Parental diet effects on egg component weights and shell quality

 C 2016 Poultry Science Association Inc.

Parental diet effects on egg component weights and shell quality Z. S. Lowman1 and C. M. Ashwell Prestage Department of Poultry Science, North Carolina State University, Raleigh, 27606 Primary Audience: Researchers, Layer Companies, Layer Producers

An experiment was conducted to investigate the effects of feeding laying hens a low protein and energy diet (LPE), a high protein and energy diet (HPE), and a commercial protein and energy diet (control) on whole egg components, egg weight, and shell quality. The hens were fed their respective diets from 15 to 30 wk of age. At 30 wk of age, egg component weight and percentages were measured along with eggshell quality. The results demonstrated that birds fed the LPE diet had significantly lower albumen, yolk, and total egg weights that the control and HPE groups. The LPE group had significantly lower levels of total albumen protein than the control group. The HPE hens had significantly lower shell thickness and pore concentration than the LPE group, demonstrating that dietary levels of CP and ME can alter not only shell quality component but also albumen protein levels. Key words: Egg components, protein, energy 2016 J. Appl. Poult. Res. 0:1–6 http://dx.doi.org/10.3382/japr/pfw024

DESCRIPTION OF PROBLEM One of the largest costs associated with commercial poultry production is feed. In fact, it has been estimated that 65 to 75% of the cost associated with egg production comes from feed costs [1]. Protein and energy are the 2 most costly components of poultry feeds, and make up about 85% of the total feed cost [2]. As a result of the high cost of feeding poultry, many studies have been conducted exploring how to maximize the performance of the birds, while minimizing input costs. This feat can be challenging since changes in protein and energy levels in the diets of laying hens have been shown to change egg production, [3,4] egg size, [5, 6] and yolk weight [6]. In fact, Zimmerman [5] has proposed a method to manage egg size by precise delivery of amino acids that has no impact on the production of the hen. 1

Corresponding Author: [email protected]

Egg weights have been shown to vary depending on crude protein (CP) and energy (E) available in the diets. Shim et al. [6] reported that hens fed higher protein diets have larger egg weights when compared to eggs from hens on lower CP diets. Gunawardana et al. [2] reported increasing dietary protein intake from 13.8 to 17.1 g/hen per day resulted in a 2.38 g increase in egg weight, but changing dietary energy was found to have no effect in this trial. Similar results also were reported by Sohail et al. [7] and Shim et al. [6] in that hens on higher protein diets produced eggs with significantly larger weights. However, data exists that demonstrated egg weight was not affected by feeding low CP diets [3]. The majority of the research suggests that birds fed diets containing low CP produce eggs that weigh less than birds fed higher CP diets. Leeson and Caston [8] demonstrated that birds fed 14.4% CP had lower egg weights than birds fed 16.8% CP diets.

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SUMMARY

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MATERIALS AND METHODS The experimental procedure used in this investigation was approved by the North Carolina State University Animal Care and Use Committee. Three hundred and sixty one-day-old W-36 parent stock chicks were obtained from a Hyline International hatchery [18]. Each chick was neck tagged and sorted into one of 3 dietary treat-

ments (20 chicks per pen, 120 chicks per treatment): low protein and energy diet (LPE [low CP and ME]), control (normal CP and ME), and high protein and energy diet (HPE [high CP and ME]). All chicks were raised in the same room in Petersime brooders. The chicks were brooded under standard brooding conditions, 30◦ C for the first wk, 28◦ C for the second wk, 26◦ C for the third wk, and 24◦ C for the remainder of the trial. The low group was fed a starter feed containing 12% CP and 2204.6 kcal/kg ME, the control group was fed a diet that contained 18% CP and 2998.3 kcal/kg ME, and the HPE diet contained 24% CP and 3218.8 kcal/kg ME (Table 1). The birds were moved at 4 wk of age to grow-out batteries (10 birds per pen). The birds were kept in the grow-out batteries for 11 wk. All birds were switched to the corresponding layer diet (Table 2.) when they reached 15 wk of age. The layer diets had the same CP and ME levels as the starter diets; the main difference was the increase in calcium levels for egg production. The birds were allowed ad libitum access to feed and water for the entire trial. When the birds were 15 wk old they were then moved to layer cages (2 birds per pen). When the hens were 30 wk old, 25 fresh eggs per treatment were collected and weighed, and egg contents were measured on the same d; whole egg weight, albumen weight, yolk weight, pore count, and shell thickness were recorded. All experimental data collected during the trial were analyzed by ANOVA using JMP 10 [20] with Tukey-Kramer comparison of means; an alpha of 0.05 was used to establish significances. Egg Contents The total egg weight was determined, and then, following the procedures of Gunawardana et al. [2], each egg was gently cracked open and the yolk placed on filter paper and gently rolled around and dried. Albumen weight was calculated by subtracting yolk and shell weight from total egg weight. The shells were rinsed with tap water leaving membranes intact and allowed to dry overnight. The shell thickness was measured using a manual caliper [19] to the nearest .01 mm, in triplicate in a similar location around the large end of each egg. Egg pore staining was conducted using the methods of Peebles and

