Carcass and meat quality of Thai native cattle fattened on Guinea grass (Panicum maxima) or Guinea grass–legume (Stylosanthes guianensis) pastures

Meat Science 81 (2009) 155–162

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Carcass and meat quality of Thai native cattle fattened on Guinea grass (Panicum maxima) or Guinea grass–legume (Stylosanthes guianensis) pastures S. Jaturasitha a,*, R. Norkeaw a, T. Vearasilp a, M. Wicke b, M. Kreuzer c a

Department of Animal Science, Faculty of Agriculture, Chiang Mai University, 239 Heuy Kaew Road, Tumbol Suthep, Chiang Mai 50200, Thailand Institute of Animal Breeding and Husbandry, Georg-August-University of Göttingen, Albrecht-Thaer-Weg 3, D-37075 Göttingen, Germany c ETH Zurich, Department of Agricultural and Food Science, Universitaetstrasse 2, CH-8092 Zurich, Switzerland b

a r t i c l e

i n f o

Article history: Received 6 June 2008 Accepted 11 July 2008

Keywords: Cattle Muscle fibre Forage Meat quality

a b s t r a c t Carcass and meat quality of Thai native cattle, fattened for 2 years on Guinea grass (Panicum maxima) and Guinea grass–legume (Stylosanthes guianensis) pastures, were investigated in twelve 3-years old males. Groups had similar carcass quality except for kidney fat percentage (higher in cattle of the grass–legume group). This group also had a lighter meat (Longissimus dorsi, Infraspinatus) than the grass-only fed cattle. Shear force was generally at the borderline to tender meat, and was unaffected by treatment as were other texture-related properties except muscle fibre diameter. Meat of the grass–legume group was perceived less juicy (P < 0.05) but more tender (P < 0.1). The meat of the grass–legume-fed cattle also had more intramuscular fat (4.3% vs. 3.4%) and a slightly less favourable n 6:n 3 fatty acid ratio (2.2 vs. 2.0). In conclusion, the mostly weak differences in carcass and meat quality did not clearly favour one of the grazing systems. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Thai native cattle, a Bos indicus (Zebu; thorasic humped cattle) genotype, originating from India and later spread across southeast Asia (Maule, 1990), have existed in Thailand for a long time, but this without a clear common breeding goal except adaptation to harsh environmental conditions. Accordingly, this cattle type is typically quite light (adult males weigh 300–350 kg, females 200–270 kg), heat tolerant, disease resistant and fertile (Wannapat, 2004). They are often used as draught animals especially in rice fields. After field discharge they are sold and later slaughtered. The beef quality is poor because of their age at slaughter, and only specific post-slaughter strategies may improve tenderness of the beef of such animals (Jaturasitha, Thirawong, Leangwunta, & Kreuzer, 2004). Thailand imports large quantities of beef (Angkuro, 2003; DLD, 2004) especially in frozen form. Recently, the increasing awareness of consumers of the way of production and a distinct demand for natural systems of meat production has generated an emerging market for beef from Thai native cattle fattened under extensive conditions, i.e. without or with few concentrate and without growth promoters. There are some data on growth performance and carcass characteristics of this cattle type (e.g., Phaowphaisal & Wijitphan, 2006), but the quality of such beef has not been determined. In order to guarantee success, alternative beef production * Corresponding author. Tel.: +66 53 221667; fax: +66 53 357601. E-mail address: [email protected] (S. Jaturasitha). 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.07.013

systems based on Thai native cattle have to result in improvements of beef quality, particularly tenderness, compared to beef harvested from the draught animals. One major constraint of foragebased fattening systems is the limited energy density of the diet and, accordingly, a comparably high age at slaughter. Tropical grasses are typically not only low in digestible organic matter but also in crude protein (CP) degradable in the rumen. The latter additionally reduces energy supply, as insufficient N supply impairs fibre degradation (Broderick, 2003). Therefore, combining such grasses with legumes, higher in CP due to their ability to assimilate nitrogen, might help to cope with this limitation (e.g. Hess et al., 2003). Additionally, it has been demonstrated that forage legumes may modify the fatty acid profile of lipids in meat (Scollan et al., 2006). Provided this would result in an increase in the desired omega-3 (n 3) fatty acids (Dewhurst, Shingfield, Lee, & Scollan, 2006), the strategy would further enhance the advantage of beef from pasture-fed cattle over that from high-concentrate fed animals (reviewed by Scollan et al. (2006)). However, the few data available on the effect of forage legumes so far have been obtained with forages grown in temperate climates, and comparable studies on tropical forages are still missing. The aim of the present experiment was (i) to study the carcass and meat quality of pasture-fed Thai native cattle which have, to the knowledge of the authors, not been assessed for meat quality before, and (ii) to put special emphasis on the question whether beef quality from indigenous cattle grazing tropical mixed grass– legume pastures is different from beef obtained from tropical grass-only pastures.

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2. Materials and methods 2.1. Experimental pastures The two pasture types, grass alone and grass–legume swards, had been established 5 years in advance of the experiment. Each pasture included Guinea grass (Panicum maxima; cultivar Purple guinea). Guinea grass originates from Tanzania and has been grown in Thailand since 1987 (Tudsri, 2004). It is quite tolerant to drought, grazing and low pH, but needs fertile soils and is susceptible to weed invasion in the humid tropics thus requiring proper management. On the second half of one of the experimental pastures, the legume Stylosanthes guianensis (cultivar ‘Stylo 184’, CIAT, Cali, Colombia) was established. This herbaceous leafy legume was introduced in Thailand in 1993 (Tudsri, 2004). The test sites were rain-fed in the rainy seasons and irrigated in the dry seasons always after grazing. During the 2 years of the experiment, the grass and legume swards were well-growing except in the dry season (4 months) where, despite the occasional irrigation, some extra Guinea grass hay had to be supplemented to the cattle due to feed scarcity. Weed invasion of the pastures was low. Forage samples were collected three times per season (start, middle and end of the rainy season) in each of the two experimental years.

