INTRODUCTION
Pig is an important component of many of the traditional diets because almost all parts of the pig can be consumed. It contributes to human nutrition because pork consumption has several benefits. For example, it constitutes a valuable source of proteins and essential amino acids that humans have to obtain from external sources, since they cannot synthesize them. In addition, intramuscular or subcutaneous pig fat constitutes a valuable energy source (FAO 2018).
One of the biggest problems faced by pig rearing is related to production cost, since it is based on cereals and soybean, causing the small producer not to obtain an economic return for raising the animals. In this context, it is necessary to look for alternative foods with good nutritional content, and that do not directly compete with those for humans (Caicedo et al. 2015).
In Pastaza province, in the Ecuadorian Amazon Region (EAR), there is a great availability of alternative foods, among which taro tubers stand out, with a cultivation area of 200 hectares and an average yield of 38 t/ha. Out of these, 80% is used for the export market and domestic consumption, while the remaining 20% are by-products of tubers that do not meet the standards of form and size established by the market for human consumption (GADPP 2014).
These tubers have a good nutrient content and have lower cost than cereals (Caicedo et al. 2015). However, in their natural state, they have a high content of humidity and secondary metabolites, so it is necessary to perform drying processes for the preparation of meals and, in this way, obtain improvements in the use of these nutrients for pig fattening (Sánchez et al. 2018).
The several parts that compose the GIT of pigs are specialized to perform different functions, which are ingestion, digestion, absorption and excretion of food. Some reports state that pigs that have alternative diets suffer changes of the gastrointestinal tract (Savón et al. 2008 and Ly et al. 2014). In this sense, it is necessary to carry out morphometric evaluations of the GIT of these animals, to study the digestion pattern of these foods. Other studies report that the intake of alternative foods stimulates the pancreas to secrete digestive juice, pepsin production in the stomach and bile secretion in the liver, so these physiological aspects could cause morphometric changes with a greater development of these organs (Mejía 2017).
The objective of this study was to evaluate the effect of taro (Colocasia esculenta (L.) Schott) meal on the productive performance and morphometry of the gastrointestinal tract (GIT) of fattening pigs.
MATERIALS AND METHODS
Location. This study was carried out in the Programa de Porcinos del Centro de Investigación, Posgrado y Conservación Amazónica (CIPCA) of the Universidad Estatal Amazónica (UEA). CIPCA is located in the Ecuadorian Amazon Region (EAR), between Pastaza and Napo provinces. This area has a semi-warm or humid subtropical climate, with precipitations ranging between 4,000 and 5,000 mm per year. It is located at an altitude of 584 meters above sea level, with relative humidity of 87% and average minimum and maximum temperature of 18 to 36 ºC (Uvidia et al. 2014).
Preparation of taro meal. Taro tubers were acquired in Teniente Hugo Ortiz parish and did not meet the size, shape, or weight requirements for sale in the market for human consumption. Subsequently, they were transferred to CIPCA and then washed for 30 minutes in a 3 % solution of hypochlorite in the water, cleaned and drained. Later, they were placed under cover for 2 h and cut into slices. Pre-drying was carried out under plastic cover for 8 h and after that, they were dried in an industrial rotary dryer (Burmester brand) at 70 ° C for two hours. Finally, it was milled in a semi-industrial mill (TRAPS brand, TRF 300G model) with a mesh of 0.25 mm, packed in hermetic bags and stored for 10 days before use.
Management of animals and facilities. Animals were managed according to the guidelines of Bienestar Animal de la República de Ecuador (AGROCALIDAD 2017) and the experimental protocol according to Sakomura and Rostagno (2007). For this study, 16 castrated male animals, resulting from an criss crossing of Largewhite x Duroc x Pietrain were used, with an initial liveweight of 69 kg, distributed into two groups of eight pigs each, and every pig was considered as an experimental unit. Animals were housed in individual metal cages of 1.80 m x 0.60 m (1.08 m2) for 33 days (five of adaptation to diets and 28 in experimentation). Each pen was provided with a hopper feeder and a nipple drinker water troughs, located in a barn with walls of 1.2 m high and concrete floor. Water was available at will and mean room temperature in the unit was 25 ° C.
Food management. Treatments consisted of two diets: a control diet T0 (corn and protein concentrate for pigs) and T40 (substitution of corn for 40 % of taro tuber meal). Diets were formulated according to NRC (2012) for fattening pigs (table 1). Intake was adjusted according to the liveweight of animals (Rostagno et al. 2011). Food was provided twice a day, at 8:00 am and 3:00 pm, divided into two equal parts.
