Quality of three muscles from suckler bulls finished on concentrates and slaughtered at 16 months of age or slaughtered at 19 months of age from two production systems.

There is a requirement in some beef markets to slaughter bulls at under 16 months of age. This requires high levels of concentrate feeding. Increasing the slaughter age of bulls to 19 months facilitates the inclusion of a grazing period, thereby decreasing the cost of production. Recent data indicate few quality differences in longissimus thoracis (LT) muscle from conventionally reared 16-month bulls and 19-month-old bulls that had a grazing period prior to finishing on concentrates. The aim of the present study was to expand this observation to additional commercially important muscles/cuts. The production systems selected were concentrates offered ad libitum and slaughter at under 16 months of age (16-C) or at 19 months of age (19-CC) to examine the effect of age per se, and the cheaper alternative for 19-month bulls described above (19-GC). The results indicate that muscles from 19-CC were more red, had more intramuscular fat and higher cook loss than those from 16-C. No differences in muscle objective texture or sensory texture and acceptability were found between treatments. The expected differences in composition and quality between the muscles were generally consistent across the production systems examined. Therefore, for the type of animal and range of ages investigated, the effect of the production system on LT quality was generally representative of the effect on the other muscles analysed. In addition, the data do not support the under 16- month age restriction, based on meat acceptability, in commercial suckler bull production.

The effects of graded levels of concentrate supplementation on colour and lipid stability of beef from pasture finished late-maturing bulls.

Finishing late-maturing bulls on grass may alter the antioxidant/prooxidant balance leading to beef with higher susceptibility to lipid oxidation and a lower colour stability compared to bulls finished on cereal concentrates. In this context, lipid oxidation and colour stability of beef from late-maturing bulls finished on pasture, with or without concentrate supplements, or indoors on concentrate was assessed. Charolais or Limousin sired bulls (n = 48) were assigned to four production systems: (1) pasture only (P), (2) pasture plus 25% dietary DM intake as barley-based concentrate (PC25), (3) pasture plus 50% dietary DM intake as barley-based concentrate (PC50) or (4) a barley-based concentrate ration (C). Following slaughter and postmortem ageing, M. Longissimus thoracis et lumborum was subjected to simulated retail display (4°C, 1000 lux for 12 h out of 24 h) for 3, 7, 10 and 14 days in modified atmosphere packs (O2 : CO2; 80 : 20). Lipid oxidation was determined using the 2-thiobarbituric acid-reactive substances assay; α-tocopherol was determined by HPLC; fatty acid methyl esters were determined using Gas Chromatography. Using a randomised complete block design, treatment means were compared by either ANOVA or repeated measures ANOVA using the MIXED procedure of SAS. Total polyunsaturated fatty acid (PUFA) concentrations were not affected by treatment, n-3 PUFAs were higher (P < 0.001) and the ratio of n-6 to n-3 PUFAs was lower (P < 0.001) in muscle from P, PC25 and PC50 compared to C. α-Tocopherol concentration was higher in muscle from P compared to PC50 and C bulls (P = 0.001) and decreased (P < 0.001) in all samples by day 14. Lipid oxidation was higher in muscle from C compared to P bulls on day 10 and day 14 of storage (P < 0.01). Finishing on pasture without supplementation did not affect beef colour stability and led to lower lipid oxidation, possibly due to the higher α-tocopherol concentration compared to concentrate finished beef.

Review: Modulating ruminal lipid metabolism to improve the fatty acid composition of meat and milk. Challenges and opportunities.

