Comparison of fatty acid profile of longissimus dorsi muscle in indigenous Lori cattle reared under rural and semi-industrial production system

A Kiani, M H Gharoni¹, R Shariati² and E Fallahi³

Animal Science Group, Lorestan University, Khoramabad, Iran
kiani.a@lu.ac.ir   ;   arkashkia@gmail.com
¹Faculty Veterinary, Lorestan University, Khoramabad, Iran
²R&D section, Garrin Dam Simorgh, Khoramabad, Iran
³Nutritional Health Research Center (NHRC), Lorestan University of Medical Sciences, Khoramabad, Iran

Abstract

In this study, the effects of production system and slaughter season on ratio of ω-6:ω-3 fatty acids (FA) and ratio of poly-unsaturated FA to saturated FA (P:S) of meat in indigenous Lori cattle were investigated. In total, 20 Lori bulls (12-15 month) were fed either with 100% forage based diet (rural) or with 60% forage and 40% concentrate (semi-industrial) were slaughtered either during spring or during fall season. Meat samples (100 g) were dissected from longissimus dorsi muscle between rib12^th and 13^th and were homogenate either without fat (lean meat) or with subcutaneous fat (fat meat). Meat fat was extracted and methylated in one-step method and FA profile was determined.

 

Spring meat compared to fall meat had higher oleic acid (8.1 vs. 5.9%) and less linoleic acid (33.4 vs. 37.8%). Neither production system nor slaughter season showed any significant effects on P:S ratio. Lean meat had higher P:S ratio than fat meat (0.4 vs. 0.1). Ratio of ω-6:ω-3 in lean meat was lower than that in fat meat (6.2 vs. 7.9). Rural meat had lower ratio of ω-6:ω-3 than semi-industrial  (5.2 vs. 8.9). In conclusion, lean meat of Lori cattle had healthy P:S ratio (0.4). Rural meat had lower ratio of ω-6:ω-3 than semi- industrial meat presumably due to higher forage intake in rural production system. Thus Lori beef meat produced in rural system proposes healthier meat for consumers in respect to ω-6:ω-3 ratio.

Keywords: beef, Indigenous Lori cattle, polyunsaturated fatty acids, production system

Introduction

Red meat is a component of a healthy diet with good balance of essential amino acid and important micronutrient (Biesalski  2005; Williams  2007). Red meat is known as source of bioavailable iron and zinc and also contains magnesium, copper, cobalt, phosphorus, chromium, nickel and most importantly selenium. Red meat provides thiamin, riboflavin, pantothenic acid, folate, niacin, B₆ and B₁₂ (Williams  2007). However, red meat is blamed for its link with cardiovascular and other chronic diseases mainly because of its high saturated fatty acids (SFA) and low polyunsaturated fatty acids (PUFA) content (McAfee et al 2010). Fatty acid profiles of ruminants products (meat and milk) generally originates from ingested feedstuff. Ruminant diet has usually less than 5% fat per dry matter and α-linolenic acid (C18:3) and linoleic acid (18:2) are the two abundant fatty acids in ruminant feedstuff. However, ruminant products (meat and milk) have high percentage of SFA but low percentage of PUFA due to rumianl biohydrogenation of fatty acids (Jenkins et al 2008). Thus, it is not surprising that the ratio of PUFA to SFA (P:S ratio) in red meat is far from recommended ratio (i.e., >0.4).

 

Red meat is also source of two important groups of long chain fatty acids in healthy diet; ω-3 and ω-6 fatty acids (Williams 2007). The known ω-3 family are α-Linoleic acid (ALA, C18:3), eicosapentaenoic acid (EPA, C20:5), docosapentenoic acid (DPA, C22:5) and docosahexaenoic acid (DHA, C22:6). Linoleic acid (LA, C18:2), gamma-linolenic acid (GLA, C20:3) and arachidonic acid (AA, C20:4) are the main members of ω-6 family. Red meat is the main dietary source of DPA because DPA accumulate in mammals but not in sea animals (Givens et al 2006). Both ω-3 and ω-6 fatty acids are imperative for human nutrition and are critical for body functions (Di Pasquale 2009). The low amount of ω-3 family and extra amount of ω-6 family in most of the foods lead to an unbalanced ratio of omega-6 to omega-3 (ω-6:ω-3 ratio). This ratio in the most of industrial and conventional animal products (meat and milk) has been reported to be 15:1 to 20:1, whereas the recommended ratio of ω-6:ω-3 ratio is  2:1 to 4:1 (Simopoulos 2002). A large number of studies has shown direct links between unbalanced ω-6:ω-3 ratio and many human chronic diseases (Simopoulos 2008). Therefore there is an urgent need to modify or to propose alternative sources of meat with healthier ω-6:ω-3 ratio (Kouba and Mourot 2011).

