Livestock Research for Rural Development 29 (10) 2017 Guide for preparation of papers LRRD Newsletter

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Comparison of the nutritive value and fatty acid profile of the green pruning residues of six grapevine (Vitis vinifera L.) cultivars

P G Peiretti, G Masoero1 and S Tassone2

Institute of Sciences of Food Production, National Research Council, Grugliasco, Italy
1 Academy of Agriculture of Torino, Torino, Italy
2 Department of Agriculture, Forestry and Food Sciences, University of Torino, Grugliasco, Italy


Interest in the green pruning residues of grapevine (GPR), harvested in spring, as a feedstuff has been increasing due to its nutritive value. The aim of this study was to investigate the differences between six cultivars of red Vitis vinifera (Nebbiolo, Barbera, Syrah, Grenache, Pinot Noir and Cabernet Sauvignon) as far as the chemical composition, gross energy, in vitro apparent digestibility (DMD) and fatty acid (FA) profile of their GPR are concerned.

There are not significant differences among cultivars in terms of dry matter (DM), crude protein and lipid contents. Whereas there are significant differences among cultivars in terms of ash, neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin contents ranged from 54 to 70, 495 to 542, 375 to 425, and 91 to 142 g/kg DM, respectively. Moreover, the cell wall contents (NDF, ADF and lignin) of the GPR were negatively correlated to the DMD, which ranged from 449 to 544 g/kg DM. The FA profile of the GPR was characterized by a low content of saturated FAs and a high content of polyunsaturated FAs (PUFA); among the latter, α-linolenic acid and linoleic acid ranged from 356 to 419 and 228 to 312 g/kg of the total FAs, respectively. Linoleic acid was found to differ significantly for the six cultivars, and the highest value was found in the GPR of the Pinot Noir.

Thus, GPR may have a good potential nutritive value and an interesting PUFA content for small ruminants.

Key words: by-product, chemical composition, digestibility, fibrous content, ruminant


Several wine production by-products have been studied as sources of natural bioactive compounds. They have been found to be potentially safe and have therefore been proposed as health promoters (Teixeira et al 2014). Moure et al (2001) reported that certain by-products of grape processing, such as seeds and peels, are promising sources of natural antioxidants. The rich and varied chemical composition of these by-products has led to a considerable interest in grape pomace as a promising source of compounds that show good nutritional properties for ruminants (Abarghuei et al 2010; Bahrami et al 2010; Basalan et al 2011; Baumgärtel et al 2007; Besharati and Taghizadeh 2009; Bravo and Saura-Calixto 1998; Deng et al 2011; Pirmohammadi et al 2007a; Romero et al 2000; Spanghero et al 2009; Zalikarenab et al 2007). Other studies have assessed the effects of ensiling on the nutrient utilization of grape pomace in ruminants (Alipour and Rouzbehan 2007; Pirmohammadi et al 2007b; Rebolé and Alvira 1986; Rebolé et al 1988; Santos et al 2014; Winkler et al 2015).

Grapevine (Vitis vinifera L.) pruning is the most important operation that growers perform on the plants during spring, and it generates an abundant residue, which is usually left in the fields. Viticulture produces large quantities of these green residues, which represent a management issue from an economic point of view, but which could constitute a source of alternative feedstuff for ruminants, and in particular for sheep. Gurbuz (2007) determined the potential value of the leaves of four Turkish grapevine cultivars (Ak, Kabarcık, Kıbrıs and Mahrabası), considering their chemical composition, in situ DM and crude protein (CP) degradation, and in vitro gas production. Kok et al (2007) studied the forage and nutritive values of grapevine leaves plus the summer lateral shoots of four cultivars (Cabernet Sauvignon, Merlot, Sauvignon Blanc and Sémillon) at grape harvest and at two post-harvest dates.

However, very little information is available in literature about the fatty acid (FA) content of grapevine by-products (Hussein and Abdrabba 2015). Grape seeds are also a source of healthy FAs and dietary fibre, according to Cao and Ito (2003).

