Effects of Breeder Age and Dietary Fat Source and Level on Broiler Hatching Egg Characteristics 1,2

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1 Effects of Breeder Age and Dietary Fat Source and Level on Broiler Hatching Egg Characteristics 1,2 E. D. Peebles,*,3 C. D. Zumwalt,* S. M. Doyle,* P. D. Gerard, M. A. Latour, 4 C. R. Boyle, and T. W. Smith* *Department of Poultry Science, Experimental Statistics Unit, and College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi ABSTRACT The effects of breeder age and added dietary Significant increases in yolk:albumen ratio occurred between fat source and level on broiler hatching egg charac- teristics were evaluated. Diets included no added fat (NAF) or 3.0% added poultry fat (PF) for peak energy intakes of 430 and 467 kcal/hen-day (PCD) or 1.5% PF or 3.0% corn oil (CO) at 449 PCD. As added dietary fat was changed from CO to PF, the percentage of unsaturated dietary fatty acids, including linoleic acid, decreased. Feeding of experimental diets was initiated when breeders were 22 wk old. Total fresh egg weight; eggshell weight; percentages of yolk (PYK), albumen (PAB), and eggshell (PSHL) weights; and yolk:albumen ratio were measured at various weeks between 26 and 47 wk of age. Egg weight increased progressively with hen age. Weeks 26 and 31 and between Weeks 31 and 35. Low (430 PCD) dietary energy levels significantly reduced PYK at 35 wk and increased PAB across breeder age. Eggshell weight was lower in birds fed moderate (449 PCD) compared to low energy levels at Week 26, moderate compared to high (467 PCD) energy levels at Week 41, and PF compared to CO across fat level at Week 31. At Weeks 31 and 41, PSHL was increased by the use of 3.0% PF compared to 1.5%, and PSHL was increased at Weeks 26 and 41 by using added PF compared to CO across fat level. Increased dietary energy decreased PAB and the use of added dietary CO rather than PF decreased PSHL in broiler breeders between 26 and 47 wk of age. (Key words: albumen, broiler breeder, dietary fat, energy, shell, yolk) 2000 Poultry Science 79: INTRODUCTION Broiler breeder age (Mather and Laughlin, 1979; Noble et al., 1986; O Sullivan et al., 1991; Latour et al., 1996) and diet (Tullett, 1990; Latour et al., 1996; Peebles et al., 1998) influence subsequent embryogenesis and hatchability of broiler eggs. Age (Peebles and Brake, 1987; O Sullivan et al., 1991; Benton and Brake, 1996; Latour et al., 1998) and diet (Brake, 1990; Latour et al., 1998), likewise, affect internal egg and eggshell quality characteristics. O Sullivan et al. (1991) reported that yolk and albumen weights and yolk:albumen ratios increased as hen age increased. Furthermore, the use of added poultry fat (PF) in broiler breeder diets caused increased egg weight (Brake et al., 1989) and decreased eggshell percentage (Brake, 1990). Research reports regarding the comparative influences of various broiler breeder dietary fat sources and levels, apart from the associated influences of energy level on egg and eggshell quality, are lacking in the literature. Therefore, the objectives of this research were to investigate the effects of breeder hen age and different sources and levels of added dietary fats that vary in degree of saturation on egg weight; eggshell weight; percentages of egg yolk (PYK), albumen (PAB), and shell (PSHL) weight; and yolk:albumen ratio in broiler breeders throughout the production cycle. MATERIALS AND METHODS Received for publication August 30, Accepted for publication February 7, This in Journal Article No. J-9539 from the Mississippi Agricultural and Forestry Experiment Station supported by MIS Use of trade names in this publication does not imply endorsement by Mississippi Agricultural and Forestry Experiment Station of these products, nor similar ones not mentioned. 3 To whom correspondence should be addressed: Poultry Science Department, Mississippi State University, Box 9665 Mississippi State, MS ; dpeebles@poultry.msstate.edu. 4 Current address: Department of Animal Science, Purdue University, 1151 Lilly Hall, West Lafayette, IN General Male and female broiler breeder chicks were obtained from Arbor Acres Farm, Inc. Housing and management Abbreviation Key: CO = added corn oil diet; L:D = hours of light:hours of darkness; NAF = no added fat diet; PAB = percentage egg albumen; PCD = peak kcal/hen-day; PF = added poultry fat diet; PSHL = percentage eggshell; PYK = percentage egg yolk. 698

