A 51-Week Egg Production Assessment with White Leghorn Hens Fed on a 400 kcal AME_n/kg Range (2,850 to 2,550)

ABSTRACT

Energy is a key determinant of feed intake regulation, nutrient utilization, and egg production in laying hens, but the long-term effects of gradual reductions in dietary metabolizable energy remain poorly understood. This study evaluated the impacts of graded decreases in apparent metabolizable energy corrected for nitrogen (AME_n; 2,850, 2,750, 2,650, and 2,550 kcal/kg) on performance and egg quality of Bovans White hens from 25 to 76 weeks of age. Ninety-six hens were allocated to a completely randomized design with four treatments and 12 replicates of two birds each. Data were analyzed using SAS 9.4 (p<0.05). Progressive AME_n reductions had significant effects on performance, with linear decreases in body weight, egg weight, egg mass, and daily energy intake, accompanied by compensatory increases in feed intake. Egg production and feed conversion ratio showed quadratic responses, with optimal values estimated at 2,733 and 2,842 kcal/kg, respectively. Lower AME_n diets also reduced yolk, albumen, and shell weights, although eggshell thickness increased. Overall, hens on the lowest AME_n diet mobilized body reserves to maintain egg output, leading to body weight loss and reduced laying persistency. These findings demonstrate that dietary AME_n from 2,733-2,750 kcal/kg supports optimal production and egg quality, while further reductions compromise long-term performance.

Keywords:
Laying hen; metabolizable energy; performance; egg quality

INTRODUCTION

Energy is required for all physiological processes, including growth, reproduction, body temperature regulation, metabolic activities and synthesis of egg components. However, daily energy intake by laying hens in commercial settings should be optimized with feeds that are able to maintain egg production. Daily energy required by laying hens depends on body weight (BW), age, laying rate, and environment (Sakomura, 2004; Barzegar et al., 2020; Jehl et al., 2020).

Laying hens are very effective at adjusting feed intake (FI) to meet their daily energetic requirements, and within practical formulation ranges, a reduction in dietary energy density is generally compensated by an increase in FI. (Emmans, 1981; Wu et al., 2005). Consequently, energy supply is often considered the primary driver of FI, with direct implications for nutrient utilization, feed conversion ratio (FCR), and egg production efficiency (Leeson & Summers, 2005; Gao et al., 2025).

When dietary energy is insufficient, hens tend to mobilize body reserves to sustain production, which may compromise body weight and long-term laying persistency (Jehl et al., 2019; Gao et al., 2025). On the other hand, excessive dietary energy intake can promote abdominal fat deposition, fatty liver hemorrhagic syndrome, and the production of oversized eggs, which become less desirable in later phases of the cycle (Harms et al., 2000; Anene et al., 2023). Therefore, both deficiencies and excesses in energy supply have detrimental effects on productivity and egg quality.

Practical recommendations for apparent metabolizable energy corrected for nitrogen (AME_n) in feeds for laying hens during egg production range from 2,760 to 2,880 kcal/kg (NRC, 1994; Hendrix, 2020; Hy-line, 2023). Fat addition in feeds is frequently needed to ensure that minimum dietary linoleic acid contents meet the requirements to sustain egg production and adequate egg weights (Jensen et al., 1958; Guenter et al., 1971; Scragg et al., 1987). Supplemental fats to provide linoleic acid, such as the most common vegetable oils, may eventually lead to an increase in dietary AME_n.

Egg quality is also directly influenced by energy supply. Lower dietary energy levels have been associated with reductions in yolk and albumen weight, indicating limited deposition of lipids and proteins necessary for yolk development (Wu et al., 2005; Anene et al., 2023). In addition, the interaction between dietary energy and hen age is crucial: as hens age, yolk proportion increases and shell thickness decreases, both of which may be exacerbated or mitigated by dietary energy levels (Noetzold et al., 2022a, 2022b).

Despite the importance of energy, relatively few studies have evaluated the long-term effects of gradually reducing dietary AME_n in laying hens. Most available research has been limited to short-term trials or has not considered the adaptive responses of birds over extended cycles (Costa et al., 2009; Kim & Kang, 2022). Understanding how hens adjust FI, nutrient utilization, and egg quality under progressive energy restriction is essential, especially as alternative feedstuffs with lower energy density and higher fiber content are increasingly used in commercial formulations (Han et al., 2020).