The aim of this study was to investigate the differences in the chemical composition, gross energy, in vitro apparent digestibility (DMD) and FA profile of the green pruning residues of grapevine (GPR) taken from six cultivars of red Vitis vinifera.

Materials and methods

Plant material and environmental conditions

The trials were carried out in the western Po Valley (Italy) in June 2016. The GPR of six cultivars of red Vitis vinifera (Nebbiolo, Barbera, Syrah, Grenache, Pinot Noir and Cabernet Sauvignon) were cut for each cultivar, with edging shears, on three plots randomly located in an experimental field at an altitude of 290 m above sea level (45°06′50″N 7°59′13″E). Sampling was only conducted in favorable weather conditions and after the disappearance of dew.

Chemical analysis

An aliquot of 200 g of each collected GPR sample was used to determine the DM, in duplicate, in a forced draft air oven at 105 °C overnight. Another aliquot of 200 g was immediately refrigerated, freeze-dried, and then brought to air temperature, ground in a Cyclotec mill (Tecator, Herndon, VA, USA) to pass through a 1-mm screen, and then stored for other analyses using the methods of the Association of Official Analysis Chemists (1990) for CP (AOAC method 955.04) and ash (AOAC method 942.05). Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin were determined using an Ankom 200 Fibre Analyser (Ankom Technology Corp., Macedon, NY, USA), according to the Van Soest et al (1991) method. The NDF of the samples was analyzed without sodium sulfite or α–amylase. Gross energy (GE) was determined using an adiabatic calorimeter bomb (IKA C7000, Staufen, Germany), according to Meineri and Peiretti (2005). The lipid content was quantified according to Peiretti et al (2013). All the analyses were performed in duplicate.

In vitro digestibility

The GPR samples were also analyzed to determine their DMD, using a Daisy II Incubator (Ankom Technology Corp., Fairport, NY, USA), according to Robinson et al (1999). Freeze-dried samples (0.25 ± 0.01 g) were double-weighed in F57 Ankom bags, with a pore size of 25 µm, heat-sealed and then placed into an incubation jar. Each jar was a glass recipient with a plastic lid provided with a single-way valve, which prevented the accumulation of fermentation gases, and was filled with 2 l buffered rumen fluid, in an anaerobic condition. The jar was then introduced into the incubator. The rumen liquor was collected, at a slaughterhouse, from the rumen content of cattle fed a fibre-rich diet (Spanghero et al 2010). The heat (39°C) and agitation were maintained constant and uniform in the controlled chamber by means of continuous rotation. After 48 h of incubation, the jars were emptied and the bags were rinsed gently. DMD was calculated using the following equation:

DMD (g/kg DM)= DMwtante- DMwtpost/ DMwt ante * 1000

where DMwtante is the DM weight before the incubation and DMwt post is the DM weight after the incubation.

Fatty acid analysis

FA analysis was performed on freeze-dried GPR (2 g), according to the method described by Peiretti et al (2013). The FA methyl esters in hexane were injected into a gas chromatograph (GC 1000 DPC; Dani Instruments S.p.A., Cologno Monzese, Italy), equipped with a flame ionisation detector, a programmed temperature vaporizing injection port and a Supelcowax-10 fused silica column (60 m × 0.32 mm, 0.25 μm). The peak area was measured using a Dani DDS 1000 Data Station. Each peak was identified according to pure methyl ester standards (Supelco and Restek Corporation, Bellefonte, PA), and the data were expressed as relative values. The FA content was expressed as g/kg of total FAs.

Statistical analysis

The variability in the chemical composition, the digestibility and the FA profile of the samples were analyzed, to establish their statistical significance, by means of an analysis of variance (ANOVA), using SPSS version 11.5.1 for Windows (SPSS Inc., Chicago, IL, USA) to test the effect of the cultivars. Multiple comparisons of the means were conducted using a Post Hoc (Tukey test) procedure to establish any differences among locations. Differences were considered significant at the p <0.05 level.

