The effects of electrical and controlled atmosphere stunning methods on meat and liver quality of geese

Traumatic Injuries Detected during Post-Mortem Slaughterhouse Inspection as Welfare Indicators in Poultry and Rabbits

Simple Summary

An analysis of the slaughterhouse post-mortem examination records over a decade showed that for animals transported to slaughter in containers, the risk of traumatic injury was highest in laying hens (2.80%) and rabbits (1.52%), while the overall incidence of trauma was below 0.5% in other species. The results show that the current rearing conditions and/or pre-slaughter handling of poultry and rabbits have comparatively negative welfare consequences, with significantly more traumatic injuries to the limbs than on the trunk in all species studied. In poultry, traumatic findings on the trunk were orders of magnitude lower to negligible, so the focus should be on preventing injuries to the limbs. In rabbits, the difference was less pronounced with a high number of injuries found on both limbs and trunk.

Abstract

The findings of traumatic injuries during post-mortem inspection in slaughterhouses reflect the level of pre-slaughter handling of animals at the farm and during transport to the slaughterhouse. The prevalence of traumatic injuries was monitored in poultry (1,089,406,687 broiler chickens, 20,030,744 laying hens, 1,181,598 turkeys, 37,690 geese, 28,579,765 ducks) and rabbits (1,876,929) originating from farms in the Czech Republic and slaughtered in slaughterhouses in the Czech Republic between 2010 and 2019. The greatest incidence of traumatic injuries was found in laying hens (2.80%) and rabbits (1.52%); while the overall incidence of trauma was less than 0.5% in other species and categories. The results show that the current rearing conditions and/or pre-slaughter handling of poultry and rabbits particularly affect the limbs; traumatic findings were significantly (p < 0.01) more frequent on the limbs than on the trunk in all species studied. In poultry, traumatic findings on the trunk were orders of magnitude lower to negligible, so the focus should be on preventing injuries to the limbs. In rabbits, the difference was less pronounced, and many injuries were found on both limbs (0.83%) and trunk (0.69%). Our results emphasize the need to reconsider both housing and pre-slaughter handling methods to determine minimum standards for the protection of rabbits, which are still lacking in European legislation.

Carcass Characteristics, Proximate Composition, Fatty Acid Profile, and Oxidative Stability of Pectoralis major and Flexor cruris medialis Muscle of Broiler Chicken Subjected to with or without Level of Electrical Stunning, Slaughter, and Subsequent Bleeding

Simple Summary

The rapid growth in the global and Muslim population has increased the demand for ritually obtained meat, creating a scope of the global meat business. Pre- and post-slaughter practices are of concern in the global meat industries. Therefore, this study examined four types of slaughter, applied with or without a level of electrical stunning, halal neck cutting, and subsequent bleeding (LSHS, MSHS, and HSHS vs. NSHS). Treatments were as follows: (1) NSHS (without electrical stunning, halal neck cut, and subsequent bleeding was for 180 s), (2) LSHS (electrically stunned at 250 mA for 5 s, halal neck cut, and subsequent bleeding was for 180 s), (3) MSHS (electrically stunned at 500 mA for 10 s, halal neck cut, and subsequent bleeding was for 180 s), and (4) HSHS (electrically stunned at 1000 mA for 20 s, halal neck cut, and subsequent bleeding was for 180 s). Slaughtering practices were evaluated in broiler chickens to determine if they influence the carcass characteristics, livability, bleeding out, Pectoralis major and Flexorcruris medialis proximate composition, cholesterol content, fatty acid profile, post-mortem pH, microbial loads, and oxidative stability. With or without stunning, halal neck cutting and subsequent bleeding did not have a significant negative impact on the nutritional aspects, such as proximate composition, cholesterol content, and fatty acid profile, or post-mortem pH, microbial loads except for a variation in some carcass characteristics, livability, bleeding out, and oxidative stability during post-mortem. Since the pre-slaughter conscious state of the animal/bird and post-slaughter bleeding are ritual demands in this process, higher livability and higher bleed out was exhibited in NSHS and LSHS, and there was no large negative impact on nutritional aspects. Therefore, the meat industry can consider without stunning (NSHS) or short-time electrical stunning (LSHS) to capture the global meat market.