The present research was conducted to evaluate the overall performance indicators of Bovans White laying hens fed on graded decreases in AME_n, starting from the usual AME_n contents in practical Brazilian feeds. It was hypothesized that by progressively reducing dietary AME_n, laying hens would adapt by adjusting their FI while maintaining production performance.

MATERIALS AND METHODS

All procedures followed in the present study were approved by the Ethics and Research Committee of the Federal University of Rio Grande do Sul, Porto Alegre, under project number 40247.

Hen Management

Ninety-six Bovans White laying hens were obtained from a commercial breeder farm (Mercoaves Comércio de Aves Ltda, Bom Princípio, RS, Brazil) at 18 weeks of age. Upon arrival, hens were individually weighed, and their body weight variation coefficient (CV = ±5%) was calculated. They were then randomly allocated in pairs into experimental cages (0.33 m length × 0.46 m width × 0.40 m height), ensuring that the CV was respected.

The study followed a completely randomized design with four treatments, each with 12 replicates of 2 hens, totaling 48 experimental units in an open-house facility. The metal cages were equipped with one stainless-steel nipple drinker and one plastic trough feeder (0.30 m length × 0.10 m depth × 0.10 m height). Lighting was provided for 16 h light:8 h dark (16L:8D) throughout the study, and environmental temperature was maintained to ensure bird comfort according to the lineage guide (Hendrix, 2020). The study was carried out in the central region of Rio Grande do Sul, Brazil, which has a humid subtropical climate (Cfa, Köppen-Geiger).

Experimental Diets and Study Design

Experimental feeds were based on corn, soybean meal (SBM), full-fat soybean, and wheat bran. Diets were formulated isoaminoacidically to ensure that only the AME_n level varied among treatments (2,850; 2,750; 2,650; and 2,550 kcal/kg), mainly through adjustments in full-fat soybean and wheat bran inclusion. Ingredients were mixed in a 500 kg capacity horizontal mixer, and feed samples were collected at every period from each batch and stored at −20 °C for further analyses. During the adaptation period (18 to 24 weeks of age), hens were given ad libitum access to a common feed (2,750 kcal AME_n/kg, 17.2% crude protein [CP], 4.0% Ca, and 0.48% available P). The experimental diets (Table 1) were provided from 25 to 76 weeks of age, with the laying phase I ranging from 25 to 48 weeks (CP: 17.0%, Ca: 4.2%, and Av.P: 0.69) and laying phase II from 49 to 76 weeks (CP: 15.5%, Ca: 4.4%, and Av.P: 0.61). Evaluations were conducted over 13 periods of 28 days each.

Table 1
Composition of feeds with graded decreases in AME_n supplied to White Leghorn laying hens from 25 to 76 weeks of age.

