The effects of pre-slaughter pig management from the farm to the processing plant on pork quality

Improving animal welfare status and meat quality through assessment of stress biomarkers: A critical review

Stress induces various physiological and biochemical alterations in the animal body, which are used to assess the stress status of animals. Blood profiles, serum hormones, enzymes, and physiological conditions such as body temperature, heart, and breathing rate of animals are the most commonly used stress biomarkers in the livestock sector. Previous exposure, genetics, stress adaptation, intensity, duration, and rearing practices result in wide intra- and inter-animal variations in the expression of various stress biomarkers. The use of meat proteomics by adequately analyzing the expression of various muscle proteins such as heat shock proteins (HSPs), acute phase proteins (APPs), texture, and tenderness biomarkers help predict meat quality and stress in animals before slaughter. Thus, there is a need to identify non-invasive, rapid, and accurate stress biomarkers that can objectively assess stress in animals. The present manuscript critically reviews various aspects of stress biomarkers in animals and their application in mitigating preslaughter stress in meat production.

The effect of transportation and pre-slaughter detention on quality of pig meat

            This research aimed to determine the influence of stress of various etiologies in pigs caused by transportation and pre-slaughter conditions on meat quality. For this purpose, pigs were divided into 11 groups within two meat processing enterprises, depending on the duration of transportation (short, long without breaks and long with breaks) and the conditions of keeping animals before slaughter. Also, within the two groups were created two subgroups with pigs of different breeds. A total of 156 pigs were studied. Blood was collected from all pigs to determine cortisol and lactate levels, and a sample of meat from the longest back muscle. The pH of the meat was determined at different stages of its maturation, and the weight loss of the sample was determined. As a result of the research, it was found that the highest quality pork was obtained from pigs that experienced lower levels of stress before slaughter. Keeping pigs for 10 – 14 hours before slaughter without access to water and food resulted in higher stress levels, which were probably expressed in higher blood concentrations of cortisol and lactate. Pigs’ access to food and water during pre-slaughter retention allows for high-quality meat by reducing the influence of stress. Pigs’ access to water before pre-slaughter does not affect the stress level but positively affects the loss of meat weight during maturation. The higher the concentration of lactate in pigs’ blood, the faster the pH of the meat decreases after slaughter, which negatively affects its quality and moisture retention. If there is a long-term transport of pigs, there is no rest stop that can significantly reduce stress levels in pigs. Duration of transportation of pigs does not correlate with stress levels, as the conditions before slaughter content.

Impacts of group stunning on the behavioral and physiological parameters of pigs and sheep in a small abattoir

This study investigated reactions of pigs (N = 148) and sheep (N = 77) to group stunning where animals were present for the slaughter of others. Mock stunning with an isolated animal was used as the control. In both species, there was little evidence to suggest a difference in blood glucose and cortisol with stun order (P ≥ 0.21). In pigs, lactate differed by stun order (P < 0.001). Control pigs had lower lactate than pigs stunned first (P = 0.009) likely due to longer rest time after pre-slaughter handling. Conversely, the control sheep had greater average lactate than other groups. However, due to limited sample size and large variation there was not enough evidence to conclude an effect of stun order on sheep lactate (P = 0.28). Overall, there was limited evidence of an impact of stun order on behavior. The last pigs stunned exhibited a greater likelihood of grunting compared with other stun orders (P ≤ 0.05).

Pilot Study of the Relationship between Deck Level and Journey Duration on Plasma Cortisol, Epinephrine and Norepinephrine Levels in Italian Heavy Pigs