2 BREEDER AGE, DIETARY FAT AND EGG CHARACTERISTICS 699 of birds during the prebreeder and breeder periods were as described by Latour et al. (1996). Briefly, 20 hens and four males were assigned to each of 24 breeder pens (six treatments with four replicates per treatment) in a curtainsided breeder house. Each treatment group of hens was limit-fed one of six different basal corn-soybean mash diets. Males were fed a common basal corn-soybean mash diet. Separate sex feeding was accomplished by feeding females from a male-excluding trough and grill. Dietary treatments began at Week 22 and were accompanied by a photoperiod change from a cycle of 10 h light:14 h darkness to a 15.5 L:8.5 D cycle to initiate lay. Amounts of feed were adjusted weekly to maintain BW gains as recommended by Arbor Acres. 5 Five-day increases in feed began before lay so that feed allotments were adjusted from kg/100 birds per d at housing to kg/ 100 birds per d at initiation of lay. After egg lay commenced, feed allotments were given for the maintenance of optimum hen-day egg production as further recommended by Arbor Acres. Environment Time of breeder housing was in early summer (beginning of June), when the mean environmental temperature was 23.9 C and natural day length provided a 14 L:10 D cycle. At 26 (July), 36 (September), and 47 (December) wk of age, mean environmental temperatures were 27.4, 21.0, and 8.7 C, respectively. Experimental Diets Six diets were formulated to meet or exceed National Research Council (1994) specifications (Table 1). Diets 1 and 2 allowed each bird to reach an energy intake of 467 kcal/d at peak egg production [467 peak kcal/hen-day (PCD)]. Diets 3 and 4 contained the lowest energy levels (430 PCD). Diets 5 and 6 contained moderate energy levels (449 PCD). Diets 1 and 3 contained 3.0% PF; Diets 2 and 4 contained no added fat (NAF); Diet 5 contained 1.5% PF, and Diet 6 contained 3.0% added corn oil (CO). Respective abbreviations for Diets 1 through 6 are: 3PF-467, NAF-467, 3PF-430, NAF-430, 1.5PF-449, and 3CO-449. Determined analyses of the CP, crude fat, ash, and moisture compositions of Diets 1 through 6 are included in Table 1. Determined analyses of the fatty acid compositions of Diets 1 through 6 show that relative proportions of saturated and unsaturated fatty acids reflect the source of dietary fat (Table 2). Determined analyses of diets were performed according to the methods of the Association of Official Analytical Chemists (1980). The levels of ethoxyquin added to diets exceeded the total antioxidant potential currently recommended by manufacturers for the fats utilized. 5 Broiler Breeder Male and Female, Feeding and Management Guide, December Arbor Acres Farm, Inc., Glastonbury, CT. Egg, Yolk, Albumen, and Eggshell Weights Only nest eggs that were not dirty, misshapen, broken, cracked, excessively small, or double-yolked were collected for analysis twice daily from each pen at 1000 and 1500 h. Total fresh egg, yolk, albumen, and eggshell weights were measured at 26, 31, 35, 41, and 47 wk of breeder hen age. For measurement of the above parameters, approximately 10 eggs at each week were collected from each pen replicate. Eggshell weight was obtained according to the procedure of Brake et al. (1984). Eggshell weight was also calculated as a percentage of total egg weight. Weights of the yolk and albumen were expressed as percentages of total egg weight. In addition, the ratio of the weights of yolk and albumen was calculated. Replicate pen means for each parameter were used for analyses. Statistical Analyses The experimental design was completely randomized. Six breeder hen dietary treatments with four replicates per treatment were utilized in all data analyses. Replicate means