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Shim et al. [6] states that yolk percentage is indirectly proportional to CP in young hens. Hens exposed to increasing dietary protein demonstrated a significant increase in yolk weight when compared to the controls. Gunawardana et al. [2] reported significant increases in both yolk and albumen weights in the birds on the high CP diets in comparison with birds on low CP diets. Eggs possess a unique property that allows for gas exchange through microscopic openings or pores. Eggs must allow for the exchange of gases produced and required by the developing embryo, as well as exchange of moisture so that the embryo can maintain ideal conditions [9, 10, 11]. This diffusion of gas has been termed conductance and is a measure of the gas exchange of an egg [9]. There are several factors that affect conductance including pore concentration. There has been much research focused on eggshell pore concentration associated with the age of the female, [9, 12, 13] and genetics or strain of the bird [10]; however, there has been very little research looking at nutritional effects on pore number. It is well documented that as poultry progress through their laying cycle the thickness of their eggshells decreases as the size of their eggs increases. As a result the pore concentration decreases [9, 12, 14]. This change in pore concentration has drastic effects on conductance and ultimately the hatchability of the eggs [9]. Since changes in diet have been shown to cause significant changes in egg weights, research looking at the effect this has on pore concentration is justified. There has been much research examining the effect that diets have on the yolk contents from color to lipid modification [15, 16, 17]. Yet there has been no research to date examining the effect that dietary protein levels have on the protein content of the albumen.

LOWMAN AND ASHWELL: EGG COMPONENTS

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Table 1. Ingredient composition of starter diets. Low %

High %

Yellow Corn Oats Poultry fat Poultry by-product meal Soybean meal Soybean hulls Calcium carbonate Dicalcium phosphate Salt DL-Methionine Choline Trace mineral mix1 Vitamin pre-mix2 Selinium Amprolium

50.0 12.5 4.2 8.2 12.5 9.6 0.9 1.3 0.3 0.1 0 0.2 0.1 0.1 0.1

30.3 35.0 0 0 4.2 26.6 0.9 2.0 0.3 0.3 0.1 0.2 0.1 0.1 0.1

55.4 1.3 4.1 12.5 23.4 0.9 1.0 0.7 0.3 0.1 0 0.2 0.1 0.1 0.1

Formulated percentages Crude protein Crude fat Crude fiber Calcium Metabolizable energy

Control (%) 18.00 8.00 6.30 1.00 2998.3 kcal/kg

Low (%) 12.00 3.30 14.23 1.00 2204.6 kcal/kg

High (%) 24.00 8.00 2.36 1.00 3218.8 kcal/kg

1

The trace mineral mix contained the following per kg of diet: Manganese, 120 mg; zinc, 120 mg; iron, 80 mg; copper, 10 mg; iodine, 2.5 mg; and cobalt, 1.0 mg. 2 The vitamin premix contained the following concentrations per kg of feed: Vitamin A, 13,200 IU; cholecaleciferol, 4,00 IU; vitamin E, 66 IU; vitamin B12 , 34.6 μg; riboflavin, 13.2 mg; niacin, 110 mg; pantothenic acid, 22 mg; vitamin K, 4 mg; folic acid, 2.2 mg; thiamine, 4 mg; pyridoxine, 8 mg; and biotin, 252 μg.

