European Poultry Science (EPS)

Europ.Poult.Sci., 79. 2015, ISSN 1612-9199, © Verlag Eugen Ulmer, Stuttgart. DOI: 10.1399/eps.2015.76


The effect of milling method, thermal treatment, and particle size of feed on exterior and interior egg quality in laying hens Der Einfluss von Mahlmethode, Hitzebehandlung und Partikelgröße von Futter auf die innere und äußere Eierqualität bei Legehennen A. Hafeez, Anneluise Mader, Ilen Röhe, Isabelle Ruhnke, F. Goodarzi Boroojeni, M. S. Yousaf, K. Männer and J. Zentek

Institute of Animal Nutrition, Department of Veterinary Medicine, Freie Universität Berlin, Germany

Correspondence: [email protected] Manuscript received 23 September 2014, accepted 10 January 2015

Introduction Milling method, thermal treatment, and particle size are important variables determining feed production costs, feed intake

and digestibility and potentially egg quality in laying hens. Besides the raw material, the energy needed during production has a major impact on the total feed costs and energy saving milling methods such as the roller mill are becoming more used

in the feed industry. Diminution of feed is the largest energy cost in layer feed production (DEATON et al., 1989) and the second largest after pelleting in broiler feed production (REECE et al., 1985). Hammer mills and roller mills are commonly

used to reduce particle size of grains (AMERAH et al., 2007; KOCH, 2002). The hammer mill is easier to handle and to maintain, but requires more energy than the roller mill (AMERAH et al., 2007). The hammer mill produces more spherical and uniform shaped particles (REECE et al., 1985), whereas the roller mill generates a more uniform particle size (AMERAH et al.,

2007) with irregular cubic or rectangular shape (KOCH, 2002). In addition, hammer mills produce a greater amount of fine particles (REECE et al., 1985). Due to the fact that chickens have a preference for larger feed particles (SCHIFFMAN, 1968), the

particle size distribution may affect egg quality, as nutrients may not be equally ingested or effectively utilized (TANG et al., 2006). In contrast, the comparison between corn based diets milled with hammer or roller mills showed no effects on bird performance and egg shell breaking strength (DEATON et al., 1989). Interestingly, layers fed with a barley based diet ground by roller mill had higher egg weight compared to the same diet produced by a hammer mill (HAMILTON, 1994). Layers fed a barley based diet ground by roller mill reduced feed intake and egg production as compared to maize and wheat diets, while

no differences were observed when a hammer mill was used. Egg quality was not affected by milling methods (PÉREZ-BONILLA et al., 2014).

Thermal treatment is commonly used in feed production to enhance apparent ileal digestibility of nutrients, to improve hygiene status of feed, and for the reduction of antinutritional factors (KILBURN and EDWARDS, 2001; MOSSEL et al., 1967;

PEISKER, 2006). Leghorn hens receiving a barley based diet flame-roasted at 124°C had eggs with higher Haugh unit scores than hens fed with non-roasted diets (HAMILTON, 1994). On the other hand, a previous study showed that thermal treatment of feed did not affect egg quality parameters including weight, Haugh unit and blood spot (HAMILTON and PROUDFOOT, 1995), while other egg quality variables of economic importance were not considered. The reduction in feed particle size increases the surface area for enzymatic activity, modifies the physical characteristics of feed and may result in improved animal performance (GOODBAND et al., 2002; WALDROUP, 1997). However, the coarser grinding of grains to a more uniform particle size may improve feed intake (SAFAA et al., 2009), performance of mature birds due to more gizzard development leading to increased grinding, gut motility and nutrient digestion (AMERAH et al., 2007). The effect of milling method, thermal treatment and particle size on egg quality has not been widely studied. Therefore, the aim of the present study was to investigate the impact of milling methods including roller and hammer mills, thermal treatment expansion, and their interaction with fine and coarse particle size of feed on exterior and interior egg quality parameters in laying hens.

Material and Methods The animal trial was performed according to the Animal Welfare Act of Germany approved by the local state office of occupational health and technical safety (Landesamt für Gesundheit und Soziales, LaGeSo, no. G 0117/11).