2.2. Fattening and slaughter procedures Twelve steer calves of the Thai Native genotype, obtained from the Mahasarakham Animal Nutrition and Development Station, Department of Livestock Development (DLD), Mahasarakham, Thailand, were reared for 1 year together with their dams. After that they were divided into two equal groups, balanced for body weight, and allowed to graze the two experimental pastures from then on. Fattening on the experimental pastures lasted for 2 years. No concentrate was supplemented, but the animals had ad libitum access to NaCl and a commercial vitamin–mineral mix for cattle. The stocking rate was set to three head per hectare. Each experimental pasture was divided into four equal parts, and the animals were rotated every week between these parts. For that purpose, the grass–legume pasture was separated in a way that the grass and the legume sections always made up half of the area. After grazing, urea was spread at a rate of 60 kg/ha in order to be grazed again after 3 weeks had passed. On average of the six sampling times, the legume contained more than twice the amount of CP, slightly more ether extract as well as neutral detergent fibre and somewhat less non-NDF carbohydrates (Table 1). This suggests that the legume was superior to the grass in (ruminally-degradable) protein but not in energy content. The fatty acid profiles of the forages were consistent with those reported on the composition of temperate grasses and legumes (e.g., Boufaïed et al., 2003; Dewhurst et al., 2006; Van Dorland, Wettstein, Leuenberger, & Kreuzer, 2008). At an age of 3 years, the animals were slaughtered in a randomised order within 2 days at the Nong Kwang slaughterhouse, Ratchaburi, Thailand, following procedures outlined in Jaturasitha (2004). All experimental procedures were carried out following the animal welfare standards of Department of Livestock Development, Ministry of Agriculture and Cooperative, Royal Thai Government. Hot (45 min postmortem (p.m.)) and chilled carcasses (24 h p.m.) were weighed, and carcass length was determined. Dressing percentage was defined as the ratio of chilled carcass weight to live weight. Loin eye area was measured between the 12th and the 13th rib. Proportions of retail cuts were determined both by dissection of the right carcass side according to Meat and Livestock Commission (MLC; Church & Wood, 1991) and of the left carcass side applying the Thai cutting style (Jaturasitha, 2004). Weights of var-

Table 1 Chemical composition of dried Purple Guinea grass (Panicum maxima) and the legume Thapra stylo (Stylosanthes guianesis) (g/kg dry matter) as harvested from the experimental sites (n = 6 per forage type) Forage type

Guinea grass

Legume

Organic matter Crude protein Neutral detergent fibre (NDF) Acid detergent fibre (ADF) Acid detergent lignin (ADL) Hemicellulose (NDF–ADF) Cellulose (ADF–ADL) Non-NDF carbohydratesa Gross energy (mJ/kg) Ether extract Total fatty acids

895 83 634 466 42 169 424 161 17.2 17 16

909 179 561 431 64 131 366 148 19.4 21 19

Fatty acids (% of totally analysed fatty acids) C12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 C20:0 Saturated fatty acids (SFA) Monounsaturated fatty acids Polyunsaturated fatty acids (PUFA) Total n 3 Total n 6

1.04 0.81 21.02 3.03 3.84 16.73 48.94 0.47 29.35 4.98 65.66 48.94 16.73

1.26 0.77 22.23 3.16 3.97 19.50 44.68 0.50 30.64 5.18 64.18 44.68 19.50

Fatty acid ratios PUFA:SFA n 6:n 3

2.24 0.342

2.09 0.436

a

Organic matter minus crude protein, ether extract and NDF.

ious internal organs and other dissected body parts were recorded, too. Samples of three muscles from different body sites, Longissimus dorsi (LD; 6th–12th rib), Semitendinosus (ST) and Infraspinatus (IS; situated in the scapular (chuck)) were prepared from the left carcass side in order to study meat quality in muscles with different connective tissue properties. 2.3. Laboratory analyses Forages were analysed by methods of AOAC (1995) for dry matter and total ash, CP (Kjeldahl; 6.25  N), ether extract and gross energy. Detergent analysis according to Goering and van Soest (1970) included neutral (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL). For NDF analysis, no sodium sulfite had been applied and samples had not been digested with a-amylase because starch contents were assumed to be low. Detergent fibre values were not corrected for ash content. Meat pH (pH meter model 191, Knick, Berlin, Germany) and electrical conductivity (EC) (model LF 196, WTW, Weilheim, Germany) were determined in LD and ST at 45 min and 24 h p.m. After dissection, the LD, ST and IS samples were cut into 2.5 cm thick slices, put into polyethylene bags, chilled at 4 °C for 48 h and then stored in the refrigerator outside of the bag for 1 h (‘blooming’) before conducting colour measurements using a Chroma Meter (Minolta, CR-300, Osaka, Japan). Water-holding capacity (WHC) was assessed via substance losses occurring during different procedures. Thawing and cooking losses were determined in the 2.5 cm thick slices of LD, ST and IS frozen in polyethylene bags at 20 °C. Thawing was performed over 24 h at 4 °C. Before weighing, the sample surfaces were dried with soft paper. Afterwards, samples were sealed in heat-resistant plastic bags to be boiled in a Korimat (model 120/1.6, Christian Wanger, Esslingen, Germany) at 80 °C until an internal temperature of 70 °C was reached. The latter was controlled by a thermocouple (Consort

