Livestock in extensive systems extends to 30 % of the world's rainforests, and is associated with high deforestation levels and with the vocation change in soil use (FAO 2018). Livestock production is associated with the change in soil use, causes a decrease in biodiversity, environmental services and alters biological cycles and ecosystems, which contributes to the planet's climate change. Considering the problem, under the Amazonia conditions it is urgent to restructure livestock to environmentally friendly systems, in which grass monocultures were replaced by natural grasses, with less water requirement and perennial plant species and silvopastoral systems that diversify the forage supply (Gomez et al. 2017).
The nutritional content of tropical grasses, the lack of knowledge of the new species and their limited fiber degradability by herbivores, are limitations for animal productivity in the Amazonian piedmont. Some farmers use grazing systems in silvopastoral systems, which allow increasing and diversifying the forage supply, to improve the diet quality and ensure the conservation and recycling of nutrients, under the particular conditions of the Amazonian soils (Vivas et al. 2017).
In the same way, production per unit area should be maximized, due to current food production needs, taking into account the new challenges of the ecological livestock , which contributes to the reduction of greenhouse gases (GHG) and the reduction of contaminants (Fajardo et al. 2014).
It is known that variations in the intensity and frequency of rainfalls, El Niño phenomenon and high temperatures affect food production. Specifically, in the Amazonia, tropical grasses are generally characterized by having low amounts of biomass and low nutritional quality, which is due to the soils quality. For these reasons, farmers need to find new materials that help to improve the food supply for their animals (Gallego-Castro et al. 2016). The forage supply, with trees and shrubs, compared to that of grasses, tends to better preserve organic matter (limiting factor), due to the return to the soil of leaves, fruits, branches, faeces and urine, which is mainly derived from the increase of the edaphological activity of the soil through the nutrients recycling, especially in acid soils and deficient in elements such as phosphorus and potassium, high in iron and aluminum, characteristic of the Amazonia (Townsend and et al. 2010).
Forage resources are the basis of nutrition and ruminants feeding, they provide the highest percentage of nutrients for their own productive and reproductive performance. However, the trees have a very variable composition, due to multiple factors that affect their quality. Using tree forage in animal feeding is a challenge for researchers exploring new resources in the Amazonia (Morales-Velasco and Teran-Gomez 2016). This can only be achieved through the knowledge of the food resources available to each region and considering the need to optimize the use of alternative sources for animal feeding under humid tropics conditions.
The objective of this research was to carry out the nutritive characterization of trees from the Amazonian piedmont, in Putumayo department, Colombia.
Materials and Methods
The study was carried out at Villa Lucero farm, located at coordinates 0°35'25.6 "N and 76°32'05.3" W in Putumayo department, Colombia, 256 m.o.s.l. The average temperature of the region is 25.3ºC, with 85 % relative humidity and 3355 mm of annual precipitation (IDEAM 2017). This region corresponds to the tropical humid forest (Holdridge 1947).
The soils of this region are characterized by being of clay-loam and clay respectively. They are acidic soils (pH 4.6), low in phosphorus (<1.7 mg kg), with high contents of aluminum (> 3.2 cmol / kg) and iron. The soil was not irrigated and the plants were not fertilized during the experimental period. The study area was 1.5 ha and 2,500 m2 plots were used for each of the six local forage species: Tithonia diversifolia (Asteraceae), Trichantera gigantea (Acanthaceae), Pictocoma discolor (Asteraceae), Clitoria fairchildiana (Fabaceae), Hibiscus rosa sinensis (Malvaceae) and Solanum rugosum (Solanaceae).
Characterization of forage species. The forage samples to be evaluated had a regrowth age of sixty days. A total of fifteen samples of a plant were taken in zig-zag from each plot of the crop, cutting from one meter. Leaves and stems were collected, harvested from the basal part of the regrowth in the summer season in June. From each species, three 200 g samples were taken for laboratory analysis. The samples were weighed and oven dried at 60 °C for 48 h. Later, they were ground in a hammer mill, until reaching a 1 mm size.
Nutritional analysis. It was performed by NIRS spectroscopy. After homogenization, the samples of round and dried forage were placed in a 50mm diameter recipient and scanned from 400 to 1098 and from 1100 to 2498nm, in 2nm increments. A VIS / NIR spectrophotometer (Foss NIR Systems model 6500; www.foss.com) was used. The spectrums were recorded with WinISI 4.7.0 (www.foss.com), in the AGROSAVIA laboratory at Mosquera (Cundinamarca).
