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Effects of dietary metabolizable energy levels and beak trimming on the performance, egg quality, and economic viability of layers
Effects of dietary metabolizable energy levels and beak trimming on the performance, egg quality, and economic viability of layers
∗
Department of Animal Nutrition and Production, University of S˜ ao Paulo (FMVZ-USP), Pirassununga, 13635900, Brazil; † School of Veterinary Medicine and Animal Science, University of S˜ ao Paulo (FMVZ- USP), ao Paulo (FZEA-USP), S˜ ao Paulo, 05508270, Brazil; and ‡ Department of Animal Science, University of S˜ Pirassununga, 13635900,Brazil were analyzed. Egg production was positively influenced by dietary ME levels. Feed intake (FI), feed conversion ratio (FCR), egg weight, albumen height, Haugh units, and eggshell strength were positively influenced by increasing dietary ME levels. Hens beaktrimmed once presented higher feed intake and worse FCR than those beak-trimmed twice. Beak trimming did not affect egg production, egg weight, albumen height, Haugh units, and eggshell strength. Production costs increased as dietary ME levels increased. Higher production cost was determined for hens beaktrimmed once than for those beak-trimmed twice. Total revenue was not influenced by the treatments. Gross margin was linearly decreased as dietary ME levels increased and was lower when hens were beak-trimmed once. Increasing dietary ME levels and beak trimming hens once reduce the economic viability of egg production.
ABSTRACT Considering the market availability of new commercial layer strains with distinct characteristics and behaviors, studies to update their nutritional requirements and to evaluate the need to adopt management practices, such as beak trimming, are needed. The objective of the present study was to evaluate the effects of dietary metabolizable energy (ME) levels and beak trimming on the live performance, egg quality, and economics of commercial layers. A total of 640 Novogen White layers were distributed according to a randomized experimental design in a 5 × 2 factorial arrangement (5 ME levels × 2 beak trimming treatments), totaling 10 treatments with 8 replicates of 8 hens each. The evaluated dietary ME levels were 2,600; 2,700; 2,800; 2,900; and 3,000 kcal/kg of feed. Layers were beak-trimmed once (7 days old) or twice (7 and 70 days old). Live performance and egg quality mesuraments and production economics
Key words: beak trimming, performance, metabolizable energy, economic viability 2019 Poultry Science 0:1–9 http://dx.doi.org/10.3382/ps/pez145
INTRODUCTION
body temperature, and synthesis of organic tissues. In addition, energy can be stored or directed to production functions, such as egg production (NRC, 1994). In laying hens, the amount of energy of the diet influences in parts the consumption of feed, which is also influenced by other factors, such as body weight, ambient temperature, photoperiod, among others. Therefore, its ratio to other dietary nutrients is extremely important. As metabolizable energy (ME) is negatively correlated with feed intake, the ratio between energy and other dietary nutrients in the diet should be carefully taken into account in diet formulation in order to provide adequate nutrient intake (Fischer et al., 1998). The research on the ME requirements of commercial layers has shown controversial results. For instance, literature reports both positive (Wu et al., 2007; Costa et al., 2009) and negative (Colvara et al., 2002; Junqueira et al., 2006; Almeida et al., 2012; Silva et al., 2012) influence of increasing dietary ME content
The nutritional requirements of commercial laying hens vary according to age, genetic strain, environmental conditions, management practices, dietary amino acid and energy levels, among other factors. Therefore, layers’ nutritional requirements need to be regularly evaluated and updated in order to formulate diets suitable for each production situation (Costa et al., 2004). Energy is the main nutritional component of commercial layer diets. Animals supply their energy requirements by oxidizing dietary carbohydrates, fats, proteins, and fibers. Energy is required for the maintenance of vital body functions, such as movement, regulation of C 2019 Poultry Science Association Inc. Received June 28, 2018. Accepted June 28, 2018. 1 Corresponding author: [email protected]
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Carlos A. Granghelli,∗,1 Maria F. C. Burbarelli ,∗ Karoline D. Lelis,† Paulo H. Pelissari,∗ Nat´ alia B. P. Utimi,‡ Brunna G. S. Leite,‡ Fabricia A. Roque,‡ Priscila S. Zorzetto,∗ Julio C. C. Balieiro,∗ L´ ucio F. Ara´ ujo,‡ and Cristiane S. S. Ara´ ujo∗
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GRANGHELLI ET AL.
MATERIALS AND METHODS Birds, Housing, and Experimental Diets The experimental protocol was approved by the Ethics Committee on the Use of Animals of the School of Veterinary Medicine and Animal Science of the University of S˜ ao Paulo under protocol n. 9176031014. During the rearing period (0 to 6 wk of age), 864 one-day-old Novogen White pullets were housed in battery cages (12 birds per cage). By the end of week 6, birds were transferred to development cages (10 birds per cage), where they remained until the end of the development phase (week 16). The management practices, lighting program, and feeding applied during the rearing and development periods followed the management guide of genetic company (Novogen, 2014). At the beginning of week 17, 640 hens were transferred to production cages (density of 562.5 cm2 per bird), located in a masonry shed with open sides with screens, and equipped with fans and foggers for temperature control. The metal cages measured 1.0 m × 0.45 m × 0.45 m and were arranged in a pyramidal system. Cages were equipped with nipple drinkers and trough feeders.
At 7 D of age, all hens were weighed and beaktrimmed, and only half of the birds (n = 432) were submitted to a second beak trimming at 70 D of age. In the first (7 D of age) and second (70 D of age) beak trimming, a moderate cut was used, 5 and 7 mm of the nostrils, respectively. The conventional beak trimming method, using hot blade, was applied. It was performed by the same trained employee, who was experienced in working with the evaluated genetic strain, and according to the directions of the equipment manufacturer (Lyon, 2007). Until week 19, all hens were fed a single diet. In week 20, chickens were individually weighed and distributed to cages according to body weight and beak-trimming treatments. Hens were evaluated for 28 wk (20 to 48 wk of age), divided into 7 cycles of 28 D each. The laying hens were distributed in a completely randomized design, in a 5 × 2 factorial experiment, with 5 levels of apparent ME in the diet (2,600; 2,700; 2,800; 2,900 and 3,000 kcal ME/kg of feed) and 2 beak trimming treatments (with or without beak trimming at 70 D of age), totaling 10 treatments with 8 replicates of 8 hens each. The effects of beak trimming once or twice and the interaction of dietary ME levels and beak trimming were analyzed. A basal diet based on corn and soybean meal, containing 2,800 kcal ME/kg, was formulated according to nutritional recommendations of Rostagno et al. (2011). The evaluated dietary ME levels were obtained by the replacement of the inert material (kaolin) by soybean oil. The experimental diets were isonutritional and are shown in Table 1. Hens were offered water and feed ad libitum, and the feed was distributed twice daily. A lighting program of 16 h of light was applied, as recommended by the genetic line manual (Novogen, 2014). The eggs were collected twice daily, and the total numbers of intact and defective eggs were recorded per replicate.
Evaluation of Live Performance and Egg Quality The live performance variables were evaluated per replicate at the end of each 28-D cycle. The following variables were determined: total egg production (EP) (total number of eggs produced divided by the average number of hens of each replicate, expressed as percentage of posture/hen/day), feed intake (FI) (amount of feed consumed per each replicate divided by the average number of hens, expressed in g/hen/day), egg mass (EM) (average egg weight of each replicate multiplied by egg production percentage, expressed in g/bird/day), feed conversion ratio (FCR) per dozen eggs produced (FCRDz) (obtained through the ratio of feed consumption and average percentage of eggs produced, multiplied by the dozen eggs, expressed in kg of feed/dozen eggs), and feed conversion ratio per egg
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on egg quality. The lack of consensus on the dietary ME recommendations for commercial laying hens may be attributed to the different growth rates, performance levels, and behavior of the current genetic lines. Therefore, it is critical to determine or to update the specific ME requirements of each genetic strain. Routine management practices also have a direct influence on egg production and quality. It has been demonstrated that management practices that cause stress, such as beak trimming, can impair bird welfare and egg production and quality (Janczak and Riber, 2015; Stadelman et al., 2017), which has led to questioning the real need of such practice (Oda et al., 2000). Beak trimming is an aggressive, painful, and stressful procedure for commercial layers (Oda et al., 2000). However, according to Hughes and Gentle (1995), it is required to reduce cannibalism, feather pecking, feed waste, and mortality on layer farms. It is recommended that beaks should be trimmed as little as possible (Janczak & Riber, 2015) and to be performed by a trained professional using the least aggressive method. However, hot blade is still the most frequent method applied. Considering that the need of such aggressive practice is controversial, and the emergence of new, more docile layer strains, the study of the influence these factors on egg production and quality may be useful. Moreover, as feed is one of the main cost of egg production, the influence of the energy requirements of modern commercial layers strains on feed intake should be re-evaluated. The objective of the present study was to evaluate the effects of dietary ME levels, beak trimming, and their interaction on the live performance, egg quality, and economics of commercial layers.