Growth in demand for foods with potentially beneficial effects on consumer health has motivated increased interest in developing strategies for improving the nutritional quality of ruminant-derived products. Manipulation of the rumen environment offers the opportunity to modify the lipid composition of milk and meat by changing the availability of fatty acids (FA) for mammary and intramuscular lipid uptake. Dietary supplementation with marine lipids, plant secondary compounds and direct-fed microbials has shown promising results. In this review, we have compiled information about their effects on the concentration of putative desirable FA (e.g. c9t11-CLA and vaccenic, oleic, linoleic and linolenic acids) in ruminal digesta, milk and intramuscular fat. Marine lipids rich in very long-chain n-3 polyunsaturated fatty acids (PUFA) efficiently inhibit the last step of C18 FA biohydrogenation (BH) in the bovine, ovine and caprine, increasing the outflow of t11-18:1 from the rumen and improving the concentration of c9t11-CLA in the final products, but increments in t10-18:1 are also often found due to shifts toward alternative BH pathways. Direct-fed microbials appear to favourably modify rumen lipid metabolism but information is still very limited, whereas a wide variety of plant secondary compounds, including tannins, polyphenol oxidase, essential oils, oxygenated FA and saponins, has been examined with varying success. For example, the effectiveness of tannins and essential oils is as yet controversial, with some studies showing no effects and others a positive impact on inhibiting the first step of BH of PUFA or, less commonly, the final step. Further investigation is required to unravel the causes of inconsistent results, which may be due to the diversity in active components, ruminant species, dosage, basal diet composition and time on treatments. Likewise, research must continue to address ways to mitigate negative side-effects of some supplements on animal performance (particularly, milk fat depression) and product quality (e.g. altered oxidative stability and shelf-life).

The effect of plant sterol-enriched turkey meat on cholesterol bio-accessibility during in vitro digestion and Caco-2 cell uptake.

This study evaluated the effect of a plant sterol-enriched turkey product on cholesterol bio-accessibility during in vitro digestion and cholesterol uptake by Caco-2 monolayers. Turkey products, one plant sterol-enriched (PS) and one plant sterol-free (C), were produced in an industrial pilot plant. Before simulated digestion, matrices were spiked with cholesterol (1:5 weight ratio of cholesterol to plant sterol). Plant sterols were included at a concentration equivalent to the minimum daily intake recommended by the European Food Safety Authority (EFSA) for cholesterol lowering. After simulated digestion, the percentage of cholesterol micellarization and uptake by Caco-2 cells in the presence of PS meat were measured. Compared to C meat, PS meat significantly inhibited cholesterol micellarization on average by 24% and Caco-2 cell accumulation by 10%. This study suggests that plant sterols in meat can reduce cholesterol uptake by intestinal epithelia and it encourages efforts to make new PS-based functional foods.

Comparison of organoleptic quality and composition of beef from suckler bulls from different production systems.

Bull beef production is traditionally based on high concentrate rations fed indoors. Inclusion of grazed grass, which is generally a cheaper feed, would decrease the cost of bull beef production, but may affect beef quality. Accordingly, the organoleptic quality and composition of beef from continental-sired suckler bulls (n=126) assigned to either ad libitum concentrates to slaughter (C), grass silage (GS) ad libitum for 120 days followed by C (GSC) or GS followed by 100 days at pasture and then C (GSPC) and slaughtered at target carcass weights (CW) of 360, 410 or 460 kg was examined. Tenderness, flavour liking and overall liking were lower (P<0.05) for GSPC than for C and GSC. Intramuscular fat content and soluble collagen proportion were lower (P<0.05) for GSPC than GSC which was lower (P<0.05) than C. Soluble collagen proportion was lower (P<0.05) for 460 kg than 410 kg CW, which was lower (P<0.05) than 360 kg CW. Inclusion of a grazing period decreased the ratings of tenderness, flavour liking and overall liking, but age of the bulls at slaughter had no clear influence on sensory characteristics.

Biochemical and organoleptic characteristics of muscle from early and late maturing bulls in different production systems.

In grass-based beef production systems (PS), early maturing (EM) breed types may be preferable to late maturing (LM) breed types in achieving adequate carcass fat cover. Biochemical and organoleptic characteristics of muscle from suckler bulls were investigated in EM and LM (n=28/breed) assigned to one of two PS (ad libitum concentrates and grass silage to slaughter (C) or ad libitum silage plus 2 kg concentrate daily during winter followed by 99 days at pasture and then an indoor finishing period on C (GSPC)) in a 2 breed type×2 PS factorial arrangement of treatments. Bulls were managed to have a common target carcass weight of 380 kg. Intramuscular fat (IMF) content was higher (P<0.05) for EM than LM, and for C than GSPC bulls. Collagen solubility was higher (P<0.05) for C than GSPC bulls. Lactate dehydrogenase (LDH) and phosphofructokinase activities were higher (P<0.05) for LM than EM. Isocitrate dehydrogenase activity and the Type I myosin heavy chain (MyHC) proportion were higher (P<0.05) for EM than LM. The LDH activity and the Type IIX MyHC proportion were higher (P<0.05) for C than GSPC bulls. Sensory ratings for tenderness and juiciness were higher (P<0.01) for beef from EM than LM while sensory ratings for tenderness, flavour liking and overall liking were higher (P<0.001) for C than for GSPC bulls. Differences in sensory quality were largely eliminated when adjusted for IMF. Overall, carcass fat scores, IMF and sensory scores were higher in EM than LM and in C than GSPC bulls but most differences in sensory quality could be attributed to differences in IMF.

