Multilevel meta-analysis and dose-response analysis for bisphenol A (BPA) exposure on metabolic and neurobehavioral effects.

Evidence suggests that oral exposure to bisphenol A (BPA) may result in adverse metabolic and neurobehavioral effects. The aim of the present meta-analysis is to examine this association based on systematically selected laboratory rodent studies published from 2012 to 2021 and sourced from Scopus, Web of Science, EmBase, and PubMed. Articles satisfying eligibility and inclusion criteria were included for the calculation of the summary standardised mean difference (SMD). Subgroup analysis and subsequent dose-response analysis were conducted if applicable. In total, 32 studies were analysed for 6 metabolic endpoints (cholesterol, triglycerides, insulin, glucose, leptin, and adiponectin) and 6 neurobehavioral endpoints (locomotor activity, exploratory, anxiety, depression, spatial learning and memory, non-spatial learning and memory). Summary SMDs implied that no significant effects were observed in endpoints considered. The dose was not determined as a significant moderator with regards to medium or high heterogeneity; however, there was significant impairment of spatial learning and memory at health-based guidance value ('HBGV') (0.05-9 mg (kg bw)-1 day-1) and 'High' (>9 mg (kg bw)-1 day-1) dose group. As a result, an indicative toxicological reference dose value of 0.034 mg (kg bw)-1 day-1 was proposed due to large variability. Potential harm to spatial learning and memory from BPA exposure requires further investigation. This study has provided some additional information on potential adverse metabolic and neurobehavioral effects of BPA from the perspective of meta-analysis which can inform the public, regulatory authorities, and policymakers.

Risk assessment of bisphenol A (BPA) in Irish meat and meat products.

Bisphenol A (BPA) is a chemical with large-scale applications in the manufacturing of industrial products. Concerns have been raised regarding human exposure to BPA and dietary consumption is the main route of exposure. BPA is recognised as an endocrine disruptor with multiple adverse effects on the reproductive, immune, and nervous systems. This study aimed to conduct a probabilistic risk assessment to evaluate the human health risk based on the raw concentration data (N = 1266) of BPA in non-canned meat and meat products purchased from supermarkets and local butchers in Dublin and the surrounding area. The mean exposure levels for BPA in non-canned meat and meat products, fresh meat, and processed meat products among children were 0.019, 0.0022, and 0.015 µg (kg bw)-1 day-1, respectively. Therefore, simulated human exposures to BPA were far below the EFSA recommended current temporary tolerable daily intake (t-TDI) of 4 µg (kg bw)-1 day-1. However recently, the EFSA has proposed a draft TDI of 0.04 ng (kg bw)-1 day-1 to replace the current t-TDI. Hence, our results indicated potential health concerns as the estimated exposure levels (5th-95th percentile) were below current t-TDI but above draft TDIs. Further investigation into the source of BPA contamination in processed meat products is highly recommended. The research presented here will inform the public, meat producers and processors, and policymakers on potential exposure to BPA.

Effect of different botanically-diverse diets on the fatty acid profile, tocopherol content and oxidative stability of beef.

BACKGROUND: Beef from pasture-fed animals is viewed as a healthier and more welfare-friendly alternative to concentrate-fed beef. Botanically-diverse pastures consisting of numerous plant species may alter the fatty acid (FA) profile and the tocopherol content of beef, as well as the oxidative stability of the meat. In the present study, steers were assigned to one of three botanically-diverse diets: perennial ryegrass (PRG), perennial ryegrass + white clover (PRG + WC) or multi-species (MS), all with a finishing diet of the respective botanically-diverse silages plus a cereal-based concentrate, consistent with production systems in Ireland. The FA profile, tocopherol content, oxidative stability and colour of meat during storage were measured. RESULTS: Compared to the other diets, the MS diet resulted in higher proportions of linolenic acid (C18:3n-3c), linoleic acid (C18:2n-6c) and total polyunsaturated fatty acids (PUFA), with higher PUFA:saturated fatty acid and n-6:n-3 ratios in the meat. α-Tocopherol concentrations were lowest in the meat of animals from the MS diet. In uncooked meat, lipid oxidation and colour values were affected by storage time across all diets, whereas the MS diet led to higher hue values only on day 14 of storage. When cooked, meat from animals on PRG + WC and MS diets had higher lipid oxidation on days 1 and 2 of storage than meat from animals on the PRG diet. CONCLUSION: Feeding steers on a botanically-diverse diet consisting of six plant species can improve the n-3 FA and PUFA concentration of beef, affecting the susceptibility of cooked, but not uncooked, beef to oxidation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Hazard characterization of bisphenol A (BPA) based on rodent models - Multilevel meta-analysis and dose-response analysis for reproductive toxicity.

