Location, distribution, and quantification of myenteric plexus neurons of the jejunum of quails fed with different levels of commercial Macleaya cordata extract

Abstract

Coturniculture has been promising, progressing from a subsistence to a technical activity due to its quick production, low breeding investment, and rapid economic return. After the restriction of antimicrobials as growth promoters, some studies aimed to evaluate alternative products that would make the farming of healthy birds viable without impacting their performance, with commercial Macleaya cordata extract being one of these substitutes. The functions of the gastrointestinal tract are coordinated mainly by the enteric nervous system, and the myenteric plexus is responsible for the reflex control of contractile activities of the external muscles. Thus, this study located and demonstrated the distribution of the myenteric plexus, quantifing the total population of myenteric neurons (Giemsa+) and the subpopulation of myenteric nitrergic neurons (NADPH-d+), and evaluated the effects of commercial Macleaya cordata extract on these populations of quail jejunum neurons. A total of 240 one-day-old female laying quails were distributed into four treatments, with four repetitions of 15 birds each. The test groups (T1, T2, and T3) were treated with commercial Macleaya cordata extract throughout the experimental period using the following doses: T1 - test group, basal diet added with 150 ppm of the extract in the feed; T2- test group, basal diet added with100 ppm of the extract in the feed; T3 - test group, basal diet added with 50 ppm of the extract in the feed; and T4 - control group, basal diet with no added extract. The study included histological analysis, Giemsa+, and NADPH-d+ myenteric neuron staining. The results showed that the myenteric plexus is located between longitudinal layer fibers and in the transition region between the longitudinal and circular layers of the muscular tunic, with the myenteric population organized into ganglia and isolated in the region of neuronal fiber bundles. The commercial Macleaya cordata extract showed no quantitative changes in the myenteric Giemsa+ population and myenteric NADPH-d+ subpopulation, however, the groups that consumed the extract showed greater NADPH-d+ neuron activity compared to the control group, implying that the food remained longer in the intestinal lumen, therefore, enabling greater nutrient use and resulting in increased productive performance.