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T851, Cohasset, MA, USA). Samples were cooled to ambient temperature and weighed after drying the surfaces with soft paper. For the determination of the grilling loss, 2.5 cm thick slices were grilled in a convection oven (model 720, Mara, Taipei, Taiwan) at 150 °C until an internal temperature of 70 °C was reached. In the LD, additionally drip loss according to Honikel (1987) was determined. In the boiled samples, shear force and energy were measured after cooling and drying. A steel hollow-core device with a diameter of 1.27 cm was punched parallel to the muscle fibres to obtain six pieces from each muscle sample. Measurements were carried out on a material testing machine (model 5565, Instron Ltd., Buckinghamshire, UK) using a Warner–Bratzler shear. A crosshead speed of 200 mm/min and a 5 kN load cell calibrated to read over a range of 0–100 N were applied. Soluble, insoluble and total collagen contents were determined according to Hill (1966). Briefly, meat samples of 4 g were mixed with 8 ml of strength Ringer solution (NaCl2, 147 mM; KCl, 4 mM; CaCl2, 2.2 mM), homogenised at 10,000 rpm for 1 min and then boiled in water bath at 77 °C for 70 min. After that the samples were centrifuged at 5200g for 26 min and separated into two portions (supernatant and natant). For hydrolysis, 30 ml H2SO4 were added to each flask and covered with watch-glass. Flasks were dried in an oven at 105 ± 1.0 °C for 16 h. The content was transferred into a volumetric flask of 500 ml, and the volume was adjusted to 500 ml by adding distilled water (AOAC, 1996). For the subsequent colour measurements, 2 ml of the solution were pipetted into a test tube of 10 ml size with 2 ml distilled water, supplemented with 1 ml of oxidant solution, and then intensively shaken. Another millilitre of colour reagent solution was added and the sample was shaken again. The test tube was placed into a water bath at 60 ± 0.5 °C for 15 min. After that it was cooled under running cold water for 3 min, then wipped dry. The solution from the test tube was measured for its light absorption at 558 nm in a spectrometer (UV 1601, Shimadzu, Tokyo, Japan) which is the wavelength characteristic for hydroxyproline. The soluble collagen was calculated as 7.52  hydroxyproline found in the supernatant of the preparation whereas insoluble collagen was 7.25  hydroxyproline found in the natant. For muscle fibre analysis, samples from the center of the ventral side of the LD, ST and IS were taken. Serial cross-sections (10 lm thick) were cut and subjected to combined ATPase/NADH diaphorase staining (modified after Horak (1983)). The density of the histochemical reaction product in the ATPase/NADH diaphorase staining was determined for each fibre. By using three density classes for ATPase, three different fibre types (types I, IIA and IIB; Brooke & Kaiser, 1970) were defined and specified using an image analyser (LUCIA, Japan). Additionally, the cross sectional area (lm) of individual myofibres was measured (250 per replicate equivalent to a total 2500 fibres per animal) (Klont, Brocks, & Eikelenboom, 1998), and proportions of each fibre type (expressed as number  area percentage) were calculated. For sensory evaluation, a test panel was selected from a number of students and faculty members of the Animal Science Department of Chiang Mai University, who had undergone sensory evaluation training following the methods of Viriyajare (1992). Grilled 2.5-cm slices of LD, ST and IF were cut into pieces of 1.3  1.3  1.9 cm and served warm. Panelists were asked to grade samples for tenderness, juiciness, flavour and overall acceptability by a scale ranging from 1 (low) to 9 (high). Samples were served subsequently in a randomised order with respect to group and animal. The 36 samples (from 12 animals and three muscles) were tested by six persons each. Samples of the LD were minced and analysed in duplicate for moisture, fat and protein contents (Kjeldahl; 6.25  N) according to AOAC (1995). Cholesterol concentrations were determined in samples after extraction of the fat (Folch, Lees, & Stanley, 1957)

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and its saponification (Abell, Brodie, & Kendall, 1951). In the residual extract cholesterol was measured colorimetrically according to Jung, Biggs, and Moorehead (1975). Fatty acids in forages and meat samples were extracted by a mixture of chloroform/methanol (Folch et al., 1957). Fatty acid methyl esters were prepared according to Morrison and Smith (1964). Gas chromatographic analysis was accomplished with model GC-14B of Shimadzu (Kyoto, Japan) equipped with a 0.25 mm  30 m  0.25 lm wall-coated fused wax capillary column. The carrier gas was helium. Oven temperature programming was an increase from 50 to 220 °C at a rate of 10 °C/min, held for 35 min, up from 200 to 230 °C at a rate of 5 °C/min and then held at 230 °C for 20 min. The injector and detector temperature was 250 °C. Chromatograms were processed using the Millenium 2010 Chromatography Manager (Millipore Corp., Milford, Massachusetts, USA). Susceptibility of the lipids to oxidation was assessed by the 2thiobarbituric acid (TBARS, thiobarbituric acid reactive substances) method (Rossell, 1994). Briefly, samples of 10 g of LD stored for 0, 3 and 6 days in the refrigerator at 4 °C were mixed with 30 ml distilled water for 2 min by a Moulinex household blender. Further 65 ml of distilled water were added, the pH was adjusted to 1.44 with 2.5 ml of 4 M HCl and drops of an antifoaming agent were added. Afterwards the flask containing the sample was connected with the distillation apparatus. Fifty millilitres of the distillate was collected within 15–20 min. Five millilitres of the distillate were allowed to react with 5 ml of TBA reagent. The solution was cooled at room temperature and the absorbance was measured against a blank at 538 nm. The TBARS were calculated by multiplying the absorbance by 7.8. Results were given as concentrations of malondialdehyde in the meat. 2.4. Statistical analysis Data was subjected to analysis of variance with the GLM procedure of SAS (2001) considering pasture type as effect. The tables give the mean values, the standard error of the mean (SEM) and the P-values for the treatment effect.

