Visible spectroscopy on lamb fat and muscle to authenticate the duration of pasture finishing.

Pasture-based livestock systems are considered environmentally-sustainable and welfare-friendly farming systems that can meet consumer demand for good-quality produce. However, trust in products labelled as 'grass-fed' depends on the ability to reliably authenticate pasture origin. The two objectives of this study were (i) to test the ability of visible spectroscopy combined with discriminant analysis on lamb perirenal fat (PF), dorsal fat (DF) and longissimus thoracis et lumborum muscle to discriminate different durations of pasture-finishing; and (ii) to determine the timing of appearance of the pasture signature and its stabilization in these tissues. Four groups of 35 lambs were used over two years, i.e. lambs fed concentrate in-stall (L0) and lambs grazing alfalfa for 21d (L21), 42d (L42) and 63d (L63) before slaughter. No one tissue satisfactorily discriminated the four treatment groups, with ≤75% of lambs correctly classified. However, visible spectroscopy discriminated L0 from L21 + L42 + L63 lambs with an accuracy of 92.8%, 92.0%, and 85.3% lambs correctly classified on PF, DF and muscle, respectively, and discriminated L0 + L21 from L42 + L63 lambs with an accuracy of 90.1%, 76.5% and 92.3% on PF, DF and muscle, respectively. The pasture fingerprint or signature on the spectrum appeared in most lambs between 0 and 21d in PF and DF and between 0 and 42d in muscle. Pasture signature gradually stabilized with increasing time on pasture but was not entirely stabilized in any tissue within the range of grazing durations explored. These promising results need to be confirmed on larger datasets with different breeds and grazing conditions.

Review: On-farm and processing factors affecting bovine carcass and meat quality.

This paper reviews the current state of knowledge on beef carcass and meat quality, with particular emphasis on on-farm and processing factors associated with its high and inconsistent variability. The diversity of livestock systems comes from the diversity of breeds (dairy or beef), ages and gender (bulls, steers, heifers, cull cows) used to produce either mainly beef or beef and milk. In addition, there are factors linked to farming practices (including diet, especially grazing) which significantly influence the sensory, nutritional, technological and extrinsic (such as image) quality attributes of meat. These can become factors of positive differentiation when controlled by the application and certification of technical specifications. Finally, preslaughter (such as stress), slaughter (such as the chilling and hanging method of carcasses) and postslaughter (such as ageing, packaging and cooking) conditions have a strong influence on the microbiological, sensory, technological and image quality attributes of beef. In this review, potential synergisms or antagonisms between the different quality attributes are highlighted. For example, finishing cattle on grass, compared to indoor fattening on a high concentrate diet, has the advantage of producing leaner meat with a higher proportion of omega-3 fatty acids while exhibiting superior oxidative stability, but with the consequence of a darker meat colour and lower productivity, as well as higher seasonality and land surface requirements. Moreover, the control of on-farm factors is often guided by productivity (growth rate, feed conversion ratio) and carcass quality attributes (weight, conformation and fatness). Genetic selection has often been oriented in this direction, without taking other quality attributes into account. Finally, the interactions between all these factors (and especially between on-farm and slaughter or processing factors) are not considered in the quality grading schemes in European countries. This means that positive efforts at farm level may be mitigated or even eliminated by poor slaughtering or processing conditions. All these considerations explain why between-animal variability in quality can be high, even when animals come from the same farming system. The ability to predict the sensory and nutritional properties of meat according to production factors has become a major objective of the supply chain.

Review: Quality of animal-source foods.