The variables dry matter (DM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (L), hemicellulose (Hc), digestibility, metabolizable energy in ruminants (ME), calcium (Ca), phosphorus (P), sulfur (S), magnesium (Mg), zinc (Zn), copper (Cu), phenols (F), total tannins (Tt) and total alkaloids ( Ta) (C Ariza-Nieto et al. 2018) were evaluated. For the qualitative content of secondary plant metabolites (SPM), qualitative tests were carried out in the specialized laboratories of the Universidad de Nariño. Saponins, phenols and sterols were characterized on the negative, low, moderate and abundant scale. The methodology described by Domínguez (1973) and Bilbao (1997) was followed.
Statistical analysis. The characterization of the forage plants was carried out using descriptive statistics, with the calculation of the position and dispersion statisticians: mean, standard deviation and coefficient of variation. The InfoStat statistical program (Di Rienzo et al. 2012) was used to process the data.
Results and Discussion
Table 1 shows the chemical composition of the forage plants. The values found for Piptocoma discolor (Pd) are higher than those reported by Mendoza et al. (2014), with 20.18 % protein and 24.87 % dry matter, so this species is considered to have high potential for silvopastoral systems, due to its good growth and volume. Mendoza et al. (2014), in a study carried out under the Ecuadorian Amazonia conditions, recommend it to establish forest and agroforestry plantations, due to its high crude protein content. However, these values are lower with respect to the protein contents of the species Tithonia diversifolia, and Piptocoma discolor (23.6 % and 20.18 %, respectively), used in the silvopastoral systems of Caquetá. Guayara (2010) reported values of 39.79 % of NDF and 36.06 % of ADF for this last tree, figures that can be considered medium to high. This reference motivates research for the establishment and massification of this species in silvopastoral systems for browsing (Hurtado and Suárez 2013).
Nutrient | ||||||
---|---|---|---|---|---|---|
DM (%) | 28.857 | 30.267 | 18.737 | 35.013 | 24.233 | 27.870 |
SD | 0.785 | 1.007 | 3.095 | 1.536 | 3.751 | 0.297 |
CV (%) | 2.720 | 3.326 | 16.518 | 4.386 | 15.479 | 1.066 |
CP (%) | 21.513 | 13.200 | 16.560 | 18.077 | 19.000 | 19.107 |
SD | 1.654 | 0.694 | 5.010 | 1.102 | 1.577 | 0.768 |
CV (%) | 7.690 | 5.257 | 30.255 | 6.096 | 8.301 | 4.022 |
EE (%) | 3.947 | 3.500 | 2.217 | 2.167 | 2.777 | 3.340 |
SD | 1.703 | 2.312 | 0.207 | 0.509 | .497 | 1.541 |
CV (%) | 43.149 | 66.069 | 9.358 | 23.472 | 17.901 | 46.152 |
ME Rum. (Mj/kgMS) | 10.258 | 9.057 | 9.295 | 9.281 | 9.630 | 9.183 |
SD | 0.126 | 0.064 | 0.126 | 0.097 | 0.231 | 0.020 |
CV (%) | 1.224 | 0.706 | 1.351 | 1.042 | 2.395 | 0.215 |
NDF | 46.607 | 33.003 | 34.367 | 47.300 | 43.577 | 47.973 |
SD | 15.392 | 8.900 | 16.480 | 19.248 | 5.823 | 4.940 |
CV (%) | 33.026 | 26.967 | 47.954 | 40.693 | 13.362 | 10.298 |
ADF | 27.250 | 17.133 | 21.763 | 32.130 | 24.600 | 33.493 |
SD | 18.245 | 3.283 | 16.766 | 16.700 | 10.282 | 3.639 |
CV (%) | 66.955 | 19.161 | 77.038 | 51.975 | 41.798 | 10.866 |
Lignin (%) | 5.423 | 5.067 | 5.213 | 7.483 | 5.430 | 8.530 |
SD | 1.939 | 2.464 | 2.613 | 1.541 | 2.589 | 0.290 |
CV (%) | 35.751 | 48.623 | 50.117 | 20.586 | 47.683 | 3.399 |
Hem. (%) | 25.717 | 11.800 | 13.600 | 15.173 | 20.200 | 13.423 |
SD | 8.189 | 1.441 | 1.480 | 2.652 | 2.610 | 0.193 |
CV (%) | 31.845 | 12.211 | 10.882 | 17.475 | 12.922 | 1.440 |
Digest. (%) | 74.710 | 65.060 | 66.233 | 66.247 | 68.993 | 65.447 |
SD | 4.446 | 0.285 | 0.750 | 0.189 | 1.007 | 0.012 |
CV (%) | 5.951 | 0.438 | 1.132 | 0.285 | 1.460 | 0.018 |
The values found for the forage Hibiscus rosa - sinensis (13.20; 3.50; 33.00 and 17.13 % for protein, EE, NDF and ADF, respectively) are lower than those reported by Meza et al. (2014). According to Huanca et al. (2017), this species is a fast growing tree with biomass availability and is used as post wood. In addition, it has good palatability for cattle, which prefer it over other species.
