Chemical Composition, Fatty Acids Profile and Biological Evaluation of Tannins of Selected Date Seeds Grown in Iran 1 1 2* Research Article A
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Rezaeenia et al. Chemical Composition, Fatty Acids Profile and Biological Evaluation of Tannins of Selected Date Seeds Grown in Iran 1 1 2* Research Article A. Rezaeenia , A.A. Naserian and A. Mokhtarpour 1 Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran 2 Research Center of Special Domestic Animals, Research Institute at University of Zabol, Zabol, Iran Received on: 11 Feb 2016 Revised on: 19 Mar 2016 Accepted on: 15 Apr 2016 Online Published on: Sep 2016 *Correspondence E‐mail: [email protected] © 2010 Copyright by Islamic Azad University, Rasht Branch, Rasht, Iran Online version is available on: www.ijas.ir This study was conducted to evaluate the chemical composition and fatty acids profile of six predominant date seed cultivars grown in Iran including Barhi, Estamaran, Mazafati, Khasi, Kharak and Zahedi and the biological effects of their tannins based on in vitro gas production. Organic matter digestibility (OMD), metabolizable energy (ME) and concentration of short chain fatty acids (SCFA) were estimated after 24 h of incubation without or with inclusion of polyethylene glycol (PEG). Results showed that date seeds of all cultivars contained high amount of neutral detergent fiber (NDF), ether extract (EE) and total phenolics (TP), which ranged from 689 to 782, 82 to 118 and 41 to 110 g/kg DM, respectively. However, they had low levels of crude protein (CP) (50 to 69 g/kg DM) and ash (10 to 26 g/kg DM). Gas chromatography re- vealed that the major unsaturated fatty acid was oleic acid (40.13 to 46.35 g/100 g fatty acids), while the main saturated fatty acid was lauric acid (20.96 to 26.25 g/100 g fatty acids). Except for Estamaran, all cul- tivars had low OMD (<334 g/kg DM) and ME (<4.1 MJ/kg DM). Inclusion of PEG increased gas volume (GV), OMD, ME and SCFA (P<0.05) suggesting the inhibitory effect of date seed tannins on microbial fermentation. Total tannins were negatively correlated with nutritive value (OMD and ME) of date seeds. It can be concluded that despite low digestibility and ME, date seed may be considered as an alternative feed because of high amount of structural carbohydrates and EE. KEY WORDS date seed, fatty acids, gas production, phenolics. other nutrients in the diet (Al-Farsi et al. 2008). Further- INTRODUCTION more, physical properties of dietary fiber (e.g., particle size, Iran with an annual production of more than 1 million tons lignification, gravity, etc.) may modulate the rumination is the second producer of date (Phoenix dactylifera) around process and consequently the rumen health and animal pro- the world, playing an important role in the economic and ductivity (NRC, 2000). The potential dysregulation of ru- social life of Iranian people (FAO, 2013). The date fruit is men fermentation under heat stress in hot climates (Hall, composed of a fleshy pericarp and seed (pit) providing nu- 2009) may be more intensive due to use of high tannin- tritional needs of domestic animals as an alternative feed containing feeds in the ration. Determination of chemical (Hossain et al. 2014). However, before incorporating less- composition along with reaction properties of organic mat- known feedstuffs in the ruminant ration, it is important to ter of feedstuffs under laboratory assessments such as in have preliminary information on chemical and mineral vitro gas production have been widely used to evaluate the compositions of feeds because some chemical compounds nutritive value of feedstuffs in ruminant studies since 1979 such as tannins may negatively affect the bioavailability of (Menke et al. 1979) to now. This technique could be more Iranian Journal of Applied Animal Science (2016) 6(3), 517-524 517 Date Seeds Chemical Composition and Tannin Bioassay efficient than other in vitro methods to evaluate tannin- Phenolic compounds and tannins containing feeds (Getachew et al. 2002). Moreover, inclu- For total phenolics (TP) and total tannin (TT) measurement, sion of polyethylene glycol (PEG) in the gas production dried samples were ground to pass a 1 mm sieve and then technique can reveal the biological effect of tannins on or- 0.5 mm sieve. Before tannin extraction, fat was removed ganic matter digestibility during the fermentation (Makkar from dried samples by extracting with diethyl ether. Ap- et al. 1995) and the volume of produced gas in this method proximately 200 mg of samples were extracted in 10 mL is closely related to organic matter digestibility and ener- 70% aqueous acetone (v/v) with four replicates overnight at getic value of substrate (Menke and Steingass, 1988). An- room temperature (25 ˚C). After centrifugation (3000×g, 4 other source of variation in