Results and discussion

Chemical composition

To the best of the authors’ knowledge, this is the first work that has studied the differences in the chemical composition, gross energy, DMD and FA profile of the green pruning residues of grapevine cultivars. The DM, CP and lipid contents of the GPR did not differ significantly among cultivars (Table 1), whereas ash, NDF, ADF and lignin contents of the GPR were significantly different, and ranged from 54 to 70, from 495 to 542, from 375 to 425, and from 91 to 142 g/kg DM, respectively. Kok et al (2007) reported lower nutritive values of shoot and leaf residues from the annual pruning of 4 cultivars, including Cabernet Sauvignon (CP 45 g/kg, NDF 325 g/kg, and ADF 248 g/kg).

The lipid content of the GPR ranged from 9 g/kg DM in Pinot Noir to 14 g/kg DM in the Grenache cultivar. Maier et al (2008) found that the total oil contents ranged from 29 to 43 g/kg for pressed seed residues and from 76 to 160 g/kg for grapevine seeds. Yi et al (2009) analyzed grape pomace powders, and found a lipid content of 68 g/kg for Royal Rouge and 73 g/kg for a Cabernet Sauvignon cultivar.

Table 1. Chemical composition (g/kg DM), gross energy (GE), and in vitro apparent digestibility (DMD) of the pruning residues of grapevine









DM (g/kg)









Crude protein









Ether Extract













































GE (MJ/kg DM)









DMD (g/kg DM)









abc Values with different letters within a row differ

In vitro digestibility

The apparent digestibility of the DM of the GPR is shown in Table 1. In the present study, relatively high values, ranging from 449 (Nebbiolo) to 544 g/kg DM (Barbera), were observed for all the cultivars. The DMD was similar for Sirah, Grenache, Cabernet Sauvignon and Pinot Noir As described in figure 1, DMD was correlated to the fibre fractions. Higher NDF, ADF and lignin corresponded to lower digestibility, in agreement with the results of Baumgärtel et al (2007).

All the digestibility values were higher than the average DMD reported by Feedipedia (Heuzé et al 2017) for grape branches and leaves However, very few studies have been conducted on the digestibility of grapevine pruning residues. Rebolé and Alvira (1986) determined the in vitro digestibility of fresh vine branches with their leaves, according to the Tilley and Terry (1963) method, and reported an average value of 427 g/kg.

Figure 1. Correlation between the cell wall contents (NDF, ADF and lignin) and in vitro apparent digestibility (DMD) of the pruning residues of grapevine

As the storage of fresh GP is difficult, because of its water content, Rebolé et al (1988) studied the digestibility of ensiled vine branches and leaves and found a reduction in DMD compared to the digestibility of fresh by-products. Some authors have analysed the vine leaves of Vitis vinifera. Kamalak (2005) reported DMD values, determined by means of Tilley and Terry’s method (1963), which ranged from 598 to 753 g/kg. Instead, Romero et al (2000) found a lower in vivo digestibility (422 g/kg), due to a high tannin content and a low digestibility of protein. Bersharati and Taghizadeh (2009) found an in situ DMD of dried grape by-products (grape cluster stems and rejected raisins) of 638 g/kg. Basalan et al (2011) determined in vitro digestibility using an Ankom Daisy Incubator, and the DMD value of the stalk was found to be 292 g/kg at 48 h.

The other data on the digestibility of grape by-products mainly refer to grape pomace. Winkler et al (2015) reported higher values in ensiled pomaces than in dried grape ones. On the other hand, some authors (Spanghero et al 2009; Pirmohammadi et al 2007b) found a reduction in digestibility due to ensilage. However, it has also been found that the digestibility of ensiled grape pomace can be increased by adding polyethylene glycol (Alipour and Rouzbehan 2007).

Trials on animals have shown that adding dried grape pomaces to ruminant diets has no negative effects on performance, and could be a good source of fibre (Bahrami et al 2010; Zalikarenab et al 2007).