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Hens and experimental design The experiment lasted for 28 days including first week of adaptation period. Two hundred and forty hens (Lohmann Brown) at the age of 19 weeks were used. The hens were divided into 8 experimental groups in 5 replicates with 6 hens per pen (in total 30 hens per feeding group). The hens were obtained from a commercial pullet rearing farm where they were previously fed with mash feed produced with a hammer mill. Hens were kept in cages, which consisted of an area for claw abrasion, a

perch, and laying nests. Wood shaving was used as bedding material. The light was provided for 16 hours a day. Eight experimental diets, produced from one identical basal diet (Table 1), meeting the nutritional recommendations by German

Society of Nutritional Physiology (GFE, 1999), were offered ad libitum during the whole experimental period and one week

before for diet adaption. The experiment was conducted using randomized design with a 3 factorial arrangement. Experimental diets were formulated using roller mill (R) and hammer mill (H) as mash (M) and expandate (E) with coarse (C)

and fine (F) particle size. The 8 different diets formulated using a 2 × 2 × 2 arrangement were then assigned to hens as 8

groups with 5 replicates each.

Table 1. Feed composition and nutrient content of the basal experimental diet Zusammensetzung und Nährstoffgehalte der Basisversuchsration Ingredients Corn Wheat

g/kg as fed 301 291

Soybean meal (42% CP) Calcium carbonate Soya oil Molasses

225 86.0 44.6 30.0

Mineral/Vitamin premix1

12.0

Monocalcium phosphate Salt DL-Methionine L-Tryptophane Titanium dioxide

7.8 2.0 1.0 0.2 0.2

Nutrient content Dry matter Crude protein Ether extract Crude fiber Starch Crude ash Calcium Phosphorus Calculated ME (MJ/kg)

g/kg dry matter as analyzed 882 186 59.7 32.7 419 111 35.7 3.54 11.4

ME metabolizable energy 1 Mineral and Vitamin Premix (Spezialfutter Neuruppin, Neuruppin, Germany) containing per kg premix: 400000 IU vitamin A; 40000 IU vitamin D3; 8000 mg vitamin E (alpha-tocopherole acetate); 300 mg vitamin K3; 250 mg vitamin B1; 250 mg vitamin B2; 2500 mg nicotinic acid; 400 mg vitamin B6; 2000 μg vitamin B12; 25000 μg biotin; 1000 mg calcium pantothenate; 100 mg folic acid; 80000 mg choline chloride; 5000 mg zinc (zinc oxide); 2000 mg iron (iron carbonate); 6000 mg manganese (manganese oxide); 1200 mg copper (copper sulfate-pentahydrate); 45 mg iodine (calcium iodate); 30 mg cobalt (cobalt-(II)-sulfate-heptahydrate); 35 mg selenium (sodium selenite); 35 g sodium (sodium chloride); 55 g magnesium (magnesium oxide).

Experimental diets production The experimental diets were processed as described by RÖHE et al. (2014). In brief, two milling types, including a roller mill (Vario-Walzenstuhl, MIAG AG, Bühler GmbH, Braunschweig, Germany) and hammer mill (horizontal rotor hammer mill, Tietjen, Hemdingen, Germany), were used to obtain coarse and fine diets. Defined particle sizes were achieved by using various milling speeds and matrix plates. Coarse feed was defined as feed characterized by discrete mean particle size (dMEAN) above 1.8 mm, while fine diets were characterized by dMEAN below 1.8 mm, based on dry sieving analysis (WOLF et al., 2012). All variants were provided to the hens as expandate (Single Screw Expander OE8, Amandus Kahl GmbH & Co KG, Reinbek, Germany) or mash (Table 2).

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Table 2. Discrete mean particle size (dMEAN) of the eight experimental diets produced by different milling methods, particle sizes and thermal treatment Diskrete, durchschnittliche Partikelgröße (dMEAN) der acht Versuchsrationen, die mit verschiedenen Mahlverfahren, Siebgrößen und thermischen Behandlungen hergestellt wurden Roller

Mill Particle size

Hammer

Coarse

Thermal

Fine

Coarse

Fine

Mash

Expandate

Mash

Expandate

Mash

Expandate

Mash

Expandate

dMEAN after dry sieving analysis (mm)

1.93

2.43

1.28

1.27

2.41

2.15

1.64

1.30

dMEAN after wet sieving analysis (mm)

