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Introduction
There are precedents suggesting that albizia (Albizia lebbeck (L.) Benth.) foliage has a nutritional value that could be considered as an alternative for application in animal production (Hassan et al., 2007; Chitra & Balasubramanian, 2016; Ly et al., 2018). In the type of livestock farming in places with a forestry component with the use of cutting and hauling, swine raising can be included (Botero, 2004; Leterme et al., 2006). The use of trees as sources of forage with considerable protein content is a suitable option for swine feed since tropical trees are locally available and there is no need to plant them more than once after harvest. Although fibrous components are present in most ingredients for monogastric animals, its concentration in swine diets has increased proportionally with the incorporation of by-product or forage-type feeds (Ly & Pok, 2014; Jha et al., 2019). The degree of acceptance of this type of alternative ingredients depends on several factors, such as fiber content, degree of microbial fermentation in the large intestine, and the degree of absorption and utilization of the volatile fatty acids produced (Jha & Berroscoso, 2015). Recent evidence shows that foliage has benefits when fed as ad libitum diets to young animals fed sugarcane molasses (Mireles et al., 2020). As these kinds of honey or molasses do not contain fiber, Preston & Murgueitio (1992) have suggested taking advantage of this fact using locally available feed resources in such integrated swine production systems, which can be fed to animals as fibrous sources of protein, an example of which may be albizia foliage meal.
In a first approach, feed intake pattern indices in growing swine-fed sugarcane molasses and albizia foliage meal diets, were evaluated (Mireles et al., 2020). However, it is necessary to evaluate their digestive utilization especially in fibrous protein sources, which could be a limitation in growing pigs related to the fibrous components (Ly et al., 2016). In this sense, nutrient digestibility varies by fiber level and type, as well as its water holding capacity (Bindelle et al., 2008). Previous reports suggest that nutrient digestibility in pigs can be affected by diets rich in fiber. Therefore, several mechanisms have been proposed to explain the negative impact that dietary fiber might have on nutrient digestion. In this regard, it has been reported that soluble fiber increases gut digesta viscosity, which leads to a reduction in nutrient digestion. On the other hand, insoluble fiber increases peristaltic action, which reduces digesta transit time and less mixing time for digestive enzymes and diet components (Agyekum & Nyachoti, 2017). However, Urriola & Stein (2010) tested diets rich in insoluble fiber from dried distillers dried grains, with no effect on digesta transit time. This suggests that effects of dietary fiber on digestion and nutrient absorption may be highly influenced by the physicochemical properties of the fiber (Wenk, 2001). The present experiment aimed to determine total tract digestibility (TTD) rates of nutrients, as well as fecal output of materials, in growing pigs fed ad libitum on sugarcane molasses diets formulated to contain variable levels of albizia foliage meal as a fibrous source of protein.
Material and Methods
A total of 32 castrated male Yorkshire x Landrace x Duroc pigs weighing 30 kg distributed completely at random in four treatments consisting of B-type sugarcane molasses/soybean flour diets (67.6/30.4, dry basis), in which 0, 5, 10 and 15 % were substituted by albizia (Albizia lebbeck (L.) Benth.) foliage meals were used.
The albizia foliage was sourced from an uncultivated plantation located in the northwest of Havana province, Cuba. This foliage was obtained from terminal branches of young trees (5 years old). The foliage meal was elaborated after sun-drying the material for a period of 5 days and then it was triturated in a hammer mill equipped with a 1µ sieve. This meal had an average content of 20.0 and 35.0 % crude protein and crude fiber, on a dry basis, respectively. The characteristics of the diets are shown in Table 1.
