Nutritional and feeding value of crude glycerin for poultry. 1. Nutritional value of crude glycerin

©2011 Poultry Science Association, Inc.

Nutritional and feeding value of crude glycerin for poultry. 1. Nutritional value of crude glycerin B. Jung and A. B. Batal1 Department of Poultry Science The University of Georgia, Athens 30602-2772 Primary Audience: Nutritionists, Researchers, Quality Control Personnel SUMMARY

Key words: glycerin, poultry, nitrogen-corrected true metabolizable energy, methanol 2011 J. Appl. Poult. Res. 20:162–167 doi:10.3382/japr.2010-00235

DESCRIPTION OF PROBLEM Biodiesel is produced from vegetable oil or animal fat during a transesterification process, which is a chemical reaction that breaks lipids, mainly triglycerides, into a mixture of mono-alkyl esters, such as methyl esters and crude glycerin, by the addition of an alcohol (usually methanol) in the presence of a base catalyst, such as sodium hydroxide or potassium hydroxide. The 1

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esters are used as a biodiesel fuel, whereas the crude glycerin is the by-product of biodiesel production [1]. Every gallon of biodiesel production generates approximately 0.3 kg (0.66 lb) of crude glycerin [2]. The increased pressure by the US government to expand production of biofuels is expected to further increase the production of biodiesel. Thus, this would result in an increased supply of the by-product, glycerin. There have been reports that crude glycerin can

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Glycerin is the main by-product of biodiesel production and it has been speculated that it may be a good energy source in poultry diets. However, knowledge is limited on the nutritional value of crude glycerin. Thus, the objective of this study was to determine the nutritional and chemical characteristics of various glycerin samples from diverse production facilities. Seven samples of crude glycerin from an array of biodiesel producers were analyzed for gross energy and TMEn. Ten crude glycerin samples were analyzed for glycerol, methanol, nutritional, and mineral composition. Considerable variation was found in the composition of the crude glycerin samples. The gross energy ranged from 3,337 to 6,742 kcal/kg, with a mean of 4,648 kcal/kg, and TMEn ranged from 2,950 to 6,711 kcal/kg, with a mean of 4,206 kcal/kg. Mean concentration values for glycerol, methanol, moisture, fat, salt, and ash were 63.7, 1.33, 18.2, 8.1, 2.19, and 4.35%, respectively. Phosphorus was the highest mineral component, with an average of 0.1% in the crude glycerin samples, and the average calcium, potassium, copper, zinc, iron, magnesium, and manganese levels were 328, 2,090, 3.20, 5.21, 18.6, 43.6, and 1.26 ppm, respectively. The range in glycerol, methanol, moisture, fat, salt, and potassium levels were from 34.2 to 86.1%, from 0.01 to 3.10%, from 7.85 to 34.9%, from 0.01 to 30.0%, from 0.01 to 4.21%, and from 120 to 11,200 ppm, respectively. Based on the variation observed among samples, we suggest that confirmatory analyses be conducted before using any crude glycerin product in poultry diets.

Jung and Batal: COMPOSITION OF GLYCERIN

MATERIALS AND METHODS All experimental protocols using animals were reviewed and approved by the Animal Care and Use Committee at the University of Georgia. Ten commercially produced crude glycerin samples from plants using soybean oil

as the main feedstock were obtained from 7 different plants in the United States between 2007 and 2009. Each sample was analyzed for proximate composition, glycerol, methanol, and mineral concentration [13, 14]. The sample numbers were held constant throughout the studies. Thus, sample 5 in Table 1 is the same sample as sample 5 in Table 2. Seven of the 10 samples were also evaluated for TMEn [15, 16]. Briefly, Single Comb White Leghorn roosters were fasted for 24 h and then crop intubated with 35 g of a corn-glycerin mix (85 and 15%, respectively) or 35 g of only corn. Excreta were collected for 48 h after the crop intubation, freeze-dried, and weighed. The data were analyzed using the GLM procedure of SAS [17] to determine the mean and SD of the samples.

