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Effect of dietary supplementation with olive pomaces on the performance and meat quality of growing rabbits
Meat Science 92 (2012) 783–788
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Effect of dietary supplementation with olive pomaces on the performance and meat quality of growing rabbits A. Dal Bosco a,⁎, E. Mourvaki a, R. Cardinali a, M. Servili b, B. Sebastiani c, S. Ruggeri a, S. Mattioli a, A. Taticchi b, S. Esposto b, C. Castellini a a b c
Department of Applied Biology, Section of Animal Science, University of Perugia, Borgo XX Giugno 74, 06126 Perugia, Italy Department of Food Science and Economics, Section of Food Technology and Biotechnology, University of Perugia, Via San Costanzo, 06126 Perugia, Italy Department of Public Health, Section of Molecular Epidemiology and Environmental Hygiene, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
a r t i c l e
i n f o
Article history: Received 5 April 2012 Received in revised form 3 July 2012 Accepted 4 July 2012 Keywords: Meat quality Olive pomace Ortho-diphenols Polyphenols Productive performance Rabbit
a b s t r a c t The aim was to investigate the effects of three types (A, B and C) of stoned and dehydrated olive pomaces (OPs), differing in olive cultivar, on productive performance and meat quality of growing rabbits. The inclusion of OPs (5%) negatively affected the performance of rabbits as it reduced the feed intake, growth rate, carcass weight and dressing out percentage (P b 0.05). Compared with the control, the meat of OP rabbits had a greater amount of monounsaturated and a lower amount of polyunsaturated fatty acids (P b 0.05), independent of the type of OP used. Oxidative processes in the meat of OPA and OPB were higher (P b 0.05), whereas OPC showed the same levels as the control group. This was due to the higher total polyphenol concentration and to the concomitant lower peroxide value of OPC. These results recommend the use of OP in rabbit diet with caution, taking into account the quality of the by-product in terms of oxidative status. © 2012 Elsevier Ltd. All rights reserved.
1. Introduction The cultivation of the olive tree (Olea europaea L.) is widespread in the Mediterranean area, where olive oil is widely used as a food in many parts of the world. Following the industrial extraction of oil from olive fruits, great amounts of by-products are obtained. Olive pomace (OP) is a solid heterogeneous mixture of olive skin, pulp, woody endocarps and seeds. This waste material represents approximately 35% (w/w) of the processed olives, in relation to the olive cultivar and the extraction method used. Unprocessed OP still contains a small amount of olive oil and is generally characterized by a high content of crude fiber and sugars (mainly polysaccharides) and moderate values of crude protein and fatty acids, chiefly oleic (C18:1n−9) and other C2–C7 fatty acids (Karantonis et al., 2008). A variety of substances with proven antioxidant and radical scavenging activity, such as hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and their secoiridoid derivatives (dialdheydic form of decarboxymethyl elenolic acid, 3,4-DHPEA-EDA or p-HPEA-EDA) as well as verbascoside, is also contained in OP (Amro, Aburjai, & Al-Khalil, 2002; Servili, Baldioli, Mariotti, & Montedoro, 1999).
Abbreviations: FA, fatty acid; OP, olive pomace; TBARS, thiobarbituric acid reactive substances. ⁎ Corresponding author. Tel.: +39 0755857110; fax: +39 0755857122. E-mail address: [email protected] (A. Dal Bosco). 0309-1740/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2012.07.001
The amount of OP oil (approximately 8%) and water depends on the applied process and on the operating conditions (Kiritsakis, 1998). Moreover, the chemical composition of OPs may vary widely in relation to the agronomic and technological conditions of production. Additionally, the olive cultivar is one of the most important factors that affect the phenolic concentration of olive oil and by-products (Martin Garcia, Moumen, Yanez Ruiz, & Molina Alcaide, 2004; Servili et al., 2004; Servili et al., 2011). Based on the above characteristics, OPs have been proposed as alternative sources of nutrients for domestic animal feeding (www.fao.org). Among domestic ruminants, goats seem to be adapted for utilizing this high lignin-cellulose/low protein feedstuff (Molina Alcaide, Yànez Ruìz, Moumen, & Martìn Garcìa, 2003). The other ruminants require an adequate supply of protein nitrogen for the ruminal microorganisms and/or addition of specific de-activating tannin compounds (Al Jassim, Awadeh, & Abodabos, 1997; Martin Garcia et al., 2004; Molina Alcaide et al., 2003). Concerning monogastric animals such as rabbits, very little data are available (Dal Bosco et al., 2007; Rupic et al., 1999; Tsantila et al., 2007). In particular, Carraro, Trocino, and Xiccato (2005) investigated the possibility of including OPs in rabbit diets as a source of indigestible fiber in order to obtain a better equilibrium between the different fiber fractions and reducing the sanitary risk. Rupic et al. (1999) and Dal Bosco et al. (2007) investigated the effect of dietary OP inclusion on the in vivo parameters of fattening rabbits. Tsantila et al. (2007) reported that OPs contain specific antagonists of the platelet activating factor, with bioactivity similar to olive oil, which in turn has an effect in inhibiting atherosclerosis development in rabbits. These compounds
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could be useful in producing foods with higher nutritional value, as they are in olive oil industry by-products (Karantonis et al., 2008). The role of OP-derived bioactive polyphenols in rabbit meat quality and oxidative stability has never been investigated. Based on these considerations, the present investigation was undertaken to evaluate the effects of dietary supplementation with three types of stoned and dried OPs, derived from olive cultivars that yielded differences in the performance and meat quality of growing rabbits. 2. Materials and methods 2.1. Animals and diets All procedures were carried out under EU Regulations for experiments on living animals (EFSA, 2004). The study was carried out in the experimental rabbitry section of the Department of Applied Biology (University of Perugia) where one hundred and sixty weaned (30 d) New Zealand white rabbits were housed in bicellular cages located in the same air-conditioned room (temperature ranging from 15 to 20 °C and relative humidity from 65 to 70%). Rabbits were divided into four homogeneous groups and fed ad libitum isoenergetic and isoproteic diets: control diet and three diets where barley was replaced with 5% dried, stoned OP (i.e., A, B, and C). The control diet was formulated according to the current recommendations for growing rabbits (De Blas & Mateos, 1998). In detail, OPA was a pomace mixture of various olive cultivars (Coratina, Moraiolo, Frantoio and Ogliarola), whereas OPB and OPC were obtained from Frantoio and Coratina olive cultivars, respectively. With regard to the antioxidant content, the different OPs were characterized by low (OPA), medium (OPB) and high (OPC) phenolic concentrations. The dehydration of the stoned OPs was carried out in a pilot plant by a fluid bed dryer with an operative capacity of 50 kg/h. The inlet temperature of the air was 120 °C, whereas the mean temperature for drying was 45–50 °C. The formulation and chemical composition of the diets are reported in Table 1. Dry matter was determined by oven drying at 105 °C overnight (AOAC, cod. 930.15, 1995). Crude protein was measured by a Kjeldahl nitrogen analysis (AOAC cod. 954.01, 1995). Ash content was determined by combusting for 3 h at 550 °C. Neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) content were determined according to Van Soest, Robertson, and Lewis (1991). Lipids were extracted by diethyl ether using a Soxhlet apparatus. At 75 d, 20 rabbits per group, with weights close to the average of the group (± 10%), were selected and slaughtered, under veterinary supervision of the University of Perugia, in the departmental processing plant 12 h after feed withdrawal; the animals did not undergo transport. Specifically, the rabbits were killed by cutting their carotid arteries and jugular veins following electro-stunning and carcasses were prepared according to Blasco and Ouhayoun (1996). After carcass chilling (24 h at + 4 °C), the two longissimus lumborum muscles were removed and carefully freed from connective and adipose tissues. 2.2. Quality evaluation of olive cakes For the extraction of residual oil from the olive cakes, 250 mL of hexane was added to 100 g of the pomace. The mixture was homogenized with a T50 Ultraturrax for 1 min at 44 ×g for 10 min at 20 °C and then filtered with filter paper (Whatman no. 1). The extraction was performed in duplicate. The filtered homogenate was evaporated under vacuum in a nitrogen flow at 35 °C. The peroxide value, free acidity and fatty acid composition of the residual oil were measured in accordance with the European Official Methods (UE 1989/2003 modifying the ECC 2568/91).
Table 1 Formulation and chemical composition of control and of enriched diets with olive pomace A (mixed cultivars), B (Frantoio) or C (Coratina). Control diet
Diet A
Diet B
Diet C
30.00 10.00 18.00 25.00 12.00 – – – 1.35 1.20 1.00 0.70 0.70 0.05 89.00
30.00 10.00 18.00 20.00 12.00 5.00 – – 1.35 1.20 1.00 0.70 0.70 0.05 90.09
30.00 10.00 18.00 20.00 12.00 – 5.00 – 1.35 1.20 1.00 0.70 0.70 0.05 90.58
30.00 10.00 18.00 20.00 12.00 – – 5.00 1.35 1.20 1.00 0.70 0.70 0.05 90.20
Proximate composition (% fresh matter) Moisture 11.00 Crude protein 17.35 Ether extract 2.00 Ash 7.25 Fiber 12.88 NDF 24.07 ADF 14.13 ADL 2.90 Hemicellulose 9.94 Digestible energyb MJ/kg f.m. 10.55
9.91 17.84 2.18 6.85 13.10 25.49 15.65 3.22 9.75 10.78
9.42 17.77 2.55 7.25 12.95 26.00 14.94 3.02 10.06 10.60
9.80 17.70 2.60 6.99 13.00 24.84 15.15 2.95 10.91 10.75
Ingredients (% wet weight) Alfa–alfa hay Corn meal Soybean meal 48% Barley Wheat bran OPA OPB OPC Ca-phosphate Vitamin mineral premixa Molasses Salt Ca-carbonate DL-methionine Dry matter
a Added per kg: vit. A U.I. 11.000; vit. D3 U.I. 2.000; vit. B1 2.5 mg; vit. B2 4 mg; vit. B6 1.25 mg; vit. B12 0.01 mg; vit. E 25 mg; biotin 0.06 mg; vit. K 2.5 mg; niacin 15 mg; folic ac. 0.30 mg; D-pantothenic ac. 10 mg; choline 600 mg; Mn 60 mg; Cu 3 mg; Fe 50 mg; Zn 15 mg; I 0.5 mg; Co 0.5 mg; lysine 50 mg; methionine 40 mg. b Estimated according to Maertens, Moermans, and De Groote (1988).
