for white Type A's not significntly differed etween strins. strin t erlier ge (5 wk), where white eggs owned However, the type A's ws significntly incresed with good mmmillry cp confluence nd extensive dvncing ge. Figure 4 showed the Type A's of sl confluent cps tht proved good conjunction with shell mmmillry cones in rown eggshell produced from memrnes nd consequently increses eggshell. older hens (61 wk). Type A s ppers to e ssocited 143

6 Tle 4: Ultrstructurl vrints of eggshell mmmille s ffected y strin, reeder flock ge nd their interction Strin Pro Pooled Trit Age (wk) Brown White SEM Overll S A S*A Confluence Overll NS NS Fusion Overll Type B's Overll.73.8 NS 0.01 NS Depression Overll NS NS NS Erosion Overll Cuic Overll NS NS NS Argonite Overll NS NS NS Cps Overll NS NS NS Type A's Overll NS Chnged memrne Overll NS NS NS Cuffing Overll NS Alignment Overll Totl scores Overll.1.93 NS NS Fig. 1: Good confluence nd rounded cps in eggshell of White strin t erly ge (5 wk) Fig. : Lte fusion nd Type A's in eggshell of white strin t lte ge (61 wk) only with the sl cp crystls of the mmmille s crystlliztion etween the cones nd is elieved to e indicted y little or no evidence of contct with the formed t some point fter the mmmillry knos hve memrne fiers (Bin, 1990). There ws significnt egun to fuse (Bin, 1990). Concerning reeder flock difference for cuffing mteril etween strins. Figure 5 ge effect, it could e noticed tht the older hens displyed cuffing form noticed in rown eggshell. This produced eggs were significntly lower in cuffing trit mteril hd useful jo with incresing the cohesion compred to other produced from younger hens. The nd merging the clcified columns, thus increses presented results showed tht lignment comes out to eggshell strength. Cuffing ppers s secondry e significntly differed etween strins, where white 144

7 Fig. 3: Type B's (poorly constructed mmmillry lyer) in eggshell of Brown strin t lte ge (61 wk) Fig. 4: Type A's in eggshell of Brown strin t lte ge (61 wk) Fig. 5: Cuffing (dhesive clcium cronte) mong columns in strong eggshell of rown strin t erly ge (5 wk) Fig. 6: Extensive lignments in Brown strin t lte ge (61 wk) strin hd the higher lignment vlue thn rown ones. Also, the eggs produced from older hens hd higher lignment vlue compred to other produced from younger hens (Fig. 6). Fthi (001) nd El-Sfty (004) reported tht if n egg sujected to mechnicl trum then the crck line will tend to follow the pth of lest resistnce (lignment) nd ordered mmmille provide such pthwy. REFERENCES Al-Btshn, H.A., S.E. Sceideler, B.L. Blck, J.D. Grlich nd K.E. Anderson, Duodenl clcium uptke, femur sh nd eggshell qulity decline with ge nd increse following molt. Poult. Sci., 73: Bdwe, M.I., 006. Modeling of prediction of residul feed consumption in egg-type strins of chicken. M.Sc. Thesis, Fc. of Agric. Ain Shms Univ., Egypt. Bin, M., A reinterprettion of eggshell strength. In: Egg nd Eggshell Qulity, Solomon, S.E. (Ed.). UK, Wolfe Pulishing, 9: Bin, M.M., Eggshell strength: A mechnicl/ ultrstructurl evlution. Ph.D. Thesis, Glsgow Univ., UK. Bin, M.M., 199. Eggshell strength: A reltionship etween the mechnism of filure nd ultrstructure orgniztion of the mmmillry lyer. Br. Poult. Sci., 33: Bin, M.M., 005. Recent dvnces in the ssessment of eggshell qulity nd their future ppliction. World s Poult. Sci. J., 61: Bumgrtner, J., J. Benková nd