were analyzed with split-plot analysis to test for the effects of breeder hen dietary treatment, age, and their interactions on egg weight, eggshell weight, PYK, PAB, PSHL, and yolk:albumen ratio. Angular transformations (arc sine of the square root of the proportion affected) were performed on all percentage data prior to analysis (Steel and Torrie, 1980). Means were compared by Fisher s protected least significant difference (Steel and Torrie, 1980). Data were further tested by contrast analysis. The effects of energy level (430, 449, or 467 ME at peak egg production), added fat source across level and only at the 3.0% level (PF or CO), and level of PF (1.5 or 3.0%) were tested. When age by dietary treatment interactions were significant, contrasts were performed within each breeder age period. All data were analyzed with the GLM procedure of the SAS Institute (1996). Statements of significance were based on P 0.05, unless otherwise indicated. RESULTS There was a significant (P ) main effect due to breeder hen age for egg weight, PAB, and yolk:albumen ratio (Table 3). Egg weight increased significantly between all time periods. Percentage albumen weight decreased significantly between Weeks 31 and 35 and 35 and 41 but increased significantly between Weeks 41 and 47. The yolk:albumen ratio increased significantly between Weeks 26 and 31 and 31 and 35. There were significant breeder age by dietary treatment interactions for PYK (P 0.04), eggshell weight (P 0.02), and PSHL (P 0.01) (Table 4). At Week 26, PYK was greater in hens fed the 3PF-467 diet compared to the 3PF- 430 diet, with all other dietary treatments being intermediate. At Week 26, the NAF-430 diet resulted in a significantly higher eggshell weight compared to the 3CO-449

3 700 PEEBLES ET AL. TABLE 1. Ingredient percentages and calculated and determined analyses of breeder diets Ingredient Diet 1 Yellow corn % Soybean meal Wheat middlings Limestone Menhaden fishmeal Defluorinated phosphate Micronutrient premix Sodium chloride DL-methionine Lysine HCL, 4 78% Poultry fat Corn oil Dietary analyses CP, calculated CP, determined ME, calculated kcal/kg 2,940 2,940 2,709 2,709 2,826 2,826 Lysine, calculated TSAA, calculated Tryptophan, calculated Calcium, calculated Available phosphorus, calculated Sodium, calculated Ash, determined Moisture, determined Crude fat, calculated Crude fat, determined Linoleic acid, calculated Diets 1 through 6, respectively, contain: 1) 3.0% added poultry fat and 467 peak kcal/hen-day (PCD), 2) no added fat and 467 PCD, 3) 3.0% added poultry fat and 430 PCD, 4) no added fat and 430 PCD, 5) 1.5% added poultry fat and 449 PCD, and 6) 3.0% added corn oil and 449 PCD. 2 Supplied the following per kilogram of finished feed: vitamin A acetate, 11,000 IU; cholecalciferol, 2,750 IU; α-tocopheral acetate, 22 IU; riboflavin, 7.7 mg; niacin, mg; d-pantothenic acid, 13.2 mg; folic acid, 1.1 mg; vitamin B 12,13µg; biotin, 110 µg; choline chloride, 441 mg; thiamine, 1.8 mg; pyridoxine, 4.7 mg; menadione sodium bisulfite, 4.96 mg; ethoxyquin, 55 mg; manganese, 55 mg; zinc, 50 mg; iron, 30 mg; copper, 5 mg; iodine, 0.50 mg; and selenium, 0.1 mg. Manufactured by Hoffman-LaRoche, Inc., Nutley, NJ Manufactured by Degussa Corp., Ridgeland Park, NJ Manufactured by Heartland Lysine, Inc., Chicago, IL diet with all others being intermediate. Conversely, at Week 31, eggshell weight was higher for the 3CO-449 group than for the NAF-430 and 1.5PF-449 groups; the others were intermediate. At Week 41, eggshell weight in the 3PF-467 group was greater compared to the 1.5PF- TABLE 2. Determined percentages of total fatty acids of broiler breeder diets Fatty acid type Diet 1 (%) 449 and 3CO-449 groups, and all other treatments were intermediate. At Week 47, the 1.5PF-449 treatment led to a higher eggshell weight than the NAF-467 treatment; all others were intermediate. Percentage eggshell weight was affected at Weeks 26, 31, and 41. At Week 26, the NAF- Myristic Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Percentage saturated fatty acids Percentage unsaturated fatty acids Diets 1 through 6, respectively, contain: 1) 3.0% added poultry fat and 467 peak kcal/hen-day (PCD), 2) no added fat and 467 PCD, 3) 3.0% added poultry fat and 430 PCD, 4) no added fat and 430 PCD, 5) 1.5% added poultry fat and 449 PCD, and 6) 3.0% added corn oil and 449 PCD. (%)