3. Results At slaughter, live weights of the 3-years old cattle grazing the grass and the grass–legume pastures for 2 years were similar with about 320 kg (Table 2). Differences between treatments in dressing percentage and carcass weight were not significant. Proportions of valuable cuts, as determined by two alternative methods (MLC and Thai style), organs and other body parts also showed few pasturetype effects. One exception was kidney fat proportion which was higher (P < 0.05) in cattle grazing the grass–legume mixture. Early- and late-p.m. meat quality traits, including pH, conductivity and colour, remained mostly unaffected by treatment with the exception of lightness (Table 3). All three muscles were lighter (P < 0.05 in LD and IS) when originating from the grass–legume fed cattle than from the cattle fed only grass, while the three muscles did not differ much in colour traits among each other. No treatment effects were found in water-holding capacity and there was also no clear pattern concerning differences among muscles. Shear force and energy appeared to be higher in IS than in LD and ST which was supported by correspondingly high contents of total and insoluble collagen (Table 4). There were no significant treatment effects in these texture-related variables and in proportions of white, intermediate and red (types I, IIA and IIB, respectively) fibres of the three muscles. However, muscle fibre diameter was larger (P < 0.001 in most fibre types and muscles) in the cattle grazing the grass–legume pasture. Among muscles,

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Table 2 Carcass quality and composition of cattle fattened on two pasture typesa Group

Grass

Grass/legume

SEM

P-value

Table 3 Early postmortem (p.m.) meat quality traits and water-holding capacity of Longissimus dorsi (LD), Semitendinosus (ST) and Infraspinatus (IS) of Thai native cattle fattened on two pasture types

Live weight (kg) Hot carcass weight (kg) Chilled carcass weight (kg) Dressing (%) Carcass length (cm) Loin eye area (cm2)

322 179 176 54.5 111 60.4

320 180 177 55.1 110 59.4

3.0 1.8 1.8 0.10 0.4 0.50

0.91 0.91 0.94 0.37 0.72 0.78

pH 45 min p.m. LD ST

6.84 6.68

24 h p.m. LD ST

Standard MLC cutting style (% of chilled carcass) Fore quarter 27.09 26.98 Chuckb Fore shank 5.36 5.25 Brisket 6.01 5.68 Rib 8.56 9.19 Plate 9.04 9.13

0.105 0.070 0.047 0.057 0.056

0.89 0.82 0.34 0.14 0.82

Hind quarter Flank Shortloin Sirloin Round Kidney fat

0.071 0.048 0.080 0.094 0.093

0.23 0.87 0.89 0.36 0.028

5.13 7.26 11.24 22.56 3.86

5.77 7.32 11.31 21.93 5.52

Thai cutting style (% of chilled carcass) Quadtriceps 9.01 Semitendinosus 2.02 Semimembranosus 5.29 Biceps femoris 6.95 Longissimus dorsi 4.65 Psoas major 1.18 Brisket 5.77 Plate 3.84 Trim meat 3.57 Red meat 28.79 Bone 21.53 Fat 7.62

8.99 2.01 5.28 6.94 4.57 1.17 6.27 3.82 2.72 28.63 21.02 7.70

0.070 0.016 0.041 0.054 0.055 0.022 0.121 0.026 0.110 0.195 0.297 0.133

0.90 0.97 0.95 0.93 0.85 0.95 0.56 0.91 0.29 0.91 0.81 0.93

Internal organs (% of live weight) Heart 0.35 Liver 1.08 Lung with trachea 1.12 Spleen 0.27 Stomach 2.72 Small intestine 1.02 Large intestine 0.36

0.37 1.10 1.21 0.26 2.68 0.90 0.41

0.004 0.008 0.008 0.005 0.010 0.009 0.012

0.43 0.72 0.16 0.64 0.60 0.086 0.58

Other body parts (% of live weight) Head 3.20 Skin 8.84 Fore leg 0.89 Hind leg 0.91 Blood 2.08 Tail 0.56 Testes 0.10 Tongue 0.60 a b

3.46 8.06 0.85 0.88 2.08 0.51 0.10 0.70

0.025 0.061 0.004 0.005 0.028 0.006 0.002 0.008

0.17 0.092 0.16 0.46 0.98 0.29 0.76 0.091

SEM, standard error of mean. Including the Infraspinatus muscle.

IF had a lower proportion of white fibres than the other muscles, and its red and white fibres had a larger diameter. The sensory perception showed a trend (P < 0.1) towards higher tenderness of the LD and the IS of the grass–legume fed cattle (Table 5). At the same time this beef was judged less juicy (P < 0.05 in LD and ST). Flavour and overall acceptability scores were unaffected by treatment. The LD of the cattle grazing the grass–legume pasture had higher fat and cholesterol contents and a lower moisture content (P < 0.05) than the LD from the grass-only fed cattle (Table 6). Effects of pasture type on the fatty acid profile remained weak except for the n 6:n 3 ratio which was higher in the grass–legume fed cattle. Levels of TBARS increased with storage time, but this independently of treatment.

Group

Grass

SEM

P-value

6.83 6.82

0.025 0.027

0.94 0.47

5.52 5.50

5.57 5.49

0.009 0.002

0.38 0.65

Conductivity (ms/cm) 45 min p.m. LD 2.83 ST 2.50

2.76 2.70

0.032 0.030

0.77 0.35

24 h p.m. LD ST

2.46 3.47

0.046 0.094

0.93 0.59

2.49 3.83

Grass/legume

Colour traits Lightness (L*) LD ST IS

36.0 36.2 35.5

37.4 37.2 37.1

0.02 0.05 0.05

<0.001 0.22 0.025

Redness (a*) LD ST IS

20.0 20.1 20.4

19.6 19.7 19.9

0.02 0.06 0.05

0.40 0.69 0.50

Yellowness (b*) LD 15.6 ST 16.3 IS 16.0

15.7 16.4 15.9

0.01 0.04 0.03

0.84 0.89 0.90

5.14 6.11 4.08

0.064 0.237 0.197

0.30 0.31 0.79

32.84 32.80 33.89

32.54 34.44 31.91

0.076 0.168 0.256

0.75 0.19 0.29

Grilling loss (%) LD 31.54 ST 32.23 IS 33.65

33.76 34.91 35.45

0.120 0.320 0.362

0.14 0.25 0.49

4.97

0.074

0.33

Water-holding capacity Thawing loss (%) LD 4.32 ST 4.36 IS 4.45 Boiling loss (%) LD ST IS

