Research Note: Nitrogen-corrected apparent metabolizable energy and standardized ileal amino acid digestibility determination of high-protein dried distiller's grains and corn bran with solubles for broilers

Abstract

Metabolism and digestibility trials were performed on broiler chickens to determine 1) nitrogen-corrected apparent metabolizable energy (AMEn) using total excreta collection and 2) standardized ileal amino acid digestibility (SIAAD) using the ileal digesta collection from high-protein dried distillers’ grains (HP-DDG) and corn bran with solubles (CBS). The results of the metabolism trial indicated that AMEn values for HP-DDG and CBS were 3,334 kcal/kg and 2,083 kcal/kg on dry matter (DM) basis, respectively. Concerning the HP-DDG, the digestibility trial resulted in the following SIAAD values and digestible concentrations, respectively: 80.33% and 1.09 for Lys, 85.95% and 1.44 for Met + Cys, 75.58% and 1.24 for Thr, 89.58% and 1.66 for Arg, 84.91% and 1.08 for His, 86.37% and 1.35 for Ile, 90.64% and 4.56 for Leu, 85.76% and 1.80 for Val, and 88.67% and 1.90 for Phe. Concerning the CBS, the following SIAAD values and digestible concentrations were measured, respectively: 79.29% and 0.44 for Lys, 89.57% and 0.31 for Met + Cys, 78.89% and 0.40 for Thr, 92.28% and 0.66 for Arg, 87.48% and 0.36 for His, 93.40% and 0.35 for Ile, 92.27% and 1.01 for Leu, 90.97% and 0.51 for Val, and 88.81% and 0.45 for Phe. The digestibility average of CBS is 88.45% for essential amino acids and 85.21% for nonessential amino acids, whereas the digestibility average of HP-DDG is 85.83% for essential amino acids and 83.83% for nonessential amino acids.

INTRODUCTION

Protein and energy represent a major proportion in poultry diets, so their prices directly influence the cost of poultry production. Therefore, continuous efforts are made to find ingredients that meet broilers’ nutritional requirements and reduce feed costs.

Dried distiller's grains (DDG) are a coproduct from the ethanol industry. They have been included in poultry diets due to their potential to partially replace high-protein ingredients, such as soybean meal, while reducing the need for supplemental amino acids (AA) (Fries-Craft and Bobeck, 2019). The ethanol industry is characterized by its continuous innovation of processing techniques to enhance ethanol yield, which consequently alters the chemical composition of corn coproducts (Rho et al., 2017).

Fries-Craft and Bobeck (2019) state that intentionally changing the process method can increase the nutritional profile of coproducts, such as increasing crude protein (CP) levels and metabolizable energy (ME), thus increasing their value for nonruminant animals. Moreover, there is a great interest in producing ethanol coproducts with higher levels of CP content and digestible amino acids for poultry (Corray et al., 2019). Considering this, a recent technology (FST; ICM Inc., Colwich, KS) was developed that involves the removal of fibers before starch fermentation, which allows ethanol plants to produce more efficiently (Shurson, 2018). It also results in 2 coproducts: 1) high-protein DDG (HP-DDG), which contain ≥38% of CP and low fiber levels; and 2) corn bran with solubles (CBS), a high energy coproduct that may vary in CP content.

ME is the most common value to define the dietary energy available for poultry. The nitrogen correction for its retention in the body is usually applied to obtain a nitrogen-corrected ME (MEn) (NRC, 1994). At the same time, the standardized ileal amino acid digestibility (SIAAD) concentration of ingredients is essential when formulating poultry diets (Sheikhhasan et al., 2020).

HP-DDG and CBS are limited for broilers’ diets due to limited information on their nutritional value. Therefore, the objective of the present study was to determine the nitrogen-corrected apparent metabolizable energy (AMEn) and SIAAD concentration of these 2 coproducts.

MATERIALS AND METHODS

Ethics Committee

All procedures adopted in this research were previously approved by the Ethics Committee in the Use of Farming Animals at the Federal University of Viçosa under protocol number 034/2021, following the norms of the National Council for Experimentation Animal Control.

Birds Husbandry

The experiment was carried out at the Research & Extension Sector for Poultry Production and Nutrition of the Animal Science Department, Federal University of Viçosa, Viçosa, Minas Gerais, Brazil.