RESULTS AND DISCUSSION The gross energy (GE) and the TMEn value of the 7 crude glycerin samples obtained from various production facilities are presented in Table 1. The average GE of the 7 glycerin samples was 4,648 kcal/kg, which was higher than the GE levels (4,100, 3,625, and 3,596 kcal/kg) reported by Brambila and Hill [4], Dozier et al. [3], and Cerrate et al. [5]. In addition, the GE values of some of the glycerin products in our current study were within the range of the values reported previously [3, 5]. The GE of the samples studied herein was generally lower than the reported GE value of pure glycerin (4,100, 4,305, and 4,310 kcal/kg [4, 6, 18]. However, 2 samples had extremely high GE values. The

Table 1. The gross energy (GE) and TMEn value of 7 glycerin products (as-fed basis) Sample 1 2 3 4 5 6 7 Mean2 Range3 1

GE, kcal/kg 3,902 3,842 6,742 6,734 3,680 3,337 4,298 4,648 ± 1,456 3,337 to 6,742

TMEN, kcal/kg (%) 3,252 (83)1 3,143 (82) 6,549 (97) 6,711 (99) 3,390 (92) 2,950 (88) 3,450 (80) 4,206 ± 1,664 (88.7 ± 7.5) 2,950 to 6,711 (80 to 99)

Values in parentheses represent the TMEn value expressed as a percentage of the GE value (TMEn/GE × 100). Mean ± SD of 7 glycerin samples. 3 Range of values observed for 7 glycerin samples. 2

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be used as an energy source in poultry diets [3–5], and glycerin is considered generally recognized as safe (GRAS) as a feed additive. However, the use of crude glycerin in poultry diets has been challenged because of its poor purity and high variation in nutritional and mineral composition between products [2, 6]. In addition, crude glycerin contains other drawbacks that may limit the inclusion level, such as methanol contamination [6]. Methanol can be found at very high concentrations because it is not entirely recovered in the current biodiesel processing, and even low levels of ingested methanol can result in formic acid accumulation, which causes metabolic acidosis in animals and poultry [7–9]. Clinical outcomes of methanol poisoning include depression of the central nervous system, vomiting, blindness, and Parkinsonian-like motor disease [9–12]. Therefore, before crude glycerin is used as an alternative fat source in poultry diets, it is necessary to characterize its chemical and nutritional qualities. To our knowledge, the TMEn of glycerin for chickens has not been reported. Thus, the objective of this research was to determine the nutritional and chemical characteristics of various glycerin products from different production facilities.

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85.7 86.1 57.4 44.6 84.1 66.6 58.3 73.9 46.5 34.2 63.7 ± 18.6 34.2 to 86.1

1 2 3 4 5 6 7 8 9 10 Mean4 Range5

<0.01 <0.01 1.79 1.51 <0.01 1.40 2.23 3.10 2.50 0.72 1.33 ± 1.1 0.01 to 3.10

Methanol 11.3 9.96 12.2 7.85 14.3 28.4 34.9 25.1 26.1 11.9 18.2 ± 9.5 34.9 to 7.85

Moisture 0.24 0.122 17.72 13.22 0.012 1.102 16.13 0.153 2.513 30.03 8.1 ± 10.5 0.01 to 30.7

2

Fat 0.90 4.40 0.30 0.30 0.80 — — — — — 1.34 ± 1.7 0.0 to 4.40

Free fatty acid 0.15 0.21 0.85 0.58 0.01 1.43 1.91 1.33 1.05 0.94 0.85 ± 0.6 0.01 to 1.91

CP

Crude fiber 0.06 0.33 0.72 0.91 0.01 0.03 0.17 0.07 0.31 0.88 0.35 ± 0.4 0.01 to 0.91

2

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The glycerin samples were sent to a commercial laboratory for composition analysis (Minnesota Valley Testing Laboratories, New Ulm, MN). Fat = crude fat [13] (method 920.39: Fat determination in feed/ingredient by Soxtec extraction). 3 Fat = petroleum ether [13] (method 945.16: Oil in cereal adjuncts). 4 Mean ± SD of 10 glycerin samples. 5 Range of values observed for 10 glycerin samples.