Drip loss (%) LD

5.50

4. Discussion 4.1. Carcass and meat quality of pasture-fed Thai native cattle Studies on feeding effects in Thai native cattle are scarce and restricted to growth and carcass characteristics. One of these investigations is from Phaowphaisal and Wijitphan (2006) who fed this cattle type with three different levels of protein and energy. The carcass quality found in the present study was comparable to that reported by Phaowphaisal and Wijitphan (2006). Carcass weight and loin eye area of the Thai native cattle were, however, smaller than those reported for Korean native cattle (Kim, Kim, Lee, & Baik, 2000; Kim, Yoon, Song, & Lee, 2003), even though the Korean cattle had been slaughtered at only 22–26 months of age compared with the 36 months in the present study. Native Chinese cattle (Yellow cattle), slaughtered at 5.3 years of age, had heavier carcasses and larger loin eye areas (Zhou et al., 2001) compared with the Thai native cattle, too, suggesting that also this cattle type exhibits higher adult body weights than the Thai native cattle. Phaowphaisal and

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S. Jaturasitha et al. / Meat Science 81 (2009) 155–162 Table 4 Texture-related properties of Longissimus dorsi (LD), Semitendinosus (ST) and Infraspinatus (IS) of Thai native cattle fattened on two pasture types Group

Grass

Warner–Bratzler shear force (N) LD 42.1 ST 42.8 IS 45.1

Grass/legume 39.6 39.7 43.9

SEM 0.05 0.17 0.16

P-value

Group

Grass/legume

SEM

P-value

0.11 0.31 0.70

Tenderness scorea LD 5.84 ST 5.94 IS 5.44

6.11 5.97 5.89

0.005 0.014 0.016

0.077 0.91 0.098

Juiciness scorea LD ST IS

6.06 6.08 5.80

5.70 5.61 5.47

0.005 0.014 0.013

0.018 0.051 0.13

Flavour scorea LD ST IS

6.47 6.44 6.44

6.68 6.58 6.64

0.005 0.015 0.016

0.15 0.59 0.46

6.57 6.43 6.36

0.004 0.013 0.014

0.13 0.79 0.25

Warner–Bratzler shear energy (mJ) LD 129 ST 128 IS 137

121 122 130

0.3 0.8 0.9

0.38 0.68 0.65

Total collagen (mg/100 g meat) LD 409 ST 558 IS 613

366 530 580

14.2 22.0 26.1

0.14 0.54 0.52

Soluble collagen (mg/100 g meat) LD 154 ST 204 IS 216

138 182 199

6.3 14.2 10.0

0.24 0.45 0.42

Insoluble collagen (mg/100 g meat) LD 256 ST 354 IS 397

228 349 380

8.9 10.5 19.6

0.13 0.79 0.66

Muscle fibre typea proportion (% of total) LD Type IA 33.7 31.4 Type IIA 26.3 22.8 Type IIB 40.0 45.8

1.40 1.21 2.15

0.43 0.18 0.21

ST Type I Type IIA Type IIB

38.6 27.4 33.9

37.9 30.2 32.0

1.71 1.50 1.30

0.82 0.38 0.47

40.7 36.7 22.6

40.6 39.2 20.2

2.43 2.10 2.30

0.99 0.57 0.62

Muscle fibre diameter (lm) LD Type I 52.1 Type IIA 60.0 Type IIB 88.4

58.0 67.4 91.1

0.53 0.49 0.69

<0.001 <0.001 0.051

ST Type I Type IIA Type IIB

47.9 66.2 88.5

59.9 73.8 97.6

0.58 0.54 0.77

<0.001 <0.001 <0.001

66.7 67.1 93.8

70.9 72.4 91.8

0.52 0.55 0.62

<0.001 <0.001 0.226

IF Type I Type IIA Type IIB

IF Type I Type IIA Type IIB

Table 5 Sensory grading of Longissimus dorsi (LD), Semitendinosus (ST) and Infraspinatus (IS) of Thai native cattle fattened on two pasture types

a Type I = slow-twitch oxidative (red); Type IIA = fast-twitch oxidative-glycolytic (intermediate); Type IIB = fast-twitch glycolytic (white).

Wijitphan (2006) described improved lean percentages in some cuts (rib and shortloin) and not in others (chuck, plate, sirloin and round) when elevating protein and energy supply of Thai native cattle which suggests that this cattle type has low nutrient and energy demands and, consequently, exhibits only limit responses to dietary changes. Crossbreeds of indigenous and improved breeds are often superior in lean accretion and percentage compared to purebred indigenous breeds (Lee et al., 2007; Zhou et al., 2001). Accordingly, Wheeler, Savell, Cross, Lunt, and Smith (1990) described an inferior carcass quality of Brahman (Zebu) vs. Hereford and crossbreeds of either Brahman  Hereford or Hereford  Brahman. Also other findings (Lee et al., 2007) suggest that carcass quality of indigenous

Grass

Overall acceptability scorea LD 6.37 ST 6.36 IS 6.08 a

1 = low, 5 = moderate and 9 = high.

