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Effect of body weight and energy intake on body composition analysis of broiler breeder hens
Effect of body weight and energy intake on body composition analysis of broiler breeder hens
Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701 nificantly, greater (P < 0.05) amounts of fat mass and lower amounts of lean mass were evident at the beginning of the production period for HBW hens compared with SBW and LBW hens. Higher levels of energy intake also affected body composition. Namely, fat deposition was greatest throughout the production period in hens consuming 480 kcal/d at peak intake (P < 0.05). Critically, fluctuations to lean and fat mass throughout the production period are suggestive of underlying regulatory processes. Specifically, hens appears to maintain consistent lean mass throughout the production period with a coefficient of variation of <12% across all birds. The results of this study provide important BB body composition information from management and nutrition studies that showed the dynamics of body composition change during the production period.
ABSTRACT A study was conducted to determine the effect of different feeding programs and energy intakes on the body composition of broiler breeders (BB) from 22 wk of age to 65 wk of age. Cobb 500 BB that had been reared using three growth curves: (1) the control group followed Cobb 500 guidelines (SBW) for target body weights (BW), (2) the second group target BW was 20% heavier (HBW) than the SBW group, and (3) the third group target BW was 20% lighter (LBW) than the SBW group. At 21 wk of age, pullets from each growth curve were assigned to be fed one of six treatments. Diets were formulated and allocated to provide 330, 360, 390, 420, 450, or 480 kcal ME/hen/d and 24 g protein/hen/d, at peak intake. Body composition (lean mass, fat mass, and mineral content) was measured by dual-energy x-ray absorptiometry throughout the production period. Sig-
Key words: body composition, pullet, breeder hen, dual energy x-ray absorptiometry, energy intake 2018 Poultry Science 0:1–7 http://dx.doi.org/10.3382/ps/pey377
INTRODUCTION
tance of carcass protein and fat as an influencing factor is increasing (Bornstein et al., 1984; Renema et al., 1999; Hocking, 2004; Melnychuk et al., 2004; De Beer and Coon, 2007; Romero et al., 2009a). Low BW tend to delay the start of lay and lay fewer eggs than medium or heavier BW hens (Robinson and Robinson, 1991). The objective of the study was to evaluate the effect of different feeding programs on the body composition profile of broiler breeder hens during the production cycle using dual energy x-ray absorptiometry (DEXA).
Feed restriction is a necessary tool to manage excessive body weight (BW) gain that may result in adverse effects on reproduction in broiler breeders. The daily intake for broiler breeder pullets may decrease by up to one-third of the normal feed intake of broilers of the same age fed ad libitum or half in birds of the same weight fed ad libitum (Savory and Kostal, 1996; De Jong et al., 2002). The extent of feed restriction is often dictated by recommended target BW throughout the rearing period. Knowledge of body composition and the changes that occur during the life cycle of current broiler breeder strains is important to understand how feeding practices and dietary nutrients might need to be adjusted to supply nutrients appropriate for the stage in growth, sexual maturation and level of egg production. Many report the importance of BW as a determinant for the onset of sexual maturity, though the potential impor-
MATERIALS AND METHODS The study complied with the provisions of the University of Arkansas Institutional Animal Care and Use Committee (Protocol no. 0,9025) as specified by the Animal and Plant Health Inspection Service, United States Department of Agriculture in 9 CFR Part 1(1– 91) for use of poultry in research.
Experimental Design
C 2018 Poultry Science Association Inc. Received February 19, 2018. Accepted October 17, 2018. 1 Corresponding author: [email protected]
One hundred and forty-four pullets of 21 wk of age were assigned to 1 of 6 experimental diets. This 1
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C. Salas, R. D. Ekmay, J. England, S. Cerrate, and C. N. Coon1
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SALAS ET AL. Table 1. Composition (%) and nutrient content of diets fed during the production period. Diet 1
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
Corn Soybean meal Limestone Wheat middling Dicalcium phosphate Salt Sodium bicarbonate DL-methionine 98.5% Fat Vitamin premix1 Choline chloride Trace mineral mix2 Copper sulfate L-lysine Selenium premix Ethoxyquin Total Nutrient CP % (calculated) CP % (analyzed) ME, kcal/kg (calculated) AMEn kcal/kg (analyzed)3 Calcium % Non-phytate P % Total P % Lysine % Methionine % Methionine + Cystine %
44.23 34.62 10.37 2.50 1.42 0.34 0.20 0.35 5.55 0.20 0.08 0.05 0.05 – 0.02 0.02 100
51.26 29.99 9.58 2.50 1.27 0.34 0.20 0.31 4.14 0.18 0.09 0.05 0.05 0.01 0.02 0.02 100
57.44 25.91 8.88 2.50 1.14 0.34 0.20 0.27 2.89 0.17 0.10 0.05 0.05 0.01 0.02 0.02 100
62.38 22.65 8.32 2.50 1.03 0.34 0.20 0.24 1.90 0.16 0.11 0.06 0.05 0.02 0.02 0.02 100
66.92 19.66 7.81 2.50 0.94 0.34 0.20 0.21 0.99 0.15 0.11 0.06 0.05 0.03 0.02 0.02 100
71.02 16.96 7.35 2.50 0.85 0.34 0.20 0.19 0.16 0.14 0.12 0.06 0.05 0.03 0.02 0.02 100
20.8 20.8 2860 2932 4.16 0.40 0.63 1.16 0.67 1.01
19.1 19.2 2860 2894 3.83 0.37 0.59 1.04 0.61 0.93
17.6 17.9 2860 2951 3.54 0.34 0.55 0.94 0.56 0.86
16.4 16.2 2860 2849 3.31 0.32 0.52 0.86 0.51 0.80
15.3 15.7 2860 2952 3.09 0.30 0.49 0.78 0.48 0.75
14.3 14.4 2860 2820 2.9 0.28 0.47 0.71 0.44 0.7
1 Vitamin mix provided per kg of mix: vitamin A (vitamin acetate), 4500,000 IU; vitamin D3, 2250,056 ICU; vitamin E, 22,500 IU; niacin, 25,313 mg; D-pantothenic acid, 11,250 mg; riboflavin, 6750 mg; thiamine, 1125 mg; menadione, 1125 mg; folic acid, 1125 mg; biotin, 113 mg; vitamin B12, 10 mg; pyridoxine, 2250 mg. 2 Trace mineral mix provided per kg of mix: manganese (MnSO4.H2O), 10%; zinc (ZnSO4.7H2O), 10%; iron (FeSO4.7H2O), 5%; copper CuSO4.5H2O), 1%; iodine (Ca(IO3)2.H2O), 1000 ppm; magnesium (magnesium oxide), 2.70%. 3 Average AMEn of the diets throughout the experimental period. Standard error was 31.6 kcal.
resulted in a 3 (BW) × 6 (peak kcal ME intakes) factorial arrangement (Tables 2 and 3) with a total of 18 treatments during the production period. Each bird was housed in individual cages (47 cm × 30.5 cm × 47 cm) and each cage was equipped with a nippletype drinker and individual feeder. Production performance was recorded daily during the trial. Egg weights were recorded every 5 wk by collecting and weighing all egg laid during the week. Diets (Table 1) were formulated to contain 2860 kcal ME/kg and six different amounts of crude protein (14.3%–20.8% CP). Feed allocation (Table 2) was based on egg production, rather than BW, and designed to provide peak ME kcal intakes of 330, 360, 390, 420, 450, or 480 kcal ME/hen/d and 24 g of ideal protein/hen/d at peak production. This was achieved by adjusting the peak feed intake per hen. The BW at 21 wk of age were a control group (SBW) that had been reared to Cobb 500 target BW and two other groups that were reared to 20% heavier (HBW) or 20% lighter (LBW) BW compared to the SBW group, respectively (Table 3), but otherwise followed Cobb Broiler Breeder Management Guide (2005) recommendations. Birds were light-stimulated at 21 wk, the start of the experimental period. Diet analysis and related rearing information may be found in Supplementary Tables 1 and 2.