Quality of deli-style turkey enriched with plant sterols.

Low-fat meat products could be excellent carriers for plant sterols, known for their cholesterol-lowering properties. In this study, we developed a protocol for the manufacture of a deli-style turkey enriched with plant sterols (S) at a level sufficient to deliver the maximum plant sterols amount recommended for cholesterol reduction by the European Food Safety Authority (3 g of plant sterols per day) in a 70 g portion. We investigated the stability of the plant sterols and the effects of their addition on the product quality. Plant sterols remained stable during the seven-day storage period. The addition of plant sterols significantly affected some texture parameters, shear force, lipid oxidation, L values and water-holding capacity compared with control (C). Sensory analysis was carried out by an untrained panel (32) using the difference-from-control test between C and S samples to evaluate first the extent of the overall sensory difference and then the extent of sensory difference on colour, texture and flavour. Results indicated that panellists considered the intensity of the difference between C and S samples to be 'small'. Plant sterols could be used as a potential health-promoting meat ingredient with no effect on plant sterol stability but with some effects on texture and sensory characteristics.

Isotopic composition of sheep wool records seasonality of climate and diet.

RATIONALE: Hair keratin is a very important material in ecological and archaeological studies because it grows continuously, can be obtained non-invasively, does not require extensive processing prior to analysis and can be found in archaeological sites. Only a few studies have examined seasonal variations in hair isotope values, and there is no published dataset examining the isotope variability recorded in the keratinous tissues of stationary (i.e., non-migrating) domestic mammals. METHODS: Thirty-six Irish sheep were sampled in eight farms every three months between September 2006 and June 2007. A shearing strategy was adopted to sample only the most recently grown wool in order to represent an average of the summer, autumn, winter and spring conditions. The stable isotope ratios of the ground samples were measured using two different stable isotope mass spectrometers operated in dual-inlet (C, N) and continuous-flow (O, H) mode. RESULTS: Wool O isotope ratios are a good proxy for seasonal variability in climate and can be used to anchor a chronology independently of other isotope records (C, N) that are influenced by diet or physiology. By contrast, interpretation of seasonal variations in hair H isotope composition in terms of climate is more complex probably due to the influence of dietary H. The C and N isotope values of grass-fed animals varied seasonally, probably reflecting the annual cycle of seasonal variation in grass isotope values. The highest δ(13) C values were measured in summer-grown wool, while the highest δ(15) N values were measured in winter-grown wool. Supplementation of the sheep diet with concentrates was detected easily and was marked by an increase in δ(13) C values and a decrease in δ(15) N values in winter-grown wool. CONCLUSIONS: The present study demonstrates that time-resolved sampling and stable isotope ratio analysis of sheep wool can be used to identify short-term changes in diet and climate and therefore offer a tool to examine a wide variety of present and past husbandry practices.

Dietary olive cake reduces the oxidation of lipids, including cholesterol, in lamb meat enriched in polyunsaturated fatty acids.

Over 40 days, lambs were fed: concentrate (C), concentrate containing 20% linseed (L), concentrate containing 35% olive cake (OC), or concentrate containing 10% linseed and 17% olive cake (OCL). The polyunsaturated fatty acids (PUFA) and peroxidation index (PI) in phospholipids were increased by the L and OCL treatments (P=0.007 and P=0.003, respectively). The OC and OCL diets increased the concentration of tocopherol in muscle (P<0.001). Compared to the OC and OCL diet, the L diet increased fatty acid oxidation, measured as conjugated dienes (CD; P=0.003), peroxides (PV; P<0.001) and TBARS (P=0.002) in minced muscle over 11 days of storage in high-oxygen atmosphere. Also, the L diet increased (P<0.001) the levels cholesterol oxidation products (COPs). In conclusion, feeding olive cake improved the oxidative stability of lamb meat and the combination of olive cake and linseed improved the fatty acid composition of meat without compromising its oxidative stability.

