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.

Impact of stunning before slaughter on expression of skeletal muscles proteome in sheep

The commercial production of halal and kosher meat and controversy surrounding the slaughter without stunning is rapidly growing across the globe. Huge global market for halal and kosher meat warrants conciliation of religious practices and animal welfare for the betterment of meat industry. In the present study, we investigated changes in muscle proteome of sheep (Ovis aries) subjected to either electrical stunning and slaughtering or slaughter without any stunning (halal). The 2DE gel analysis detected approximately 377 protein spots in which 243 (119 up regulated and 124 down regulated) protein spots were significantly (p ≤ 0.05) differentially expressed with a fold change ratio ≥1.5/≤1.5. The in-gel digestion and MALDI-TOF/TOF MS analysis of statistically significant protein spots revealed 35 differentially abundant proteins out of which 26 were up-regulated and 9 were down-regulated. The study demonstrated that slaughtering of sheep without stunning resulted in changes in the abundance of proteins involved in catalytic, structural, and stress related processes. This understanding of protein alterations in sheep slaughtered with and without stunning have the potential to act as possible signature for animal welfare index.

An outlook on livestock welfare conditions in African communities - A review

A significant proportion of the African continent is conducive for animal agricultural production, due to its historical experience and available resources to accommodate and nurture various indigenous and exotic animal species and breeds. With food security being a global challenge, animal products can play an important role as nutrient dense food sources in human diets, particularly in Africa. However, this does not seem to reach its full potential in practice, due to numerous reasons that have not been adequately addressed. Animal welfare reservations can be highlighted as one of the major contributing factors to the curbed progress. The consequences have been scientifically proven to affect product quality and market access. However, in the African community, the concept of animal welfare has not been fully embraced. While there are international animal welfare standards in the developed world, there are inherent factors that hinder adoption of such initiatives in most developing regions, particularly among communal farmers. These include cultural norms and practices, social ranking, socio-economic status, available resources, information dissemination and monitoring tools. Therefore, there is need to harmonize what is internationally required and what is feasible to accommodate global variability. The protocols followed to ensure and evaluate farm animal welfare require regular investigation, innovation and a sustainable approach to enhance animal productivity, efficiency and product quality. Additionally, investing in animal wellbeing and health, as well as empowering communities with significant knowledge, has a potential to improve African livelihoods and contribute to food security. This review seeks to highlight the concept of animal welfare in relation to livestock and food production in African conditions.

Assessing cattle welfare at slaughter - Why is it important and what challenges are faced?

The welfare of animals in the meat industry, especially at the time of slaughter, has become an area of increasing public scrutiny and has prompted research on its assessment, and enhancement. Fundamental factors such as the effects of transport, reactions of the animals to novel environments and underlying commercial pressures which impose 'speed' and 'robustness of action' in the way animals are handled, can pose a challenge when establishing a valid, reliable and feasible welfare assessment protocol for use at slaughter. The purpose of this review is to assess published work on animal welfare at slaughter, with a focus on the current methods used to assess cattle welfare in the slaughterhouse, which are outlined in the scientific and trade literature, and how these relate to the interaction between the environment, the animal, and slaughterhouse personnel.

Gas stunning with CO2 affected meat color, lipid peroxidation, oxidative stress, and gene expression of mitogen-activated protein kinases, glutathione S-transferases, and Cu/Zn-superoxide dismutase in the skeletal muscles of broilers

BACKGROUND

Meat color and lipid peroxidation are important traits related to meat quality. CO2 concentration is a critical factor that can affect meat quality in the commercial use of gas stunning (GS). However, the effect and mechanism of CO2 stunning on meat color and lipid peroxidation during long-term storage remain poorly studied. We aimed to study the effects of GS methods, especially CO2 concentration, on meat color and meat lipid peroxidation in broilers during long-term storage at 4 °C and to explore the potential mechanism of meat color change via lipid peroxidation and the inner lipid peroxide scavenging system.

METHODS

Eighteen broilers were sacrificed after exposure to one of the following gas mixtures for 90 s: 40% CO2 + 21% O2 + 39% N2 (G40%), 79% CO2 + 21% O2 (G79%), or no stunning (0% CO2, control). Meat color, serum variables, enzyme activities, and the gene expression of mitogen-activated protein kinase (MAPK), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferase (GST) and superoxide dismutase (SOD) were determined.

RESULTS

The concentrations of serum triiodothyronine (T3, P = 0.03) and the ratio of serum free triiodothyronine/free thyroxine (FT3/FT4, P <  0.01) were decreased, whereas levels of serum cortisol (P <  0.01) were increased in the 40% CO2 group compared with the control group. Additionally, the thiobarbituric acid-reactive substances (TBARS) 3 d (P <  0.01) and TBARS 6 d (P = 0.01) in breast meat and the TBARS 3 d in thigh meat (P <  0.01) were increased in the 40% CO2 group compared with the control group. Serum T3 was negatively correlated with TBARS6 d both in the breast and thigh meat (r = - 0.63, P <  0.01 and r = - 0.47, P = 0.05 respectively). T3/T4 was negatively correlated with TBARS6 d in the breast meat and in the thigh meat (r = - 0.57, P = 0.01; and r = - 0.53, P = 0.03 respectively). Compared with the control group, Lightness (L*) 1 d (P = 0.03) and L*9 d (P < 0.01) were increased, whereas total chromatic aberration (E*) 1 d (P = 0.05) and E*3 d (P < 0.01) were decreased in the breast meat of both the G40% and G79% groups. The values of yellowness (b*) 3 d (P = 0.01), b*6 d (P < 0.01) and E*6 d (P < 0.01) in the thigh meat were lower in both the G40% and G79% groups than in the control group. In the breast muscle, the mRNA levels of c-Jun N-terminal kinase 2 (JNK2, P = 0.03), GSTT1 (P = 0.04), and SOD1 (P = 0.05) were decreased, and the mRNA levels of JNK1 (P = 0.07), Nrf2 (P = 0.09), and GSTA3 (P = 0.06) were slightly lower in both the G40% and G79% groups compared with the control group. However, among these genes, only the mRNA level of JNK1 was decreased in the G40% group compared with the control group and the G79% group (P = 0.03) in the thigh muscle.

