Effects of feeding diets varying in energy and nutrient density to Hy-Line W-36 laying hens on production performance and economics

The influence of breed, dietary energy and lysine on laying persistency and body composition of laying hens

The effect of dietary energy and lysine levels on laying persistency and body composition in brown and white hens was studied. Dietary treatments with 2 Metabolizable Energy levels (ME lay; constant or reduction over time) and 2 apparent fecal digestible Lys levels (AFD Lys; constant or reduction over time), were fed to Lohmann white or brown hens, from 17 to 75 wk of age, in a 2 × 2 × 2 factorial design. Data were subjected to mixed model analyses. The egg production curve was modeled using a non-linear regression function. White hens showed an improved laying persistency and a higher number of total eggs per hen compared to brown hens, indicated by a shorter peak production phase but a significant lower slope of decline after peak (P < 0.05). Similarly, hensfed a reduced instead of a constant ME Lay diet had a better laying persistency, indicated by a shorter peak production phase and a significant smaller slope of decline after peak (P < 0.05). This improved laying persistency was probably related to a higher ADFI and nutrient intake of hens fed the reduced ME Lay diets (P < 0.05). A segmented regression analysis showed reasonable correlation between egg mass production and ME Lay intake, with an R2 adjusted of 0.78 for the overall model. The egg mass production was not increased for intakes above 330 kcal of ME Lay intake for white hens and 324 kcal for brown hens. Limited effects of dietary treatments on body crude fat and crude protein were found. Both energy and protein requirement seemed to increase over time, indicated by higher voluntary nutrient intake and a reducing body crude fat after wk 43 in all treatments. The egg mass production correlated poorly with the AFD Lys intake, with an R2 of 0.22. In conclusion, laying persistency was mostly influenced by breed and dietary ME Lay level, but not dietary AFD Lys level.

Effects of exogenous energy on synthesis of steroid hormones and expression characteristics of the CREB/StAR signaling pathway in theca cells of laying hen

Energy and the cAMP-response element binding protein (CREB)/steroidogenic acute regulatory protein (StAR) signaling pathway play important roles in steroid hormone production and follicular development in hens. This present study aimed to investigate the effects of exogenous energy on the synthesis of steroid hormones and the expression characteristics of the CREB/StAR signaling pathway in theca cells of laying hen. The primary theca cells of small yellow follicles were randomly divided into 6 treatments and cultured in medium with glucose concentrations of 1, 1.5, 3, 4.5, 6, and 7.5 mg/mL for 48 h. It was found that growth was robust and cell outlines were clear when cells were cultured with 1, 1.5, 3, and 4.5 mg/mL glucose, but cell viability was diminished and cell density decreased after exposure to glucose at 6 and 7.5 mg/mL for 48 h. Cell viability showed an increasing and then decreasing quadratic response to increasing glucose concentration in culture (r2 = 0.688, P < 0.001). The cell viability of theca cells cultured with 4.5 mg/mL glucose was greater than those cultured with 1, 1.5, 6, and 7.5 mg/mL glucose (P < 0.05). The concentration of estradiol in the medium containing 3 mg/mL glucose was higher than in medium containing 1, 1.5, and 6 mg/mL glucose (P < 0.05). There was an increasing and then decreasing quadratic correlation between progesterone concentrations and glucose concentrations (r2 = 0.522, P = 0.002). The concentration of progesterone in medium with 4.5 mg/mL glucose was higher than in medium with 1 and 7.5 mg/mL glucose (P < 0.05). There was an increasing and then decreasing quadratic correlation between the relative expression of CREB1 (r2 = 0.752, P < 0.001), StAR (r2 = 0.456, P = 0.002), CYP1B1 (r2 = 0.568, P < 0.001), and 3β-HSD (r2 = 0.319, P = 0.018) in theca cells of laying hens and glucose concentrations after treatment with different glucose concentrations for 48 h. After treatment with 4.5 mg/mL glucose, the expression of StAR, CYP1B1, and 3β-HSD genes were increased compared to treatment with 1, 1.5, 3, 6, and 7.5 mg/mL glucose (P < 0.001). There was an increasing and then decreasing quadratic correlation between glucose concentrations and protein expression of CREB1 (r2 = 0.819, P < 0.001), StAR (r2 = 0.844, P < 0.001), 3β-HSD (r2 = 0.801, P < 0.001), and CYP11A1 (r2 = 0.800, P < 0.001) in theca cells of laying hens. The protein expression of CREB1, StAR, and 3β-HSD in theca cells cultured with 4.5 mg/mL glucose was higher than in other groups (P < 0.001). The results indicate that the appropriate glucose concentration (4.5 mg/mL) can improve the synthesis of steroid hormones in theca cells of laying hens through the upregulation of key genes and proteins in the CREB/StAR signaling pathway.