This article critically reviews the current state of knowledge on the quality of animal-source foods according to animal production and food processing conditions, including consumer expectations-behaviours and the effects of consumption of animal-source foods on human health. Quality has been defined through seven core attributes: safety, commercial, sensory, nutritional, technological, convenience, and image. Image covers ethical, cultural and environmental dimensions associated with the origin of the food and the way it is produced and processed. This framework enabled to highlight the priorities given to the different quality attributes. It also helped to identify potential antagonisms and synergies among quality attributes, between production and processing stages, and among stakeholders. Primacy is essentially given to commercial quality attributes, especially for standard commodity animal-source foods. This primacy has strongly influenced genetic selection and farming practices in all livestock commodity chains and enabled substantial quantitative gains, although at the expense of other quality traits. Focal issues are the destructuration of chicken muscle that compromises sensory, nutritional and image quality attributes, and the fate of males in the egg and dairy sectors, which have heavily specialised their animals. Quality can be gained but can also be lost throughout the farm-to-fork continuum. Our review highlights critical factors and periods throughout animal production and food processing routes, such as on-farm practices, notably animal feeding, preslaughter and slaughter phases, food processing techniques, and food formulation. It also reveals on-farm and processing factors that create antagonisms among quality attributes, such as the castration of male pigs, the substitution of marine-source feed by plant-based feed in fish, and the use of sodium nitrite in meat processing. These antagonisms require scientific data to identify trade-offs among quality attributes and/or solutions to help overcome these tensions. However, there are also food products that value synergies between quality attributes and between production and processing phases, particularly Geographical Indications, such as for cheese and dry-cured ham. Human epidemiological studies have found associations between consumption of animal-source foods and increased or decreased risk for chronic non-communicable diseases. These associations have informed public health recommendations. However, they have not yet considered animal production and food processing conditions. A concerted and collaborative effort is needed from scientists working in animal science, food process engineering, consumer science, human nutrition and epidemiology in order to address this research gap. Avenues for research and main options for policy action are discussed.

Review: Factors affecting sheep carcass and meat quality attributes.

Sheep meat comes from a wide variety of farming systems utilising outdoor extensive to indoor intensive with animals of various ages at slaughter. In Europe, slaughter may occur from 4 weeks of age in suckling light lambs to adult ages. More than any other animal species used for meat production, there are strong country-specific preferences for sheep meat quality linked to production system characteristics such as dairy or grassland-based systems. This article critically reviews the current state of knowledge on factors affecting sheep carcass and meat quality. Quality has been broken down into six core attributes: commercial, organoleptic, nutritional, technological, safety and image, the latter covering aspects of ethics, culture and environment associated with the way the meat is produced and its origin, which are particularly valued in the many quality labels in Europe. The quality of meat is built but can also deteriorate along the continuum from the conception of the animal to the consumer. Our review pinpoints critical periods, such as the gestation and the preslaughter and slaughter periods, and key factors, such as the animal diet, via its direct effect on the fatty acid profile, the antioxidant and volatile content, and indirect effects mediated via the age of the animal. It also pinpoints methodological difficulties in predicting organoleptic attributes, particularly odour and flavour. Potential antagonisms between different dimensions of quality are highlighted. For example, pasture-feeding has positive effects on the image and nutritional attributes (through its effect on the fatty acid profile of meat lipids), but it increases the risk of off-odours and off-flavours for sensitive consumersand the variability in meat quality linked to variability of animal age at slaughter. The orientation towards more agro-ecological, low-input farming systems may therefore present benefits for the image and nutritional properties of the meat, but also risks for the commercial (insufficient carcass fatness, feed deficiencies at key periods of the production cycle, irregularity in supply), organoleptic (stronger flavour and darker colour of the meat) and variability of sheep carcass and meat quality. Furthermore, the genetic selection for lean meat yield has been effective in producing carcasses that yield more meat, but at a penalty to the intramuscular fat content and eating quality of the meat, and making it more difficult to finish lambs on grass. Various tools to assess and predict quality are in development to better consider the various dimensions of quality in consumer information, payment to farmers and genetic selection.

Review: Quality and authentication of organic animal products in Europe.