Lipid and colour stability of M. longissimus muscle from lambs fed camelina or linseed as oil or seeds.

Colour and lipid stability of M. longissimus dorsi (LD) from sheep fed diets containing different lipid sources (Megalac (MG), camelina oil (CO), linseed oil (LO), NaOH-treated camelina seed (CS), NaOH-treated linseed (LS) or CO treated with ethanolamine (CA)) were examined. After 100 days on-feed, samples of LD were collected, fatty acid profile determined and colour and lipid oxidation (2-thiobarbituric acid reactive substances; TBARS) measured during retail display in high oxygen packaging. The LS ration was most effective in increasing the 18:3n-3 and conjugated linoleic acid (CLA) concentration in muscle. Within camelina, CA resulted in the highest 18:3n-3 and lowest CLA concentration in muscle. There was no difference in colour stability. Oil (seed) supplementation increased TBARS compared to MG in the early part of display while linseed-based rations tended to cause higher TBARS than camelina-based rations. Higher muscle 18:3n-3 concentration was associated with higher oxidation during early retail display but this was not reflected in a loss of colour stability.

Authentication of beef production systems using a metabolomic-based approach.

There is a need for new, non-invasive, rapid and reliable analytical methodologies that can easily be implemented and used for authentication of cattle production systems and the meat derived from them. Easily quantifiable markers could strengthen the current tracing methods for beef authentication. This study investigated the use of a nuclear magnetic resonance-based metabolomic approach as a tool to authenticate beef on the basis of the pre-slaughter production system. Urine and muscle samples were collected from animals fed either pasture outdoor, a barley-based concentrate indoor, silage followed by pasture outdoor or silage followed by pasture outdoor with concentrate over 1 year. A metabolomic analysis was performed on urine (n = 68) and muscle (n = 98) samples collected from animals on the different diets. The results showed that separation according to production system was possible indicating the potential use of this approach in beef authentication. Identification of the major discriminating peaks in urine led to the identification of potential markers of production system including creatinine, glucose, hippurate, pyruvate, phenylalanine, phenylacetylglycine and three unassigned resonances.

Sulphur isotopes in animal hair track distance to sea.

Stable sulphur isotope ratios ((34)S/(32)S) in animal tissues have been suggested as a tracer of coastal residency of terrestrial animals, but data are lacking that quantify the inland range of the sulphur coastal signal and the effects of seasonality. Here, we present δ(34)S measurements of sheep wool collected seasonally on eight farms across Ireland and wool samples collected opportunistically along the west and east coasts. We observed large (>10‰) δ(34)S differences across the island and we show that wool δ(34)S values were negatively correlated with distance to the west coast. We propose that this is due to the predominantly (south-)westerly airflow, possibly combined with the influence of anthropogenic sulphur deposited from the east. While essentially all the sulphur contained in west-coast wool is of marine origin, relatively high δ(34)S values were still measured >100 km inland, suggesting that marine sulphur can be carried over long distances. Seasonal variations are small at the individual level for sedentary grazing animals. We conclude that sulphur isotopes ratios measured in archival keratinous tissues can be used to describe regional δ(34)S isoscapes primarily defined by distance to coasts and thus provide a tool to detect short-term movements of domestic, feral and wild animals within such isoscapes.

Vitamin E and polyunsaturated fatty acids in bovine muscle and the oxidative stability of beef from cattle receiving grass or concentrate-based rations.