The aim of this pilot study was to evaluate the relationship between journey duration, deck level and activation patterns of the hypothalamic-pituitary-adrenocortical axis (HPA) and sympathetic adrenal medullary system (SAM) in pigs. A total of 90 pigs were examined. The animals came from three different Italian farms associated with the same slaughterhouse located in Bari (Apulia region-Italy). A group of thirty animals was transported from Pordenone (11 h journey); a second group was transported from Terni (6.5 h journey); a third group was transported from Benevento (3 h journey). The animals were transported in the same vehicle, which complied with the structural characteristics indicated in the Council Regulation (EC) No. 1/2005. The truck was composed of a lorry and a trailer, each one divided into three decks. Only the animals transported in the trailer were tested for the study. Before transportation, blood samples were collected on each farm, at 6:00 a.m., from 30 pigs randomly selected out of 135 pigs ready to be transported. Blood samples were also collected during slaughter to evaluate plasma cortisol, epinephrine and norepinephrine, around 6:00 a.m. A journey duration of 11 h was associated with significantly higher plasma concentrations of stress hormones compared with shorter journeys. This increase was proportional to the journey duration, with the pigs travelling for 6.5 h displaying intermediate concentrations between those noticed after 3 h and 11 h journeys. The interaction between deck and journey distance was not significant on epinephrine, norepinephrine or cortisol levels collected at arrival. There was a significant effect of deck level on norepinephrine levels (p < 0.0001), a tendency to influence epinephrine levels (p = 0.073) but no effect on cortisol levels (p = 0.945). Overall, we observed that an 11 h-long journey seemed to impact negatively on pigs' HPA-SAM activity, likely requiring the animals to spend more time in the lairage facilities to recover.

ASSESSMENT OF THE QUALITY OF MODERN COMMERCIAL PORK PRODUCTS

By a morphological study of carcasses of young pig stock of different origin, it has been proved that up-to-date crossbreeding schemes using meat-type breeds as parents increase the percentage of meat in a carcass and optimise the lean-to-fat ratio. Physicochemical analysis of pork obtained from pigs of different breeds has shown that all the parameters investigated are within the current physiological standards. Most parameters have shown no significant difference, though tend to exhibit some peculiarities associated with the effect of a genotype on how this or that physicochemical characteristic manifests itself. The use of the Piétrain breed as the sire line decreases the intramuscular fat content, and hence the calorific value of pork. The back fat of this breed has the highest melting point, which indicates its high storability, but somewhat lower cooking properties than those of similar products obtained from offspring of Large White and Landrace parents. The pH and water-holding capacity of the pork of Piétrain-sired offspring make it quite similar to PSE (Pale, Soft, Exudative) meat: this pork is slightly less tender and paler in colour and exhibits greater weight loss during thermal processing. Also, the result of a comprehensive sensory evaluation of boiled pork and pork broth obtained from Piétrain-sired young stock was the lowest, which is consistent with most of the physicochemical properties of pork from pigs of this genotype. So, it is the 75% purebred Landrace that should be favoured as a terminal sire line in crossbreeding programmes in order to obtain pork and bacon of improved quality in intensive commercial swine production systems. It is recommended to combine Piétrain and Duroc lines to produce terminal sires, ½ (Piétrain + Duroc), that will be further mated with two-breed-cross dams – ½ (Large White + Landrace).

Animal welfare in the U.S. slaughter industry-a focus on fed cattle

Animal welfare within the U.S. slaughter industry continues to prevail as one of the top priorities for livestock producers, businesses, and consumers alike. There are federal regulations that enforce the humane transport, handling, and slaughter of cattle. The journey that cattle must make to the slaughter facility is comprised of many environmental and human factors that can positively or negatively affect animal welfare. Cattle may be exposed to multiple stressors, such as noise, unfamiliar animals and humans, temperature extremes, temporary food/water deprivation, variable transport distances and experiences, and new pen conditions. The animal caretakers involved in these processes attempt to minimize stress and discomfort for the animals, but research is needed to focus on the gaps in knowledge and to support the implementation of strategies known to enhance the human-animal interactions that occur from farm to slaughter. This literature review will provide a summary of fed cattle welfare topics, research, and industry tools that span across the beef animal's journey from the farm/feedlot through the slaughter process. In addition, areas that have had little research focus are identified to highlight the need for future work and development of industry tools. Some of these topics include examining trailer design, the use of trailer slats during weather extremes, the welfare aspects of cattle destined for salvage slaughter, multiple preslaughter factors and interactions, abnormal mobility and nonambulatory cattle, lairage environmental conditions, new stunning methods, and the impact of a well-trained, motivated, and stable workforce on cattle and people welfare. The authors conducted a survey at the 2019 North American Meat Institute Animal Care and Handling Conference, which comprised of stakeholders within the meat packing industry, packing plant employees, and food company employees, educators, and auditors. The survey responses identified training/education and communication as areas of need in animal welfare, whereas the majority of survey responses focused on the aspects of the human-animal interaction as the top challenges for the industry. By continuously identifying, measuring, monitoring, and managing animal welfare challenges within the beef cattle slaughter industry, prioritization and execution of programs and training that improve the welfare of cattle can be achieved as animals move through this final stage of the meat production system.