1

Glycerol

Sample

Table 2. Glycerol, methanol, and proximate composition (%) of 10 glycerin products (as-fed basis)1

4.14 4.11 0.01 0.01 3.08 3.02 2.57 4.21 0.72 0.01 2.19 ± 1.8 0.01 to 4.21

Salt

4.64 4.54 4.18 4.55 3.12 3.66 3.56 4.85 5.08 5.34 4.35 ± 0.7 3.12 to 5.34

Ash

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Jung and Batal: COMPOSITION OF GLYCERIN

the value (0.41%) reported by Dozier et al. [3]. However, the average sodium chloride content in the glycerin products was 2.19% (SD = 1.8), with a range of 0.01 to 4.21%, which was lower than the value (3.13%) reported by Dozier et al. [3]. The high salt concentration and variation between samples can be a serious problem in feed formulation and should to be taken into consideration. The mineral contents of the 10 glycerin samples are presented in Table 3. The phosphorus level ranged from 0.01 to 0.26% and averaged 0.10% (SD = 0.09), which was significantly higher than the values measured from crude glycerin samples made from soybean and canola oil (53.0 and 58.7 ppm, respectively) reported by Thompson and He [2]. The calcium content varied from 28 to 1,500 ppm, with an average of 328 ppm (SD = 460), which was also much higher than the values (11.0 ppm for crude glycerin from soybean oil, and 19.7 ppm for crude glycerin from canola oil) noted by Thompson and He [2]. In addition, the average levels of chloride (1.26%; data was not shown) and potassium (2,090 ppm) in crude glycerin products were relatively higher than the other elements. During the production of biodiesel, fat is mixed with methanol in the presence of a catalyst, such as sodium or potassium hydroxide, which may explain the variation in potassium and sodium levels between samples. In addition, the average copper, zinc, iron, magnesium, and manganese levels in 10 crude glycerin products were 3.20, 5.21, 18.6, 43.6, and 1.26 ppm, respectively. The range in the mineral contents of the 10 glycerin products in the current study varied widely, and the average levels were markedly dissimilar compared with the values reported by Thompson and He [2]. Large differences were observed between the average values obtained from these 10 glycerin samples and those reported by Dozier et al. [3] and Thompson and He [2]. These differences could be due to differences in the feedstock (different fats used) and production process (differences in the facilities). Therefore, it is important that confirmatory analysis be conducted on crude glycerin products before their use in poultry feed because the crude glycerin from different plants and suppliers may vary. Research

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TMEn ranged from 2,950 to 6,711 kcal/kg, with an average of 4,206 kcal/kg (SD = 1,664), which was also higher than the value reported by Dozier et al. [3] (3,621 kcal/kg AME). The high average GE and TMEn were likely due to the 2 samples (samples 3 and 4) that had extremely high GE and determined TMEn. The TMEn value as a percentage of GE (TMEn/GE × 100) ranged from 80 to 99%, with an average of 88.7% (SD = 7.5). However, other researchers have reported that the ME value as a percentage of GE is closer to 98 [18] or 90% [3]. The glycerol, methanol, and proximate composition of the 10 crude glycerin samples are presented in Table 2. Glycerol values ranged between 34.2 and 86.1% and averaged 63.7% (SD = 18.6), which was lower than the value (86.95%) reported by Dozier et al. [3]. Lammers et al. [6] reported that the AME value is a direct function of the glycerol content: as the glycerol content goes up, the ME value increases. In the studies reported herein, one cannot arrive at that conclusion because of samples 3 and 4, which had very high GE and TMEn values and a lower glycerol content. The methanol content ranged from 0.01 to 3.10%, with an average of 1.33% (SD = 1.1) for all 10 samples, which was much higher than the value (0.03%) reported by Dozier et al. [3]. In addition, the moisture and fat contents of the glycerin samples ranged from 7.85 to 34.9% and 0.01 to 30%, and averaged 18.2% and 8.1%, respectively, which again were higher than the levels (9.63 and 0.12%) reported by Dozier et al. [3]. The researchers were informed by the biodiesel plant personnel that water was added to sample number 7 because of the high methanol level. Therefore, we emphasize that significant variation exists between plants. There appeared to be an inverse relationship between the fat and glycerol content in our current samples: when the glycerol content was high, the fat content was low. There also appeared to be a relationship between glycerol and methanol concentration: samples with lower glycerol concentrations tended to have higher methanol levels. In addition, crude glycerin samples with higher GE and TMEn values tended to contained relatively higher fat levels. Crude protein ranged from 0.01 to 1.91% and averaged 0.85% (SD = 0.6), which was also higher than

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<0.01 <0.01 0.05 0.04 0.06 0.21 0.26 0.09 0.18 0.09 0.10 ± 0.09 0.01 to 0.26

