Salmonella status of pigs at slaughter--bacteriological and serological analysis

Apart from Salmonella monitoring of pig herds during the period of growth to evaluate the efficacy of control programmes, monitoring at harvest level is of relevance to assess the Salmonella status of fattening pigs and the associated risk of introducing Salmonella organisms in the slaughter process. Samples from 1830 fattening pigs were gathered at slaughter. Ileocaecal lymph nodes, rectal and caecal content as well as tonsils were collected for bacteriological examinations, and a part of the diaphragm pillar muscle was taken to gain meat-juice for serological analysis. Salmonella spp. was recovered from 13.8% of all pigs examined. Salmonella Typhimurium and Derby were the dominating serovars. The highest detection rates were found in caecal content followed by ileocaecal lymph nodes. By analysing both organs nearly 90% of all Salmonella positive pigs could be identified. Serological examination revealed 9.6% of the pigs as positive using a cut-off value of OD % ≥ 40. Only one quarter of all Salmonella positive pigs showed also a positive serological result. A reduction of the cut-off value does not necessarily result in a higher compliance between bacteriologically and serologically positive slaughter pigs. Detection of antibodies is useful to verify whether pig herds were previously exposed to Salmonella organisms. However, the Salmonella status of pigs at time of slaughter and the associated risk of dissemination of Salmonella organisms can only be assessed by bacteriological examinations which should include both lymph nodes and caecal content.     

Behavioural and physiological reactions of cattle in a commercial abattoir: relationships with organisational aspects of the abattoir and animal characteristics

Behavioural, physiological and metabolic reactions of cattle to handling and slaughter procedures were evaluated in a commercial abattoir, from arrival until slaughter. Different genders or breeds were not subjected to the same procedures due to abattoir equipment or organisational aspects of the abattoir. Reactions to similar slaughter procedures varied according to animal characteristics and could have consequences for subsequent handling procedures. Factors that appeared to cause handling problems and vocalisation were excessive pressure during restraint, and distractions in the corridor such as noise, darkness, seeing people and activity. Post-mortem muscle metabolism depended on slaughter procedures. Following stunning or halal slaughter, some animals showed head rising movements despite the abolition of the corneal reflex, suggesting that head rising is not always indicative of consciousness. Overall, this study presents concrete data on how different types of cattle may react to slaughter procedures with a direct interest for the abattoir itself but also for scientific purposes.     

The use of meta-analytical tools in risk assessment for food safety

This communication deals with the use of meta-analysis as a valuable tool for the synthesis of food safety research, and in quantitative risk assessment modelling. A common methodology for the conduction of meta-analysis (i.e., systematic review and data extraction, parameterisation of effect size, estimation of overall effect size, assessment of heterogeneity, and presentation of results) is explained by reviewing two meta-analyses derived from separate sets of primary studies of Salmonella in pork. Integrating different primary studies, the first meta-analysis elucidated for the first time a relationship between the proportion of Salmonella-carrier slaughter pigs entering the slaughter lines and the resulting proportion of contaminated carcasses at the point of evisceration; finding that the individual studies on their own could not reveal. On the other hand, the second application showed that meta-analysis can be used to estimate the overall effect of a critical process stage (chilling) on the incidence of the pathogen under study. The derivation of a relationship between variables and a probabilistic distribution is illustrations of the valuable quantitative information synthesised by the meta-analytical tools, which can be incorporated in risk assessment modelling. Strengths and weaknesses of meta-analysis within the context of food safety are also discussed.     

The effects of carbon monoxide on Atlantic salmon (Salmo salar L.)

Atlantic salmon were exposed to carbon monoxide (CO) before the fish were percussively killed and gill cut. The fish were compared against a control group treated identically, without CO. Salmon exposed to CO expressed no adverse reactions and were easily stunned by percussion. CO-treated salmon had an earlier onset of rigor mortis and a faster decrease in muscle pH than the control group. No significant difference in drip loss was found between salmon treated with CO and the control. A significantly deeper red colour of both gills and fillets of CO-treated salmon was observed 10 days post mortem. Significantly higher levels of plasma lactate and potassium were found in CO-treated salmon compared to control, as well as a lower level of pCO₂. Exposure to CO did not increase plasma cortisol, sodium, haematocrit or glucose; however, lactate was high. Exposure of salmon or other fish to CO could improve quality and welfare when slaughtered.     