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ENERGY AND BEAK TRIMMING in LAYER HENS Table 1. Composition of the experimental diets. Diets Metabolizable energy levels (kcal/kg of feed)
AME. kcal/kg Crude Protein, % Ca % P% Na % Methionine + cystine % Lysine, % Methionine % Threonine % Linoleic Acid
2,600 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 0 4.6 0.40 100 2.600 16.020 3.900 0.291 0.218 0.617 0.719 0.391 0.535 1.325
2,700 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 1.15 3.45 0.40 100
2,800 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 2.30 2.30 0.40 100
2,900 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 3.45 1.15 0.40 100
Calculated composition, g/kg 2.700 2.800 2.900 16.020 16.020 16.020 3.900 3.900 3.900 0.291 0.291 0.291 0.218 0.218 0.218 0.617 0.617 0.617 0.719 0.719 0.719 0.391 0.391 0.391 0.535 0.535 0.535 1.325 1.325 1.325
3,000 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 4.6 0 0.40 100 3000 16.020 3.900 0.291 0.218 0.617 0.719 0.391 0.535 1.325
1 Vitamin and mineral premix provided—Fe, 0.04 g/kg; Cu, 10 mg/kg; Mg, 0.08 g/kg; Zn, 0.1 g/kg; I, 0.832 mg/kg; Se, 3 mg/kg; retinyl acetate, 7.000.00 UI/kg; cholecalciferol, 2.500.00 UI/kg; α -tocopherol acetate, 8.00 UI/kg; menadione, 1.58 mg/kg; thiamine, 1.00 mg/kg; riboflavin, 4.00 mg/kg; Niacinn (m´ın.), 20.1 mg/kg; pantothenic acid (m´ın.), 7.22 mg/kg; pyridoxine, 1.00 mg/kg; folic acid, 0.296 mg/kg; Biotine, 0.02 mg/kg; cyanocobalamin, 9.6 mcg/kg; Choline (m´ın.), 0.3 g/kg; Methionine, 1.00 g/kg; Colistin, 7 mg/kg.
mass (FCRM) (obtained from the ratio of feed consumption and egg mass, expressed in kg of feed/kg of egg). In order to evaluate internal and external egg quality variables, 2 eggs per replicate were collected on days 27 and 28 of each cycle, totaling 4 eggs, which were identified by treatment and replicate. Eggs were individually analyzed in a Digital Egg Tester (DET6000, Nabel, Japan) for egg weight (WG) (g), eggshell strength (EST) (kgf), albumen height (AH) (mm), yolk color (CL), and Haugh units (HU).
Economic Analysis Live performance measurements and total egg production per hen obtained at the end of each cycle, as well as treatment (feed and beak trimming) costs per hen were used for the economic analysis. Gross margin was calculated as the estimated revenue obtained with egg sales (carton with 30 dozen eggs) minus treatment cost. Labor and capital allocations were not different among treatments, because management and feeding practices, housing, and equipment were identical for all treatments. Therefore, these costs were not considered in the economic analysis. Feed costs per 30 dozen eggs were based on the historical average monthly feedstuff prices during a 10-yr
period. Feedstuff monthly prices were deflated by the National Consumer Price Index (INPC, 2015) for December 2015. Historical price data were used for the calculations due to the significant seasonal price variation of feedstuffs, and therefore historical prices tend to be more representative of the actual situation. Beak-trimming cost per hen was obtained by dividing the amount paid to a professional to beak trim 1,000 birds and calculated as USD 10.85 for the first procedure (7 D of age), and USD 21.99 for the second procedures (70 D of age). The price paid per carton of 360 eggs was obtained from the public database of the Center for Advanced Studies in Applied Economics (CEPEA, ESALQ, USP). At the time the experiment was carried out, the price paid to the farmer per egg carton was $11.74. Gross margin was calculated according to the method described by Vidal et al. (2014). The equations used to calculate gross margin (GM), total revenue (TR), and treatment cost (TC) are shown as follows: GMi = RTi − TCi TRi = (NEi) × PECi ÷ 360 TCi = FCi + BTCi, where NEi is the number of eggs produced per hen in the ith treatment; PECi is the price paid egg carton,
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Ingredients (g/kg) Maize meal Soybean meal Wheat meal Dicalcium phosphate Small particle size limestone Large particle size limestone Salt DL-Methionine Soybean oil Inert Vitamin and mineral premix1 Total
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GRANGHELLI ET AL. Table 2. Performance of white laying hens fed with 5 levels of metabolizable energy and 1 or 2 beak trimming. Variables Effects1
EP (%)
FI (g/hen/day)
EM (g)
FCRDz (kg feed/doz)
FCRM (kg feed/kg egg)
2,600 2,700 2,800 2,900 3,000
95.975 96.062 95.443 96.384 95.666
111.0 109.0 104.0 103.0 100.0
58.751 59.355 58.522 58.284 58.312
1.397 1.364 1.322 1.303 1.269
1.902 1.839 1.782 1.773 1.729
Beak Trimm.3
1 2
95.734 98.950
107.0x 104.0z
58.726 58.564
1.354x 1.310z
1.833x 1.780z
0.174
0.007
0.010
Probability 0.255 < 0.001 0.630 0.001 0.058 0.167
< 0.001 0.001 0.070
SEM4 Source of variation ME Beak Trimm.3 M
0.001 0.558 0.328 0.099
0.005 < 0.001 0.001 0.223
1 EP, EGG production (%); FI, FEED intake (g/hen/day); EM, EGG mass(g); FCRDz, feed conversion rate per dozen eggs (kg of feed/dozen eggs); FCRM, feed conversion rate per egg mass (kg of feed/kg egg mass) 2 ME, metabolizable energy 3 Beak Trimm., beak trimming 4 SEM, standard error x-z Means with different letter in columns differ statistically.
which was divided by 360 to obtain the price paid per egg in the ith treatment I; FCi is feed cost of the ith treatment during the experimental period; and TBCi is the beak-trimming cost of the ith treatment. In addition, the TC to TR ratio (TC/TR) was calculated as an indication of profitability.
Statistical Analysis For statistical evaluation, the mean value of each evaluated variable obtained in each 28-D experimental cycle was considered. Residue normality was analyzed by the Shapiro–Wilk test (PROC GLM), and the equality of variances was compared by Levene’s Test. All data were submitted to analysis of variance using the MIXED procedure to test the effects of dietary ME levels, beak trimming, and the interaction between these 2 factors. The interaction among treatments was analyzed by partitioning the sum of squares of dietary ME levels using orthogonal polynomials. All statistical analyses were performed using the Statistical Analysis System (SAS Institute, 2012), and results were considered statistically significant at 5% probability level.
RESULTS Egg production and egg mass were not affected (P > 0.05) by dietary ME levels or number of beaktrimming procedures. However, the evaluated treatments significantly influenced (P < 0.05) feed intake, FCR per dozen eggs, and per egg mass (Table 2). Increasing dietary ME levels linearly reduced feed intake (Figure 1A) and linearly improved FCR both per dozen eggs and per egg mass (Figures 1B and C). Hens sub-
mitted twice to beak trimming presented lower feed intake and better FCR per dozen eggs and per egg mass compared with those beak-trimmed once (Table 3). Egg weight was not influenced (P > 0.05) by dietary ME levels. However, hens submitted to beak trimming twice produced lighter eggs than those beak-trimmed once (Table 3). Although there was no influence (P > 0.05) of the isolated treatments on albumen height, a significant interaction (P = 0.016) between the evaluated factors was detected for this variable (Table 3). Albumen height linearly increased as dietary ME levels increased when hens were beak-trimmed once; however, when hens were beak-trimmed twice albumen height was not influenced by dietary ME level (Linear P = 0.3794, Quadratic P = 0.8683) (Figure 2A). Dietary ME levels and the number of beak trimmings individually influenced (P < 0.05) yolk color (Table 3). Dietary ME levels had a positive quadratic effect (P < 0.0001) on yolk color up to 2,800 kcal ME/kg (Figure 2B), whereas the eggs of hens submitted to beak trimming twice presented less intense yolk color than those beak-trimmed once. As albumen height, individual factors did not affect HU values, which, however, were influenced by the interaction (P < 0.05) between ME levels and the number of beak trimmings (Table 3). When the hens were beak-trimmed once, Haugh units linearly increased with dietary ME levels but not when beak-trimmed only once (linear P = 0.4627, quadratic P = 0.9754) (Figure 2C). Eggshell strength linearly increased (P < 0.05) with dietary ME levels (Table 2; Figure 2D) but was not influenced by the number of beak trimmings (P > 0.05). There were significant isolated effects (P > 0.05) of dietary ME levels and beak trimming on total
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ME2 kcal ME/kg
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ENERGY AND BEAK TRIMMING in LAYER HENS
115 110 105 100 95 2600
2700
2800
2900
3000
(B) Feed convertion ratio per dozen eggs
y = -0.000027x + 0.1826 R² = 0.5463 p=<0.0001
Metabolizable Energy (kcalME/kg)
1.55 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 1.10 2600
y = -0.0003x + 2.2144 R² = 0.4328 p<0.0001
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Feed convertion ratio per egg mass
(C) y = -0.0004x + 2.9628 R² = 0.4208 p<0.0001
2.10 2.00 1.90 1.80 1.70 1.60 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg) Figure 1. (A) Feed consumption of white laying hens fed with increasing levels of metabolizable energy. (B) Feed conversion per dozen eggs of white laying hens fed with increasing levels of metabolizable energy. (C) Feed conversion per egg mass of white laying hens fed with increasing levels of metabolizable energy.