Table 2. Fatty acid composition (g/kg of total FA) of the pruning residues of grapevine



































































































abc Values with different letters within a row differ

Fatty acid

The FA profile of the GPR (Table 2) was characterized by a low content of saturated FAs (SFA) and a high content of polyunsaturated FAs (PUFA), and of the latter, α-linolenic acid and linoleic acid ranged from 356 to 419 and 228 to 312 g/kg of total FAs, respectively. The content of linoleic acid differed significantly over the six cultivars, and the highest value was found in the GPR of the Pinot Noir cultivar.

Chitarrini et al (2017) highlighted the role of some FAs in response to abiotic stress, such as mechanical wounding of grapevine leaves (Bianca cultivar), and reported an increase in linoleic acid, α-linolenic acid and oleic + cisvaccenic acid during the first 12 h after injury.

Miele et al (1993) determined the FA composition of different lipid fractions of leaves, pericarps, skins, musts, and seeds of Vitis vinifera (Cabernet Sauvignon cultivar) collected at grape maturity. They found that α-linolenic acid was the most abundant acid in leaves, pericarps and skins, while linoleic acid was predominant in seeds. The unsaturated FA/SFA ratio was found to vary according to the lipid fraction and the tissue, and it decreased from seeds to leaves, pericarps and skins.

Santos et al (2011) determined the FA profile of the pulp, peel and seeds of Vitis vinifera (Benitaka and Brazil cultivars), and detected a total of twelve FAs in peels, eleven FAs in seeds and nine FAs in pulps. The main FAs were: linoleic, palmitic and oleic acid in the peels, linoleic, palmitic and α-linolenic acid in the pulp, linoleic, oleic and palmitic acid in the seeds, respectively. Hussein and Abdrabba (2015) found that the FA composition of the seeds of red grapes (Sultana cultivar) had a high PUFA content, and linoleic acid in particular (553 g/kg total FA), and this was followed by oleic acid (258 g/kg total FA), while palmitic acid was the dominant SFA (119 g/kg total FA). Lachman et al (2015) evaluated the FA composition in the seed of different grapevine cultivars, and reported that linoleic acid was the most abundant FA in all the analysed grape seed oils, contributing with between 68 and 78 g/100 g oil, while α-linolenic acid was only present in small traces, that is, from 0.29 to 0.77 g/100 g oil. Yi et al (2009) determined the FA composition of grape pomace powder (Cabernet Sauvignon and Royal Rouge cultivars) and found differences in the linoleic and α-linolenic acid contents, SFA, cis monounsaturated FA (MUFA) and n-6 PUFA; they also found a ratio of n-6/n-3 for the two cultivars.

Ju et al (2016) detected a total of sixteen FAs in grape skins (Pinot Noir cultivar). The main SFAs were palmitic, stearic, behenic and arachidic acid, and the main unsaturated FAs were linoleic, oleic and palmitoleic acid; α-linolenic acid was not detected.

Santos et al (2014) studied the effect of incorporating grape residue silage (at 0, 50, 75, or 100 g/kg of DM) in a diet containing soybean oil on the milk FA and antioxidant composition of lactating dairy cows. They reported an FA profile of grape residue silage that was characterized by five main FAs: linoleic (612 g/kg of the total FAs), oleic (192 g/kg of the total FAs), palmitic (125 g/kg of the total FAs), stearic (44 g/kg of the total FAs), and α-linolenic acid (41 g/kg of the total FAs). They reported that the supplementation had no effect on the total polyphenol and flavonoid concentrations in milk, while the PUFA/SFA ratio increased in milk fat as the grape residue silage was increased.



The authors thank Mrs M. Jones for the linguistic revision of the manuscript and Mr. T. Strano (Department of Agriculture, Forestry and Food Sciences, University of Torino) for the helpful collaboration in the field operations.


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Received 9 September 2017; Accepted 13 September 2017; Published 3 October 2017

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