Effect of lairage time, behaviour and gender on stress and meat quality parameters in pigs

Effect of lairage time prior to slaughter on stress in pigs: a path analysis

BACKGROUND

Pre-slaughter process during transportation, handling, and lairage causes stress in pigs, affecting animal welfare and meat quality. Therefore, lairage factors are important for relieving stress. A total of 24 LYD (Landrace × Yorkshire × Duroc) barrows were used to investigate the effect of 6 and 20 h lairage time (LT) on cortisol, serotonin, and catecholamine in blood and physiological factors in muscle, and to verify the causal relationship between these factors.

RESULTS

The results revealed that cortisol was increased (0.064 ± 0.007 µg/ml), and epinephrine (0.020 ± 0.002 µg/ml) and norepinephrine (1.518 ± 0.071 µg/ml) were lower at a LT of 20 h than those at 6 h, and there was no significant effect on the muscle and carcass characteristic factors. In addition, cortisol and norepinephrine showed a negative correlation (r = -50,346, p = 0.0121), epinephrine and glycogen had a positive correlation (r = 0.4417, p = 0.0307), and serotonin and heat shock protein 70 (HSP70) were positively correlated (r = 0.4715, p = 0.0200). Path analysis indicated that the increase in LT had a direct effect on cortisol, epinephrine, and norepinephrine, and an indirect effect on muscle glycogen.

CONCLUSION

This study confirmed the effect of the increase in LT from 6 to 20 h in the lairage room on the stress response of pigs. These findings support the legal requirements that advocate for shorter lairage times, in alignment with enhanced animal welfare standards.

Mixed management in growing and finishing pigs: Differences between gender and their impacts on behavior, growth performance, and physiological parameters

Mixing, a common management strategy used to regroup pigs, has been reported to impair individual performance and affect pig welfare because of the establishment of a new social hierarchy after regrouping. In this study we aimed to determine whether mixing management (non-mixed vs. mixed) and gender (gilts vs. barrows) affect the social and non-social behavior, performance, and physiological parameters of pigs. A total of 96 growing pigs (48 barrows and 48 females) were separated into two treatments: control (CT)-pigs that were mixed once during the growing-finishing period; and social stress (SS)-pigs that were mixed thrice during the growing-finishing period. We recorded social and non-social behaviors, injury score, performance, and physiological parameters during the experimental period. Data were grouped by the period, based on each mix performed, and overall values. The statistical analysis performed considered gender and treatment. For treatment, during period-II and III, the SS group presented the highest frequency of agonistic interactions (AI), stayed longer lying laterally (LL) and sternly (LS), and explored more enrichment material (ER) than the CT group. Furthermore, SS pigs presented the highest injury score in the ear, head, and middle and posterior regions. Compared to the females, the barrows spent more time at the electronic feed station and initiated most of the agonistic interactions during period-II, and they presented a higher injury score for the ear and head regions during period-III. In conclusion, repeated regrouping significantly affected social and feeding behavior without severely altering performance and physiological parameters. Furthermore, different patterns of social and feeding behavior, agonistic interactions, and injury scores between barrows and females were observed. This study provides an understanding of the impact of mixing management and gender differences on pigs, and this knowledge can be used to improve swine productivity and welfare.

Prevalence of carcass lesions and their effects on welfare, carcass composition and meat quality in slaughtered pigs

The aims of this study were to determine the prevalence of carcass lesions in slaughtered pigs and to quantify their relationships with different animal characteristics, pre-slaughter factors, blood measurements, performance indices, carcass composition and meat quality traits. Data was recorded for 30 journeys referring to 1080 market-weight pigs that originated from 15 commercial small-scale finishing farms. Carcass lesions were visually assessed on the slaughterline in different parts of the carcass, i.e., anterior, middle and posterior, using a three-point scale. Complete blood count was investigated. The following performance indices and carcass composition traits were measured: average lifetime daily weight gain, live, hot and cold carcass weights, cooler shrinkage, dressing percentage, backfat thickness and meatiness. Meat pH and temperature were measured 45 minutes postmortem. Of the 1080 pigs slaughtered in 30 batches, 70.28% displayed some degree of lesions on the carcass (moderate – 30.00%; severe – 40.28%). The carcass lesions were the most prevalent (50.20%) in the posterior part of the pig carcass. RYR1 genotype, live weight, loading density, lairage time, lairage density and slaughter season affected the carcass lesion prevalence. The presence of carcass lesions, irrespective of severity, was associated with alterations in blood measurements in slaughtered pigs, indicating compromised animal welfare. The presence of severe carcass lesions in slaughtered pigs was significantly associated with increased meat pH45min, which led to the highest occurrence of dark, firm and dry pork. In contrast, there was strong evidence of association between the presence of moderate carcass lesions in slaughtered pigs and both decreased meat pH45min and increased meat T45min, which led to the highest occurrence of pale, soft and exudative pork among the carcass lesion groups. In conclusion, this study showed a high prevalence of carcass lesions in slaughtered pigs, whereby the risk of their occurrence was affected by both animal characteristics and pre-slaughter conditions. Also, the presence of carcass lesions in slaughtered pigs, irrespective of severity, was significantly associated with alterations in the blood measurements and pork quality.