Bisphenol A (BPA) is a widely used synthetic industrial compound frequently detected in food. Dietary exposure to BPA has been recognised as a potential health concern. However, there are uncertainties regarding BPA toxicity. The primary objective of this study was to summarise and analyse multiple toxicity endpoints of adverse reproductive effects caused by BPA exposure in rodent models. Therefore, a multilevel meta-analysis and subsequent dose-response analysis were conducted. Relevant articles published in English between 2012 and 2021 were collected from online databases, viz. Scopus, EmBase, Web of Science, and PubMed. In total, 41 studies were included for statistical analysis. All statistical analyses were performed using open-source RStudio packages. Summary effects indicated the statistical significance of BPA exposure on decreased sperm concentration (Hedges' g: -1.35) and motility (Hedges' g: -1.12) on average, while no significant effects were observed on the absolute and relative weight of male and female reproductive organs. The lowest mean toxicological reference dose values of 0.0011 mg (kg bw)-1 day-1 was proposed for BPA exposure on sperm concentration from the dose-response model. In conclusion, potential health risks from BPA exposure were shown with regards to reproductive toxicity, especially that sperm concentration and sperm motility require further attention.

A probabilistic approach to model bisphenol A (BPA) migration from packaging to meat products.

Bisphenol A (BPA), a synthetic chemical which has raised concerns due to its potential toxicological effects on humans, has been widely detected in canned and non-canned meat and meat products. This study estimated BPA migration from packaging to non-canned and canned meat products by developing two probabilistic models. BPA concentration data in packaging materials were collated, including polyethylene terephthalate, polyvinyl chloride, epoxy-based coatings, and polyester-based coatings. Migration ratios were calculated from migration tests of BPA molecules moving from packaging to food simulants. The predictive model revealed that the BPA migration concentration from packaging ranges from 0.017 to 0.13 (5th-95th percentile) µg kg-1 with a simulated mean of 0.056 µg kg-1 in non-canned meat products. This is in stark contrast to the simulated mean of 134.57 (5th-95th percentile: 59.17-223.25) µg kg-1 for canned meat products. Nevertheless, plastic packaging was estimated to contribute only 3 % of BPA levels in non-canned meat products. The sensitivity analysis showed that the contact area of meat products with films is the most sensitive parameter of the plastic packaging migration model. It is concluded that plastic packaging may not be the only or dominant source of BPA in non-canned meat products.

Yeast ß-Glucan Improves Insulin Sensitivity and Hepatic Lipid Metabolism in Mice Humanized with Obese Type 2 Diabetic Gut Microbiota.