Table 3. Quality of white laying hens’ eggs fed with 5 levels of metabolizable energy submitted to 1 or 2 beak trimming. Variables Effects1
WG (g)
AH (mm)
CL
HU
EST (kgf)
ME2 kcal ME/kg
2,600 2,700 2,800 2,900 3,000
61.233 61.814 61.308 61.256 61.220
7.737 7.713 7.822 7.765 7.867
5.496 5.618 5.658 5.533 5.477
87.295 86.922 87.704 87.412 88.010
4.971 4.985 5.136 5.201 5.250
Beak Trimm.3
1 2
61.571x 61.161z
7.801 7.760
5.585x 5.527z
87.543 87.394
5.079z 5.139x
SEM4
0.107
0.022
0.016
0.141
0.024
Source of variation ME Beak Trimm.3 ME × Beak Trimm.
0.299 0.047 0.058
0.152 0.342 0.016
0.121 0.581 0.039
< 0.001 0.155 0.404
Probability 0.001 0.045 0.530
1 WG, egg weight (g); AH, albumen height (mm); CL, yolk color; HU, Haugh units; EST, eggshell strength (kgf) 2 ME, metabolizable energy 3 Beak Trimm., beak trimming 4 SEM, standard error. x-z Means with different letter in columns differs statistically.
cost. Dietary ME levels linearly increased total cost (Figure 3A). Moreover, total production cost per hen was significantly higher when hens were beak-trimmed only once compared with the cost obtained when hens were beak-trimmed twice (Table 4). Gross margin was influenced (P < 0.05) both by dietary ME levels and number of beak trimmings.
Gross margin decreased linearly as dietary ME levels increased (Figure 3B), whereas higher gross margin was obtained when hens were beak-trimmed twice. The group of birds doubled had a higher gross margin of egg commercialization. The ratio between total production cost and total revenue was linearly reduced (P < 0.05) as dietary ME
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Feed intake (g)
(A)
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GRANGHELLI ET AL.
(A)
y = 0.0008x + 5.4459 R² = 0.358 p<0.0001
Yolk color
8.00 7.80 7.60 7.40 7.20 2600
2700
2800
2900
y = -0.0000037x2 + 0.0207x - 23.194 R² = 0.2046 p<0.0001
5.90 5.70 5.50 5.30 5.10 2600
3000
(C) Haugh Units
y = 0.0049x + 73.776 R² = 0.2987 p=0.0003
89.00 87.00 85.00
2700
2800
2900
Eggshell Strenght (kgf)
(D)
91.00
83.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Metabolizable Energy (kcalME/kg)
y = 0.0008x + 2.9434 R² = 0.2602 p<0.0001
5.50 5.25 5.00 4.75 4.50 2600
3000
Metabolizable Energy (kcalME/kg)
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Figure 2. (A) Albumen height of eggs of white laying hens fed with increasing levels of metabolizable energy. (B) Yolk color of eggs of white laying hens fed with increasing levels of metabolizable energy. (C) Haugh unit of eggs of white laying hens fed with increasing levels of metabolizable energy. (D) Eggshelll strength of white laying hens fed with increasing levels of metabolizable energy.
(B)
(A) y = 0.0037x + 8.6052 R² = 0.3074
20.50
Gross Margin($)
Treatment cost ($)
21.00 20.00 19.50 19.00 18.50 18.00 17.50 17.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalEM/kg)
(C)
TC to TR ratio
1.05
y = -0.0041x + 13.126 R² = 0.2975
4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 -1.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
y = 0.0002x + 0.3649 R² = 0.2996
1.00 0.95 0.90 0.85 0.80 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg) Figure 3. (A) Treatment cost of white laying hens fed with increasing levels of metabolizable energy. (B) Gross margin of eggs of white laying hens fed with increasing levels of metabolizable energy. (C) TC to RT ratio of eggs of white laying hens fed with increasing levels of metabolizable energy.
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Albumen Height (mm)
8.20
(B)
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ENERGY AND BEAK TRIMMING in LAYER HENS Table 4. Indicators of the economic productivity of white laying hens. Variables Effects1
TC (US$)
TR (US$)
GM (US$)
TC/TR (US$)
2,600 2,700 2,800 2,900 3,000
5.296 5.425 5.598 5.628 5.733
6.04 6.04 6.02 6.09 6.02
0.744 0.621 0.410 0.363 0.275
0.870 0.890 0.930 0.940 0.950
Beak Trimm.3
1 2
5.733x 5.340z
6.04 6.04
0.278z 0.689x
0.950x 0.880z
0.105
0.034
0.119
0.005
Probability 0.343 < 0.001 0.930 < 0.001 0.102 0.063
< 0.001 < 0.001 0.065
SEM Source of variation ME Beak Trimm.3 ME × Beak Trimm
< 0.001 < 0.001 0.066
1 TC, Treatment cost (US$); TR, total revenue (US$); GM, gross margin (US$); TC/TR, TC to RT ratio (US$). 2 ME, metabolizable energy 3 Beak Trimm., beak trimming x-z Means with different letters in superscript in columns differs (P < 0.05).
level increased (Figure 3C). In addition, higher TC/TR ratio (P < 0.05) was obtained when hens were beaktrimmed twice (Table 4).
DISCUSSION In the present study, dietary ME levels did not affect egg production, as previously observed by Peguri and Coon (1991) and Ost and Peixoto (1998), when layers were fed ME levels of 2,645 to 2,971 and 2,650 to 2,950 kcal/kg of feed, respectively. These results indicate that layers are able to adapt to different nutritional, environmental, and management conditions, maintaining their egg production. On the other hand, Xavier and Peixoto (1997) observed an increased egg production only when intermediate ME levels (2,750 and 2,850 kcal/kg of feed) were fed to layers, suggesting that the efficiency of dietary energy utilization for egg production is reduced at higher energy levels (Peguri and Coon, 1991). These findings support the recommendation of 2,800 kcal ME/kg for layers proposed by Rostagno et al. (2011). The linear reduction of feed intake as ME levels increased in the present study was also observed by Latshaw et al. (1990), Peguri and Coon (1991), and Wu et al. (2005). This result was expected, as layer feed intake is regulated by dietary energy levels and it is inversely proportional to dietary ME levels. According to Wu et al. (2005), feed intake is reduced in 1% for every 39 kcal/kg increase in dietary ME content. On the other hand, the higher feed intake observed when hens were beak-trimmed once (5mm of nostrils) may be related to their higher beak size (7 mm of nostrils), and consequently their better feed prehension. Glatz (2003) observed that hens with larger beaks consume more feed than those with smaller beaks. Ara´ ujo et al. (2005) also determined higher feed intake when
layers were beak-trimmed once compared with those beak-trimmed twice. The worse feed conversion obtained when hens were beak-trimmed once may be possibly due to the higher selectivity of the feed particles, which may have influence their nutrient balance. In addition, when pecking the feed during selection, part of the feed is thrown out the feeders, which contributes to increase feed waste (Ara´ ujo et al., 2005), consequently leading to an overestimation of feed intake, when calculated as feed offer minus feed residues in the feeders. The FCR per dozen eggs and per egg mass results obtained are consistent with the hypothesis of feed waste, as no difference in egg production was observed between hens beak-trimmed once or twice. The linear improvement in FCR per dozen egg and per egg mass as dietary ME levels increased may be explained by the higher dietary inclusion of lipids. Soybean oil has an extra caloric effect and reduces feed passage rate in the gastrointestinal tract, increasing nutrient utilization and, therefore, feed conversion ratio (Bertechini, 1998). Danicke et al. (2000) observed better FCR with increasing inclusion levels of soybean oil in layer diets up to a maximum inclusion level of 10%. On the other hand, the results of the present study differ from those of Xavier and Peixoto (1997) and Ost and Peixoto (2000), who obtained better FCR when layers were fed intermediate ME levels (2,750 and 2,850 kcal/kg, respectively) and worse FCR at extreme ME levels (2,650 and 2,950 kcal ME/kg) were fed. Albeit statistically different, the eggs of the hens beak-trimmed once were only 0.4 g heavier than those beak-trimmed twice, and both groups reached the desired egg weight of about 60 g. Pizzolante et al. (2007), evaluating 3 lengths of beak trimming in laying quails, also determined slightly lower egg weight when half of the beak was trimmed compared with no beak trimming and one-third of the beak trimmed. Possibly, the
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ME2 kcal ME/kg
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GRANGHELLI ET AL.
terial were changed. This result shows that, although feed intake was significantly reduced as dietary ME levels increased, feed cost was not reduced. In fact, a total production cost difference of USD 0.437 was calculated between the group fed the highest (3,000 kcal ME/kg of feed) and the lowest (2,600 kcal ME/kg of feed) energy level. In the study of Rabello et al. (2007), feed cost increased in USD 0.031 with the inclusion of 4% of soybean oil compared with a diet with no soybean oil. Ribeiro et al. (2013) determined a USD 0.52 increase in the production cost of egg carton (30 dozen eggs) when dietary ME levels increased from 2,700 to 3,000 kcal/kg. The absence of effects of ME levels and beak trimming on total revenue may be attributed to the fact that egg production was not influenced by either factor. On the other hand, the gross margin obtained with egg sales was influenced by the treatments. The difference in the gross margin between the lowest level (2,600 kcal ME/kg) and the highest (3,000 kcal ME/kg) dietary energy level was USD 0.469 per hen, in agreement with the findings of Santos et al. (2011), who compared 2 dietary oil inclusion levels (2 and 4%) and also obtained higher gross margin with the lower oil inclusion. The analysis of the effect of beak trimming on the gross margin showed higher gross margin (+USD 0.411) and higher profitability (total cost/total revenue) when hens were beak-trimmed twice, which may be explained by their higher feed intake compared with those beak-trimmed once. These findings suggest that feed or dietary nutrients were wasted (Blokhuis et al., 1987) due to the possible greater feed selection by the hens beak-trimmed once. These results are in agreement with the findings of Davis et al. (2004), who demonstrated that beak trimming reduced feed cost and increased net profit, because beak-trimmed hens showed better feed utilization or lower feed waste. The findings of the present study indicate that if only egg production and egg quality results were taken into account, higher dietary ME levels would be recommended due to their positive influence on layer performance and egg quality, as well as beak trimming hens only once, as it did not compromise their performance and egg quality. In addition, the second beak trimming would not be required, complying with animal welfare requirements of minimizing stress and trauma. However, the economic analysis completely changed the scenario. Feed cost increased and profitability decreased as dietary ME levels increased. In addition, when hens are beak-trimmed only once, there is greater feed particle selection and feed waste, resulting in higher total production cost and a marked reduction in profitability. Therefore, from the economic point of view, it is recommended to beak-trim layers twice due to production cost savings.