Fatty acid composition of lambs of indigenous dairy Greek breeds of sheep as affected by post-weaning nutritional management and weight at slaughter

The objective was to assess the effect of breed, sex, post-weaning nutrition and weight at slaughter on the fatty acids (FA) composition in carcass fat of lambs of indigenous Greek dairy breeds of sheep, the Boutsko (B), Serres (S) and Karagouniko (K) breed. The lambs (weaned at approximately 42 days) had been reared under different conditions of housing and feeding in three consecutive experiments (Experiment). In Experiment 1, lambs (n=120) were individually penned and fed ad libitum on a concentrate feed (11.3MJ metabolisable energy (ME)/kg DM and 192g crude protein (CP)/kg DM) together with 100g/day of Lucerne hay (8.3MJ ME/kg DM and 182g CP/kg DM). In Experiment 2, lambs (n=108) were fed the same concentrate on 3 different levels: High (H), Medium (M) and Low (L) and ad libitum on Lucerne hay. In Experiment 3, lambs (n=108) were initially group fed indoors for 63 days on 3 different levels of concentrate (H, M and L) together with ad libitum Lucerne hay. Thereafter they were finished on irrigated, sown pasture. Lambs were slaughtered at one of 5 standard proportions of mature weight (PMW) for each breed in Experiment 1 (i.e. 0.20, 0.30, 0.45, 0.60 and 0.90); at 3 fixed live weights in Experiment 2 (TSLW; i.e. 23, 28 and 33kg) and at 3 fixed PMW in Experiment 3 (PMW; i.e. 0.20, 0.48 and 0.54). The right hand side of their carcasses was minced and a random sample, around 200g, was taken. It was freeze-dried and then grounded to obtain a quantity of 2g for lipid extraction and preparation of fatty acid methyl esters, which were assayed by gas-liquid chromatography to identify. Results were analysed separately for each experiment by analysis of variance. In Experiment 1, breed of lambs had significant effects (P<0.001) on C14:0, C16:0, C17:0, C18:2, C18:3 and C18:1 (P<0.05), whereas sex affected only the percentage of C15:0, C16:1 (P<0.001), C18:0 (P<0.01) and C18:2 (P<0.05). Live weight of lambs at slaughter had significant effects (P<0.05-0.001) on all the fatty acids. In Experiment 2, with the exception of C18:0 and C20:0, all other fatty acids were significantly affected by Breed (P<0.05-0.001). However, only C17:0, C18:0, C18:1 and C18:2 were significantly (P<0.001) affected by the level of concentrates in the diet. The major finding in Experiment 3 was the trend for saturated fatty acids to be lower; possibly due to the fact that lambs finished at pasture. It is concluded that there are possibilities of modifying FA composition in carcass fat of lambs by manipulation of post-weaning nutrition and slaughtering them at a wide range of live weights.     

Effects of mid-summer transport duration on pre- and post-slaughter performance and pork quality in Mexico

Seven hundred and fourteen pigs were monitored from transport to slaughter in July in three treatments: 8, 16 and 24 transport hours; lairage time for the three groups was of 8h. Transport duration significantly (P<0.05) affected live-weight gain during the rest period. Weight gain percentages at lairage were 0.05%, 0.78% and 1.15% for treatments 1, 2 and 3, respectively. Transport to slaughter loss percentage was 2.7%, 4.3% and 6.8% for each of the treatments. Short transport periods significantly increased carcass pH below normal values. Animals transported under acute stress (8h) showed pale carcasses (high possibilities of transforming into PSE meat). On the contrary, pigs transported for 24h had more dark red carcasses. Transport from farm to the slaughterhouse should take no more than 16h in order to improve carcass quality and animals' welfare.     

Depth of concussion in cattle shot by penetrating captive bolt

The prevalence of shallow depth of concussion following captive bolt shooting was assessed in 1608 cattle at an abattoir. Depth of concussion was determined in each animal from physical collapse, presence or absence of corneal reflex, normal rhythmic breathing, eyeball rotation, and whether the animal was re-shot. The presence of nystagmus and the absence of tongue protrusion were also monitored as potential indicators of a shallow depth of concussion, and simultaneous noise measurements assessed whether loudness of gun discharge was linked to concussion depth. The prevalence of a shallow depth of concussion was 8% for all cattle and 15% for young bulls. Nystagmus was associated with other indicators of a shallow depth of concussion. Absence of tongue protrusion was not associated with depth of concussion, but could serve as a useful indicator of jaw relaxation and insensibility following exsanguination. Soft-sounding shots (111 dB) when using 4.5 gr cartridges were associated with shallow depth of concussion.     