Body Composition Body composition of eight hens per treatment (144 total) was measured at 21, 30, 35, 46, 55, and 65 wk of age during the production period using a DEXA scanner (GE Lunar Prodigy, Encore software version 12.20.023) as previously described by Salas et al. (2012) except bids were scanned live. Briefly, birds were restrained and placed prone, un-anesthetized on the DEXA scanner and scanned utilizing the small animal software module (Lunar Prodigy from GE, encore software version 12.20.023). Defining the whole bird as the region of interest, the DEXA provided measurements in grams of bone mineral content (BMC), grams fat content and grams lean mass for each bird. The sum of the DEXA measurements was assumed to be grams total body mass. Results were evaluated using regression equations previously developed and validated using DEXA-reported measurements and actual chemical analysis of the body composition (Salas et al., 2012).
Statistical Analysis The trial was a completely randomized design with a factorial treatment structure. Growth curve, energy intake, and age were considered fixed effects for body composition data. Data were analyzed as repeated measures using the analysis of variance procedure of
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Ingredient
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BODY COMPOSITION AND BREEDER MANAGEMENT Table 2. Feed program for broiler breeder hens during the production period to obtain the energy intake at peak. 21 wk
23 wk
5%5
37%5
53%5
61%5
Peak
35 wk
40 wk
46 wk
50 wk
56 wk
60 wk
106 22 302
115 24 328
115 24 328
115 24 329
115 24 329
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
106 20 302
115 22 328
115 22 330
120 23 342
124 24 353
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
106 19 302
115 20 328
116 20 331
124 22 356
132 23 377
136 24 390
136 24 390
136 24 389
136 24 389
136 24 389
136 24 389
136 24 389
136 24 389
106 17 302
115 19 328
116 19 333
129 21 369
140 23 401
147 24 419
147 24 419
144 24 413
139 23 396
136 22 388
136 22 388
136 22 388
136 22 388
106 16 302
115 18 328
117 18 334
134 20 383
149 23 425
157 24 449
157 24 449
155 24 443
149 23 426
144 22 411
140 21 400
136 21 390
136 21 389
106 15 302
115 16 328
117 17 336
139 20 396
157 22 449
168 24 479
168 24 479
165 24 473
159 23 456
155 22 443
151 22 433
146 21 417
142 20 407
1
1
330 kcal fed diet 1, 360 kcal fed diet 2, 390 kcal fed diet 3, 420 kcal fed diet 4, 450 kcal fed diet 5, 480 kcal fed diet 6. g feed/d—grams feed per bird per day. 3 g CP/d—grams crude protein per bird per day. 4 kcal/d—calculated kcal ME per bird per day. 5 Percent production reached at which time feed amounts were increased. 2
JMP 8.2 (SAS Institute Inc., Cary, North Carolina). Age was not considered into the statistical model for egg production data, except for egg weight data that were analyzed as repeated measures. Each individual hen was considered the experimental unit. When there were significant treatment effects, means were separated using Student’s t-test. Post-hoc trend contrasts were performed on egg production data to determine line shape across energy intake treatments after visual inspection of the data. The level of significance is reported at P < 0.05.
RESULTS Analyzed daily energy intake for each diet was within 3% of target daily energy intake. No significant interactions effects were observed between growth curve, energy, and age, or growth curve by energy intake for body composition components at any age (Tables 3, 4, and 5). When body composition components were expressed on an absolute weight basis (grams), significant interaction effects were observed between growth curve and time, and energy intake and age, respectively, for fat mass but not lean mass (Tables 4 and 5). A significant energy intake by time effect was observed for BMC when expressed on an absolute weight basis. When body composition components were expressed on a percentage basis, significant interaction effects were observed between growth curve and time, as well as energy intake and time, for fat mass and lean mass, but not BMC.
The significant increase in fat mass (g) in HBW breeders carried through into production through 35 wk of age (Figure 1). However, when viewed on a percentage basis, the initial fat mass increase in HBW breeders disappeared by week 30. Logically, energy intake had a significant effect on fat mass with hens consuming the higher energy intake, e.g., 480 kcal/d, having greater fat mass on both an absolute weight basis and percentage basis at all time periods. Energy intake also impacted lean mass deposition; however, the deposition trends were time specific. At 35 wk of age, hens consuming higher energy intakes showed greater lean mass deposition, but the opposite was observed at other time periods. BMC was significantly greater among hens consuming greater energy intakes but only when BMC was expressed on an absolute weight. No significant (P = 0.0592) growth curve by energy intake effect was observed for egg production, and no significant main effects were observed (Table 6). However, a significant quadratic fit was observed with energy intake, with peak production predicted to be between 390 kcal/d and 420 kcal/d. No significant effects were observed for age of first egg or egg weight.
DISCUSSION There is evidence to suggest that carcass fat and a fat pool threshold are important for the onset of production (Bornstein et al., 1984; Hocking, 2004). Hocking (2004) reported that the number of normal yellow follicles at
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330 kcal g feed/d2 g CP/d3 kcal/d4 360 kcal g feed d g CP/d kcal/d 390 kcal g feed/d g CP/d kcal/d 420 kcal g feed/d g CP/d kcal/d 450 kcal g feed/d g CP/d kcal/d 480 kcal g feed/d g CP/d kcal/d
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Table 3. Body weight and composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Growth curve
Energy intake (kcal ME/d)
HBW
SBW
LBW
SEM
330
360
390
420
450
480
SEM
21 30 35 46 55 65
wk wk wk wk wk wk
2528 3849a 4052a 4270a 4307a 4195a
2194 3675b 3900b 4172a 4250a 4168a
1773 3482c 3675c 3981b 4104b 4005b
123.9 30.7 32.9 42.7 49.5 56.7
N/A 3403c 3444e 3590e 3684d 3641d
N/A 3515c 3655d 3883d 3989c 3940c
N/A 3673b 3861c 4175c 4278b 4240b
N/A 3680b 3932c 4165c 4296b 4217b
N/A 3813a 4083b 4359b 4382b 4224b
N/A 3927a 4279a 4673a 4692a 4474a
N/A 43.3 46.5 60.4 70.0 80.2
Fat (g)
21 30 35 46 55 65 21 30 35 46 55 65 21 30 35 46 55 65
wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk
412a 804a 962a 1216 1083 830 2683 2929 2988 2904 3087 3244 70 116 128 150 147 123
188b 736b 872b 1225 1185 880 2427 2826 2909 2796 2908 3162 69 112 118 149 156 127
185b 710b 854b 1207 1083 827 1967 2663 2706 2630 2861 3055 54 109 114 142 145 122
36.9 21.4 33.2 42.5 49.7 42.4 93.8 32.7 39.7 44.5 44.6 44.7 2.9 2.9 3.3 4.9 5.5 5.0
N/A 635d 609d 828d 664d 559d N/A 2660 2737 2642 2880 2976 N/A 107 98d 119c 116d 106c
N/A 697c,d 829c 1072c 981c 697c,d N/A 2709 2770 2673 2871 3135 N/A 109 106c,d 138b,c 137c,d 108c
N/A 719b-d 875b,c 1220b,c 1253a,b 943a,b N/A 2846 2890 2813 2881 3170 N/A 108 118b,c 142b 161a,b 131a,b
N/A 779b,c 954b,c 1248b 1112b,c 835b,c N/A 2789 2852 2760 3035 3263 N/A 111 126b 157a,b 148b,c 120b,c
N/A 797a,b 994a,b 1347b 1241b 950a,b N/A 2899 2958 2856 2982 3140 N/A 117 131a,b 156a,b 158a-c 133a,b
N/A 875a 1115a 1583a 1452a 1091a N/A 2932 3023 2920 3060 3239 N/A 121 140a 169a 174a 144a
N/A 30.3 47.0 60.1 70.3 59.9 N/A 46.2 56.1 63.0 63.0 63.3 N/A 3.9 4.7 6.9 7.8 7.1
Lean (g)
BMC (g)
LBW = light BW, SBW = standard BW, HBW = heavy BW, N/A = not applicable Means within the same row that do not share a letter differ significantly (P < 0.05).