SCOPE: Gut microbiota alterations are associated with obesity and type 2 diabetes. Yeast ß-glucans are potential modulators of the innate immune-metabolic response, by impacting glucose, lipid, and cholesterol homeostasis. The study examines whether yeast ß-glucan interacts differentially with either an obese healthy or obese diabetic gut microbiome, to impact metabolic health through hepatic effects under high-fat dietary challenge. METHODS AND RESULTS: Male C57BL/6J mice are pre-inoculated with gut microbiota from obese healthy (OBH) or obese type 2 diabetic (OBD) subjects, in conjunction with a high-fat diet (HFD) with/without yeast ß-glucan. OBD microbiome colonization adversely impacts metabolic health compared to OBH microbiome engraftment. OBD mice are more insulin resistant and display hepatic lipotoxicity compared to weight matched OBH mice. Yeast ß-glucan supplementation resolves this adverse metabolic phenotype, coincident with increasing the abundance of health-related bacterial taxa. Hepatic proteomics demonstrates that OBD microbiome transplantation increases HFD-induced hepatic mitochondrial dysfunction, disrupts oxidative phosphorylation, and reduces protein synthesis, which are partly reverted by yeast ß-glucan supplementation. CONCLUSIONS: Hepatic metabolism is adversely affected by OBD microbiome colonization with high-fat feeding, but partially resolved by yeast ß-glucan. More targeted dietary interventions that encompass the interactions between diet, gut microbiota, and host metabolism may have greater treatment efficacy.

Human health risk assessment of bisphenol A (BPA) through meat products.

Meat and meat products are often consumed in our daily diet, providing essential nutrients. Contamination by chemical hazards, including bisphenol A (BPA) in meat products, is a concern and is continuously monitored. BPA is well-known for its endocrine-disrupting properties, which may cause potential toxicological effects on reproductive, nervous, and immune systems. Dietary consumption is the main route of BPA exposure, and meat products are a major contributor. BPA exposure from meat consumption is the focus of this review. This review found that BPA has been widely detected in canned and non-canned meat products. BPA in canned meat is assumed to be predominantly from migration from can coatings. Relatively low levels are observed in non-canned products, and the source of contamination in these products has yet to be definitively identified. A recent European Food Safety Authority (EFSA) draft opinion has proposed to lower the tolerable daily intake of BPA from 4 µg kg body weight (bw)-1 day-1 to 0.04 ng kg body weight (bw)-1 day-1, therefore potential health risks need to be addressed. This review has investigated potential contamination at the farm, industrial processes, and retail levels. Data gaps in the literature are also identified to improve future food safety in the meat industry. Also, a unified risk assessment strategy has been proposed. Further understanding of BPA migration in meat products is needed as a part of the exposure assessment to reduce potential risk, and more data on the dose-response relationship will help comprehend potential adverse health effects of BPA on humans. This research will inform the public, meat producers and processing industry, and policymakers on potential exposure to BPA and risk reduction measures, thus, ensuring food safety.

High-Pressure Processing for the Production of Added-Value Claw Meat from Edible Crab (Cancer pagurus).

High-pressure processing (HPP) in a large-scale industrial unit was explored as a means for producing added-value claw meat products from edible crab (Cancer pagurus). Quality attributes were comparatively evaluated on the meat extracted from pressurized (300 MPa/2 min, 300 MPa/4 min, 500 MPa/2 min) or cooked (92 °C/15 min) chelipeds (i.e., the limb bearing the claw), before and after a thermal in-pack pasteurization (F9010 = 10). Satisfactory meat detachment from the shell was achieved due to HPP-induced cold protein denaturation. Compared to cooked or cooked-pasteurized counterparts, pressurized claws showed significantly higher yield (p < 0.05), which was possibly related to higher intra-myofibrillar water as evidenced by relaxometry data, together with lower volatile nitrogen levels. The polyunsaturated fatty acids content was unaffected, whereas the inactivation of total viable psychrotrophic and mesophilic bacteria increased with treatment pressure and time (1.1-1.9 log10 CFU g-1). Notably, pressurization at 300 MPa for 4 min resulted in meat with no discolorations and, after pasteurization, with high color similarity (ΔE* = 1.2-1.9) to conventionally thermally processed samples. Following further investigations into eating quality and microbiological stability, these HPP conditions could be exploited for producing uncooked ready-to-heat or pasteurized ready-to-eat claw meat products from edible crab.

Bisphenol A and Metabolites in Meat and Meat Products: Occurrence, Toxicity, and Recent Development in Analytical Methods.

