Effects of dietary herbal essential oil mixture and/or mannan-oligosaccharide supplementation on laying performance, some serum biochemical markers and humoral immunity in laying hens exposed to heat

摘要

This study investigates the effects of dietary supplementation with essential oil mixture (EOM) and/or mannan-oligosaccharides (MOS) in laying hens reared under heat stress conditions on body weight gain, laying performance and egg quality as well ason some serum biochemical markers (glucose, cholesterol and triglycerides) and on humoral immunity. A total of 192 laying hens, 52 week old at the beginning of the experiment, exposed to high ambient temperatures during the summer season, were randomly allotted into 4 equal groups according to the diet regimens: 3 groups were supplemented with EOM (included essential oils from Oregano, laurel, sage, myrtle, fennel seeds and citrus peels, 36 mg/kg/day) or with MOS (1 g/kg/day) or with EOM and MOS (with the same dosages) for 16 weeks whereas the last one was not supplemented (negative control). The weight gain tended to be higher (but not significantly) in the 3 supplemented groups. The dietary supplementation with EOM alone or combined with MOS has significantly increased the egg weight and the Haugh unit and the albumen height were markedly enhanced in eggs from all supplemented birds whereas only eggs from hens treated/ with EOM and MOS combination exhibited significantly higher eggshell thickness. The intestinal pH was dramatically depressed in MOS and in EOM + MOS supplemented hens, whereas the intestinal viscosity was significantly reduced only in birds treated with both 2 additives and the small intestine weight was significantly decreased in MOS supplemented ones. On the other hand, no significant alterations in blood biochemistry or in titres of circulating antibodies against the Newcastle disease, infectious bronchitis and infectious bursal disease viruses were evidenced in supplemented hens compared to the controls. These results show that MOS and/or EOM supplementation in laying hens exposed to high temperatures improves some laying performances (egg weight) and egg qualities and partly promotes the digestive function.