Table 4. Percent body composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Growth curve
Energy intake (kcal ME/d)
HBW
SBW
LBW
SEM
330
360
390
420
450
480
SEM
% Fat
21 30 35 46 55 65
wk wk wk wk wk wk
12.8a 20.8 23.6 29.1 24.5 19.3
6.8b 20.0 22.2 29.1 27.5 20.8
8.2b 20.4 23.1 29.6 25.9 20.3
1.06 0.56 0.87 0.91 1.02 0.84
N/A 18.7c 17.6b 22.9c 17.9d 15.2d
N/A 19.9b,c 22.8a 27.6b,c 24.5c 17.6c,d
N/A 19.7b,c 22.7a 28.3b 29.1a,b 22.3a,b
N/A 21.1a,b 24.2a 32.0a,b 25.7b,c 19.6b,c
N/A 20.9a,b 24.4a 30.7a,b 27.9a-c 22.1a,b
N/A 22.3a 26.1a 33.9a 30.7a 23.9a
NA 0.79 1.23 1.29 1.45 1.19
% Lean
21 30 35 46 55 65 21 30 35 46 55 65
wk wk wk wk wk wk wk wk wk wk wk wk
85.0b 76.1 73.9 70.0 72.1 77.9 2.2 3.0 3.1 3.6 3.4 2.9
90.6a 77.0 74.7 67.4 68.8 76.2 2.6 3.1 3.0 3.6 3.7 3.0
89.4a 76.5 73.8 66.4 70.6 76.7 2.5 3.1 3.1 3.6 3.5 3.0
1.02 0.60 0.74 0.99 1.10 0.89 0.09 0.07 0.09 0.11 0.11 0.11
N/A 78.2a 79.5a 73.7a 78.9a 81.9 N/A 3.2 2.8 3.3 3.2 2.9
N/A 77.1a 75.6b 68.9a,b 73.0b 79.4 N/A 3.0 2.9 3.6 3.4 2.7
N/A 77.4a 74.2b,c 67.4b,c 67.1c,d 74.7 N/A 3.0 3.1 3.4 3.8 3.1
N/A 75.9a,b 72.6c,d 69.5a,b 70.8b,c 77.6 N/A 3.0 3.2 4.0 3.5 2.9
N/A 76.0a,b 72.4c,d 65.7b,c 68.5b-d 74.7 N/A 3.1 3.2 3.6 3.6 3.2
N/A 74.6b 70.6d 62.5c 65.6d 73.0 N/A 3.1 3.3 3.6 3.7 3.2
NA 0.85 1.05 1.40 1.55 1.26 NA 0.10 0.12 0.15 0.15 0.15
% BMC
HBW = heavy BW, SBW = standard BW, LBW = light BW, N/A = not applicable Means within the same row that do not share a letter differ significantly (P < 0.05).
Table 5. P values for body composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production.
Growth curve Energy intake Age Growth curve × energy intake Growth curve × age Energy intake × age Growth curve × energy intake × age
Fat (g)
Lean (g)
BMC (g)
Fat (%)
Lean (%)
BMC (%)
0.3465 < 0.0001 < 0.0001 0.7490 0.0093 < 0.0001 0.9221
< 0.0001 0.0015 < 0.0001 0.0876 0.7357 0.6398 0.8032
0.1275 < 0.0001 < 0.0001 0.4018 0.4726 0.0353 0.9648
0.7706 < 0.0001 < 0.0001 0.6470 0.0124 < 0.0001 0.8939
0.5689 < 0.0001 < 0.0001 0.5703 0.0290 < 0.0001 0.9161
0.5213 0.0998 < 0.0001 0.2937 0.7550 0.2428 0.9495
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BW (g)
BODY COMPOSITION AND BREEDER MANAGEMENT
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Table 6. Age of first egg and total egg production of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Age at first egg (wk)
Eggs per hen housed
Average egg weight (g)
HBW SBW LBW
26.1 26.0 26.4
173.4 175.5 165.3
65.5 64.4 64.4
330 360 390 420 450 480 SEM
26.1 26.3 25.9 26.4 25.9 26.3 0.27
173.4 184.3 173.9 185.7 180.3 184.6 6.78
64.5 66.2 64.2 65.1 64.5 64.1 0.89
Growth curve Energy intake Growth curve × energy intake Quadratic (energy)
0.6420 0.7532 0.7563
0.5042 0.6331 0.0592
0.4367 0.3323 0.7981
N/A
0.0088
0.1732
the onset of lay and abdominal fatness were linearly related to BW. Renema et al. (2007) found that breeders photo-stimulated at 22 wk vs. 19 wk enter lay with more carcass fat but similar carcass protein. However, De Beer and Coon (2007) reported that carcass fat did not appear to be a limiting threshold for onset of sexual maturity. The concept of a protein threshold appears to be well supported in literature as well. Reports indicate that pullets enter lay at similar lean mass content, percentage ash and percentage carcass protein regardless of the degree of restriction (Soller et al., 1984). Sun et al. (2006) showed that at first egg total carcass protein was very similar for ad libitum and feed-restricted hens, indicating the importance of protein mass for sexual maturity. Several reports indicate uniform lean mass and protein content are required in feed-restricted birds for the onset of production and that fat content alone is not enough to initiate sexual maturity (Bornstein et al., 1984; Soller et al., 1984; Wilson et al., 1995; Renema et al., 1999; Sun et al., 2006; de Beer and Coon, 2007). Indeed, the results reported herein
support the concept of a protein threshold rather than a fat threshold. There was a relatively constant body protein (across target BW), i.e., no significant difference was observed at light stimulation (week 21) in the present study (Table 3), whereas body fat content significantly differed between growth curves to no effect on age of first egg, egg production, or egg weight. The coefficient of variation for lean mass throughout the entire production period was <12%. Though, given the small sample size for egg production data, the presence or absence of statistical difference should be taken with caution. A significant quadratic effect for energy intake was observed for egg production that may suggest main effect differences with a larger sample size. Ciacciariello and Gous (2005) found no difference in body composition between hens that had never laid, were poor layers or were good layers. Although much work remains to be done in this area, several recent studies highlight what may be driving a protein threshold. First, fat requirements for egg production during early lay appear to be met primarily through lipogenesis. Salas et al. (2017), using stable isotope tracers, found that deposition of palmitic acid into egg yolk during early lay was primarily through lipogenesis (through glucose) with limited amounts of fatty acids coming from feed and tissue. Salas et al. (2017) hypothesized that glucose generated through skeletal muscle breakdown, via gluconeogenic amino acids, served as building blocks for lipogenesis. Thus, fat deposition in the pullet transitioning into sexual maturity serves no direct “purpose.” Second, Ekmay et al. (2013) reported that breeders during early lay (26 wk old) have a significant increase in fractional breakdown rates compared with pre-lay (22 wk old) pullets and return to similar, though marginally greater, breakdown rates by peak production (31 wk old). This trend was also observed by Vignale et al. (2017) in parent stock broiler breeders, though the increase in fractional breakdown rates was greatest at peak production. Furthermore, Ekmay et al. (2014) showed that isotopically labeled lysine in the skeletal
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Figure 1. (A) Lean and (B) fat composition during the production period of broiler breeder hens reared to three different growth curves. HBW—heavy BW; SBW—standard BW; LBW—light BW.
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SUPPLEMENTARY DATA Supplementary data are available at Poultry Science online. Supplementary Table 1. Nutrient content (%) of diets fed during the rearing period. Diets were formulated and provided by Cobb-Vantress. Supplementary Figure 1. Body weight during the rearing period of test birds.
