Gas stunning with CO_2 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. CO_2 concentration is a critical factor that can affect meat quality in the commercial use of gas stunning(GS). However, the effect and mechanism of CO_2 stunning on meat color and lipid peroxidation during long-term storage remain poorly studied. We aimed to study the effects of GS methods, especial y CO_2 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% CO_2+21% O_2+ 39% N2(G40%), 79% CO_2+ 21% O_2(G79%), or no stunning(0% CO_2, control). Meat color, serum variables,enzyme activities, and the gene expression of mitogen-activated protein kinase(MAPK), nuclear factor-erythroid2-related factor 2(Nrf2), glutathione S-transferase(GST) and superoxide dismutase(SOD) were determined.(Continued on next page)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%CO_2 group compared with the control group. Additionally, the thiobarbituric acid-reactive substances(TBARS)3 d(P < 0.01) and TBARS6 d(P = 0.01) in breast meat and the TBARS3 din thigh meat(P < 0.01) were increased in the40% CO_2 group compared with the control group. Serum T3 was negatively correlated with TBARS6 dboth 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 din 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 yel owness(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 m RNA 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 m RNA 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 m RNA 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% CO_2. However, oxidative stress and meat lipid peroxidation during storage were aggravated by GS with 40% CO_2 compared to GS with 79% CO_2 and no GS.

Nutritional modulation of health, egg quality and environmental pollution of the layers

World egg production and consumption have been increasing for the past decades. Traditional strategies in poultry nutrition have made vital contributions to this great growth in quantity. However, current global issues should be considered in modern egg production such as growing populations and food security, food safety and quality, limited resources and environmental problems. The development of knowledge of poultry nutrition and modern biotechnology provides novel nutritional approaches to closely fit the requirement of pullets and laying hens, which will consequently decrease the nutrition excretion and maintain the lower cost of feed. Nutrition has also been widely accepted as a strategy to influence health and diseases of laying hens. The maintenance of good health is an important prerequisite for improving productivity and egg quality. In addition, there are many measures and strategies for minimizing the incidence of egg defects and providing a choice of lifestyle to enhance human health. This paper reviews current research progress on developing innovative technologies and strategies to maximize animal health and performance, improve the quality of egg products and minimize pollution caused by poultry production.

Effect of dietary protein sources and storage temperatures on egg internal quality of stored shell eggs

This study was conducted to evaluate the effects of various protein sources(soybean meal, SBM; cottonseed protein, CSP; double-zero rapeseed meal, DRM) on the internal quality(Haugh unit, yolk index,albumen pH,yolk hardness and yolk springiness) of eggs when stored at either 4 or 28℃ for 28 d. A total of 288 laying hens(32 wk of age) were randomly allotted to 6 treatment groups(4 replicates per treatment) and fed diets containing SBM, CSP, or DRM individually or in combination with equal crude protein content(SBM-CSP, SBM-DRM, and CSP-DRM) as the protein ingredient(s). A 6 x 2 factorial arrangement was employed with dietary types and storage temperatures(4 and 28℃) as the main effects. After 12 wk of diet feeding, a total of 216 eggs was collected for egg internal quality determination.The results showed as follows: 1) lower egg quality was observed in the DRM group compared with the other groups when stored at 4 and 28℃ for 28 d(P < 0.05), while there was no difference in egg internal quality among the other groups. 2) The CSP diet resulted in higher yolk hardness compared with the other diets when eggs were stored at 4℃ for 28 d(P < 0.05). Lower Haugh unit was observed in the DRM and SBM-DRM groups compared with the other groups when eggs were stored for 28 d at 4℃(P < 0.05).3) Yolk breakage occurred in the DRM group and eggs could not be analyzed for egg internal quality when stored at 28℃ for 28 d. The overall results indicated that CSP or DRM as the sole dietary protein source for laying hens may adversely affect the internal quality of stored eggs as compared with the SBM diet, and half replacement of CSP combined with SBM may maintain similar egg quality to SBM diet alone for eggs stored under refrigerated conditions.