4 BREEDER AGE, DIETARY FAT AND EGG CHARACTERISTICS 701 TABLE 3. Egg weight, percentage albumen weight, and yolk:albumen ratio of eggs from breeder hens at 26, 31, 35, 41, and 47 wk of age Egg weight Albumen weight Yolk:albumen Week (g) (%) ratio e 60.8 a 0.45 c d 59.9 a 0.47 b c 58.3 b 0.53 a b 57.1 c 0.53 a a 58.4 b 0.53 a Pooled SEM a e Means within variables for different week with no common superscript differ significantly (P 0.05). 430 and 1.5PF-449 diets resulted in a significantly greater PSHL than did the 3CO-449 diet with all others being intermediate. Conversely, at 31 wk, the NAF-467, 3PF- 430, and NAF-430 diets resulted in a higher PSHL than did the 1.5PF-449 diet; all others were intermediate. At 41 wk, PSHL was significantly higher for eggs from hens fed 3PF-467 compared to 3CO-449; all other dietary treatments were intermediate. There were significant contrasts within breeder age for PYK, eggshell weight, and PSHL (Table 5). Contrast analyses revealed that at Week 35, PYK was significantly higher in eggs from birds fed high or moderate energy levels compared to those fed low energy levels. Birds fed moderate energy diets laid eggs with a significantly lower eggshell weight compared to birds fed low energy diets at Week 26 and those fed high energy diets at Week 41. At Weeks 31 and 41, PSHL was significantly higher in eggs from birds fed high or low energy levels compared to those fed moderate energy levels. Eggshell weight at Week 31 was higher in birds fed CO compared to PF across fat level. At Week 26, PSHL was higher in birds fed 1.5% added PF compared to 3.0% PF, and was higher in birds fed PF compared to CO across fat level. However, at Week 31, eggshell weight and PSHL were higher in birds fed 3.0% compared to 1.5% levels of PF. Furthermore, at Week 41, PSHL was higher in birds fed 3.0% added PF than 1.5% added PF. Also, at Week 41, PSHL was higher for birds fed PF compared to CO across fat level and only at the 3.0% level. Contrast analyses across breeder age also showed that PAB was significantly higher in eggs from birds fed low compared to moderate (P 0.04) and low compared to high (P 0.01) energy levels. Mean PAB for low, moderate, and high energy level groups were 59.6, 58.7, and 58.5% (pooled SEM = 0.34), respectively. DISCUSSION Egg weight increased with hen age through Week 47 in the present study. Egg weight also has been shown to increase between Weeks 26 and 58 in commercial layers (Fletcher et al., 1981). Likewise, Shanawany (1984) showed egg weight to increase with broiler breeder age between 28 and 44 wk, and O Sullivan et al. (1991) reported that eggs from broiler breeders increased in weight between Weeks 29 and 62. Ahn et al. (1997) reported that the yolk:albumen ratio of eggs from Single Comb White Leghorn chickens was highest between 55 and 78 wk of age; whereas, this ratio was lowest at 28 wk. Similarly, in eggs from breeder hens in this study, the yolk:albumen ratio increased between Weeks 26 and 31 and 31 and 35 and was highest between Weeks 35 and 47. Furthermore, in broiler breeders, O Sullivan et al. (1991) demonstrated that yolk and albumen weights of eggs increased with egg weight between 29 and 62 wk but that increased yolk:albumen ratio during that period was due to a larger increase in yolk relative to albumen. In commercial layers, Fletcher et al. (1981) reported that with increasing flock age between 26 and 58 wk, PYK increased, whereas PAB decreased. Percentage albumen weight was observed to decrease with flock age at various intervals in this study; however, an unexpected increase in PAB between Weeks 41 and 47 may have resulted from relatively slower increases in the weights of other egg components and the total egg during that time. O Sullivan et al. (1991) showed that an increase in yolk:albumen ratio with breeder