Supplementary Figure 2. Coefficient of variation for body weights of experimental birds during their rearing period.
REFERENCES Bornstein, S., I. Plavnik, and Y. Lev. 1984. Body weight and/or fatness as potential determinants of the onset of egg production in broiler breeder hens. Br. Poult. Sci. 25:323–341. Ciacciariello, M., and R. M. Gous. 2005. A comparison of the effects of feeding treatments and lighting on age at first egg and subsequent laying performance and carcase composition of broiler breeder hens. Br. Poult. Sci. 46:246–254. Cobb-Vantress. 2005. Cobb 500 Breeder Management Guide. Blueprint for Success. Cobb-Vantress, Siloam Springs, Arkansas. de Avila, V. S., A. M. Penz, Jr., P. S. Rosa, P. A. R. de Brum, A. L. Guidoni, and M. C. Ledur. 2003. Influence of feeding time on sexual maturity and carcass composition in female broiler breeders. Rev. Bras. Cienc. Avic. 5:189–196. De Beer, M., and C. N. Coon. 2007. The effect of different feed restriction programs on reproductive performance, efficiency, frame size, and uniformity in broiler breeder hens. Poult. Sci. 86:1927– 1939. De Jong, I. C., A. Sander Van Voorst, D. A. Ehlhardt, and H. J. Blokhuis. 2002. Effects of restricted feeding on physiological stress parameters in growing broiler breeders. Br. Poult. Sci. 43:157– 168. Ekmay, R. D., C. Salas, J. England, S. Cerrate, and C. N. Coon. 2013. The effects of age, energy and protein intake on protein turnover and the expression of proteolysis-related genes in the broiler breeder hen. Comp. Biochem. Physiol. B: Biochem. Mol. Biol. 164:38–43. Ekmay, R. D., C. Salas, J. England, S. Cerrate, and C. N. Coon. 2014. Lysine partitioning in broiler breeders is not affected by energy or protein intake when fed at current industry levels. Poult. Sci. 93:1737–1744 Hocking, P. M. 2004. Roles of body weight and feed intake in ovarian follicular dynamics in broiler breeders at the onset of lay and after a forced molt. Poult. Sci. 83:2044–2050. Melnychuk, V. L., J. D. Kirby, Y. K. Kirby, D. A. Emmerson, and N. B. Anthony. 2004. Effect of strain, feed allocation program, and age at photostimulation on reproductive development and carcass characteristics of broiler breeder hens. Poult. Sci. 83:1861–1867. Pearson, R. A., and K. M. Herron. 1981. Effects of energy and protein allowances during lay on the reproductive performance of broiler breeder hens. Br. Poult. Sci. 22:227–239. Renema, R. A., F. E. Robinson, and M. J. Zuidhof. 2007. Reproductive efficiency and metabolism of female broiler breeders as affected by genotype, feed allocation, and age at photostimulation. 2. Sexual maturation. Poult. Sci. 86:2267–2277. Renema, R. A., F. E. Robinson, M. Newcombe, and R. I. McKay. 1999. Effects of body weight and feed allocation during sexual maturation in broiler breeder hens. 1. Growth and carcass characteristics. Poult. Sci. 78:619–628. Robinson, F. E., N. A. Robinson, and R. T. Hardin. 1995. The effects of 20-week body weight and feed allocation during early lay on female broiler breeders. J. Appl. Poult. Res. 4:203–210. Robinson, F. E., and N. A. Robinson. 1991. Reproductive performance, growth and body composition of broiler breeder hens differing in body weight at 21 weeks of age. Can. J. Anim. Sci. 71:1233–1239. Romero, L. F., M. J. Zuidhof, R. A. Renema, F. E. Robinson, and A. Naeima. 2009. Nonlinear mixed models to study metabolizable energy utilization in broiler breeder hens. Poult. Sci. 88:1310– 1320. Salas, C., R. D. Ekmay, J. England, S. Cerrate, and C. N. Coon. 2012. Determination of chicken body composition measured by dual energy x-ray absorptiometry. Int. J. Poult. Sci. 11: 462–468. Salas, C., R. D. Ekmay, J. A. England, S. Cerrate, and C. N. Coon. 2017. Mechanisms of lipid mobilization towards egg formation in broiler breeder hens using stable isotopes. Poult. Sci. 96:383– 387.
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muscle of 26 wk old breeders was a major source of lysine for early egg production. These results highlight a reason behind minimum body protein content before the onset of sexual maturity. It has been reported that differences in live BW and composition of older hens can be attributed to nutritional factors (Pearson and Herron, 1981; Spratt and Leeson, 1987a,b) and that body composition is a function of level of feed allocation and egg production rate during the latter part of the laying period (Robinson et al., 1995). Present results show that caloric intake had a significant effect on body composition, primarily to fat deposition, during the production period. A greater level of regulation is apparent to lean mass content, however, from 30 to 55 wk of age. The observed regulation may be due to the mobilization of body protein reported by Ekmay et al. (2013, 2014). Changes in BW can largely be attributed to increases in fat deposition that occurs after sexual maturity, consistent with the results of Salas et al. (2017) and Vignale et al. (2017). It is only after 55 wk of age does one observe a decrease in fat content and an increase in lean mass content. These results suggest that fat (energy) is not limiting during peak egg production. Further, the increase in lean mass towards the latter stages of egg production may cause an increase in the requirement for energy and result in a need for more energy to cope with the higher energy requirement for maintenance, for lean mass production, and continued egg production. Similarly, Pearson and Herron (1981) indicated that energy intake restriction after peak reduces BW and carcass fat. Sun et al. (2006) and de Beer and Coon (2007) have also indicated that during production, as hen age increases, carcass protein decreases and fat content increases. Avila et al. (2003) found a decrease in CP as the birds’ age. Results of the present study suggest the importance of carcass protein status. BW status at sexual maturity had a significant impact on carcass composition. Further, the energy intakes evaluated in the present study did not impact carcass protein but had pronounced effects on carcass fat. The results of these studies show age dependent effects to body composition that occur during the production period of breeders and further evaluation is needed in this area to determine if this shift is due to physiological processes that are affecting hens’ tissue deposition and mobilization.
BODY COMPOSITION AND BREEDER MANAGEMENT
Sun, J. M., M. P. Richards, R. W. Rosebrough, C. M. Ashwell, J. P. McMurtry, and C. N. Coon. 2006. The relationship of body composition, feed intake, and metabolic hormones for broiler breeder females. Poult. Sci. 85:1173–1184. Vignale, K., J. V. Caldas, J. A. England, N. Boonsinchai, P. Sodsee, M. Putsakum, E. D. Pollock, S. Dridi, and C. N. Coon. 2017. The effect of four different feeding regimens from rearing period to sexual maturity on breast muscle protein turnover in broiler breeder parent stock. Poult. Sci. 96:1219–1227. Wilson, J. L., F. E. Robinson, N. A. Renema, and R. T. Hardin. 1995. Effects of feed allocation on female broiler breeders. J. Appl. Poult. Res. 4:193–202.
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Savory, C. J., and L. Kostal. 1996. Temporal patterning of oral stereotypies in restricted-fed fowls: 1. Investigations with a single daily meal. Int. J. Comp. Psychol. 9:117–139. Soller, M., Y. Eitan, and T. Brody. 1984. Effect of diet and early quantitative feed restriction on the minimum weight requirement for onset of sexual maturity in white rock broiler breeders. Poult. Sci. 63:1255–1261. Spratt, R. S., and S. Leeson. 1987a. Broiler breeder performance in response to diet protein and energy. Poult. Sci. 66:683–693. Spratt, R. S., and S. Leeson. 1987b. Effect of protein and energy intake of broiler breeder hens on performance of broiler chicken offspring. Poult. Sci. 66:1489–1494.