The concentrations of total phenols and orthodiphenols for each OP and experimental diet were determined colorimetrically, according to Montedoro, Servili, Baldioli, and Miniati (1992). The phenolic compounds were extracted from the OPs by modifying the procedure previously described by Servili, Baldioli, Selvaggini, Macchioni, & Montedoro (1999). Ten grams of PO were homogenized with 100 mL of 80% methanol containing 20 mg/L of sodium diethyldithiocarbamate (DIECA); the extraction was performed in triplicate. After the removal of the methanol, the aqueous extract underwent SPE phenol separation. The SPE procedure was performed by loading 1 mL of the aqueous extract into a 5 g/25 mL Extraclean highload C18 cartridge (Alltech Italia S.r.l., Sedriano, Italy). Methanol (50 mL) was used as the eluting solvent. After removing the solvent under vacuum at 30 °C, the phenolic extract was recovered and then dissolved in methanol (1 mL). The reversed-phase HPLC analyses of the phenolic extracts were conducted with an Agilent Technologies system Mod. 1100 (Agilent Technologies Italia S.p.A., Cernusco sul Naviglio, Milano, Italy), which was composed of a vacuum degasser, a quaternary pump, an autosampler, a thermostatted column compartment, a Diode-Array Detector (DAD), and a fluorescence detector (FLD). To evaluate the phenolic compounds (Selvaggini et al., 2006), a Spherisorb column ODS-1 250 × 4.6 mm with a particle size of 5 μm (Phase Separation Ltd., Deeside, U.K.) maintained at 25 °C was employed, and a 20 μL sample volume was injected. The mobile phase was composed of 0.2% acetic acid (pH 3.1) in water (solvent A)/methanol (solvent B) at a flow rate of 1 mL/min. The gradient was changed as follows: 95% A/5% B for 2 min, 75% A/25% B in 8 min, 60% A/40% B in 10 min, 50% A/50% B in 16 min, and 0% A/100% B in 14 min. This composition was maintained for 10 min and was then returned to the initial conditions and equilibration in 13 min; the total running time was 73 min. Lignans were detected using the FLD operated at an excitation wavelength of 280 nm and emission at 339 nm
A. Dal Bosco et al. / Meat Science 92 (2012) 783–788
(Selvaggini et al., 2006), whereas the other compounds were detected using the DAD with wavelength of 278 nm. 2.3. Determination of the lipid fatty acid profile of olive cakes and diets The fatty acid (FA) profile of OPs and diets was determined by gas-chromatography (Fisons Mega 2, equipped with a flame ionization detector; Fisons Instruments S.p.A., Rodano, Milano, Italy) after lipid extraction (Folch, Lees, & Sloanes-Stanley, 1957) and consecutive hot derivatization with a methanolic solution of sulfuric acid (3%). Separation of the resulting fatty acid methyl esters (FAME) was carried out on an Agilent (J&W) capillary column (30 m × 0.25 mm I.D.) coated with a DB-Wax stationary phase (film thickness of 0.25 mm). The individual FA methyl esters (FAME) were identified by reference to the retention time of authentic FAME standards. The relative proportion of each FA in the samples was expressed as a percentage of total FA and calculated with Chrom-Card software.
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Dietary indexes of atherogenicity (AI) and thrombogenicity (TI) were evaluated as proposed by Ulbricht and Southgate (1991), while the peroxidability index (PI) was determined according to Arakawa and Sagai (1986). The extent of muscle lipid peroxidation was evaluated by a spectrophotometer at 532 nm, (Hitachi U-2000, Theodor‐Heuss‐Anlage 12, Mannheim, F.R. Germany), which measured the absorbance of thiobarbituric acid-reactive substances (TBARS), and a tetraethoxypropane calibration curve in sodium acetate buffer (pH = 3.5, Dal Bosco et al., 2009). The results were expressed as malondialdehyde (MDA) mg/kg muscle. 2.5. Statistical analysis The data are presented as the least square means and least significant differences at 5%. The data were processed using the GLM procedure of Stata (StataCorp, 2005), based on a linear model that evaluates the fixed effect of dietary treatments.
2.4. Evaluation of rabbit meat quality parameters 3. Results Proximate analyses of longissimus lumborum muscles were carried out according to the Association of Official Analytical Chemists (AOAC, 1995). In particular, moisture, ash, and total nitrogen content were obtained using the N. 950.46B, 920.153, and 928.08 methods, respectively. The total protein content was calculated using Kjeldahl nitrogen and a conversion factor of 6.25. The total lipid content was extracted from 5 g of each homogenized sample and calculated gravimetrically (Folch et al., 1957). Ultimate pH (pHu) was measured at 24 h with a Knick digital pH meter (Broadly Corp., Santa Ana, CA, USA) after homogenization of 1 g of raw muscle for 30 s in 10 mL of 5 M iodoacetate (Korkeala, Mäki-Petais, Alanko, & Sorvettula, 1984). The water holding capacity (WHC) was estimated (Nakamura & Katoh, 1985) by centrifuging 1 g of whole muscle placed on tissue paper inside a tube for 4 min at 1500 ×g. The remaining water after centrifugation was quantified by drying the samples at 70 °C overnight. The WHC was calculated as follows: (weight after centrifugation −weight after drying) /initial weight× 100. Whole samples of both muscles (approximately 20 g) were placed in open aluminum pans and roasted in an electric oven (pre-heated to 200 °C) for 15 min to an internal temperature of 80 °C (Cyril, Castellini, & Dal Bosco, 1996). Cooking loss was estimated as the percentage of the weight of the roasted samples (cooled for 30 min to approximately 15 °C and dried on the surface with a paper towel) with respect to the raw samples. Shear force was evaluated on the cores (1.25 cm × 2 cm) obtained from the mid-portions of the roasted samples (as above) by cutting them perpendicularly to the direction of the fiber using an Instron Model 1011 equipped with a Warner-Blatzler Meat Shear Apparatus (Instron, Test and Measurement, Trezzano sul Naviglio, Milano, Italy). The color parameters (L*, a*, b*) for the raw muscles were measured using a tristimulus analyzer (Minolta Chroma Meter CR-200, Azuchi-Machi Higashi-Ku, Osaka 541, Japan) with the Cielab (1976). The L*a*b* color system consists of a luminance or lightness component (L*) and two chromatic components: the a° component from green (− a) to red (+a) and the b* component from blue (− b) to yellow (+b) colors. The colorimeter was calibrated using a standard pink plate. It has an 8 mm diameter measuring area and uses diffuse illumination and 0° viewing angle (spectral component included) for accurate measurement of a wide variety of subjects. The fatty acid profile was determined by gas-chromatography using the procedures previously described for OPs and diets. The average amount of each fatty acid was used to calculate the sum of the saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids.
3.1. Effects of the olive cultivar on the biochemical characteristics of OPs The main biochemical characteristics of the three types of OPs are reported in Table 2. Olive cake C had the highest total polyphenol concentration, followed by OPB, whereas OPA had almost half the quantity of OPC. The most abundant phenols were 3,4-DHPEA-EDA and verbascoside. OPs B and C were also very rich in p-HPEA-EDA. A reverse order was observed for the peroxide number and free acidity (OPA > OPB > OPC). As a consequence, the concentration ratio between peroxide number and ortho-diphenols was higher in OPC than in the other two OPs, suggesting a higher oxidative stability. Gas-chromatography analysis of OP lipids revealed that oleic acid was the predominant FA in all of the OPs, with the highest concentration found in OPC, followed by OPB. As a result, OPC had a 2-fold lower saturated/unsaturated ratio compared to OPA and OPB. Of all the OPs, the proportion of the PUFA n − 6 series was higher than in the PUFA n −3 series. Table 2 Polyphenol profile (g/kg dry weight) and other quality parameters of the olive pomace A (mixed olive cultivars), B (Frantoio) and C (Coratina). Determined by HPLCa
3,4-DHPEA p-DHPEA Verbascoside 3,4-DHPEA-EDA p-HPEA-EDA (+)-1-Acetoxypinoresinol Lutein Ortho-diphenols Free acidity (g of oleic acid/100 g of oil) Peroxide number (meq O2/kg oil) Peroxide/ortho-diphenols Fatty acid composition (% of total) C16:0 C18:0 C18:1n−9 C18:2n−6 C18:3n−3 Total SFA Total MUFA Total PUFA Saturated/unsaturated FAb PUFA (n−3/n−6)
Olive pomace A
B
C
1.3 ± 0.01 0.7 ± 0.01 9.7 ± 0.1 8.3 ± 0.6 1.1 ± 0.01 0.6 ± 0.01 n.d. 4.1 ± 0.4 6.1 ± 0.4 21.4 ± 1.3 5.2 ± 0.6
1.5 ± 0.01 1.0 ± 0.01 9.9 ± 1.0 17.0 ± 1.7 6.9 ± 0.7 0.6 ± 0.1 0.8 ± 0.1 8.0 ± 0.8 4.0 ± 0.2 15.3 ± 0.9 1.9 ± 0.2
1.1 ± 0.01 1.4 ± 0.01 11.8 ± 0.1 22.0 ± 1.2 10.1 ± 0.1 1.1 ± 0.01 1.2 ± 0.01 9.9 ± 1.0 3.4 ± 0.1 9.8 ± 0.5 1.1 ± 0.1
13.8 ± 0.3 2.2 ± 0.1 69.4 ± 1.8 9.5 ± 0.3 1.0 ± 0.1 16.1 ± 0.2 69.4 ± 1.7 10.5 ± 0.4 0.2 ± 0.1 0.1 ± 0.1
13.0 ± 0.2 2.6 ± 0.1 74.0 ± 1.6 7.6 ± 0.2 1.1 ± 0.2 15.6 ± 0.4 74.0 ± 1.6 8.7 ± 0.2 0.2 ± 0.1 0.2 ± 0.1
11.8 ± 0.3 2.6 ± 0.1 76.3 ± 1.8 7.7 ± 0.4 0.9 ± 0.1 14.4 ± 0.2 76.3 ± 1.7 8.7 ± 0.4 0.1 ± 0.1 0.1 ± 0.1
Each value represents the mean of three replicate analyses. a The phenolic content is reported as the mean value of four independent samplings. b Unsaturated FA is defined as the sum of MUFA and PUFA.
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3.2. Effects of OP inclusion on the chemical and biochemical composition of diets Inclusion of OP in the standard diet resulted in a slight increase in ether extract, independent of the type of OC used, without affecting the energy content of the diets (Table 1). Regarding the FA pattern of the ether extract, OP-enriched diets had a higher proportion of MUFA and a concomitant lower proportion of PUFA compared to the control diet (Table 3). The resulting saturated/unsaturated FA ratio of the diets was affected by these changes, and the OP diets showed lower values with respect to the control diet. Oleic acid was the predominant FA of OP-enriched diets, while linoleic acid was the most representative FA in the control diet. The OPC diet had the highest level of oleic acid.
