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The alternative resources constitute a viable option to mitigate the costs of pigs feeding in extensive and semi-extensive rearing houses (Lezcano et al. 2014). Ecuador have an excellent potential, as to the alternative foods production for their use in this animal category, among which is the guava fruit (Psidium guajaba L.). In tropical and subtropical areas, this crop is cultivated and harvest twice a year in February-May and August -November. The regions of higher cultivation are the provinces Orellana, Pastaza, Pichincha, Esmeraldas, Azuay, Zamora Chinchipe and Tungurahua, but the main production line is in the cantons of Baños, Mera, Pastaza, Santa Clara, Palora and Joya de los Sachas. In Pataza canton, this crop is established in the most part of the farms from agricultural farmers (Morocho 2017).
The commercial production of guava fruit begins in Ecuador from a third year, with an average of 3 t/ha/year, which reaches 26 t/ha/year in the eighth. In selected crops a production of 35 t/ha/year is achieved. The greatest part of the fruit is use for the production of jellies, yogurt, wines and jams. However, there is a surplus which not fulfill with the parameters for commercialization and it is not assess for animal feeding due to its high humidity content the changeable characteristics of the fruit (Marquina et al. 2008), and, after harvested suffers the attack of microorganisms that causes the decomposition of this raw matter (MAGAP 2023).
For the preserving of these resources for a long time and for their use in pigs feeding (Caicedo et al. 2019) fermentative process can be used (silage). The traditional fermentative technique is performed with the use of lactic bacteria culture on the raw matter slightly chopped, under anaerobic conditions. However, in the fermentation of agricultural byproducts, today are applying inclusion variants of the draying material to improve the dry matter content and the nutrients concentration of the fermented food (Borrás-Sandoval et al. 2017 and Caicedo et al. 2019).The objective of this study was to evaluate the chemical characteristics of the ripe guava fruit (Psidium guajaba L.) silage for their use in pigs.
Materials and Methods
Location. The research was performed in the Microbiology and Bromatology laboratories from the Universidad Estatal Amazónica. The study was carried out in Pastaza canton, Pastaza province, Ecuador. This region has a subtropical humid climate, with high rainfalls (4000 to 4500 mm annuals), relative humidity of 87 % and altitude of 900 m o.s.l. The temperatures vary between 20 and 28 ºC (INAMHI 2014).
Preparation of the ripe guava fruit silage. For the silage preparation ripe and fresh guava fruit was used, from Caicedo Agricultural Farm. After the harvest, the fruits were washed with drinking water for human consumption and they leave drained for 10 min. They were immediately milled in a hammer mill with 2cm sieve. Later the milled raw matter was taken to the Microbiology laboratory from Universidad Estatal Amazónica. To formulate the silage, there were combined chopped ripe fruit, wheat dust, sugar cane molasses, vitamin and mineral premixture, calcium carbonate and natural yogurt (table 1). All the raw matter was weighed in a CAMRY digital scales, model Ek9150k, from China, with 5000 g capacity and ± 1 g precision. The mixture was placed in 24 plastic micro-silos with 1kg capacity, whose content was analyzed in different conservation times (0, 1, 4, 8, 15 and 30 d). A total of four micro-silos per conservation time were evaluated, throwing out every time the respective measurements were performed.
Table 1 Inclusion of raw matters and additives for the elaboration of ripe guava silage
| Raw matters | Inclusion, % |
|---|---|
| Chopped ripe guava | 90.0 |
| Wheat powder | 6.0 |
| Sugar cane molasses | 2.0 |
| Vitamins and minerals1premixture | 0.5 |
| Calcium carbonate | 0.5 |
| Natural yogurt | 1.0 |
1 Each kg contain: calcium 17 a 20%; phosphorus 18%; NaCl 0.5 a 1%; magnesium 3.0%; biotin 50 mg; zinc 8000 mg; manganese 1500 mg; iron500 mg; copper 2000 mg; iodine 160 mg; cobalt 30 mg; selenium 70 mg; vitamin A 300 000 UI; vitamin D3 50 000 UI; vitamin E 100 UI; calcium-phosphorus ratio 1.3:1; zinc-copper ratio 4:1
Determination of the chemical components of guava fruit silage. The chemical components of the silage were determined in the Bromatology Laboratory from Universidad Estatal Amazónica. For that three random samples of 1kg of the silage were taken, from the micro-silos of eight days post-elaboration. The time of the chemical characterization was established in function of Rodríguez (2008) and Lezcano et al. (2014) suggestions. In the fermented food was determined the dry matter (DM), crude fiber (CF), ash, crude protein (CP), ether extract (EE) and nitrogen free extract (NFE), according to the AOAC (2005) recommendations . The gross energy (GE) was determined in an adiabatic calorimetric pump, Parr brand, model 1241, from United States. All the analyses were made in triplicate.
Checking of the pH in the guava fruit silage. The determination of the pH was performed with a standard portable meter, Milwaukee brand, model MW102, American production. The checking was made in 24 micro-silos at 0, 1, 4, 8, 15 and 30 d of conservation (four micro-silos in each study). The pH measurement was made by the Cherney and Cherney (2003) procedure.