D. Peškovicová, 007. Effect of line, ge nd individulity on yolk cholesterol content nd some other egg qulity trits in Leghorn type yolk cholesterol selected hens. XVIII Europen Symposium on the qulity of poultry met nd XII Europen Symposium on the qulity of eggs nd egg products, Septemer -5. Prgue, pp: Bell, G., Eggshell qulity-its impct on production, processing nd mrketing economics. In: Biotechnology in the Feed Industry. Proceedings of Alltech s 14th Annul Symposium, pp: Bennett, C.D., 199. The influence of shell thickness on htchility in commercil roiler reeder flocks. J. Applied Poult. Res., 1: Brnd, H.V.D., H.K. Prmeter nd B. Kemp, 004. Effects of housing system cout door vs cges nd ge of lying hens on egg chrcteristics. Br. Poult. Sci., 45: Butcher, G., R. Miles nd A. Nilipour, L clidd del cs cron del huevo. Industri Avicol, 38: Crter, T.C., The hen egg. A mthemticl model with three prmeters. Br. Poult. Sci., 9: Curtis, P.A., F.A. Grdner nd D.B. Mellor, A comprison of selected qulity nd compositionl chrcteristics of rown nd white shell eggs. III. Composition nd nutritionl chrcteristics. Poult. Sci., 65: Curtis, P.A., F.A. Grdner nd D.B. Mellor, A comprison of selected qulity nd compositionl chrcteristics of rown nd white eggshells; I. shell qulity. Poult. Sci., 64:

8 Dennis, J.M., S.Q. Xio, M. Agrwl, D.J. Fink, A.H. Heuer Mchl, L. nd J. Simeonovov, 00. The reltionship nd A.I. Cpln, Microstructure of mtrix nd of shortening nd strength of eggshell to some egg minerl components of eggshells from White qulity indictors nd egg production in hens of Leghorn Chickens (Gllus gllus). J. Morphol., 8: different initil lying lines. Arch. Tierz., 45: Mertens, K., F. Bmelis, B. Kemps, B. Kmers, E. Elroussi, M.A., L.R. Forte, S.L. Eer nd H.V. Biellier, Verhoelst, B. De Ketelere, M. Bin, E. Decuypere Clcium homeostsis the lying hen. 1. Age nd J. De Berdemeker, 006. Monitoring of nd dietry clcium effects. Poult. Sci., 73: 590- eggshell rekge nd eggshell strength in different production of chins of consumption eggs. El-Sfty, S.A., 004. Stepwise regression nlysis for Poult. Sci., 85: ultrstructurl mesurements of eggshell qulity in Monir, K.N., M. Slhuddin nd G. Mih, 003. Effect of two locl reeds of chicken. Egypt. Poult. Sci., 4: reed nd holding period on egg qulity chrcters of chicken. Int. J. Poult. Sci., : Fthi, M.M. nd E.A. El-Shr, Determining the Nscimento, V.P., S. Crnstoun nd S.E. Solomon, strength of eggshell y using n pproprite 199. Reltionship etween shell structure nd pprtus nd n eqution to clculte egg surfce movement of Slmonell enteritidis cross the depending on its dimensions. Egypt. Poult. Sci., 16: eggshell wll. Br. Poult. Sci., 33: Nys, Y., M. Hincke, J.L. Aris, J.M. Grci-Ruiz nd S.E. Fthi, M.M., 001. Ultrstructurl evlution of eggshell Solomon, Avin eggshell minerliztion. qulity produced from two different genetic groups Poult. Avin Biol. Rev., 10: of chicken. Egypt. Poult. Sci., 1: Ousterhout, L.E., The effects of phsed feeding Flock, D.K., Neue Akzente für die protein nd clcium on egg weight nd shell qulity Legehennenzucht: rückläufige Leistungs- with four strins of white leghorn hens. Poult. Sci., steigerungen zwingen zum Üerdenken der 60: Zuchtziele. Arch. Tierz., 38: Prsons, A.H., 198. Structure of the eggshell. Poult. Frser, A.C., M.M. Bin nd S.E. Solomon, Sci., 61: Trnsmission electron microscopy of the verticl Peeles, E.D. nd