Effects of lysolecithins on performance, egg quality, blood profiles and liver histopathology in late-phase laying hens

1. This study investigated the effects of lysolecithins (LL) on performance, egg quality, blood profiles, relative organ weight and liver histopathology in laying hens.2. A total of 480 healthy 65-week-old Lohmann laying hens were randomly allocated into four treatments in a 2 × 2 factorial arrangement design with two levels of energy (AMEn, 11.08 MJ/kg and 12.94 MJ/kg) and two levels of LL (0 and 0.05%).3. Birds fed high energy diets had lower (P < 0.05) average daily intake and feed conversion rate during weeks 0-4, 5-8 and 0-8, but higher (P < 0.05) average egg weight (AEW) during trial weeks 0-4. There was an interaction in (P < 0.05) AEW during trial weeks 0-14 and 0-8 for energy and LL. The high energy diets increased yolk colour at the end of weeks 2 and 4, while addition of LL increased albumen height at the end of week 2. There was an interaction (P < 0.05) in yolk colour between energy and LL at the end of week 2. There was an interaction (P < 0.05) in serum superoxide dismutase and LDL-C throughout the experiment.4. The high energy diets increased (P < 0.05) the relative weight of abdominal fat compared with low energy diets. The high energy diets increased (P < 0.05) liver ether extract content and liver pathological injury score compared with low energy diets at the end of week 8, while the addition of LL decreased (P < 0.05) liver pathological injury score.5. The supplementation of LL in high energy diets could alleviate some negative effects on liver injury in late laying hens.

Dietary metabolizable energy and crude protein levels affect the performance, egg quality and biochemical parameters of a dual-purpose chicken

Effects of dietary metabolizable energy (ME) and crude protein (CP) level on performance, egg quality and biochemical parameters were studied in a dual-purpose chicken-Beijing You Chicken (BYC) at peak laying period. A 3 × 3 factorial experiment was arranged, including 3 levels of dietary ME (11.31, 11.51, 11.71 MJ/kg) and 3 levels of dietary CP (14%, 15%, 16%). The results showed that dietary CP level alone and the interaction of ME by CP affected the total feed intake (TFI) during 27-30 wks, dietary ME level affected the mortality rate of 27-34 wks of age (p = 0.018), with the highest mortality rate found in 11.31 MJ/kg group (3.10%). The albumen height (AH), Haugh unit (HU) and egg grade (EG) of 16% group was higher than those in 14% and 15% groups (p < 0.05). Serum immunoglobulin G content in 11.31 MJ/kg group was lower than in 11.51 MJ/kg and 11.71 MJ/kg groups (p = 0.037). The present study suggested that dietary levels of 11.51 MJ/kg ME and 16.0% CP are enough to maintain the performance and egg quality of BYC at peak laying period. 11.31 MJ/kg ME increased the mortality of the chicken, which may be related to the decrease of the humoral immune function and antioxidative capability.