The present study was designed to assess the balance between antioxidant and prooxidant components and the oxidative stability of beef from cattle fed exclusively grazed pasture (PAS) or a barley-based concentrate offered indoors (CONC) for 11 mo, or fed grass silage indoors for a 5-mo winter period, followed for the remaining 6-mo summer period by grazed pasture (SiP) or by grazed pasture plus concentrate at 50% of the dietary DM (SiPC). Muscle prooxidant and antioxidant components were determined by measuring fatty acids and α-tocopherol concentration of LM, respectively. Lipid oxidation and color stability were monitored in ground LM, packaged in a high-oxygen modified atmosphere, over 11 d of refrigerated storage. Vitamin E concentration decreased (P < 0.0005) with an increasing proportion of concentrate in the diet (2.59, 2.45, 1.76, and 1.15 µg/g for PAS, SiP, SiPC, and CONC, respectively). A greater proportion of PUFA was found in LM from cattle in the PAS, SiP, and SiPC groups compared with animals in the CONC group (9.62, 11.04, 8.96, and 6.94%, respectively; P < 0.0005). A greater concentration of highly peroxidizable PUFA was found in LM from heifers in the PAS, SiP, and SiPC groups compared with those in the CONC group (0.84, 0.85, 0.87, and 0.65 mg/g of muscle, respectively; P = 0.02). Dietary treatment affected lipid oxidation (P < 0.0005), with greater 2-thiobarbituric acid reactive substance values in beef from heifers in the SiPC group than in beef from those in the PAS, SiP, and CONC groups. Dietary treatment affected myoglobin oxidation (P = 0.002) during storage, with greater metmyoglobin accumulation in beef from animals receiving concentrate (CONC and SiPC treatments) than in beef from cattle in the PAS and SiP groups. Consequently, feeding concentrate impaired meat color stability over the storage duration, with greater H* (hue angle) values (P < 0.0005) in meat from heifers in the SiPC and CONC groups compared with meat from those in the PAS and SiP groups. The results of the present study confirm a positive effect of grass-based feeding systems on meat color stability compared with concentrate-based dietary strategies. It appears that vitamin E in muscle alone does not explain the resistance of meat to oxidative deterioration because a clear interaction with highly peroxidizable PUFA exists.

Carotenoid, colour and reflectance measurements in bovine adipose tissue to discriminate between beef from different feeding systems.

Our hypothesis was that carotenoids in bovine subcutaneous adipose tissue (SAT) together with colour and reflectance spectra could be used to differentiate between beef production systems based on grass, concentrates or combinations thereof. SAT was sampled from the carcasses of heifers fed pasture (P), a barley-based concentrate (C), silage followed by pasture (SiP) or silage followed by pasture with concentrate (SiPC). ß-carotene in the SAT from the C group (0.09 µg g(-1)) was lower (P<0.05) than that from the P (0.54 µg g(-1)), SiP (0.49 µg g(-1)) and SiPC (0.49 µg g(-1)) groups. Lutein in the SAT differed (P<0.05) between all groups with 0.13, 0.10, 0.08 and 0.04 µg g(-1) for the P, SiP, SiPC and C groups, respectively. Principal component analysis of the carotenoid data, SAT colour variables ['L', 'a', 'b', 'C', 'H'] and the reflectance data made it possible to distinguish between the animals fed a barley-based concentrate diet and the animals fed pasture-based diets, but not between different pasture-based groups.

The fatty acid profile of muscle and adipose tissue of lambs fed camelina or linseed as oil or seeds.

The objective of this study was to evaluate the impact of diets enriched with plant oils or seeds, high in polyunsaturated fatty acids (PUFA), on the fatty acid profile of sheep intramuscular and subcutaneous adipose tissue (SAT). Sixty-six lambs were blocked according to initial body weight and randomly assigned to six concentrate-based rations containing 60 g fat/kg dry matter from different sources: (1) Megalac (MG; ruminally protected saturated fat), (2) camelina oil (CO), (3) linseed oil (LO), (4) NaOH-treated camelina seed (CS), (5) NaOH-treated linseed (LS) or (6) CO protected from ruminal saturation by reaction with ethanolamine; camelina oil amides (CA). The animals were offered the experimental diets for 100 days, after which samples of m. longissimus dorsi and SAT were collected and the fatty acid profile determined by GLC. The data were analyzed using ANOVA with 'a priori' contrasts including camelina v. linseed, oil v. NaOH-treated seeds and CS v. CA. Average daily gain and total fatty acids in intramuscular adipose tissue were similar across treatments. The NaOH-treatment of seeds was more effective in enhancing cis-9, trans-11 conjugated linoleic acid (CLA) incorporation than the corresponding oil, but the latter resulted in a higher content of trans-11 18:1 in both muscle neutral and polar lipids (P < 0.01, P < 0.001, respectively). Inclusion of LS resulted in the highest PUFA:saturated fatty acid (SFA) ratio in total intramuscular fat (0.22). The NaOH-treatment of seeds resulted in a higher PUFA/SFA ratio (0.21 v. 0.18, P < 0.001) than oils and on average, linseed resulted in a higher PUFA/SFA ratio than camelina (P < 0.01). Lambs offered LS had the highest concentration of n-3 PUFA in the muscle, while those offered MG had the lowest (P < 0.001). This was reflected in the lowest (P < 0.001) n-6: n-3 PUFA ratio for LS-fed lambs (1.15) than any other treatment, which ranged from 2.14 to 1.72, and the control (5.28). The trends found in intramuscular fat were confirmed by the data for SAT. This study demonstrated the potential advantage from a human nutrition perspective of feeding NaOH-treated seeds rich in PUFA when compared to the corresponding oil. The use of camelina amides achieved a greater degree of protection of dietary PUFA, but decreased the incorporation of biohydrogenation intermediates such as cis-9, trans-11 CLA and trans-11 18:1 compared to NaOH-treated seeds.

