Acciaro M.1, Decandia M.1, Sitzia M.1, Manca C.1, Giovanetti V.1, Rassu S.P.G.2, Leiber F.3, Addis M.1, Fiori M.1 and Molle G.1
1AGRIS Sardegna, Loc. Bonassai, 07100 Sassari, Italy; 2Dipartimento di Agraria, Sezione di Scienze Zootecniche, Università di Sassari, viale Italia 39, 07100 Sassari, Italy; 3FiBL Research Institute of Organic Agriculture, 5070 Frick, Switzerland; macciaro@agrisricerca.it
Abstract
To highlight the effects of pasture and hay and concentrate-based diets on α-tocopherol content and fatty acids composition of intramuscular fat of young Sarda bulls at equal growth rate, a study was undertaken.
Twenty-eight animals, homogeneous for live weight (288.7±29.0 kg, mean±s.d.), body condition score (2.69±0.18) and age (355±25 days) were divided into 4 groups: one group (PAS) was fed 24 h day-1 at pasture without supplementation; three groups were confined and fed natural pasture hay ad libitum and an increasing daily dose of concentrates (2.5 kg head-1 HC1, 3.5 kg head-1 HC2, and ad libitum HC3). This paper, part of larger one, only reports the results for group PAS and HC2, which showed an undifferentiated growth rate (PAS 0.75±0.05 and HC2 0.78±0.05 kg head-1 day-1). The pasture-based diet increased (P<0.05) the content (mg g-1 of total lipids) of linolenic acid (22.3±0.8 vs 10.9±0.8, Lsmeans±SE), ω3 (31.9±1.2 vs 19.7±1.2), α-tocopherol (3.9±0.1 vs 2.1±0.1 mg kg-1 of meat), and lowered n-6/n-3 ratio (3.6±0.2 vs 5.9±0.2). The results confirm that pasture can result in a better meat quality with putative benefits for consumers’ health.
Keywords: grazing, cattle, fatty acids, α-tocopherol, local breeds.
Introduction
Due to the high cost of fattening based on concentrates, Sardinian farmers prefer to sell calves at weaning to the fattening centres in the North Italy and this explains the low self-supply rate of beef in Sardinia, which hardly reaches 48%. The use of pasture in the fattening of calves could decrease the feeding costs and improve the meat quality for human health (Daley et al., 2010; Realini et al., 2004). However, in many of these experiments dietary effects are confounded with differences in carcass weight at slaughter or with animal age (French et al., 2000). This happens when animal fed high-energy diets, usually based on grains, are heavier, fatter and younger at slaughter than counterparts fed forage-based diets (Steen et al., 2003). In order to isolate the effects of diet from those of nutrition level on some meat traits of young Sarda bulls, a study was carried out, comparing animals with similar growth rates.
Materials and methods
The study was carried out during 2010 (May-July) at the experimental farm of the Agricultural Research Agency of Sardinia (AGRIS Sardegna) located in Foresta Burgos (latitude 40°25’N, longitude 8°55’E, altitude 850 m a.s.l.). The site is characterized by Mediterranean climate, with minimum and maximum mean temperatures of 1.7 °C (January) and 28.0 °C (July), respectively and average annual rainfall of 905 mm, mostly from November to March. A 7 ha natural pasture based on oak tree forest, manly Quercus pubescens L was grazed by 28 young Sarda bulls, divided into 4 groups (7 heads per group) homogeneous for live weight (LW, 288.7±29.0 kg, mean ± s.d.), Body Condition Score (BCS, 2.69±0.18 five-points scale, Lowman et al., 1976) and age (355±25 days). One group was fed 24 h on pasture (group PAS), without supplementation. The other three groups (HC groups) were kept in roofed pens and fed daily with natural pasture hay (ad libitum) and commercial concentrate at 3 different levels (kg head-1): 2.5 (group HC1), 3.5 (group HC2) and ad libitum (group HC3), offered twice a day. The animals were
slaughtered at fixed age (416±25 days). 24 h post-mortem, samples of Longissimus dorsi were removed between sixth and seventh thoracic vertebrae from each left half-carcass. The α-tocoferol (Vitamin E) content and the fatty acids composition were determined in intra-muscular fat (Addis et al., 2013).
