Abstract
Considering that glycyrrhizic acid (GRA) has been shown to have in-vitro and in-vivo antiviral activity against a wide range of viruses as well as immunostimulating activity, a trial to evaluate its effects on the performance and the immune response against Newcastle disease of broiler chickens was carried out. The study was performed with one-day-old Ross x Ross broiler chickens. GRA was added to the drinking water throughout the 49-d production cycle at a dose of 0.03%. Sample size of the trial was established in a pilot assay. Results showed that broiler chickens treated with GRA presented better weight gain, final body weight, feed conversion ratio, and lower mortality rate than the non-treated controls. In addition, GRA-treated birds presented higher antibody titers against Newcastle disease virus and more efficient cellular immune response, as demonstrated by the late-hypersensitivity response test. Blood lymphocyte and thrombocyte counts also increased in this group. The histopathological examination of the bursa, spleen, and thymus revealed that only the thymus of the GRA-treated group had a clearly defined increase in cortex thickness on day 49. The bursa showed a higher number of lymphoid lesions in CG on days 21 and 49 compared with the GRA group. These results suggest that GRA has growth promotion properties, which are possibly linked to immune-based effects.
Highlights
Low cost, high quality, and the efficient production of large quantities of broiler meat are key goals of modern poultry production
The study was performed on a commercial farm located in the state of Queretaro, Mexico, with three flocks of one-day-old Ross x Ross broiler chickens, which were randomly assigned to an untreated control group (CG) and the experimental glycyrrhizic acid (GRA)-treated group (VG)
The second phase of this study was performed on a commercial farm located in the state of Queretaro, Mexico, with a total of 60,000 one-day-old Ross x Ross broiler chicks, which were randomly assigned to two groups: the untreated control group (CG) and the experimental GRA-treated group (GRA-G), with 30,000 broilers per group and three replicates of 10,000 each, allocated so as to have both groups in each chicken house, separated only by a wire mesh
Summary
High quality, and the efficient production of large quantities of broiler meat are key goals of modern poultry production. Encouraging results have been obtained in poultry production with the DNA-containing preparation CpG-ODN®, and with a patented version of Aloe vera aqueous extract (Gomis, et al, 2003; Durrani, et al 2008) Another potentially useful immune-stimulating pharmaceutical preparation based on glycyrrhizic acid (GRA) has been used in human medicine. Ocampo et al (2014) found that addition of GRA to shrimp diets increased the survival rate of shrimp affected in white spot syndrome virus Based on these evidences, the aim of this trial was to evaluate if the GRA oral supplementation in the drinking water could improve the performance of broilers, while stimulating their humoral and cellular immune responses. A basic screening of parameters for liver integrity were performed to assess whether or not a measurable change could be detected in GRA-medicated broiler chickens
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