Cobb500 male broiler chicks were obtained from a commercial hatchery (Rivelli Alimentos SA, Matheus Leme, MG, Brazil), where all chicks received vaccinations for Marek and Newcastle diseases and infectious bronchitis. Before reaching 16 d, broiler chicks were reared under conditions established by the Cobb500 guideline recommendations. They had free access to water and feed, which was based on corn and soybean meal formulated according to Rostagno et al. (2017).

A total of 180 Cobb500 male chicks (583 g ± 27.8 g) were housed in metabolic cages (600 cm²/bird) and randomly distributed into 3 treatments, including 10 replicates with six 16 to 32-day-old birds each. Each experimental unit was equipped with a nipple drinker and a trough feeder to guarantee free access to water and feed during the experimental period. Temperature and light programs were set according to genetic guidelines.

HP-DDG and CBS

The same batches of HP-DDG and CBS were used in the following experiment and were analyzed for their nutrient profile (Table 1). Both coproducts were sourced from a Brazilian company (F.S. Bioenergia Inc., Lucas do Rio Verde, Mato Grosso, Brazil) and produced through FST technology (ICM Inc., Colwich, KS).

Table 1.

Composition of the experimental diets used in the metabolism and digestibility trials.

Ingredients, %
Metabolizable energy trial
	Basal diet	30% HP-DDG4	30% CBS5
Corn	60.15	42.11	42.11
Soybean meal	35.00	24.50	24.50
Soybean oil	2.10	1.47	1.47
Dicalcium phosphate	0.95	0.67	0.67
Limestone	0.98	0.69	0.69
Salt	0.48	0.34	0.34
Mineral premix1	0.05	0.04	0.04
Vitaminic premix2	0.13	0.09	0.09
Choline chloride, 60%	0.10	0.07	0.07
Salinomycin, 12%	0.05	0.04	0.04
BHT3	0.01	0.01	0.01
High-protein DDG	-	30.00	-
Corn bran with solubles	-	-	30.00
Total	100.00	100.00	100.00
Amino acid digestibility trial
	NFD	30% HP-DDG4	30% CBS5
Starch	82.75	52.75	52.75
Sugar	5.00	5.00	5.00
Soybean oil	5.00	5.00	5.00
Dicalcium phosphate	1.62	1.62	1.62
Limestone	0.80	0.80	0.80
Salt	0.45	0.45	0.45
Corncob	3.00	3.00	3.00
Mineral premix1	0.05	0.05	0.05
Vitaminic premix2	0.13	0.13	0.13
Choline chloride, 60%	0.20	0.20	0.20
Indigestible marker Celite	1,00	1,00	1,00
High-protein DDG	-	30.00	-
Corn bran with solubles	-	-	30.00
Total	100.00	100.00	100.00

¹Trace mineral premix provided per kg of diet: Mn, 58.36 g; Fe, 41.68 g; Zn, 54.21 g; Cu, 8.31 g; I, 0.84 g; Se, 0.25 g.

²Vitamin premix provided per kg of diet: vitamin A, 9,638,000 IU; vitamin D3, 2,410,000 IU; vitamin E, 36,100 IU; vitamin B1, 2.60 g; vitamin B2, 6.45 g; vitamin B6, 3.61 g; vitamin B12, 15.9 mg; vitamin K3, 1.94 g; pantothenic acid, 12.95 g; nicotinic acid, 39.20 g; folic acid, 0.90 g; biotin, 89.80 mg.

³Antioxidant butylhydroxytoluene.

⁴HP-DDG analyzed composition (as-fed basis): 91.74% dry matter, 42.60% crude protein, 5,358 kcal/kg gross energy, 13.03% ether extract, 5.48% starch, 6.06% crude fiber, 24.14% neutral detergent fiber, 16.88% acid detergent fiber, 2.21% ash, 0.005% calcium, 0.49% total phosphorus, 0.07% sodium, 0.10% magnesium, 0.56% potassium 10.42 mg/kg copper, 157.57 mg/kg iron, 6.23 mg/kg manganese, and 49.76 mg/kg zinc.

⁵CBS analyzed composition (as-fed basis): 88.76% dry matter, 15.64% crude protein, 4,293 kcal/kg gross energy, 6.15% ether extract, 3.45% starch, 10.78% crude fiber, 49.86% neutral detergent fiber, 12.74% acid detergent fiber, 5.44% ash, 0% calcium, 0.70% phosphorus, 0.18% sodium, 0.30% magnesium, 1.48% potassium, 6.26 mg/kg copper, 52.13 mg/kg iron, 17.81 mg/kg manganese, and 67.24 mg/kg zinc.