Review: Analysis of the process and drivers for cellular meat production

Cell-based meat, also called 'clean', lab, synthetic or in vitro meat, has attracted much media interest recently. Consumer demand for cellular meat production derives principally from concerns over environment and animal welfare, while secondary considerations include consumer and public health aspects of animal production, and food security. The present limitations to cellular meat production include the identification of immortal cell lines, availability of cost-effective, bovine-serum-free growth medium for cell proliferation and maturation, scaffold materials for cell growth, scaling up to an industrial level, regulatory and labelling issues and at what stage mixing of myo-, adipo- and even fibrocytes can potentially occur. Consumer perceptions that cell-based meat production will result in improvements to animal welfare and the environment have been challenged, with the outcome needing to wait until the processes used in cell-based meat are close to a commercial reality. Challenges for cell-based meat products include the simulation of nutritional attributes, texture, flavour and mouthfeel of animal-derived meat products. There is some question over whether consumers will accept the technology, but likely there will be acceptance of cell-based meat products, in particular market segments. Currently, the cost of growth media, industry scale-up of specific components of the cell culture process, intellectual property sharing issues and regulatory hurdles mean that it will likely require an extended period for cellular meat to be consistently available in high-end restaurants and even longer to be available for the mass market. The progress in plant-based meat analogues is already well achieved, with products such as the ImpossibleTM Burger and other products already available. These developments may make the development of cellular meat products obsolete. But the challenges remain of mimicking not only the nutritional attributes, flavour, shape and structure of real meat, but also the changes in regulation and labelling.

Interference of stress with the somatotropic axis in pigs - lights on new biomarkers

The acceptance of animal products is increasingly associated with standardized animal welfare, which relates to appropriate animal husbandry from birth to slaughter. In particular, shipment to the slaughterhouse is considered as a critical process exposing the animals to a number of, in part severe, stressors. New biomarkers may be useful for the assessment of animal welfare. The IGF-system has been assessed in a commercial pig transport in conjunction with established markers of stress response. Furthermore, the effect of repeated restraint as an experimental model for repeated acute stress was investigated. During shipment from farm to slaughterhouse, plasma concentrations of IGFBP-3 and IGFBP-2 were significantly reduced (p < 0.01). After shipment, the plasma concentrations of IGFBP-5, glucocorticoids and IL-2 increased but decreased after lairage (p < 0.05) whereas IGF-1 decreased after shipment (p < 0.01). Repeated acute stress increased concentrations of IGFBP-3 and IGF-1 in exsanguination blood (p < 0.05). Differential IGF- signatures can indicate altered endocrine or metabolic control and thus contain complex animal-related information. The somatotropic axis may be of particular interest when established biomarkers such as cortisol, glucose, or lactate cannot be used for the assessment of animal stress or welfare.

Correlations among Stress Parameters, Meat and Carcass Quality Parameters in Pigs

Relationships among different stress parameters (lairage time and blood level of lactate and cortisol), meat quality parameters (initial and ultimate pH value, temperature, drip loss, sensory and instrumental colour, marbling) and carcass quality parameters (degree of rigor mortis and skin damages, hot carcass weight, carcass fat thickness, meatiness) were determined in pigs (n = 100) using Pearson correlations. After longer lairage, blood lactate (p<0.05) and degree of injuries (p<0.001) increased, meat became darker (p<0.001), while drip loss decreased (p<0.05). Higher lactate was associated with lower initial pH value (p<0.01), higher temperature (p<0.001) and skin blemishes score (p<0.05) and more developed rigor mortis (p<0.05), suggesting that lactate could be a predictor of both meat quality and the level of preslaughter stress. Cortisol affected carcass quality, so higher levels of cortisol were associated with increased hot carcass weight, carcass fat thickness on the back and at the sacrum and marbling, but also with decreased meatiness. The most important meat quality parameters (pH and temperature after 60 minutes) deteriorated when blood lactate concentration was above 12 mmol/L.