 

Beef meat in many countries (including Iran) is produced either in rural or semi-industrial production system. Basically, animals in these two production systems are indigenous or cross breeds which fatty acid profile of their product are not yet fully determined. In semi-industrial production system animals are usually fed by 40% concentrate and 60% forages. The forage part of the ration during spring contains green forages whereas agricultural by products (such as different kinds of straw) are main fibrous part of the diet during summer and early autumn Similarly, cattle in rural production system are fed by green forages and grazed in natural ranges during spring but they are fed agricultural by products during summer and autumn. Therefore, the nutritional background of cattle that are sacrificed at two seasons are different though the proportion of forage in daily ration is similar.  The differences in animal nutrition in semi-industrial and rural system at different sacrifice seasons might affect the fatty acid profile of the meat. On the other hand, red meat is consumed either as lean meat (with low fat) or as minced meat (with high fat content) which the differences in their fatty acid are not clearly know. Therefore, in the present study fatty acid profile of red meat of indigenous Lori cattle reared in rural and semi-industrial production system was determined. Furthermore, the effects of production system (rural vs. semi-industrial) and slaughter season on ω-6:ω-3 ratio and P:S ratio of two type of meat in indigenous Lori cattle breed were investigated.

Materials and methods

Animals and meat samples

 

In total, twenty Lori bulls (12 to 15 month age) were slaughtered under commercial processing conditions (Gholshan Abbattoir,  Khoramabad, Lorestan) during spring and autumn season. All calves were reared with their dams until weaning at 5 months of age. Nutritional background of the animals during the last two months prior to slaughter time was recorded. In rural production system, cattle grazed natural ranges (Aleshtar, Lorestan, Iran) during April and May. The predominant plant species of the ranges were ryegrass (Lolium perenne) and clover (Trifolium spp). However, during the summer time calves were fed by agricultural by products mainly wheat and barley straw. In semi-industrial production system, animals were fed a diet with 60% forage and 40% concentrate. During April and May, green red clover and green fresh alfalfa were contributed up to 60 % of the total daily intake. The rest were barley, wheat bran and soyabean meal with 22%, 10% and 5% respectively.  However, during August and September , the forage part of the animals ration were fed by 30 % dried alfalfa, 30% wheat straw .The average slaughter body weight (± SD) was 158 ± 35 and 274 ±83 kg for animals in rural and semi-industrial production system respectively. Meat samples (about 100 g) were taken from the loin portion of longissimus dorsi (between ribs 12^th and 13^th) muscles on the left side of the carcass. All meat samples were collected within 3 hours after slaughter and stored at + 4 ̊ C for 24 hours. Samples were divided into two sub-samples; either without subcutaneous fat (lean meat) or with 30 % subcutaneous fat (fat meat). Both group of samples were grounded, in a food processor (3×5 s), and stored in −80 ̊ C pending analysis.

 

Lipid extraction and methylation

 

Fatty acid methyl esters (FAME) were determined using the procedures described previously by Sukhija and Palmquist (1988) with some modification. About 0.1 g meat sample was weighed by digital scale (KERN, Germany) and then was dried by means of freeze dryer. Freeze-dried sample was placed into culture tube (16*125 ml, Scott glass tube). One ml heptan including internal standard (C13:0) was added and mixed. Then 0.2 ml of sodium methylate (25%) was added and the tube was put in a 50 °C water bath for 10 minutes. After that, sample was cooled for about 5 minutes. Then 3 ml of freshly made methanolic HCl 10 % (prepared by adding 20 ml of acetyl chloride to 100 ml of anhydrous methanol) was added and vortexed. The tube was put in a 90 °C steam bath for 30 minutes and then the tube sample was cooled. Finally, one ml of heptane and three ml of potassium carbonate 10% was added and mixed for one minute. The sample was centrifuged (Centrifuge 5415 R; Rotofix 32A, Germany) in 5 minutes at 5000 r.p.m. Heptane phase (upper phase) was transferred to the GC vial (1.5 ml) using pastor pipette.