Ingredients	Laying I (25 to 48)				Laying II (49 to 76)
	2,850	2,750	2,650	2,550	2,850	2,750	2,650	2,550
Corn	54.98	57.54	57.49	53.70	56.05	50.33	58.95	47.15
Soybean meal	10.72	18.43	23.60	24.19	5.50	4.00	18.50	10.22
Wheat bran	-	-	2.00	8.19	2.79	10.39	4.80	18.00
Full fat soy	21.39	11.11	4.00	1.00	21.96	21.60	4.00	10.94
Limestone	10.18	10.20	10.23	10.32	10.96	11.06	11.02	11.18
Dicalcium phosphate	1.84	1.84	1.80	1.67	1.52	1.36	1.49	1.19
Salt	0.42	0.42	0.42	0.42	0.41	0.41	0.42	0.41
Vitamin-mineral mix1	0.30	0.30	0.30	0.30	0.30	0.30	0.30	0.30
DL-Methionine 99%	0.16	0.15	0.15	0.16	0.17	0.17	0.17	0.18
L-Lysine 78%	-	-	-	0.04	0.12	0.14	0.13	0.18
L-Threonine 98%	0.01	0.01	0.01	0.01	0.05	0.07	0.06	0.08
Choline chloride	0.11	0.11	0.11	0.11	0.12	0.12	0.12	0.12
Total	100.00				100.00
Formulated composition, % as-is3
AMEn, kcal/kg2	2,850	2,750	2,650	2,550	2,850	2,750	2,650	2,550
Crude protein	17.00 (17.6±0.20)	17.00 (17.5±0.33)	17.00 (17.8±0.12)	17.00 (17.9±0.73)	15.5 (15.4±0.15)	15.5 (15.7±0.23)	15.5 (15.6±0.31)	15.5 (15.7±0.27)
Ca	4.20 (4.34±0.23)	4.20 (4.39±0.28)	4.20 (4.43±0.15)	4.20 (4.20±0.08)	4.40 (4.43±0.21)	4.40 (4.47±0.17)	4.40 (4.51±0.14)	4.40 (4.49±0.31)
Av. P	0.42				0.37
Total P	0.69 (0.67±0.03)	0.69 (0.66±0.05)	0.69 (0.66 ± 0.05)	0.69 (0.68±0.04)	0.61 (0.68±0.08)	0.61 (0.59±0.21)	0.61 (0.63±0.09)	0.61 (0.55±0.15)
Crude fat	4.54	3.71	3.71	2.89	4.64	4.61	3.19	3.75
Linoleic acid	4.11	3.01	3.01	2.50	3.22	3.18	1.70	2.28
Na	0.18
Dig. Lys	0.82				0.80
Dig. TSAA	0.65				0.62
Dig. Thr	0.56				0.55
Dig. Trp	0.18				0.16
Dig. Arg	1.03				0.91
Dig. Val	0.77	0.74	0.73	0.71	0.70	0.68	0.65	0.64

• ¹
  Supplied the following per kg of feed: Cu, 15 mg; Zn, 110 mg; Fe, 50 mg; Se, 0.3 mg; I, 2 mg; vitamin A, 12,000 IU; vitamin D3, 3,000 IU; vitamin E, 100 IU; vitamin K3, 6mg; vitamin B12, 40 mg; thiamine, 3.5 mg; riboflavin, 16 mg; vitamin B6, 6 mg; niacin,40 mg; pantothenic acid, 25 mg; folic acid, 4 mg; biotin, 0.3 mg.
• ²
  Recovered value of 2,850, 2,750, 2,650 and 2,550 kcal AME_n/kg were Laying I were 2,886, 2,747, 2,654 and 2,561kcal AME_n/kg, Laying II were 2,859, 2,787, 2,648 and 2,571kcal AME_n/kg, respectively.
• ³
  Values within parenthesis are analyzed (n = 13 samples of each treatment).

Performance and Egg Quality Evaluation

The laying hens’ BW was recorded at the end of each experimental period. Eggs were collected four times per day (08:30 am, 11:00 am, 2:00 pm, and 4:00 pm), and once a week all eggs laid on the same day were weighed. FI (g/bird/day) and daily energy intake were determined at the end of each period. Hen-day egg production was calculated as (total eggs produced ÷ hen-days) × 100. FCR was expressed as kilograms of feed consumed per kilogram of eggs produced and per dozen of eggs laid.

Egg quality was evaluated at 36, 48, 60, and 72 weeks of age using 30 eggs per treatment, collected over two consecutive days. Albumen weight was calculated by subtracting yolk and shell weights from egg weight. Percentages of yolk, albumen, and shell were expressed relative to total egg weight. Eggshells were washed with filtered water, dried at 105 °C for 24 h, and weighed. Shell thickness was measured three times at the equatorial region using a digital micrometer (Model IP65; Mitutoyo Corp., Kawasaki, Japan), and the average value was used for statistical analysis.

AME _n Determination

An assay to determine the AME_n of the treatment feeds was conducted during the last three days of the trial. A pool of feeds provided throughout the study, previously stored at -20 ^oC, was mixed and added with 1% insoluble marker (Celite, Celite Corp., Lompoc, CA). Each had been provided for three days with the corresponding excreta collected twice daily on aluminum foil trays. Excreta was pooled by cage and stored at -20 ºC for dry matter (DM) analysis, which was carried out after drying the samples at 105 °C for 16 hrs (AOAC International, 2006). Excreta and feed samples were analyzed for gross energy (GE) using a calorimeter calibrated with benzoic acid as the standard (IKA Werke, Parr Instruments, Staufen, Germany). Calculations of AME_n were subsequently performed. Acid insoluble ash in excreta and diets were determined as described by Vogtmann et al. (1975) and Choct & Annison (1992). Calculations of AME_n were made considering AME (kcal/kg) = GEi − [GE × (Mi /Mo )], where Mi represents the concentration of acid insoluble ash in the diet in grams per kilogram of DM; Mo represents the concentration of acid insoluble ash in the excreta in grams per kilogram of DM output; Ei represents the concentration of DM, CP, and GE in the diet in milligrams per kilogram of DM; and Eo represents the concentration of DM, CP, GE, in the excreta and in milligrams per kilogram of DM (Kong & Adeola, 2014) . The calculated AME was corrected to zero N retention using a factor of 8.22 kcal/g (Hill & Anderson, 1958). Total feed consumption was determined from the difference obtained between feed offered and left per cage.