Meat Quality of Crossbred Porkers without the Gene RYR1 (T) Depending on Slaughter Weight

The first aim of the study was to compare selected meat quality parameters in porkers without the gene RYR1 (T) (ryanodine receptor gene). These were porkers slaughtered at 100 to 115 kg and 116 to 130 kg live weight. The second aim of the study was to determine the occurrence frequency of standard-quality meat (red, firm, nonexudative [RFN]) and the occurence frequency of defective meat (pale, soft, exudative [PSE] and acid, soft, exudative [ASE]). The analysis was conducted on the longissimus lumborum muscle in 114 crossbred porkers. The porkers were a cross of Camborough 22 sows and boars from lines 337PIC (Pig Improvement Company), Norsvin Landrace and Pietrain. All of the animals were provided with identical environmental and nutritional conditions. The average weight of the slaughtered animals in the light and heavy groups was 110 kg and 122 kg, respectively. Both groups had the same average post-slaughter meatiness (56.5%). A statistical analysis of selected meat-quality parameters did not show any significant differences between the weight groups. On the other hand, the classification based on carcass quality showed an occurence frequency of defective meat in heavier crossbred porkers (116 to 130 kg) that was three times higher than in those crossbred animals which weighed 100 to 115 kg when slaughtered. In porkers without the gene RYR1 (T) , the defective meat types PSE and ASE occurred with a frequency of 17.54%.

Welfare measurements of finishing pigs on the day of slaughter: a review

Animal welfare on the day of slaughter is of increasing concern to the authorities and consumers alike, creating a need not only to optimize the welfare of the animals but also to document the level of welfare. The day of slaughter is composed of a variety of stages, initiated when the pigs leave the home pen and including pick-up facilities, transport, lairage, stunning and sticking. At each of these stages, the animals are exposed to different stressors that, both individually and in interaction with one another, can compromise welfare. As part of the initial work aiming to document the welfare of finishing pigs on the day of slaughter, this paper provides an overview of the individual stages including a discussion of potential stressors and potential welfare measurements. These measurements are discussed with regard to their relevance and suitability for documentation of animal welfare on the day of slaughter for development of on-site tools for continuous automatic monitoring of animal welfare.

Use of infrared ocular thermography to assess physiological conditions of pigs prior to slaughter and predict pork quality variation

Infrared thermography (IRT) body temperature readings were taken in the ocular region of 258 pigs immediately before slaughter. Levels of lactate were measured in blood taken in the restrainer. Meat quality was assessed in the longissimus dorsi (LD), semimembranosus (SM), and adductor muscles. Ocular IRT (IROT) temperature was correlated with blood lactate levels (r=0.20; P=0.001), with pH taken 1hour postmortem (pH1: r=-0.18; P=0.03) and drip loss (r=0.20; P=0.02) in the LD muscle, and with pH1 in the SM muscle (r=-0.20; P=0.02). Potentially, IROT may be a useful tool to assess the physiological conditions of pigs at slaughter and predict the variation of important meat quality traits. However, the magnitude of the correlations is rather low, so a further development of image capture technique and further studies under more variable preslaughter conditions ensuring a larger pork quality variation are needed.

Range of blood lactate values in farm pigs prior to experimental surgery

In biomedical research the pig is widely used as an animal model for experimental surgery. Feasible monitoring tools during anaesthesia are pivotal for successful and reliable research outcome. Blood lactate values are a monitoring tool and prognostic indicator during surgery both in humans and animals. Lactate levels in pigs might be influenced by various parameters including stressful handling, breed and weight differences. To determine blood lactate levels present prior to experimental surgery, values of 124 female farm pigs were measured in venous blood samples. Pigs presented with blood lactate concentrations ranging from 0.5 to 5.5 mmol/L (median, 1.2 mmol/L; interquartile range [IQR] 1.2). Considering genetic background, Rheinhybrid/Pietrain pigs (n = 51; median, 1.4 mmol/L; IQR, 1) had significantly higher blood lactate levels compared with Landrace/Pietrain crossbred animals (n = 73; median, 1.1 mmol/L; IQR, 1; P < 0.05). Body weight had no significant effect on blood lactate levels within the evaluated range. This report can benefit research projects monitoring blood lactate values in farm pigs during experimental surgery.