Table 1 Composition of diets with inclusion of albizia (Albizia lebbekc (L.) Benth) for growing pigs (per cent on a dry basis).
| Albizia foliage meal, % | ||||
|---|---|---|---|---|
| - | 5 | 10 | 15 | |
| Ingredients | ||||
| Sugar cane molasses type B | 67.60 | 64.22 | 60.84 | 57.46 |
| Soybean meal | 30.40 | 28.88 | 27.36 | 25.84 |
| Albizia foliage meal | - | 5.00 | 10.00 | 15.00 |
| CaPO4H.2H2O | 0.50 | 0.48 | 0.45 | 0.42 |
| NaCl | 0.50 | 0.48 | 0.45 | 0.42 |
| Vitamins and minerals1 | 1,00 | 0.94 | 0.90 | 0.86 |
| Analysis | ||||
| DM | 85.50 | 85.85 | 86.19 | 86.53 |
| Ash | 4.65 | 4.87 | 5.10 | 5.32 |
| Organic matter | 95.35 | 95.13 | 94.90 | 94.68 |
| Crude fibre | 2.26 | 3.66 | 5.04 | 6.44 |
| ADF | 2.11 | 3.62 | 5.11 | 6.61 |
| NDF | 2.83 | 4.85 | 7.07 | 9.19 |
| Crude protein (Nx6.25) | 16.20 | 17.13 | 17.55 | 17.98 |
| Gross energy, kJoule/g DM | 16.50 | 16.49 | 16.48 | 16.48 |
| Water retention, g/g DM2 | 1.55 | 1.67 | 1.80 | 1.92 |
1 Contenido (per kg): vitamina A, 600 UI; vitamina D3, 160 UI; vitamina E, 10 mg; vitamina B1, 2 mg; vitamina B2, 3 mg; vitamina B6, 15 mg; vitamina B12, 0.025 mg; ácido pantoténico, 5 mg; cloruro de colina, 300 mg; bisulfato sódico de menadiona, 2 mg; ácido fólico, 0.5 mg; cobalto, 0.4 mg; hierro, 10 mg; yodo, 0.5 mg.
2 Determined by centrifugation (Kyriazakis & Emmans, 1999).
The total tract digestibility assay was conducted by broadly following the methodology recommended by Adeola (2001). During first week, individuals were dewormed and gradually switched from a conventional cornmeal/soybean meal diet to the molasses B/soybean meal diet. By third week, pigs were about 30 kg, and at the beginning of the third week, they were completely randomized to one of four diets containing albizia foliage meal (0, 5, 10 and 15 %, dry basis). On seventh day of third week, rectal sampling was performed at 9:00 am to determine fecal output of materials and in vivo TTD through an indirect nutrient method. During these events, feed distribution was always ad libitum.
Dry matter (DM) and ash content were determined in representative samples of fresh feed and excreta (AOAC, 2007), and in ash, acid insoluble ash by digestion in 4 N HCl with subsequent gravimetric quantification of insoluble residues (Van Keulen & Young, 1977). The N concentration was also measured in fresh material by the macro Kjeldahl method (AOAC, 2007). The rest of the samples were dried in an oven at 60 °C with air circulation and then milled in a hammer mill equipped with a 1 mm sieve. Crude fiber content of this meal was quantified according to AOAC (2007) recommendations. ADF and NDF were determined by digestion of dry samples in detergent solutions (Van Soest et al., 1991). Sample calorific content was established using an adiabatic calorimetric bomb and water retention capacity of the albizia meal and diets, according to Kyriazakis & Emmans (1999) by weighing the dry residue of material previously suspended in water, kept rest at room temperature (25 °C), and centrifuged at low speed. All fecal output data were calculated according to Ly et al. (1998), while the equation suggested by Crampton and Harris (1969) was used for TTD. Data were processed through the statistical package Minitab (2014), under a one-way variance analysis (Aaron & Hays, 2001). Tukey's range test was used when the analysis of variance revealed significant differences (p < 0.05) between treatments.
Results and Discussion
Fecal output of materials
Data on fecal indices and fecal output of materials are listed in Table 2. DM concentration in fecal material decreased (p = 0.001) as well as fecal pH, with increasing foliage meal in the diet. Data suggest that alterations in the fermentation pattern of food residues arriving in the large intestine of pigs fed tree foliage, in correspondence with the presence of other substrates for residing intestinal microflora (Lowell et al., 2015; Liu et al., 2016).