1.85

0.85

1.14

0.31

2.60

0.93

1.27

0.50

Wet sieving analysis of diets The wet sieving analysis of the experimental diets was performed as described by RÖHE et al. (2014). In brief, a total of 100 g

feed sample was soaked in 1000 mL water for 60 minutes and sieved through nine sieves with different pore sizes (Analysensiebe, Retsch GmbH, Haan, Germany) for 10 minutes under continuous shaking. The contents of the sieves were dried for 6 hours at 100°C before weighing and dMEAN was calculated as described earlier (FRITZ et al., 2012). Results are displayed in Table 2.

Data for performance parameters Throughout the experimental period, data were collected for performance parameters including laying performance, feed intake, FCR and body weight etc. and nutrients digestibility, which is explained in RUHNKE et al. (2015).

Collection of samples At the end of experiment, at 23 weeks of age, three eggs per pen from every diet group (in total 15 eggs per group) were randomly collected for exterior and interior quality analysis.

Determination of egg quality Eggs with any visible cracks were sorted out. After weighing (g) the egg, the air cell (mm) was measured using a candling lamp (Powerlux, Egg Tester, Orka Technology, UT, USA) and air cell gauge (Luftkammer-Messer, Siepmann GmbH,

Herdecke, Germany). Shape index was measured with the help of self-built device (Humboldt Universität, Berlin, Germany). Egg stability or shell breaking strength was determined using the measure and test system Typ EPG (Mess- und Prüfsysteme GmbH, Wazau, Berlin, Germany). The number of visible blood and meat spots was counted. Yolk color was determined using a Roche Yolk Color Fan (RYCF, F. Hoffman-La Roche AG., Basel, Switzerland) where 1 was lightest and 15 was darkest color. The height (mm) of yolk and albumen was measured using a device from August Fabia (München, Germany). The length and width (cm) for yolk and albumen was determined with a vernier caliper. The shell thickness (mm) was measured at center, broad and pointed ends using a shell thickness meter (Ogawa Seiki Co., Tokyo, Japan). The weight (g) of shell, shell membrane and yolk was measured using balance (1205 MP, Sartorius AG, Göttingen, Germany). The weight (g) of albumen was determined after subtracting the weight of yolk, shell and shell membrane from total egg weight (g). Yolk index was calculated as a ratio between yolk height and width. Albumen index was estimated from the ratio of albumen height to width. The percent content of yolk, albumen, shell and shell membrane was determined according to their respective weight (g) in relation to total egg weight (g). 2

Area (cm ) vs egg weight was calculated by this equation: 0.662

A = 4.835 × W

(PAGANELLI et al., 1974), where W = Egg weight (g)

Shell weight per unit surface area (SWUSA) was calculated by following expression: SWUSA = 3.9782 × (EW)

0.666

(CARTER, 1975), where EW = Egg weight (g) 2

The SWUSA was expressed as mg/cm (TYLER and GEAKE, 1964). Surface area (SA) was determined from this expression: 0.7056

SA = 3.9782 × (W

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) (PHIRINYANE et al., 2011), where W = Egg weight (g)

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Shell density was estimated from the expression: 5

SD = SW/(SW × ST) (DUDUSOLA, 2009), where ST = Shell Thickness (mm) Haugh unit was calculated using following formula: 0.37 2

HU = 100log (H + 7.51 – 1.7EW

) (DUDUSOLA, 2009; HAUGH, 1937), where H = Albumen height (mm), W = the weight of

egg when tested (g). The ranking for Haugh unit was as following: AA = 72–130, A = 60–71, B = 31–59, C 0.05). The performance parameters are briefly discussed by RUHNKE et al. (2015) and were not affected by the feed production methods.

The results after dry and wet sieving analysis of particle size are presented in Table 2. The thermal treatment had a major

effect on particle size analysed after wet sieving. The expansion resulted in a less pronounced differences between coarse and fine particle size after wet sieving. Table 3 presents the effect of milling method, thermal treatment and feed particle size on exterior egg quality. The shell membrane weight and percent shell membrane weight was lower in treatment H as compared to treatment R (P 0.05).