Bisphenol A (BPA) is a commonly used compound in many industries and has versatile applications in polycarbonate plastics and epoxy resins production. BPA is classified as endocrine-disrupting chemical which can hamper fetal development during pregnancy and may have long term negative health outcomes in humans. Dietary sources, main route of BPA exposure, can be contaminated by the migration of BPA into food during processing. The global regulatory framework for using this compound in food contact materials is currently not harmonized. This review aims to outline, survey, and critically evaluate BPA contamination in meat products, including level of BPA and/or metabolites present, exposure route, and recent advancements in the analytical procedures of these compounds from meat and meat products. The contribution of meat and meat products to the total dietary exposure of BPA ranges between 10 and 50% depending on the country and exposure scenario considered. From can lining materials of meat products, BPA migrates towards the solid phase resulting higher BPA concentration in solid phase than the liquid phase of the same can. The analytical procedure is comprised of meat sample pre-treatment, followed by cleaning with solid phase extraction (SPE), and chromatographic analysis. Considering several potential sources of BPA in industrial and home culinary practices, BPA can also accumulate in non-canned or raw meat products. Very few scientific studies have been conducted to identify the amount in raw meat products. Similarly, analysis of metabolites and identification of the origin of BPA contamination in meat products is still a challenge to overcome.

Comparison of the effects of the intestinal permeation enhancers, SNAC and sodium caprate (C10): Isolated rat intestinal mucosae and sacs.

SNAC and C10 are intestinal permeation enhancers (PEs) used in formulations of peptides for oral delivery in clinical trials. Our aims were to compare their: (i) mechanism of action in isolated rat intestinal mucosae mounted in Ussing chambers and in non-everted gut sacs, (ii) effects on mucosa integrity in those models and also in in situ intra-jejunal instillations and (iii) interactions with intestinal mucus. SNAC increased the apparent permeability coefficient (Papp) of the paracellular marker, FITC-dextran 4000 (FD4), across isolated rat gastric mucosae in concentration-dependent fashion, whereas C10 did not, while both reduced the transepithelial electrical resistance (TEER). In isolated jejunal and colonic mucosae, both agents increased the Papp of [14C]-mannitol and FD4 whereas C10 but not SNAC reduced TEER. 20 mM SNAC was required to achieve the efficacy of 10 mM C10 in jejunal and colonic mucosae. In isolated non-everted jejunal and colonics sacs, FD4 flux increases were observed in the presence of both PEs. Histology of mucosae revealed that both PEs induced minor epithelial damage to the mucosa at concentrations that increased fluxes. Jejunal tissue withstood epithelial damage in the following order: intra jejunal in situ instillations > jejunal sacs > isolated jejunal mucosae. Both PEs modulated viscoelastic properties of porcine jejunal mucus without altering rheological properties. In conclusion, SNAC and C10 are reasonably efficacious PEs in rat intestinal tissue with common overall mechanistic features. Their potency and toxic potential are low, in agreement with clinical trial data.

Effect of Cold Plasma on Meat Cholesterol and Lipid Oxidation.

Cold atmospheric plasma (CAP) is a novel non-thermal technology with potential applications in inactivating microorganisms in food products. However, its impact on food quality is not yet fully understood. The aim of this research is to study the impact of in-package plasma technology on the stability of cholesterol and total lipid in four different types of meat (beef, pork, lamb and chicken breast). Additionally, any changes in the primary or secondary lipid oxidation, which is undesirable from a health perspective, is investigated. CAP was not found to have any impact on the cholesterol or lipid content. However, higher peroxide and thiobarbituric acid reactive substances (TBARS) values were found for the treated samples, indicating that plasma can induce the acceleration of primary and secondary lipid oxidation. Finally, color was not affected by the treatment supporting the suitability of the technology for meat products.

Monitoring the effect of different microwave extraction parameters on the recovery of polyphenols from shiitake mushrooms: Comparison with hot-water and organic-solvent extractions.