Ingredients, % | Levels of substitution of corn for taro tuber meal, % | |
---|---|---|
0 | 40 | |
Yellow corn | 63 | 23 |
Wheat meal | 9.0 | 9.0 |
Taro tuber meal | - | 40 |
Protein concentrate for pigs | 27 | 27 |
Mineral premix for pigs1 | 0.5 | 0.5 |
Sodium chloride | 0.5 | 0.5 |
Calculated nutrients | ||
ME, kJ g MS-1 | 13.71 | 13.12 |
CP, % | 15.84 | 15.79 |
CF, % | 3.23 | 3.70 |
Cost, dollars kg DM-1 | 0.60 | 0.50 |
1Premix of vitamins and minerals for finishing pigs (Vit A, 2,666,660 UI; Vit D3, 533,300 UI; Vit E, 4,667 UI; Vit K3, 1,200 mg; Vit B1, 200 mg; Vit B2, 13,336 mg; Vit B6, 133 mg; Vit B12, 6.667 μg; Folic acid, 34 mg; Niacin, 10.000 mg; Pantothenic, 666.666 mg; Biotin, 20 mg; Choline, 62 g; Iron, 40 mg; Copper, 86.805 mg; Cobalt, 334 mg; Manganese, 30,000 mg; Zinc, 46,666 mg; Selenium, 67 mg; Iodine, 400 mg; Antioxidant, 40 g; Vehicle qsp, 1,000 g); 2BHT; 3Calculation based on NRC (2012). Source: created by the authors
Productive indicators. After being selected for the experiment, pigs were dewormed with Fenbendazole at a rate of 10 g 100 kg LW-1. Animals were individually weighed every 14 days on a 200 kg capacity Cardinal scale. Productive performance indicators under study were daily food intake (DFI), daily weight gain (DWG), food conversion (FC) and final weight (FW) according to Lezcano et al. (2014), and carcass yield (CY) and back fat (BF) regarding Paredes et al. (2017).
Morphometric evaluations of the GIT and accessory organs. At the end of the 28-day experimental period, animals were fasted for 8 h and weighed later. Subsequently, they were sacrificed with the use of an electric stunner and bleeding by cardiac puncture (Ly et al. 2013). For the collection of intestinal samples, the abdomen was immediately opened from the sternum to the pubis and the complete GIT was exposed (Hou et al. 2010).
The GIT was divided into stomach, small intestine, large intestine and caecum. The organs were isolated and emptied (Grecco et al. 2018). The digestive contents of different sections of the GIT were not taken into account. Weights were recorded on a Camry scale with an accuracy of ± 1 g and measured with a tape measure with a fidelity of 1 cm (Ayala et al. 2014). In addition, liver weight was recorded and means of weights and lengths were analyzed as relative weight to the liveweight.
Statistical analysis and experimental design. The experiment was managed according to a completely randomized design. The analysis of variance was carried out according to recommendations of Steel et al. (1997). In the cases in which significant differences (P<0.05) were found, means were contrasted by Fisher (1954) test. Analyzes were conducted with the application of the statistical program Infostat (Di Rienzo et al. 2012).
RESULTS
Productive indicators. No differences (P> 0.05) were found among treatments for the productive indicators under study: DFI, DWG, FC, FW, CY and DF (table 2).
Variables | Levels of substitution of corn for taro tuber meal, % | SE± | P value | |
---|---|---|---|---|
0 | 40 | |||
Initial weight (kg) | 69.00 | 69.00 | 0.70 | P=0.9999 |
DFI (kg) | 2.96 | 2.95 | 0.01 | P=0.6985 |
DWG (kg pig-1 day-1) | 0.98 | 0.98 | 0.02 | P=0.9999 |
FC (kg kg-1) | 3.01 | 3.00 | 0.05 | P=0.9475 |
FW (kg) | 96.50 | 96.00 | 0.43 | P=0.8699 |
CY (kg) | 81.06 | 80.81 | 0.72 | P=0.8323 |
DF (mm) | 21.05 | 22.5 | 0.01 | P=0.5572 |
DFI (daily food intake), DWG (daily weight gain), FC (food conversion), FW (final weight), CY (carcass yield), DF (dorsal fat), SE (standard error).
Morphometric indicators. Table 3 shows the relative weight of GIT and accessory organs of fattened pigs fed with taro tuber meal, expressed in g kg-1 of body weight. There were no differences (P> 0.05) for the weight of the GIT, stomach, small intestine, large intestine, caecum and liver.
