Several production factors could exacerbate the biological formation of free radicals which, in turn, cause oxidative stress that impair the health, overall performance and meat quality of broiler chickens. Such factors could have a nutritional, pathological, physiological or environmental origin. The modern drive towards intensive commercial poultry production has elevated the exposure risk of broilers to these factors. In contrast, it has been demonstrated in many studies that dietary antioxidants could combat oxidative stress and improve broiler performance as well as meat quality. Interestingly, these efficacy claims have generated much attention from several feed additive companies which has spurred the development of certain commercial antioxidant products available in the global market. Information from recent studies suggests that both natural and synthetic antioxidants can be effective for augmenting broiler performance and meat quality particularly under conditions of oxidative stress. However, legislative restrictions may hinder the inclusion of high amounts of synthetic antioxidants required to achieve potency in oxidative-stressed broilers. The efficacy of dietary antioxidants depends on the age of the birds, dose and duration of supplementation. Moreover, supplementation of individual antioxidants on average seems to offer a better performance improvement than does a combination of antioxidants. Nonetheless, research efforts aimed at finding the right proportion of combining dietary antioxidants will offer tremendous economic benefits especially with the reduced use of costly synthetic vitamin E. This article gives further insights into research areas that could enhance the effective supplementation of antioxidants in broilers.

Stress in broilers may have severe consequences on the final product quality. A synthetic analogue of uropygial secretion of mother hens was isolated from poultry. This mother hen uropygial secretion analogue (MHUSA) was tested in farm conditions on broilers during 12 wk. The purpose of this trial was to estimate the influence of MHUSA on growing performances, meat characteristics after processing, and stress indicators of broilers. After the 80-d period, birds under treatment were heavier at 3 different weighing ages (P

L’interdiction des antibiotiques comme facteur de croissance en élevage a dynamisé la recherche d’alternatives comme les extraits végétaux et en particulier les huiles essentielles. En aviculture, les huiles essentielles de thym, origan et romarin sont les plus étudiées. Leur composition en principes actifs est très variable, entraînant certainement une grande variabilité des réponses zootechniques. L’huile essentielle de thym semble favoriser le gain de poids, en particulier chez le poulet. Celle d’origan améliore l’indice de consommation et la vitesse de croissance chez le poulet de chair, et le taux de ponte et l’indice de consommation chez la poule pondeuse. Celle du romarin améliore aussi l’indice de consommation chez le poulet. Cependant, utilisées à forte dose, les huiles essentielles peuvent exercer des effets contraires. Toutefois, la consommation d’huiles essentielles aux doses utilisées (moins de 0,5 mg par kg de poids vif) ne dépasse pas le seuil de toxicité pour l’animal ou pour le consommateur.

________________________________________________________________________________ AbstractPerformance, physiological and behavioural parameters of two groups of domestic chickens were compared. Chickens were raised in classical commercial conditions in buildings housing 12000 birds. One group acted as a control, while the environment of the other was perfused with MHUSA (Mother Hens' Uropygial Secretion Analogue), a synthetic analogue of a mother-hen odorant secretion which has shown its potential in reducing stress-related reactions in chickens. At the end of the rearing period the animals treated, appeared less stressed, as determined by a range of behavioural and physiological parameters. Even if there was no treatment effect on live weight, the carcasses of MHUSA treated animals were heavier and showed less scarring from fights. The influence of MHUSA was proven when it was removed from the atmosphere. Sex and age appeared to have an importance with regard to the action of MHUSA on the number of suffocated animals. There were no differences between the two groups in a variant of the tonic immobility test. Thus this semiochemical appears to have a positive effect on broiler welfare.

Two similar 400-m2 buildings, each housing 8,400 broilers of a commonly used industrial strain, were used to test the effectiveness of the semiochemical treatment known as mother hen uropygial secretion analogue (MHUSA). The birds in 1 building were exposed to MHUSA continuously during a 35-d growing period, whereas those in the other building received a placebo. The experiment was then repeated using precisely the same conditions but with the building treatment reversed to control for any building effect. The purpose of the trial was to evaluate the effect of MHUSA on growing performances (live weights) and stress indicators observed from blood samples: heterophil-lymphocyte ratio and corticosterone level. Data analysis (ANOVA) showed that MHUSA-treated broilers had a higher mean growth rate, as shown by increased live weights at both d 17 and 35 (P < or = 0.001 and P < or = 0.001, respectively). After the 35-d growing period, we observed both lower heterophil-lymphocyte ratio (P < or = 0.001) and lower corticosterone level (P < or = 0.05) for birds treated with MHUSA compared with placebo, further indicating that the birds were less stressed. We conclude that constant diffusion of MHUSA in buildings used to house broilers might enhance the welfare and growth of the bird by reducing stress.