The current study aimed to investigate the effect of different microwave-assisted extraction (MAE) parameters (i.e., particle size of the sample, solid-to-liquid ratio, microwave power, and extraction time) on the total phenolic content (TPC), antioxidant capacity (DPPH and CUPRAC), chlorogenic acid and caffeic acid contents of shiitake mushrooms. All the independent variables affected TPC and antioxidant capacity values. Only the sample particle size had no significant effect on phenolic acid contents. The highest TPC, DPPH, and CUPRAC values were obtained when a particle size of 1.75 mm, solid-to-liquid ratio of 1/40, microwave power of 600 W, and extraction time of 15 min were used. The extracts obtained by MAE were compared with those obtained after hot-water extraction (HWE) and organic-solvent extraction (OSE). Scanning electron microscopy (SEM) confirmed that MAE resulted in cell wall disruption which might be due to an increase in the pressure of the inner part of the cells.

A Validated Method for Cholesterol Determination in Turkey Meat Products Using Relative Response Factors.

The objective of this study was to develop a precise and accurate method to quantify cholesterol in turkey meat products using relative response factors, based on a modification of a previously published method for plant sterols determination. Validation was performed using neat solutions to determine linearity, precision, and accuracy. The method was linear in the concentration range considered (1-20 µg/mL, r2 ≥ 0.991). Precision and accuracy were within the acceptability guidelines of the U.S. Food and Drug Administration (FDA) for method validation (<20% relative standard deviation (RSD) at the lower limit of quantification (LLOQ) and <15% RSD for other standards). Turkey meat was spiked with cholesterol at two levels (low = 3 µg/mL and high = 18 µg/mL), either before or after saponification, to establish the recovery and matrix effects. Recovery ranged from 94% to 105%, with a mean value of 105% at the low spike level and 95% at the high spike level. No significant matrix effects were found (90% to 112% recovery). This method is reliable for the quantification of cholesterol in turkey meat products in the range 0.4-8 mg/g.

Shedding Light on the Trehalose-Enabled Mucopermeation of Nanoparticles with Label-Free Raman Spectroscopy.

Nanoparticle-based drug delivery systems have attracted significant interest owing to their promise as tunable platforms that offer improved intracellular release of cargo therapeutics. However, significant challenges remain in maintaining the physiological stability of the mucosal matrix due to the nanoparticle-induced reduction in the matrix diffusivity and promotion of mucin aggregation. Such aggregation also adversely impacts the permeability of the nanoparticles, and thus, diminishes the efficacy of nanoparticle-based formulations. Here, an entirely complementary approach is proposed to the existing nanoparticle functionalization methods to address these challenges by using trehalose, a naturally occurring disaccharide that offers exceptional protein stabilization. Plasmon-enhanced Raman spectroscopy and far-red fluorescence emission of the plasmonic silver nanoparticulate clusters are harnessed to create a unique dual-functional, aggregating, and imaging agent that obviates the need of an additional reporter to investigate mucus-nanoparticle interactions. These spectroscopy-based density mapping tools uncover the mechanism of mucus-nanoparticle interactions and establish the protective role of trehalose microenvironment in minimizing the nanoparticle aggregation. Thus, in contrast to the prevailing belief, these results demonstrate that nonfunctionalized nanoparticles may rapidly penetrate through mucus barriers, and by leveraging the bioprotectant attributes of trehalose, an in vivo milieu for efficient mucosal drug delivery can be generated.

Validation of a Rapid Microwave-Assisted Extraction Method and GC-FID Quantification of Total Branched Chain Fatty Acids in Lamb Subcutaneous Adipose Tissue.