An evaluation of over-wintering feeding strategies prior to finishing at pasture for cull dairy cows on live animal performance, carcass and meat quality characteristics.

Fifty-six spring calving Holstein-Friesian dairy cows (body weight=607 kg and body condition score=2.75), destined for culling, were randomly assigned to one of four experimental treatments. Cows were confirmed non-pregnant by rectal palpation. The experiment was split into two periods: over-wintering period (OWP) and spring finishing period (SFP). Animals were assigned to one of four treatments: a control group (C) was slaughtered after am milking on day 0; three dietary treatments, two of which were dried pre-experiment; ad libitum grass silage (GS+G); 75% grass silage and 25% straw (GS+S); and one with the extended lactation concept applied, cows were offered grass silage plus 6 kg concentrate DM/cow/day and milked twice daily (EXTLAC). EXTLAC cows were dried-off 1 week prior to turnout. The OWP lasted 84 days. Subsequent to the OWP cows were turned out to pasture (SFP). All cows were finished to a pre-defined carcass specification; >272 kg cold carcass weight, P+carcass conformation class and 3 carcass fat class. Over the entire experimental period, average daily gain (ADG) was lower (P<0.001) for the EXTLAC treatment compared with the two other dietary treatments. The GS+G treatment finished 33 and 38 days (P<0.001) earlier than the GS+S and EXTLAC treatments, respectively. Total feed utilized on a DM basis was 1.9, 2.0 and 2.5 tonnes/cow for the GS+G, GS+S and EXTLAC dietary treatments, respectively. All finishing treatments resulted in a significant improvement in carcass weight, as well as carcass quality traits, compared to the C group. A significant improvement occurred in muscle redness between the C group and treatments offered a finishing period prior to slaughter.

Lipid and colour stability of meat from lambs fed fresh herbage or concentrate.

Fourteen male Comisana lambs were divided into two groups at 45days of age and were individually penned for 105days. Over this period, seven lambs were fed a concentrate-based diet (C), whereas the remaining animals received vetch (Vicia sativa; H) harvested daily and given fresh to the animals. Lipid oxidation was measured in both minced cooked meat (semimembranosus muscle, SM) over 4days of aerobic refrigerated storage and on minced raw meat stored over 14days in a high oxygen atmosphere. Colour descriptors, haem pigment concentration, and metmyoglobin percentages were also determined during storage duration on the minced raw meat. Lipid oxidation increased over time in cooked and raw meat (P<0.0005), but lower TBARS values were found in both cooked and minced meat from lambs fed vetch compared to those given concentrates (P=0.001; P=0.006, respectively). Higher a* values, lower b* values and lower hue angle values were observed in meat from H-fed animals as compared to meat from C-fed lambs (P=0.006; P=0.02; P=0.005, respectively). Metmyoglobin formation increased over time (P<0.0005), but the H diet resulted in lower metmyoglobin percentages than the C diet (P=0.006). Haem pigment concentration decreased over the 14days of storage (P<0.0005). We conclude that, under conditions that promote oxidative stress in meat, a herbage-based diet can improve the oxidative stability of meat compared to a concentrate-based diet.

Turnover of carbon, nitrogen, and sulfur in bovine longissimus dorsi and psoas major muscles: Implications for isotopic authentication of meat.