Control
Group A
Group B
Group C
Mortality (%) 10 13 15 10 Weaning weight 561 558 554 560 (g) 2,510a 2,450a 2,590b Slaughter weight 2,640c (g) 43.4a 42.1a 45.1b Daily weight gain 46.2c (g) 128.0a 126.4a 135.3b Daily feed intake 143.9c (g) Feed conversion (g) 3.1 2.9 3.0 3.0 Carcass weight (g) 1,610b 1,500a 1445a 1,595b b ab a Dressing out (%) 61 60 59 59a
P value SED – 0.657
3⁎ 49
0.042
47
0.002
3.1
0.047
11.5
0.523 0.041 0.036
0.09 105 1.3
N = 20 per group; a,b,c: Least square means in the same row with different superscript letters are significantly different (P b 0.05); SED: standard error deviation. ⁎ χ2, P b 0.05.
3.3. Influence of olive pomace on the productivity of rabbits The inclusion of OPs reduced the feed intake of the diets from 5% (OPC) to 16% (OPA–OPB). Accordingly, rabbits fed the OPA and OPB diets had a lower daily weight gain and lower slaughter and carcass weights (P b 0.05) with respect to the control and OPC-treated rabbits (Table 4).
3.4. Effects of OC dietary supplementation on meat quality The proximate composition and physical traits of longissimus lumborum muscle were not affected by OP (Table 5). On the contrary, the fatty acid profiles, dietary indexes and oxidative status of meat underwent several modifications in relation to the OP used (Table 6). In detail, dietary treatment with OP resulted in a significant (P b 0.05) increase of MUFA, to the detriment of PUFA (P b 0.05), in meat. The proportion of SFA was reduced, reaching statistical significance (P b 0.05) only for the meat of the OPC-treated rabbits. This group had the greatest proportion of MUFA (chiefly oleic acid) but the lowest proportion of PUFA (especially linoleic acid). As a consequence, the ratio between saturated and unsaturated FAs was also lower. The changes in meat fatty acids due to OP were responsible for the changes in the dietary quality indexes. Accordingly, the peroxidability index was lower (P b 0.05) in all meat samples that were derived from OP-treated rabbits, whereas the atherogenic and thrombogenic indexes were significantly (P b 0.05) reduced only in OPC. The oxidative stability of the meat lipid was also affected by OP supplementation, and the magnitude was related to the OP used. Meat from the OPB group had the greatest (P b 0.05) TBARS level and was therefore the most susceptible to lipid peroxidation with respect to the other groups. Table 3 Fatty acid composition of control and olive pomace-enriched diets (A — mixed cultivars; B — Frantoio and C — Coratina). Fatty acids (% of total)
Control
Diet A
Diet B
Diet C
C14:0 C16:0 C18:0 C18:1n−9 C18:2n−6 C18:3n−3 Total SFA Total MUFA Total PUFA Saturated/unsaturated FAa PUFA (n−3/n−6)
1.2 ± 0.1 19.5 ± 1.4 3.1 ± 1.1 16.9 ± 1.4 41.5 ± 2.3 14.7 ± 1.2 24.3 ± 1.1 18.8 ± 1.8 56.9 ± 2.8 1.2 ± 0.8 0.3 ± 0.1
0.8 ± 0.07 17.8 ± 1.0 2.9 ± 1.1 35.7 ± 2.2 29.7 ± 1.1 11.5 ± 1.8 20.4 ± 2.7 37.0 ± 2.4 42.7 ± 2.8 0.8 ± 0.08 0.4 ± 0.04
0.76 ± 0.01 17.0 ± 1.8 2.8 ± 1.9 43.7 ± 2.5 26.3 ± 1.3 8.0 ± 0.8 20.0 ± 1.8 44.8 ± 2.5 35.2 ± 2.2 0.7 ± 0.2 0.3 ± 0.1
0.6 ± 0.33 16.6 ± 1.5 2.6 ± 1.2 47.0 ± 2.8 26.8 ± 2.0 8.8 ± 1.1 19.0 ± 2.4 46.6 ± 2.8 34.4 ± 2.7 0.6 ± 0.08 0.3 ± 0.15
Each value represents the mean of three replicate analyses. a Unsaturated FA is defined as the sum of MUFA and PUFA.
Table 4 Productive performance of rabbits as affected by the inclusion of different types of olive pomace (A, B and C) in the standard diet.
4. Discussion There are many factors that affect the quality of OPs; olive cultivar, fruit quality, technological process and storage are the most important (Servili, Baldioli, Mariotti, et al., 1999). The OPs tested in this trial were obtained by a three-phase olive oil extraction from various Italian olive cultivars using stoned olives after oil separation and were characterized by different phenolic contents. Coratina is known to be the richest olive cultivar in terms of polyphenols, and this may explain the abundance of these compounds in the derivation of OP with respect to Frantoio, which is obtained under the same industrial conditions. The differences in polyphenol content among the OPs might be due to the observed differences in rancidity, defined as the peroxide value. Indeed, the degree of Frantoio OP autoxidation was higher than that of Coratina, although they both had the same proportion of unsaturated FAs. Based on the ratio between the peroxide value and the polyphenols, the studied OPs could be classified as high (Coratina), medium (Frantoio) or low quality (mixture). It should be noted that this parameter refers to the antioxidant properties of OP, giving limited information on the nutritional value of the OP. In this study, the FA composition of the OP lipids was also evaluated, which revealed substantial differences in oleic acid concentration among the different OPs (Coratina > Frantoio > mixture). The data demonstrated for the first time that meat quality can be seriously affected by the quality of the OP used in rabbit diet. The rabbits that were fed a diet containing OPC had the highest oxidative stability and nutritional value, as revealed by the low concentration of lipid peroxidation and the high nutritional indexes, respectively. It
Table 5 Proximate composition and physical traits of meat samples from rabbits fed a control or enriched diet with olive pomace A (mixed cultivar), B (Frantoio) and C (Coratina). Variable
Control
Proximate composition (g/100 g) Moisture 75.02 Protein 21.35 Lipids 2.19 Ash 1.44 Physical traits pHu 5.50 WHC (%) 55.08 Cooking loss (%) 34.69 Tenderness (kg/cm2) 2.78 Color L* 63.71 a* 6.90 b* 0.39
Group A
Group B
Group C
P value
SED
75.1 20.91 2.64 1.35
74.99 20.93 2.72 1.36
75.24 20.62 2.59 1.55
0.358 0.098 0.261 0.075
2.26 1.21 0.49 0.30
5.56 55.29 34.68 2.25
5.40 54.19 35.06 2.42
5.58 55.36 34.56 2.61
0.326 0.084 0.694 0.320
0.37 2.24 1.72 0.49
62.06 5.18 0.49
61.91 5.18 0.60
62.43 5.12 0.61
0.362 0.095 0.071
2.08 2.18 0.24
N = 20 per group; SED: standard error deviation.
A. Dal Bosco et al. / Meat Science 92 (2012) 783–788 Table 6 Fatty acid composition (% of total fatty acids), dietary indexes and oxidative status of rabbit meat fed with control diet, olive pomace A (mixed cultivar), B (Frantoio) and C (Coratina). Variable C14:0 C16:0 C18:0 Others Total SFA C14:1n−6 C16:1n−7 C18:1n−9 Others Total MUFA C18:2n−6 C20:3n−6 C20:4n−6 C18:3n−3 C20:3n−3 C20:5n−3 C21:5n−3 C22:5n−3 C22:6n−3 Others Total PUFA Saturated/unsaturated PUFA (n−3/n−6)
Control b
2.58 28.15 8.16b 2.15 41.04b 0.26 3.52b 23.78a 0.76 28.32a 20.13b 0.39 3.81 2.74 0.11 0.46 0.25 0.78b 0.53 1.42 30.64b 0.70b 0.20
A
B a
3.15 29.01 6.54ab 2.57 41.27b 0.23 2.98ab 26.67b 0.87 30.75b 17.57a 0.37 4.12 2.39 0.05 0.38 0.34 0.69b 0.48 1.60 27.98a 0.70b 0.19
Dietary indexes and oxidative status Atherogenicity index 0.67b 0.74c Thrombogenicity index 0.95b 0.98b Peroxidability index 59.24b 55.74a TBARs (μmol/L) 0.80a 1.20ab
C b
a
P value
SED
2.73 27.24 7.38ab 2.30 39.66b 0.19 2.45a 28.15c 1.25 32.04c 18.62ab 0.44 3.91 2.31 0.09 0.30 0.37 0.59a 0.36 1.27 28.30a 0.66b 0.17
2.31 27.60 5.03a 2.15 37.09a 0.24 2.41a 32.56d 1.31 36.52d 16.84a 0.32 3.53 2.29 0.06 0.42 0.39 0.61ab 0.57 1.38 26.39a 0.59a 0.21
0.002 0.154 0.021 0.240 0.035 0.068 0.046 0.003 0.063 0.001 0.027 0.258 0.094 0.247 0.095 0.107 0.087 0.048 0.301 0.074 0.006 0.024 0.061
0.21 2.22 1.22 0.13 1.12 0.18 0.40 2.05 0.34 1.41 1.20 0.16 1.29 0.80 0.06 0.14 0.12 0.12 0.16 0.30 2.42 0.06 0.06
0.65b 0.94b 53.84a 1.45b
0.60a 0.84a 53.07a 0.77a
0.003 0.039 0.041 0.007
0.04 0.09 3.02 0.19
N = 20 per group; a,b,c,d: Least square means in the same row with different superscript letters are significantly different (P b 0.05); SED: standard error deviation.