A rapid microwave-assisted extraction and derivatization of three branched chain fatty acids (BCFA): 4-methyloctanoic acid (MOA), 4-ethyloctanoic acid (EOA) and 4-methylnonanoic acid (MNA) from subcutaneous adipose tissue (SAT) of lamb was developed and validated. Linearity was excellent (R2 > 0.99), and the limits of detection and quantification (µg/mL) were between 0.03 to 0.05 and 0.04 to 0.06, respectively. The relative response factors were 0.9416, 1.2840, and 1.0370 determined with high precision (RSD: 5.8%, 6.7%, and 5.9%) for MOA, EOA, and MNA, respectively. The accuracy, recoveries and matrix effect were 92.5% to 108.3%, 103.1% to 103.8%, and 89.3% to 101.9%, respectively. Analysis of 24 SAT samples can be done in under 4 hr. The levels of total BCFA in SAT of lambs were in good agreement with levels found in literature using more time-consuming method. PRACTICAL APPLICATION: Microwave-assisted preparation and quantification of branched chain fatty acids (BCFA) in lamb subcutaneous adipose tissue (SAT) was developed and validated. This method requires the use of less toxic chemicals and a relatively higher number of samples can be analyzed in a short period of time in comparison to established methods of fatty acid analysis. The validated method met the internationally accepted standards, and the BCFA levels in lamb SAT were consistent with published values; consequently, the method can be used for future analyses.

Volatile Profile of Grilled Lamb as Affected by Castration and Age at Slaughter in Two Breeds.

The aim of this study was to assess the effect of castration and slaughter age on the volatile profile of cooked meat from Scottish Blackface (SB) and Texel × Scottish Blackface (T × SB) lambs. M. longissimus thoracis et lumborum was sampled at slaughter and subjected to volatile analysis by SPME-GC-MS. Rams had higher relative proportions, expressed as relative abundance (RA), in lipid oxidation products while castrates had higher RA in pyrazines and benzenoid compounds. There was no consistent age effect on the RA of volatiles, although rams in November and January had a different volatile profile to castrates. There were higher proportions of free branched-chain fatty acids in muscle from SB compared to T × SB lambs. Overall, the results showed that production factors affected the volatile profile of cooked lamb meat which may explain differences in lamb flavor. PRACTICAL APPLICATION: Lamb meat has a characteristic flavor which, according to the evidence to date, may be influenced by farm production factors like gender or slaughter age. Our results showed variations in the proportions of some flavor compounds in cooked lamb between rams and castrated lambs while an increase in slaughter age did not have a consistent effect on proportions of compounds.

Effect of castration and carcass suspension method on the quality and fatty acid profile of beef from male dairy cattle.

BACKGROUND: The use of bulls rather than steers for beef production offers some considerable advantages; however, the eating quality of bull beef is an issue of marketing concern. This study assessed the physicochemical characteristics of young Holstein-Friesian (HF) bull and steer beef. Steer carcasses were suspended by the Achilles tendon (AS) and by pelvic suspension (PS). RESULTS: HF steer beef had higher redness, yellowness and chroma values, whereas bulls had higher ultimate pH and darker muscle. Warner-Bratzler shear force, cook loss at different ageing times, moisture, and insoluble and total collagen were higher for HF bull beef, whereas intramuscular fat, soluble collagen and collagen solubility were higher for steer beef. HF steer beef had a higher proportion of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA), whereas bull beef had higher proportions of polyunsaturated fatty acids (PUFA), PUFA/SFA and n-6/n-3 PUFA ratios. In comparison to AS, PS increased redness and chroma after 24 h blooming; PS improved tenderness up to 7 days of ageing and accelerated the ageing process. CONCLUSION: For young dairy cattle, steer beef would likely have superior eating quality but a relatively less favourable nutritional fatty acid profile to bull beef. Suspension method affected the tenderness and colour intensity of dairy steer beef at different ageing times. © 2018 Society of Chemical Industry.

Nanoparticle passage through porcine jejunal mucus: Microfluidics and rheology.

