Diagnosis of the palatability of fruits of three fodder trees in ruminants

Diagnóstico de la palatabilidad del fruto de tres árboles forrajeros en rumiantes

Saúl Rojas-Hernández¹, Jaime Olivares-Pérez*¹, Fredy Quiroz-Cardoso^1, Abel Villa-Mancera², Moisés Cipriano Salazar¹, Luis Miguel Camacho Díaz¹, Alejandro Reynoso Palomar²

¹ Unidad Académica de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Guerrero, km. 3.0 Carretera Ciudad Altamirano-lguala, Col. Querenditas, CP. 40660, Municipio de Pungarabato Guerrero, México. * Corresponding author: olivaares@hotmail.com

Note received September 9, 2014,
Accepted may 11, 2015

ABSTRACT

The chemical composition, in vitro dry matter (IVDMD) and organic matter (IVOMD) digestibility of the fruits of Pithecellobium dulce, Acacia farnesiana and Acacia cochliacantha were determined. A cafeteria test in calves, sheep and goats was developed to determine through consumption of dry matter and coefficient of preference the palatability of these fruits as a feed source. Crude protein and neutral and acid detergent fiber contents were higher in the A. cochliacantha fruit (p < 0.001) with 11.1, 55.0 and 38.3 %, respectively. Total phenols were higher (p < 0.001) in A. farnesiana fruit with 39.7 %. The IVDMD and IVOMD were greater (p < 0.001) in P. dulce fruit with 57.7 and 35.6 %, respectively. The P. dulce fruit was more palatable (p < 0.0001) for calves and those of A. cochliacanta for sheep and goats (p < 0.05). It is concluded that palatability was higher for A. cochliacanta and P. dulce fruits due to their chemical composition.

Keywords: Palatability, fruits, trees, ruminants.

RESUMEN

Palabras clave: Palatabilidad, frutos, árboles, rumiantes.

INTRODUCTION

Fodder trees have been recognized in many parts of Mexico as a strategic biomass resource for livestock, which can help meet animal feed requirements in critical periods (Olivares et ai 2013a), without diminishing nutrient intake (Seresinhe et ai 2012). The selecting of feed by animals depends on its palatability, which is a complex phenomenon that is determined by factors inherent to the animal as well as to feed properties. The preference tests developed by Mokoboki et ai (2011) have demonstrated the usefulness of conducting cafeteria tests in ruminants for determining differences in palatability of feed obtained from trees. In the Mexican tropics, Pithecellobium dulce, Acacia farnesiana and Acacia cochliacantha trees are found scattered in pastures and in living fences where ruminants harvest the fruit to feed themselves in the dry season according to the animal's ability (Olivares et al. 2011). The objective was to determine the chemical composition and digestibility of the fruits of P. dulce, A. cochliacantha and A. farnesiana, as well as the preference that ruminants have for them as an indicator of their palatability, in order to provide additional important information regarding ruminant nutrition.

MATERIALS AND METHODS

The study was performed in the Tierra Caliente region of Guerrero, located at 18° 20' 30" north latitude, and 100° 39' 18" west longitude. The climate is AwO, the driest of the warm subhumid area with summer rains. The average temperature and rainfall are 28 °C and 1010.7 mm, respectively (Fragoso 1990).

Chemical composition and in vitro digestibility of fruits

Three samples of 500 g of ripe fruit from each tree were collected, dried at 40 °C for 72 h to constant weight, ground with a Willey mill with a 1 mm sieve and used for chemical composition analysis. Samples were analyzed for dry matter (DM) by drying at 105 C° for 24 h in a forced air oven (AOAC 2000; ID 954.01). Ash (AOAC 2000) and crude protein (CP) were determined by the Kjeldahl method (AOAC 2000; ID 954.01). Acid detergent fiber (ADF), neutral detergent fiber (NDF) (Van Soest et al. 1991), total phenol content (TP) (Folin ciocalteu) and condensed tannins (CT) (butanol-HCL) were determined using the methodology described by Waterman and Mole (1994).

Cafeteria test

The fruits of P. dulce, A. farnesiana and A. cochliacantha, trees native to Mexico and reportedly more abundant in the country's tropical regions than anywhere else, were used (Olivares et al. 2011). The fruits were crushed to two cm particle size for feeding. The animals used were four cross male calves Bos taurus / Bos indicus with live weight of 170.0 ± 15.0 kg; eight male sheep hybrid Dorper-Pelibuey of 18.5 ± 1.5 kg live weight and eight entire creole male goats of 20.6 ± 1.8 kg live weight, housed in individual pens with free access to food and water bowls. At the beginning of the experiment the animals were dewormed with albendazole sulfoxide (4.5 mg kg^-1 BW^-1 oral route) and were given vitamins A, D and E.