is likely that the high polyphenol content of OPC prevented the oxidation of unsaturated lipids, contributing to the preservation of the dietetic-nutritional value of the meat. Among the polar phenolic compounds, ortho-diphenols such as hydroxytyrosol 3,4-DHPEA-EDA and verbascoside have the best antioxidant activity and are good radical scavengers (Badioli, Servili, Perretti, & Montedoro, 1996). In particular, it has been demonstrated that hydroxytyrosol may scavenge aqueous peroxyl radicals near the membrane surface, while oleuropein may block/inhibit the chain propagating lipid peroxyl radicals within membranes (Saija et al., 1998). A great amount of hydroxytyrosol (in the form of 3,4-DHPEA-EDA) and verbascoside was contained in OPC, which supports this hypothesis, while the other OPs had a lower proportion. The beneficial effects of olive polyphenols on the oxidative status of meat have also been reported by Paci, Schiavone, and Marzonim (2001), who used oleuropein, an immediate precursor of hydroxytyrosol, further corroborating the present findings. The high dietetic indexes in the meat of OPC-treated rabbits should probably be ascribed to the higher oleic acid content and to the concomitant lower SFA concentration found in this type of olive oil waste. This is an important issue as monounsaturated acids, including oleic acid, have been shown to reduce plasma total cholesterol and low-density lipoprotein cholesterol, and their consumption is highly recommended to prevent cardiovascular diseases (Gurr, Borlak, & Ganatra, 1989). Although OP intake, especially Coratina, improved meat quality, the productive performance of the rabbits was slightly reduced. It should be noted that all the OP-enriched diets provided similar digestible energy to the rabbits. Nevertheless, the former diets had a slightly higher ether extract, NDF and hemicellulose levels, which may explain this phenomenon. It is well-known that high dietary hemicellulose decreases voluntary feed intake and, hence, rabbit
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weight (Gidenne, Pinheiro, & Falcão, 2000). In addition, OPs generally have low palatability and may contain anti-nutritional compounds that are able to complex proteins and sugars, limiting their nutrient availability. Carraro et al. (2005) reported that daily weight gain and final live weight were not affected by the inclusion of 3 and 6% of olive stone meal, but at the same time observed a decrease of daily feed intake as a consequence of OP supplementation. In another study aimed to evaluate the dietary effect of OP inclusion (20%) in an Algerian population of rabbits, Kadi, Belaidi-Gater, and Chebat (2004) concluded that crude olive cake seems to replace the alfalfa-like source of fiber and does not seem to influence the performance or carcass characteristics of growing rabbits. It is therefore clear that future studies are warranted to better clarify the abovementioned aspects, specifically to determine the types and concentrations of tannins or other anti-nutritional compounds contained in OPs. 5. Conclusions In conclusion, the data showed for the first time that the nutritional quality of rabbit meat can be improved by adding a 5% concentration of OP to the standard diet. To achieve this goal, only OPs of high quality in terms of pro-oxidant/antioxidant content should be used. Specifically, OPs with a peroxide value less than 10 meq/kg and an ortho-diphenol concentration higher than 20 g/kg can guarantee a satisfactory meat oxidative stability. Lastly, the findings support the notion that feeding rabbits with OPs could be an alternative strategy to enrich meat in precious monounsaturated FAs, such as oleic acid, which has recognized beneficial effects on human health. Other investigations are needed in order to improve the feed formulation and consequently rabbit performance that was slightly worsened by OP supplementation. References Al Jassim, R. A. M., Awadeh, F. D., & Abodabos, A. (1997). Supplementary feeding value of urea-treated olive cake when fed to growing Awassi lambs. Animal Feed Science and Technology, 64, 287–292. Amro, B., Aburjai, T., & Al-Khalil, S. (2002). Antioxidative and radical scavenging effects of olive cake extract. Fitoterapia, 73, 456–461. AOAC (1995). Official methods of analysis (15th ed.). Washington, DC, USA: Association of Official Analytical Chemist. Arakawa, K., & Sagai, M. (1986). Species difference in lipid peroxide levels in lung tissue and investigation of their determining factors. Lipids, 21, 769–778. Badioli, M., Servili, M., Perretti, G., & Montedoro, G. F. (1996). Antioxidant activity of tocopherols and phenolic compounds in virgin olive oil. Journal of the American Oil Chemists' Society, 73, 1589–1593. Blasco, A., & Ouhayoun, J. (1996). Harmonization of criteria and terminology in rabbit meat research. Revised proposal. World Rabbit Science, 4, 93–99. Carraro, L., Trocino, A., & Xiccato, G. (2005). Dietary supplementation with olive stone meal in growing rabbits. Italian Journal of Animal Science, 4, 88–90. Cielab (1976). Colour system. Commission International de l'Eclairage (pp. 231).CIE Publication 36, Paris. Cyril, H. W., Castellini, C., & Dal Bosco, A. (1996). Comparison of three coking methods of rabbit meat. Italian Journal of Food Science, 8, 337–342. Dal Bosco, A., Castellini, C., Cardinali, R., Mourvaki, E., Moscati, L., Battistacci, L., et al. (2007). Olive cake dietary supplementation in rabbit: Immune and oxidative status. Italian Journal of Animal Science, 6, 761–763. Dal Bosco, A., Mugnai, C., Mourvaki, E., Cardinali, R., Moscati, L., Paci, G., et al. (2009). Effect of genotype and rearing system on the native immunity and oxidative status of growing rabbits. Italian Journal of Animal Science, 8, 781–783. De Blas, J. C., & Mateos, G. G. (1998). Feed formulation. In J. C. De Blas, & J. Wiseman (Eds.), The nutrition of the rabbit (pp. 241–253). Wallingford, U.K.: Commonwealth Agricultural Bureaux. EFSA-Q-2004-023 (2004). Opinion of the Scientific Panel on Animal Health and Welfare (AHAW) on a request from the Commission related to “The impact of the current housing and husbandry systems on the health and welfare of farmed domestic rabbits”. Adopte' le: 13/09/2005. Folch, J., Lees, M., & Sloanes-Stanley, H. (1957). A simple method for the isolation and purification of total lipids from animal tissues. Journal Biology Chemistry, 226, 497–509. Gidenne, T., Pinheiro, V., & Falcão, L. (2000). A comprehensive approach of the rabbit digestion: Consequences of a reduction in dietary fibre supply. Livestock Production Science, 64, 225–237.
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A. Dal Bosco et al. / Meat Science 92 (2012) 783–788
Gurr, M. I., Borlak, N., & Ganatra, S. (1989). Dietary fat and plasma lipids. Nutrition Research Reviews, 2, 63–86. Kadi, S. A., Belaidi-Gater, N., & Chebat, F. (2004). Inclusion of crude olive cake in growing rabbits diet: Effect on growth and slaughter yield. Proc. 8th World Rabbit Congress – September 7-10, 2004 – Puebla, Mexico. Karantonis, H. C., Tsantila, K., Stamatakis, G., Samiotaki, M., Panayotou, G., Smaragdi, K., et al. (2008). Bioactive polar lipids in olive oil, pomace and waste byproducts. Journal of Food Biochemistry, 32, 443–459. Kiritsakis, A. K. (1998). Flavor components of olive oil—A review. JAOCS, 75, 673–681. Korkeala, H., Mäki-Petais, O., Alanko, T., & Sorvettula, O. (1984). Determination of pH in meat. Meat Science, 18, 121–125. Maertens, L., Moermans, R., & De Groote, G. (1988). Prediction of the apparent digestible energy content of commercial pelleted feeds for rabbits. Journal of Applied Rabbit Research, 11, 60–67. Martin Garcia, A. I., Moumen, A., Yanez Ruiz, D. R., & Molina Alcaide, E. (2004). Chemical composition and nutrients availability for goats and sheep of two-stage olive cake and olive leaves. Animal Feed Science and Technology, 107, 61–74. Molina Alcaide, E., Yànez Ruìz, D. R., Moumen, A., & Martìn Garcìa, A. I. (2003). Chemical composition and nitrogen availability for goats and sheep of some olive by-products. Small Ruminant Research, 49, 329–336. Montedoro, G. F., Servili, M., Baldioli, M., & Miniati, E. (1992). Simple and hydrolysable phenolic compounds in virgin olive oil. 1. Their extraction, separation, quantitative and semi quantitative evaluation by HPLC. Journal of Agricultural and Food Chemistry, 40, 1571–1576. Nakamura, M., & Katoh, K. (1985). Influence of thawing method on several properties of rabbit meat. Bulletin of Ishikawa Prefecture College of Agriculture, 11, 45–49. Paci, G., Schiavone, A., & Marzonim, G. (2001). Influence d'un extrait végétal naturel (oléuropéine) sur les processus oxydatifs de la viande de lapin: premiers résultats. Mem. 9émes Journées Recherche Cunicole, Paris (pp. 27–30). Rupic, V., Bozikov, V., Bozac, R., Muzic, S., Vranesic, N., & Dikic, M. (1999). Effect of feeding olive by product on certain blood parameters and serum enzyme activities of fattening rabbits. Acta Veterinaria Hungarica, 47, 65–75. Saija, A., Trombetta, D., Tomaino, A., Lo Cascio, R., Trinci, P., Uccella, N., et al. (1998). In vitro evaluation of the antioxidant activity and biomembrane interaction of the plant
phenols oleuropein and hydroxy-tyrosol. International Journal of Pharmaceutics, 166, 123–133. Selvaggini, R., Servili, M., Urbani, S., Esposto, S., Taticchi, A., & Montedoro, G. F. (2006). Evaluation of phenolic compounds in virgin olive oil by direct injection in high-performance liquid chromatography with fluorometric detection. Journal of Agricultural and Food Chemistry, 54, 2832–2838. Servili, M., Baldioli, M., Mariotti, F., & Montedoro, G. F. (1999). Phenolic composition of olive fruit and virgin olive oil: Distribution in the constitutive parts of fruit and evolution during the oil mechanical extraction process. Acta Horticulturae, 474, 609–613. Servili, M., Baldioli, M., Selvaggini, R., Macchioni, A., & Montedoro, G. F. (1999). Phenolic compounds of olive fruit: One- and two-dimensional nuclear magnetic resonance characterization of nüzhenide and its distribution in the constitutive parts of fruit. Journal of Agricultural and Food Chemistry, 47, 12–18. Servili, M., Esposto, S., Veneziani, G., Urbani, S., Taticchi, A., Di Maio, I., et al. (2011). Improvement of bioactive phenol content in virgin olive oil with an olive-vegetation water concentrate produced by membrane treatment. Food Chemistry, 124, 1308–1315. Servili, M., Selvaggini, R., Esposto, S., Taticchi, A., Montedoro, G. F., & Morozzi, G. (2004). Health and sensory properties of virgin olive oil hydrophilic phenols: Agronomic and technological aspects of production that affect their occurrence in the oil. Journal of Chromatography. A, 1054, 113–127. StataCorp (2005). Stata statistical software: Release 9.0 college station. TX: StataCorp. Tsantila, N., Karantonis, H. C., Perrea, D. N., Theocharis, S. E., Iliopoulos, D. G., Antonopoulou, A., et al. (2007). Antithrombotic and antiatherosclerotic properties of olive oil and olive pomace polar extracts in rabbits. Mediators of Inflammation, 36204. http://dx.doi.org/10.1155/2007/36204 (Article ID). Ulbricht, T. L., & Southgate, D. A. T. (1991). Coronary heart disease: Seven dietary factors. The Lancet, 338, 985–992. Van Soest, P. J., Robertson, J. B., & Lewis, B. A. (1991). Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science, 74, 3583–3597.