A micro-slide chamber was used to screen and rank sixteen functionalized fluorescent silica nanoparticles (SiNP) of different sizes (10, 50, 100 and 200 nm) and surface coatings (aminated, carboxylated, methyl-PEG1000ylated, and methyl-PEG2000ylated) according to their capacity to permeate porcine jejunal mucus. Variables investigated were influence of particle size, surface charge and methyl-PEGylation. The anionic SiNP showed higher transport through mucus whereas the cationic SiNP exhibited higher binding with lower transport. A size-dependence in transport was identified - 10 and 50 nm anionic (uncoated or methyl-PEGylated) SiNP showed higher transport compared to the larger 100 and 200 nm SiNP. The cationic SiNP of all sizes interacted with the mucus, making it more viscous and less capable of swelling. In contrast, the anionic SiNP (uncoated or methyl-PEGylated) caused minimal changes in the viscoelasticity of mucus. The data provide insights into mucus-NP interactions and suggest a rationale for designing oral nanomedicines with improved mucopermeability.

Isotopic turnover of carbon and nitrogen in bovine blood fractions and inner organs.

RATIONALE: Isotope ratio analysis of bovine tissues is a tool for inferring aspects of the dietary history of cattle. The objective of this experiment was to quantify the carbon (C) and nitrogen (N) isotopic turnover in blood (serum and residue) and inner organs (liver, kidney, heart and brain) of beef cattle. METHODS: Growing beef cattle (n = 70 in total) were either switched from a control diet containing barley and urea to an experimental diet containing maize and (15)N-enriched urea, for various intervals prior to slaughter or maintained on the control diet for 168 days pre-slaughter. Samples of blood, liver, kidney, heart and brain were collected at 0, 14, 28, 56, 112 and 168 days and analysed using Isotope Ratio Mass Spectrometry. RESULTS: After 168 days, C- and N-isotopic equilibrium was reached in the blood serum, liver and kidney, approached in the heart and brain, but not reached in the non-serum component of blood. The estimated C and N half-lives were 16.5 and 20.7 days for liver, 19.2 and 25.5 days for kidney, 29.2 and 35.6 days for blood serum, 37.6 and 49.9 days for heart, 53.3 and 52.2 days for brain and 113.3 and 115.0 days for the non-serum blood residue, respectively. Modelling the C and N turnover in the different tissue combinations revealed that a combined analysis of liver and heart as well as brain and kidney can provide the most accurate estimation of the timing of the diet switch. CONCLUSIONS: Based on the difference in turnover rates, bovine soft tissues can provide isotopic information on short- and long-term dietary changes, which in turn may be linked to the geographic or production origin of beef cattle. This study also provides basic biological data on organ C and N turnover in a large herbivorous mammal.

Three-dimensional growth of bovine hoof as recorded by carbon stable isotope ratios.

To investigate the usefulness of bovine hooves as incremental tissues, the objective of this research was to gain a better understanding of hoof growth in three dimensions. In a controlled experiment, cattle were switched from a barley-based diet to a maize-based diet (C isotopic spacing between diets was 13.6 per thousand) and maintained on this experimental diet for 168 days. To compare growth rates along the hoof wall, three slices were sampled post-mortem from one bovine claw. In addition, one claw from each of three different animals was sampled at different depths from the surface to determine any possible time lag ('offset') in the laying down of keratin tissue layers. From each hoof as many as 41 superficial samples were taken over the first 60 mm, starting at the periople, and up to 12 samples were taken sequentially at increasing depths to a depth of 6 mm at five particular points on the surface. The growth rate of the abaxial wall of the bovine claw increased from the anterior to the posterior region of the bovine hoof. Analysis of the deep samples revealed that the deeper layers were younger than the surface layers. This offset was inversely related to the hoof growth rate, i.e. hooves with a high hoof growth rate showed a smaller offset. Observed offsets ranged between 9.2 +/- 1.8 days per mm in depth for a high and 14.0 +/- 2.8 days per mm in depth for a low hoof growth rate and were significantly different (t > or = 3.92, p < 0.0005, n = 19 or 27). The results of this study demonstrate that when sampling hooves or hoof fragments for applications such as diet reconstruction, careful consideration needs to be given to sample location.