The 'organic' label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises the use of veterinary drugs; however, consumers are demanding guarantees regarding food quality. This article reviews the current state of knowledge on the quality of organic animal products, including the authentication of their organic origin. Quality has been considered as an integrative combination of six core attributes: commercial value, and nutritional, sensory, technological, convenience and safety attributes. The comparison of these attributes between organic and conventional animal products shows high heterogeneity due to variability in farming pratices in both organic and conventional systems. To overcome this, we pinpoint the farming practices underlying the differences observed. This enables light to be shed on the consequences of possible trajectories of organic farming, if specifications are relaxed or tightened up on commitments concerning farming practices that impact product quality. Two recent meta-analyses showed better nutritional attributes in organic milk and meat linked to their higher poly-unsaturated fatty acid (PUFA) content, particularly n-3 PUFAs. Regarding safety, we point to a lack of integrated studies quantifying the balance between positive and negative effects. Organic farming reduces the risk of drug residues and antibiotic resistance, but both outdoor rearing and a frequently longer rearing period increase the animals' exposition to environmental contaminants and the risk of their bioaccumulation in milk, eggs, meat and fish flesh. We highlight antagonisms between quality attributes for certain animal products (lamb, pork). In general, attributes are more variable for organic products, which can be explained by lower genetic selection (poultry), lower inputs and/or greater variability in farming conditions. However, the literature does not address the implications of this greater variability for the consumers' acceptability and the necessary adaptation of manufacturing processes. Further research is needed to document the impacts on human nutritional biomarkers and health. Methods used to authenticate organic origin are based on differences in animal diet composition between organic and conventional systems, but their reliability is hampered by the variability in farming practices.

Construction of beef quality through official quality signs, the example of Label Rouge.

The European Union promotes high-quality food products and protects agricultural traditions. With that vision, Regulation (EU) 1151/2012 defines quality schemes such as protected designations of origin, protected geographical indications and optional quality terms that link quality and tradition to legal labels. These quality schemes are completed by national initiatives. Label Rouge is an official regulated sign of premium quality in France that explicitly aims at higher product quality. Each Label Rouge product has to comply with production and processing conditions stated in its published specifications. Here, we analyse commitments made under Label Rouge books of specifications for beef to show how the Label Rouge quality-sign constructs quality. In order to provide a frame, product quality has been broken down into a set of seven quality attributes: commercial, organoleptic, nutritional, safety, technological, convenience and image-value, where image-value quality attributes encompass the ethical, cultural and environmental dimensions associated with how a food is produced and processed, and its origin. The specifications highlight 'communicative certified characteristics' (characteristics set out in the specifications that are certified and communicated to the public) and specify how the meat needs to be farmed and processed to attain superior quality. Analysis of all 16 Label Rouge books of specifications for beef, based on scientific expertise and the literature, showed that commitments in these specifications are linked to the seven groups of quality attributes and that they concern the whole continuum of the chain, from animal type to on-farm conditions, transport to slaughter and through to meat ageing. Commitments concerning the whole herd and the selection of label-eligible animals, carcasses and meat particularly enhance organoleptic and image-value attributes. Label Rouge builds quality through commitments on the production, transport and beef ageing conditions, and offers a strong referent for the beef sector on how to better meet more qualitative consumers' expectations.

Review: Authentication of grass-fed meat and dairy products from cattle and sheep.

Meat and dairy products derived from grassland carry premium values and sensory and nutritional qualities that aroused much interest for authentication methods to guarantee grassland origin claims. This article reviews the current state of knowledge on the authentication of meat and dairy of grassland origin from food analysis in both cattle and sheep. A range of methods alone or combined, involving analysis of elemental or molecular constituents of food product and fingerprinting profiling combined with chemometrics, have been developed and proved useful to differentiate contrasted feeding regimes and authenticate grass-fed meat and dairy. Their robustness and discriminatory reliability in more complex feeding conditions, such as in the case of dietary switches or when grass only makes up part of the animal's diet, are under active investigation. Our review highlights the possibilities and limitations of these methods, the latter being chiefly posed by variations in the quantity, characteristics and composition of grassland feedstuffs consumed by animals, which are nevertheless inherent to grassland-based production systems, variations in animal responses within and across breeds, and difficulties in detecting the consumption of non-grass feedstuffs by the animal. It also highlights a number of issues for consideration, points of caution and caveats in applying these methods. Scientists agree that much of the research carried out so far has been a 'proof of concept' type and that efforts should be made in the future to develop more databases to help gain genericity and robustness.

Comparison of muscle fatty acid composition and lipid stability in lambs stall-fed or pasture-fed alfalfa with or without sainfoin pellet supplementation.