Bovines

Four calves housed in individual 2 x 4 m pens were used. The treatments were the fruits of the trees P. dulce and A. cochliacantha. Four kg DM animal^-1 d-^-1 of each fruit were offered for two hours a day before going to pasture (7:00 to 9:00 h) in individual feeders with daily rotation, to avoid the conditioning of animals. The study lasted fifteen days, comprising eight days for adaptation and seven for evaluation.

Sheep and Goats

Eight sheep and goats were housed in individual 1 x 1.2 m pens. The treatments were the fruits of the trees A. cochliacantha and A. farnesiana. 500 g DM animal^-1 d^-1 of each fruit in individual troughs were offered daily with rotation to avoid the conditioning of animals. Also, oat hay as basal diet was provided as an additional fodder. The study lasted twenty-five days, 10 d for adaptation plus fifteen for evaluation.

Variables measured

Palatability was determined by the animals' dry matter intake (DMI), subtracting the amount of fruit rejected daily by the amount offered (Alonso et al. 2008, Alonso et al. 2009, Olivares et al. 2013b), and the coefficient of preference (COP) was calculated from the ratio between the intake of individual fruits divided by the average consumption of fruits (Olivares et al. 2013b).

Statistical analysis

The preference study data variables (DMI and COP) were analyzed in a completely randomized design with a factorial arrangement, using the statistical model: Y_ijk = μ + T_i + σ_ij + P_k + (TxP)_ik + ε_ijk; Where, Y_ijk is the response to the ith treatment in the jth measurement in the kth period; μ is the overall mean; T_i is the effect of ith treatment (two fruits); σ_ij is the error associated with the experimental unit in the ith treatment (four calves and eight sheep and goats; Pk is the period effect (seven days in calves and fifteen days in sheep and goats); (T x P)_ik is the interaction treatment*period; and ε_ijk is the error associated with periods. Comparison of means between treatments in the two designs was performed with the Tukey test (p < 0.05).

RESULTS AND DISCUSSION

Chemical composition

The content of CP, ADF, NDF and CT was higher (p < 0.001) in the fruit of A. cochliacantha with 14.5, 38.3, 55.0 and 4.6 %, respectively (Table 1). The total phenol content was higher in the fruit of A. farnesiana with 39.7 %. The fruit of P. dulce was the most digestible (p < 0.001) with 57.7 % in dry matter and 35.6 % in organic matter (Table 1).

In general, the protein content in the fruits of the three tree species was between 10.2 and 14.5 % on a dry matter basis, which covers the required minimum of 8.0 % to ensure the efficient functioning of the rumen micro flora (Van Soest 1994). On the other hand, ADF and NDF contents in the fruit of P. dulce (Table 1) is below that reported for fruits in other tree species (Guazuma ulmifolia, Crescentia alata, Acacia nilotica and Acacia sieberiana); however, the detergent fiber content of A. cochliacantha fruit is higher (Mlambo et al. 2011, Rojas-Hernandez et al. 2015). The highest ADF and NDF contents were found in the A. cochliacantha fruit, suggesting the presence of high concentrations of cellulose, hemicellulose and lignin, as described by Mlambo et al. (2011) and Olivares et al. (2013b), which decreased IVDMD and IVOMD in this fruit (Table 1).

Cafeteria test in ruminants

The calves' preference for the P. dulce fruit (Figure 1) was associated with higher in vitro dry and organic matter digestibility of this fruit (Table 1). The levels of ADF and NDF affect the digestibility of food and this can have an effect on dry matter intake by the animal (Gregorini et al. 2015). The rejection of A. cochliacantha fruit by calves could be related to the higher content of total phenols and condensed tannins (Table 1), compounds responsible for the astringency and decreased palatability (Patra and Sexena 2011).