Table 2 Fecal output materials in growing pigs fed ad libitum with albizia (Albizia lebbeck (L.) Benth foliage meal diets
| Albizia foliage meal, % | EE ± | P | ||||
|---|---|---|---|---|---|---|
| - | 5 | 10 | 15 | |||
| n | 8 | 8 | 8 | 8 | - | - |
| Fecal indices | ||||||
| DM, % | 35.00a | 34.12a | 32.12b | 31.82b | 0.77 | 0.001 |
| pH | 6.81a | 6.68ab | 6.60b | 6.43c | 0.09 | 0.001 |
| Fecal output, g/kg intake DM | ||||||
| Fresh material | 380.8a | 447.0ab | 545.8bc | 650.2c | 72.8 | 0.001 |
| Dry material | 134.8a | 160.0ab | 175.1bc | 198.2c | 20.9 | 0.001 |
| Water | 246.0a | 257.0ab | 370.7bc | 452.0c | 52.8 | 0.001 |
abcd Means without a letter in common in the same row are statistically different (p < 0.05) there between.
Output of fresh and dry material, as well as water in excreta, significantly increased (p = 0.001) as raising the level of foliage in the feed. It is known that the inclusion of feed resources in diets determines an increase in fecal volume emitted by pigs (Vu et al., 2009). This phenomenon also occurs with sugar cane molasses, so it is necessary to know its magnitude to establish an adequate balance of materials in integrated animal production systems (Preston & Murgueitio, 1992).
Total tract digestibility of nutrients in the diets.
Nutrient digestibility of the treatment without albizia foliage was high (Table 3), typical of a type B molasses diet, with a remarkable sucrose content. On the other hand, with the inclusion of this tree foliage in the molasses diet, a significant decrease (p = 0.001) in the TTD of DM, organic matter and energy was observed. Such decrease was also observed in the TTD of crude fiber and ADF, but the opposite effect occurred with NDF (p = 0.001). On the other hand, TTD of N also decreased from 86.6 to 84.0 % (p = 0.008) in the diet containing 0 and 15 % albizia foliage meal.7
Table 3 Total tract digestibility in growing pigs fed ad libitum with albizia (Albizia lebbeck (L.) Benth.) foliage meal diets
| Albizia foliage meal, % | EE ± | P | ||||
|---|---|---|---|---|---|---|
| - | 5 | 10 | 15 | |||
| n | 8 | 8 | 8 | 8 | - | - |
| Digestibility, % | - | - | ||||
| Dry matter | 86.6a | 84.9ab | 82.5bc | 80.2c | 2.0 | 0.001 |
| Organic matter | 87.4a | 85.9a | 82.7b | 80.5b | 2.2 | 0.001 |
| Crude fibre | 40.1a | 38.2ab | 36.1b | 31.5c | 1.6 | 0.*** |
| ADF | 40.5a | 38.7ab | 36.3b | 31.0c | 1.5 | 0.001 |
| NDF | 54.0a | 58.7ab | 64.6ab | 66.0b | 6.0 | 0.001 |
| Protein | 86.6a | .85.5ab | 84.6ab | 84.0b | 1.4 | 0.008 |
| Energy | 84.9a | 83.1a | 82.1a | 77.5b | 2.8 | 0.001 |
abcd Means without letter in common in the same row are significantly (p < 0.05) different among them.
At first, it could be argued that the decrease in TTD of albizia diets can be attributed to its fiber content. As is well known, an increase in the level of dietary fiber has a negative impact on the nutritive content (Jha & Berrocoso, 2015). However, the decrease in TTD was not as high as observed in other experiments where fibrous feed resources have been incorporated in swine diets. This could be attributable to the nature of the fibrous fraction contained in the albizia foliage, in which the leaves were relatively young, non-lignified terminal branches.
Total tract digestibility of nutrients in albizia foliage meal.