Variables | Levels of substitution of corn for taro tuber meal, % | SE± | P value | |
---|---|---|---|---|
0 | 40 | |||
Body weight, kg | 96.00 | 95.50 | 0.61 | P=0.9481 |
GIT | 53.13 | 52.18 | 0.25 | P=0.6140 |
Stomach | 9.49 | 9.09 | 0.28 | P=0.4226 |
Small intestine | 20.00 | 20.09 | 0.64 | P=0.4324 |
Large intestine | 23.64 | 23.00 | 0.57 | P=0.4216 |
Caecum | 3.64 | 3.64 | 0.01 | P=0.9999 |
Liver | 31.37 | 30.91 | 0.36 | P=0.4223 |
GIT (gastrointestinal tract), SE (standard error)
+Weight of empty and fresh organs
Table 4 shows the longitudinal measurements of digestive organs in cm kg-1 of body weight of fattening pigs fed with taro tuber meal. There was no effect (P> 0.05) among treatments for the elongation of the GIT, small intestine, large intestine and caecum of animals.
Variables | Levels of substitution of corn for taro tuber meal, % | SE± | P value | |
---|---|---|---|---|
0 | 40 | |||
Body weight, kg | 96.00 | 95.50 | 0.61 | P=0.9481 |
GIT+ | 41.21 | 42.49 | 0.47 | P=0.7487 |
Small intestine | 31.21 | 32.50 | 0.58 | P=0.6231 |
Large intestine | 10.00 | 10.00 | 0.51 | P=0.9973 |
Caecum | 0.70 | 0.71 | 0.40 | P=0.8459 |
GIT (gastrointestinal tract), SE (standard error)
+ From duodenum to rectum
DISCUSSION
Productive indicators. The optimum productive performance is due to the adequate content of nutrients of easy assimilation that taro meal has for pig feeding (Aragadvay et al. 2016). This fact was confirmed by Caicedo et al. (2018), who conducted studies of apparent digestibility of dry matter, organic matter, crude protein, crude fiber and crude energy in fattening pigs, and demonstrated that the substitution of 20 and 40% of corn for taro meal in the diet did not affect the use of nutrients in relation to the basal diet of corn and soybeans.
Starch from taro tubers is very small, 6.50 μm for white varieties and 6.60 μm for purple varieties (Torres et al. 2013), compared to other roots and tubers (Xanthosoma yucatanensis 12.40 μm, Ipomoea batata 12.41 μm, Manihot esculenta Crantz 16.5 μm and Marantha arundinacea 10.64 μm, Hernández-Medina et al. 2008), which facilitates the utilization of starch (Lapis et al. 2017). Likewise, taro meal has a low fiber content and does not affect digestibility of energy and protein in diets (Bertechini 2013).
In other researches, Naskar et al. (2008) with meal from boiled sweet potato tubers achieved increases in the rate of growth and food conversion of pigs by replacing the commercial diet by 40% of this food. Koslowski et al. (2017), with cassava meal, observed a decrease of food intake, weight gain and food conversion by completely substituting corn in the diet of growing pigs, and recommended replacing up to 66% without compromising the DFI, DWG and FC. With cassava bran, Romero de Armas et al. (2017) partially replaced corn in the diet at 30% without negative effect on the productive indicators of fattening pigs.
In summary, Ly (2010) and Sánchez et al. (2018) stated that roots and tubers processed in the form of meal constitute a valuable energy source for swine feeding at a lower cost in relation to cereals.
Morphometric evaluations of the GIT and accessory organs. There was no affectation for the weight of the GIT, stomach, small intestine, large intestine, caecum and liver, nor for the elongation of the TGI, small intestine, large intestine and caecum of the animals under study. Several reports indicate that the processing of food in the form of meal allows well-balanced diets that do not negatively influence on the morphology and function of the organs of the TGI, nor affect the productive performance of pigs (Landgraf et al. 2006, Bach-Knudsen et al. 2012, Diba et al. 2014 and Lindberg 2014). In this study, this effect is attributed to the low fiber level of the diets used (Hurtado et al. 2011 and Aguilar 2017).
Finally, there is enough experimental evidence to ensure that the increase in weight and elongation of digestive organs of pig are influenced by the genotype (McKay et al. 1984) and with the increase in the fiber level in the diet (Borin 2005, Ly et al. 2011 and Agyekum and Nyachoti 2017).
Under the conditions of this study, the use of taro tuber meal as a partial substitution of corn in the diet is feasible, since it does not have a negative influence on the indicators of productive performance or on the morphometry of the gastrointestinal organs of fattening pigs.