Sheep: Sheep on the fifth day of the experiment consumed more (p < 0.05) A. cochliacanthawasfruit with 0.29 kg DM animal^-1 d^-1 and this level was maintained until the fifteenth day of the experiment with 0.42 kg DM animal^-1 d^-1 (Figure 2). In relation to consumption dynamics during the study period, it was observed that fruit intake by sheep increased significantly (p < 0.0001). In A. cochliacantha fruit, it increased from the first day with 0.17 kg DM animal^-1 d^-1 to 0.44, 0.45 and 0.42 kg DM animal^-1 d^-1 on the ninth, tenth and fifteenth day, respectively. In A. farnesiana fruit, consumption initiated with 0.15 kg animal^-1 d^-1 and peaked on the tenth day of consumption with 0.38 Kg DM animal^-1 d^-1 and ended with 0.32 Kg DM Animal^-1d^-1 (Figure 2). The COP of the sheep for A. cochliacantha fruit ranged between 1.04 to 1.16 units and was higher (p < 0.05, p < 0.01, p < 0.001) than the COP for A. farnesiana fruit (Figure 2). In relation to COP dynamics during the study period, it was observed that fruit intake by sheep by tree species did not differ (p > 0.05) (Figure 2). In sheep the higher intake and COP for A. cochliacantha fruit (Figure 2) are attributed to its high crude protein and low total phenol content, compared to the levels observed in A. farnesiana fruit (Table 1); this behavior was similar to that reported by Alonso et ai (2009) and Olivares et ai (2013b) in small ruminants.

Goats: In goats there were no differences (p > 0.05) in the consumption of fruits of A. cochliacantha (0.19 to 0.49 kg DM animal^-1d^-1) and A. farnesiana (0.18 to 0.45 kg DM animal^-1d^-1(Figure 3). In relation to consumption dynamics during the study period, it was observed that fruit intake by goats increased significanty (p< 0.0001). In A. cochliacantha fruit, it increased from 0.19 kg DM animal^-1 d^-1 on the first day to 0.44 to 0.49 kg DM animal^-1 d¹ between the ninth and fifteenth day. In A. farnesiana fruit, consumption started with 0.18 kg animal^-1 d^-1 and reached 0.39 to 0.45 kg DM animal^-1 d^-1 between the ninth and fifteenth day (Figure 3). The COP of the goats for A. cochliacantha fruit varied between 1.00 and 1.05 units and was higher (p < 0.05) than the COP they had for A. farnesiana fruit on the first day and between the ninth and fifteenth day only (Figure 3). In terms of COP dynamics during the study period, it was observed that fruit intake by goats by tree species did not differ (p > 0.05) (Figure 3). In goats the differences in the COP (Figure 3) may indicate their tendency to prefer A. cochliacantha fruit due to its protein and detergent fiber contents (Table 1), behavior similar to that reported by Alonso et al. (2008) and Olivares et al. (2013a). In goats the consumption of A. cochliacantha and A. farnesiana fruits was similar (Figure 3), which indicates their ability to adapt to eating foods with higher total phenol and condensed tannin contents and regulate their nutritional needs to the intake of diversified feeds (Torres et al. 2008, Olivares et al. 2013b).

It is important to analyze the CT and TP content of fruit (< 5 %) as it indicates its potential as feed for ruminants (Table 1); this is because reports indicate that such secondary compounds in higher amounts affect the rumen microbial population, inactivate enzymes in the rumen, precipitate proteins and carbohydrates from the diet and consequently cause poor digestion of feed, leading to increased nitrogen excretion in the feces (Patra and Saxena 2011, Lorentz et al. 2013, Hatew et al. 2014). They can also affect the health of the animal by causing hemolysis and increased methemoglobin in the blood, which can lead to the death of the animal (Mueller-Harvey 2010)

Variation among ruminants in dry matter intake of the fruits of different trees has demonstrated the usefulness of preference tests in ruminants for reporting differences in palatability of feed, where there are factors of interaction inherent to the animal and to the organoleptic properties of the feeds given to it due to their chemical compounds (Mokoboki et al. 2011, Olivares et al. 2013b).

It is concluded that the differences in the consumption of fruits and in the COP between ruminant animals were determined by the in vitro digestibility of DM and OM, as well as the content of CP, ADF, NDF and CT. The fruit of P. dulce was the most palatable for calves, whereas the fruit of A. cochliacantha was the most palatable for sheep and goats, which adapted to consuming fruit with higher levels of CT due to the physiological and chemical characteristics of their salivary secretions. The three fruits have potential as feed for ruminants in the tropics because of their low content (< 5.0 %) of secondary compounds (CT and TP) and a CP content greater than 8.0 %.

ACKNOWLEDGEMENTS

The authors thank SEMILLA-UAGro for funding this research project, which enabled the students involved to fulfill their degree requirements.

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