Currently, consumers are increasingly interested in obtaining high-quality and healthy lamb meat. Compared to grain-based diets, dietary forage legumes such as alfalfa and condensed tannin (CT)-rich sainfoin increase the levels of polyunsaturated fatty acids (PUFAs) that are beneficial for health in lamb meat thanks to their high content in PUFA and/or their impact on ruminal biohydrogenation. However, they can therefore adversely affect its oxidative stability. Thus, the impact of dietary forage legumes on lamb longissimus thoracis (LT) muscle FA composition and their stability to peroxidation was studied in 36 Romane lambs grazing alfalfa (AF; n = 12) or alfalfa plus daily supplementation with CT-rich sainfoin pellets (AS; n = 12; 15 g DM/kg BW, 42 g CT/kg DM) or stall-fed concentrate and grass hay indoors (SI; n = 12). Lambs were slaughtered at a mean age of 162 ± 8.0 days after an average experimental period of 101 ± 8.1 days. Forage legumes-grazing lambs outperformed SI lambs in LT nutritional quality, with more conjugated linoleic acids and n-3 PUFAs, especially 18:3n-3, eicosapentaenoic and docosahexaenoic acids (P < 0.001), and thus lower n-6 PUFA/n-3 PUFA and 18:2 n-6/18:3 n-3 ratios (P < 0.001). Peroxidizability index was higher (P < 0.001) in LT muscle of forage legumes-grazing lambs. Concurrently, two endogenous antioxidant enzyme activities, superoxide dismutase and glutathione peroxidase, were, respectively, similar and lower (P < 0.001) for forage legumes-grazing compared with SI lambs. A lower vitamin E level in SI lambs compared with forage legumes-grazing lambs (1.0 v. 3.8 mg/g, P < 0.001) could explain that malondialdehyde content, a marker of lipid oxidation intensity, was 0.63 µg/g in SI after 8 days in aerobic packaging conditions, whereas it remaining steady at 0.16 µg/g in forage legumes-grazing lambs. Dietary forage alfalfa thus improved FA composition of lamb LT muscle and their stability to oxidation when compared to SI lambs. However, supplementation of alfalfa-grazing lambs with CT-rich sainfoin pellets did not affect the nutritional quality of LT muscle FAs.

Reliability of visible reflectance spectroscopy in discriminating between pasture and stall-fed lambs from thin and fat-tailed sheep breeds in dry and hot environment.

Considering the additional market value of pasture meat, many authentication methods were developed to discriminate it from meat produced in conventional systems. The visible reflectance spectroscopy technique has proved its efficiency under European conditions and breeds. The present study tested the reliability of this method to discriminate between pasture-fed (P) and stall-fed (S) lambs under North African conditions and investigated the effect of feeding system (FS) (P v. S) and breed (Barbarine; Queue Fine de l'Ouest; and Noire de Thibar) on weight and colour of perirenal, subcutaneous and caudal fat. A total of 18 P and 18 S lambs were used with 6 P and 6 S lambs for each breed. The colour and the reflectance spectrum of different fat tissues were measured. The FS affected weights of all fat tissues and all colour parameters of perirenal and subcutaneous fat (P ≤ 0.01); it almost affected redness and yellowness of caudal fat (P ≤ 0.05; P ≤ 0.01). In all adipose tissues, lightness was higher and both redness and yellowness were lower for S lambs than P lambs. The breed affected weight, lightness and redness of perirenal fat and weight and redness of subcutaneous fat with significant interaction with FS for subcutaneous fat data. To discriminate P lambs from S lambs, the reflectance spectrum of perirenal, subcutaneous and caudal fat at wavelengths between 450 and 510 nm (Method 1, M1) or at wavelengths between 400 and 700 nm using partial least squares discriminative analysis as a classification method (Method 2, M2) were used. M2 yielded to a higher proportion of correctly classified lambs compared with M1 (P = 0.001). The proportion of correctly classified lambs using M2 was 76.4, 75.0 and 80.0% for perirenal, subcutaneous and caudal fat for P lambs and 83.3, 76.4 and 100.0% for S lambs. Despite lower reliability in comparisons to European researches, this study confirmed the efficiency of visible reflectance spectroscopy technique applied on perirenal fat in feeding systems authentication under North African conditions and spotted the caudal fat as a new support for better classification of fat-tailed breeds.

