Profile of fatty acids of Longissimus dorsi muscle and productive indicators of sheeps, supplemented with pods of Acacia cochliacantha, in grasslands native to dry tropics

Perfil de ácidos grasos del Longissimus dorsi e indicadores productivos de corderos, suplementados con vainas de Acacia cochliacantha, en praderas nativas del trópico seco

E.J. Mireles,^I D. Rodríguez,^II H. Jordán,^II M. Valdivia,^III A. Ramírez,^IV A. García,^IV J. Olivares,^I

^IUnidad Académica de Medicina Veterinaria y Zootecnia de la Universidad Autónoma de Guerrero, México. km 2.5 Carretera Cd. Altamirano- Iguala Cd Altamirano Gro. CP 40660.
^IIInstituto de Ciencia Animal, Apartado Postal 24, San José de las Lajas, Mayabeque, Cuba. ]]> ^IIILaboratorio de Química y Análisis de Alimentos, Facultad de Química, Universidad Nacional Autónoma de México. Av. Universidad 3000, Coyoacán, Del Carmen, 04510 Ciudad de México, D.F., México.
^IVDepartamento de Nutrición Animal y Bioquímica, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México.

ABSTRACT

Daily weight gain, hot carcass yield and profile of fatty acids of Longissimus dorsi muscle were determined in 30 Pelibuey-Black Belly x Dorper-Katahdin lambs, with 20 ± 2 kg of liveweight, supplemented with ground pods of Acacia cochliacantha, in irrigated native grasslands. The animals were selected at random and three treatments were designed: 1) grazing and 0 % of supplementation, 2) grazing plus 15 % of supplementation, and 3) grazing plus 30 % of supplementation with Acacia cochliacantha, according to the dry matter requirements. The grasslands were composed by shrubs, grasses and herbaceous plants. Daily weight gain, hot carcass yield, weight of liver, kidneys and heart, perirenal and pericardial fat, and profile of fatty acids were determined. The analysis of variance was applied to the data. There were no significant differences in daily weight gain (68, 59 and 63 g), hot carcass yield (37.08, 37.84 and 39.09 %), weight of viscera and intramuscular fat (1.59, 1.84 and 1.72 %). There was a C18:2-n6/c18:3-n3 (omega 6/omega 3) relation of 3.53, 3.25 and 3.38 in the Longissimus dorsi muscle, for the 0, 15 and 30 % supplementation groups, respectively. The treatment with 30 % of supplementation had the lowest content (P<0.05) of C22:1n-9, regarding the control treatment. It can be concluded that lambs in irrigated native grasslands, with or without supplementation of pods of Acacia cochliacantha, produced acceptable hot carcass yield and daily weight gains, and a close relation of  C18:2-n6/c18:3-n3. There was only a decrease of erucic acid (C22:1n-9) in the Longissimus dorsi muscle of the supplemented animals.

Key words: ovine, daily weight gain, intramuscular fat, supplementation, Acacia cochliacantha.

RESUMEN

Se determinó la ganancia diaria de peso, el rendimiento de la canal caliente y el perfil de ácidos grasos del Longissimus dorsi de 30 corderos Pelibuey-Black Belly x Dorper-Katahdin, de 20 ± 2 kg de peso vivo, suplementados con vaina molida de Acacia cochliacantha, en pastoreo de praderas nativas irrigadas. Los animales se seleccionaron completamente al azar y se diseñaron tres tratamientos: 1) pastoreo y 0 % de suplementación; 2) pastoreo más 15 % suplementación; 3) pastoreo más 30 % de suplementación con Acacia cochliacantha, según los requerimientos de materia seca. Las praderas estuvieron compuestas por gramíneas, arbustivas y herbáceas. Se determinó la ganancia diaria de peso, el rendimiento en canal caliente, el peso del hígado, riñones, corazón, grasa pericárdica y perirenal y perfil de ácidos grasos. A los datos se les aplicó análisis de varianza. No hubo  diferencias significativas en la ganancia diaria de peso (68, 59 y 63 g), rendimiento en canal caliente (37.08, 37.84 y 39.09 %), peso de las vísceras y grasa intramuscular (1.59, 1.84 y 1.72 %). Hubo relación C18:2-n6/c18:3-n3 (omega 6/omega 3) de 3.53, 3.25 y 3.38 en el músculo  Longissimus dorsi, para  los grupos con 0, 15 y 30 % de suplementación, respectivamente. El tratamiento con 30 % de suplementación tuvo menor contenido (P < 0.05) de C22:1n-9, con respecto al tratamiento control. Se concluye que los corderos en praderas nativas irrigadas, con  suplementación de vaina Acacia cochliacantha o sin ella, produjeron ganancia diaria de peso y rendimientos en canal caliente aceptables y relación estrecha de C18:2-n6/c18:3-n3. Solo hubo disminución del ácido erúcico (C22:1n-9) en el Longissimus dorsi en los animales suplementados.

