RESEARCH WORK

Conservation and nutritional composition of the elder (Sambucus nigra) foliage

Teresa Carvajal Salcedo and Aurora Cuesta Peralta

Facultad de Ciencias Pecuarias, Universidad de Ciencias Aplicadas y Ambientales (UDCA) Campus Universitario, Calle 222 No. 55-37, Bogotá, Colombia.
E-mail: teresita.carvajal@gmail.com

ABSTRACT

The foliage of the tree species Sambucus nigra (elder) was evaluated as silage, hay or meal, in order to determine the most adequate method to preserve the plant species and use it in feeding programs to attenuate the negative effects of forage seasonality. The analyzed indicators were: silage efficiency, chemical composition and in sacco ruminal degradation of the dry matter (DM). At 30 days of fermentation, the silage showed 28,42 % DM, pH 4,28 and ammoniacal nitrogen (NH3-N) with regards to the total nitrogen (TN) of 13,60 %. Significant difference (p < 0,05) was found in the DM content of the silage (28,42 %), with regards to the hay (90,49 %) and the meal (90,77 %). The total protein content (TP) did not differ significantly among the three methods; however, the silage showed a higher content of the soluble protein fraction (49,80 %), compared with hay (27,30 %) and meal (30,00 %). In addition, the silage showed a higher content of non-structural carbohydrates (36,48 %) and a low lignin percentage (1,74 %), which differed significantly from the ones found in the hay and meal. The three methods showed significant differences (p < 0,05) in the DM degradability rate: 62 % degradability at 6 h, 77 % at 24 h and 80 % at 48 h, as average. It is concluded that the elder foliage preserved as silage, hay or meal was not nutritionally affected; likewise, silage was the most appropriate method, for preserving the nutritional quality.

Key words: silage, meal, hay, nutritional value.

Forage resources in the high tropic constitute one of the primordial energy sources for the ruminant; their composition is variable and is influenced by the seasonal conditions. For such reason, it is necessary to search for nutritional alternatives from non-traditional plant species, such as trees and shrubs, which are used in livestock production systems as material for fences, stables and pens, or as shade for the animals (Benavides, 1994; Ospina et al., 2005; Franco, 2008; Sánchez and Villaneda, 2009).

In order to reach a more sustainable production in rural zones, silvopastoral systems have been proposed as a short-, medium- and long-term alternative, with the introduction of trees in the pasturelands; which, besides providing good-quality forage for the animals, can be used as living fences, windbreaks, for the control of erosion and also to improve soil fertility and humidity (Chamorro, 2004; Jaramillo, 2005; Franco, 2008).

The inclusion of tree species in animal feeding systems, which show a higher protein and mineral content than grazing forages, can improve cattle productivity due to their effect on rumen functioning, by increasing the availability of ammoniacal nitrogen, aminoacids and peptides (Preston and Leng, 1990; Sánchez et al., 2009).

Elder (Sambucus nigra), shrubby plant which has turned out to be promising as forage bank, is extended in Europe, Asia, Africa and America. In its nutritional composition it has total protein percentage between 15,20 and 25,80 and low cell wall content (19,00-38,90 %), adequate values to be utilized by the animals.

Its foliage is well consumed fresh, important condition that guarantees appropriate characteristics of the preserved material from the tree waste, which can be included in the diets of the animals (Sánchez et al., 2009).

As forage conservation methods the following stand out: silage elaboration, based on fermentation by anaerobic bacteria; haymaking, produced by a fast evaporation of water (lower than 15 %); and meal elaboration, which is a dehydrated and finely ground material, with fiber particles of 1-2 mm from which 97 % passes through a sieve of 3,35 mm (ICONTEC, 1972).

In order to determine the most adequate method from the nutritional point of view, three elder forage conservation methods were compared: silage, hay and meal.

The study was conducted at the University of Applied and Environmental Sciences (UDCA for its initials in Spanish), in the facilities of the laboratory of animal nutrition, belonging to the School of Livestock Production Sciences, Program of Animal Management; it is located in the Bogotá D. C. savanna, Cundinamarca Department, at 2 660 masl, with an average temperature of 13 ºC and rainfall of 630 mm.

For the study the elder was selected due to its good adaptation to the high tropic, its availability and good nutritional quality. The foliage was obtained from silvopastoral systems established in the Mosquera municipality, Cundinamarca, in the dry season and under similar conditions to those of consumption by the animal. The trees were three years old and had a vegetative period of 90 days.

Treatments and design. The treatments consisted in three conservation methods: silage, hay and meal in a completely randomized design.