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1,2

Table 4. Effect of milling method, thermal treatment and particle size of feed on interior egg quality in layers

Einfluss des Mahlverfahren, der thermischen Behandlung und der Partikelgröße des Futters auf die Merkmale der internen Eiqualität der Legehennen Mill

Thermal

P-value

Particle Size

Mill× Roller Hammer Air cell Yolk color Blood spot Haugh unit

Mash Expandate

Coarse Fine

SEM

1.38 1.40 5.20 4.88 0.733 0.595 97.2 93.4

0.069 0.113 0.084 1.042

0.523 0.524 0.414 0.601

Mill Thermal Size Thermal Size

(mm) 1.43 1–15 4.97 0.733 94.8

1.34 5.11 0.595 95.9

1.45 5.13 0.669 95.4

1.33 4.95 0.660 95.3

5.00a

4.92

4.94

4.94

4.92

0.026

0.006

0.704

Yolk weight

(g)

4.86b 12.4

12.4

12.5

12.4

12.5

12.3

0.092

0.949

0.808

Yolk height

(mm) 18.4b (cm) 3.85 (cm) 3.80

18.8a 3.76 3.76

18.6

18.6

18.7

18.5

0.080

0.018

0.786

3.79 3.78

3.82 3.79

3.84 3.81

3.77 3.76

0.032 0.015

0.155 0.203

147

148

148

147

151

144

2.427

36.8

36.6

36.9

36.5

37.2

36.2

(mm) 9.48

9.57

9.53

9.52

9.79a

6.43

6.50

6.50

6.43

7.84

7.78

7.75

2.97

2.96

22.5

22.6

66.1

66.1

66.2

Yolk index

Yolk width Yolk length Albumen index Albumen weight Albumen height

(g)

Albumen (cm) width Albumen (cm) length Albumen:Yolk % Yolk weight % Albumen weight 1 2

Mill× Thermal

0.395 0.419 0.955 0.954

0.849 0.150 0.414 0.073

Mill×

×Size

Thermal×Size

0.650 0.044 0.463 0.748

0.829 0.203 0.260 0.543

0.278 0.215 0.463 0.811

0.449 0.602 0.047 0.772

0.713

0.276

0.546

0.503

0.892

0.297

0.689

0.157

0.067

0.579

0.301

0.292

0.036

0.093

0.753

0.622 0.691

0.248 0.103

0.312 0.994

0.856 0.973

0.200 0.499

0.516 0.694

0.709

0.916

0.161

0.931

0.377

0.952

0.816

0.325

0.812

0.535

0.111

0.978

0.766

0.219

0.123

9.27b

0.120

0.698

0.975

0.032

0.701

0.759

0.470

0.405

6.44

6.49

0.041

0.394

0.392

0.539

0.743

0.663

0.535

0.855

7.88

7.77

7.86

0.055

0.603

0.264

0.395

0.296

0.039

0.986

0.398

2.97

2.96

2.98

2.95

0.029

0.903

0.771

0.576

0.826

0.449

0.827

0.093

22.4

22.6

22.4

22.6

0.161

0.751

0.703

0.498

0.881

0.374

0.556

0.115

66.0

66.1

66.1

0.194

0.902

0.562

0.890

0.926

0.997

0.897

0.050

Data are means of 15 replicates per group. Data within one group were normally distributed.

Discussion The results demonstrated that mash feed did not show pronounced differences in particle size distribution after dry and wet sieving analysis. Therefore, the characterization of coarse and fine particle size in mash diet may be based on macrostructure