Metabolism Trial—AMEn

The trial was performed from 16 to 26-days old to determine the AMEn. The treatments comprised a basal diet (BD) meeting the nutritional requirements of the birds, according to Rostagno et al. (2017), and 2 diets composed of 70% of BD and 30% of HP-DDG or CBS (Table 1).

The trial period lasted 10 d; the first 5 d were destined for adapting the birds to the experimental diets, and the last 5 d were intended for total excreta collection and measure of feed intake. A metal tray coated with plastic canvas, which allowed the individual excreta collection for each experimental unit, was placed under the metabolic cages. Excreta were collected twice daily, at 8 am and 4 pm, to avoid fermentation and nutrient losses. After each collection period, excreta were packed in plastic bags identified according to their respective experimental unit and stored at −20°C. At the end of the last collection day, excreta were defrosted and individually weighed to measure the total amount produced. Feed intake was measured through the difference between the feed given to the birds at the beginning and end of the same 5 collection days.

Homogenous and representative samples of excreta, experimental diets, HP-DDG, and CBS were analyzed according to the Association of Official Analytical Chemists (AOAC): dry matter (DM; AOAC, 934.01, 2006) and nitrogen (N; AOAC, 990.03, 2006). Gross energy (GE) was measured by a C500 adiabatic bomb calorimeter (IKA-Werke GmbH & Co. KG, Staufen, Germany). Nitrogen balance (NB) was calculated by the difference between N intake and N excreted. The total AMEn intake of each experimental diet was calculated using the following equation:

$$\text{AMEn}=\left[\right(\text{GE intake}-\text{GE excretion})-8.22\times \text{NB})]/\text{DM intake}$$

The equation below was used to calculate the AMEn of HP-DDG and CBS:

$$\text{AMEn}=\text{BD}-\left[\right(\text{BD}-\text{TD})/\text{g}/\text{g of}\text{substitution}]$$

where BD is the nitrogen-corrected metabolizable energy of the basal diet and TD is nitrogen-corrected metabolizable energy of each of the experimental diets with HP-DDG and CBS.

Digestibility Trial—SIAAD

The trial was performed from 27 to 32-days old to determine the SIAAD concentration. The treatments comprised a nitrogen-free diet (NFD) used to measure basal ileal endogenous amino acids losses (IEAA), and 2 diets with 30% of either HP-DDG or CBS replacing starch in the NFD. All diets included 1% of acid insoluble ash (AIA; Celite) as an indigestible marker (Table 1).

Birds were fed with the experimental diets for 5 d, at the end of which they were slaughtered by cervical dislocation for ileal digesta collection. Ileum was identified as the section of the intestine between Meckel's diverticulum and the ileocecal junction. Digesta were entirely removed by flushing with distilled water. They were placed in plastic pots identified according to their respective experimental unit and stored at −20°C. For the analyses, digesta were lyophilized and grounded. Samples of digesta and diets were analyzed for DM (AOAC, 934.01, 2006) and ash (AOAC, 942.05, 2006), and AIA content was analyzed through the adapted methodology described by Van Keulen and Young (1977). Moreover, HP-DDG, CBS, diets, and digesta were analyzed for AA and CP content by CBO Análises Laboratoriais (Valinhos, São Paulo, Brazil).

Apparent and standardized digestibility values and endogenous ileal losses were calculated using the following equations:

$$\text{AIAAD}\text{value}(\%)=\left[\left(\text{AA}\text{diet}\left(\text{DM},\%\right)/\text{AIA}\text{diet}(\%)\right)-\left(\text{AA digesta}(\%)-\text{AIA digesta}(\%)\right)\mathrm{\times }100\right]/\left(\text{AA diet}\left(\text{DM},\%\right)/\text{AIA diet}(\%)\right)$$

$$\text{IEAA}\left(\mathrm{g}/\text{kg}\text{DM}\right)=\left(\text{AA}\text{digesta}\left(\mathrm{g}/\text{kg}\text{DM}\right)\right)\mathrm{\times }\left(\text{AIA}\text{diet}\left(\mathrm{g}/\text{kg}\text{DM}\right)\right)/\left(\text{AIA}\text{digesta}\left(\mathrm{g}/\text{kg}\text{DM}\right)\right)$$

$$\text{SIAAD}\text{value}\left(\mathrm{\%}\right)=\text{AIAAD value}\left(\mathrm{\%}\right)+\left(\text{IEAA}\left(\mathrm{g}/\text{kg}\text{DM}\right)\right)/(\text{AA}\text{diet}\left(\mathrm{g}/\text{kg}\text{DM}\right)\mathrm{\times }\mathrm{100}$$

where AIAAD value is the apparent ileal amino acid digestibility value, IEAA is the ileal endogenous amino acid losses, and SIAAD value is the standardized ileal amino acid digestibility value.