age reflected large increases in wet and dry relative yolk weight. The present results also demonstrate similarities to the data of Fletcher et al. (1981) in that decreases in PAB were associated with increases in yolk:albumen ratio between Weeks 31 and 35. TABLE 4. Eggshell weight and percentages of eggshell and yolk weights of eggs from breeder hens at 26, 31, 35, 41, and 47 wk of age fed Diets 1 through 6 Eggshell weight 1 Eggshell weight 1 Yolk weight 1 Diet 2 26 wk 31 wk 35 wk 41 wk 47 wk 26 wk 31 wk 35 wk 41 wk 47 wk 26 wk 31 wk 35 wk 41 wk 47 wk (g) (%) ab 5.22 abc a 6.00 ab 8.9 ab 8.9 ab a a ab 5.33 ab ab 5.85 b 9.1 ab 8.9 a ab ab ab 5.29 ab ab 6.01 ab 9.0 ab 9.0 a ab b a 5.19 bc ab 6.04 ab 9.2 a 8.9 a ab ab ab 5.05 c b 6.10 a 9.3 a 8.5 b ab ab b 5.43 a b 5.90 ab 8.7 b 8.9 ab b ab a,b Means within variables for different week with no common superscript differ significantly (P 0.05). 1 Pooled SEM for all diets across week = 0.08, 0.1, and 0.8 for eggshell weight, percentage eggshell weight, and percentage yolk weight, respectively. 2 Diets 1 through 6, respectively, contain: 1) 3.0% added poultry fat and 467 peak kcal/hen-day (PCD), 2) no added fat and 467 PCD, 3) 3.0% added poultry fat and 430 PCD, 4) no added fat and 430 PCD, 5) 1.5% added poultry fat and 449 PCD, and 6) 3.0% added corn oil and 449 PCD.

5 702 PEEBLES ET AL. TABLE 5. Significant contrasts within breeder age for eggshell weight and percentages of eggshell and yolk weights Variable Week Contrast 1 and (mean) 2 P > F Eggshell weight (g) 26 Moderate (4.62) vs. low (4.78) energy PF (5.20) vs. CO (5.42) across level % PF (5.06) vs. 3.0% PF (5.27) High (5.88) vs. moderate (5.65) energy 0.01 Eggshell weight (%) 26 PF (9.0) vs. CO (8.7) across level % PF (9.3) vs. 3.0% PF (8.9) High (8.9) vs. moderate (8.7) energy 0.05 Moderate (8.7) vs. low (9.0) energy % PF (8.5) vs. 3.0% PF (8.9) High (9.0) vs. moderate (8.7) energy Moderate (8.7) vs. low (9.0) energy PF (8.9) vs. CO (8.7) across level % PF (8.7) vs. 3.0% PF (9.1) % PF (9.1) vs. 3.0% CO (8.7) Yolk weight (%) 35 High (30.7) vs. low (29.6) energy Moderate (30.4) vs. low (29.6) energy Contrast types are followed in parentheses by the diet combinations compared: High vs. low energy (1 and 2 vs. 3 and 4), high vs. moderate energy (1 and 2 vs. 5 and 6), low vs. moderate energy (3 and 4 vs. 5 and 6), PF vs. CO across levels (1, 3, and 5 vs. 6), PF vs. CO at 3.0% (1 and 3 vs. 6), 1.5 vs. 3.0% PF (5 vs. 1 and 3). Diets 1 through 6, respectively, contain: 1) 3.0% added poultry fat (PF) and 467 peak kcal/hen-day (PCD), 2) no added fat and 467 PCD, 3) 3.0% added PF and 430 PCD, 4) no added fat and 430 PCD, 5) 1.5% added PF and 449 PCD, and 6) 3.0% added corn oil (CO) and 449 PCD. 2 Pooled SEM for all contrasts across the weeks specified = 0.06, 0.08, and 0.4 for eggshell weight, percentage eggshell weight, and percentage yolk weight, respectively. French and Tullett (1991) have described research conducted on turkeys by French and Shaw (1989) that show that as hens aged, increased egg weight was associated with increased PYK and decreased PAB. More recently, Lapão et al. (1999) reported that albumen height decreased and albumen ph increased in fresh eggs with broiler breeder hen age between 32 and 59 wk. Albumen weight is also largely dependent upon its moisture content, whereas yolk weight is a function of DM accumulation (O Sullivan et al., 1991). Work by Marion et al. (1966) and French and Shaw (1989) has shown that although increased egg weight with hen age is associated with increased yolk weight, albumen weight primarily affects variation in egg weight at a given hen age. Conversely, long-term genetic selection in Single Comb White Leghorn chickens has produced larger eggs that have lower PYK (Tharrington et al., 1999). The inclusion of supplemental fats (Sell et al., 1987) and the elimination of ME deficiencies (Harms and Waldroup, 1963; Bray, 1967) in diets of commercial layers have been shown to increase egg weight. Jensen et al. (1958) demonstrated that CO contains a factor necessary for maximizing egg size, and Shutze et