Tannin-rich sainfoin pellet supplementation reduces fat volatile indoles content and delays digestive parasitism in lambs grazing alfalfa.

Lambs grazing alfalfa or white clover are prone to flavour taint which can be an impediment to consumer acceptance. Here we investigated whether condensed tannin (CT)-rich sainfoin pellet supplementation of lambs grazing alfalfa influences meat sensory quality. Using three groups of 18 male Romane weaned lambs, we compared three feeding regimes: alfalfa grazing (AF), alfalfa grazing + daily supplementation with CT-rich sainfoin pellets (15 g dry matter (DM)/kg live weight, AS) and stall feeding with concentrate and grass hay indoors (SI). We also investigated the potential interest of sainfoin pellet supplementation for controlling digestive parasitism. The sainfoin pellets contained 42 g of CT/kg of DM and they represented on average 36% of the diet in AS lambs. Skatole and indole were detected in most of the AF and AS lambs, whereas in very few SI lambs. Skatole and indole concentrations in perirenal and dorsal fat were lower in the AS lambs than the AF lambs (P < 0.025 to P < 0.001), but the intensity of 'animal' odour and 'animal' flavour of the chops did not differ between both forage-grazing groups. Longissimus thoracis et lumborum muscle lightness was lower in the AF and AS lambs than the SI lambs (P < 0.001) with the other muscle colour coordinates being unaffected by the treatment and between-treatment group differences in muscle colour coordinates remaining constant throughout the 9-day display period. Subcutaneous fat colour coordinates were not influenced by the treatment. The number of individual anthelmintic drenches necessary to keep nematode faecal egg count below a threshold of 550 eggs/g of faeces was lower in the AS than the AF lambs (0.94 per lamb v. 1.63 per lamb; P < 0.001). Faecal oocyst count was lower in the AS than the AF lambs for the first measurement made 56 days after the beginning of the experiment (P < 0.001) and was not significantly different between both forage-grazing groups thereafter. The use of CT-rich sainfoin pellets to supplement lambs that are concurrently grazing alfalfa reduced fat volatile skatole and indole concentrations and delayed the onset of both helminth and coccidian infections.

How does barley supplementation in lambs grazing alfalfa affect meat sensory quality and authentication?

Excessive flavour in lamb meat is undesirable for consumers and can prompt purchase resistance. Volatile indoles responsible for off-flavours accumulate more in the fat of lambs on pasture than on grain and are enhanced when lambs graze alfalfa. Here, we investigated whether barley supplementation of lambs grazing alfalfa influences meat sensory quality. Using three groups of 12 male Romane lambs, we compared three feeding regimes: alfalfa grazing (AG), alfalfa grazing + daily supplementation with barley (29 g/kg live weight0.75, AGS) and stall feeding with concentrate and hay (SF). As some of the compounds involved in meat sensory traits may act as dietary biomarkers, we also investigated potential implications for meat authentication. Although barley represented 38% of the diet in AGS lambs, it did not offer any advantage for animal average daily gain or parasitism level. Animal performance, carcass weight and fatness did not differ between feeding regimes. Dorsal fat firmness tended to be greater in AG than AGS and greater in AGS than SF. Skatole and indole concentrations in perirenal and dorsal fat were lower in SF lambs than in AG and AGS lambs (P<0.01 to P<0.0001), but did not differ between AG and AGS lambs. Yellowness, chroma and hue angle of perirenal fat were lower in SF lambs than in AG and AGS lambs (P<0.001), but did not differ between AG and AGS lambs. Absolute value of the mean integral for both perirenal fat and subcutaneous caudal fat (AVMIPF and AVMISC), quantifying the intensity of light absorption by carotenoids in perirenal and subcutaneous caudal fat, respectively, were lower in SF lambs than in AG and AGS lambs (P<0.0001 for both comparisons), but did not differ between AG and AGS lambs. Meat colour was unaffected by the treatment. We confirm that lambs grazing alfalfa accumulate high levels of volatile indoles in their fat, but we show that barley supplementation to lambs grazing alfalfa is not effective in reducing fat volatile indoles concentration and excessive odour/flavour in the meat. We also confirm that both perirenal fat skatole concentration and AVMIPF are of interest for discriminating lambs that grazed alfalfa from lambs that were stall-fed, and we show that they are not effective for discriminating supplemented from non-supplemented grazing lambs.