Abstract

With an emphasis on the global meat market and considering the ritual requirements and quality aspects, four types of slaughtering treatments were compared: (1) NSHS (without electrical stunning, halal neck cut, and subsequent bleeding for 180 s), (2) LSHS (electrically stunned at 250 mA for five seconds, halal neck cut, and subsequent bleeding for 180 s), (3) MSHS (electrically stunned at 500 mA for 10 s, halal neck cut, and subsequent bleeding for 180 s), and (4) HSHS (electrically stunned at 1000 mA for 20 s, halal neck cut, and subsequent bleeding for 180 s). Four hundred 36 day-old Ross 308 broiler chickens (body weights of 1.4 to 1.8 kg) were divided into four random groups of 100 birds each (ten replicated pens of ten birds). This study examined the livability, bleeding out, Pectoralis major and Flexor cruris medialis proximate composition, cholesterol content, fatty acid profile and post-mortem pH, microbial loads, and oxidative stability. The livability and bleeding out were higher in NSHS and LSHS than MSHS and HSHS (p < 0.05). The Pectoralis major and Flexor cruris medialis proximate composition, cholesterol content and fatty acid profile, post-mortem pH, and microbial loads were unaffected by the slaughter treatments (p > 0.05), but the oxidative stability of Pectoralis major differed during the eight-day post-mortem period (p < 0.05). The results suggest that for capturing the global meat market, the meat industry can consider NSHS and LSHS because the ritual requirements are fulfilled, and there is no negative impact on the nutritional aspects.

Evaluation of the Effects of Pre-Slaughter High-Frequency Electrical Stunning Current Intensities on Lipid Oxidative Stability and Antioxidant Capacity in the Liver of Yangzhou Goose (Anser cygnoides domesticus)

Limited research has been performed to evaluate the effects of high-frequency electrical stunning (ES) methods on the lipid oxidative stability of the meat goose livers. This study was conducted to evaluate the effects of high-frequency-ES current intensities on lipid oxidative stability and antioxidant capacity in the liver of Yangzhou goose (Anser cygnoides domesticus). Forty 92-day-old male Yangzhou geese were randomly divided into five treatments (n = 8). Geese were not stunned (control) or exposed to ES for 10 s with alternating current (AC) at 500 Hz in a water bath. Current intensities were set at 30 V/20 mA (E30V), 60 V/40 mA (E60V), 90 V/70 mA (E90V), or 120 V/100 mA (E120V), respectively. The malondialdehyde level at day 0 was the highest in 120 V (p < 0.05). Antioxidant enzymes' activity on day 2 was the highest in E60V. The 1, 1-diphenyl-2-picrylhydrazyl free radical (DPPH·) elimination ability was lower in the E120V than that in the E60V at two days and four days postmortem (p < 0.05). A combination of 60 V/40 mA/ 500 Hz/ 10 s per bird could be applied in the ES of Yangzhou geese to improve the lipid oxidative stability and antioxidant capacity in the livers.

Duration of transport and holding in lairage at constant postprandial delay to slaughter--effects on fatty liver and breast muscle quality in mule ducks

The present study was designed to evaluate the effect of preslaughter transport (30 vs. 150 min) and holding of mule ducks in lairage in their transport crates (15 vs. 120 min) on the quality of the meat and fatty liver. A total of 120 birds were allocated in a 2 × 2 factorial design with a constant postprandial delay to slaughter (8 h), to avoid the confounding between the effects of the experimental treatments and those of fasting duration. Under such conditions, extending the transport or holding duration did not induce a loss in preslaughter live weight or liver weight. Similarly, breast muscle glycogen stores were not affected by the treatments, nor was the kinetics of postmortem pH decline affected. The mechanical resistance of raw meat obtained by the compression test significantly increased with holding duration. The gross chemical composition of the livers did not differ significantly among the preslaughter treatments. Residual blood in the liver, as indicated by heme pigment concentration, was enhanced with a longer transport, but this effect was more pronounced after the longest holding duration, as shown by a significant interaction. This, however, did not significantly affect the incidence of appearance defects or the commercial grading of the livers. The percentage of fat loss during the cooking of canned livers was significantly reduced when the transport duration was increased. This effect could not be explained on the basis of the current knowledge for determining the technological quality of fatty liver. The identification of biological markers of liver quality is currently underway in our laboratory. Further investigations studying the differential expression of these biological markers according to preslaughter conditions would provide a better understanding of the effect of transport duration on liver processing yield.