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Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701 nificantly, greater (P < 0.05) amounts of fat mass and lower amounts of lean mass were evident at the beginning of the production period for HBW hens compared with SBW and LBW hens. Higher levels of energy intake also affected body composition. Namely, fat deposition was greatest throughout the production period in hens consuming 480 kcal/d at peak intake (P < 0.05). Critically, fluctuations to lean and fat mass throughout the production period are suggestive of underlying regulatory processes. Specifically, hens appears to maintain consistent lean mass throughout the production period with a coefficient of variation of <12% across all birds. The results of this study provide important BB body composition information from management and nutrition studies that showed the dynamics of body composition change during the production period.
ABSTRACT A study was conducted to determine the effect of different feeding programs and energy intakes on the body composition of broiler breeders (BB) from 22 wk of age to 65 wk of age. Cobb 500 BB that had been reared using three growth curves: (1) the control group followed Cobb 500 guidelines (SBW) for target body weights (BW), (2) the second group target BW was 20% heavier (HBW) than the SBW group, and (3) the third group target BW was 20% lighter (LBW) than the SBW group. At 21 wk of age, pullets from each growth curve were assigned to be fed one of six treatments. Diets were formulated and allocated to provide 330, 360, 390, 420, 450, or 480 kcal ME/hen/d and 24 g protein/hen/d, at peak intake. Body composition (lean mass, fat mass, and mineral content) was measured by dual-energy x-ray absorptiometry throughout the production period. Sig-
Key words: body composition, pullet, breeder hen, dual energy x-ray absorptiometry, energy intake 2018 Poultry Science 0:1–7 http://dx.doi.org/10.3382/ps/pey377
INTRODUCTION
tance of carcass protein and fat as an influencing factor is increasing (Bornstein et al., 1984; Renema et al., 1999; Hocking, 2004; Melnychuk et al., 2004; De Beer and Coon, 2007; Romero et al., 2009a). Low BW tend to delay the start of lay and lay fewer eggs than medium or heavier BW hens (Robinson and Robinson, 1991). The objective of the study was to evaluate the effect of different feeding programs on the body composition profile of broiler breeder hens during the production cycle using dual energy x-ray absorptiometry (DEXA).
Feed restriction is a necessary tool to manage excessive body weight (BW) gain that may result in adverse effects on reproduction in broiler breeders. The daily intake for broiler breeder pullets may decrease by up to one-third of the normal feed intake of broilers of the same age fed ad libitum or half in birds of the same weight fed ad libitum (Savory and Kostal, 1996; De Jong et al., 2002). The extent of feed restriction is often dictated by recommended target BW throughout the rearing period. Knowledge of body composition and the changes that occur during the life cycle of current broiler breeder strains is important to understand how feeding practices and dietary nutrients might need to be adjusted to supply nutrients appropriate for the stage in growth, sexual maturation and level of egg production. Many report the importance of BW as a determinant for the onset of sexual maturity, though the potential impor-
MATERIALS AND METHODS The study complied with the provisions of the University of Arkansas Institutional Animal Care and Use Committee (Protocol no. 0,9025) as specified by the Animal and Plant Health Inspection Service, United States Department of Agriculture in 9 CFR Part 1(1– 91) for use of poultry in research.
Experimental Design
C 2018 Poultry Science Association Inc. Received February 19, 2018. Accepted October 17, 2018. 1 Corresponding author: [email protected]
One hundred and forty-four pullets of 21 wk of age were assigned to 1 of 6 experimental diets. This 1
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C. Salas, R. D. Ekmay, J. England, S. Cerrate, and C. N. Coon1
2
SALAS ET AL. Table 1. Composition (%) and nutrient content of diets fed during the production period. Diet 1
Diet 2
Diet 3
Diet 4
Diet 5
Diet 6
Corn Soybean meal Limestone Wheat middling Dicalcium phosphate Salt Sodium bicarbonate DL-methionine 98.5% Fat Vitamin premix1 Choline chloride Trace mineral mix2 Copper sulfate L-lysine Selenium premix Ethoxyquin Total Nutrient CP % (calculated) CP % (analyzed) ME, kcal/kg (calculated) AMEn kcal/kg (analyzed)3 Calcium % Non-phytate P % Total P % Lysine % Methionine % Methionine + Cystine %
44.23 34.62 10.37 2.50 1.42 0.34 0.20 0.35 5.55 0.20 0.08 0.05 0.05 – 0.02 0.02 100
51.26 29.99 9.58 2.50 1.27 0.34 0.20 0.31 4.14 0.18 0.09 0.05 0.05 0.01 0.02 0.02 100
57.44 25.91 8.88 2.50 1.14 0.34 0.20 0.27 2.89 0.17 0.10 0.05 0.05 0.01 0.02 0.02 100
62.38 22.65 8.32 2.50 1.03 0.34 0.20 0.24 1.90 0.16 0.11 0.06 0.05 0.02 0.02 0.02 100
66.92 19.66 7.81 2.50 0.94 0.34 0.20 0.21 0.99 0.15 0.11 0.06 0.05 0.03 0.02 0.02 100
71.02 16.96 7.35 2.50 0.85 0.34 0.20 0.19 0.16 0.14 0.12 0.06 0.05 0.03 0.02 0.02 100
20.8 20.8 2860 2932 4.16 0.40 0.63 1.16 0.67 1.01
19.1 19.2 2860 2894 3.83 0.37 0.59 1.04 0.61 0.93
17.6 17.9 2860 2951 3.54 0.34 0.55 0.94 0.56 0.86
16.4 16.2 2860 2849 3.31 0.32 0.52 0.86 0.51 0.80
15.3 15.7 2860 2952 3.09 0.30 0.49 0.78 0.48 0.75
14.3 14.4 2860 2820 2.9 0.28 0.47 0.71 0.44 0.7
1 Vitamin mix provided per kg of mix: vitamin A (vitamin acetate), 4500,000 IU; vitamin D3, 2250,056 ICU; vitamin E, 22,500 IU; niacin, 25,313 mg; D-pantothenic acid, 11,250 mg; riboflavin, 6750 mg; thiamine, 1125 mg; menadione, 1125 mg; folic acid, 1125 mg; biotin, 113 mg; vitamin B12, 10 mg; pyridoxine, 2250 mg. 2 Trace mineral mix provided per kg of mix: manganese (MnSO4.H2O), 10%; zinc (ZnSO4.7H2O), 10%; iron (FeSO4.7H2O), 5%; copper CuSO4.5H2O), 1%; iodine (Ca(IO3)2.H2O), 1000 ppm; magnesium (magnesium oxide), 2.70%. 3 Average AMEn of the diets throughout the experimental period. Standard error was 31.6 kcal.
resulted in a 3 (BW) × 6 (peak kcal ME intakes) factorial arrangement (Tables 2 and 3) with a total of 18 treatments during the production period. Each bird was housed in individual cages (47 cm × 30.5 cm × 47 cm) and each cage was equipped with a nippletype drinker and individual feeder. Production performance was recorded daily during the trial. Egg weights were recorded every 5 wk by collecting and weighing all egg laid during the week. Diets (Table 1) were formulated to contain 2860 kcal ME/kg and six different amounts of crude protein (14.3%–20.8% CP). Feed allocation (Table 2) was based on egg production, rather than BW, and designed to provide peak ME kcal intakes of 330, 360, 390, 420, 450, or 480 kcal ME/hen/d and 24 g of ideal protein/hen/d at peak production. This was achieved by adjusting the peak feed intake per hen. The BW at 21 wk of age were a control group (SBW) that had been reared to Cobb 500 target BW and two other groups that were reared to 20% heavier (HBW) or 20% lighter (LBW) BW compared to the SBW group, respectively (Table 3), but otherwise followed Cobb Broiler Breeder Management Guide (2005) recommendations. Birds were light-stimulated at 21 wk, the start of the experimental period. Diet analysis and related rearing information may be found in Supplementary Tables 1 and 2.