J. Brke, Eggshell qulity nd crystl lyer nd cuticle of the eggshell of the htchility in roiler reeders eggs. Poult. Sci., 66: domestic fowl. Br. Poult. Sci., 40: Gunlu, A., K. Kiriki, O. Cetin nd M. Crip, 003. Some Poggenpoel, D.G., Correlted response in shell externl nd internl qulity chrcteristics of nd lumen qulity with selection for increse egg ptridge (A. grec) eggs. Food Agri. Environ., 1: production. Poult. Sci., 65: Potts, P.L. nd K.W. Wshurn, The reltionship Hmilton, R.M.G., Oservtions on the chnges in of ge, methods of mesuring nd strin on physicl chrcteristics tht influence eggshell vrition in shell strength. Poult. Sci., 6: qulity in ten strins of white leghorns. Poult. Sci., Roerts, J.R., 004. Fctors ffecting egg internl qulity 57: nd eggshell qulity in lying hens. J. Poult. Sci., 41: Hempe, J.M., R.C. Luxen nd J.E. Svge, Rpid determintion of egg weight nd specific grvity Roerts, J.R. nd C.N. Blney, 000. Eggshell using computerized dt collection system. Poult. ultrstructure nd shell qulity. Reltionship of Sci., 67: ultrstructure to eggshell qulity nd strength. Izt, A.L., F.A. Grdner nd D.B. Mellor, The effect World s Poult. Sci. Rev. Conference Montrel of ge of ird nd seson of the yer on egg qulity. Cnd. II. Hugh units nd compositionl ttriutes. Poult. Rolnd, D.A. Sr., Recent developments in Sci., 65: eggshell qulity. Feedstuffs, 48: 31-3, 41. Khtkr, M.S., J.S. Sndhu, G.S. Brh nd M.L. Rolnd, D.A. Sr., Fctors influencing shell qulity Chudhry, Estimtion of egg shell reking of ging hens. Poult. Sci., 58: strength from egg chrcteristics in lyer chickens. Rolnd, D.A. Sr., C.E. Putmn nd R.L. Hilurn, In. J. Poult. Sci., 3: The reltionship of ge on ility of hens to Krshvrz, K., Lying hens respond differently to mintin eggshell clcifiction when stressed with high dietry levels of phosphorus in monosic nd indequte dietry clcium. Poult. Sci., 57: disic clcium phosphte. Poult. Sci., 73: Lukáš Zit, N., E. Tùmová nd L. Štolc, 008. Effects of Ruiz, J., P. Groves, P. Gltz, J. Meldrum nd C. Lunm, Genotype, Age nd Their Interction on Egg Qulity Ultrstructurl nlysis of eggshell lmine. in Brown-Egg Lying Hens. Act Vet. Brno., 78: 85- Proceedings of the Austrlin Poultry Science 91. Symposium, Sydney, pp:

9 SAS institute, 000. SAS/STAT User's Guide sttistics Ver. 8.; SAS institute Inc., Cry, NC. Suveur, B., Reproduction des volilles et production d'ufs (Pris, INRA Editions). Scott, T.A. nd F.G. Silversides, 000. The effect of storge nd strin of hen on egg qulity. Poult. Sci., 79: Seelnd, G., R. Huner nd B. Roder, Beziehungen zwischen der Legeleistung und Eiqulitätsmerkmlen von Legehennen. Arch. Tierz., 38: Silversides, F.G. nd T.A. Scott, 001. Effect of storge nd lyer ge on qulity of eggs from two lines of hens. Poult. Sci., 80: Solomon, S.E., Egg nd eggshell qulity, Wolfe Pu. Ltd. London. Solomon, S.E., An eggs ist ein ei, es un huevo, est un oeuf. Br. Poult. Sci., 40: Summers, J.D. nd S. Leeson, Fctors influencing erly egg size. Poult. Sci., 6: Tyler, G. nd F.H. Geke, Studies on eggshells. XV. Criticl pprisl of vrious methods of ssessing shell thickness. J. Sci. Food Agric., 1: Wshurn, K.W., Genetic Vrition in Egg Composition. In: Poultry Breeding nd Genetics, Crwford, R.D. (Ed.). Elsevier Scientific Pulishers, New York, pp: Well's, R.J., The mesurement of certin egg qulity: A study of the hens. Ed. y T.C. Crter Pu. Oliver nd Boyd Edinurgh, pp: 0-6,