Experimental design and statistical analysis. For the analysis of the chemical components of the silage descriptive statistical was used and the mean, standard deviation and variation coefficient were determined. To analyze the pH data of the food a completely random design was applied. The treatments were the fermentation days 0, 1, 4, 8, 15 and 30 and Duncan (1955) test with (p ≤ 0.05) to contrast means was applied. All the analyses were carried out with the statistical program InfoStat (Di Rienzo et al. 2020).
Results and Discussion
The use of different raw matters and additives in a combination with the ripe guava fruit make a silage food of an appreciable nutritive quality for pigs feeding (table 2).
Table 2 Chemical components of the ripe guava fruit silage (dry base , n=3)
| Nutrients | Mean | Standard deviation | Variation coefficient , % |
|---|---|---|---|
| DM, % | 22.61 | 0.01 | 0.01 |
| CP, % | 13.51 | 0.10 | 0.20 |
| CF, % | 9.90 | 0.57 | 0.40 |
| SE, % | 6.08 | 0.01 | 0.02 |
| Ashes, % | 10.24 | 0.09 | 0.1 |
| NFE, % | 72.49 | 1.60 | 1.96 |
| GE, kJ g DM-1 | 18.54 | 3.33 | 2.76 |
The inclusion of the wheat powder as drying material improves the DM content of the silage, from 12 to 13 %, with respect to the fruit in natural state (Torres 2010), which is beneficial to keep the food for a long time and avoid loses due to decomposing microorganisms. Nkosi et al (2016) state that the high DM content in the silage limits the developing of putrefactive microorganisms. The increase in the protein value is due to the colony forming units (CFU) of lactic acid bacteria and yeasts which are develop during the fermentative process (Gunawan et al. 2015, Caicedo et al. 2020 and García et al. 2020). The increase in the concentrations of ash, ether extract, nitrogen free extracts and energy is due to the inclusion of different raw matters and additives which was made the silage (Borrás-Sandoval et al. 2017 and Fonseca-López et al. 2018).
The nutritional composition of the ripe guava fruit silage is similar to some types of silages from agricultural byproducts used in pigs: cassava root (Reina-Rivas et al. 2022), sweet potato tubers (Lezcano et al. 2015) and banana (García et al. 2020).
The highest pH value was showed in the moment of the micro-silos elaboration (day zero) and was slightly decreased in 0.74 units towards the first day the fermentation process have been start. Among the 4 and 30 evaluation days, the pH was established in values lower to 4, without significant differences among the mentioned days. The results of the pH analysis in the ripe guava fruit silage are shown in table 3.
Table 3 Performnace of the pH in the ripe guava fruit silage
| Silage days | SE ± | P value | ||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 4 | 8 | 15 | 30 | |||
| pH | 4.75a | 4.01b | 3.74c | 3.78c | 3.75c | 3.76c | 0.05 | < 0.0001 |
abc Different letters show differences at the level of p < 0.05 (Duncan 1955)
The highest pH values were showed in the 0 and 1 evaluation days. This is due to at the beginning of the fermentation process the lactic acid concentrations in the micro-silos are low or null because of the limited activity of the lactic acid bacteria (LAB).The changes in the pH are related with the amount of inoculum and soluble carbohydrates which are used in the silage formulation for the benefic microbial population reduce the pH efficiently, when increasing in the media the concentration of lactate and acetate (Ogiy et al. 2015 and Ogunade et al. 2018).
However to the previous, the pH was established between the 4 and 30 measurement days. This is satisfactory to achieve a good conservation of the product. Nkosi and Meeske (2010) show that the pH should stabilized in the first 96h of started the fermentation to reduce the concentrations of butyric acid and ammoniac nitrogen, as to achieve a good aerobic stability and restrict the developing of proteolytic enzymes, enterobacteria and clostridiums that damage the silage (Álvarez et al. 2015 and Da Silva et al. 2018).
The rapid pH stabilization is due to the lactic acid production because of the presence of Lactobacillus (Lopes et al. 2013).The inclusion of a carbon source (sugarcane molasses) of easily assimilation and the natural yogurt as inoculum source in the raw matter favors the growing of lactic bacteria and with this, the faster acidification of the medium (García et al. 2020 and Kim et al. 2021).This allow to reduce and stabilize the silage pH (Ossa et al. 2010 and Cárdenas et al. 2018) and keep the nutrients in the food. It is important to highlight that the faster stabilization inhibits the development of decomposing microorganisms that causes undesirable fermentations, deterioration of nutrients and silage quality (Borreani et al. 2017 and Ávila and Carvalho 2020).
Conclusions
The ripe guava fruit silage had good nutritional composition, so it constitutes an alternative food with appreciable nutritive characteristics for their use in pig diets under the Ecuadorian Amazonia conditions. The silage pH was showed constant in the first 96h of started the fermentation process, which is beneficial to avoid undesirable fermentations and achieve good aerobic stability and food conservation for a long time.