Body Composition Body composition of eight hens per treatment (144 total) was measured at 21, 30, 35, 46, 55, and 65 wk of age during the production period using a DEXA scanner (GE Lunar Prodigy, Encore software version 12.20.023) as previously described by Salas et al. (2012) except bids were scanned live. Briefly, birds were restrained and placed prone, un-anesthetized on the DEXA scanner and scanned utilizing the small animal software module (Lunar Prodigy from GE, encore software version 12.20.023). Defining the whole bird as the region of interest, the DEXA provided measurements in grams of bone mineral content (BMC), grams fat content and grams lean mass for each bird. The sum of the DEXA measurements was assumed to be grams total body mass. Results were evaluated using regression equations previously developed and validated using DEXA-reported measurements and actual chemical analysis of the body composition (Salas et al., 2012).
Statistical Analysis The trial was a completely randomized design with a factorial treatment structure. Growth curve, energy intake, and age were considered fixed effects for body composition data. Data were analyzed as repeated measures using the analysis of variance procedure of
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Ingredient
3
BODY COMPOSITION AND BREEDER MANAGEMENT Table 2. Feed program for broiler breeder hens during the production period to obtain the energy intake at peak. 21 wk
23 wk
5%5
37%5
53%5
61%5
Peak
35 wk
40 wk
46 wk
50 wk
56 wk
60 wk
106 22 302
115 24 328
115 24 328
115 24 329
115 24 329
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
115 24 330
106 20 302
115 22 328
115 22 330
120 23 342
124 24 353
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
126 24 360
106 19 302
115 20 328
116 20 331
124 22 356
132 23 377
136 24 390
136 24 390
136 24 389
136 24 389
136 24 389
136 24 389
136 24 389
136 24 389
106 17 302
115 19 328
116 19 333
129 21 369
140 23 401
147 24 419
147 24 419
144 24 413
139 23 396
136 22 388
136 22 388
136 22 388
136 22 388
106 16 302
115 18 328
117 18 334
134 20 383
149 23 425
157 24 449
157 24 449
155 24 443
149 23 426
144 22 411
140 21 400
136 21 390
136 21 389
106 15 302
115 16 328
117 17 336
139 20 396
157 22 449
168 24 479
168 24 479
165 24 473
159 23 456
155 22 443
151 22 433
146 21 417
142 20 407
1
1
330 kcal fed diet 1, 360 kcal fed diet 2, 390 kcal fed diet 3, 420 kcal fed diet 4, 450 kcal fed diet 5, 480 kcal fed diet 6. g feed/d—grams feed per bird per day. 3 g CP/d—grams crude protein per bird per day. 4 kcal/d—calculated kcal ME per bird per day. 5 Percent production reached at which time feed amounts were increased. 2
JMP 8.2 (SAS Institute Inc., Cary, North Carolina). Age was not considered into the statistical model for egg production data, except for egg weight data that were analyzed as repeated measures. Each individual hen was considered the experimental unit. When there were significant treatment effects, means were separated using Student’s t-test. Post-hoc trend contrasts were performed on egg production data to determine line shape across energy intake treatments after visual inspection of the data. The level of significance is reported at P < 0.05.
RESULTS Analyzed daily energy intake for each diet was within 3% of target daily energy intake. No significant interactions effects were observed between growth curve, energy, and age, or growth curve by energy intake for body composition components at any age (Tables 3, 4, and 5). When body composition components were expressed on an absolute weight basis (grams), significant interaction effects were observed between growth curve and time, and energy intake and age, respectively, for fat mass but not lean mass (Tables 4 and 5). A significant energy intake by time effect was observed for BMC when expressed on an absolute weight basis. When body composition components were expressed on a percentage basis, significant interaction effects were observed between growth curve and time, as well as energy intake and time, for fat mass and lean mass, but not BMC.
The significant increase in fat mass (g) in HBW breeders carried through into production through 35 wk of age (Figure 1). However, when viewed on a percentage basis, the initial fat mass increase in HBW breeders disappeared by week 30. Logically, energy intake had a significant effect on fat mass with hens consuming the higher energy intake, e.g., 480 kcal/d, having greater fat mass on both an absolute weight basis and percentage basis at all time periods. Energy intake also impacted lean mass deposition; however, the deposition trends were time specific. At 35 wk of age, hens consuming higher energy intakes showed greater lean mass deposition, but the opposite was observed at other time periods. BMC was significantly greater among hens consuming greater energy intakes but only when BMC was expressed on an absolute weight. No significant (P = 0.0592) growth curve by energy intake effect was observed for egg production, and no significant main effects were observed (Table 6). However, a significant quadratic fit was observed with energy intake, with peak production predicted to be between 390 kcal/d and 420 kcal/d. No significant effects were observed for age of first egg or egg weight.
DISCUSSION There is evidence to suggest that carcass fat and a fat pool threshold are important for the onset of production (Bornstein et al., 1984; Hocking, 2004). Hocking (2004) reported that the number of normal yellow follicles at
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330 kcal g feed/d2 g CP/d3 kcal/d4 360 kcal g feed d g CP/d kcal/d 390 kcal g feed/d g CP/d kcal/d 420 kcal g feed/d g CP/d kcal/d 450 kcal g feed/d g CP/d kcal/d 480 kcal g feed/d g CP/d kcal/d
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SALAS ET AL.
Table 3. Body weight and composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Growth curve
Energy intake (kcal ME/d)
HBW
SBW
LBW
SEM
330
360
390
420
450
480
SEM
21 30 35 46 55 65
wk wk wk wk wk wk
2528 3849a 4052a 4270a 4307a 4195a
2194 3675b 3900b 4172a 4250a 4168a
1773 3482c 3675c 3981b 4104b 4005b
123.9 30.7 32.9 42.7 49.5 56.7
N/A 3403c 3444e 3590e 3684d 3641d
N/A 3515c 3655d 3883d 3989c 3940c
N/A 3673b 3861c 4175c 4278b 4240b
N/A 3680b 3932c 4165c 4296b 4217b
N/A 3813a 4083b 4359b 4382b 4224b
N/A 3927a 4279a 4673a 4692a 4474a
N/A 43.3 46.5 60.4 70.0 80.2
Fat (g)
21 30 35 46 55 65 21 30 35 46 55 65 21 30 35 46 55 65
wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk wk
412a 804a 962a 1216 1083 830 2683 2929 2988 2904 3087 3244 70 116 128 150 147 123
188b 736b 872b 1225 1185 880 2427 2826 2909 2796 2908 3162 69 112 118 149 156 127
185b 710b 854b 1207 1083 827 1967 2663 2706 2630 2861 3055 54 109 114 142 145 122
36.9 21.4 33.2 42.5 49.7 42.4 93.8 32.7 39.7 44.5 44.6 44.7 2.9 2.9 3.3 4.9 5.5 5.0
N/A 635d 609d 828d 664d 559d N/A 2660 2737 2642 2880 2976 N/A 107 98d 119c 116d 106c
N/A 697c,d 829c 1072c 981c 697c,d N/A 2709 2770 2673 2871 3135 N/A 109 106c,d 138b,c 137c,d 108c
N/A 719b-d 875b,c 1220b,c 1253a,b 943a,b N/A 2846 2890 2813 2881 3170 N/A 108 118b,c 142b 161a,b 131a,b
N/A 779b,c 954b,c 1248b 1112b,c 835b,c N/A 2789 2852 2760 3035 3263 N/A 111 126b 157a,b 148b,c 120b,c
N/A 797a,b 994a,b 1347b 1241b 950a,b N/A 2899 2958 2856 2982 3140 N/A 117 131a,b 156a,b 158a-c 133a,b
N/A 875a 1115a 1583a 1452a 1091a N/A 2932 3023 2920 3060 3239 N/A 121 140a 169a 174a 144a
N/A 30.3 47.0 60.1 70.3 59.9 N/A 46.2 56.1 63.0 63.0 63.3 N/A 3.9 4.7 6.9 7.8 7.1
Lean (g)
BMC (g)
LBW = light BW, SBW = standard BW, HBW = heavy BW, N/A = not applicable Means within the same row that do not share a letter differ significantly (P < 0.05).
