Effects of High Concentration Nitrogen Gas Stunning of Pigs on the Quality Traits of Meat and Small Intestine

Simple Summary To satisfy consumer demand, it is necessary to ensure the quality of the meat and small intestine of animals. For consideration of animal welfare and to obtain an adequate quality of the meat and small intestine, animals need to be stunned to minimize anxiety, pain, distress, or suffering. Electric stunning and exposure to a high concentration of carbon dioxide (CO2) are common stunning methods in the meat industry. However, both methods have some limitations. Pale color and a higher tendency of ecchymosis is the common feature in electric-stunned pigs' meat. Exposure to higher concentration of carbon dioxide induces high aversion, irritation of nasal mucosal membranes, and severe respiratory distress causing hyperventilation and breathlessness in pigs. Hypercapnia, hyperglycemia, lactic acidosis, and an increased hematocrit also occur in pigs. To reducing the negative impacts of CO2, inert gases (i.e., Argon and N-2) are sometimes mixed with CO2. But, the amount of Argon in the atmosphere is very negligible (0.93%) and Argon has a high cost in the market. To maintain hypercapnic-hypoxia and improve stability, a higher concentration of N-2 has sometimes been mixed with CO2 and used in pig stunning. But, no trial has used only high concentration of nitrogen in the stunning of animals, while maintaining a hypoxic condition (less than 2% O-2 in atmosphere). Our study involved conducting a trial on electricity, CO2 (80%), and high concentrations of nitrogen (98%) in the stunning of pigs and comparing the meat and small intestine quality traits. Findings show that the meat and small intestine quality of N-2 (98%)-stunned pigs was favorable compared to the other treatment groups. The objective of present study was to investigate the feasibility of utilizing only high concentration of nitrogen gas in the stunning of pigs and its effects on the quality traits of the meat and small intestine.To conduct this experiment, three treatment groups were compared: (i) electric stunning (T1), (ii) CO2 (80%) gas stunning (T2), and (iii) N-2 (98%) gas stunning (T3). A total of 21 standard pigs (Landrace x Yorkshire x Duroc; LYD) were collected from a commercial pig farm, randomly selecting seven pigs for each group (body weight of 104.5 to 120.6 kg). For stunning, each individual pig was separately kept in a gas chamber, after which each specific gas was used to fulfill the desired level in the pit. To obtain the desired level of concentration for each gas (N-2 at 98% and CO2 at 80%), approximately 80 min and 35 min were required, respectively. It was observed that after reaching the desired level of concentration, pigs were stunned within a very short time (for CO2, 90 s and for N-2, 120 s). For electric stunning, standard quality electric devices were used. After slaughtering, the meat and small intestine of each animal was collected separately and kept in a cool room where temperature was -2 degrees C. In the meat and small intestine, L* (Lightness) and b* (Yellowness) were high (p < 0.05) in the T1 and T3 groups. The T2 group showed high a* (Redness) (p < 0.05) values in both the meat and small intestine. A proximate composition of meat showed no significant differences except moisture. The water holding capacity (WHC), cooking loss (CL), and Warner-Bratzler shear force (WBSF) of meat were lowest in the T2 group, but not at a notable difference compared to T3. In the small intestine, L* (Lightness), a* (Redness), b* (Yellowness), and thickness significantly differed (p < 0.05) in each group, but WBSF showed no significance between the T2 and T3 groups. It is concluded that a high concentration of N-2 gas (98%) may be considered in the stunning of pigs, and its effect on meat and small intestine is favorable.

Automated summary

In order to ensure the quality of meat and small intestine, animals need to be stunned during the slaughter process. Traditional methods like electric stunning and exposure to carbon dioxide have limitations. This study investigates the feasibility of using high concentrations of nitrogen gas for stunning pigs and finds that it has a positive effect on the quality of meat and small intestine.