The results reported hereunder refer only to the groups that showed similar growth rates during the experiment (PAS and HC2). These data were analyzed with lme procedure of R using a linear mixed-effects model with diet as fixed effect and animal as random effect.
Results and discussion
PAS and HC2 bulls showed similar LW (PAS 340±9 and HC2 336±9 kg LW, P=0.74) and growth rates (PAS 0.75±0.05 and HC2 0.78±0.05 kg head-1 day-1 P=0.67).
The PAS group showed the higher value of the α-tocopherol content (Table 1), falling in the optimal range to extend the shelf life of retail beef (0.30-0.35 mg 100 g-1 of fresh meat, Geay et al., 2001).
The α-tocopherol plays also a role in preventing coronary heart diseases, hampering the synthesis of nitrosamines (Daley et al., 2010). While intramuscular fat from HC2 was higher in oleic acid; α-linolenic and eicosapentaenoic (EPA) acids were higher in pastured-animals, likely because of the fatty acid composition of the diet. The α-linolenic acid is the major fatty acid in grass lipids (Scollan et al., 2006) and EPA arises from its elongation and desaturation. Both contribute to increase the n-3content, in meat from PAS group, lowering the n-6/n-3 ratio that was below the threshold (n-6/n-3<4) indicated by the Committee on Medical Aspect of Food Policy to prevent some cardiovascular diseases. Unexpectedly, the CLA 9c 11t content was lower in PAS group, mirroring the trend of its precursor, vaccenic acid, which Table 1. The effect of diet on individual fatty acid proportions in intra-muscular fat of Longissimus dorsi at 6th/7th rib and α-tocopherol content of young Sarda bulls. (Lsmeans±SE).1
Fatty acid (mg g-1 total lipid) HC 2 PAS SE P-value2
C16:0 128.48 119.06 5.88 ns
C18:0 137.32 133.64 6.85 ns
C18:1 11t (TVA) 17.38 12.95 1.46 0.05
C18:1 9c oleic acid 162.04 133.88 7.84 0.05
C18:2 9c,12c (linoleic acid) 97.50 97.26 5.49 ns
C18:3 9c,12c,15c (linolenic acid) 10.94 22.35 0.81 0.001
CLA 9c,11t 3.02 1.99 0.21 0.01
C20:4 5c,8c,11c,14c 18.58 18.88 1.60 ns
C20:5 5c,8c,11c,14c,17c EPA 0.26 0.49 0.03 0.001
C22:5 7c,10c,13c,16c,19c DPA 7.96 8.60 0.55 ns
C22:6 4c,7c,10c,13c,16c,19c DHA 0.52 0.54 0.06 ns
SFA 277.16 262.57 13.02 ns
MUFA 179.43 146.83 8.85 0.01
PUFA 139.02 150.33 7.59 ns
UFA 318.45 297.16 4.58 0.01
Σn-3 19.68 31.97 1.25 0.001
Σn-6 116.08 116.14 6.91 ns
Σn-6/Σn-3 ratio 5.92 3.63 0.21 0.001
PUFA/SFA 0.51 0.60 0.06 ns
α-tocoferol (mg kg-1 of meat) 2.11 3.94 0.12 0.001
1 SFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids; UFA = unsaturated fatty acids.
2 ns = P>0.05.
is one of the major intermediates formed during rumen biohydrogenation of C18 polyunsaturated fatty acids (PUFA) (Alfaia et al., 2006). We cannot exclude that PAS diet included species containing plant secondary metabolites (PSM) able to curb PUFA lipolysis and biohydrogenation in the rumen (Cabiddu et al., 2009). Flowers or other species such as some daisy plant can contain other PSM such as terpenes, or complex enzymes such as polyphenol oxidase which can modulate fatty acid metabolism in the rumen (Buccioni et al., 2012).
Conclusions
At similar nutritional level and equal finishing age, the grazing bulls, thanks to the characteristics of the ingested pasture, produced meat of better quality for consumers’ health as compared with that obtained under feedlot conditions. This could result in a greater appreciation of grass-sourced meat by the consumers.
Acknowledgements
The authors are grateful to S. Picconi, A. Pintore, S. Mastinu, Nino Lei, P. Carta together with G. Scanu and all staff of the laboratory.
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