REFERENCES Almeida, V. R., A. N. Dias, C. F. D. Bueno, F. A. P. Couto, P. Rodrigues, W. C. L. Nogueira, and D. E. Faria Filho. 2012. Crude
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hens beak-trimmed once were able to select feed particles which nutrients allowed increasing egg weight. The linear increase in albumen height and Haugh units as a function of increasing dietary ME levels observed in the hens beak-trimmed once supports this hypothesis. Poultry are able to select feed particle due to the presence of mechanoreceptors in the beak, which explains their preference for large feed particles (Schiffman, 1968; Gentle, 1979). When beak trimming is not too severe, these mechanoreceptors are partly preserved, allowing particle selection (Freire et al., 2011). The lack of influence of dietary ME levels on egg weight was also observed by Valkonen et al. (2008). A possible explanation is that the dietary protein level supplied the hens’ requirements. In addition, according to NRC (1994), egg weight increase is related to high linoleic acid rather than to high total lipid levels in the diet. It should be noted that the level of this fatty acid remained constant in all experimental diets. The increase in yolk color intensity up to the level of 2,800 kcal EM/kg of feed is consistent with the findings of Gunawardana et al. (2008) evaluating increasing ME levels in layer hens’ diets. This result is related to the better absorption of fat-soluble yolk pigments (xanthophylls) when hens are fed diets with high oil or fat levels. The reduction in yolk color intensity observed at 2,800 kcal ME/kg of feed may be attributed to the low feed intake of the hens fed this ME level, and therefore their low intake of corn, which is one of the main sources of pigments responsible for yolk color. Hens beak-trimmed twice showed, on average, lower yolk color intensity than those beak-trimmed once, which also suggests the selection of larger particles such as corn, which is rich in xanthophylls (Amerah et al., 2007). The observed increasing eggshell strength results may be explained by the reduction of heat increment as dietary oil addition increases (Daghir, 2008), allowing better nutrient utilization by the hens, as the present experiment was carried out during a season when high average temperatures (>25◦ C) are recorded in the region (UNICAMP, 2018). The total cost obtained for the group beak-trimmed once was USD 0.393 higher than that of the group beaktrimmed twice. This result may be due to the higher feed intake or feed waste of hens’ beak-trimmed one. In the study of Davis et al. (2004), layers not submitted to beak trimming presented higher feed intake than beaktrimmed layers. Those authors demonstrated that beak trimming reduced feed cost and increased net profit, because beak-trimmed hens showed better feed utilization or lower feed waste. Regarding the economic evaluation, the linear increase of feed cost as dietary ME levels increased was expected, as soybean oil was gradually added to the diets with the purpose of increasing dietary energy density. Therefore, the feed cost increased as a function only of oil inclusion, as all other nutrients remained constant and only the proportions of oil and inert ma-
ENERGY AND BEAK TRIMMING in LAYER HENS
National Research Council (NRC). 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. Novogen. 2014. Novogen White management guide. NovogenLayer. Accessed Nov. 2017. http://www.tombarron.co.uk/ wp-content/uploads/2014/03/novogen-white-cs-managementguide-english-23-6-2009-gb-v.pdf Oda, P. K., V. M. B. Moraes, J. Ariki, R. D. Malheiros, R. L. Furlan, and S. Kronka. 2000. Desempenho comparativo entre duas linhagens de roedeiras comerciais debicadas em diferentes idades na fase de recria. Cienc. Rural 30:693–698. Ost, P. R., and R. R. Peixoto. 1998. N´ıveis de energia metaboliz´avel em ra¸c˜oes para poedeiras de ovos marrons nas condi¸c˜oes de inverno de 1997 de Pelotas-RS. Proc. 35th Reuni˜ ao Anual da Sociedade Braz de Zootec. 35:368–370. (Abstr.) Ost, P. R., and R. R. Peixoto. 2000. N´ıveis de energia metaboliz´avel em ra¸c˜oes para poedeiras de ovos marrons nas condi¸c˜oes de inverno e ver˜ ao da regi˜ ao de Pelotas – RS. R. Bras. Zootec. 29:2283– 2291. Peguri, A., and C. Coon. 1991. Effect of temperature and dietary energy on layer performance. Poult. Sci. 70:126–138. Pizzolante, C. C., E. A. Garcia, E. S. P. B. Saldanha, C. Lagan´ a, A. B. G. Faitarone, H. B. A. Souza, and K. Pelicia. 2007. Beak trimming methods and their effect on the performance and egg quality of Japanese Quails (Coturnix japonica) during lay. Rev. Bras. Cienc. Avic. 9:17–21. Rabello, C. B. V., A. L. Pinto, E. P. Silva, and S. B. P. Lima. 2007. N´ıveis de ´oleo de soja na dieta de poedeiras comerciais criadas em regi˜ao de alta temperatura. R. Bras. Cienc. Agr. 2:174– 182. Ribeiro, P. A. P., J. B. Matos Jr, A. C. A. Queiroz, L. J. C. Lara, and N. Bai˜ ao. 2013. Efeito dos n´ıveis de energia para poedeiras comerciais no per´ıodo final de produ¸c˜ao sobre o desempenho, a convers˜ao alimentar e energ´etica e a qualidade de ovos. Arq. Bras. Med. Vet. Zootec. 65:1491–1499. Rostagno, H. S., L. F. T Albino, J. L. Donzele, P. C. Gomes, R. F. Oliveira, D. C. Lopes, A. S. Ferreira, and S. L. T. Barreto. 2011. Tables brasileiras para aves e su´Inos—Composi¸c˜ao de alimentos e exigˆencias nutricionais. 3rd ver. ed. Editora UFV. Vicosa, MG, Brazil. Santos, M. S. V., G. B. Esp´ındola, A. S. Khan, L. E. Carvalho, and J. P. B. Loureiro. 2011. An´ alise econˆomica da produ¸c˜ao de poedeiras comercias submetidas `as dietas suplementadas com diferentes o´leos vegetais. Inf. Econ. 41:54–59. SAS Institute. 2012. User’s Guide. Statistics Version 9.2 ed. SAS Inst., Inc., Cary, NC. Schiffman, H. R. 1968. Texture preference in the domestic chick. J. Comp. Physiol. Psychol. 66:540–541. Silva, A. B. P., E. A Garcia, A. B. Molino, and E. M. P. Silva. 2012. Metabolizable energy and oil intake in brown commercial layers. R. Bras. Zootec. 41:2232–2237. Stadelman, W. J., D. Newkirk, and L. Newby. 2017. Egg Science and Technology. 4th erv. Ed. CRC Press, Binghamton, NY. Unicamp. 2018. Clima dos munic´ıpios paulistas. Cepagri Meteorologia Unicamp. Accessed Feb. 2018. http://www.cpa. unicamp.br/outras-informacoes/clima muni 442.html Valkonen, E., E. Ven¨ al¨ ainen, L. Rossow, and J. Valaja. 2008. Effects of dietary energy content on the performance of laying hens in furnished and conventional cages. Poult. Sci. 87:844–852. Vidal, M. P., G. Aferri, A. S. C. P. Pereira, and A. H. Gameiro. 2014. Modelo matem´ atico para an´ alise econˆomica de dietas: uma aplica¸c˜ao na avalia¸c˜ao dos diferentes cereais utilizados na alimenta¸c˜ao de cordeiros em confinamento. Bol. Ind. Anim. 71:273– 283. Wu, G., M. M. Bryant, R. A. Voitle, and D. A. Roland, 2005. Effect of dietary energy on performance and egg composition of Bovans White and Dekalb White hens during phase I. Poult. Sci. 84:1610– 1615. Wu, G., M. M. Bryant, P. Gunawardana, and D. A. Roland. 2007. Effect of nutrient density on performance, egg components, egg solids, egg quality, and profits in eight commercial leghorn strain during phase one. Poult. Sci. 86:691–697. Xavier, E. G., and R. R. Peixoto. 1997. N´ıveis de energia metaboliz´avel em ra¸c˜oes para poedeiras nas condi¸c˜oes de temperatura e umidade relativa no inverno do extremo sul do brasil. R. Bras. Zootec. 26:391–395.