Contents lists available at SciVerse ScienceDirect
Meat Science journal homepage: www.elsevier.com/locate/meatsci
Effect of dietary supplementation with olive pomaces on the performance and meat quality of growing rabbits A. Dal Bosco a,⁎, E. Mourvaki a, R. Cardinali a, M. Servili b, B. Sebastiani c, S. Ruggeri a, S. Mattioli a, A. Taticchi b, S. Esposto b, C. Castellini a a b c
Department of Applied Biology, Section of Animal Science, University of Perugia, Borgo XX Giugno 74, 06126 Perugia, Italy Department of Food Science and Economics, Section of Food Technology and Biotechnology, University of Perugia, Via San Costanzo, 06126 Perugia, Italy Department of Public Health, Section of Molecular Epidemiology and Environmental Hygiene, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
a r t i c l e
i n f o
Article history: Received 5 April 2012 Received in revised form 3 July 2012 Accepted 4 July 2012 Keywords: Meat quality Olive pomace Ortho-diphenols Polyphenols Productive performance Rabbit
a b s t r a c t The aim was to investigate the effects of three types (A, B and C) of stoned and dehydrated olive pomaces (OPs), differing in olive cultivar, on productive performance and meat quality of growing rabbits. The inclusion of OPs (5%) negatively affected the performance of rabbits as it reduced the feed intake, growth rate, carcass weight and dressing out percentage (P b 0.05). Compared with the control, the meat of OP rabbits had a greater amount of monounsaturated and a lower amount of polyunsaturated fatty acids (P b 0.05), independent of the type of OP used. Oxidative processes in the meat of OPA and OPB were higher (P b 0.05), whereas OPC showed the same levels as the control group. This was due to the higher total polyphenol concentration and to the concomitant lower peroxide value of OPC. These results recommend the use of OP in rabbit diet with caution, taking into account the quality of the by-product in terms of oxidative status. © 2012 Elsevier Ltd. All rights reserved.
1. Introduction The cultivation of the olive tree (Olea europaea L.) is widespread in the Mediterranean area, where olive oil is widely used as a food in many parts of the world. Following the industrial extraction of oil from olive fruits, great amounts of by-products are obtained. Olive pomace (OP) is a solid heterogeneous mixture of olive skin, pulp, woody endocarps and seeds. This waste material represents approximately 35% (w/w) of the processed olives, in relation to the olive cultivar and the extraction method used. Unprocessed OP still contains a small amount of olive oil and is generally characterized by a high content of crude fiber and sugars (mainly polysaccharides) and moderate values of crude protein and fatty acids, chiefly oleic (C18:1n−9) and other C2–C7 fatty acids (Karantonis et al., 2008). A variety of substances with proven antioxidant and radical scavenging activity, such as hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and their secoiridoid derivatives (dialdheydic form of decarboxymethyl elenolic acid, 3,4-DHPEA-EDA or p-HPEA-EDA) as well as verbascoside, is also contained in OP (Amro, Aburjai, & Al-Khalil, 2002; Servili, Baldioli, Mariotti, & Montedoro, 1999).
Abbreviations: FA, fatty acid; OP, olive pomace; TBARS, thiobarbituric acid reactive substances. ⁎ Corresponding author. Tel.: +39 0755857110; fax: +39 0755857122. E-mail address: [email protected] (A. Dal Bosco). 0309-1740/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2012.07.001
The amount of OP oil (approximately 8%) and water depends on the applied process and on the operating conditions (Kiritsakis, 1998). Moreover, the chemical composition of OPs may vary widely in relation to the agronomic and technological conditions of production. Additionally, the olive cultivar is one of the most important factors that affect the phenolic concentration of olive oil and by-products (Martin Garcia, Moumen, Yanez Ruiz, & Molina Alcaide, 2004; Servili et al., 2004; Servili et al., 2011). Based on the above characteristics, OPs have been proposed as alternative sources of nutrients for domestic animal feeding (www.fao.org). Among domestic ruminants, goats seem to be adapted for utilizing this high lignin-cellulose/low protein feedstuff (Molina Alcaide, Yànez Ruìz, Moumen, & Martìn Garcìa, 2003). The other ruminants require an adequate supply of protein nitrogen for the ruminal microorganisms and/or addition of specific de-activating tannin compounds (Al Jassim, Awadeh, & Abodabos, 1997; Martin Garcia et al., 2004; Molina Alcaide et al., 2003). Concerning monogastric animals such as rabbits, very little data are available (Dal Bosco et al., 2007; Rupic et al., 1999; Tsantila et al., 2007). In particular, Carraro, Trocino, and Xiccato (2005) investigated the possibility of including OPs in rabbit diets as a source of indigestible fiber in order to obtain a better equilibrium between the different fiber fractions and reducing the sanitary risk. Rupic et al. (1999) and Dal Bosco et al. (2007) investigated the effect of dietary OP inclusion on the in vivo parameters of fattening rabbits. Tsantila et al. (2007) reported that OPs contain specific antagonists of the platelet activating factor, with bioactivity similar to olive oil, which in turn has an effect in inhibiting atherosclerosis development in rabbits. These compounds
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could be useful in producing foods with higher nutritional value, as they are in olive oil industry by-products (Karantonis et al., 2008). The role of OP-derived bioactive polyphenols in rabbit meat quality and oxidative stability has never been investigated. Based on these considerations, the present investigation was undertaken to evaluate the effects of dietary supplementation with three types of stoned and dried OPs, derived from olive cultivars that yielded differences in the performance and meat quality of growing rabbits. 2. Materials and methods 2.1. Animals and diets All procedures were carried out under EU Regulations for experiments on living animals (EFSA, 2004). The study was carried out in the experimental rabbitry section of the Department of Applied Biology (University of Perugia) where one hundred and sixty weaned (30 d) New Zealand white rabbits were housed in bicellular cages located in the same air-conditioned room (temperature ranging from 15 to 20 °C and relative humidity from 65 to 70%). Rabbits were divided into four homogeneous groups and fed ad libitum isoenergetic and isoproteic diets: control diet and three diets where barley was replaced with 5% dried, stoned OP (i.e., A, B, and C). The control diet was formulated according to the current recommendations for growing rabbits (De Blas & Mateos, 1998). In detail, OPA was a pomace mixture of various olive cultivars (Coratina, Moraiolo, Frantoio and Ogliarola), whereas OPB and OPC were obtained from Frantoio and Coratina olive cultivars, respectively. With regard to the antioxidant content, the different OPs were characterized by low (OPA), medium (OPB) and high (OPC) phenolic concentrations. The dehydration of the stoned OPs was carried out in a pilot plant by a fluid bed dryer with an operative capacity of 50 kg/h. The inlet temperature of the air was 120 °C, whereas the mean temperature for drying was 45–50 °C. The formulation and chemical composition of the diets are reported in Table 1. Dry matter was determined by oven drying at 105 °C overnight (AOAC, cod. 930.15, 1995). Crude protein was measured by a Kjeldahl nitrogen analysis (AOAC cod. 954.01, 1995). Ash content was determined by combusting for 3 h at 550 °C. Neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) content were determined according to Van Soest, Robertson, and Lewis (1991). Lipids were extracted by diethyl ether using a Soxhlet apparatus. At 75 d, 20 rabbits per group, with weights close to the average of the group (± 10%), were selected and slaughtered, under veterinary supervision of the University of Perugia, in the departmental processing plant 12 h after feed withdrawal; the animals did not undergo transport. Specifically, the rabbits were killed by cutting their carotid arteries and jugular veins following electro-stunning and carcasses were prepared according to Blasco and Ouhayoun (1996). After carcass chilling (24 h at + 4 °C), the two longissimus lumborum muscles were removed and carefully freed from connective and adipose tissues. 2.2. Quality evaluation of olive cakes For the extraction of residual oil from the olive cakes, 250 mL of hexane was added to 100 g of the pomace. The mixture was homogenized with a T50 Ultraturrax for 1 min at 44 ×g for 10 min at 20 °C and then filtered with filter paper (Whatman no. 1). The extraction was performed in duplicate. The filtered homogenate was evaporated under vacuum in a nitrogen flow at 35 °C. The peroxide value, free acidity and fatty acid composition of the residual oil were measured in accordance with the European Official Methods (UE 1989/2003 modifying the ECC 2568/91).
Table 1 Formulation and chemical composition of control and of enriched diets with olive pomace A (mixed cultivars), B (Frantoio) or C (Coratina). Control diet
Diet A
Diet B
Diet C
30.00 10.00 18.00 25.00 12.00 – – – 1.35 1.20 1.00 0.70 0.70 0.05 89.00
30.00 10.00 18.00 20.00 12.00 5.00 – – 1.35 1.20 1.00 0.70 0.70 0.05 90.09
30.00 10.00 18.00 20.00 12.00 – 5.00 – 1.35 1.20 1.00 0.70 0.70 0.05 90.58
30.00 10.00 18.00 20.00 12.00 – – 5.00 1.35 1.20 1.00 0.70 0.70 0.05 90.20
Proximate composition (% fresh matter) Moisture 11.00 Crude protein 17.35 Ether extract 2.00 Ash 7.25 Fiber 12.88 NDF 24.07 ADF 14.13 ADL 2.90 Hemicellulose 9.94 Digestible energyb MJ/kg f.m. 10.55
9.91 17.84 2.18 6.85 13.10 25.49 15.65 3.22 9.75 10.78
9.42 17.77 2.55 7.25 12.95 26.00 14.94 3.02 10.06 10.60
9.80 17.70 2.60 6.99 13.00 24.84 15.15 2.95 10.91 10.75
Ingredients (% wet weight) Alfa–alfa hay Corn meal Soybean meal 48% Barley Wheat bran OPA OPB OPC Ca-phosphate Vitamin mineral premixa Molasses Salt Ca-carbonate DL-methionine Dry matter
a Added per kg: vit. A U.I. 11.000; vit. D3 U.I. 2.000; vit. B1 2.5 mg; vit. B2 4 mg; vit. B6 1.25 mg; vit. B12 0.01 mg; vit. E 25 mg; biotin 0.06 mg; vit. K 2.5 mg; niacin 15 mg; folic ac. 0.30 mg; D-pantothenic ac. 10 mg; choline 600 mg; Mn 60 mg; Cu 3 mg; Fe 50 mg; Zn 15 mg; I 0.5 mg; Co 0.5 mg; lysine 50 mg; methionine 40 mg. b Estimated according to Maertens, Moermans, and De Groote (1988).