Palabras clave: ovinos, ganancia diaria de peso, grasa intramuscular, suplementación Acacia cochliacantha.

INTRODUCTION

Ovine meat production in Mexico is not enough to cover the demand of this product. Therefore, more than 40 % of the national consumption is imported (Martínez et al. 2009). Feeding based on forages generates a reduction of productive indexes, but at low costs compared to the intensive fattening based on grains and pastes of oleaginous plants, to obtain daily weight gains (DWG) of 250 g or more (Macedo and Castellanos 2004 and Macías et al. 2010). The meat of sheep fed with forages show less content of fat and a beneficial fatty acid profile for the health of consumers, regarding those fed with large amounts of grain in the ration (Velazco et al. 2004 and Nuernberg et al. 2008). Nowadays, it is important the production of hair sheep, with a great performance in systems of low inputs, based on forages of medium nutritional quality that produce small and lean carcasses, with different chemical composition, compared to the animals fattened with grain-rich diets (Johnson et al. 2010 and Turner et al. 2014).     

Lamb grazing in irrigated native grasslands and the physical control of weeds is an alternative for feeding lambs, together with the supplementation with shrub fruits. The objective of this study was to determine daily weight gain (DWG), carcass yield, weight of some viscera and perirenal and pericardial fat, and to perform a proximal chemical analysis and find the profile of fatty acids of the Longissimus dorsi muscle of sheeps in native grasslands, with irrigation and supplementation with ground pods of Acacia cochliacantha.

MATERIALS AND METHODS

This study was carried out from October, 2012 to January, 2013, at the Facultad de Medicina Veterinaria y Zootecnia from the Universidad Autónoma of Guerrero, located at km 2.5 de la carretera Altamirano- Iguala, Pungarabato municipality, Tierra Caliente region, Guerrero, Mexico. This area is located at 18º 20` 30” NL and 100º 39` 18” WL. The climate, according to a classification of Köopen, is subhumid warm AW0 type (INIA1982).

Animals. An amount of 30 Pelibuey-Black Belly x Dorper-Katahdin lambs were used, with 20 ± 2 kg of liveweight. They were wormed and injected intramuscularly with A, D, E vitamins before the beginning of the experimental period, and they were divided completely at random into three treatments: 1) 100 % gazing with 0 % of supplementation (control treatment), 2) grazing plus 15 % of supplementation, and 3) grazing plus 30 % of supplementation (30 % treatment). The ground pods of Acacia cochliacantha were used as supplementation, with 102 g and 205 g, respectively. Table 1 shows the chemical composition of the diets.

Grazing. Six mixed native grasslands were used, with 20 x 40 m, with rotational grazing of five days per 30 d of recovery, with irrigation every seven days and annual application of ovine manure (10 t ha^-1 año^-1) during the dry period (González 1995).

The mean botanical composition of diets was formed by grasses (Chloris virgata Sw 72.28 %, Cynodon dactylon (L.) Pers. 5.52 % and Setaria spp.  6.10 %), shrubs (Acacia cochliacantha 6.93 %, Acacia farnesiana (L.) Willd. 3.19 %, Prosopis laevigata 0.16 % and Pithecellobium dulce 1.01 %), legumes (Indigofera jamaicencis Spreng 0.03 %), and herbaceous plants (Desmanthus virgatus (L) 0.27 %, Ipomoea pedatisecta Mart. et Gal 3.34 %, Mitracarpus hirtus (L) DC 0.11 %, Aeschynomene americana (L) 0.34 % and Euphorbia nutans Lam. 0.72 %).