To what extent is a breed-specific database necessary to differentiate meat from pasture-fed and stall-fed lambs using visible spectroscopy?

Carotenoid pigments signature in the fat using visible reflectance spectroscopy has shown high potential for distinguishing pasture-fed (P) from stall concentrate-fed (S) lamb carcasses. However, a recent study demonstrated a between-breed variability in the digestive and metabolic fate of carotenoids pigments. The present study was therefore designed to investigate the extent to which this between-breed variability may affect the reliability of diet authentication using visible spectroscopy of the fat. We used 1054 male lambs from three breeds (Romane (ROM), Ile-de-France (OIF) and Limousine (LIM)). The breed-feed breakdown was 148 P and 258 S ROM, 102 P and 92 S OIF and 168 P and 286 S LIM lambs. The reflectance spectrum of perirenal fat was measured at 24 h postmortem at wavelengths between 400 and 700 nm. We quantified light absorption in the 450 to 510 nm area by calculating a traceability index (AVMI 450 to 510) considered as an indicator of the carotenoid concentration in the fat (method 1) and we performed a multivariate analysis over the full set of reflectance data between 400 and 700 nm (method 2). The reliability of method 1 proved very variable across breeds, with a percentage of correctly classified lambs reaching 95.3%, 90.5% and 79.4% in ROM, LIM and OIF lambs, respectively. Despite these between-breeds differences, the threshold of the linear discriminant analysis performed on AVMI 450 to 510 was fairly similar between breeds; when all the data for the three breeds were pooled, the threshold cut-off value was 224 units and the method correctly classified 90.2% of the 1054 lambs. Using the full range of reflectance data (method 2) enabled to significantly increase the proportion of correctly classified lambs for both OIF and LIM breeds, but not for ROM breed. It enabled to correctly classify 96.1%, 94.5% and 94.8% of the ROM, LIM and OIF lambs. The reliability of the discrimination was not significantly different when pooling all lambs for the three breeds than when using a breed-specific database (93.9% and 95.2%, respectively).

Comparison of visible and near infrared reflectance spectroscopy on fat to authenticate dietary history of lambs.

Since consumers are showing increased interest in the origin and method of production of their food, it is important to be able to authenticate dietary history of animals by rapid and robust methods used in the ruminant products. Promising breakthroughs have been made in the use of spectroscopic methods on fat to discriminate pasture-fed and concentrate-fed lambs. However, questions remained on their discriminatory ability in more complex feeding conditions, such as concentrate-finishing after pasture-feeding. We compared the ability of visible reflectance spectroscopy (Vis RS, wavelength range: 400 to 700 nm) with that of visible-near-infrared reflectance spectroscopy (Vis-NIR RS, wavelength range: 400 to 2500 nm) to differentiate between carcasses of lambs reared with three feeding regimes, using partial least square discriminant analysis (PLS-DA) as a classification method. The sample set comprised perirenal fat of Romane male lambs fattened at pasture (P, n = 69), stall-fattened indoors on commercial concentrate and straw (S, n = 55) and finished indoors with concentrate and straw for 28 days after pasture-feeding (PS, n = 65). The overall correct classification rate was better for Vis-NIR RS than for Vis RS (99.0% v. 95.1%, P < 0.05). Vis-NIR RS allowed a correct classification rate of 98.6%, 100.0% and 98.5% for P, S and PS lambs, respectively, whereas Vis RS allowed a correct classification rate of 98.6%, 94.5% and 92.3% for P, S and PS lambs, respectively. This study suggests the likely implication of molecules absorbing light in the non-visible part of the Vis-NIR spectra (possibly fatty acids), together with carotenoid and haem pigments, in the discrimination of the three feeding regimes.

Visible spectroscopy on carcass fat combined with chemometrics to distinguish pasture-fed, concentrate-fed and concentrate-finished pasture-fed lambs.