Welfare and carcass and meat quality of pigs being transported for two hours using two vehicle types during two seasons of the year

Correa, J. A., Gonyou, H. W., Torrey, S., Widowski, T., Bergeron, R., Crowe, T. G., Laforest, J. P. and Faucitano, L. 2013. Welfare and carcass and meat quality of pigs being transported for two hours using two vehicle types during two seasons of the year. Can. J. Anim. Sci. 93: 43–55. A total of 3756 pigs were transported for 2 h in summer and winter using a “pot-belly” trailer (PB) and a hydraulic double-decked truck (DD) in order to assess the effect of vehicle design on animal welfare and carcass and meat quality. Animal welfare was assessed in randomly selected barrows by measuring heart rate of pigs and lactate and creatine phospho-kinase (CPK) concentrations in exsanguination blood. Skin damage was scored and meat quality was evaluated in the longissimus dorsi (LD), semimembranosus (SM) and adductor (AD) muscles. Heart rates in winter were higher (P< 0.01) during transport, at unloading and in lairage. Blood CPK and lactate concentrations at slaughter were higher (P<0.05 and P<0.01, respectively) in pigs transported on the PB trailer. Bruises increased in winter (P<0.001) and in pigs from the DD truck (P<0.05). The pHu was higher (P< 0.01) in all muscles and L* value was lower (P<0.05) in the LD muscle from pigs transported in the PB trailer. Overall, the results of this study indicate that the type of vehicle, animal location in the truck and the season affect the welfare of pigs during transport with clear consequences on skin bruises and pork quality variation.

Distinctive genes determine different intramuscular fat and muscle fiber ratios of the longissimus dorsi muscles in Jinhua and landrace pigs

Meat quality is determined by properties such as carcass color, tenderness and drip loss. These properties are closely associated with meat composition, which includes the types of muscle fiber and content of intramuscular fat (IMF). Muscle fibers are the main contributors to meat mass, while IMF not only contributes to the sensory properties but also to the plethora of physical, chemical and technological properties of meat. However, little is known about the molecular mechanisms that determine meat composition in different pig breeds. In this report we show that Jinhua pigs, a Chinese breed, contains much higher levels of IMF than do Landrace pigs, a Danish breed. We analyzed global gene expression profiles in the longissimus dorsi muscles in Jinhua and Landrace breeds at the ages of 30, 90 and 150 days. Cross-comparison analysis revealed that genes that regulate fatty acid biosynthesis (e.g., fatty acid synthase and stearoyl-CoA desaturase) are expressed at higher levels in Jinhua pigs whereas those that regulate myogenesis (e.g., myogenic factor 6 and forkhead box O1) are expressed at higher levels in Landrace pigs. Among those genes which are highly expressed in Jinhua pigs at 90 days (d90), we identified a novel gene porcine FLJ36031 (pFLJ), which functions as a positive regulator of fat deposition in cultured intramuscular adipocytes. In summary, our data showed that the up-regulation of fatty acid biosynthesis regulatory genes such as pFLJ and myogenesis inhibitory genes such as myostatin in the longissimus dorsi muscles of Jinhua pigs could explain why this local breed produces meat with high levels of IMF.

Effects of long distance transportation and CO2 stunning on critical blood values in pigs

The aim of the study was to evaluate the effect of two stressful stimuli, long transportation and 80% CO(2) stunning on metabolic-physiological variables, hemodynamic and gas exchange in slaughter pigs imported from the U.S. to Mexico City with a journey time of 27 h, with 8 h of lairage at the abattoir. A total of 589 pigs from three genders were monitored. Overall results show that both stimuli caused metabolic and physiological disturbance. Gilts were more efficient in controlling glycemia after a long transport journey (24h), than castrated males (P<0.05), whose glucose was increased above the 30 mg/dL basal level. Females on arrival had 23mg/dL more lactate compared to basal levels (P<0.05). Stunning caused more physiological effects compared to transportation. Regarding the gender factor, females and entire males were more susceptible to transport stress and stunning compared to the castrated pigs, and entire males showed more complications restoring the gas exchange compared to females and barrows.