Silage. For the elaboration of the microsilos transparent plastic bags, 35 x 60 cm, caliber 6 with reinforced seal, identified by: material type, time of ensiling, elaboration date and time, were used. Three kilograms of material were weighed in each bag, in triplicate; 5 % of molasses was added, it was manually compacted, the air was extracted through a vacuum pump and the remainder end of the bag was twisted to close it hermetically. Each bag constituted a microsilo. The microsilos were stored during 30 days, in capped black plastic tanks.

Hay. For the haymaking process of the tree foliage, the material was cut and dried under environmental conditions, under a shed located in a nursery; it was extended and turned twice a day during 72 h. Once the material was dried, it was stored in 1-kg microsacs, in triplicate.

Meal. For the drying process the same methodology as for the hay was followed; the dehydrated forage was crushed in a Willey mill, with a sieve of 1-mm opening, which allowed that all the material passed through the sieve and it came out with a particle size equal to or lower than 1 mm, taking the aspect of meal.

Chemical and nutritional evaluation. The nutritional content of the whole foliage was evaluated, as it is generally offered to the animals, as well as of the fractions that constitute it.

In order to know the fermentation quality of the silage 30 days after being elaborated, the following elements were determined, immediately after opening the bags: pH, through a potentiometer; percentage of ammoniacal nitrogen (NH3-N) and of total nitrogen (TN), according to the AOAC International (2003); and dry matter, through the technique proposed by Harris (1970).

For the nutritional evaluation of the different treatments, the percentages of dry matter (DM), total protein (TP), content of total minerals measured as ash (A), organic matter (OM) calculated by difference with C, content of neutral detergent fiber (NDF), cell content (CC) obtained by difference with the NDF content, and non-structural carbohydrates (NSC) calculated by difference with TP, EE, C and NDF (AOAC International, 2003). In the case of the fractioning of carbohydrates and proteins (CNCPS), the methodology described by Van Soest and Robertson (1985) and by Licitra et al. (1996) was followed.

Degradability conditions. The in sacco degradability of DM was conducted at times 0, 6, 24, 48, 72 and 96 h of ruminal incubation, in two cannulated Holstein cattle, fed with kikuyu grass (Pennisetum clandestinum) and supplemented with mineral salt; Ankon polyester bags, 20 x 10 cm and pore of 53 micra, were used (Ørskov et al., 1980).

Antinutritional factors. The contents of tannins and saponins were qualitatively evaluated (Galindo et al., 1989).

Statistical analysis. The GLM procedure of SAS was used; the means were compared through the Benferroni test (SAS Institute, 1995)

RESULTS AND DISCUSSION

Fractions of the elder (S. nigra) foliage and their nutritional variation

Table 1 shows the characteristics of the foliage used in the trial; the elder fractions are related, as well as the nutritional composition of each.

From the fresh foliage 86,7 % was constituted by leaf-petiole and stem, with a content of 77,5 % of L-P in an 8,5:1 ratio. If it is considered that this fraction in the plant materials can be easily degraded, due to the high proportion of mesophyll tissue, it must be assumed that the foliage showed an important nutritional composition. This high ratio (L-P-S) was maintained when the material was dehydrated, and influenced the percentage of dry matter reached in the whole foliage.

The seeds made an important contribution of TP (30,97 %), but their representation in the whole material was low; thus, the protein content of the whole foliage was more related to the L-P contribution (18,70 %), as it was the fraction of higher proportion in the total material.

The concentration of total minerals in the stem decreased in 50 % with regards to the other fractions, which had values over 10 %; nevertheless, as the stem represented 11,1 % of the whole material it did not influence drastically the content of total minerals of the whole foliage.

According to the organoleptic characteristics of the elder silage, such as the light green color (belonging to silages with good respiration) and nice smell, it is qualified as of good quality (Bernal et al., 2005).

Table 2 shows the results of the chemical fermentation indicators at 30 days.

The elder silage showed a pH of 4,28 after 30 days, which indicates that the conservation process was efficient during the period in which fermentation occurred; in this sense, the literature states that in ensiled and adequately preserved materials, a pH close to 4 is sufficient to preserve the crop (McDonald et al., 1995).

The NH3-N, which represents the protein breakdown during the process, showed a relation of 13,6 % with the TN; this value is adjusted to the condition of a good quality silage, which should be equal to or lower than 15 % (Pereira et al., 2007).