 

Determination of fatty acid composition

 

FAME were analyzed by gas chromatography with flame ionization detection (GC-FID; HP 6890 chromatograph, Hewlett-Packard, Avondale, PA, USA) using a Chrompack CP-Sil 88 TM fused silica capillary column (100 m × 0.25 mm i.d., 0.2 mm film thickness; Varian Inc., Walnut Creek, CA, USA). Briefly, the oven temperature was initially 150 °C (held for 5 minute), then increased at 5 °C min⁻¹ to 180 °C (held for 30 minute), then increased at 1 ◦C min⁻¹ to 190 °C (held for 5 minute) and finally increased at 1 °C min⁻¹ to 200 °C (held for 35 minute). Hydrogen was used as the carrier gas at a flow rate of 1.0 ml.min^-1. The injector and detector temperatures were maintained at 280 and 300 °C respectively. Identification of common fatty acids was accomplished by comparison of sample peak retention times with those of FAME standard mixtures (Supelco^TM 37 component FAME Mix, Supelco-47885-U, Sigma-Aldrich Chemie GmbH, Germany). Quantification of total FAME was done using Tridecanoic acid (13:0) as internal standard (Fluka-91988, Sigma-Aldrich Chemie GmbH, Germany). Results for each fatty acid were expressed as mg per 100 g total fatty acids.

 

Statistical Analysis

 

Data were analyzed using the MIXED procedure of SAS Version 9.2 (SAS Institute, Cary, NC, USA). The model considered the fixed effect of meat sample type (lean meat vs. fat meat), slaughter season (spring vs. fall) and production system (semi-industrial vs. rural) and the interaction effects. Each animal from the sample type was considered as the subject (random effect) and the sample type as repeated measures. Because the interactions effects were not significant, the interactions were excluded (Littell et al 1998).

Results

Fatty acid profiles of Lean- meat vs. fat meat

 

The means of fatty acid composition (%) in beef meat with subcutaneous fat (fat meat) and without fat (lean meat) are shown in Table 1. Sum of SFA in lean meat (44.6 %) and fat meat (47.4 %) were not significantly different (P > 0.05). Lean meat had significantly lower percentage of MUFA (37.7 % vs. 46.9 %) but higher percentage of PUFA (18.9 vs. 4.0 %) than fat meat. The P:S ratio in lean meat was significantly higher than that in fat meat (0.4 vs. 0.1, P < 0.05). The ratio of ω-6:ω-3 in lean meat was significantly lower than that in fat meat (6.2 vs. 7.9, P < 0.05) (Table 1). Total fatty acid (g per 100 g meat) in lean meat and fat meat were 5.3 and 16.6 g (Table 2). As the table 2 shows , lean meat had significantly lower palmitic acid, stearic acid, sum of SFA, oleic acid, sum of MUFA but higher PUFA and  total ω-3 fatty acids than fat meat.

 

Effects of slaughter season on fatty acids profile of beef meat

 

Slaughter season had no significant effect on sum of SFA and sum of PUFA (P > 0.05). Oleic acid and sum of MUFA in spring season were 33.4% and 38.0 % and were significantly lower than those in fall season 37.8 % and 42.6 % respectively. Spring meat had higher linoleic acid and linolenic acid than fall meat (P < 0.05). Neither P:S ratio nor  ω-6:ω-3 ratio had affected by slaughter season in beef meat (P > 0.05). Total fatty acid (g per 100 g meat) was not different between meat from spring and autumn slaughter time with 11.1 and 10.5 g respectively (Table 2). The quantity of fatty acids (mg per 100 g meat) were almost the same in two slaughter time however spring had higher linoleic acid and lower docosahexaenoic acid than fall (table 2).

 

Effects of production system on fatty acids profile of beef meat

 

Production system had no significant effect of sum of SFA, sum of MUFA and sum of PUFA in beef meat as percentage (Table 1). Rural meat had significantly higher percentage of palmitic acid (26.8 vs.24.3 %, P < 0.05) but lower percentage of linoleic acid (5.7 vs.8.2 %, P < 0.05) than semi-industrial meat. Sum of ω-6 fatty acids in semi-industrial meat was significantly higher than that in rural meat (P < 0.05). Sum of trans fatty acids in semi-industrial meat was significantly higher than that in rural meat (2.5 vs. 1.75 %, P < 0.05). Ratio of ω-6:ω-3 in rural meat was significantly lower than that in semi-industrial meat (5.2 vs. 8.9, P < 0.05). As the Table 2 shows, Total fatty acids (g per 100 g meat) in semi-industrial and rural production system were 10.5 and 11.3 g respectively with no significant differences (P > 0.05). However, quantity of oleic acid in rural meat was significantly higher than that in semi-industrial meat (4.3 vs. 3.9 g per 100 g meat, P <0.05).