Table 4 lists TTD data of nutrients and energy of albizia foliage meal per se, calculated by difference. The TTD of protein and foliage energy were high at 71.7 and 57.6 %, respectively. A considerable variation in all the evaluated parameters was observed, and, as might be expected, no significant differences (p > 0.05) between treatments were found.
When using albizia foliage for pigs, there is very little information available with which to discern which factors are relevant and should be considered in terms of the nutritive value of this tree foliage (Kambashi et al., 2014). In advance, at least it has been shown that the nutritive value of albizia foliage meal, determined under in vitro conditions, was higher in young foliage material, similar to that used in this experimental work (Ly et al., 2018), compared to aged tree material. Furthermore, animals used in the present experiment were fed under ad libitum conditions, as it is known that, at a higher level of feed intake, digestibility seems to decrease (Roth & Kirchgessner, 1984), given a shorter digesta retention time in the cecum and colon (Liu et al., 2016). Age or body weight parameters also seems to affect pigs, since the same diet fed to young pigs, leads to a lower nutrient digestibility when this index is compared to older animals (Lowell et al., 2015). Nevertheless, it remains likely there is no decisive drawback of the age or body weight of the individuals in the digestive use of diets with low levels of albizia foliage meal in diets fed to growing pigs of the kind used in the present investigation. It is possible that the adaptation time could influence the determination of TTD in animals (Huang et al., 2018). This could be associated with phytochemical advantages inherent to albizia (Hassan et al., 2007; Mishra et al., 2010).
Obtained data corresponding to DTT of nutrients and energy of the albizia foliage meal are shown in Table 4. Such DTT calculation was determined by difference (Crampton & Harris, 1969) and had no significant effect (p > 0.05) among the three treatments containing the albizia meal evaluated, thus the average value of said three treatments was calculated.
Table 4 Total tract digestibility of nutrients and energy of albizia (Albizia lebbeck (L.) Benth.) foliage meal for pigs calculated by difference
| Albizia foliage meal, % | EE ± | P | ||||
|---|---|---|---|---|---|---|
| Digestibility % | - | 5 | 10 | 15 | ||
| n | 8 | 8 | 8 | - | - | - |
| DM | 44.9 | 49.8 | 45.7 | 39.3 | 29.2 | 0.775 |
| Organic matter | 48.7 | 65.5 | 39.3 | 41.3 | 26.8 | 0.227 |
| NDF | 15.6 | 14.8 | 16.0 | 15.9 | 2.9 | 0.680 |
| Protein | 71.7 | 72.0 | 71.2 | 72.0 | 21.9 | 0.997 |
| Energy | 57.6 | 58.0 | 57.3 | 48.6 | 33.8 | 0.795 |
In the present study, as usual, a high similarity (R2 < 0.9) was found between the TTD percentage of DM, organic matter and energy (44.9, 48.7 and 57.8 %). On the other hand, either low or high values (15.6 and 71.7 %, respectively) noted in the TTD of cell wall and N, showed no evident correlation between said parameters (p > 0.05).
It is suggested that consumption of up to 15 % albizia foliage meal in the diet fed ad libitum to young pigs may result in measurable changes in DTT indexes when fed to animals fed type B sugarcane molasses diets. It remains possible that the nutritional value of albizia foliage may be enhanced by the addition of fibrolytic or other substances with a similar purpose, or by feeding animals with adequate body weight, such as gilts or pregnant sows, which would be worth investigating. There is still a need of determining whether this status quo influences the behavioral traits of pigs.
Conclusions
It is suggested that TTD of DM, organic matter and N do not change its pattern in pigs fed diets where corn/soybean meal is partially excluded as conventional feed ingredients. In contrast, the digestive processes of degradability of the fibrous fractions of the diet, such as crude fiber, acid detergent fiber and neutral detergent fiber may undergo important modifications both qualitatively and quantitatively, probably in the large intestine of individuals. It is advisable to further investigate which factors have the most relevant influence on the nutritive value of the fibrous fractions of albizia foliage meal. It is also recommended to extend this type of research to the nutritional evaluation for pigs of shrub and tree foliage in general, and of albizia in particular.