CONCLUSIONS

Compared with the control group, meat color quality in the breast meat was decreased, and the expression of genes in the MAPK/Nrf2/ARE (antioxidant responsive element) antioxidant pathway in breast muscle was partly suppressed by GS of both 40% and 79% CO2. However, oxidative stress and meat lipid peroxidation during storage were aggravated by GS with 40% CO2 compared to GS with 79% CO2 and no GS.

Pre-slaughter cattle welfare indicators for use in commercial abattoirs with voluntary monitoring systems: A systematic review

Animal welfare has become an important subject of public, economic and political concern, leading to the need to validate indicators that are feasible to use at abattoirs. A systematic review was carried out, which identified 72 cattle welfare indicators (CWI) that were classified into four categories (physiological, morphometric, behavioral and meat quality). Their validity and feasibility for use in abattoirs were evaluated as potential measures of cattle welfare during transportation to the abattoir and at the abattoir itself. Several highly valid indicators were identified that are useful to assess welfare at abattoirs, including body condition score, human-animal interactions, vocalizations, falling, carcass bruising, and meat pH. In addition, some intermediate valid indicators are useful and should be investigated further. Information along the food chain could be used systematically to provide a basis for a more-risk-based meat inspection. An integrated system based on the use of key indicators defined for each inspection step with the setting of alarm thresholds could be implemented.

Low-current & high-frequency electrical stunning increased oxidative stress, lipid peroxidation, and gene transcription of the mitogen-activated protein kinase/nuclear factor-erythroid 2-related factor 2/antioxidant responsive element (MAPK/Nrf2/ARE) signaling pathway in breast muscle of broilers

Mechanism of electrical stunning (ES) methods on lipid peroxidation and antioxidant protection were studied by determining meat color, serum variables, antioxidant-related enzyme activities, gene expressions of mitogen-activated protein kinases (MAPKs), nuclear factor-erythroid 2-related factor 2 (Nrf2), glutathione S-transferases (GSTs), and superoxide dismutases (SODs). Broilers were sacrificed without stunning, or after ES with 65V, 86mA, 1000Hz (E65V) or 150V, 130mA, 60Hz (E150V). Serum cortisol and uric acid, muscular malondialdehyde and mRNA levels of MAPKs, Nrf2, GSTA3, GSTT1 and SOD2 were increased, whereas, serum free triiodothyronine, free thyroxine, muscular GST_1d activity were decreased in E65V compared with E150V. Overall, the serum uric acid and transcription of the MAPK/Nrf2/ARE (antioxidant responsive element) signaling pathway were elevated, but didn't overcome the oxidative stress stimulated by low-current & high-frequency ES, leading to aggravated lipid peroxidation at 1d and 9d postmortem in breast muscle compared with high-current & low-frequency ES.

Farm to abattoir conditions, animal factors and their subsequent effects on cattle behavioural responses and beef quality - A review

The current review seeks to highlight the concerns that have been raised on pre-slaughter stress, contributing factors and its consequent effects on cattle behavioural responses and the quality of beef; inter-linking the activities involved from birth to slaughter. Such information is crucial in light of the consumer concerns on overall animal welfare, quality of meat and food security. Slaughter animals are exposed to different conditions during production and transportation to abattoirs on a daily basis. However; the majority of studies that have been done previously singled out different environments in the meat production chain, while conclusions have been made that the welfare of slaughter animals and the quality of meat harvested from them is dependent on the whole chain. Behaviour is a critical component used to evaluate the animals' wellbeing and it has been reported to have an effect on product quality. Apart from the influence of on-farm, transportation and abattoir conditions, the genetic background of the animal also affects how it perceives and responds to certain encounters. Stress activates the animals' hypothalamic-pituitary-adrenal activity, triggering release of various stress hormones such as catecholamines and cortisol, thus glycogen depletion prior slaughter, elevated ultimate pH and poor muscle-meat conversion. Pre-slaughter stress sometimes results to cattle attaining bruises, resulting to the affected parts of the carcass being trimmed and condemned for human consumption, downgrading of the carcass and thus profit losses.

Effects of transport distance, lairage time and stunning efficiency on cortisol, glucose, HSPA1A and how they relate with meat quality in cattle

This study determined the effects of distance travelled, lairage duration and number of stunning shots on the plasma levels of bovine heat shock protein 70 (HSPA1A), cortisol (CORT) and glucose (GLU) and their relationship with beef quality. There were positive correlations among HSPA1A, GLU, CORT, a*, b* and the HUE angle. Animals that were stunned more than once had the highest HSPA1A (13.61±2.874ng/ml) and CORT (109.36±8.373nmol/L) levels. Animals that travelled for 200<400km had lower HSPA1A expression (8.29±2.026ng/ml) than those that were transported for 400<800km (12.11±2.548ng/ml) and <200km (17.32±2.362ng/ml). Lairage duration affected (P<0.05) the expression of HSPA1A, GLU and CORT levels. Animals stunned more than once had elevated CORT and HSPA1A levels. HSPA1A, CORT and GLU were related to beef quality. Stunning of animals more than once increased the levels of blood CORT and HSPA1A.