of the feed obtained from dry sieving analysis. This macrostructure of the particles is reduced to microstructure due to digestive juices and saliva activity in the upper digestive tract of the bird. The results obtained by dissolving feed in water and subjecting it to wet sieving analysis represent the microstructure of the diet which is similar to particle size in the digestive tract of the bird. Our results indicated that differences between coarse and fine particles in thermally processed feed after wet sieving analysis were less pronounced in comparison with dry sieving analysis. The macrostructure may influence feed intake by the bird whereas microstructure affect the gut function therefore, feed subjected to thermal treatment may be characterized by both, macro- and microstructure (SVIHUS, 2006). A well-developed gizzard significantly reduces the feed particle size (AMERAH et al., 2007; DUKE, 1986; NIR et al., 2001; NIR et al., 1994). The literature shows a strong relation between development of gizzard and feed particle sizes (AMERAH et al., 2007; CUMMING, 1994; ENGBERG et al., 2002; NIR et al., 1995; TAYLOR and JONES, 2004; WILLIAMS et al., 2008). In the present study, we had similar findings where gizzard weight was significantly higher in birds fed with coarse feed particles than those receiving fine particles, which is briefly discussed in another publication by RÖHE et al. (2014). In the present study, shell membrane weight and percent shell membrane weight was higher in the treatments receiving feed produced by the roller mill as compared to the hammer mill. The shell membrane is normally counted as part of egg shell. The shell membrane is synthesized by proteinaceous fibers in isthmus, whereas the egg shell is formed of calcium carbonate which is deposited around the shell membranes in the uterus. Minerals like sodium, potassium and bicarbonates are transferred through shell membrane and it acts like a barrier between egg shell and internal egg contents including albumen and yolk (LARBIER and LECLERCQ, 1992). Therefore, the shell membrane may have a role in the crystallization of calcium

carbonate for egg formation. In present study, calcium deposition in egg contents including shell was not affected by milling methods, which is briefly discussed in HAFEEZ et al. (2015). Due to the fact that egg stability and shell weight were not affected by milling methods, the differences in the shell membrane are minor and may not have any biological

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consequences. The feed produced by hammer mill resulted in a higher yolk height in comparison with roller mill, whereas

the other interior quality variables were not affected. The higher yolk index is the indication of freshness of egg which reduces with time due to deterioration of the vitelline membrane and liquefaction of the yolk (CANER, 2005). The development of the yolk (Vitellus) is rapid during 8 to 10 days before lay when diverse protein and lipoproteins synthesized in the liver including phosvitin, lipovitellin and lipovitellenin are intensively transported to developing yolk (LARBIER and

LECLERCQ, 1992). The vitelline membrane around the yolk interferes with transport of water and minerals from albumen which increases with time after lay and flattens the shape of the yolk thereby reducing its height (LEESON and SUMMERS,

2001). Due to the fact that apparent ileal digestibility of crude protein and amino acid levels were not affected by milling methods in the present study as reported in RUHNKE et al. (2015), which could have influenced the yolk formation, the higher yolk height and yolk index seems to have no systematic background and was probably caused by chance. Our results are in line with a previous study which suggests that shell breaking strength of eggs from laying hens fed with diets produced by

roller and hammer mills was comparable (DEATON et al., 1989). Another recent study shows similar results where Hy-Line Brown laying hens fed with diets ground by roller and hammer mill had no effect on Haugh unit, yolk color, percent content of shell, yolk and albumen in egg, and yolk to albumen ratio (PÉREZ-BONILLA et al., 2014). In contrary, leghorn hens given a

barley diet produced by roller mill had higher number of large size eggs and blood spots, increased egg weight, and a lower number of medium sized eggs as compared to hens fed with hammer milled diet (HAMILTON, 1994). Thermal treatment of feed may improve starch digestibility and extract viscosity (LUNDBLAD et al., 2011), as well as apparent

ileal nutrient digestibility (JIA and SLOMINSKI, 2010; KILBURN and EDWARDS, 2001). The results of the present study as

described by RUHNKE et al. (2015) indicate that starch digestibility was higher in hens fed with mash feed as compared to hens

receiving expandate, however digestibility of protein and amino acids was not affected by thermal treatment. The present study demonstrates that the shell membrane content was higher in expansion treatment. Due to the fact that other related parameters to shell membrane including shell weight and stability were not affected by expansion of feed, the difference in percent shell membrane weight has no major impact on egg quality. The literature reveals similar findings where white

leghorn laying hens fed with mash, crumbles and pellets did not show any differences in egg weight, Haugh unit and blood spots (HAMILTON and PROUDFOOT, 1995). On the other hand, laying hens given crumbled diets had higher egg size compared to hens fed mash diets (PEPPER et al., 1968). Furthermore, layers receiving a flame-roasted barley diet (124°C) had lower egg weight, number of extra large size eggs and higher Haugh unit score, number of medium sized, and grades B and C eggs than non-roasted barley diets (HAMILTON, 1994). Our results show that shell density was higher in treatment receiving fine sized particle whereas shell thickness and shell weight was higher in treatments receiving coarse sized particles. Furthermore, albumen height was higher in treatments receiving coarse particles as compared to those with fine particles. However, these changes observed in shell density, shell