Research Note: Effect of increasing fat supplementation in diets on productive performance, egg quality, and fatty liver incidence in laying hens throughout the entire laying cycle

This study aimed to investigate the effect of increasing fat supplementation in diets on productive performance, egg quality, and fatty liver incidence in laying hens during the entire laying cycle. A total of three hundred eighty-four 18-wk-old Hy-Line Brown laying hens were randomly allotted to 1 of 3 dietary treatments with 8 replicates for a 52-wk feeding trial. Each replicate comprised 16 consecutive cages with 1 hen per cage. The experimental diets were prepared by supplementing 0, 1.5, or 3.0% tallow to a basal diet, but all nutrients and energy in 3 diets were formulated to be equalized according to the recommended nutrient and energy concentrations at each phase of laying hens. Results indicated that increasing fat supplementation in diets decreased (linear, P < 0.01) feed conversion ratio (FCR) by increased egg mass (linear, P < 0.05) but decreased feed intake (linear and quadratic, P < 0.05) in laying hens during overall periods. Increasing fat supplementation in diets decreased (linear and quadratic, P < 0.05) egg yolk color during overall periods. Increasing fat supplementation in diets had no effects on liver color and hemorrhagic score measured at 60 wk (phase 3) and 70 wk of age (phase 4) without affecting hepatic fat concentrations during overall periods. However, the relative abdominal fat weight in laying hens was increased (linear and quadratic, P < 0.05) during overall periods by increasing fat supplementation in diets. In conclusion, increasing fat supplementation up to 3.0% in diets improves FCR with no impacts on fatty liver incidence and economics in laying hens throughout the entire laying cycle.

High dietary energy decreased reproductive performance through increasing lipid deposition in Yangzhou geese at late laying stage

Dietary metabolizable energy (ME) level could offer a well production performance through maintaining lipid homeostasis in poultry. In this study, a total of 540 geese (450 females and 90 males) at 64 wk of age with similar body weight (4,600 ± 382) were randomly divided into 5 groups with 3 replicates in each group and 30 females and 6 males (1♂:5♀) in each replicate. After 2 wk adaptation, the 5 groups were designed to provide diet with ME intakes of 9.65, 10.05, 10.70, 11.45, and 11.75 MJ/kg, respectively, according to production requirement. Body weight, egg production, hatchability, blood lipid, and fat deposition were recorded after 6 wk feeding. The expression of lipid synthesis-related genes, lipoprotein lipase (LPL) and fatty acid synthase (FASN), were determined by quantitative real-time PCR. Geese fed with high ME diet of 11.75 MJ/kg caused an increased liver and abdominal fat weight and low hatchability of set eggs. The ovarian weight and oviduct length were higher in geese fed dietary energy of 10.7 MJ/kg as compared to the 9.65 MJ/kg groups, whereas no significant difference was observed in geese fed dietary energy of 10.05 MJ/kg. Dietary energy level did not change the concentration of serum lipids at the late egg laying stage. The LPL expression exhibited linear and quadratic effect in response to dietary ME. The FASN expression showed quadratic effect and a relatively higher expression was exhibited in 10.05 and 11.45 MJ/kg than that of the 9.65 and 10.70 MJ/kg ME groups. According to the productivity, reproductive performance, and fat deposition, dietary ME of 10.13 to 10.28 MJ/kg could be suggested for breeding geese at their late laying stage.

Effects of protease enzyme supplementation and varying levels of amino acid inclusion on productive performance, egg quality, and amino acid digestibility in laying hens from 30 to 50 weeks of age