Brake [11]. Briefly, each egg was stained with a dye solution containing 0.5 g of methylene blue crystals dissolved in 70% ethanol. The solution was placed on the inside of the egg for 30 min then the excess dye solution was poured off and the egg was allowed to dry. Then 4 equally spaced 0.25cm2 squares were drawn on the large end of the egg. The pores in each square were counted using a stero microscope on low power. The 4 numbers were then averaged for statistical analysis. Protein Content of Albumen Total protein content of the albumen was determined using the Pierce TM BCA Protein Assay Kit [20] following manufacturer’s instructions. Briefly, the whole albumens from 24 eggs were placed into individual whirl-pak bags and homogenized in a stomacher for 30 s. Then a 100 μl sample of homogenized albumen was collected using wide bore pipette tips to ensure a sufficient

sample was collected due to the thick consistency of the albumen. This 100 μl sample was diluted into 900 μl 1XPBS +2% SDS, but this dilution was not sufficient, so another 1:10 dilution was required; again this dilution was not sufficient to obtain measurable results so a final 1:5 serial dilution was performed resulting in a final dilution of 1:500. 25 μL of diluted sample, and 200 μL of working stock reagent (supplied by kit) was placed into a 96-well microplate. Each sample was run in triplicate. The plate was sealed and incubated at 37◦ C for 30 min. Absorbencies of the solutions were read at 570 nm.

RESULTS AND DISCUSSION There were significant increases (P < 0.0001) observed in egg weights from the groups on the HPE diet. Eggs from hens fed the LPE diet were smaller (59.76 g) by almost 5 g than the eggs from the HPE group (64.27 g). The

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Control %

Ingredient

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4 Table 2. Ingredient composition of layer diets. Low %

High %

Yellow corn Oats Poultry fat Poultry by-pProduct meal Soybean meal Soybean hulls Calcium carbonate Dicalcium phosphate Salt DL-Methionine Choline Trace mineral mix1 Vitamin pre-mix2 Selinium Amprolium

52.2 0 6.4 10.5 12.5 7.7 8.7 1.3 0.3 0.1 0 0.2 0.1 0.1 0.1

37.2 25.0 0 0 7.2 18.7 8.8 2.0 0.3 0.2 0.1 0.2 0.1 0.1 0.1

41.5 0 9.1 12.5 26.5 0.1 8.8 0.8 0.3 0.1 0 0.2 0.1 0.1 0.1

Formulated percentages Crude protein Crude fat Crude fiber Calcium Metabolizable energy

Control (%) 18.00 10.00 4.40 4.00 2998.3 kcal/kg

Low (%) 12.00 2.99 10.46 4.00 2204.6 kcal/kg

High (%) 24.00 12.30 1.69 4.00 3218.8 kcal/kg

18.60%

12.40%

24.80%

Analysis (actual percentages) Crude protein 1

The trace mineral mix contained the following per kg of diet: Manganese, 120 mg; zinc, 120 mg; iron, 80 mg; copper, 10 mg; iodine, 2.5 mg; and cobalt, 1.0 mg. 2 The vitamin premix contained the following concentrations per kg of feed: Vitamin A, 13,200 IU; cholecaleciferol, 4,00 IU; vitamin E, 66 IU; vitamin B12 , 34.6 μg; riboflavin, 13.2 mg; niacin, 110 mg; pantothenic acid, 22 mg; vitamin K, 4 mg; folic acid, 2.2 mg; thiamine, 4 mg; pyridoxine, 8 mg; and biotin, 252 μg. Table 3. Effects of varying protein and energy diets on egg weights and egg contents.1 Treatment2 LPE Control HPE Pooled SE

Weight (g) b

59.76 63.08a 64.27a 0.69

Albumen (g) b

35.45 40.17a 40.49a 0.56

Yolk (g) b

16.04 19.19a 19.58a 0.26

Albumen % a

59.29 63.66a 62.95a 0.36

Yolk % c

26.86 31.59a 30.45b 0.31

n 25 25 25

Values with different superscripts in the same columns differ significantly (P ≤ 0.05). Each value represents the mean of 25 eggs sampled for each group when the hens were 30 wk of age. 2 The diets were: LPE (12.4% CP; 2204.6 kcal/kgME); HPE (24.8% CP; 3218.8 kcal/kg ME); and control (18.6% CP; 2998.3 kcal/kg ME). a–c 1

eggs from the control group (63.08 g) were significantly heavier than the LPE group but not statistically different from the HPE group (Table 3). These data are in agreement with work reported by Shim et al. [6] that hens fed higher levels of protein had heavier egg weights. These data are also in agreement with the work of Gunawardana et al. [2] as well as work by Zimmerman [5] who reported that egg size in

layers can be controlled with precise nutrient delivery. Similar trends were observed in both albumen and yolk weights. There were significant differences (P < 0.0001) in weights of albumen and yolk weights found between treatments. There were no differences found between the HPE and control groups in regard to albumen and yolk weights. However, the egg weights in the LPE

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Control %

Ingredient

LOWMAN AND ASHWELL: EGG COMPONENTS Table 4. Effects of varying protein and energy diets on eggshell thickness and shell pore counts.1 Treatment2 LPE Control HPE