The dry matter was higher in 8 percentage units, compared with that of a mixed elder-oat-thorn tree silage (28 vs. 20 %), studied by Blanco et al. (2005). This DM content meant 80 g more of DM per kilogram of silage offered with regards to the mixed silage, which would allow a better production in the livestock production farms that adopt feeding with this tree material. In addition, it was adequate to obtain in the silage the required pH for conservation, value which according to McDonald et al. (1995) should be higher than 20 %.

The silage DM differed significantly (p < 0,05) from that of the hay and the meal; however, these last ones did not show differences in the average DM content (table 3) in spite of the dehydration or drying processes to which the elder was subject, similar performance as the one reported in literature (Bernal et al., 2005).

The total protein did not show significant differences, with average values of 16,90 % for the three methods; this indicates that the protein from elder was not affected by the conservation method used. These values are higher in 4,8 percentage units than the average value reported for a mixed silage of elder, thorn tree and oat (Blanco et al., 2005), in 5 units for a barley silage and in 8,7 percentage units for an oat silage. Besides, they are comparable to those of alfalfa hay and meal, for which average contents of 17 % of TP are reported (Laredo and Cuesta, 1988; National Research Council, 2001).

The content of total minerals, represented by ash, showed an average of 10,7 %. On the other hand, the silage differed (p < 0,05) from the other methods and it was higher in 0,43 percentage units. The adequate ash content of the different preserved materials indicates the importance of establishing which minerals are present and in what amount; this allows to determine the mineralized salt that should be used when this tree is supplied. These ash values are in correspondence with the ones reported in literature (Nova et al., 2005).

The organic matter showed an average of 89,3 % in the three conservation methods, adequate value for an efficient rumen functioning; the silage exceeded in 0,6 percentage units the hay and meal (p < 0,05). This indicator is important for the ruminant, because it is the source of the carbonated skeletons for the synthesis of secondary metabolites which occurs from the ruminal function (Navas, 1995).

The ethereal extract significantly differed among the three conservation methods (p < 0,05) and its average percentage (5,63 %) was higher in 2-3 percentage units with regards to the one reported for the forages (National Research Council, 2001). This content coincides with the quantities reported for ruminant diets, which are normally low in fat (1-5 %) because the rumen is intolerant to high quantities.

The cell content, which indicates the highly digestible nutrient percentage, statistically differed (p < 0,05) for the three conservation methods. In the case of the silage, the average value (69,32 %) indicates that it supplied a higher quantity of easily-disposed nutrients in the rumen ecosystem, which is important for a higher animal production (Navas, 1995).

The results for the protein fractions through the CNCPS system (Fox et al., 2004) are shown in table 4.

The fraction A or non-protein nitrogen (NPN) in the silage, with 12,07 %, significantly differed (p < 0,05) from that of hay or meal, whose average was 5,07 %; it could be due to the dehydration process which occurs during their elaboration.

The fraction B1 or soluble true protein of the silage (37,70 %), showed significant differences (p < 0,05) with regards to hay (22,50 %) and meal (24,50 %). The value of the fraction A + B1, which forms the soluble protein of fast degradation (SF), which was 49,80 % in the silage, higher in 21,10 units with regards to the other two methods. This value turned out to be higher than those of the silages of Avena sativa (23,69 %), Zea mays (28,72 %) and Hordeum vulgare (43,70 %) (Fox et al., 2004), and higher than the mixture of oat, elder and thorn tree (29,90 %) (Blanco et al., 2005), and is within the SF range (4,60-82,39 %) reported for the forage tree species used in cattle production systems (Chamorro, 2014).

In the fraction B2 of the silage significant differences were observed (p < 0,05) compared with that of hay and meal. In the three methods a range was appreciated between 20 and 28 % of true protein of intermediate ruminal degradation (70-85 %) and possibly used by microorganisms (Sniffen et al., 1992).

One of the most important fractions in cattle supplementation is the bypass protein or fraction B3. It did not show significant differences between silage and hay; while the meal showed 4,56 percentage units less with regards to the other two methods. The fraction B3 is slowly degradable in the rumen (5-15 %) and is associated to the cell wall (Sniffen et al., 1992).

The fraction C represents the protein fraction that is not used in the gastrointestinal tract of the ruminant. The hay material and the meal did not show significant differences, and the lowest percentage of fraction C was found in the silage (10,50 %); this value is related to a higher availability of digestible protein, and coincides with the report by Blanco et al. (2005) for a mixed silage of oat, elder and thorn tree (11,32 %). The contents of this fraction in the preserved materials are located within the range reported for forage tree species (Chamorro, 2014).