An experiment was conducted to evaluate the effects of protease supplementation and reduced digestible amino acid (dAA)/ crude protein (CP) level on productive performance, AA digestibility, and egg quality parameters in Hy-Line W-36 laying hen from 30 to 50 wk of age. A total of 768 hens (12 replicates of 8 hens per treatment) were equally and randomly allocated into 8 experimental diets in a 4 × 2 factorial arrangement of dAA/CP level (100, 95, 90, and 85% of breeder recommendation) and protease (exclusion or inclusion). Protease was added at 60 g/metric ton of feed in the inclusion group. Hens were housed in raised-wire cages with a stocking density of 870 cm²/bird. The adequate (100%) diet was based on corn and soybean meal and formulated based on the digestible (d) Lys and dAAs (dMet, dThr, dTrp, dTSAA, dIle, and dVal) to meet 100% of the current management guide recommendation. Variations in dAA/CP (95, 90, and 85% diets) were accomplished by reducing the 100% dAA by 5, 10, and 15%, respectively. All diets were supplemented with phytase at 500 phytase units (FTU)/kg. Data were analyzed using PROC GLM of SAS 9.4. There was a main effect of dAA/CP level on 85% diet where it had a lower mean hen-day egg production (HDEP, P < 0.01), egg mass (EM, P < 0.01), and higher feed conversion ratio (FCR, P < 0.001). Higher egg weight (P < 0.01) was observed in 95 and 100% dAA/CP level diets. However, Haugh unit (P < 0.01) and albumen height (P < 0.01) were higher in 85 and 90% diets. The inclusion of protease reduced the feed consumption (P = 0.0247), FCR for dozens of eggs (P = 0.0049) from 30 to 49 wk of age without affecting the HDEP or EM. Protease supplementation and dAA/CP level had an effect on the apparent ileal digestibility (AID) of CP (P = 0.019), Lys (P < 0.01), Thr (P < 0.01), Trp (P = 0.017), and Val (P < 0.01). Addition of protease significantly increased egg income (P = 0.033) and return on investment (P = 0.00223) from 30 to 37 wk of age. At 38 to 50 wk of age, dAA/CP level had a significant effect on egg income (P < 0.001), feed cost (P < 0.001), and return on investment (P < 0.001). This experiment indicates that the inclusion of protease in 90 and 95% lower dAA/CP diets could help improve the digestibility of CP, and key amino acids and maintain productive performance of corn and soybean meal-based diets in Hy-Line W-36 laying hen from 30 to 50 wk of age.

The role of hen body weight and diet nutrient density in an extended laying cycle

The egg production (EP), egg quality and health of heavier or lighter hens fed a diet of either higher nutrient density (HND) or lower nutrient density (LND) during early lay, was assessed at very late lay. Based on their body weight (BW) at 18 wk of age (WOA) ISA Brown pullets were allocated as either heavier weight (HW; average 1.65 kg) or lighter weight (LW: average 1.49 kg). Half of each BW group received the HND (2,901 kcal/kg; 17.6% crude protein (CP) or LND (2726 kcal/kg, 16.4% CP) diet from 18 to 24 WOA. From 25 to 90 WOA all birds received identical early, then mid and late-lay diets. Hen BW was measured after peak-lay (36 WOA) and at 90 WOA. At 89 WOA and across 18 to 36 and 18 to 89 WOA feed intake (FI), EP, egg mass (EM), and feed conversion ratio (FCR) were calculated. Eggshell quality, breast score, relative ovary weight and liver and bone health were evaluated in very late lay. Differences in BW continued to 90 WOA. At 36 WOA HW hens produced heavier eggs, and had higher 18 to 36 WOA cumulative FI, EM (P < 0.001) and FCR (P < 0.05). When 89 WOA HW birds consumed more feed (P < 0.001) but EP, EM and FCR did not differ from LW hens. Cumulatively, 18 to 89 WOA FI and EM were higher for HW hens (P < 0.05), but cumulative EP and FCR was not different. The early-lay HND diet improved very late lay eggshell thickness (P < 0.05) and shell breaking strength (P = 0.05). Lighter hens fed HND and HW hens fed LND diet produced heavier eggs, higher relative oviduct weight and lower liver lipid peroxidase in very late lay (P < 0.05). Bone strength did not differ, but LW hens had higher femoral manganese and zinc (P < 0.05), lowering their likelihood of osteoporosis. Overall LW hens sustained EP throughout a longer laying cycle with beneficial bone characteristics. The HND diet improved eggshell strength and, in LW hens reduced hepatic oxidation.