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protein and metabolizable energy levels for layers reared in hot climates. Rev. Bras. Cienc. Avic. 14:203–208. Amerah, A. M., V. Ravindran, R. G. Lentle, and D. G. Thomas. 2007. Feed particle size: implications on the digestion and performance of poultry. Worlds Poult. Sci. J. 63:439–455. Ara´ ujo, L. F., M. B. Caf´e, N. S. M. Leandro, O. M. Junqueira, C. S. S. Ara´ ujo, M. I. R. Cunha, and C. C. Silva. 2005. Desempenho de poedeiras comerciais submetidas ou n˜ao a diferentes m´etodos de debicagem. Cienc. Rural 35:169–173. Beterchini, A. G. 1998. Nutri¸c˜ao de monog´ astricos. 2nd ver. ed. Editora UFLA, Lavras, MG. Blokhuis, H. J., J. W. Van der Haar, and P. G. Koole. 1987. Effects of beak trimming and floor type on feed consumption and body weight of pullets during rearing. Poult. Sci. 66:623–625. Colvara, I. G., J. C. Maier, F. Rutz, P. A. R. Brum, and E. A. Pan. 2002. N´ıveis de energia metaboliz´avel em ra¸c˜oes para poedeiras semi-pesadas durante o segundo ciclo de produ¸c˜ao no ver˜ ao. R. Braz. Agrociˆencia. 8:47–49. Costa, F. G. P., H. C. Souza, C. A.V. Gomes, L. R. Barros, P.A. Brand˜ ao, G. Nascimento, A. W. R. Santos, and V. S. Amarante J´ unior. 2004. N´ıveis de prote´ına bruta e energia metaboliz´ avel na produ¸c˜ao e qualidade dos ovos de poedeiras da linhagem lohmann brown. Ciˆenc. Agrotec. 28:1421–1427. Costa, F. G. P., J. S. Costa, C. C. Goulart, D. F. Figueiredo-Lima, R. C. Lima Neto, and B. J. S Quirino. 2009. Metabolizable energy levels for semi-heavy laying hens at the second production cycle. R. Bras. Zootec. 38:857–862. Daghir, N. J., ed. 2008. Nutrient requirements of poultry at high temperatures. Pages 132–159 in Poultry Production in Hot Climates. CAB Internationa, Cambridge. D¨ anicke, S., I. Halle, H. Jeroch, W. B¨ ottcher, P. Ahrens, R. Zachmann, and S. G¨ otze. 2000. Effect of soy oil supplementation and protein level in laying hen diets on praecaecal nutrient digestibility, performance, reproductive performance, fatty acid composition of yolk fat, and on other egg quality parameters. Eur. J. Lipid Sci. Technol. 102:218–232. Davis, G. S., K. E. Anderson, and D. R. Jones. 2004. The effects of different beak trimming techniques on plasma corticosterone and performance criteria in single comb white leghorn hens. Poult. Sci. 83:1624–1628. Fischer Jr, A. A., Jr, L. F. T. Albino, H. S. Rostagno, and P. C. Gomes. 1998. Determina¸c˜ao dos valores de energia metaboliz´ avel de alguns alimentos usados na alimenta¸c˜ao de aves. R. Bras. Zootec. 7:314–318. Freire, R., M. A. Eastwood, and M. Joyce. 2011. Minor beak trimming in chickens leads to loss of mechanoreception and magnetoreception. J. Anim. Sci. 89:1201–1206. Gentle, M. J. 1979. Sensory control of feed intake. Pages 259–273 in Food Intake Regulation in Poultry. K. N. Boormanand, and B. M. Freeman, eds. Longman, Edinburgh. Glatz, P. C. 2003.The effect of beak length and condition on food intake and feeding behaviour of hens. Intern. J. Poult. Sci. 2:53– 57. Gunawardana, P., D. A. Roland, and M. M. Bryant. 2008. Effect of energy and protein on performance, egg components, egg solids, egg quality, and profits in molted Hy-Line W-36 hens. J. Appl. Poult. Res. 17:432–439. Hughes, B. O., and M. J. Gentle. 1995. Beak trimming of poultry: its implications for welfare. Worlds Poult. Sci. J. 51:51–61. ´Indice nacional de pre¸cos ao consumidor (INPC). 2015. S´erie hist´ orica. Accessed Nov. 2017. http://www.portalbrasil. net/incpc.net Janczak, A. M., and A. B. Riber. 2015. Review of rearing-related factors affecting the welfare of laying hens. Poult. Sci. 94:1454– 1469. Junqueira, O. M., A. C. de Laurentiz, R. S. Filardi, E. A. Rodrigues, and E. M. Casartelli. 2006. Effects of energy and protein levels on egg quality and performance of laying hens at early second production cycle. J. Appl. Poult. Res. 15:110–115. Latshaw, J. D., G. B. Havenstein, and V. Toelle. 1990. Energy level in the laying diet and its effects on the performance of three commercial leghorn strains. Poult. Sci. 69:1998–2007. Lyon. 2007. General guide to beak trimming. Lyon USA. Accessed Nov. 2016. https://lyonusa.com/wp-content/uploads/ 2015/05/beaktrimmingguide.pdf
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Department of Animal Nutrition and Production, University of S˜ ao Paulo (FMVZ-USP), Pirassununga, 13635900, Brazil; † School of Veterinary Medicine and Animal Science, University of S˜ ao Paulo (FMVZ- USP), ao Paulo (FZEA-USP), S˜ ao Paulo, 05508270, Brazil; and ‡ Department of Animal Science, University of S˜ Pirassununga, 13635900,Brazil were analyzed. Egg production was positively influenced by dietary ME levels. Feed intake (FI), feed conversion ratio (FCR), egg weight, albumen height, Haugh units, and eggshell strength were positively influenced by increasing dietary ME levels. Hens beaktrimmed once presented higher feed intake and worse FCR than those beak-trimmed twice. Beak trimming did not affect egg production, egg weight, albumen height, Haugh units, and eggshell strength. Production costs increased as dietary ME levels increased. Higher production cost was determined for hens beaktrimmed once than for those beak-trimmed twice. Total revenue was not influenced by the treatments. Gross margin was linearly decreased as dietary ME levels increased and was lower when hens were beak-trimmed once. Increasing dietary ME levels and beak trimming hens once reduce the economic viability of egg production.
ABSTRACT Considering the market availability of new commercial layer strains with distinct characteristics and behaviors, studies to update their nutritional requirements and to evaluate the need to adopt management practices, such as beak trimming, are needed. The objective of the present study was to evaluate the effects of dietary metabolizable energy (ME) levels and beak trimming on the live performance, egg quality, and economics of commercial layers. A total of 640 Novogen White layers were distributed according to a randomized experimental design in a 5 × 2 factorial arrangement (5 ME levels × 2 beak trimming treatments), totaling 10 treatments with 8 replicates of 8 hens each. The evaluated dietary ME levels were 2,600; 2,700; 2,800; 2,900; and 3,000 kcal/kg of feed. Layers were beak-trimmed once (7 days old) or twice (7 and 70 days old). Live performance and egg quality mesuraments and production economics
Key words: beak trimming, performance, metabolizable energy, economic viability 2019 Poultry Science 0:1–9 http://dx.doi.org/10.3382/ps/pez145
INTRODUCTION
body temperature, and synthesis of organic tissues. In addition, energy can be stored or directed to production functions, such as egg production (NRC, 1994). In laying hens, the amount of energy of the diet influences in parts the consumption of feed, which is also influenced by other factors, such as body weight, ambient temperature, photoperiod, among others. Therefore, its ratio to other dietary nutrients is extremely important. As metabolizable energy (ME) is negatively correlated with feed intake, the ratio between energy and other dietary nutrients in the diet should be carefully taken into account in diet formulation in order to provide adequate nutrient intake (Fischer et al., 1998). The research on the ME requirements of commercial layers has shown controversial results. For instance, literature reports both positive (Wu et al., 2007; Costa et al., 2009) and negative (Colvara et al., 2002; Junqueira et al., 2006; Almeida et al., 2012; Silva et al., 2012) influence of increasing dietary ME content
The nutritional requirements of commercial laying hens vary according to age, genetic strain, environmental conditions, management practices, dietary amino acid and energy levels, among other factors. Therefore, layers’ nutritional requirements need to be regularly evaluated and updated in order to formulate diets suitable for each production situation (Costa et al., 2004). Energy is the main nutritional component of commercial layer diets. Animals supply their energy requirements by oxidizing dietary carbohydrates, fats, proteins, and fibers. Energy is required for the maintenance of vital body functions, such as movement, regulation of C 2019 Poultry Science Association Inc. Received June 28, 2018. Accepted June 28, 2018. 1 Corresponding author: [email protected]
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Carlos A. Granghelli,∗,1 Maria F. C. Burbarelli ,∗ Karoline D. Lelis,† Paulo H. Pelissari,∗ Nat´ alia B. P. Utimi,‡ Brunna G. S. Leite,‡ Fabricia A. Roque,‡ Priscila S. Zorzetto,∗ Julio C. C. Balieiro,∗ L´ ucio F. Ara´ ujo,‡ and Cristiane S. S. Ara´ ujo∗
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MATERIALS AND METHODS Birds, Housing, and Experimental Diets The experimental protocol was approved by the Ethics Committee on the Use of Animals of the School of Veterinary Medicine and Animal Science of the University of S˜ ao Paulo under protocol n. 9176031014. During the rearing period (0 to 6 wk of age), 864 one-day-old Novogen White pullets were housed in battery cages (12 birds per cage). By the end of week 6, birds were transferred to development cages (10 birds per cage), where they remained until the end of the development phase (week 16). The management practices, lighting program, and feeding applied during the rearing and development periods followed the management guide of genetic company (Novogen, 2014). At the beginning of week 17, 640 hens were transferred to production cages (density of 562.5 cm2 per bird), located in a masonry shed with open sides with screens, and equipped with fans and foggers for temperature control. The metal cages measured 1.0 m × 0.45 m × 0.45 m and were arranged in a pyramidal system. Cages were equipped with nipple drinkers and trough feeders.