Impact of Procedures and Human-Animal Interactions during Transport and Slaughter on Animal Welfare of Pigs: A Systematic Literature Review

Animal welfare is a high social and political priority and is enshrined in European and national legislation. This systematic literature review (funded by the German Ministry of Food and Agriculture; grant no. 2817806A18) was conducted to find animal and management-based indicators that could be influenced by changes in pig handling and management procedures on the day of slaughter and, therefore, will directly result in improved animal welfare. For this systematic literature review, following the PRISMA guidelines, we conducted a structured literature search using the databases PubMed^®, Web of Science^TM, and LIVIVO with set search terms and their combinations in German and English. Only peer-reviewed original articles from European countries from 2009 until 2022 that dealt with welfare during transport and/or slaughter of fattening pigs and offered potential measurable indicators on the basis of the animal or management, and either directly or indirectly recommended handling practices were included. We used the literature management system EndNote^TM, and after duplicate removal, a total of 1099 records were found for further analysis. After analysis and discussion in the review team, which consisted of three experts in total, 105 articles underwent full-text screening. Finally, 39 articles were included in the results for this systematic literature review. According to this systematic literature review, the following procedures have a positive impact on the animal welfare of pigs on the day of slaughter. Calm-rather than rough-handling of pigs was the most influential factor. This can be achieved by using animal-friendly driving aids. Loud noise should be avoided in general or reduced as far as possible. Transport time is not always influenceable, but shorter transport duration with stocking density as stated by the European regulations as a maximum will reduce stress in pigs. Our review showed that there are differing scientific results about lairage duration, although this should be set in relation to prior stress and transport time. Knowledge of good stunning parameters, such as gas concentration, exposure time to the gas, recommended amperage, and current flow duration is essential. If electrical stunning is performed, the correct attachment of electrodes is crucial. The control of stunning effectiveness is extremely important to avoid suffering and pain, with the proviso that it is assessed on the basis of multiple parameters. The corneal reflex, regular gasping, and the up-righting reflex could be assessed together. Certificates of competence and continuing educational programmes for the personnel form the basis of animal-friendly handling and a stressless slaughter routine. It can be assumed that the results of this systematic literature review reflect the state of current research of pig welfare during transport and slaughter in the European Union, even though it must be assumed that not all relevant points were covered by the review, which can be seen as a limitation at the same time because important non-European or older publications could not be included.

Stress responses in camels subjected to different rest periods (0 and 12 h) at slaughterhouse

This study investigated the effect of two different rest periods (R0: no rest time, and R12: 12 h of rest) on several stress indicators, including plasma and serum stress parameters, in dromedary camels (Camelus dromedarius). This study involved 60 healthy male dromedary camels aged 5 years, from which blood samples were collected. Cortisol, glucose, urea, creatinine, the enzymatic activity of creatine kinase, lactic dehydrogenase, aspartate aminotransferase, alanine aminotransferase, and alkalinephosphatase were analyzed. Data obtained indicated that rest time had a significant effect on cortisol, creatinine, creatine kinase, lactic dehydrogenase and aspartate aminotransferase (p < 0.05). However, no statistically significant effect was found for glucose, urea, alanine aminotransferase, and alkalinephosphatase. The values of cortisol and creatinine showed a significant decrease at R12. In contrast, the enzymatic activity of creatine kinase, lactic dehydrogenase, and aspartate aminotransferase, significantly increased at R12. Additionally, several correlations between different studied parameters were documented, including for lactic dehydrogenase. The results obtained in this study suggest that rest time may influence welfare indicating parameters. In summary, a rest time of more than 12 h is recommended in order to allow camels to recover from the effects of pre-slaughter stress. Additionally, lactate dehydrogenase might be suitable to use as an indicator of stress in camels during the slaughter process.

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.

Physiological responses of pigs to preslaughter handling: infrared and thermal imaging applications

Loading, transport, unloading, lairage and stunning are the principle ante-mortem events that generate negative responses associated with stress in pigs. For this reason, it is important to verify the condition of animals throughout the supply chain in order to ensure their welfare and obtain, at the end of the slaughtering process, high-quality carcases and meat. Several studies have identified the indicators and samples that need to be taken into account to properly measure and evaluate the responses that these animals emit to the stressors involved. However, these procedures must be carried out quickly and by non-invasive means so as not to impede the flow of animals through the operations of loading, transport, unloading and lairage. Therefore, the objective of this review article is to analyse the stressful events that pigs experience during these events and discuss the use of the infrared thermography (IRT) as an alternative tool for measuring stress based on temperature changes on the surface of pigs’ skin. We argue that infrared thermography can be used as a strategy to improve animal welfare during loading, transport, unloading and lairage by preventing fatigue and deaths, and decreasing negative impacts on meat quality, such as pale, soft and exudative (PSE), or dark, firm and dry (DFD) conditions.