Influence of the energy concentration and the standardized ileal digestible lysine content of the diet on performance and egg quality of brown-egg laying hens from 18 to 41 weeks of age

The influence of the energy and the standardized ileal digestible lysine (DLys) content of the diet on egg production and egg quality, was studied in brown-egg laying hens from 18 to 41 wk of age. The experimental design was completely randomized with 10 treatments organized as a 2 × 5 factorial with 2 energy concentrations (2,750 and 2,800 kcal AMEn/kg) and 5 levels of DLys (values varied from 0.66 to 0.78% and 0.67 to 0.79%, for the low and high energy diets, respectively). Each treatment was replicated 10 times (10 hens per replicate). The data were analyzed using the MIXED procedure of SAS with energy concentration and DLys content of the diets as main effects. In addition, the effects of the DLys on the variables studied were partitioned into its lineal and quadratic components. From 18 to 21 wk of age (pre-peak phase), diet composition had limited effects on egg production. From 22 to 41 wk of age (peak phase), however, an increase of 50 kcal AMEn/kg diet increased egg weight (P < 0.05) and tended to improve energy intake (P = 0.083) and feed conversion ratio (P = 0.074). An increase in DLys improved linearly (P < 0.001) egg production, egg weight, egg mass, feed conversion, and energy conversion ratio, and tended to increase BW gain (P = 0.074). Diet composition did not any affect egg quality trait except shell strength that increased linearly (P < 0.05) with increases in the DLys. Cumulatively (18–41 wk of age), egg weight increased (P < 0.05) as the energy and the DLys content of the diet increased. In summary, an increase in energy and DLys content of the diet had limited effects on egg production during the prepeak phase but improved egg production, feed conversion ratio, and BW gain during the peak phase. The data indicate that hens require at least 839 mg DLys/d to maximize egg production in the peak production phase.

The influence of hen size and diet nutrient density in early lay on hen performance, egg quality and hen health in late lay

The effect of hen size and diet nutrient density during early lay on egg production (EP) at 24 and 69 wk of age (WOA) and late lay egg quality and hen health was evaluated. Based on bodyweight (BW) at 18 WOA ISA Brown hens were assigned as heavier (HW; n = 120) or lighter weight (LW; n =120). Sixty birds from each BW group were fed an early-lay diet of higher nutrient density (HND), or lower nutrient density (LND) between 18 and 24 WOA. From 25 WOA all hens received the same early-lay diet and then from 40 WOA the mid-lay diet. Hen average daily feed intake (ADFI), hen-day EP, egg weight (EW), egg mass (EM), and feed conversion ratio (FCR) were assessed at 24 and 69 WOA. Between 66 and 70 WOA eggshell and internal egg quality was evaluated and at 70 WOA BW, liver and bone health were assessed. At 24 WOA BW was highest in HW birds and birds receiving the HND diet (P < 0.01). Concurrently ADFI, and FCR were higher and hen-day EP was lower in HW compared to LW birds (P < 0.05). The HND diet resulted in lower ADFI and FCR at 24 WOA, but higher EW and EM compared to the LND diet (P < 0.01). At 69 WOA HW birds had higher ADFI, EW (P < 0.02) and heavier 70 WOA BW compared to LW hens. The lower FCR of the LW birds at 69 WOA was approaching significance (P = 0.054). Hen weight and diet density did not affect 69 WOA egg production. Between 18 and 69 WOA cumulative FI and EM were higher in HW hens (P < 0.01) than LW hens, as was cumulative FCR (P = 0.053). Hen weight and diet density did not alter 66–70 WOA internal egg quality, but the HND diet generated thicker eggshells and higher eggshell breaking strength (P < 0.05). Seventy WOA liver health, keel curvature and femur breaking strength did not differ. Overall LW hens had lower FCR than HW hens and the early-lay HND diet facilitated improved eggshell integrity during late lay compared to the LND diet.