At 7 D of age, all hens were weighed and beaktrimmed, and only half of the birds (n = 432) were submitted to a second beak trimming at 70 D of age. In the first (7 D of age) and second (70 D of age) beak trimming, a moderate cut was used, 5 and 7 mm of the nostrils, respectively. The conventional beak trimming method, using hot blade, was applied. It was performed by the same trained employee, who was experienced in working with the evaluated genetic strain, and according to the directions of the equipment manufacturer (Lyon, 2007). Until week 19, all hens were fed a single diet. In week 20, chickens were individually weighed and distributed to cages according to body weight and beak-trimming treatments. Hens were evaluated for 28 wk (20 to 48 wk of age), divided into 7 cycles of 28 D each. The laying hens were distributed in a completely randomized design, in a 5 × 2 factorial experiment, with 5 levels of apparent ME in the diet (2,600; 2,700; 2,800; 2,900 and 3,000 kcal ME/kg of feed) and 2 beak trimming treatments (with or without beak trimming at 70 D of age), totaling 10 treatments with 8 replicates of 8 hens each. The effects of beak trimming once or twice and the interaction of dietary ME levels and beak trimming were analyzed. A basal diet based on corn and soybean meal, containing 2,800 kcal ME/kg, was formulated according to nutritional recommendations of Rostagno et al. (2011). The evaluated dietary ME levels were obtained by the replacement of the inert material (kaolin) by soybean oil. The experimental diets were isonutritional and are shown in Table 1. Hens were offered water and feed ad libitum, and the feed was distributed twice daily. A lighting program of 16 h of light was applied, as recommended by the genetic line manual (Novogen, 2014). The eggs were collected twice daily, and the total numbers of intact and defective eggs were recorded per replicate.
Evaluation of Live Performance and Egg Quality The live performance variables were evaluated per replicate at the end of each 28-D cycle. The following variables were determined: total egg production (EP) (total number of eggs produced divided by the average number of hens of each replicate, expressed as percentage of posture/hen/day), feed intake (FI) (amount of feed consumed per each replicate divided by the average number of hens, expressed in g/hen/day), egg mass (EM) (average egg weight of each replicate multiplied by egg production percentage, expressed in g/bird/day), feed conversion ratio (FCR) per dozen eggs produced (FCRDz) (obtained through the ratio of feed consumption and average percentage of eggs produced, multiplied by the dozen eggs, expressed in kg of feed/dozen eggs), and feed conversion ratio per egg
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on egg quality. The lack of consensus on the dietary ME recommendations for commercial laying hens may be attributed to the different growth rates, performance levels, and behavior of the current genetic lines. Therefore, it is critical to determine or to update the specific ME requirements of each genetic strain. Routine management practices also have a direct influence on egg production and quality. It has been demonstrated that management practices that cause stress, such as beak trimming, can impair bird welfare and egg production and quality (Janczak and Riber, 2015; Stadelman et al., 2017), which has led to questioning the real need of such practice (Oda et al., 2000). Beak trimming is an aggressive, painful, and stressful procedure for commercial layers (Oda et al., 2000). However, according to Hughes and Gentle (1995), it is required to reduce cannibalism, feather pecking, feed waste, and mortality on layer farms. It is recommended that beaks should be trimmed as little as possible (Janczak & Riber, 2015) and to be performed by a trained professional using the least aggressive method. However, hot blade is still the most frequent method applied. Considering that the need of such aggressive practice is controversial, and the emergence of new, more docile layer strains, the study of the influence these factors on egg production and quality may be useful. Moreover, as feed is one of the main cost of egg production, the influence of the energy requirements of modern commercial layers strains on feed intake should be re-evaluated. The objective of the present study was to evaluate the effects of dietary ME levels, beak trimming, and their interaction on the live performance, egg quality, and economics of commercial layers.
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ENERGY AND BEAK TRIMMING in LAYER HENS Table 1. Composition of the experimental diets. Diets Metabolizable energy levels (kcal/kg of feed)
AME. kcal/kg Crude Protein, % Ca % P% Na % Methionine + cystine % Lysine, % Methionine % Threonine % Linoleic Acid
2,600 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 0 4.6 0.40 100 2.600 16.020 3.900 0.291 0.218 0.617 0.719 0.391 0.535 1.325
2,700 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 1.15 3.45 0.40 100
2,800 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 2.30 2.30 0.40 100
2,900 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 3.45 1.15 0.40 100
Calculated composition, g/kg 2.700 2.800 2.900 16.020 16.020 16.020 3.900 3.900 3.900 0.291 0.291 0.291 0.218 0.218 0.218 0.617 0.617 0.617 0.719 0.719 0.719 0.391 0.391 0.391 0.535 0.535 0.535 1.325 1.325 1.325
3,000 60.18 23.5 0.42 1.06 4.61 4.61 0.46 0.16 4.6 0 0.40 100 3000 16.020 3.900 0.291 0.218 0.617 0.719 0.391 0.535 1.325
1 Vitamin and mineral premix provided—Fe, 0.04 g/kg; Cu, 10 mg/kg; Mg, 0.08 g/kg; Zn, 0.1 g/kg; I, 0.832 mg/kg; Se, 3 mg/kg; retinyl acetate, 7.000.00 UI/kg; cholecalciferol, 2.500.00 UI/kg; α -tocopherol acetate, 8.00 UI/kg; menadione, 1.58 mg/kg; thiamine, 1.00 mg/kg; riboflavin, 4.00 mg/kg; Niacinn (m´ın.), 20.1 mg/kg; pantothenic acid (m´ın.), 7.22 mg/kg; pyridoxine, 1.00 mg/kg; folic acid, 0.296 mg/kg; Biotine, 0.02 mg/kg; cyanocobalamin, 9.6 mcg/kg; Choline (m´ın.), 0.3 g/kg; Methionine, 1.00 g/kg; Colistin, 7 mg/kg.
mass (FCRM) (obtained from the ratio of feed consumption and egg mass, expressed in kg of feed/kg of egg). In order to evaluate internal and external egg quality variables, 2 eggs per replicate were collected on days 27 and 28 of each cycle, totaling 4 eggs, which were identified by treatment and replicate. Eggs were individually analyzed in a Digital Egg Tester (DET6000, Nabel, Japan) for egg weight (WG) (g), eggshell strength (EST) (kgf), albumen height (AH) (mm), yolk color (CL), and Haugh units (HU).
Economic Analysis Live performance measurements and total egg production per hen obtained at the end of each cycle, as well as treatment (feed and beak trimming) costs per hen were used for the economic analysis. Gross margin was calculated as the estimated revenue obtained with egg sales (carton with 30 dozen eggs) minus treatment cost. Labor and capital allocations were not different among treatments, because management and feeding practices, housing, and equipment were identical for all treatments. Therefore, these costs were not considered in the economic analysis. Feed costs per 30 dozen eggs were based on the historical average monthly feedstuff prices during a 10-yr
period. Feedstuff monthly prices were deflated by the National Consumer Price Index (INPC, 2015) for December 2015. Historical price data were used for the calculations due to the significant seasonal price variation of feedstuffs, and therefore historical prices tend to be more representative of the actual situation. Beak-trimming cost per hen was obtained by dividing the amount paid to a professional to beak trim 1,000 birds and calculated as USD 10.85 for the first procedure (7 D of age), and USD 21.99 for the second procedures (70 D of age). The price paid per carton of 360 eggs was obtained from the public database of the Center for Advanced Studies in Applied Economics (CEPEA, ESALQ, USP). At the time the experiment was carried out, the price paid to the farmer per egg carton was $11.74. Gross margin was calculated according to the method described by Vidal et al. (2014). The equations used to calculate gross margin (GM), total revenue (TR), and treatment cost (TC) are shown as follows: GMi = RTi − TCi TRi = (NEi) × PECi ÷ 360 TCi = FCi + BTCi, where NEi is the number of eggs produced per hen in the ith treatment; PECi is the price paid egg carton,
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Ingredients (g/kg) Maize meal Soybean meal Wheat meal Dicalcium phosphate Small particle size limestone Large particle size limestone Salt DL-Methionine Soybean oil Inert Vitamin and mineral premix1 Total
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GRANGHELLI ET AL. Table 2. Performance of white laying hens fed with 5 levels of metabolizable energy and 1 or 2 beak trimming. Variables Effects1
EP (%)
FI (g/hen/day)
EM (g)
FCRDz (kg feed/doz)
FCRM (kg feed/kg egg)
2,600 2,700 2,800 2,900 3,000
95.975 96.062 95.443 96.384 95.666
111.0 109.0 104.0 103.0 100.0
58.751 59.355 58.522 58.284 58.312
1.397 1.364 1.322 1.303 1.269
1.902 1.839 1.782 1.773 1.729
Beak Trimm.3
1 2
95.734 98.950
107.0x 104.0z
58.726 58.564
1.354x 1.310z
1.833x 1.780z
0.174
0.007
0.010
Probability 0.255 < 0.001 0.630 0.001 0.058 0.167
< 0.001 0.001 0.070
SEM4 Source of variation ME Beak Trimm.3 M
0.001 0.558 0.328 0.099
0.005 < 0.001 0.001 0.223
1 EP, EGG production (%); FI, FEED intake (g/hen/day); EM, EGG mass(g); FCRDz, feed conversion rate per dozen eggs (kg of feed/dozen eggs); FCRM, feed conversion rate per egg mass (kg of feed/kg egg mass) 2 ME, metabolizable energy 3 Beak Trimm., beak trimming 4 SEM, standard error x-z Means with different letter in columns differ statistically.
which was divided by 360 to obtain the price paid per egg in the ith treatment I; FCi is feed cost of the ith treatment during the experimental period; and TBCi is the beak-trimming cost of the ith treatment. In addition, the TC to TR ratio (TC/TR) was calculated as an indication of profitability.