A biofuel strategy for Ireland with an emphasis on production of biomethane and minimization of land-take

Increasing energy consumption has exerted great pressure on natural resources; this has led to a move towards sustainable energy resources to improve security of supply and to reduce greenhouse gas emissions. However, the rush to the cure may have been made in haste. Biofuels in particular, have a bad press both in terms of competition with good agricultural land for food, and also in terms of the associated energy balance with the whole life cycle analysis of the biofuel system. The emphasis is now very much on sustainable biofuel production; biofuels from wastes and lignocellulosic material are now seen as good sustainable biofuels that affect significantly better greenhouse gas balances as compared with first generation biofuels. Ireland has a significant resource of organic waste that could be a potential source of energy through anaerobic digestion. Ireland has 8% of the cattle population of the EU with less than 1% of the human population; as a result 91% of agricultural land in Ireland is under grass. Residues such as slurries and slaughter waste together with energy crops such as grass have an excellent potential to produce biogas that may be upgraded to biomethane. This biomethane may be used as a natural gas substitute; bio-compressed natural gas may then be an avenue for a biofuel strategy. It is estimated that a maximum potential of 33% of natural gas may be substituted by 2020 with a practical obtainable level of 7.5% estimated. Together with biodiesel from residues the practical obtainable level of this strategy may effect greater than a 5% substitution by energy of transport. The residues considered in this strategy to produce biofuel (excluding grass) have the potential to save 93,000 ha of agricultural land (23% of Irish arable land) when compared to a rapeseed biodiesel strategy.     

Physico-chemical characteristics of carcass and meat Manchego-breed suckling lambs slaughtered at different weights

Forty-nine Manchego-breed lambs raised exclusively on their dams’ milk until slaughter were used in this study. The effects of gender and slaughter weight (10, 12 and 14 kg) on carcass fatness, meat quality and the fatty acid composition of their fat were studied. Fatness, and in particular dorsal-fat thickness (P0.01), increased with live weight. The effect of gender was even greater (P0.001), as female lambs presented the highest fatness values for all parameters studied. The smallest drop in m. longissimus pH values was seen in the lowest-weight (10 kg) lambs. These same lambs displayed the highest L* value and thus the lightest colour. Fatty acid composition, which was not influenced by live weight, was affected by gender. The subcutaneous fat of female lambs contained more linolenic acid (C18:3) (P0.01) and a greater proportion of polyunsaturated fatty acids than that of male lambs (P0.001). Likewise, the intramuscular fat of female lambs displayed a greater proportion of monounsaturated fatty acids (P0.001) than that of male lambs.     

Relationship between water mobility and distribution and sensory attributes in pork slaughtered at an age between 90 and 180 days

Water mobility and distribution were measured in M. longissimus dorsi from 41 pigs slaughtered at an age of 90, 140, 161 or 182 days using low-field proton NMR relaxometry, and in order to investigate the impact on sensory attributes, a sensory evaluation of the pork was performed in parallel. The sensory evaluation demonstrated a significant effect of slaughter age on juiciness of the meat, and a final juiciness score of 8.4, 7.7, 7.2 and 7.8 was obtained for meat from 90, 140, 161 and 182-day old pigs, respectively. The NMR measurements revealed that the higher juiciness in meat slaughtered at an age of 90 days could be ascribed to a longer relaxation time of the extramyofibrillar water, corresponding to more mobile water, in the fresh meat of 90-day old pigs compared with the older pigs. In the cooked meat the higher juiciness of meat from 90-day old animals could be ascribed to a more homogenous distribution of the myofibrillar water compared with meat from older pigs. In contrast, the NMR measurements showed no effects that could explain the higher juiciness in meat from pigs slaughtered at an age of 182 days compared with meat from pigs slaughtered at an age of 140 or 161 days. Possibly the increase in juiciness when the age at slaughter is increased from 161 to 182 days should be ascribed to an increase in intramuscular fat content, which was not evident in the NMR measurements.