An evaluation of bird weight and diet nutrient density during early lay on ISA brown performance, egg quality, bone characteristics and liver health

This study compared the impact of a higher nutrient density (HND) or lower nutrient density (LND) diet fed during early lay to either heavier weight (HW) or lighter weight (LW) ISA Brown hens. At 18 wk of age (WOA) pullets (n = 240) were evenly assigned to either HW (n = 120) or LW (n = 120). Sixty birds from each weight group were then randomized to either the HND or LND diet treatments which were fed from 18 to 24 WOA inclusive. At 25 WOA the LND diet replaced the HND diet. All hens remained on LND diet to 50 WOA. Hen performance was measured from 18 to 50 WOA. Femur and liver health were evaluated at 50 WOA. Egg quality was assessed from 46 to 50 WOA. The 18 WOA HW hens had higher BW, cumulative egg production, cumulative feed intake (CFI), and cumulative egg mass (CEM) to both 24 and 50 WOA (P < 0.01). At 24 WOA the HND diet also generated higher BW (P < 0.001), CEM (P < 0.001) and lower cumulative feed conversion ratio (CFCR) (P < 0.01), the latter being sustained to 50 WOA (P < 0.01). At 50 WOA CFCR of LW birds was lower than HW birds (P < 0.01). Egg weight (EW), yolk diameter, and percent yolk weight were higher (P < 0.05) in the HW birds with the highest albumen to yolk ratio in LW birds (P < 0.05). Egg shape index was higher in LND diet fed birds (P < 0.01) while LW hens had higher shell phosphorus (P < 0.05). Body weight and diet nutrient density interacted on femoral diameter and cortical thickness being higher (P < 0.01) in LW birds fed HND than LW birds fed LND diets. Fatty liver hemorrhagic scores (P < 0.05) and liver lipid peroxidase (P < 0.001) at 50 WOA were higher in HW and LND diet treatments. Concurrently HW birds had the highest CFI and EW while CFCR and liver health were superior in LW and the HND diet treatment.

Influence of the energy and digestible lysine contents of the diet on performance and egg quality traits of brown-egg laying hens from 19 to 59 weeks of age

The influence of nutrient density and standardized ileal digestible lys (DLys) content of the diet on egg production and egg quality traits, was studied in brown-egg laying hens from 19 to 59 wk of age. The experimental design was completely randomized with eight treatments arranged as a 2×4 factorial with two AMEn concentrations (2,680 and 2,780 kcal/kg) and four levels of DLys (0.68, 0.72, 0.76, and 0.80%). Each treatment was replicated nine times and the experimental unit was a cage with nine hens. Hen production, egg components (proportion of albumen, yolk, and shell), egg quality traits (Haugh units, egg shell strength, and incidence of broken, dirty, and shell-less eggs) were measured by period (28 d) and cumulatively. Data were analyzed as a completely randomized design with energy concentration, level of DLys, and their interactions as main effects. In addition, the effects of the level of DLys on the variables studied, were partitioned into its linear and quadratic components. No interactions between AMEn and DLys content of the diet were detected for any of the traits studied and therefore, only main effects are presented. An increase in the AMEn concentration of the diet from 2,680 to 2,780 kcal/kg increased energy intake (P < 0.05) and egg weight (P < 0.001) and improved feed conversion ratio (P < 0.05). An Increase in DLys from 0.68 to 0.80% did not affect the number of eggs produced but increased linearly egg weight (P < 0.01) and egg mass production (P < 0.05). Diet did not affect egg quality. In conclusion, an increase in the AMEn content of the diet from 2,680 to 2,780 kcal/kg increased egg weight and improved feed efficiency. Laying hens require no more than 744 mg DLys/d (corresponding to 0.68% DLys) to optimize egg production. However, when the objective is to maximize egg weight, hens should consume at least 843 mg DLys/d (corresponding to 0.76% D Lys).