Statistical Analysis For statistical evaluation, the mean value of each evaluated variable obtained in each 28-D experimental cycle was considered. Residue normality was analyzed by the Shapiro–Wilk test (PROC GLM), and the equality of variances was compared by Levene’s Test. All data were submitted to analysis of variance using the MIXED procedure to test the effects of dietary ME levels, beak trimming, and the interaction between these 2 factors. The interaction among treatments was analyzed by partitioning the sum of squares of dietary ME levels using orthogonal polynomials. All statistical analyses were performed using the Statistical Analysis System (SAS Institute, 2012), and results were considered statistically significant at 5% probability level.
RESULTS Egg production and egg mass were not affected (P > 0.05) by dietary ME levels or number of beaktrimming procedures. However, the evaluated treatments significantly influenced (P < 0.05) feed intake, FCR per dozen eggs, and per egg mass (Table 2). Increasing dietary ME levels linearly reduced feed intake (Figure 1A) and linearly improved FCR both per dozen eggs and per egg mass (Figures 1B and C). Hens sub-
mitted twice to beak trimming presented lower feed intake and better FCR per dozen eggs and per egg mass compared with those beak-trimmed once (Table 3). Egg weight was not influenced (P > 0.05) by dietary ME levels. However, hens submitted to beak trimming twice produced lighter eggs than those beak-trimmed once (Table 3). Although there was no influence (P > 0.05) of the isolated treatments on albumen height, a significant interaction (P = 0.016) between the evaluated factors was detected for this variable (Table 3). Albumen height linearly increased as dietary ME levels increased when hens were beak-trimmed once; however, when hens were beak-trimmed twice albumen height was not influenced by dietary ME level (Linear P = 0.3794, Quadratic P = 0.8683) (Figure 2A). Dietary ME levels and the number of beak trimmings individually influenced (P < 0.05) yolk color (Table 3). Dietary ME levels had a positive quadratic effect (P < 0.0001) on yolk color up to 2,800 kcal ME/kg (Figure 2B), whereas the eggs of hens submitted to beak trimming twice presented less intense yolk color than those beak-trimmed once. As albumen height, individual factors did not affect HU values, which, however, were influenced by the interaction (P < 0.05) between ME levels and the number of beak trimmings (Table 3). When the hens were beak-trimmed once, Haugh units linearly increased with dietary ME levels but not when beak-trimmed only once (linear P = 0.4627, quadratic P = 0.9754) (Figure 2C). Eggshell strength linearly increased (P < 0.05) with dietary ME levels (Table 2; Figure 2D) but was not influenced by the number of beak trimmings (P > 0.05). There were significant isolated effects (P > 0.05) of dietary ME levels and beak trimming on total
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ME2 kcal ME/kg
5
ENERGY AND BEAK TRIMMING in LAYER HENS
115 110 105 100 95 2600
2700
2800
2900
3000
(B) Feed convertion ratio per dozen eggs
y = -0.000027x + 0.1826 R² = 0.5463 p=<0.0001
Metabolizable Energy (kcalME/kg)
1.55 1.50 1.45 1.40 1.35 1.30 1.25 1.20 1.15 1.10 2600
y = -0.0003x + 2.2144 R² = 0.4328 p<0.0001
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Feed convertion ratio per egg mass
(C) y = -0.0004x + 2.9628 R² = 0.4208 p<0.0001
2.10 2.00 1.90 1.80 1.70 1.60 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg) Figure 1. (A) Feed consumption of white laying hens fed with increasing levels of metabolizable energy. (B) Feed conversion per dozen eggs of white laying hens fed with increasing levels of metabolizable energy. (C) Feed conversion per egg mass of white laying hens fed with increasing levels of metabolizable energy.
Table 3. Quality of white laying hens’ eggs fed with 5 levels of metabolizable energy submitted to 1 or 2 beak trimming. Variables Effects1
WG (g)
AH (mm)
CL
HU
EST (kgf)
ME2 kcal ME/kg
2,600 2,700 2,800 2,900 3,000
61.233 61.814 61.308 61.256 61.220
7.737 7.713 7.822 7.765 7.867
5.496 5.618 5.658 5.533 5.477
87.295 86.922 87.704 87.412 88.010
4.971 4.985 5.136 5.201 5.250
Beak Trimm.3
1 2
61.571x 61.161z
7.801 7.760
5.585x 5.527z
87.543 87.394
5.079z 5.139x
SEM4
0.107
0.022
0.016
0.141
0.024
Source of variation ME Beak Trimm.3 ME × Beak Trimm.
0.299 0.047 0.058
0.152 0.342 0.016
0.121 0.581 0.039
< 0.001 0.155 0.404
Probability 0.001 0.045 0.530
1 WG, egg weight (g); AH, albumen height (mm); CL, yolk color; HU, Haugh units; EST, eggshell strength (kgf) 2 ME, metabolizable energy 3 Beak Trimm., beak trimming 4 SEM, standard error. x-z Means with different letter in columns differs statistically.
cost. Dietary ME levels linearly increased total cost (Figure 3A). Moreover, total production cost per hen was significantly higher when hens were beak-trimmed only once compared with the cost obtained when hens were beak-trimmed twice (Table 4). Gross margin was influenced (P < 0.05) both by dietary ME levels and number of beak trimmings.
Gross margin decreased linearly as dietary ME levels increased (Figure 3B), whereas higher gross margin was obtained when hens were beak-trimmed twice. The group of birds doubled had a higher gross margin of egg commercialization. The ratio between total production cost and total revenue was linearly reduced (P < 0.05) as dietary ME
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Feed intake (g)
(A)
6
GRANGHELLI ET AL.
(A)
y = 0.0008x + 5.4459 R² = 0.358 p<0.0001
Yolk color
8.00 7.80 7.60 7.40 7.20 2600
2700
2800
2900
y = -0.0000037x2 + 0.0207x - 23.194 R² = 0.2046 p<0.0001
5.90 5.70 5.50 5.30 5.10 2600
3000
(C) Haugh Units
y = 0.0049x + 73.776 R² = 0.2987 p=0.0003
89.00 87.00 85.00
2700
2800
2900
Eggshell Strenght (kgf)
(D)
91.00
83.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Metabolizable Energy (kcalME/kg)
y = 0.0008x + 2.9434 R² = 0.2602 p<0.0001
5.50 5.25 5.00 4.75 4.50 2600
3000
Metabolizable Energy (kcalME/kg)
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
Figure 2. (A) Albumen height of eggs of white laying hens fed with increasing levels of metabolizable energy. (B) Yolk color of eggs of white laying hens fed with increasing levels of metabolizable energy. (C) Haugh unit of eggs of white laying hens fed with increasing levels of metabolizable energy. (D) Eggshelll strength of white laying hens fed with increasing levels of metabolizable energy.
(B)
(A) y = 0.0037x + 8.6052 R² = 0.3074
20.50
Gross Margin($)
Treatment cost ($)
21.00 20.00 19.50 19.00 18.50 18.00 17.50 17.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalEM/kg)
(C)
TC to TR ratio
1.05
y = -0.0041x + 13.126 R² = 0.2975
4.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -0.50 -1.00 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg)
y = 0.0002x + 0.3649 R² = 0.2996
1.00 0.95 0.90 0.85 0.80 2600
2700
2800
2900
3000
Metabolizable Energy (kcalME/kg) Figure 3. (A) Treatment cost of white laying hens fed with increasing levels of metabolizable energy. (B) Gross margin of eggs of white laying hens fed with increasing levels of metabolizable energy. (C) TC to RT ratio of eggs of white laying hens fed with increasing levels of metabolizable energy.
