Coconut tree (Cocos nucifera L.), one of the trees of Arecaceae family, is probably one of the first plants domesticated by humans. Its culture is currently developed in various tropical regions (Johnson 1995 and Ly et al. 2005). The fruit of this palm, which is the coconut, originates different products that are often used in industry, or in human food and farm animals.
Although there is sufficient literature on the use of coconut tree products for feeding pigs (Ly et al. 2005 and Stein et al. 2015), its use in pig nutrition is still an important subject. There are several recent reports that deal with this matter (Février et al. 2001, Siebra et al. 2008, Sulabo et al, 2013, Jaworski et al., 2014 and Son et al. 2014). In Cuba, although there are coconut plantations in different parts of the archipelago (Pérez et al. 2001), coconut production is concentrated in Baracoa and Maisí municipalities, in Guantanamo province (Alvarado et al. 2013). Harvesting this fruit may generate different products, by-products or co-products that can be used for fattening pigs and which generally result from agreements established between pig farmers and Cuban state companies.
Although some evaluations have been carried out in Cuba about nutritional value of coconut endosperm in materials in the shape of meal (Ly et al. 1999 and Ly and Delgado 2009), it is unknown whether drying process could modify digestibility indexes because of undesirable reactions like those of Maillard. In addition, drying up increases the price of the process of using coconuts in pig feeding, and is not very common practice among Cuban farmers. The objective of this study was to present data related to the nutritional value of products from coconut endosperm, in natura, measured by in vitro digestibility technique simulating ileal digestion in pigs.
Dry coconuts were collected by acquiring fruits from local markets, from Artemisa, Mayabeque and Havana provinces, Cuba. Markets and fruits destined for human consumption were selected at random. Coconuts came from palm trees, grown in the provinces cited before. The cultivated variety was not identified. The endosperm of coconuts was separated from the fruit to constitute one sample per market and five markets were chosen per province, with the purpose of evaluating 15 samples in total. The endosperm was manually chopped and grated in natura, to make in vitro digestibility tests (pepsin/pancreatin) in quadruplicate, with the use of the technique recommended by Dierick et al. (1985). Half of that endosperm was used intact, and the other half was placed in a Soxhlet apparatus to be defatted with petroleum ether (fraction 40/60 °C). Analytical determinations of DM, ash and N were carried out according to recognized procedures (AOAC 2016). Organic matter was determined as the result of subtracting the ash percent from 100. Casein, with purity degree for analysis, was used as reference standard substance.
Data were processed according to a completely randomized design, in a 2x3 factorial arrangement, with five repetitions per origin (Steel et al. 1997). Factors were defatting or not the samples and the origin or province where the fruits were collected. Data was processed using the statistical package MINITAB (2014).
There was no significant interaction (P <0.05) among the analyzed factors. Defatting determined significant decrease or increase (P <0.05) in the concentration of organic matter or N (table 1), without effect of the place of origin. It was verified that N content was considerable in defatted endosperm, in agreement with data from other contemporary studies (Stein et al. 2015). In the coconut endosperms used by Sulabo et al. (2013) and Son et al. (2014), total N reached 3.79 and 3.60 % respectively, values that exceeded what was obtained in this study. This may be due to the fact that in the aforementioned research, fruits from trees grown under more favorable conditions than those from Cuba have been used.
Table 2 shows the values corresponding to in vitro determinations (pepsin/pancreatin) of the digestibility of coconut endosperm. The test with casein, incubated in the same experimental conditions, indicated digestibility values of DM, organic matter and N of 98.5, 99.0 and 97.1 %, respectively. There was no significant effect (P> 0.05) of defatting nor of the origin of the gathering in the in vitro digestibility of DM, organic matter and N, with mean values of 48.7, 44.5 and 57.7 %, respectively.
Results of in vitro tests of this study coincide with data of in vitro ileal digestibility reported by Ly et al. (1999). They suggest that there are no undesirable consequences in ileal digestibility of N due to the presence of the lipid fraction of coconut endosperm. They also indicate that fiber fraction of this endosperm could reduce N digestibility, under in vitro and in vivo conditions. This is due, among other reasons, to the fact that part of N is linked to fiber, as in the case of royal palm nuts (Ly et al. 2015).
In correspondence with the above, Sulabo et al. (2013) found that, under in vivo conditions, apparent ileal digestibility of N of copra meal (69.8 %) was lower than that of soybean meal, (80.9 %), which was attributed to the negative influence of NDF content of coconut endosperm in digestive processes, as reported by Février et al. (2001) and Son et al. (2014). The magnitude of this effect was not evaluated in this analysis. It is likely that the treatment with fibrolytic enzymes contributes to improve the nutritional value of this food resource, as Masey O'Neill et al. (2014). Even so, in vitro ileal digestibility indexes of coconut endosperm are not insignificant in absolute values and their use in pig feeding is recommended, as indicated by Stein et al. (2015).
It is concluded that coconut endosperm, provided to pigs in ground shape and in natura, may considerably useful as an energy and protein source, due to its ileal digestibility.