For the tree Trichantera gigantea, Moreno-Lopez (2014) reported similar values to those found in this research (24.23; 19.0 and 2.78 % for DM, CP and EE, respectively). These results are higher to those obtained by Valarezo and Ochoa (2013), with 18.18 % for CP and 1.88 % EE. Bejar (2017) refers that this shrub is a promising species as an alternative for supplementation in cattle diets.
In the Tithonia diversifolia species, the contents of CP, NDF and Hc in this study are lower than those reported by Rodriguez (2017) in their characterization of different plant materials. The obtained values ranges from 18.26 to 26.40 %, 32.62 to 41.83 % and 14.79 to 25.74 % for CP, NDF and Hc respectively, which denotes high variability in the data. Rivera et al. (2018) reported that this species has a high biomass production and superior chemical composition with respect to most of the grasses used under tropical conditions. In addition, it has a good edaphoclimatic adaptation. The EE values (2.0 %) were higher than those obtained by Chamba (2016), which makes this species a forage alternative to use in sustainable animal production systems in the Amazonian piedmont.
The mineral composition of the forage plants is shown in table 2. The Zn and Cu values for the Trichantera gigantea tree are higher compared to the other forage plants under study. The Ca content was in a range of 2.22 to 2.63 %, higher than the one found by Rivera et al. (2017), like P 0.29 %.
Nutrient | ||||||
---|---|---|---|---|---|---|
Ca (%) | 0.76 | 0.71 | 1.10 | 0.83 | 0.97 | 0.97 |
SD | 0.01 | 0.02 | 0.02 | 0.04 | 0.08 | 0.01 |
CV (%) | 0.76 | 2.14 | 1.90 | 4.34 | 8.05 | 1.22 |
P (%) | 8.17 | 8.26 | 10.76 | 6.01 | 10.03 | 8.34 |
SD | 0.02 | 0.01 | 0.02 | 0.01 | 0.02 | 0.01 |
CV (%) | 6.03 | 25.00 | 8.65 | 6.25 | 6.89 | 4.98 |
Mg (g/100gDM) | 0.22 | 0.21 | 0.25 | 0.23 | 0.31 | 0.22 |
SD | 0.01 | 0.01 | 0.01 | 0.01 | 0.03 | 0.00 |
CV (%) | 4.55 | 2.71 | 4.56 | 4.95 | 7.98 | 1.06 |
S (g/100 gDM) | 0.10 | 0.08 | 0.12 | 0.15 | 0.17 | 0.10 |
SD | 0.01 | 0.01 | 0.01 | 0.01 | 0.02 | 0.00 |
CV (%) | 10.00 | 12.50 | 4.68 | 3.94 | 11.27 | 0.00 |
Cu (g /100gDM) | 6.62 | 4.10 | 6.31 | 5.77 | 8.50 | 7.30 |
SD | 0.06 | 0.03 | 0.10 | 0.22 | 0.63 | 0.01 |
CV (%) | 0.88 | 0.75 | 1.59 | 3.80 | 7.36 | 0.16 |
Zn (mg/kgDM) | 28.37 | 27.82 | 28.46 | 26.24 | 36.56 | 30.08 |
SD | 0.45 | 0.10 | 0.82 | 0.30 | 3.14 | 0.05 |
CV (%) | 1.57 | 0.35 | 2.88 | 1.14 | 8.58 | 0.17 |
Table 3 shows the anti-nutritional factors of the forage plants. The qualitative analysis showed that the saponins in the Piptocoma discolor are in a higher value, in relation to the other forage plants. This could have an effect on the ruminal fermentation pattern. Alayón et al. (2018) reported about 50 species rich in tannins and saponins, with the potential to mitigate CH4 in enteric fermentation of ruminants. González García et al. (2018) found, under in vitro conditions, the ability of this compound to inhibit methanogenesis and the population of ciliated protozoa.