al. (1962) identified the agent as linoleic acid. Menge et al. (1965) further showed that linoleic acid is required for maximizing egg size in linoleic acid-deficient hens but that greater than 20 mg/d had no further beneficial effect. However, no dietary effects were noted for the egg weight of broiler breeders in the current study. Research in a number of other laboratories has also detected no effect of supplemental fat on egg weight of layers (Sell et al., 1979; Summers and Leeson, 1983; Atteh and Leeson, 1985). Sell et al. (1987) suggested that the differences in results of the effects of supplemental fat on egg weight may be due to differences in experimental protocol. Although egg weight was not affected by diet, PYK and PAB were influenced by dietary treatment in the present study. In general, low (430 PCD) dietary energy levels were capable of increasing PAB when compared to high (467 PCD) or moderate (449 PCD) energy levels. Low energy levels also decreased PYK compared to high or moderate energy at Week 35; however, yolk:albumen ratio was not significantly affected by energy at any time. These data would, therefore, suggest that increased energy in the diet may compromise albumen deposition in the egg and may promote yolk deposition at certain breeder ages without altering the yolk:albumen ratio. Differences in the effects of dietary energy on egg yolk and albumen size may be associated with the large difference in their fat contents (Burley and Vadehra, 1989). The level of saturation and proportions of component fatty acids in egg yolk can be significantly modified by the amounts of unsaturated fatty acids in a diet (Cruickshank, 1934; Cherian and Sim, 1991). However, these data also showed that PYK and egg weight were not influenced by the source of fat added to the breeder diets. Associated changes in dietary linoleic acid content, as indicated in Table 2, were also shown to have no effect. Eggshell quality decreases after the first few months of lay (Petersen, 1965). Unpublished data taken from the same flock of birds as in the present study showed that egg specific gravity also decreased with hen age between Weeks 31 and 43. The results of this study demonstrate the independent influences of dietary energy and fat source on eggshell weight and PSHL at various breeder ages through Week 41. Furthermore, breeder age may

6 BREEDER AGE, DIETARY FAT AND EGG CHARACTERISTICS 703 markedly alter the effects of specific dietary energy and fat source combinations on the eggshells of broiler hatching eggs. This effect is noticeably demonstrated by the opposite effects of the 3CO-449 and NAF-430 diets on eggshell weight at Weeks 26 and 31. Consistent effects were found due to dietary fat source on PSHL. When compared to PF, CO decreased PSHL at the 3.0% level on Week 41 and across fat level on Weeks 26 and 41. When compared to control diets containing 0% added fat, Brake (1990) found that diets containing 4 or 6% added PF decreased PSHL in broiler breeders. Brake (1990) suggested that the significant decrease in PSHL was due to a slight increase in egg weight in association with a constant eggshell weight. It was further proposed, based on earlier work (Brake et al., 1989), that the increase in egg weight was due to the higher levels of linoleic acid in the 4 and 6% added PF diets when compared to the control diets. The average linoleic acid contents in the PF and CO diets across level (PF = 32.4% and CO = 51.8%) and at 3.0% (PF = 29.8% and CO = 51.8%) (Table 2) indicate that the diets with added CO contained approximately 20% more linoleic acid as a percentage of total dietary fatty acids than did the diets with added PF. These data confirm earlier work (Brake et al., 1989; Brake, 1990), suggesting that increased dietary levels of linoleic acid depress PSHL. The decrease in PSHL was not associated with a significant increase in egg weight, as was noted by Brake (1990). Furthermore, at one point in time (Week 31), eggshell weight was increased in birds fed CO when compared to those fed PF. 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