Stable isotope ratio analysis of light elements (including C, N, and S) is a powerful tool for inferring the production and geographic origins of animals. The objectives of this research were to quantify experimentally the isotopic turnover of C, N, and S in bovine skeletal muscle (LM and psoas major) and to assess the implications of the turnover for meat authentication. The diets of groups (n = 10 each) of beef cattle were switched from a control diet containing barley and unlabelled urea to an experimental diet containing maize, (15)N-labeled urea, and seaweed for periods of up to 168 d preslaughter. The feeding of the experimental diet was clearly reflected by the delta(13)C, delta(15)N, and delta(34)S values of the LM and psoas major muscles, but isotopic equilibrium was not reached in either muscle for C, N, or S after 168 d of feeding the experimental diet. The slow turnover in skeletal muscle was reflected by the C and N half-lives of 151 and 157 d for LM and 134 and 145 d for psoas major, respectively, and by an S half-life of 219 d in LM. It is concluded that the turnover of light elements (C, N, and S) in bovine skeletal muscles is a slow process; therefore, skeletal muscles contain isotopic information on dietary inputs integrated over a long period of time (months to years).

Colour of bovine subcutaneous adipose tissue: A review of contributory factors, associations with carcass and meat quality and its potential utility in authentication of dietary history.

The colour of bovine subcutaneous (sc) adipose tissue (carcass fat) depends on the age, gender and breed of cattle. Diet is the most important extrinsic factor but its influence depends on the duration of feeding. Cattle produced under extensive grass-based production systems generally have carcass fat which is more yellow than their intensively-reared, concentrate-fed counterparts and this is caused by carotenoids from green forage. Although yellow carcass fat is negatively regarded in many countries, evidence suggests it may be associated with a healthier fatty acid profile and antioxidant content in beef, synonymous with grass feeding. Nonetheless, management strategies to reduce fat colour of grass-fed cattle are sought after. Current research suggests that yellow colour of this tissue is reduced if pasture-fed cattle are converted to a grain-based diet, which results in accretion of adipose tissue and dilution of carotenoids. Colour changes may depend on the initial yellow colour, the carotene and utilisable energy in the finishing diet, the duration of finishing, the amount of fat accumulated during finishing and the rate of utilisation of carotene from body fat. Differences in nutritional strategies which cause differences in fatty acid composition may be reflected by differences in fat colour and carotenoid concentration. Fat colour and carotenoids are prominent among a panoply of measurements which can aid the authentication of the dietary history and thus to some extent, the origin of beef, although this potential utility is complicated by the simultaneous rather than discrete use of forages and concentrates in real production systems.

Effect of grass silage and concentrate based finishing strategies on cull dairy cow performance, carcass and meat quality characteristics.

Sixty-eight spring calving Holstein-Friesian dairy cows on completion of lactation were randomly assigned to one of four dietary treatments. The experiment commenced on 17th December 2005 and was completed on 27th June 2006. Pre-experimental live weight and BCS were 605kg (s.d. 68.9) and 2.7 (s.d 0.28), respectively. The four treatments were: ad-lib grass silage (GS), GS+3kg concentrate (GS+3), GS+6kg concentrate (GS+6) and GS+9kg concentrate (GS+9). All cows were finished to a live weight>620kg and a BCS>3.5. Live animal, carcass and meat quality characteristics were measured. Mean (s.d.) total feed utilized was similar, at 1.5 (0.05) tonnes DM/cow across all treatments. There was a linear (P<0.001) increase in ADG (kg/day) for the first three dietary treatments, GS (0.71), GS+3 (0.91), GS+6 (1.14) with no additional response to the final increment, GS+9 (1.15). As concentrate proportion in the diet increased there was a linear decrease (P<0.001) in days to slaughter. Cows on the GS+9 treatment (84 days) finished on average 12, 25 and 38 days earlier than those on the GS+6, GS+3, and GS treatments. The GS+9 treatment had lower carcass fat yellowness ('b' value) than the GS treatment but the GS+3 and GS+6 treatments did not differ from either GS or GS+9. There was no effect of treatment (P>0.05) on muscle redness ('a' value) following exposure to oxygen. When cull cows are finished to pre-defined slaughter criteria, similar carcass classifications and carcass quality can be achieved with diets ranging from GS to GS+9, however significant difference in physical performance and days to slaughter will result.