Statistical Analysis

Data were submitted to the normality of variance test, to check for normal distribution, and the homogeneity of variance test (Levene, 1960; Shapiro & Wilk, 1965). A variance analysis was performed using the PROC MIXED model procedure of SAS with effect of diets and periods and their interactions, using the repeated statement of SAS 9.4 (2015). The best covariance structure was determined based on the Akaike information criteria (Littell et al., 1998). The Tukey-Kramer test was used for means comparison, where differences were considered significant at p<0.05 (Tukey, 1991). Regression analyses were tested for the effects of dietary AME_n with linear (L) and quadratic (Q) models.

RESULTS

Feed formulations as well as CP, GE, Ca and P analyses are presented in Table 1. Feed AME_n contents evaluated at the end of the experiment were 2,866, 2,727, 2,632, 2,532 kcal AME_n/kg, which were acceptable for the planned experimental assessment since they were close to the expected values of 2,850, 2,750, 2,650, 2,550 kcal AME_n/kg (Table 1). Overall, there were no interactions between dietary AME_n and period on the evaluated responses (p>0.05).

Performance results are presented in Table 2. There were treatment effects on all performance data evaluated (p<0.05). Regression analyses showed that dietary AME_n had linear relationships with BW, daily AME intake, egg weight, egg mass, and FI as follows: BW = Y = 891.95351 + 0.26973x, R² 0.0907, p<0.001; daily kcal intake = 174.75915 + 0.04790x R² = 0.1176, p<0.001; egg weight = 45.09732 + 0.00632 x, R² = 0.0618, p<0.001; egg mass = 39.38019 + 0.00744x; R² = 0.0395; p<0.001; FI = 165.41294 - 0.1968x; R² = 0.1176, p<0.001. The reduction in dietary AME_n led to quadratic responses for total egg production and FCR (kg/dozen) as follows: total eggs produced = - 242.8669422 + 0.2484120x - 0.0000455x2, R² = 0.0098, p<0.0497; FCR = 9.567823249 - 0.005763746x + 0.000001014x2, R² = 0.1045, p<0.001. Linear effects of dietary AME_n showed that, for every 100 kcal reduction, hens had a 30 g decrease in body weight, a 2.2 g increase in feed intake, a 5.3 kcal decrease in daily energy intake, and reductions of 0.7 g in egg weight and 0.8 g in egg mass. Quadratic adjustments showed that the highest egg production occurred when hens were fed 2,733 kcal/kg AME_n., with a maximum hen day egg production of 96.2% or a total of 350 eggs per hen in the 51 week cycle. FCR was optimized at 2,842 kcal/kg AME_n, with an FCR of 1.377 kg/dozen.

Table 2
Performance and egg characteristics of White Leghorn laying hens fed on graded decreases of AME_n from 25 to 76 weeks of age.