Table 6 Chemical composition and fat shelf life of the Longissimus dorsi of Thai native cattle fattened on two pasture types Group

Grass

Grass/legume

SEM

P-value

Chemical composition (g/100 g meat) Moisture Protein Fat Cholesterol

73.2 22.4 3.35 41.0

72.0 21.9 4.27 46.2

0.05 0.03 0.025 0.20

0.035 0.11 <0.001 0.013

Fatty acids (% of totally analysed fatty C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 n 9cis C18:2 n 6 C18:3 n 6 C18:3 n 3 C20:0 C20:1 C20:3 n 6 C20:3 n 3 C20:4 n 6 C20:5 n 3 Saturated fatty acids (SFA) Monounsaturated fatty acids Polyunsaturated fatty acids (PUFA) Total n 6 Total n 3

acids) 2.74 0.43 0.57 27.93 4.42 1.60 0.68 17.64 38.36 2.70 0.18 1.34 0.19 0.14 0.21 0.10 0.41 0.35 50.68 44.05 5.28 3.49 1.78

2.74 0.42 0.56 28.27 4.37 1.64 0.68 17.35 38.19 2.93 0.19 1.30 0.17 0.14 0.20 0.10 0.42 0.33 50.73 43.80 5.47 3.75 1.72

0.006 0.002 0.002 0.032 0.018 0.004 0.002 0.036 0.038 0.012 0.001 0.006 0.001 0.001 0.001 0.001 0.002 0.002 0.050 0.049 0.021 0.014 0.007

0.99 0.50 0.66 0.44 0.85 0.60 0.90 0.56 0.74 0.15 0.070 0.58 0.14 0.25 0.45 0.99 0.70 0.53 0.94 0.72 0.51 0.20 0.55

Fatty acid ratios PUFA:SFA n 6:n 3

0.10 1.99

0.11 2.19

0.001 0.004

0.61 0.002

TBARS (mg malondialdehyde/kg meat) Day 0 Day 3 Day 6

0.171 0.209 0.254

0.188 0.222 0.266

0.0013 0.0016 0.0017

0.21 0.41 0.50

cattle in Asia is inferior to that of crossbreeds and improved breeds. Overall, it seems that Thai native cattle, among Asian native cattle, are particularly light in an adult stage and, as such, particularly inferior to crossbreeds or imported breeds in carcass traits. The levels of meat pH and EC measured at 45 min and 24 h p.m. in LD and ST in the Thai native cattle were in a normal range of

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values found in other cattle types. Also the water-holding capacity was similar to that reported from other grass-fed cattle (Baublits et al., 2006; Varela et al., 2004). It was superior to that found in Chinese cattle genotypes (Lee et al., 2007), but here a methodological reason cannot be totally excluded. The traits related to water-holding capacity of meat are typically determined by genotype and slaughter condition. The valuable cuts (LD and ST) obtained from the present Thai native cattle were at the borderline to 40 N, a threshold level that Shorthose, Harris, Hopkins, and Kingston (1988) found to correspond with the change in consumer ratings from ‘tender’ to ‘nontender’ beef. Shear force of the present beef was lower by a factor of 2–2.5 than that reported by Strydom, Naede, Smith, Scholtz, and van Wyk (2000) for African indigenous cattle and imported breeds, but this was rather the result of an unusually large size of the muscle samples sheared (2.5 cm diameter). In this comparison, meat from the African indigenous cattle genotypes had a lower shear force than that of Santa Gertrudis (an improved Zebu breed), and Strydom et al. (2000) related this to a different myofibrillar fragmentation index. Differences from the present samples to meat of African indigenous cattle genotypes (Strydom et al., 2000) occurred in soluble collagen content (high in Thai native cattle) and percentage of muscle fibre type IIB (43% vs. 35% in African indigenous cattle). Measured percentages in the LD of muscle fibre type I were higher in Hanwoo cattle (Kim et al., 2000) and that of type IIB were lower than those noted in the Thai native cattle. Compared to discharged draught Zebu oxen where the LD had a shear force of about 100 N (Jaturasitha et al., 2004), the LD of the present Thai native cattle exhibited a shear force lower by a factor of 2.5, and the first mentioned beef required intensive postmortem treatment to make it palatable. It is well documented that tenderness decreases when percentage Bos indicus inheritance increases (Shackelford, Wheeler, & Koohmaraie, 1995; Wheeler et al., 1990), and crossbreeds are often superior to purebred indigenous breeds in shear force (Lee et al., 2007). The beef of the present study with Thai native cattle was composed of fat, protein, moisture and cholesterol in proportions similar to Hanwoo cattle (Kim et al., 2000). The fatty acid profile, especially with respect to n 3 fatty acids and n 6:n 3 fatty acid ratio, as found in the Thai native cattle, resembled that of other grass-fed cattle (e.g., Razminowicz, Kreuzer, & Scheeder, 2006; Scollan et al., 2006). Threshold levels of <5:1 in n 6:n 3 ratio (e.g., DACH, 2000) and 1:1–4:1 (Simopoulos, 2002) were easily reached in both the grass and the grass–legume fed cattle. The fatty acid profile of the beef is mostly diet dependent, while genotype effects for instance on the n 6:n 3 ratio are likely to be minor as can be seen from the study of Rule, Broughton, Shellito, and Maiorano (2002) where differences between beef cattle and bisons were negligible compared to those between grazing and feedlot fattening. Accordingly, there are large differences when comparing grass-fed vs. grain-fed cattle (Dannenberger, NuernRule berg, Nuernberg, & Ender, 2006; Descalzo et al., 2005; et al., 2002), and even the simple supplementation of grass with fibrous soybean hulls was found to be unfavourable in this respect (Baublits et al., 2006). In comparison with grain-finished cattle, Descalzo et al. (2005) reported that TBARS of the tenderloin of pasture-fed cattle was lower, probably due to the high contents of a-tocopherol and other vitamins in the grass and, consequently, in the beef. The TBARS level of about 0.1 mg/kg found by Descalzo et al. (2005) was also lower than that found in the fresh beef of the present pasture-fed cattle. Still, Baublits et al. (2006) found a significantly more frequent occurrence of grassy off-flavour in beef of unsupplemented grass-fed animals compared with those supplemented with soybean hulls. This off-flavour is likely due to the correspondingly higher contents of n 3 fatty acids.