Table 4. Percent body composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Growth curve
Energy intake (kcal ME/d)
HBW
SBW
LBW
SEM
330
360
390
420
450
480
SEM
% Fat
21 30 35 46 55 65
wk wk wk wk wk wk
12.8a 20.8 23.6 29.1 24.5 19.3
6.8b 20.0 22.2 29.1 27.5 20.8
8.2b 20.4 23.1 29.6 25.9 20.3
1.06 0.56 0.87 0.91 1.02 0.84
N/A 18.7c 17.6b 22.9c 17.9d 15.2d
N/A 19.9b,c 22.8a 27.6b,c 24.5c 17.6c,d
N/A 19.7b,c 22.7a 28.3b 29.1a,b 22.3a,b
N/A 21.1a,b 24.2a 32.0a,b 25.7b,c 19.6b,c
N/A 20.9a,b 24.4a 30.7a,b 27.9a-c 22.1a,b
N/A 22.3a 26.1a 33.9a 30.7a 23.9a
NA 0.79 1.23 1.29 1.45 1.19
% Lean
21 30 35 46 55 65 21 30 35 46 55 65
wk wk wk wk wk wk wk wk wk wk wk wk
85.0b 76.1 73.9 70.0 72.1 77.9 2.2 3.0 3.1 3.6 3.4 2.9
90.6a 77.0 74.7 67.4 68.8 76.2 2.6 3.1 3.0 3.6 3.7 3.0
89.4a 76.5 73.8 66.4 70.6 76.7 2.5 3.1 3.1 3.6 3.5 3.0
1.02 0.60 0.74 0.99 1.10 0.89 0.09 0.07 0.09 0.11 0.11 0.11
N/A 78.2a 79.5a 73.7a 78.9a 81.9 N/A 3.2 2.8 3.3 3.2 2.9
N/A 77.1a 75.6b 68.9a,b 73.0b 79.4 N/A 3.0 2.9 3.6 3.4 2.7
N/A 77.4a 74.2b,c 67.4b,c 67.1c,d 74.7 N/A 3.0 3.1 3.4 3.8 3.1
N/A 75.9a,b 72.6c,d 69.5a,b 70.8b,c 77.6 N/A 3.0 3.2 4.0 3.5 2.9
N/A 76.0a,b 72.4c,d 65.7b,c 68.5b-d 74.7 N/A 3.1 3.2 3.6 3.6 3.2
N/A 74.6b 70.6d 62.5c 65.6d 73.0 N/A 3.1 3.3 3.6 3.7 3.2
NA 0.85 1.05 1.40 1.55 1.26 NA 0.10 0.12 0.15 0.15 0.15
% BMC
HBW = heavy BW, SBW = standard BW, LBW = light BW, N/A = not applicable Means within the same row that do not share a letter differ significantly (P < 0.05).
Table 5. P values for body composition (measured with DEXA technology) of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production.
Growth curve Energy intake Age Growth curve × energy intake Growth curve × age Energy intake × age Growth curve × energy intake × age
Fat (g)
Lean (g)
BMC (g)
Fat (%)
Lean (%)
BMC (%)
0.3465 < 0.0001 < 0.0001 0.7490 0.0093 < 0.0001 0.9221
< 0.0001 0.0015 < 0.0001 0.0876 0.7357 0.6398 0.8032
0.1275 < 0.0001 < 0.0001 0.4018 0.4726 0.0353 0.9648
0.7706 < 0.0001 < 0.0001 0.6470 0.0124 < 0.0001 0.8939
0.5689 < 0.0001 < 0.0001 0.5703 0.0290 < 0.0001 0.9161
0.5213 0.0998 < 0.0001 0.2937 0.7550 0.2428 0.9495
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BW (g)
BODY COMPOSITION AND BREEDER MANAGEMENT
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Table 6. Age of first egg and total egg production of broiler breeder hens reared to three different growth curves and fed six different levels of energy at peak production. Age at first egg (wk)
Eggs per hen housed
Average egg weight (g)
HBW SBW LBW
26.1 26.0 26.4
173.4 175.5 165.3
65.5 64.4 64.4
330 360 390 420 450 480 SEM
26.1 26.3 25.9 26.4 25.9 26.3 0.27
173.4 184.3 173.9 185.7 180.3 184.6 6.78
64.5 66.2 64.2 65.1 64.5 64.1 0.89
Growth curve Energy intake Growth curve × energy intake Quadratic (energy)
0.6420 0.7532 0.7563
0.5042 0.6331 0.0592
0.4367 0.3323 0.7981
N/A
0.0088
0.1732
the onset of lay and abdominal fatness were linearly related to BW. Renema et al. (2007) found that breeders photo-stimulated at 22 wk vs. 19 wk enter lay with more carcass fat but similar carcass protein. However, De Beer and Coon (2007) reported that carcass fat did not appear to be a limiting threshold for onset of sexual maturity. The concept of a protein threshold appears to be well supported in literature as well. Reports indicate that pullets enter lay at similar lean mass content, percentage ash and percentage carcass protein regardless of the degree of restriction (Soller et al., 1984). Sun et al. (2006) showed that at first egg total carcass protein was very similar for ad libitum and feed-restricted hens, indicating the importance of protein mass for sexual maturity. Several reports indicate uniform lean mass and protein content are required in feed-restricted birds for the onset of production and that fat content alone is not enough to initiate sexual maturity (Bornstein et al., 1984; Soller et al., 1984; Wilson et al., 1995; Renema et al., 1999; Sun et al., 2006; de Beer and Coon, 2007). Indeed, the results reported herein
support the concept of a protein threshold rather than a fat threshold. There was a relatively constant body protein (across target BW), i.e., no significant difference was observed at light stimulation (week 21) in the present study (Table 3), whereas body fat content significantly differed between growth curves to no effect on age of first egg, egg production, or egg weight. The coefficient of variation for lean mass throughout the entire production period was <12%. Though, given the small sample size for egg production data, the presence or absence of statistical difference should be taken with caution. A significant quadratic effect for energy intake was observed for egg production that may suggest main effect differences with a larger sample size. Ciacciariello and Gous (2005) found no difference in body composition between hens that had never laid, were poor layers or were good layers. Although much work remains to be done in this area, several recent studies highlight what may be driving a protein threshold. First, fat requirements for egg production during early lay appear to be met primarily through lipogenesis. Salas et al. (2017), using stable isotope tracers, found that deposition of palmitic acid into egg yolk during early lay was primarily through lipogenesis (through glucose) with limited amounts of fatty acids coming from feed and tissue. Salas et al. (2017) hypothesized that glucose generated through skeletal muscle breakdown, via gluconeogenic amino acids, served as building blocks for lipogenesis. Thus, fat deposition in the pullet transitioning into sexual maturity serves no direct “purpose.” Second, Ekmay et al. (2013) reported that breeders during early lay (26 wk old) have a significant increase in fractional breakdown rates compared with pre-lay (22 wk old) pullets and return to similar, though marginally greater, breakdown rates by peak production (31 wk old). This trend was also observed by Vignale et al. (2017) in parent stock broiler breeders, though the increase in fractional breakdown rates was greatest at peak production. Furthermore, Ekmay et al. (2014) showed that isotopically labeled lysine in the skeletal
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Figure 1. (A) Lean and (B) fat composition during the production period of broiler breeder hens reared to three different growth curves. HBW—heavy BW; SBW—standard BW; LBW—light BW.
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SALAS ET AL.
SUPPLEMENTARY DATA Supplementary data are available at Poultry Science online. Supplementary Table 1. Nutrient content (%) of diets fed during the rearing period. Diets were formulated and provided by Cobb-Vantress. Supplementary Figure 1. Body weight during the rearing period of test birds.