We used visible spectroscopy of fat to discriminate lambs that were pasture-fed (n=76), concentrate-fed (n=79) or concentrate-finished after pasture-feeding (n=69). The reflectance spectrum of perirenal and subcutaneous caudal fat was measured at slaughter and 24h post mortem. In Method 1 (W450-510), the optical data were used at wavelengths in the range of 450-510nm to calculate an index quantifying light absorption by carotenoids. In Method 2 (W400-700), the full set of data at wavelengths in the range of 400-700nm was used to differentiate carcasses using PLS-DA as a classification method. W400-700 proved more reliable than W450-510 (P<0.0001). The proportion of correctly classified lambs using W400-700 was 95.6% and 95.9% for measurements made on perirenal fat at slaughter and 24h post mortem. The intensity of light absorption by carotenoids decreased exponentially with live weight gain during the finishing period.

Influence of fresh alfalfa supplementation on fat skatole and indole concentration and chop odour and flavour in lambs grazing a cocksfoot pasture.

We investigated the influence of the level of fresh alfalfa supplementation on fat skatole and indole concentration and chop sensory attributes in grazing lambs. Four groups of nine male Romane lambs grazing a cocksfoot pasture were supplemented with various levels of alfalfa for at least 60days before slaughter. Perirenal fat skatole concentration was higher for lambs that consumed alfalfa than for those that consumed only cocksfoot. The intensity of 'animal' odour in the lean part of the chop and of 'animal' flavour in both the lean and fat parts of the chop, evaluated by a trained sensory panel, increased from the lowest level of alfalfa supplementation onwards and did not increase further with increasing levels of alfalfa supplementation. The outcome of this study therefore suggests that these sensory attributes may reach a plateau when perirenal fat skatole concentration is in the range 0.16-0.24µg/g of liquid fat.

Dose-dependent response of nitrogen stable isotope ratio to proportion of legumes in diet to authenticate lamb meat produced from legume-rich diets.

This study investigated the dose-dependent response in lamb meat of stable nitrogen isotope ratio to the dietary proportion of legumes, and the ability of the nitrogen isotope signature of the meat to authenticate meat produced from legume-rich diets. Four groups of nine male Romane lambs grazing a cocksfoot pasture were supplemented with different levels of fresh alfalfa forage to obtain four dietary proportions of alfalfa (0%, 25%, 50% and 75%) for 98 days on average before slaughter (groups L0, L25, L50 and L75). We measured the stable nitrogen isotope ratio in the forages and in the longissimus thoracis muscle. The δ(15)N value of the meat decreased linearly with the dietary proportion of alfalfa. The distribution of the δ(15)N values of the meat discriminated all the L0 lambs from the L75 lambs, and gave a correct classification score of 85.3% comparing lambs that ate alfalfa with those that did not.

Influence of level of barley supplementation on plasma carotenoid content and fat spectrocolorimetric characteristics in lambs fed a carotenoid-rich diet.

This study investigated changes in plasma carotenoid concentration and fat reflectance spectrum characteristics and color in lambs fed a carotenoid-rich diet with low-level (L, 100 g/lamb/day) or high-level (H, 400 g/lamb/day) of barley supplementation for 75 days before slaughter. Each treatment used 24 Romane male lambs that were individually penned indoors. Plasma carotenoid concentration at slaughter was 16% lower in H lambs than in L lambs. H lambs had heavier and fatter carcasses than L lambs. Yellowness and redness of perirenal fat were slightly lower in H lambs than in L lambs. The absolute value of the mean integral (AVMI) calculated from the reflectance spectrum of the fat in the 450-510 nm band was not affected by the treatment. Yellowness, chroma and AVMI of subcutaneous fat were not affected by the treatment but decreased with initial animal's liveweight.

Response of lamb plasma carotenoid concentration to a shift from a low to a high dietary carotenoid level.