Thickness (mm)

SEM

Pore #

SEM

n

.42a .41a .38b

.5 .5 .5

29.51a 25.10b 23.98b

.9 .9 .9

25 25 25

a,b

Values with different superscripts in the same columns differ significantly (P ≤ 0.05). 1 Each value represents the mean of 25 eggs sampled for each group when the hens were 30 wk of age. 2 The diets were: LPE (12.4% CP; 2204.6 kcal/kgME); HPE (24.8% CP; 3218.8 kcal/kg ME); and control (18.6% CP; 2998.3 kcal/kg ME). Table 5. Effect of varying protein and energy diets on albumen protein content.1 Treatment2 LPE Control HPE

Total Protein (mg/mL) b

147.5 188.7a 182.7a,b

SEM

n

14.3 13.6 13.6

22 24 24

a,b

Values with different superscripts in the same columns differ significantly (P ≤ 0.05). 1 Each value represents the mean of eggs sampled for each group when the hens were 30 wk of age. 2 The diets were: LPE (12.4% CP; 2204.6 kcal/kgME); HPE (24.8% CP; 3218.8 kcal/kg ME); and control (18.6% CP; 2998.3 kcal/kg ME).

thickness of laying hens raised in differing housing designs, but that these differences were due to the amount of feed the birds consumed in the various housing designs, not the composition of the feed. There were significant differences observed in total protein content of the eggs (Table 5). The control group had the highest total albumen protein content (188.7 mg/ml) followed closely by the HPE group (182.7 mg/ml). The HPE group had a total protein intermediate of the LPE and control groups, approaching significant difference from the LPE group (p ≤ 0.07). However, the control group had significantly higher (p ≤ 0.04) levels of total albumen protein than did the LPE group. The mechanism for this effect has not been documented in the literature as of yet. One possible theory for this phenomenon could be that there are less amino acids available when the tubular gland cells of the magnum begin to deposit albumen. Further exploration of this occurrence must be conducted to fully understand the processes that are occurring. From this research it appears that with further investigation,

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group were associated with significantly lower weights for both the albumen (35.45 g) and yolk (16.04 g) (Table 3). These correlate well with previous research due to the fact that increased egg weights are a result of an increase in contents. These findings are in agreement with similar work conducted by Gunawardana et al. [2] who also showed increased albumen and yolk weights in layers on higher CP diets compared to birds on lower CP diets. The results are in agreement with Noavk et al. [22], as well as Penz and Jensen [4]. These data suggest that the laying hens on lower CP diets could not be receiving sufficient amino acids for optimal albumen formation. The interesting element of the egg component data is that the control group had a significantly higher yolk percentage (31.59%) than did the HPE or LPE groups of 30.45 and 26.86%, respectively (Table 3). Novak et al. [22] reported similar findings in laying hens: Birds on lower CP diets had larger percentages of yolk than birds on high CP diets. This supports our results for the differences observed between the control and HPE groups; however, our LPE treatment still had a lower percentage of yolk than the control and HPE groups. Our LPE group also was fed a diet with CP (12%) that was much lower than that used by Novak et al. [21]. Also, our LPE diet contained lower caloric levels; diets low in ME have been shown not to provide the bird with enough exogenous fat to supply sufficient amounts of lipids for the hen to mobilize to form the yolk [23], thereby explaining the difference in egg sizes. Differences also were observed in shell thickness and pore concentration. The LPE and control groups had significantly thicker (p < 0.0001) shells than the HPE group (Table 4). Gunawardana et al. [2] reported that increasing dietary protein in laying hens significantly decreased eggshell percentages due to a an increase in total egg weight. Nahashon et al. [24] found that guinea fowl on either high CP or ME diets had decreased shell thicknesses. The average pore concentrations of the LPE group were significantly higher (p < 0.0004) than pore concentrations of the control and HPE groups (Table 4). This data can be explained and supported by the simple fact that as egg size increases the pore concentration decreases. Karcher et al. [25] found differences in shell

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6 a producer may be able to change the albumen protein content of eggs, making an egg that may be more appealing to some consumers.

CONCLUSIONS AND APPLICATIONS

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1. Decreases in dietary CP and ME levels can significantly decrease egg weights and component percentages, primarily % yolk and albumen. 2. Increasing dietary CP and ME levels appears to significantly decrease shell thickness and pore concentration due to changes in egg size. 3. Dietary CP levels appear to have some effect on total protein concentration of resultant albumen.

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