The effects of stunning methods on product qualities in force-fed ducks and geese. 1. Carcass downgrading and meat quality

This study investigated the effects of various stunning methods on the quality of carcass and meat in ducks and geese force-fed for the production of French 'foie gras'. The ducks (n = 30 per group) were stunned with one of the following techniques: electrical stunning in a water bath (50 Hz AC, 130 mA, 4 s), head-only electrical stunning (50 Hz AC, 600 mA, 4 s), mechanical stunning (captive bolt) and controlled atmosphere stunning (CAS: phase 1, CO2 (40%)-O2 (30%)-N2 (30%), for 2 min followed by phase 2, CO2 > 85% in air, for 2 min). The same methods (except head-only stunning which was not applied) were used in geese (n = 40 per group). During the first 5 min after slaughter, the stunning techniques that did not kill the animals were associated with a high incidence of head movements (mechanical and electrical head-only stunning), convulsions and convulsive wing flapping (mechanical stunning), in both species. Consequently, the rate of post-mortem pH fall in breast muscle was enhanced and the meat was paler when measured at 24 h or 6 days post mortem (L*, a*, b* coordinates). In ducks, the animals stunned in the water bath showed the lowest bleeding efficiency, compared to the three other procedures. In geese, the mechanical stunning allowed the highest recovery of blood compared to the CAS and the water-bath methods. Meat texture assessed instrumentally and fluid losses during storage and processing were not affected by the stunning method in any species. Sensory analysis showed a higher score for bloody appearance of raw meat in ducks stunned with the methods that kill before neck cutting (water-bath and CAS). This effect was, however, not linked to the rate of bleeding. The sensory properties of cooked meat were not affected by the stunning method. In both ducks and geese, CAS was associated with the lowest rate of fractures of humeral bone but CAS-stunned geese showed the most engorged wing veins. Overall, these results show the positive effect of CAS on the appearance defects of carcass and meat of ducks and geese, and, on the contrary, they confirm the detrimental effects of water-bath stunning on these criteria. However, the incidences on meat sensory qualities were scarce.

Effects of electrical stunning frequency and voltage combinations on the presence of engorged blood vessels in goose liver

The purpose of this study was to investigate the influence of nine electrical stunning methods using various frequency and voltage combinations on the occurrence of engorged blood vessels in goose liver. Two hundred seventy Gourmaud geese (liver-type line SI 14) were slaughtered at 12 wk of age, in groups of 90 at three different times. Thirty birds each were subjected to one of the nine stunning methods. Neck cutting was performed immediately after stunning. The duration of exsanguination was 11 min. After completion of bleeding, the birds were scalded, defeathered manually, and kept refrigerated. At 1 d postmortem, the carcasses were eviscerated and cut up. From the slaughterhouse, the livers chilled in ice were transported to the cannery where they were weighed and graded at 2 d postmortem and were further processed. All of the veins and capillaries full of blood were removed from livers, because their presence was a hazard to product quality by causing discoloration of the canned liver, and the percentage of liver weight loss was then determined. The loss in liver weight due to removal of engorged blood vessels was reduced (P < 0.05) at 350 Hz, 70 to 90 V, and 80 to 85 mA when compared to the results obtained with any other stunning method tested. It was concluded that the use of high-frequency currents for electrical stunning of liver geese might have considerable commercial advantages.