The SIAAD concentration was calculated by multiplying each SIAAD value by the respective AA content in each ingredient.

RESULTS AND DISCUSSION

The analyzed composition of CBS is shown in Table 1. The AMEn of CBS was 2,083 kcal/kg on a DM basis (Table 2). This value is lower than the ones observed by Rochell et al. (2011) and Oliveira (2019), who found an AMEn of 3,030 kcal/kg and 2,590 kcal/kg on a DM basis for corn bran and CBS, respectively. Moreover, it is lower than the value of 2,666 kcal/kg on DM basis for conventional DDGS according to the NRC (1994). This lower AMEn value could be explained by the lower fat content and higher NDF levels than those mentioned before (NRC, 1994; Rochell et al., 2011; Oliveira, 2019). The CP of CBS was 17.62% on a DM basis, which is similar to the report from Oliveira (2019), who found a value of 17.44% on a DM basis. However, it is higher than the value of 15.17% found by Rochell et al. (2011) and lower than the conventional DDGS of 29.5% reported by the NRC (1994). In addition, the total Lys concentration in CBS was lower than reported by Oliveira (2019) and conventional DDGS reported by the NRC (1994) (0.55 vs. 0.80% and 0.81% on a DM basis, respectively). Although SIAAD values for CBS displayed a higher value for all essential amino acids than the one reported by Oliveira (2019) and the NRC (1994) for conventional DDGS, the total amino acid concentration was lower. However, the SIAAD concentration of all essential amino acids was similar to the CBS reported by Oliveira (2019) and lower than conventional DDGS reported by the NRC (1994). In summary, the results obtained for CBS in the present study suggest that its energy is lower than previously reported for CBS, corn bran, and conventional DDGS. However, its protein and digestible amino acids are similar to previously reported data on CBS and lower than those on corn bran and conventional DDGS.

Table 2.

Apparent metabolizable energy (AME), nitrogen-corrected apparent metabolizable energy (AMEn), standardized ileal amino acid digestibility value (SIAAD value), total amino acids content (AA) and standardized ileal digestibility (SID) on as-fed basis, and ileal endogenous amino acids losses (IEAA) of HP-DDG and CBS used in the metabolism and digestibility trials.