The concentrations of total phenols and orthodiphenols for each OP and experimental diet were determined colorimetrically, according to Montedoro, Servili, Baldioli, and Miniati (1992). The phenolic compounds were extracted from the OPs by modifying the procedure previously described by Servili, Baldioli, Selvaggini, Macchioni, & Montedoro (1999). Ten grams of PO were homogenized with 100 mL of 80% methanol containing 20 mg/L of sodium diethyldithiocarbamate (DIECA); the extraction was performed in triplicate. After the removal of the methanol, the aqueous extract underwent SPE phenol separation. The SPE procedure was performed by loading 1 mL of the aqueous extract into a 5 g/25 mL Extraclean highload C18 cartridge (Alltech Italia S.r.l., Sedriano, Italy). Methanol (50 mL) was used as the eluting solvent. After removing the solvent under vacuum at 30 °C, the phenolic extract was recovered and then dissolved in methanol (1 mL). The reversed-phase HPLC analyses of the phenolic extracts were conducted with an Agilent Technologies system Mod. 1100 (Agilent Technologies Italia S.p.A., Cernusco sul Naviglio, Milano, Italy), which was composed of a vacuum degasser, a quaternary pump, an autosampler, a thermostatted column compartment, a Diode-Array Detector (DAD), and a fluorescence detector (FLD). To evaluate the phenolic compounds (Selvaggini et al., 2006), a Spherisorb column ODS-1 250 × 4.6 mm with a particle size of 5 μm (Phase Separation Ltd., Deeside, U.K.) maintained at 25 °C was employed, and a 20 μL sample volume was injected. The mobile phase was composed of 0.2% acetic acid (pH 3.1) in water (solvent A)/methanol (solvent B) at a flow rate of 1 mL/min. The gradient was changed as follows: 95% A/5% B for 2 min, 75% A/25% B in 8 min, 60% A/40% B in 10 min, 50% A/50% B in 16 min, and 0% A/100% B in 14 min. This composition was maintained for 10 min and was then returned to the initial conditions and equilibration in 13 min; the total running time was 73 min. Lignans were detected using the FLD operated at an excitation wavelength of 280 nm and emission at 339 nm
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(Selvaggini et al., 2006), whereas the other compounds were detected using the DAD with wavelength of 278 nm. 2.3. Determination of the lipid fatty acid profile of olive cakes and diets The fatty acid (FA) profile of OPs and diets was determined by gas-chromatography (Fisons Mega 2, equipped with a flame ionization detector; Fisons Instruments S.p.A., Rodano, Milano, Italy) after lipid extraction (Folch, Lees, & Sloanes-Stanley, 1957) and consecutive hot derivatization with a methanolic solution of sulfuric acid (3%). Separation of the resulting fatty acid methyl esters (FAME) was carried out on an Agilent (J&W) capillary column (30 m × 0.25 mm I.D.) coated with a DB-Wax stationary phase (film thickness of 0.25 mm). The individual FA methyl esters (FAME) were identified by reference to the retention time of authentic FAME standards. The relative proportion of each FA in the samples was expressed as a percentage of total FA and calculated with Chrom-Card software.
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Dietary indexes of atherogenicity (AI) and thrombogenicity (TI) were evaluated as proposed by Ulbricht and Southgate (1991), while the peroxidability index (PI) was determined according to Arakawa and Sagai (1986). The extent of muscle lipid peroxidation was evaluated by a spectrophotometer at 532 nm, (Hitachi U-2000, Theodor‐Heuss‐Anlage 12, Mannheim, F.R. Germany), which measured the absorbance of thiobarbituric acid-reactive substances (TBARS), and a tetraethoxypropane calibration curve in sodium acetate buffer (pH = 3.5, Dal Bosco et al., 2009). The results were expressed as malondialdehyde (MDA) mg/kg muscle. 2.5. Statistical analysis The data are presented as the least square means and least significant differences at 5%. The data were processed using the GLM procedure of Stata (StataCorp, 2005), based on a linear model that evaluates the fixed effect of dietary treatments.
2.4. Evaluation of rabbit meat quality parameters 3. Results Proximate analyses of longissimus lumborum muscles were carried out according to the Association of Official Analytical Chemists (AOAC, 1995). In particular, moisture, ash, and total nitrogen content were obtained using the N. 950.46B, 920.153, and 928.08 methods, respectively. The total protein content was calculated using Kjeldahl nitrogen and a conversion factor of 6.25. The total lipid content was extracted from 5 g of each homogenized sample and calculated gravimetrically (Folch et al., 1957). Ultimate pH (pHu) was measured at 24 h with a Knick digital pH meter (Broadly Corp., Santa Ana, CA, USA) after homogenization of 1 g of raw muscle for 30 s in 10 mL of 5 M iodoacetate (Korkeala, Mäki-Petais, Alanko, & Sorvettula, 1984). The water holding capacity (WHC) was estimated (Nakamura & Katoh, 1985) by centrifuging 1 g of whole muscle placed on tissue paper inside a tube for 4 min at 1500 ×g. The remaining water after centrifugation was quantified by drying the samples at 70 °C overnight. The WHC was calculated as follows: (weight after centrifugation −weight after drying) /initial weight× 100. Whole samples of both muscles (approximately 20 g) were placed in open aluminum pans and roasted in an electric oven (pre-heated to 200 °C) for 15 min to an internal temperature of 80 °C (Cyril, Castellini, & Dal Bosco, 1996). Cooking loss was estimated as the percentage of the weight of the roasted samples (cooled for 30 min to approximately 15 °C and dried on the surface with a paper towel) with respect to the raw samples. Shear force was evaluated on the cores (1.25 cm × 2 cm) obtained from the mid-portions of the roasted samples (as above) by cutting them perpendicularly to the direction of the fiber using an Instron Model 1011 equipped with a Warner-Blatzler Meat Shear Apparatus (Instron, Test and Measurement, Trezzano sul Naviglio, Milano, Italy). The color parameters (L*, a*, b*) for the raw muscles were measured using a tristimulus analyzer (Minolta Chroma Meter CR-200, Azuchi-Machi Higashi-Ku, Osaka 541, Japan) with the Cielab (1976). The L*a*b* color system consists of a luminance or lightness component (L*) and two chromatic components: the a° component from green (− a) to red (+a) and the b* component from blue (− b) to yellow (+b) colors. The colorimeter was calibrated using a standard pink plate. It has an 8 mm diameter measuring area and uses diffuse illumination and 0° viewing angle (spectral component included) for accurate measurement of a wide variety of subjects. The fatty acid profile was determined by gas-chromatography using the procedures previously described for OPs and diets. The average amount of each fatty acid was used to calculate the sum of the saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids.
3.1. Effects of the olive cultivar on the biochemical characteristics of OPs The main biochemical characteristics of the three types of OPs are reported in Table 2. Olive cake C had the highest total polyphenol concentration, followed by OPB, whereas OPA had almost half the quantity of OPC. The most abundant phenols were 3,4-DHPEA-EDA and verbascoside. OPs B and C were also very rich in p-HPEA-EDA. A reverse order was observed for the peroxide number and free acidity (OPA > OPB > OPC). As a consequence, the concentration ratio between peroxide number and ortho-diphenols was higher in OPC than in the other two OPs, suggesting a higher oxidative stability. Gas-chromatography analysis of OP lipids revealed that oleic acid was the predominant FA in all of the OPs, with the highest concentration found in OPC, followed by OPB. As a result, OPC had a 2-fold lower saturated/unsaturated ratio compared to OPA and OPB. Of all the OPs, the proportion of the PUFA n − 6 series was higher than in the PUFA n −3 series. Table 2 Polyphenol profile (g/kg dry weight) and other quality parameters of the olive pomace A (mixed olive cultivars), B (Frantoio) and C (Coratina). Determined by HPLCa
3,4-DHPEA p-DHPEA Verbascoside 3,4-DHPEA-EDA p-HPEA-EDA (+)-1-Acetoxypinoresinol Lutein Ortho-diphenols Free acidity (g of oleic acid/100 g of oil) Peroxide number (meq O2/kg oil) Peroxide/ortho-diphenols Fatty acid composition (% of total) C16:0 C18:0 C18:1n−9 C18:2n−6 C18:3n−3 Total SFA Total MUFA Total PUFA Saturated/unsaturated FAb PUFA (n−3/n−6)
Olive pomace A
B
C
1.3 ± 0.01 0.7 ± 0.01 9.7 ± 0.1 8.3 ± 0.6 1.1 ± 0.01 0.6 ± 0.01 n.d. 4.1 ± 0.4 6.1 ± 0.4 21.4 ± 1.3 5.2 ± 0.6
1.5 ± 0.01 1.0 ± 0.01 9.9 ± 1.0 17.0 ± 1.7 6.9 ± 0.7 0.6 ± 0.1 0.8 ± 0.1 8.0 ± 0.8 4.0 ± 0.2 15.3 ± 0.9 1.9 ± 0.2
1.1 ± 0.01 1.4 ± 0.01 11.8 ± 0.1 22.0 ± 1.2 10.1 ± 0.1 1.1 ± 0.01 1.2 ± 0.01 9.9 ± 1.0 3.4 ± 0.1 9.8 ± 0.5 1.1 ± 0.1
13.8 ± 0.3 2.2 ± 0.1 69.4 ± 1.8 9.5 ± 0.3 1.0 ± 0.1 16.1 ± 0.2 69.4 ± 1.7 10.5 ± 0.4 0.2 ± 0.1 0.1 ± 0.1
13.0 ± 0.2 2.6 ± 0.1 74.0 ± 1.6 7.6 ± 0.2 1.1 ± 0.2 15.6 ± 0.4 74.0 ± 1.6 8.7 ± 0.2 0.2 ± 0.1 0.2 ± 0.1
11.8 ± 0.3 2.6 ± 0.1 76.3 ± 1.8 7.7 ± 0.4 0.9 ± 0.1 14.4 ± 0.2 76.3 ± 1.7 8.7 ± 0.4 0.1 ± 0.1 0.1 ± 0.1
Each value represents the mean of three replicate analyses. a The phenolic content is reported as the mean value of four independent samplings. b Unsaturated FA is defined as the sum of MUFA and PUFA.
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3.2. Effects of OP inclusion on the chemical and biochemical composition of diets Inclusion of OP in the standard diet resulted in a slight increase in ether extract, independent of the type of OC used, without affecting the energy content of the diets (Table 1). Regarding the FA pattern of the ether extract, OP-enriched diets had a higher proportion of MUFA and a concomitant lower proportion of PUFA compared to the control diet (Table 3). The resulting saturated/unsaturated FA ratio of the diets was affected by these changes, and the OP diets showed lower values with respect to the control diet. Oleic acid was the predominant FA of OP-enriched diets, while linoleic acid was the most representative FA in the control diet. The OPC diet had the highest level of oleic acid.