thickness and shell weight did not affect the stability of the egg shell and percent shell weight, therefore this impact of particle size is of minor importance. Similarly higher albumen height in treatment receiving coarse particles did not affect the Haugh unit score which depends on albumen height at most. Therefore, the differences in albumen height due to particle size are of lower value. Our findings are in line with a previous study, which indicated that fine and coarse feed particle did not alter egg weight, Haugh unit and blood spots in laying hens at 187 and 477 days of age (HAMILTON and PROUDFOOT, 1995). Similarly, increasing particle size in a corn based diet had no impact on the shell breaking strength (DEATON et al., 1989). Moreover, the feed particle size did not affect the egg weight, Haugh unit, air cell, blood spot and percent egg contents of shell, yolk and albumen in laying hens (SAFAA et al., 2009). In contrast, another study revealed that due to feed

segregation and selection of large feed particles by the birds, the shell thickness, albumen height and Haugh unit were negatively affected, as small particle nutrients may not have been utilized (TANG et al., 2006).

The interaction between treatments affected some external and internal egg quality parameters in present study. The yolk height was higher in groups receiving coarse particles produced by hammer mill than coarse particles produced by roller mill whereas no differences were observed for fine particles produced by both roller and hammer mills. This might indicate that spherical shaped particles produced by the hammer mill resulted in higher yolk height than same sized irregular shaped particles produced by roller mill, which might be due to better nutrient absorption and utilization especially for proteins. However, the digestibility data for this study reported by RUHNKE et al. (2015) indicates that nutrient digestibility was not

affected by interaction of milling methods and particle size. Additionally, the shell thickness was lower in groups receiving fine particles produced by roller mill in comparison with all other interaction groups. However, these differences did not affect shell weight, stability and density. Therefore, the differences observed for yolk height and shell thickness for interaction effects between milling method and particle size seem to have no physiological background. In general, in the present study, all eggs were classified as AA quality on the basis of Haugh unit score (> 72). This reflects that feed treatments had no deleterious impact on egg quality. According to recommendations of the Council of the European Union, only eggs graded at least class A can be sold or retailed (COMMUNITY, 2006). However, the feed production

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costs have to be taken into account while formulating layer ration with any combination of the treatments used in present study.

Conclusions In conclusion, milling methods, expansion and particle size of feed, and their interactions had no effect on egg quality

parameters of economic importance and laying performance. Therefore, feed production technology can be modified according to specific requirements, eg. energy saving, hygienisation, and animal welfare without negatively affecting egg quality.

Acknowledgements The project was financed by the German Federation of Industrial Research Association (Allianz Industrie Forschung- AIF) through the German Federal Ministry of Economics and Technology, project number 16800 N. The authors are especially thankful to A. Kannegießer, I. Walther and M. Modrow from Institut für Agrar- und Gartenbauwissenschaften, Humboldt-

Universität zu Berlin, for their technical support during the laboratory analysis. The authors express deep appreciation to Dr. W. Vahjen from the Institute of Animal Nutrition, Freie Universität Berlin for his valuable inputs and critical review of the manuscript.

Summary Various milling methods, thermal treatment and particle sizes are used in feed production for laying hens, which may influence egg quality. The present study was designed to investigate the effect of feed produced by roller (R) and hammer mill (H) as mash (M) and expandate (E) with coarse (C) and fine (F) particle size on exterior and interior egg quality in layers. A total of 240 hens (Lohmann Brown), 19 weeks old, were used in a randomized design with 2×2×2 factorial arrangement. Eight experimental diets were offered ad libitum during the whole experimental period and one week before for diet

adaption. Eggs were analyzed for egg weight, area, shape index, shell weight per unit surface area, air cell, yolk color, blood spot, Haugh unit, yolk and albumen measures (weight, index, height, width and length) shell measures (stability, surface area, density, thickness and membrane weight), and percent contents of yolk, albumen, shell and shell membrane. The shell membrane weight and percent shell membrane weight was lower in treatment H as compared to treatment R (P