AMEn, kcal/kg1	BW	Daily Intake		Egg weight	Egg mass	Hen/d egg production	Total eggs3	FCR
	g	g	Kcal2	g		%	Units/hen	kg/kg	kg/dozen
2,850	1,656	110b	313a	63.2a	61.1a	96.5ab	351ab	1.799c	1.364b
2,750	1,638	111b	305ab	62.2ab	60.3a	96.9ab	352a	1.851bc	1.378b
2,650	1,602	114ab	302bc	61.7ab	60.1ab	97.1a	353a	1.896b	1.404b
2,550	1,568	116a	296c	61.0b	57.8b	94.9b	345b	1.996a	1.460a
Periods, wks
25 - 28	1,553f	102a	276c	57.2f	51.7c	90.4f	-	1.978ª	1.355cd
29 - 32	1,570ef	112b	302ab	60.7c	60.0ab	98.9a	-	1.881bc	1.361d
33 - 36	1,602d	113ab	305ab	61.8cde	60.6ab	98.2abc	-	1.875bc	1.386bcd
37 - 40	1,639bc	112ab	303ab	62.3bc	61.4a	98.7ab	-	1.836c	1.369cd
41 - 44	1,655ab	113ab	305ab	60.9de	59.0b	96.8bcd	-	1.926ab	1.405abcd
45 - 48	1,599de	115ab	310ab	62.4bc	60.2ab	96.5abcde	-	1.912abc	1.431ab
49 - 52	1,605de	114ab	307ab	62.6bc	60.8ab	97.2abcd	-	1.880bc	1.411abc
53 - 56	1,626bcd	114ab	308ab	63.3ab	61.9a	97.9abcd	-	1.847bc	1.400abcd
57 - 60	1,611cd	114ab	307a	63.1bc	60.8ab	95.9abcde	-	1.846bc	1.398abcd
61 - 64	1,620bcd	112b	303b	62.2bcd	60.6ab	97.1cd	-	1.854bc	1.390bcd
65 - 68	1,679a	115a	310a	63.2b	60.2ab	95.4de	-	1.915ab	1.449ª
69 - 72	1,620bcd	113ab	305ab	62.6bc	58.9b	93.8e	-	1.898bc	1.425ab
73 - 76	1,599de	114ab	309ab	64.4a	61.6a	95.8cde	-	1.868bc	1.441a
SEM	4.561	0.285	0.741	0.127	0.164	0.193	0.688	0.006	0.004
Probability 4, 5
AMEn	0.0636	0.0034	0.0004	0.0425	0.0088	0.0459	0.0435	<0.0001	<0.0001
Period	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001	-	<0.0001	<0.0001
AMEn*Period	0.1085	0.1620	0.2843	0.8313	0.0743	0.0704	-	0.0509	0.0522

• ^a-f
  Means with different letters in the same column indicate significant differences (p<0.05).
• ¹
  Recovered value of 2,850, 2,750, 2,650 and 2,550 kcal AME_n/kg were Laying I were 2,886, 2,747, 2,654 and 2,561kcal AME_n/kg, Laying II were 2,859, 2,787, 2,648 and 2,571kcal AME_n/kg, respectively.
• ²
  Intake/hen/day*feed kcal AME_n/1,000.
• ³
  Total eggs set at the end of 13 periods of 28 days.
• ⁴
  Body weight = Y = 891.95351 + 0.26973x, R² 0.0907, p<0.001; daily kcal intake = 174.75915 + 0.04790x R² = 0.1176, p<0.001; egg weight = 45.09732 + 0.00632 x, R² = 0.0618, p<0.001; egg mass = 39.38019 + 0.00744x; R² = 0.0395; p<0.001; daily feed intake = 165.41294 - 0.1968x; R² = 0.1176, p<0.001.
• 5 Total eggs produced = - 242.8669422 + 0.2484120x - 0.0000455x², R² = 0.0098, p<0.0497; FCR = 9.567823249 - 0.005763746x + 0.000001014x², R² = 0.1045, p<0.0001

The egg composition results are summarized in Table 3. Effects of AME_n were found for all evaluated variables (p<0.05), except for the percentages of albumen and eggshell (p>0.05). Conversely, period affected all responses (p<0.05), except for albumen percentage (p>0.05). Reducing AME_n led to decreases in yolk, albumen and eggshell weights, while eggshell thickness increased (Yolk = 10.910000 + 0.00214x, R² = 0.0309, p<0.001; albumen = 25.32007 + 0.00515x, R² = 0.0370, p<0.001; eggshell = 4.14856 + 0.00070685x, R² = 0.0429, p<0.001; eggshell thickness = 446.97495 − 0.01632x, R² = 0.0131, p<0.001). These linear changes corresponded to reductions of 0.57 g, 0.24 g, and 0.07 g in albumen, yolk and eggshell weights, respectively; and an increase of 1.82 μm in eggshell thickness for every 100 kcal AME_n/kg reduction (p<0.05).