Supplementary Figure 2. Coefficient of variation for body weights of experimental birds during their rearing period.
REFERENCES Bornstein, S., I. Plavnik, and Y. Lev. 1984. Body weight and/or fatness as potential determinants of the onset of egg production in broiler breeder hens. Br. Poult. Sci. 25:323–341. Ciacciariello, M., and R. M. Gous. 2005. A comparison of the effects of feeding treatments and lighting on age at first egg and subsequent laying performance and carcase composition of broiler breeder hens. Br. Poult. Sci. 46:246–254. Cobb-Vantress. 2005. Cobb 500 Breeder Management Guide. Blueprint for Success. Cobb-Vantress, Siloam Springs, Arkansas. de Avila, V. S., A. M. Penz, Jr., P. S. Rosa, P. A. R. de Brum, A. L. Guidoni, and M. C. Ledur. 2003. Influence of feeding time on sexual maturity and carcass composition in female broiler breeders. Rev. Bras. Cienc. Avic. 5:189–196. De Beer, M., and C. N. Coon. 2007. The effect of different feed restriction programs on reproductive performance, efficiency, frame size, and uniformity in broiler breeder hens. Poult. Sci. 86:1927– 1939. De Jong, I. C., A. Sander Van Voorst, D. A. Ehlhardt, and H. J. Blokhuis. 2002. Effects of restricted feeding on physiological stress parameters in growing broiler breeders. Br. Poult. Sci. 43:157– 168. Ekmay, R. D., C. Salas, J. England, S. Cerrate, and C. N. Coon. 2013. The effects of age, energy and protein intake on protein turnover and the expression of proteolysis-related genes in the broiler breeder hen. Comp. Biochem. Physiol. B: Biochem. Mol. Biol. 164:38–43. Ekmay, R. D., C. Salas, J. England, S. Cerrate, and C. N. Coon. 2014. Lysine partitioning in broiler breeders is not affected by energy or protein intake when fed at current industry levels. Poult. Sci. 93:1737–1744 Hocking, P. M. 2004. Roles of body weight and feed intake in ovarian follicular dynamics in broiler breeders at the onset of lay and after a forced molt. Poult. Sci. 83:2044–2050. Melnychuk, V. L., J. D. Kirby, Y. K. Kirby, D. A. Emmerson, and N. B. Anthony. 2004. Effect of strain, feed allocation program, and age at photostimulation on reproductive development and carcass characteristics of broiler breeder hens. Poult. Sci. 83:1861–1867. Pearson, R. A., and K. M. Herron. 1981. Effects of energy and protein allowances during lay on the reproductive performance of broiler breeder hens. Br. Poult. Sci. 22:227–239. Renema, R. A., F. E. Robinson, and M. J. Zuidhof. 2007. Reproductive efficiency and metabolism of female broiler breeders as affected by genotype, feed allocation, and age at photostimulation. 2. Sexual maturation. Poult. Sci. 86:2267–2277. Renema, R. A., F. E. Robinson, M. Newcombe, and R. I. McKay. 1999. Effects of body weight and feed allocation during sexual maturation in broiler breeder hens. 1. Growth and carcass characteristics. Poult. Sci. 78:619–628. Robinson, F. E., N. A. Robinson, and R. T. Hardin. 1995. The effects of 20-week body weight and feed allocation during early lay on female broiler breeders. J. Appl. Poult. Res. 4:203–210. Robinson, F. E., and N. A. Robinson. 1991. Reproductive performance, growth and body composition of broiler breeder hens differing in body weight at 21 weeks of age. Can. J. Anim. Sci. 71:1233–1239. Romero, L. F., M. J. Zuidhof, R. A. Renema, F. E. Robinson, and A. Naeima. 2009. Nonlinear mixed models to study metabolizable energy utilization in broiler breeder hens. Poult. Sci. 88:1310– 1320. Salas, C., R. D. Ekmay, J. England, S. Cerrate, and C. N. Coon. 2012. Determination of chicken body composition measured by dual energy x-ray absorptiometry. Int. J. Poult. Sci. 11: 462–468. Salas, C., R. D. Ekmay, J. A. England, S. Cerrate, and C. N. Coon. 2017. Mechanisms of lipid mobilization towards egg formation in broiler breeder hens using stable isotopes. Poult. Sci. 96:383– 387.
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muscle of 26 wk old breeders was a major source of lysine for early egg production. These results highlight a reason behind minimum body protein content before the onset of sexual maturity. It has been reported that differences in live BW and composition of older hens can be attributed to nutritional factors (Pearson and Herron, 1981; Spratt and Leeson, 1987a,b) and that body composition is a function of level of feed allocation and egg production rate during the latter part of the laying period (Robinson et al., 1995). Present results show that caloric intake had a significant effect on body composition, primarily to fat deposition, during the production period. A greater level of regulation is apparent to lean mass content, however, from 30 to 55 wk of age. The observed regulation may be due to the mobilization of body protein reported by Ekmay et al. (2013, 2014). Changes in BW can largely be attributed to increases in fat deposition that occurs after sexual maturity, consistent with the results of Salas et al. (2017) and Vignale et al. (2017). It is only after 55 wk of age does one observe a decrease in fat content and an increase in lean mass content. These results suggest that fat (energy) is not limiting during peak egg production. Further, the increase in lean mass towards the latter stages of egg production may cause an increase in the requirement for energy and result in a need for more energy to cope with the higher energy requirement for maintenance, for lean mass production, and continued egg production. Similarly, Pearson and Herron (1981) indicated that energy intake restriction after peak reduces BW and carcass fat. Sun et al. (2006) and de Beer and Coon (2007) have also indicated that during production, as hen age increases, carcass protein decreases and fat content increases. Avila et al. (2003) found a decrease in CP as the birds’ age. Results of the present study suggest the importance of carcass protein status. BW status at sexual maturity had a significant impact on carcass composition. Further, the energy intakes evaluated in the present study did not impact carcass protein but had pronounced effects on carcass fat. The results of these studies show age dependent effects to body composition that occur during the production period of breeders and further evaluation is needed in this area to determine if this shift is due to physiological processes that are affecting hens’ tissue deposition and mobilization.
BODY COMPOSITION AND BREEDER MANAGEMENT
Sun, J. M., M. P. Richards, R. W. Rosebrough, C. M. Ashwell, J. P. McMurtry, and C. N. Coon. 2006. The relationship of body composition, feed intake, and metabolic hormones for broiler breeder females. Poult. Sci. 85:1173–1184. Vignale, K., J. V. Caldas, J. A. England, N. Boonsinchai, P. Sodsee, M. Putsakum, E. D. Pollock, S. Dridi, and C. N. Coon. 2017. The effect of four different feeding regimens from rearing period to sexual maturity on breast muscle protein turnover in broiler breeder parent stock. Poult. Sci. 96:1219–1227. Wilson, J. L., F. E. Robinson, N. A. Renema, and R. T. Hardin. 1995. Effects of feed allocation on female broiler breeders. J. Appl. Poult. Res. 4:193–202.
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Savory, C. J., and L. Kostal. 1996. Temporal patterning of oral stereotypies in restricted-fed fowls: 1. Investigations with a single daily meal. Int. J. Comp. Psychol. 9:117–139. Soller, M., Y. Eitan, and T. Brody. 1984. Effect of diet and early quantitative feed restriction on the minimum weight requirement for onset of sexual maturity in white rock broiler breeders. Poult. Sci. 63:1255–1261. Spratt, R. S., and S. Leeson. 1987a. Broiler breeder performance in response to diet protein and energy. Poult. Sci. 66:683–693. Spratt, R. S., and S. Leeson. 1987b. Effect of protein and energy intake of broiler breeder hens on performance of broiler chicken offspring. Poult. Sci. 66:1489–1494.
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