Effects of dietary probiotic (Pediococcus acidilactici) supplementation on productive performance, egg quality, and body composition in laying hens fed diets varying in energy density

This study was conducted to determine the effect of probiotic Pediococcus acidilactici (PA) strain MA18/5M supplementation of diets with different dietary energy levels on productive performance, egg quality, and body composition in Hy-Line Brown hens during a 16-week period from 32 to 47 wk of age. The experimental treatments with a 2 × 2 factorial design received a 2 wheat–corn–soybean diet: a moderately low energy density diet with 2,650 kcal ME/kg (M-LED) and a low energy density diet based on the M-LED diet with 2,550 kcal ME/kg (LED), each diet without and with probiotic supplementation (M-LED, LED, M-LEDp, and LEDp, respectively). Reduced dietary energy levels had a particularly negative effect on egg weight (61.7 vs. 63.3 g; −2.6%, P < 0.001), egg mass output (1.67 vs. 1.71 kg; −2.4%, P = 0.015), and FCR (2.01 vs. 1.97 kg feed/kg egg; +2%, P = 0.028). In hens administered the LED diet, deteriorated productive performance was accompanied by greater body weight loss (P < 0.001) and reduced abdominal fat content (P < 0.033) as compared with the M-LED group. Dietary probiotic inclusion increased egg weight (P = 0.015), including relative eggshell weight (P = 0.008) and eggshell thickness (P = 0.002) and significantly improved FCR (P = 0.010). No interactions between the PA-based probiotic and dietary energy levels were found in any of the tested parameters. Adding the probiotic on top of the M-LED diet improved layers performance but resulted in nonbioequivalence for the egg weight, egg mass output, and FCR compared with this group without probiotic. Probiotic supplementation of the LEDp diet improved all performance parameters except for egg weight. As a result, the laying rate, egg mass output, daily feed intake, and FCR in the LEDp treatment were bioequivalent to those noted in the M-LED group without the probiotic. The results of a bioequivalence test suggest that a low energy diet fed to laying hens promoted a probiotic response to improve energy utilization by birds.

Equations of prediction for abdominal fat in brown egg-laying hens fed different diets

The objective was to use noninvasive measurements to formulate equations for predicting the abdominal fat weight of laying hens in a noninvasive manner. Hens were fed with different diets; the external body measurements of birds were used as regressors. We used 288 Hy-Line Brown laying hens, distributed in a completely randomized design in a factorial arrangement, submitted for 16 wk to 2 metabolizable energy levels (2,550 and 2,800 kcal/kg) and 3 levels of crude protein in the diet (150, 160, and 170 g/kg), totaling 6 treatments, with 48 hens each. Sixteen hens per treatment of 92 wk age were utilized to evaluate body weight, bird length, tarsus and sternum, greater and lesser diameter of the tarsus, and abdominal fat weight, after slaughter. The equations were obtained by using measures evaluated with regressors through simple and multiple linear regression with the stepwise method of indirect elimination (backward), with P < 0.10 for all variables remaining in the model. The weight of abdominal fat as predicted by the equations and observed values for each bird were subjected to Pearson's correlation analysis. The equations generated by energy levels showed coefficients of determination of 0.50 and 0.74 for 2,800 and 2,550 kcal/kg of metabolizable energy, respectively, with correlation coefficients of 0.71 and 0.84, with a highly significant correlation between the calculated and observed values of abdominal fat. For protein levels of 150, 160, and 170 g/kg in the diet, it was possible to obtain coefficients of determination of 0.75, 0.57, and 0.61, with correlation coefficients of 0.86, 0.75, and 0.78, respectively. Regarding the general equation for predicting abdominal fat weight, the coefficient of determination was 0.62; the correlation coefficient was 0.79. The equations for predicting abdominal fat weight in laying hens, based on external measurements of the birds, showed positive coefficients of determination and correlation coefficients, thus allowing researchers to determine abdominal fat weight in vivo.