Table 3
Effects of diets with gradual decreases of AME_n on egg characteristics of White Leghorn laying hens from 25 to 76 weeks of age.¹

AMEn, kcal/kg2	Albumen	Yolk	Shell	Albumen	Yolk	Shell	Thickness
	g			%			μm
2,850	40.3a	17.3a	6.1a	63.2	27.2ab	9.6	390b
2,750	39.6ab	17.0a	6.1a	63.2	27.1ab	9.7	396b
2,650	39.0bc	17.0a	6.0b	63.0	27.3a	9.7	401a
2,550	38.8c	16.4b	5.9b	63.4	26.9b	9.7	402a
Periods, wks
36	38.4c	16.3c	6.1a	63.1	26.8c	10.1a	417a
48	39.1b	17.1b	6.1a	63.2	27.1ab	9.7b	399b
60	39.9a	17.0b	6.0a	63.2	27.1ab	9.7b	393c
72	40.3a	17.5a	5.9b	63.3	27.5a	9.2c	386d
SEM	0.102	0.042	0.013	0.064	0.059	0.021	0.070
Probability 3
AMEn	<0.0001	<0.0001	<0.0001	0.0767	0.0122	0.6087	0.0001
Period	<0.0001	<0.0001	<0.0001	0.7886	<0.0001	<0.0001	<0.0001
AMEn*Period	0.0701	0.0976	0.0825	0.1118	0.1031	0.0632	0.0836

• ^a-c
  Means with different letters in the same column indicate significant differences (p<0.05).
• ¹
  Samples = 30 eggs per treatment each period
• ²
  Recovered value of 2,850, 2,750, 2,650 and 2,550 kcal AME_n/kg were Laying I were 2,886, 2,747, 2,654 and 2,561kcal AME_n/kg, Laying II were 2,859, 2,787, 2,648 and 2,571kcal AME_n/kg, respectively.
• ³
  Yolk = 10.910000 + 0.00214x, R² = 0.0309, p<0.001; Albumen = 25.32007 + 0.00515x, R² = 0.0370, p<0.001; eggshell = 4.14856 + 0.00070685x, R² = 0.0429, p<0.001; eggshell thickness = 446.97495 - 0.01632x, R² = 0.0131, p<0.001

DISCUSSION

Progressively reducing the AME_n of feeds over a 51‐week period had a significant impact on both egg production and performance parameters. Although most responses exhibited predominantly linear trends, both total egg production and FCR followed quadratic patterns. These quadratic adjustments suggest that to optimize FCR and sustain egg production, hens require a slightly higher daily AME_n intake than that provided by the lowest energy diets.

The present study was in line with the expected feed intake increase as dietary energy decreased (Wu et al., 2005; 2007). However, this compensatory increase has physiological limits, as birds face constraints imposed by the bulk capacity of the gastrointestinal tract and metabolic regulation (Kyriazakis & Emmans, 1995; Nobrega et al., 2022).

The two highest dietary AME_n treatments resulted in increased daily egg production, higher egg weight, and greater body weight compared to lower energy treatments. These results highlight that long-term feeding of low-energy diets may adversely affect egg production, as hens fed lower AME_n diets appear to mobilize their energy reserves to maintain egg output, leading to reductions in body weight over time. Similarly, Gao et al. (2025) reported that insufficient dietary energy forces hens to mobilize body reserves, which compromises body weight and may impair long-term performance. Although our study terminated at 76 weeks of age, typical commercial white hen cycles extend to approximately 100 weeks, suggesting that the negative impacts on production observed with the lowest AME_n diets could be even more pronounced over an extended period.

Egg weight decreased linearly by 0.7 g for every 100-kcal reduction in dietary AME_n, a result similar to that reported by Harms et al. (2000), who observed an increase of 2.1 g in egg weight when comparing diets of 2,519 and 3,078 kcal AME_n/kg. Lowering dietary AME_n may therefore be a viable strategy to reduce egg weight from extra-large to large, potentially enhancing marketability in later production stages when oversized eggs become less desirable. According to Anene et al. (2023), excess nutrients not required for maintenance or egg production are stored as abdominal fat or incorporated into yolk solids, contributing to larger egg size. In addition, egg weight is also influenced by the body weight of the hens, as heavier hens tend to produce heavier eggs, a relationship confirmed by Ekinci et al. (2023), who reported a significant positive correlation (p<0.0001) between body weight and egg weight.

