Effects of dietary phytase and sex on behavioral responses in castrated male and female piglets

Abstract

This study investigated whether adding phytase to the diet of castrated male and female piglets modulates behavior and if the response differs between sexes. The experiment involved 126 piglets, weaned at 21 days of age, with an average weight of 6.53 ± 1.29 kg. Six treatments were employed, with seven replications and three animals per pen. The treatments were PC: positive control diet - adequate nutritional levels and without phytase; NC: negative control diet - reduced levels of nutrients and metabolizable energy, and without phytase; negative control diets with 500; 1.000; 1.500 and 2.000 FTU/kg of feed. Piglets were subjected to open field (OF), novel object (NO) and reactivity during weighing (RDW) behavioral tests. In the OF, females showed longer exploration time (p = 0.036) and explored a greater number of quadrants (p = 0.031). Conversely, males remained more static (p < 0.01) and vocalized more (p = 0.041). For the NO, females exhibited shorter latency to reach the novel object (p = 0.040). In the RDW, male piglets exhibited greater movement resistance (p = 0.011) and vocalized more frequently (p = 0.038). The addition of phytase did not affect piglet behavior; however, the results suggest that females are more explorative, while castrated males show increased immobility in response to fear.

Keywords: Exploration; Gender; Novel object; Open field; Pigs; Vocalizations; Welfare.