in vitro studies can be the ru- ˚C, 10 min) the supernatant was collected and kept in re- men liquor of donor animal because of diversity of rumen frigerator (4 ˚C). Folin-Ciocalteu reagent was used for microbial population (Menke and Steingass, 1988). In this quantification of TP and TT and tannic acid (Merck GmbH, research, we used an exceptional beef cattle native to the Darmstadt, Germany) was used as a standard (Makkar, southern-east of Iran called Sistani cow that is very resistant 2000). The values of TP and TT were expressed as tannic to harsh conditions in tropical regions and even long-term acid equivalent. drought. It has been suggested that the high ability of Sis- tani cow to adapt with rough climate may be partly due to Mineral composition its rumen ecosystem and resident microbiota (Mansoori et Potassium contents of ground samples were determined al. 2006). using the Sherwood model 410 Flame Photometer (Sher- Therefore, the aim of this study was to evaluate the wood Science Single Channel Flame Photometer) after ash- chemical and mineral composition and lipid profile of six ing and treating with concentrated HCl. Other minerals date palm seeds cultivated in Iran and to determine the bio- including P, Na, Ca, Mg, Zn and Fe were measured on Var- logical effects of their tannins on organic matter fermenta- ian SpectrAA-400 plus Atomic Absorption Spectrometer. tion. Oil extraction MATERIALS AND METHODS The oil extraction was conducted with Twisselmann appa- ratus. About 15 g of the grounded date seeds were extracted Date seed samples with petroleum ether, 40-60 ˚C (Merck, Darmstadt, Ger- Six fully ripened date seed cultivars including Barhi, Es- many) for 6 h. The solvent was removed by a rotary evapo- tamaran, Mazafati, Khasi (Khasui), Kharak and Zahedi rator (Heidolph Laborota 4000) at 40 ˚C. The seeds oil was were obtained from different farms located in southern transferred into screw capped test tubes and drained with provinces of Iran. Samples of Barhi, Estamaran and Khasi nitrogen and stored at –20 ˚C until further analysis. cultivars were collected from Khuzestan province and sam- ples of Mazafati, Kharak and Zahedi cultivars were col- Fatty acids composition lected from Kerman, Sistan and Baluchestan and Yazd The fatty acid composition was determined according to provinces, respectively. Air dried samples were ground to ISO standard ISO 5509:2000, (ISO, 2000) procedure. The pass a 1 mm sieve by a cyclic mill. FAs of the oil samples were converted into methyl esters (FAMEs). FAMEs were identified on a Shimadzu Gas Chemical analysis chromatography (GC)-17A with a capillary column, Su- Proximate analysis pelco SPTM-2330 (30 m×0.32 mm×0.20 μm film thickness). Dry matter content of date seed samples was determined by The column temperature was programmed from 60 to 190 drying in an oven at 100 ˚C to a constant weight (method ˚C at 10 ˚C/min and held for 2 min, then heated to 220 ˚C at 934.01) (AOAC, 2005). Ash (method 942.05), ether extract 2 ˚C/min. The injector and detector temperatures were set at (method 920.39), acid detergent fiber (ADF) and lignin 250 ˚C. The carrier gas was high pure nitrogen. The peak (method 973.18) were determined according to AOAC areas were computed by the integration software and per- (2005). Crude protein (Kjeldahl N×6.25) was determined centages of FAMEs were obtained as weight percent by by the Block Digestion Method (method 2001.11) on direct internal normalization. Two replicates were injected Kjeltec 2300 Autoanalyzer, Foss Tecator AB, Hoganas, for each sample. Sweden) as described in AOAC (2005). Neutral detergent fiber (NDF) was determined by the procedure of Van Soest In vitro tannin bioassay et al. (1991). The sodium sulphite and α-amylase were not To investigate the biological effects of tannins, in vitro gas used and both NDF and ADF were expressed exclusive of production was carried out using PEG as described by residual ash. Makkar (2000). Briefly, 500 mg dry weight of date seed 518 Iranian Journal of Applied Animal Science (2016) )3(6 , 517 5- 24 Rezaeenia et al. samples were incubated without and with 1 g PEG The highest concentration of ADF and EE were observed (MW=6000) and filled with 40 mL rumen liquor and buffer in Barhi with the content of 577.7 and 118.0 g/kg DM, re- mixture in triplicate. Rumen fluid was obtained from three spectively. The highest amount of NDF was observed in fistulated Sistani cows fed with corn silage and concentrate Mazafati (782.3 g/kg DM). The content of lignin among with a ratio of 70:30, before the morning feeding. Culture cultivars ranged from 101.4 to 133.5 g/kg DM. bottles were placed in a water bath at 39 ˚C and gas produc- Of the cultivars studied, significant differences in TP and tion in the head space of each bottle was read from the dis- TT contents of date seeds were observed (Table 1).