Efeito da acidificação da ração com os ácido fórmico e lignossulfônico sobre a fisiologia digestiva e desempenho zootécnico de juvenis do camarão Litopenaeus vannamei

Abstract

The objective of this study was to evaluate the impacts of feed acidification on the digestive physiology, zootechnical performance, and intestinal health of juvenile Penaeus vannamei shrimp under experimental conditions. Three formulations were tested: control (no acidifier), 5 g/kg, and 15 g/kg of acids applied by spraying. For 84 days, shrimp with an initial weight of 1.99 ± 0.31 g were stocked in 15 circular 0.5 m3 tanks maintained in a covered area, with monitoring of zootechnical and physiological parameters. To determine acid leaching, feed pH was measured at 0 (pre-immersion), 5, 10, 15, 20, 25, and 30 min after water immersion. pH of the proventriculus, hepatopancreas, and posterior intestine contents was also determined at 15 and 30 min after feed offering across treatments. Histological tests were performed on 45 animals (15 per treatment) to assess health status and possible gastrointestinal tract damage. Results revealed that shrimp fed the 5 g/kg acidified diet achieved higher final survival (92.0 ± 4.1%) than those fed 15 g/kg (82,5 ± 6,8%) or the control diet (81.0 ± 4.5%; P = 0.013), while the 15 g/kg acid diet resulted in higher final body weight (13.10 ± 1.59 g) compared to others (11.67 ± 2.35 g and 11.94 ± 1.63 g; P < 0.05). No statistical differences occurred in other zootechnical parameters. Acid leaching assessment by immersion of intact and ground feed showed a successive pH increase in all treatments after water immersion at 0, 5, 10, 15, 20, 25, and 30 min. Diets with 5 g/kg and 15 g/kg exhibited significantly higher variance than control, with acidification effects active after 30 min of water exposure. Treated feeds maintained significantly reduced pH (<6.6) in the digestive tract (proventriculus and hepatopancreas) for up to 30 min, reinforcing method effectiveness. In the histological examination, the satisfactory digestive health of the analyzed animals was evidenced, with findings consistent with the presence of Vibrio spp. and an inflammatory response in all treatments. The samples from the animals exposed to the acidified feed, in turn, in addition to showing a protective effect on the integrity of the hepatopancreas tubules and cellularity, when compared to the control, did not show tissue damage resulting from exposure to organic acids. It is concluded that the inclusion of 5g/kg of the acid solution optimizes survival and mimics the best results when observing the data from the perspective of performance and health, while the inclusion of 15g/kg favors the final growth of the animals, both with proven protective effects on the digestive morphology against infection by Vibrio spp. The technique proved to be viable for practical application in shrimp farming.