Experimental procedure. Lambs grazed daily from 9.00 a.m. to 6.00 p.m. During the night, they were kept in pens (3 x 3 m), with ground floor and galvanized roof, with free access to water in the treatments with 15 and 30 %. The animals received ground pods of Acacia cochliacantha in feeding troughs every day, with 102 and 205 g of DM/lamb, equivalent to 15 and 30 % of dry matter requirements, respectively, according to NRC (2007).

The adapting period lasted 10 d. the record of liveweight was performed every 21 d for five periods.

Six lambs were sacrificed from each group, selected at random. The living animal and the hot carcass were weighed with a scale of 100 g. A top loading balance was used to weight the pericardial and perirenal fat, heart, kidneys, liver and gallbladder. 

A sample of the Longissimus dorsi muscle of each sheep was taken, through a dissection from the first to the seventh thoracic vertebra of the left side of the carcass. The samples were refrigerated at 4 ºC during 24 h and, later, they were frozen up to -20 ºC until their
processing.

The studied variables were total weight gain (TWG), daily weight gain (DWG), hot carcass yield (HCY), weight of the pericardial and perirenal fat, and weight of the heart, kidneys and gallbladder. Proximal chemical analysis, content of gallic acid and profile of fatty acids were performed to the Longissimus dorsi muscle. The fatty acids were classified as total lipids (TL), saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA).

Chemical analysis. The bromatological composition of the consumed grass and the supplement was determined at the Laboratorio de Bromatología y Bioquímica de la Universidad Nacional Autónoma de México (UNAM), according to AOAC (2003). The NDF and ADF were determined according to the described by Van Soest et al. (1991). In vitro digestibility of dry matter (IVDDM) of diets of grazing lambs was determined regarding the technique of Tilley and Terry (1963), and the digestibility of Acacia cochliacantha pods was performed In vivo, using the conventional method, according to McDonald et al. (2006).

Muscle samples were processed at the Laboratorio de Química y Análisis de Alimentos de la Facultad de Química de la Universidad Nacional Autónoma de México. A proximal chemical analysis was also carried out. Humidity was determined through dehydration at 60 ºC, ashes through incineration at 550 ºC and the crude protein by the method of Kjeldahl (AOAC 2003). Total lipids (TL) were determined according to Folch et al. (1957). Identification and quantification of fatty acids were performed through saponification and methylation, using gas chromatography in Varian Star 3400 CX equipment, with Split injector and flame ionization (Bligh and Dyer 1959, and Morrisson and Smith 1964). Total poly-phenols (TP) were determined according to Folin-Ciocalteu, through the colorimetric method proposed by Taga et al. (1984). TP concentration was calculated using the gallic acid as standard.

RESULTS AND DISCUSSION

The supplement intake in both groups was 100 %. Table 2 shows that the DWG of the three treatments statistically similar, with 63 g as average. The values of the treatments with 15 (59 g) and 30 % (63 g) can be attributed to the high content of CF and lignin in the pods, compared to the forage from grazing (table 1). This possibly led to a lower digestibility of the celluloses in the pods and, with that, to a lower energy contribution (Bondi 1989).  

The contribution of the supplement was 49.68g (15%) and 99.85 g (30%) of dry matter, which possibly provoked the decrease equivalent to forage in grazing.

Values of DWG, HCY, and weights of liver, gallbladder, heart, kidneys, and  pericardial and perirenal fat (table 2), as well as the percentages of humidity, protein, polyphenols and fat from the Longissimus dorsi muscle (table 3) had no statistical differences among treatments. This can be attributed to the similarities of diets in the content of all the nutrients of consumed forage in the grasslands (table 1), and to the probable substitutive effect of the fruit in the intake of grasses in the treatments with 15 and 30 %.