Due to the breakdown of the proteins in the ensiling process, the SF fraction showed significant difference (p < 0,05) with regards to the hay and the meal. If it is compared with the mixed silage of elder, thorn tree and oat (Blanco et al., 2005), this silage showed higher SF (49 vs. 31 %), lower fraction B2 (28 vs. 24 %), similar content of B3 (11 vs. 10 %) and lower fraction C (10 vs. 15 %).

The hay and meal, comparatively with the alfalfa meal (19 % TP), provide lower fraction A (5 vs. 27 %) and B (54 vs. 66 %) and higher fraction C (49 vs. 6 %); this indicates that for each offered kilogram of this material, the animals will receive 171 g of TP, and from them 48 g would be indigestible (fraction C).

In the NSC significant differences were found (p < 0,05) for the three conservation methods (table 5); the silage showed a higher quantity of NSC, which constitutes an important energy source that facilitates at rumen level the synergism of the contribution of fast-degradation proteins and carbohydrates and increases the degradation of structural carbohydrates.

The hay and meal showed, as average, a higher content of NDF (40,80 %) compared with the silage (30,68 %), which was similar to the one reported by Barreto and Chamorro (2005) for a mixed silage.

In the ADF there were also significant differences (p < 0,05) between the silage and the other two methods. The silage showed an ADF content lower in 6 % than the one reported by Barreto and Chamorro (2005), which allows to predict higher digestibility of the material.

The lignin, phenolic compound indigestible by the animal, was statistically different (p < 0,05) in the silage with regards to the hay and meal, which allows to state that nutritionally the best conservation method was the first. The higher lignin values in the hay and meal were related to a higher content of the fraction (lignin-bound fraction) of the protein. The lignin percentage in the three methods was lower than the one reported for alfalfa (National Research Council, 2001); however, it is not considered a negative factor for the degradability of the material.

The hemicellulose showed significant differences (p < 0,05) among the three treatments, and in the silage this indicator was 3 % and 6 % higher than the hay and meal, respectively.

On the other hand, the cellulose did not show statistical differences between the hay and the meal; the silage was lower in 10 percentage units with regards to the other two methods, with a similar value to the one reported by Blanco et al. (2005) for a mixed silage of elder, thorn tree and oat (19,3 vs. 20,7 %).

The nutritional composition of this tree preserved with any of the methods allows to recommend it as an important source of nutrients in animal feeding, especially the silage.

The in sacco degradability of the dry matter for the elder, in the different incubation times, is shown in table 6.

The solubility rate (T0) of the silage exceeded in 10 percentage units that of hay and meal; nevertheless, at 24 hours interrelation was observed and the average degradability was 77,70 % for the three methods. This allows to qualify this tree as a good quality feedstuff (higher than 40 %), according to the report by Preston y Leng (1990).

The average DM degradability for the three methods at 48 h increased in 2,80 % with regards to that of 24 h (80,50 vs. 77,70 %). This indicates that the material with a permanence time of 24 h in the reticulum-rumen showed a high content of utilizable material; however, the maximum time would be 48 h. The high degradability that occurred in the three conservation methods was related to the higher content of leaves plus petiole (79 %), structures associated with a lower lignification, high ruminal degradation and low cell wall content (Chamorro et al., 2005).

The rumen-degraded protein (DP), highly important in ruminant nutrition, because it participates in the production of microbial cells, was 88,95 % for the meal; 87,66 % for the hay and 85,82 % for the silage. This allows to infer that the quantity of non-degraded (NDP) and utilizable protein in the second digestive process would be, as average, 12,50 %. In this indicator there were significant differences (p < 0,05) among the three methods: silage: 14,18 %, hay: 12,34 %, and meal: 11,05 %. Such values are lower than the ones reported for the bypass proteins of alfalfa hay (25 %) and that of a silage (30 %), with less than 45 % of NDF (National Research Council, 2001), and are related to the values of the slowly degradable protein fractions (B1 + B2 + B3) (table 4).

Taking into consideration that secondary metabolites are one of the limitations for the intake and acceptability of shrubs and trees for ruminants (Carulla and Lascano, 1994), the presence of tannins and saponins in the three conservation methods of the elder foliage was qualitatively evaluated.

The tannin contents were very low (lower than 0,3 %) and were negative in the case of saponins, which allows to infer that these antinutritional factors did not limit the digestion of nutrients, or affected the nutritional quality of elder in any of the material preservation methods.

The elder preserved as silage, hay or meal showed a low content of cell wall and a high degradability of dry matter and protein; no secondary metabolites were found.

The comparison of the three conservation methods, from the nutritional point of view, proved that silage is visualized as the most adequate one, for showing higher protein and cell content percentage, lower lignin quantity and an adequate degradability of dry matter.