4.2. Effect of legume inclusion into Guinea grass swards grazed by Thai native cattle The basic hypothesis to be tested in the present experiment was that including legumes into a tropical low-quality grass pasture would improve the nutritional status of the animals and thus influence carcass and meat quality. While an increased metabolic protein supply would enhance muscle accretion, an improved energy supply (e.g. via an improved dietary fibre utilisation by removing the limitation in ruminally available nitrogen given in the low-protein grass; Broderick, 2003) might increase body fat accretion and would result in higher carcass fatness, intramuscular fat content and, maybe associated with that, cholesterol content of the beef. Inclusion of the legume into the sward actually increased kidney fat proportion in the carcasses and intramuscular fat content, but not muscle accretion, suggesting that the treatment had an extra energetic effect rather than supplying extra metabolic protein. Similarly, extra energy was found to increase carcass fatness in Thai native cattle (Phaowphaisal & Wijitphan, 2006). The observation of concomitantly elevated intramuscular fat and cholesterol contents, as found here with legume inclusion into grassonly diets, is consistent with responses to other dietary factors (e.g., Rule et al., 2002). Fraser, Speijers, Theobald, Fychan, and Jones (2004) reported that fattening lambs grazing a legume (red clover) pasture instead of a ryegrass pasture had slightly higher dressing percentages. This was different from the present findings, but can be explained with the concomitantly increased daily gains in the study of Fraser et al. (2004). In the present study, there was no increase in proportion of lean and of valuable cuts when offering the legume in addition to the grass. By contrast, supplementing with extra energy is often found to increase lean accretion in those grazing cattle which are in a metabolic status that does not completely exploit the growth potential (Baublits et al., 2004; Steen, Lavery, Kilpatrick, & Porter, 2003). Still, an improved metabolic protein supply with legume inclusion cannot be totally excluded in the present study as the lack of live weight differences at the same slaughter age indicates that the genetic growth potential seems to have been completely exploited with grazing in both forms. Additionally, typical adult weights of 300–350 kg (Wannapat, 2004) had been reached at slaughter, and Phaowphaisal and Wijitphan (2006) also noted only a minor response of Thai native cattle to improved protein supply. Body fat accretion is frequently assumed to be associated with higher beef tenderness; however, the validity of this statement is weakened by including results into this consideration which are confounded with other factors such as age. Koohmaraie and Geesink (2006) therefore concluded that this relationship might be less close than assumed. Anyway, shear force of the LD and the ST of the grass–legume fed cattle was (non-significantly) superior to that found in the grass-only fed cattle, which was consistent with the differences (P < 0.1) noted in the sensory impression of tenderness. Muscle fibre diameter was clearly larger in the grass–legume fed cattle in all muscles and in most fibre types investigated. Since fibre diameter is expected to be negatively correlated with shear force, this may have prevented an even clearer improvement of shear force and sensory impression of tenderness. However, the effect of including the legume into the sward on muscle fibre diameter at quite constant muscle sizes is difficult to explain. Muscle fibre type profile is strongly genetically regulated which is why it is not surprising that there was no effect of feeding. Collagen properties were likely to respond only in case of clear age differences at slaughter, which was not the case. Also other studies investigating the effect of supplementation to grazing described only small variations in shear force (Baublits et al., 2006; Razminowicz, Kreuzer, Leuenberger, & Scheeder, 2008), collagen properties (Santos-Silva,

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Mendes, & Bessa, 2002) and muscle fibre types and diameter (Picard, Lefaucheur, Berri, & Duclos, 2002; Vestergaard et al., 2000). Meat quality traits related to water-holding capacity, including pH and conductivity, remained widely unaffected by the dietary treatment as was expected from the fact that these traits are almost exclusively determined by genotype, by handling of the animals at slaughter and by post-slaughter treatment, factors which were kept constant in the present investigation. Consistent with this, feeding measures were found to be of little importance in other studies with grazing animals (Baublits et al., 2006; Dannenberger et al., 2006; Kerth, Braden, Cox, Kerth, & Rankins, 2007; Varela et al., 2004). The sensory impression of juiciness is determined by water-holding capacity and the fat content of the meat. It remains unclear why the meat from the grass–legume fed cattle, with a similar water-holding capacity and a higher intramuscular fat content, was judged to be less juicy than the beef from the grass-only fed cattle unless, unexpectedly, the water content of the beef played a role, too. Also others did not report significant effects of either pasture type (Fraser et al., 2004) or supplementary feeding (Baublits et al., 2006; Kerth et al., 2007) on beef juiciness. Another phenomenon found was the lighter meat of the grass– legume fed cattle. This seems to have resulted from a less red meat, although a* was only numerically different between groups. There was no difference in fibre colour type proportions, only in fibre diameter. Therefore, the extra intramuscular fat could have been responsible for this effect (Dannenberger et al., 2006). Alternatively, a lower iron incorporation into the beef when consuming legumes is possible. Baublits et al. (2004) found that supplementing soyhull pellets to cattle grazing orchard grass and tall fescue increased beef lightness, but also yellowness. Kim et al. (2003) found that the LD of Hanwoo cattle, slaughtered in summer and winter, had higher pH but a lower L* value than of those slaughtered in fall and spring. This indicates that seasonal variations in sward composition could be of importance, too. Forage legumes fed in combination to grass are known to significantly affect the fatty acid profile of the milk but this effect is smaller than the influence of substituting diets based on either maize or concentrate or both by grass (Van Dorland et al., 2008). Red, and especially white, clover were clearly beneficial by decreasing the n 6:n 3 fatty acid ratio in milk even though the clover lipids are not necessarily superior to the grass in that respect (Dewhurst et al., 2006; Van Dorland et al., 2008). Scollan et al. (2006) found that increasing levels of red clover substituting ryegrass may result in a significant decline of the n 6:n 3 ratio of the beef. By contrast, Fraser et al. (2004) found a higher n 6:n 3 ratio in fattened lambs grazing on either red clover or lucerne instead of ryegrass. Similarly, Thapra stylo offered together with Purple Guinea grass elevated the n 6:n 3 ratio in the present study, corresponding to the small differences found in the fatty acid profile of the forages. However, this change was small and values were still far below the threshold of <5:1 (e.g., DACH, 2000). The variations in fatty acid profile were also small enough to avoid any change in susceptibility to oxidation as measured through TBARS. It remains open whether the reported beneficial effect of the clovers was due to their specific properties including a higher passage rate and specific plant secondary compounds (Dewhurst et al., 2006), making them exceptional in their favourable effect on the fatty acid profile of animal foods.