Control
Group A
Group B
Group C
Mortality (%) 10 13 15 10 Weaning weight 561 558 554 560 (g) 2,510a 2,450a 2,590b Slaughter weight 2,640c (g) 43.4a 42.1a 45.1b Daily weight gain 46.2c (g) 128.0a 126.4a 135.3b Daily feed intake 143.9c (g) Feed conversion (g) 3.1 2.9 3.0 3.0 Carcass weight (g) 1,610b 1,500a 1445a 1,595b b ab a Dressing out (%) 61 60 59 59a
P value SED – 0.657
3⁎ 49
0.042
47
0.002
3.1
0.047
11.5
0.523 0.041 0.036
0.09 105 1.3
N = 20 per group; a,b,c: Least square means in the same row with different superscript letters are significantly different (P b 0.05); SED: standard error deviation. ⁎ χ2, P b 0.05.
3.3. Influence of olive pomace on the productivity of rabbits The inclusion of OPs reduced the feed intake of the diets from 5% (OPC) to 16% (OPA–OPB). Accordingly, rabbits fed the OPA and OPB diets had a lower daily weight gain and lower slaughter and carcass weights (P b 0.05) with respect to the control and OPC-treated rabbits (Table 4).
3.4. Effects of OC dietary supplementation on meat quality The proximate composition and physical traits of longissimus lumborum muscle were not affected by OP (Table 5). On the contrary, the fatty acid profiles, dietary indexes and oxidative status of meat underwent several modifications in relation to the OP used (Table 6). In detail, dietary treatment with OP resulted in a significant (P b 0.05) increase of MUFA, to the detriment of PUFA (P b 0.05), in meat. The proportion of SFA was reduced, reaching statistical significance (P b 0.05) only for the meat of the OPC-treated rabbits. This group had the greatest proportion of MUFA (chiefly oleic acid) but the lowest proportion of PUFA (especially linoleic acid). As a consequence, the ratio between saturated and unsaturated FAs was also lower. The changes in meat fatty acids due to OP were responsible for the changes in the dietary quality indexes. Accordingly, the peroxidability index was lower (P b 0.05) in all meat samples that were derived from OP-treated rabbits, whereas the atherogenic and thrombogenic indexes were significantly (P b 0.05) reduced only in OPC. The oxidative stability of the meat lipid was also affected by OP supplementation, and the magnitude was related to the OP used. Meat from the OPB group had the greatest (P b 0.05) TBARS level and was therefore the most susceptible to lipid peroxidation with respect to the other groups. Table 3 Fatty acid composition of control and olive pomace-enriched diets (A — mixed cultivars; B — Frantoio and C — Coratina). Fatty acids (% of total)
Control
Diet A
Diet B
Diet C
C14:0 C16:0 C18:0 C18:1n−9 C18:2n−6 C18:3n−3 Total SFA Total MUFA Total PUFA Saturated/unsaturated FAa PUFA (n−3/n−6)
1.2 ± 0.1 19.5 ± 1.4 3.1 ± 1.1 16.9 ± 1.4 41.5 ± 2.3 14.7 ± 1.2 24.3 ± 1.1 18.8 ± 1.8 56.9 ± 2.8 1.2 ± 0.8 0.3 ± 0.1
0.8 ± 0.07 17.8 ± 1.0 2.9 ± 1.1 35.7 ± 2.2 29.7 ± 1.1 11.5 ± 1.8 20.4 ± 2.7 37.0 ± 2.4 42.7 ± 2.8 0.8 ± 0.08 0.4 ± 0.04
0.76 ± 0.01 17.0 ± 1.8 2.8 ± 1.9 43.7 ± 2.5 26.3 ± 1.3 8.0 ± 0.8 20.0 ± 1.8 44.8 ± 2.5 35.2 ± 2.2 0.7 ± 0.2 0.3 ± 0.1
0.6 ± 0.33 16.6 ± 1.5 2.6 ± 1.2 47.0 ± 2.8 26.8 ± 2.0 8.8 ± 1.1 19.0 ± 2.4 46.6 ± 2.8 34.4 ± 2.7 0.6 ± 0.08 0.3 ± 0.15
Each value represents the mean of three replicate analyses. a Unsaturated FA is defined as the sum of MUFA and PUFA.
Table 4 Productive performance of rabbits as affected by the inclusion of different types of olive pomace (A, B and C) in the standard diet.
4. Discussion There are many factors that affect the quality of OPs; olive cultivar, fruit quality, technological process and storage are the most important (Servili, Baldioli, Mariotti, et al., 1999). The OPs tested in this trial were obtained by a three-phase olive oil extraction from various Italian olive cultivars using stoned olives after oil separation and were characterized by different phenolic contents. Coratina is known to be the richest olive cultivar in terms of polyphenols, and this may explain the abundance of these compounds in the derivation of OP with respect to Frantoio, which is obtained under the same industrial conditions. The differences in polyphenol content among the OPs might be due to the observed differences in rancidity, defined as the peroxide value. Indeed, the degree of Frantoio OP autoxidation was higher than that of Coratina, although they both had the same proportion of unsaturated FAs. Based on the ratio between the peroxide value and the polyphenols, the studied OPs could be classified as high (Coratina), medium (Frantoio) or low quality (mixture). It should be noted that this parameter refers to the antioxidant properties of OP, giving limited information on the nutritional value of the OP. In this study, the FA composition of the OP lipids was also evaluated, which revealed substantial differences in oleic acid concentration among the different OPs (Coratina > Frantoio > mixture). The data demonstrated for the first time that meat quality can be seriously affected by the quality of the OP used in rabbit diet. The rabbits that were fed a diet containing OPC had the highest oxidative stability and nutritional value, as revealed by the low concentration of lipid peroxidation and the high nutritional indexes, respectively. It
Table 5 Proximate composition and physical traits of meat samples from rabbits fed a control or enriched diet with olive pomace A (mixed cultivar), B (Frantoio) and C (Coratina). Variable
Control
Proximate composition (g/100 g) Moisture 75.02 Protein 21.35 Lipids 2.19 Ash 1.44 Physical traits pHu 5.50 WHC (%) 55.08 Cooking loss (%) 34.69 Tenderness (kg/cm2) 2.78 Color L* 63.71 a* 6.90 b* 0.39
Group A
Group B
Group C
P value
SED
75.1 20.91 2.64 1.35
74.99 20.93 2.72 1.36
75.24 20.62 2.59 1.55
0.358 0.098 0.261 0.075
2.26 1.21 0.49 0.30
5.56 55.29 34.68 2.25
5.40 54.19 35.06 2.42
5.58 55.36 34.56 2.61
0.326 0.084 0.694 0.320
0.37 2.24 1.72 0.49
62.06 5.18 0.49
61.91 5.18 0.60
62.43 5.12 0.61
0.362 0.095 0.071
2.08 2.18 0.24
N = 20 per group; SED: standard error deviation.
A. Dal Bosco et al. / Meat Science 92 (2012) 783–788 Table 6 Fatty acid composition (% of total fatty acids), dietary indexes and oxidative status of rabbit meat fed with control diet, olive pomace A (mixed cultivar), B (Frantoio) and C (Coratina). Variable C14:0 C16:0 C18:0 Others Total SFA C14:1n−6 C16:1n−7 C18:1n−9 Others Total MUFA C18:2n−6 C20:3n−6 C20:4n−6 C18:3n−3 C20:3n−3 C20:5n−3 C21:5n−3 C22:5n−3 C22:6n−3 Others Total PUFA Saturated/unsaturated PUFA (n−3/n−6)
Control b
2.58 28.15 8.16b 2.15 41.04b 0.26 3.52b 23.78a 0.76 28.32a 20.13b 0.39 3.81 2.74 0.11 0.46 0.25 0.78b 0.53 1.42 30.64b 0.70b 0.20
A
B a
3.15 29.01 6.54ab 2.57 41.27b 0.23 2.98ab 26.67b 0.87 30.75b 17.57a 0.37 4.12 2.39 0.05 0.38 0.34 0.69b 0.48 1.60 27.98a 0.70b 0.19
Dietary indexes and oxidative status Atherogenicity index 0.67b 0.74c Thrombogenicity index 0.95b 0.98b Peroxidability index 59.24b 55.74a TBARs (μmol/L) 0.80a 1.20ab
C b
a
P value
SED
2.73 27.24 7.38ab 2.30 39.66b 0.19 2.45a 28.15c 1.25 32.04c 18.62ab 0.44 3.91 2.31 0.09 0.30 0.37 0.59a 0.36 1.27 28.30a 0.66b 0.17
2.31 27.60 5.03a 2.15 37.09a 0.24 2.41a 32.56d 1.31 36.52d 16.84a 0.32 3.53 2.29 0.06 0.42 0.39 0.61ab 0.57 1.38 26.39a 0.59a 0.21
0.002 0.154 0.021 0.240 0.035 0.068 0.046 0.003 0.063 0.001 0.027 0.258 0.094 0.247 0.095 0.107 0.087 0.048 0.301 0.074 0.006 0.024 0.061
0.21 2.22 1.22 0.13 1.12 0.18 0.40 2.05 0.34 1.41 1.20 0.16 1.29 0.80 0.06 0.14 0.12 0.12 0.16 0.30 2.42 0.06 0.06
0.65b 0.94b 53.84a 1.45b
0.60a 0.84a 53.07a 0.77a
0.003 0.039 0.041 0.007
0.04 0.09 3.02 0.19
N = 20 per group; a,b,c,d: Least square means in the same row with different superscript letters are significantly different (P b 0.05); SED: standard error deviation.