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Albumen Height (mm)
8.20
(B)
7
ENERGY AND BEAK TRIMMING in LAYER HENS Table 4. Indicators of the economic productivity of white laying hens. Variables Effects1
TC (US$)
TR (US$)
GM (US$)
TC/TR (US$)
2,600 2,700 2,800 2,900 3,000
5.296 5.425 5.598 5.628 5.733
6.04 6.04 6.02 6.09 6.02
0.744 0.621 0.410 0.363 0.275
0.870 0.890 0.930 0.940 0.950
Beak Trimm.3
1 2
5.733x 5.340z
6.04 6.04
0.278z 0.689x
0.950x 0.880z
0.105
0.034
0.119
0.005
Probability 0.343 < 0.001 0.930 < 0.001 0.102 0.063
< 0.001 < 0.001 0.065
SEM Source of variation ME Beak Trimm.3 ME × Beak Trimm
< 0.001 < 0.001 0.066
1 TC, Treatment cost (US$); TR, total revenue (US$); GM, gross margin (US$); TC/TR, TC to RT ratio (US$). 2 ME, metabolizable energy 3 Beak Trimm., beak trimming x-z Means with different letters in superscript in columns differs (P < 0.05).
level increased (Figure 3C). In addition, higher TC/TR ratio (P < 0.05) was obtained when hens were beaktrimmed twice (Table 4).
DISCUSSION In the present study, dietary ME levels did not affect egg production, as previously observed by Peguri and Coon (1991) and Ost and Peixoto (1998), when layers were fed ME levels of 2,645 to 2,971 and 2,650 to 2,950 kcal/kg of feed, respectively. These results indicate that layers are able to adapt to different nutritional, environmental, and management conditions, maintaining their egg production. On the other hand, Xavier and Peixoto (1997) observed an increased egg production only when intermediate ME levels (2,750 and 2,850 kcal/kg of feed) were fed to layers, suggesting that the efficiency of dietary energy utilization for egg production is reduced at higher energy levels (Peguri and Coon, 1991). These findings support the recommendation of 2,800 kcal ME/kg for layers proposed by Rostagno et al. (2011). The linear reduction of feed intake as ME levels increased in the present study was also observed by Latshaw et al. (1990), Peguri and Coon (1991), and Wu et al. (2005). This result was expected, as layer feed intake is regulated by dietary energy levels and it is inversely proportional to dietary ME levels. According to Wu et al. (2005), feed intake is reduced in 1% for every 39 kcal/kg increase in dietary ME content. On the other hand, the higher feed intake observed when hens were beak-trimmed once (5mm of nostrils) may be related to their higher beak size (7 mm of nostrils), and consequently their better feed prehension. Glatz (2003) observed that hens with larger beaks consume more feed than those with smaller beaks. Ara´ ujo et al. (2005) also determined higher feed intake when
layers were beak-trimmed once compared with those beak-trimmed twice. The worse feed conversion obtained when hens were beak-trimmed once may be possibly due to the higher selectivity of the feed particles, which may have influence their nutrient balance. In addition, when pecking the feed during selection, part of the feed is thrown out the feeders, which contributes to increase feed waste (Ara´ ujo et al., 2005), consequently leading to an overestimation of feed intake, when calculated as feed offer minus feed residues in the feeders. The FCR per dozen eggs and per egg mass results obtained are consistent with the hypothesis of feed waste, as no difference in egg production was observed between hens beak-trimmed once or twice. The linear improvement in FCR per dozen egg and per egg mass as dietary ME levels increased may be explained by the higher dietary inclusion of lipids. Soybean oil has an extra caloric effect and reduces feed passage rate in the gastrointestinal tract, increasing nutrient utilization and, therefore, feed conversion ratio (Bertechini, 1998). Danicke et al. (2000) observed better FCR with increasing inclusion levels of soybean oil in layer diets up to a maximum inclusion level of 10%. On the other hand, the results of the present study differ from those of Xavier and Peixoto (1997) and Ost and Peixoto (2000), who obtained better FCR when layers were fed intermediate ME levels (2,750 and 2,850 kcal/kg, respectively) and worse FCR at extreme ME levels (2,650 and 2,950 kcal ME/kg) were fed. Albeit statistically different, the eggs of the hens beak-trimmed once were only 0.4 g heavier than those beak-trimmed twice, and both groups reached the desired egg weight of about 60 g. Pizzolante et al. (2007), evaluating 3 lengths of beak trimming in laying quails, also determined slightly lower egg weight when half of the beak was trimmed compared with no beak trimming and one-third of the beak trimmed. Possibly, the
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ME2 kcal ME/kg
8
GRANGHELLI ET AL.
terial were changed. This result shows that, although feed intake was significantly reduced as dietary ME levels increased, feed cost was not reduced. In fact, a total production cost difference of USD 0.437 was calculated between the group fed the highest (3,000 kcal ME/kg of feed) and the lowest (2,600 kcal ME/kg of feed) energy level. In the study of Rabello et al. (2007), feed cost increased in USD 0.031 with the inclusion of 4% of soybean oil compared with a diet with no soybean oil. Ribeiro et al. (2013) determined a USD 0.52 increase in the production cost of egg carton (30 dozen eggs) when dietary ME levels increased from 2,700 to 3,000 kcal/kg. The absence of effects of ME levels and beak trimming on total revenue may be attributed to the fact that egg production was not influenced by either factor. On the other hand, the gross margin obtained with egg sales was influenced by the treatments. The difference in the gross margin between the lowest level (2,600 kcal ME/kg) and the highest (3,000 kcal ME/kg) dietary energy level was USD 0.469 per hen, in agreement with the findings of Santos et al. (2011), who compared 2 dietary oil inclusion levels (2 and 4%) and also obtained higher gross margin with the lower oil inclusion. The analysis of the effect of beak trimming on the gross margin showed higher gross margin (+USD 0.411) and higher profitability (total cost/total revenue) when hens were beak-trimmed twice, which may be explained by their higher feed intake compared with those beak-trimmed once. These findings suggest that feed or dietary nutrients were wasted (Blokhuis et al., 1987) due to the possible greater feed selection by the hens beak-trimmed once. These results are in agreement with the findings of Davis et al. (2004), who demonstrated that beak trimming reduced feed cost and increased net profit, because beak-trimmed hens showed better feed utilization or lower feed waste. The findings of the present study indicate that if only egg production and egg quality results were taken into account, higher dietary ME levels would be recommended due to their positive influence on layer performance and egg quality, as well as beak trimming hens only once, as it did not compromise their performance and egg quality. In addition, the second beak trimming would not be required, complying with animal welfare requirements of minimizing stress and trauma. However, the economic analysis completely changed the scenario. Feed cost increased and profitability decreased as dietary ME levels increased. In addition, when hens are beak-trimmed only once, there is greater feed particle selection and feed waste, resulting in higher total production cost and a marked reduction in profitability. Therefore, from the economic point of view, it is recommended to beak-trim layers twice due to production cost savings.
REFERENCES Almeida, V. R., A. N. Dias, C. F. D. Bueno, F. A. P. Couto, P. Rodrigues, W. C. L. Nogueira, and D. E. Faria Filho. 2012. Crude
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hens beak-trimmed once were able to select feed particles which nutrients allowed increasing egg weight. The linear increase in albumen height and Haugh units as a function of increasing dietary ME levels observed in the hens beak-trimmed once supports this hypothesis. Poultry are able to select feed particle due to the presence of mechanoreceptors in the beak, which explains their preference for large feed particles (Schiffman, 1968; Gentle, 1979). When beak trimming is not too severe, these mechanoreceptors are partly preserved, allowing particle selection (Freire et al., 2011). The lack of influence of dietary ME levels on egg weight was also observed by Valkonen et al. (2008). A possible explanation is that the dietary protein level supplied the hens’ requirements. In addition, according to NRC (1994), egg weight increase is related to high linoleic acid rather than to high total lipid levels in the diet. It should be noted that the level of this fatty acid remained constant in all experimental diets. The increase in yolk color intensity up to the level of 2,800 kcal EM/kg of feed is consistent with the findings of Gunawardana et al. (2008) evaluating increasing ME levels in layer hens’ diets. This result is related to the better absorption of fat-soluble yolk pigments (xanthophylls) when hens are fed diets with high oil or fat levels. The reduction in yolk color intensity observed at 2,800 kcal ME/kg of feed may be attributed to the low feed intake of the hens fed this ME level, and therefore their low intake of corn, which is one of the main sources of pigments responsible for yolk color. Hens beak-trimmed twice showed, on average, lower yolk color intensity than those beak-trimmed once, which also suggests the selection of larger particles such as corn, which is rich in xanthophylls (Amerah et al., 2007). The observed increasing eggshell strength results may be explained by the reduction of heat increment as dietary oil addition increases (Daghir, 2008), allowing better nutrient utilization by the hens, as the present experiment was carried out during a season when high average temperatures (>25◦ C) are recorded in the region (UNICAMP, 2018). The total cost obtained for the group beak-trimmed once was USD 0.393 higher than that of the group beaktrimmed twice. This result may be due to the higher feed intake or feed waste of hens’ beak-trimmed one. In the study of Davis et al. (2004), layers not submitted to beak trimming presented higher feed intake than beaktrimmed layers. Those authors demonstrated that beak trimming reduced feed cost and increased net profit, because beak-trimmed hens showed better feed utilization or lower feed waste. Regarding the economic evaluation, the linear increase of feed cost as dietary ME levels increased was expected, as soybean oil was gradually added to the diets with the purpose of increasing dietary energy density. Therefore, the feed cost increased as a function only of oil inclusion, as all other nutrients remained constant and only the proportions of oil and inert ma-
ENERGY AND BEAK TRIMMING in LAYER HENS
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