This study was conducted to investigate the pattern of plasma carotenoid concentration (PCC) in lambs switching from a low to a high dietary carotenoid level. A total of 12 Romane lambs were individually penned indoors and fed a low dietary carotenoid level for 23 days (period 1) and then a high dietary carotenoid level for 15 days (period 2). At the beginning of period 2, the lambs were 15 weeks old and weighed 29.9 kg (s.d. 2.7) on average. Lambs were fed daily (dry matter) 0.558 kg alfalfa pellets, 0.181 kg straw and 0.181 kg barley. Plasma content of total carotenoids was measured daily in period 2 by spectrophotometry. PCC (µg/l) varied with the animal (P < 0.001) and with time elapsed since the beginning of alfalfa distribution (P < 0.001). Mean PCC was 8 µg/l (s.d. 3.3) at the beginning of period 2, then increased curvilinearly with the time elapsed since the beginning of alfalfa distribution. As early as 24 h on the alfalfa diet, PCC was already higher than before the switch (P < 0.001). Mean PCC continued to increase until day 6 on average and reached a plateau thereafter. We propose a monomolecular function to model this pattern, the equation obtained on the mean data being: PCC = 97 (s.e. 2.2) × (1-exp(-0.3378 (s.e. 0.0282)×d)), where r2 = 0.997, r.s.d. = 4.47, n = 15 and d = day. The percentage of variance explained by the model ranged between 95.9% and 99.2%, depending on the animal. The parameters of the monomolecular function varied among animals, confirming the interindividual variability in animal response. Plateau for PCC was reached slightly earlier for the six lambs with the lowest values of the asymptote than for the six lambs with the highest values of the asymptote.

Fat spectro-colorimetric characteristics of lambs switched from a low to a high dietary carotenoid level for various durations before slaughter.

This study investigated the changes in fat reflectance spectrum characteristics and color in lambs switched from a low to a high dietary carotenoid level for various durations before slaughter. Six treatments, feeding a high dietary carotenoid level for 0, 15, 30, 45, 60 or 75 days before slaughter, were compared in individually indoor penned lambs. Each treatment used 10 Romane lambs; feeding management ensured similar growth pattern and carcass weight for all the treatment groups. There was a change in reflectance spectrum characteristics and yellowness of subcutaneous fat as early as 15 days after the switch. Mean concentration of carotenoid pigments and yellowness of subcutaneous fat increased linearly with the duration of the high dietary carotenoid level. In perirenal fat, the change in reflectance spectrum characteristics was observed as early as 15 days after the switch, but the response to the duration of the high dietary carotenoid level was curvilinear.

Comparison of meat and carcass quality in organically reared and conventionally reared pasture-fed lambs.

The 'Organic' product label guarantees a production process that avoids the use of synthetic fertilisers, pesticides and hormones and minimises recourse to pharmaceuticals or veterinary drugs; however, the product's quality remains an issue that needs to be addressed in response to consumer demand. Consequently, this study was conducted to compare the sensory and nutritional qualities of meat and carcasses from pasture-fed lambs reared organically (O) or conventionally (C). Mean lamb growth profile was kept similar between the two treatments to avoid confounding effects with lamb age or weight at slaughter. The experiment was conducted over 3 years (2005 to 2007) with 12 O and 12 C lambs each year. The O and C treatments differed in the level of on-pasture mineral N fertilisation inducing a higher proportion of white clover in the organic pasture than the conventional pasture. Lambs were slaughtered when they attained a fat class of 2 to 3, and carcass and meat quality were evaluated. Lambs were slaughtered at an average weight and age of 35.3 kg and 156 days in the O treatment, respectively, and 35.2 kg and 155 days in the C treatment, respectively. Sensory evaluation indicated that loin chops from the O treatment had a higher level of abnormal fat odour compared with the C treatment. Carcasses from the O treatment had a softer subcutaneous fat one among 3 years (2007) compared to the C treatment. These results are probably due to a higher proportion of white clover in the diet. Organically reared lambs did offer the slight advantage of muscle fatty acid containing a higher level of stearic acid, which may have positive effects in the prevention of cardiovascular disease in humans. This may be the result of a higher rumen bio-hydrogenation of C18:3n-3 due to differences in the botanical composition between the O and the C pasture. Production system had no effect on the colour characteristics of the meat and subcutaneous fat, except lightness of subcutaneous dorsal fat, which was slightly higher in the O lambs. There were no differences between O and C lambs in terms of colour stability and lipid oxidation of the meat during the 6-day refrigerated storage under gas-permeable film.