The DWG of this study were similar or close to those reported by Vázquez et al. (2012), who reffered values of 68 g in Pelibuey x Dorper lambs grazing Paspalum notatum and Axonopus compressus, supplemented with nutritional blocks with 20 % Leucaena leucocephala  plus  20 % of wheat bran. Likewise, Fernández et al. (1997) stated 71 g in lambs grazing native grasslands, complemented with nutritional blocks. Ortiz et al. (2007) indicated 77 g with a feeding based on Bothriochloa pertusa and supplemented with molasses (6 g kg^-1 of liveweight). This can possibly be attributed to the variety of plant species (grasses, shrubs and herbaceous plants) from the grasslands consumed by the lambs in this study.

Regarding the HCY of grazing lambs, Romano et al. (1983) and Lemes et al. (2014) reported figures of 37.2 and 37.16 %, respectively. Ortiz et al. (2007) pointed out 45.8 %, when lambs were fed with native grasslands of Bothriochloa pertusa and supplemented with molasses (6 g kg^-1 of liveweight). This could be caused by the highest ingestion of energy represented by the supplementation.

Regarding liver weight, Ortiz et al. (2007) reported 537 g in lambs fed in native grasslands of Bothriochloa pertusa and supplemented with molasses (6 g kg^-1 of liveweight). This is probably caused by the sugars provided by the molasses. These authors pointed out similar values for kidney weight (79 g) and heart weight (106 g), respectively. 

Fat percentages were statistically similar among treatments, with 1.71 % as average value, which gives the meat its lean characteristic (table 3).

The contents of TFA, determined in the Longissimus dorsi muscle of the lambs in this study, were similar to those pointed out by Díaz et al. (2005) in lambs (1682.75 mg) in an extensive system from Uruguay. However, TFA values in lambs fed with grain-enriched rations in Germany and the United Kingdom were 2,808.75 mg and 2 430.74 mg, respectively.

The average percentage in the three treatments of C18:1 was reduced, to 9.91 %. Reza et al. (2012) reported 39.91 % and Mazzone et al. (2010) stated 30.87 % in lambs fed with hay from grasslands and supplemented with grains. This difference could be caused by the supplementation, which influenced on the poly-unsaturated/saturated (P/S) fatty acids relation, with 0.19 and 0.42, respectively, regarding the 0.03 obtained in this study.

Fat contents and the profile of fatty acids from the Longissimus dorsi muscle obtained in this study can be attributed to the forages consumed during grazing and to the supplementation with pods of Acacia cochliacantha. It can be also attributed to the possible effect of tannins within the shrub leaves (24.82 %) (Olivares et al. 2014) and within the supplement (5.03 %) (Reyes et al. 2013) because these metabolites decrease the hydrogenation of fats at ruminal level, as informed by Priolo et al. (2005) and Vasta et al. (2007).

Among the percentages of SFA, the C18:0 had the highest representation (37.46 %). Consequently, percentages corresponding to C12:0, C14:0 and C14:0 decreased (table 5). This condition is related to the benefits it brings to human health (Paim et al. 2014). Regarding the estearic acid (C18:0), Willems et al. (2014) stated 36.30 %, and amounts similar to those of this study in grazing lambs.

The percentage of fat in the lambs of this study, lower than 2 % of the Longissimus dorsi muscle, belongs to diets based on forages. Reza et al. (2012) reported a similar situation, with 1.92 % in lambs fed in an extensive system. These values can be attributed to carcasses considered as lean. However, these authors obtained 2.41 % of fat with the grain supplementation. Mazzone et al. (2010) informed 2.80 %, attributed to the energy supplementation represented by grains.

The reduced contents of C12:0, C14:0, C16:0, C18:0 and C18:1, and the close relation of C18:2-n6/c18:3-n3, obtained in this study, are beneficial for human health, regarding the prevention of cardiovascular diseases (Webb and O´Nell 2008, Russo 2009, Hunter et al.  2010, Dervishi et al. 2011 and Paim et al. 2014).

The C:22:1n-9  was different (P < 0.05) among treatments. However, the amount of this mono-unsaturated fatty acid was not reflected on the whole amount of MUFA (table 5).

CONCLUSIONS

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Received: November 12, 2014
Accepted: May 25, 2015

E.J. Mireles, Unidad Académica de Medicina Veterinaria y Zootecnia de la Universidad Autónoma de Guerrero, México. km 2.5 Carretera Cd. Altamirano- Iguala Cd Altamirano Gro. CP 40660. Email: emirelesmartinez@gmail.com