Total egg production per hen varied significantly among treatments, ranging from 345 to 353 eggs over the 51-week production period. Hens fed 2,650 kcal AME_n/kg achieved the highest productivity (353 eggs per hen), whereas those fed the lowest energy density (2,550 kcal AME_n/kg) produced only 345 eggs per hen. This reduction suggests that diets with AME_n below 2,650 kcal AME_n/kg may compromise egg-laying persistence due to an inadequate energy supply to meet the metabolic demands of continuous production (Bertechini, 1998). Lower energy availability likely affects both laying rate and feed conversion efficiency, as birds must allocate energy to maintenance functions at the expense of production (Sunder et al., 2008). Furthermore, reduced energy intake can impair the utilization of other critical nutrients such as proteins and minerals, which are essential for the synthesis and deposition of reserves that sustain production throughout the laying cycle (Hocking et al., 2002; Ribeiro et al., 2014).

In the context of growing interest in alternative raw materials such as high-fiber ingredients with lower energy density, mild reductions in dietary AME_n may be implemented without severely compromising performance. However, further investigation is needed to assess the long-term effects of fibrous, low-energy diets on nutrient digestibility and egg quality parameters. The selection of ingredients for layer diets should therefore consider both immediate production performance and the broader implications for egg characteristics.

In terms of egg quality, reducing the AME_n content negatively affects key egg components. A significant decrease was observed in the weights of the yolk, albumen, and shell. Yolk weight remained relatively constant at higher AME_n levels (2,850, 2,750, and 2,650 kcal AME_n/kg), averaging around 17.0 g, but exhibited a significant 5% reduction at the lowest AME_n level (2,550 kcal AME_n/kg). This decline indicates that lower caloric intake compromises the deposition of essential lipids and proteins required for optimal yolk development, in agreement with findings by Ribeiro et al. (2014). According to Anene et al. (2023), higher energy intake in hens allows excess fats not used for body maintenance or development to be stored as abdominal fat or incorporated into yolk solids, which is consistent with the observed reduction in yolk weight at lower AME_n levels. Interestingly, while eggshell weight decreased with lower AME_n, shell thickness remained unchanged, suggesting that the structural integrity of the eggshell was maintained despite reductions in overall shell mass.

As hens age, an increased yolk proportion is typically observed alongside a reduction in eggshell thickness, a trend associated with increased egg weight and higher daily caloric intake (McDaniel et al., 1981; Leeson & Summers, 2005; Noetzold et al., 2022a, 2022b).

In summary, the results of this study illustrate that optimizing dietary AME_n is critical for balancing productive performance and egg quality in laying hens. While higher AME_n levels improve production parameters such as egg weight and FCR, moderate energy levels (e.g., 2,650-2,750 kcal AME_n/kg) appear sufficient to sustain production and egg quality. Future research should focus on the long-term impacts of low-energy diets - especially those incorporating fibrous ingredients - on nutrient utilization and egg characteristics across extended production cycles.

CONCLUSION

Progressive reductions in dietary AME_n affected performance, egg production, and egg composition in Bovans White laying hens. Lower AME_n led to linear decreases in body weight, egg weight, egg mass, and yolk and albumen weights, while eggshell thickness increased. Quadratic responses indicated maximum total egg production at approximately 2,733 kcal AME_n/kg. Considering these responses, a dietary AME_n level of 2,733-2,750 kcal/kg is recommended for maintaining performance and egg quality in Bovans White hens under the conditions of this study.

ACKNOWLEDGEMENTS

The authors wish to thank Coordenacão de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Pesquisa (CNPq) for the support given to conduct the present research.

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• FUNDING
  No funding was received for this study.
• DATA AVAILABILITY STATEMENT
  Data will be available upon request.
• DISCLAIMER/PUBLISHER’S NOTE
  The published papers’ statements, opinions, and data are those of the individual author(s) and contributor(s). The editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.

Edited by

• Section Editor:
  Tatiana Carlesso dos Santos

Data availability

Data will be available upon request.

Publication Dates

• Publication in this collection
  16 Feb 2026
• Date of issue
  2025

History

• Received
  26 Sept 2025
• Accepted
  23 Nov 2025