5. Conclusions Thai native cattle steers grazing tropical grass pastures and slaughtered at an age of 3 years yield beef of sufficient quality with respect to water-holding capacity and tenderness, and offers a desirable fatty acid profile. Improving the grass pasture with a

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tropical forage legume seems not to have pronounced effects on carcass and meat quality. The few effects noted were both of a desired (higher intramuscular fat content, lighter meat and trend towards more tender beef) and an undesired nature (higher carcass fatness, more cholesterol, lower juiciness and higher n 6:n 3 ratio), thus giving none of the alternatives a clear advantage over the other. Acknowledgements The Alexander von Humboldt Foundation is highly acknowledged for providing a grant to the first author. We owe thanks to Thumrongsakd Phonbumrung and Cheerawat Khemsawat from the Department of Livestock Development, Ministry of Agriculture and Cooperation, Royal Thai Government for providing the beef samples. References Abell, L. L., Brodie, B. B., & Kendall, F. E. (1951). A simplified method for the estimation of total serum cholesterol in serum and demonstration of its specificity. Journal of Biological Chemistry, 195, 357–366. Angkuro, S. (2003). Beef cattle situation. In Thai beef cattle: Development and the impact of free trade agreement (pp. 1–9). Asia Hotel, Bangkok, Thailand. AOAC (Association of Official Analytical Chemists) (1995). Official methods of analysis (15th ed.). Arlington, VA, USA. AOAC (Association of Official Analytical Chemists) (1996). Official methods of analysis (15th ed.). Arlington, VA, USA. Baublits, R. T., Brown, A. H., Pohlman, F. W., Johnson, Z. B., Onks, D. O., Loveday, H. D., et al. (2004). Carcass and beef color characteristics of three biological types of cattle grazing cool-season forages supplemented with soyhulls. Meat Science, 68, 297–303. Baublits, R. T., Brown, A. H., Pohlman, F. W., Rule, D. C., Johnson, Z. B., Onks, D. O., et al. (2006). Fatty acid and sensory characteristics of beef from three biological types of cattle grazing cool-season forages supplemented with soyhulls. Meat Science, 72, 100–107. Boufaïed, H., Chouinard, P. Y., Tremblay, G. F., Petit, H. V., Michaud, R., & Bélanger, G. (2003). Fatty acids in forages. I. Factors affecting concentrations.. Canadian Journal of Animal Science, 83, 501–511. Broderick, G. A. (2003). Effects of varying dietary protein and energy levels on the production of lactating dairy cows. Journal of Dairy Science, 86, 1370–1381. Brooke, M. H., & Kaiser, K. K. (1970). Muscle fibre types: How many and what kind? Archives of Neurology, 23, 369–379. Church, P. N., & Wood, J. M. (1991). The manual of manufacturing meat quality. Essex, UK: Elsevier Science Publishers Ltd.. 285 p. DACH (German, Austrian and Swiss Societies of Nutrition) (2000). Referenzwerte für die Nährstoffzufuhr. Frankfurt/Main: Umschau Braus. Dannenberger, D., Nuernberg, K., Nuernberg, G., & Ender, K. (2006). Carcass and meat quality of pasture vs concentrate fed German Simmental and German Holstein bulls. Archives of Animal Breeding, 49, 315–328. Descalzo, A. M., Insani, E. M., Biolatto, A., Sancho, A. M., García, P. T., Pensel, N. A., et al. (2005). Influence of pasture or grain-based diet supplemented with vitamin E on antioxidant/oxidative balance of Argentine beef. Meat Science, 70, 35–44. Dewhurst, R. J., Shingfield, K. J., Lee, M. R. F., & Scollan, N. D. (2006). Increasing the concentrations of beneficial polyunsaturated fatty acids in milk produced by dairy cows in high-forage systems. Animal Feed Science and Technology, 131, 168–206. DLD (Department of Livestock Development) (2004). Economic data of import meat and meat product in 2003. Bangkok, Thailand: Ministry of Agriculture and Cooperative Royal Thai Government. Folch, J., Lees, M., & Stanley, G. H. S. (1957). A simple method for the isolation and purification of total lipids from animal tissue. Journal of Biological Chemistry, 226, 497–509. Fraser, M. D., Speijers, M. H. M., Theobald, V. J., Fychan, R., & Jones, R. (2004). Production performance and meat quality of grazing lambs finished on red clover, lucerne or perennial ryegrass swards. Grass and Forage Science, 59, 345–356. Goering, H. K., & van Soest, P. J. (1970). Forage fibre analysis handbook. Washington, USA (No. 379): USDA Agricultural Research Service. Hess, H. D., Monsalve, L. M., Lascano, C. E., Carulla, J. E., Díaz, T. E., & Kreuzer, M. (2003). Supplementation of a tropical grass diet with forage legumes and Sapindus saponaria fruits: Effects on in vitro ruminal nitrogen turnover and methanogenesis. Australian Journal of Agricultural Research, 54, 703–713. Hill, F. (1966). The solubility of intramuscular collagen in meat animals of various ages. Journal of Food Science, 31, 161–166. Honikel, K. O. (1987). How to measure the water-holding capacity of meat? Recommendation of the standardized method. In G. Eikelenboom, P. V. Tarrant, & G. Monin (Eds.), Evaluation and control of meat quality in pigs (pp. 129–142). The Hague, The Netherland: Martinus Nijhoff Publishers.

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