is likely that the high polyphenol content of OPC prevented the oxidation of unsaturated lipids, contributing to the preservation of the dietetic-nutritional value of the meat. Among the polar phenolic compounds, ortho-diphenols such as hydroxytyrosol 3,4-DHPEA-EDA and verbascoside have the best antioxidant activity and are good radical scavengers (Badioli, Servili, Perretti, & Montedoro, 1996). In particular, it has been demonstrated that hydroxytyrosol may scavenge aqueous peroxyl radicals near the membrane surface, while oleuropein may block/inhibit the chain propagating lipid peroxyl radicals within membranes (Saija et al., 1998). A great amount of hydroxytyrosol (in the form of 3,4-DHPEA-EDA) and verbascoside was contained in OPC, which supports this hypothesis, while the other OPs had a lower proportion. The beneficial effects of olive polyphenols on the oxidative status of meat have also been reported by Paci, Schiavone, and Marzonim (2001), who used oleuropein, an immediate precursor of hydroxytyrosol, further corroborating the present findings. The high dietetic indexes in the meat of OPC-treated rabbits should probably be ascribed to the higher oleic acid content and to the concomitant lower SFA concentration found in this type of olive oil waste. This is an important issue as monounsaturated acids, including oleic acid, have been shown to reduce plasma total cholesterol and low-density lipoprotein cholesterol, and their consumption is highly recommended to prevent cardiovascular diseases (Gurr, Borlak, & Ganatra, 1989). Although OP intake, especially Coratina, improved meat quality, the productive performance of the rabbits was slightly reduced. It should be noted that all the OP-enriched diets provided similar digestible energy to the rabbits. Nevertheless, the former diets had a slightly higher ether extract, NDF and hemicellulose levels, which may explain this phenomenon. It is well-known that high dietary hemicellulose decreases voluntary feed intake and, hence, rabbit
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weight (Gidenne, Pinheiro, & Falcão, 2000). In addition, OPs generally have low palatability and may contain anti-nutritional compounds that are able to complex proteins and sugars, limiting their nutrient availability. Carraro et al. (2005) reported that daily weight gain and final live weight were not affected by the inclusion of 3 and 6% of olive stone meal, but at the same time observed a decrease of daily feed intake as a consequence of OP supplementation. In another study aimed to evaluate the dietary effect of OP inclusion (20%) in an Algerian population of rabbits, Kadi, Belaidi-Gater, and Chebat (2004) concluded that crude olive cake seems to replace the alfalfa-like source of fiber and does not seem to influence the performance or carcass characteristics of growing rabbits. It is therefore clear that future studies are warranted to better clarify the abovementioned aspects, specifically to determine the types and concentrations of tannins or other anti-nutritional compounds contained in OPs. 5. Conclusions In conclusion, the data showed for the first time that the nutritional quality of rabbit meat can be improved by adding a 5% concentration of OP to the standard diet. To achieve this goal, only OPs of high quality in terms of pro-oxidant/antioxidant content should be used. Specifically, OPs with a peroxide value less than 10 meq/kg and an ortho-diphenol concentration higher than 20 g/kg can guarantee a satisfactory meat oxidative stability. Lastly, the findings support the notion that feeding rabbits with OPs could be an alternative strategy to enrich meat in precious monounsaturated FAs, such as oleic acid, which has recognized beneficial effects on human health. Other investigations are needed in order to improve the feed formulation and consequently rabbit performance that was slightly worsened by OP supplementation. References Al Jassim, R. A. M., Awadeh, F. D., & Abodabos, A. (1997). Supplementary feeding value of urea-treated olive cake when fed to growing Awassi lambs. Animal Feed Science and Technology, 64, 287–292. Amro, B., Aburjai, T., & Al-Khalil, S. (2002). Antioxidative and radical scavenging effects of olive cake extract. Fitoterapia, 73, 456–461. AOAC (1995). Official methods of analysis (15th ed.). Washington, DC, USA: Association of Official Analytical Chemist. Arakawa, K., & Sagai, M. (1986). Species difference in lipid peroxide levels in lung tissue and investigation of their determining factors. Lipids, 21, 769–778. Badioli, M., Servili, M., Perretti, G., & Montedoro, G. F. (1996). Antioxidant activity of tocopherols and phenolic compounds in virgin olive oil. Journal of the American Oil Chemists' Society, 73, 1589–1593. Blasco, A., & Ouhayoun, J. (1996). Harmonization of criteria and terminology in rabbit meat research. Revised proposal. World Rabbit Science, 4, 93–99. Carraro, L., Trocino, A., & Xiccato, G. (2005). Dietary supplementation with olive stone meal in growing rabbits. Italian Journal of Animal Science, 4, 88–90. Cielab (1976). Colour system. Commission International de l'Eclairage (pp. 231).CIE Publication 36, Paris. Cyril, H. W., Castellini, C., & Dal Bosco, A. (1996). Comparison of three coking methods of rabbit meat. Italian Journal of Food Science, 8, 337–342. Dal Bosco, A., Castellini, C., Cardinali, R., Mourvaki, E., Moscati, L., Battistacci, L., et al. (2007). Olive cake dietary supplementation in rabbit: Immune and oxidative status. Italian Journal of Animal Science, 6, 761–763. Dal Bosco, A., Mugnai, C., Mourvaki, E., Cardinali, R., Moscati, L., Paci, G., et al. (2009). Effect of genotype and rearing system on the native immunity and oxidative status of growing rabbits. Italian Journal of Animal Science, 8, 781–783. De Blas, J. C., & Mateos, G. G. (1998). Feed formulation. In J. C. De Blas, & J. Wiseman (Eds.), The nutrition of the rabbit (pp. 241–253). Wallingford, U.K.: Commonwealth Agricultural Bureaux. EFSA-Q-2004-023 (2004). Opinion of the Scientific Panel on Animal Health and Welfare (AHAW) on a request from the Commission related to “The impact of the current housing and husbandry systems on the health and welfare of farmed domestic rabbits”. Adopte' le: 13/09/2005. Folch, J., Lees, M., & Sloanes-Stanley, H. (1957). A simple method for the isolation and purification of total lipids from animal tissues. Journal Biology Chemistry, 226, 497–509. Gidenne, T., Pinheiro, V., & Falcão, L. (2000). A comprehensive approach of the rabbit digestion: Consequences of a reduction in dietary fibre supply. Livestock Production Science, 64, 225–237.
788
A. Dal Bosco et al. / Meat Science 92 (2012) 783–788
Gurr, M. I., Borlak, N., & Ganatra, S. (1989). Dietary fat and plasma lipids. Nutrition Research Reviews, 2, 63–86. Kadi, S. A., Belaidi-Gater, N., & Chebat, F. (2004). Inclusion of crude olive cake in growing rabbits diet: Effect on growth and slaughter yield. Proc. 8th World Rabbit Congress – September 7-10, 2004 – Puebla, Mexico. Karantonis, H. C., Tsantila, K., Stamatakis, G., Samiotaki, M., Panayotou, G., Smaragdi, K., et al. (2008). Bioactive polar lipids in olive oil, pomace and waste byproducts. Journal of Food Biochemistry, 32, 443–459. Kiritsakis, A. K. (1998). Flavor components of olive oil—A review. JAOCS, 75, 673–681. Korkeala, H., Mäki-Petais, O., Alanko, T., & Sorvettula, O. (1984). Determination of pH in meat. Meat Science, 18, 121–125. Maertens, L., Moermans, R., & De Groote, G. (1988). Prediction of the apparent digestible energy content of commercial pelleted feeds for rabbits. Journal of Applied Rabbit Research, 11, 60–67. Martin Garcia, A. I., Moumen, A., Yanez Ruiz, D. R., & Molina Alcaide, E. (2004). Chemical composition and nutrients availability for goats and sheep of two-stage olive cake and olive leaves. Animal Feed Science and Technology, 107, 61–74. Molina Alcaide, E., Yànez Ruìz, D. R., Moumen, A., & Martìn Garcìa, A. I. (2003). Chemical composition and nitrogen availability for goats and sheep of some olive by-products. Small Ruminant Research, 49, 329–336. Montedoro, G. F., Servili, M., Baldioli, M., & Miniati, E. (1992). Simple and hydrolysable phenolic compounds in virgin olive oil. 1. Their extraction, separation, quantitative and semi quantitative evaluation by HPLC. Journal of Agricultural and Food Chemistry, 40, 1571–1576. Nakamura, M., & Katoh, K. (1985). Influence of thawing method on several properties of rabbit meat. Bulletin of Ishikawa Prefecture College of Agriculture, 11, 45–49. Paci, G., Schiavone, A., & Marzonim, G. (2001). Influence d'un extrait végétal naturel (oléuropéine) sur les processus oxydatifs de la viande de lapin: premiers résultats. Mem. 9émes Journées Recherche Cunicole, Paris (pp. 27–30). Rupic, V., Bozikov, V., Bozac, R., Muzic, S., Vranesic, N., & Dikic, M. (1999). Effect of feeding olive by product on certain blood parameters and serum enzyme activities of fattening rabbits. Acta Veterinaria Hungarica, 47, 65–75. Saija, A., Trombetta, D., Tomaino, A., Lo Cascio, R., Trinci, P., Uccella, N., et al. (1998). In vitro evaluation of the antioxidant activity and biomembrane interaction of the plant
phenols oleuropein and hydroxy-tyrosol. International Journal of Pharmaceutics, 166, 123–133. Selvaggini, R., Servili, M., Urbani, S., Esposto, S., Taticchi, A., & Montedoro, G. F. (2006). Evaluation of phenolic compounds in virgin olive oil by direct injection in high-performance liquid chromatography with fluorometric detection. Journal of Agricultural and Food Chemistry, 54, 2832–2838. Servili, M., Baldioli, M., Mariotti, F., & Montedoro, G. F. (1999). Phenolic composition of olive fruit and virgin olive oil: Distribution in the constitutive parts of fruit and evolution during the oil mechanical extraction process. Acta Horticulturae, 474, 609–613. Servili, M., Baldioli, M., Selvaggini, R., Macchioni, A., & Montedoro, G. F. (1999). Phenolic compounds of olive fruit: One- and two-dimensional nuclear magnetic resonance characterization of nüzhenide and its distribution in the constitutive parts of fruit. Journal of Agricultural and Food Chemistry, 47, 12–18. Servili, M., Esposto, S., Veneziani, G., Urbani, S., Taticchi, A., Di Maio, I., et al. (2011). Improvement of bioactive phenol content in virgin olive oil with an olive-vegetation water concentrate produced by membrane treatment. Food Chemistry, 124, 1308–1315. Servili, M., Selvaggini, R., Esposto, S., Taticchi, A., Montedoro, G. F., & Morozzi, G. (2004). Health and sensory properties of virgin olive oil hydrophilic phenols: Agronomic and technological aspects of production that affect their occurrence in the oil. Journal of Chromatography. A, 1054, 113–127. StataCorp (2005). Stata statistical software: Release 9.0 college station. TX: StataCorp. Tsantila, N., Karantonis, H. C., Perrea, D. N., Theocharis, S. E., Iliopoulos, D. G., Antonopoulou, A., et al. (2007). Antithrombotic and antiatherosclerotic properties of olive oil and olive pomace polar extracts in rabbits. Mediators of Inflammation, 36204. http://dx.doi.org/10.1155/2007/36204 (Article ID). Ulbricht, T. L., & Southgate, D. A. T. (1991). Coronary heart disease: Seven dietary factors. The Lancet, 338, 985–992. Van Soest, P. J., Robertson, J. B., & Lewis, B. A. (1991). Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science, 74, 3583–3597.