1 2 3 4 5 6 7 8 9 10 Mean2 Range3

78 64 185 136 28 268 1,500 31 275 719 328 ± 460 28 to 1,500

Calcium, ppm 788 801 930 444 120 822 766 930 11,200 4,100 2,090 ± 3,384 120 to 11,200

Potassium, ppm 2.70 2.50 2.30 5.40 2.40 1.37 2.30 2.92 4.04 6.03 3.20 ± 1.49 1.37 to 6.03

Copper, ppm 0.80 3.10 4.80 5.40 5.00 1.44 10.50 2.67 8.83 9.58 5.21 ± 3.42 0.8 to 10.5

Zinc, ppm

Iron, ppm 3.5 3.5 19.3 11.3 3.6 8.4 46.1 5.4 20.8 64.2 18.6 ± 20.7 3.6 to 64.2

2

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The glycerin samples were sent to a commercial laboratory for composition analysis (Minnesota Valley Testing Laboratories, New Ulm, MN). Mean ± SD of 10 glycerin products. 3 Range of values observed for 10 glycerin products.

1

Phosphorus, %

Sample

Table 3. Mineral composition of 10 glycerin products (as-fed basis)1

8.4 0.4 71.7 45.0 20.0 47.0 138.0 31.0 36.4 38.1 43.6 ± 38.9 0.4 to 138

Magnesium, ppm

<0.01 <0.01 0.90 0.90 5.00 0.39 2.10 0.31 0.93 2.05 1.26 ± 1.51 0.01 to 5.0

Manganese, ppm

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Jung and Batal: COMPOSITION OF GLYCERIN needs to be done to look at how methanol, sodium, potassium, and fat (free fatty acids) affect the ME value.

CONCLUSIONS AND APPLICATIONS



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Bregendahl. 2008. Nitrogen-corrected metabolizable energy value of crude glycerol for laying hens. Poult. Sci. 87:104– 107. 7. Gott, P. 2009. Variation in the chemical composition of crude glycerin. Honors Thesis. Ohio State Univ., Columbus. 8. Medinsky, M. A., and D. C. Dorman. 1995. Recent developments in methanol toxicity. Toxicol. Lett. 82– 83:707–711. 9. Skrzydlewska, E. 2003. Toxicological and metabolic consequences of methanol poisoning. Toxicol. Mech. Methods 13:277–293. 10. Röe, O. 1982. Species differences in methanol poisoning. Crit. Rev. Toxicol. 10:275–286. 11. Dorman, D. C., J. A. Dye, M. P. Nassise, J. Ekuta, B. Bolon, and M. A. Medinsky. 1993. Acute methanol toxicity in minipigs. Fundam. Appl. Toxicol. 20:341–347. 12. Soffritti, M., F. Belpoggi, D. Cevolani, M. Guarino, M. Padovani, and C. Maltoni. 2002. Results of long-term experimental studies on the carcinogenicity of methyl alcohol and ethyl alcohol in rats. Ann. NY Acad. Sci. 982:46–69. 13. Association of Official Analytical Chemists (AOAC). 2006. Official Methods of Analysis. 18th ed. Rev. 1. Official methods 990.03 (nitrogen), 990.03 (CP), 926.09 (crude fiber), 942.05 (ash), 963.03 (phosphorus), and 968.08 (minerals). Assoc. Off. Anal. Chem., Gaithersburg, MD. 14. Minnesota Valley Testing Laboratories, New Ulm, MN. 15. Sibbald, I. R. 1976. A bioassay for true metabolizable energy of feedingstuffs. Poult. Sci. 55:303–308. 16. Dale, N. M., and H. L. Fuller. 1984. Correlation of protein content of feedstuffs with the magnitude of nitrogen correction in true metabolizable energy determinations. Poult. Sci. 63:1008–1012. 17. SAS Institute. 2005. SAS User’s Guide: Statistics. Version 9.1.3 Edition. SAS Inst. Inc., Cary, NC. 18. Swiatkiewicz, S., and J. Koreleski. 2009. Effect of crude glycerin level in the diet of laying hens on egg performance and nutrient utilization. Poult. Sci. 88:615–619.

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1. Based on the research reported herein, the TMEn value can safely and conservatively be considered at least 80% of its GE. 2. Based on the considerable variation observed between the crude glycerin products from various biodiesel plants, it is critical that confirmatory analysis be conducted on every glycerin sample.

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