Item	HP-DDG			CBS
	AME, kcal/kg	AMEn, kcal/kg		AME, kcal/kg	AMEn, kcal/kg
Dry matter	3,535 ± 410.3	3,334 ± 399.1		2,215 ± 536.5	2,083 ± 478.6			IEAA, g/kg DM
As-fed basis	3,243 ± 376.4	3,058 ± 366.1		1,966 ± 448.9	1,849 ± 424.8
	SIAAD value (%)	AA, %	SID¹	SIAAD value (%)	AA, %	SID1
Essential amino acids
Lysine	80.3 ± 4.285	1.36	1.09	79.3 ± 7.815	0.55	0.44		0.408 ± 0.1924
Methionine	90.5 ± 3.380	0.91	0.82	91.5 ± 4.275	0.17	0.16		0.106 ± 0.0433
Methionine + cystine	85.9 ± 3.845	1.68	1.44	89.6 ± 3.775	0.35	0.31		0.167 ± 0.0642
Threonine	75.6 ± 5.869	1.64	1.24	78.9 ± 11.219	0.51	0.40		0.611 ± 0.1894
Arginine	89.6 ± 3.640	1.85	1.66	92.3 ± 3.755	0.72	0.66		0.379 ± 0.1585
Histidine	84.9 ± 3.550	1.27	1.08	87.5 ± 3.926	0.41	0.36		0.190 ± 0.0832
Isoleucine	86.4 ± 4.870	1.56	1.35	93.4 ± 5.373	0.38	0.35		0.379 ± 0.1276
Leucine	90.6 ± 3.484	5.03	4.56	92.3 ± 3.747	1.09	1.01		0.631 ± 0.2420
Valine	85.8 ± 4.587	2.10	1.80	90.9 ± 4.338	0.56	0.51		0.478 ± 0.1839
Phenylalanine	88.7 ± 3.926	2.14	1.90	88.8 ± 6.369	0.51	0.45		0.338 ± 0.1242
Nonessential amino acids
Alanine	88.0 ± 3.907	3.27	2.88	87.9 ± 4.193	0.92	0.81		0.420 ± 0.1613
Aspartic acid	77.7 ± 5.289	2.78	2.16	85.4 ± 6.186	0.87	0.74		0.301 ± 0.1189
Cystine	79.3 ± 4.634	0.77	0.61	86.7 ± 4.543	0.18	0.16		0.061 ± 0.0213
Glutamic acid	88.9 ± 2.228	7.51	6.67	91.1 ± 3.977	1.96	1.79		0.653 ± 0.2878
Glycine	75.4 ± 4.691	1.66	1.25	78.4 ± 6.808	0.66	0.52		0.464 ± 0.1492
Serine	80.5 ± 4.451	2.12	1.71	74.9 ± 10.049	0.60	0.45		0.539 ± 0.1681
Glycine + serine	78.2 ± 4.527	3.78	2.96	76.9 ± 8.029	1.26	0.97		1.003 ± 0.3168
Tyrosine	88.6 ± 3.892	1.71	1.51	88.5 ± 5.288	0.40	0.35		0.299 ± 0.1075
Phenylalanine + tyrosine	94.7 ± 2.009	3.85	3.65	95.2 ± 2.177	0.91	0.87		0.325 ± 0.1084
Proline	87.0 ± 2.175	3.89	3.39	87.3 ± 3.555	1.10	0.96		0.497 ± 0.1476

AME, AMEn, SIAAD, and IEAA presented as average of 10 replicates cages ± standard deviation.

¹SID = (total amino acids concentration × standardized digestibility coefficient)/100.

The other final ethanol coproduct evaluated was HP-DDG and its analyzed composition is shown in Table 1. The AMEn of HP-DDG was 3,334 kcal/kg on a DM basis (Table 2), which is similar to the value of 3,276 kcal/kg reported by Fries-Craft and Bobeck (2019), and higher than value of 2,546 kcal/kg reported by Oliveira (2019). Due to the high CP content (46.44% on a DM basis), HP-DDG was expected to contain higher levels of all amino acids than conventional DDGS. For example, the total Lys content in HP-DDG was 1.36%, whereas conventional DDGS contains 0.81% (NRC, 1994). The most limiting AA in broiler nutrition is Lys, Met, and Thr; therefore, a high digestibility of these AA in HP-DDG would be of great interest. The total AA content was higher or similar to the ones reported by Jung and Batal (2009) and Fries-Craft and Bobeck (2019), but lower than the content in Lys and Thr, reported by Oliveira (2019). The SIAAD values showed a similar pattern to those reported by Jung and Batal (2009) and Fries-Craft and Bobeck (2019), which were higher than those reported by Oliveira (2019). In general, the results found for SIAAD concentration are in agreement with the previous reports in the literature for the essential amino acids assessed (Jung and Batal, 2009; Fries-Craft and Bobeck, 2019; Oliveira, 2019). In addition, the SIAAD concentration of Met + Cys and Thr in HP-DDG were similar, but they were lower in Lys compared to soybean meal with 44% of CP (Rostagno et al., 2017). On the other hand, the SIAAD concentration of Lys and Thr was lower in HP-DDG, but the one of Met was higher compared to soybean meal with 47.5% of CP, as reported in the NRC (1994). The results obtained for Lys were expected since the HP-DDG is a coproduct from corn, which has a lower Lys concentration compared to soybean meal. Overall, the nutritional value of HP-DDG used in this study is consistent with previous research regarding AMEn and SIAAD concentration.

In conclusion, the AMEn of CBS and HP-DDG is 2,083 kcal/kg and 3,334 kcal/kg on a DM basis, respectively. The digestibility average of CBS is 88.45% for essential amino acids and 85.21% for nonessential amino acids, whereas the digestibility average of HP-DDG is 85.83% for essential amino acids and 83.83% for nonessential amino acids.