Ingredient | Phenols (%) | Condensed tannins (%) | Total alkaloids (%) | Sterols | Saponins | Phenols |
---|---|---|---|---|---|---|
2.45 | 0.27 | 0.46 | Low | Low | Moderate | |
SD | 0.11 | 0.02 | 0.05 | |||
CV (%) | 4.49 | 5.73 | 10.65 | |||
2.61 | 0.77 | 0.87 | Low | Negative | Moderate | |
SD | 0.02 | 0.01 | 0.05 | |||
CV (%) | 0.77 | 4.03 | 5.76 | |||
3.16 | 0.28 | 0.63 | Low | Negative | Moderate | |
SD | 0.15 | 0.02 | 0.02 | |||
CV (%) | 4.79 | 7.14 | 3.32 | |||
3.67 | 0.39 | 0.59 | Low | Negative | Moderate | |
SD | 0.03 | 0.01 | 0.02 | |||
CV (%) | 0.79 | 2.56 | 2.60 | |||
1.15 | 0.24 | 0.30 | Low | Negative | Moderate | |
SD | 0.16 | 0.02 | 0.03 | |||
CV (%) | 13.97 | 8.67 | 9.08 | |||
1.41 | 0.14 | 0.57 | Low | Negative | Moderate | |
SD | 0.02 | 0.01 | 0.00 | |||
CV (%) | 1.50 | 5.05 | 0.00 |
Terranova et al. (2014), when supplying 0.4 g/L of saponins in the diet, found that this metabolite, in moderate doses, can reduce the use of ruminal protein, increasing the flow of duodenal protein and reducing ammonia concentrations in the rumen, with 18.4 % increase in microbial protein mass and 8.3 % reduction in ammonium concentrations. This can be an important alternative for the supplementation of this forage in silvopastoral systems at the Amazonian piedmont.
In all the evaluated forage plants, the phenolic compounds content was moderate. However, the results show that Clitoria fairchildiana has the highest content, when compared with that reported in studies by Verdecia et al. (2018). These authors found that the values of these compounds are below to those reported in the edible fraction of some legumes from production systems in the tropics, showing the quality of this species to be use in animal feeding.
In the qualitative analysis, the forage plants do not report alkaloids. The results show that the highest proportion corresponds to Hibiscus rosa - sinensis. For this same species, the lowest tannin value was reached with 0.02 %. Authors such as Obrador et al. (2007) report that there is variation in the productive and metabolic response of growing ruminants, when using this tree harvested at different cutting frequencies, which is explained by the different concentrations of condensed tannins that affect the intake and the ruminal metabolism. Being this species palatable for its good palatability in cattle; deeper studies in silvopastoral systems are needed.
Different researches shows the effect of intake high tannin diets on ruminants. Authors like Ramirez (2018) suggest that the ingestion of tannins inhibits the growth of rumen proteolytic microorganisms. Tituaña (2018) found that the ingestion of condensed tannins (CT) decreases the digestibility of the protein and NDF as the rumen fermentation patterns. The plant CT reduce the ruminal methanogenesis by decreasing hydrogen formation. Sánchez et al. (2018) found a greater amount of total viable and proteolytic bacteria, and a higher concentration of SCFA in animals that intake multiple mixtures of herbaceous legumes without tannins. This suggests that Clitoria fairchildiana, with 2.72 % of CT is the one that could have less use by ruminants.
Conclusions
According to the characterization of shrubs in the Amazonian piedmont, the species Piptocoma discolor, Trichantera gigantea and Hibiscus rosa sinensis have an adequate content of protein, energy and digestibility. Tithonia diversifolia, Clitoria fairchildiana and Solanum rugosum have adequate mineral content and moderate content of secondary metabolites. All have acceptable levels of nutritional components that make possible their use in animal feeding.