Effets du Stress Avant Abattage sur les Qualités Nutritionnelles de la Viande de Poulet de Chair nourri avec des Régimes riches en Acides Gras Insaturés Additionnés d’Antioxydants Naturels

Effects of Stress Before Slaughter on Nutritional Qualities of Chicken Meat Fed with Diets Rich in Unsaturated Fatty Acids Supplemented with Natural Antioxidants In nutrition, increasing the levels of polyunsaturated fatty acids (PUFA) in meat is a primary goal of nutritionists. But, the major concern of this enrichment is the high susceptibility of these (PUFAs) to peroxidation, during the storage of the meat or if it comes from an animal that has undergone stress before its slaughter as that of transport, and therefore the use of natural antioxidants is necessary to limit the lipoperoxidation of meat. The objective of the first study is to evaluate the impact of a diet added with canola seed and supplemented with vitamin C or rosemary leaves on growth performance, fatty acid composition and lipid peroxidation of thigh meat during storage at 4°C. The experiment was carried out during the period of April-June 2014, and involved 220 chicks of the ISA F15 strain, which were divided into two groups and fed two different diets (standard diet (T) and diet added 5% of canola seed (GC)), during the finishing phase the group (GC) was divided into two subgroups whose diet was supplemented either with 200 mg/kg of vitamin C (GCC) or 10 g/kg of rosemary leaves (GCR). We have demonstrated that the incorporation of 5% of canola seed in the diet increases by more than twice the proportion of n-3 PUFAs in thigh meat (p<0.05), but affects negatively (P<0.05) the chickens performance. However, the growth retardation observed at the beginning of the breeding is compensated at the end of the finishing phase (J56) by the supplementation of the second diet with 200mg/kg of vit C and 10g/kg of rosemary leaves. Malondialdehyde (MDA) concentrations increased further (p <0.05) for the (T) group compared to the other two groups (GCC and GCR) during storage at 4°C, and the dose of 10 g/kg rosemary had a higher antioxidant effect than that of 200mg/kg of vit C. The aim of the second experiment was to study the effects of transport stress responses on chicken serum glucose and lactic dehydrogenase (LDH) and creatine kinase (CK) activities, fatty acid composition and different meat quality indicators (pH, color, MDA concentration), and improve the meat oxidative stability by dietary supplementation with vitamin E and olive leaves. The experiment was carried out during the period April-May 2015, on 160 chicks of the ISA F15 strain which consumed a diet added 5% of the canola seed "00" and were divided into four groups in finishing phase: Group 1: was fed with the diet without addition of antioxidant (T), group 2: received diet supplemented with 200 mg/kg of vitamin E (VE), group 3: consumed diet supplemented with 10g/kg of olive leaves, (group 4): in which 200 mg/kg of vit E and 10 g/kg of olive leaves (VE + FO) were added to the diet. On the day of slaughter, each group of animals was divided into two subgroups; one was placed in a rest situation and the other was subjected to transport stress for 2 hours. At the end of this trial, pre-slaughter transport resulted in a significant (p <0.05) decrease in live weights and a significant (p<0.05) increase in serum glucose and LDH and CK activities. In addition, a significant increase in the pHu values of the meat accompanied by a remarkable decrease (p<0.05) in the luminance and in the proportion of PUFAs was also observed in transported animals. In addition, there was a significant (p<0.05) increase in MDA concentrations in the meat of chickens transported, however, the addition of 200 mg/kg of vit E and 10g/kg of olive leaves to chickens diet reduces MDA values by 23% and 18% respectively. Thus, the combined intake of these two antioxidants was more effective in reducing by 30% the lipoperoxidation. Finally, dietary supplementation with natural antioxidants such as rosemary and olive leaves seems an interesting alternative to the use of synthetic products (vit C and E) to increase the oxidative stability of meat.