Dietary Linoleic and α-Linolenic Acids Affect Anxiety-Related Responses and Exploratory Activity in Growing Pigs

Background: Growing evidence suggests that the dietary ratio of linoleic acid (LA) to a-linolenic acid (ALA), the precursors of arachidonic acid (AA) and docosahexaenoic acid (DHA), respectively, may affect behavior in mammals. Objective: This study aimed at evaluating the impact of dietary LA and ALA intake on behaviors of growing pigs, a pertinent model for human nutrition. Methods: At 7 wk of age, 32 pigs were allocated to 4 dietary treatments varying in daily intake of LA (1.3 and 2.6 g · kg body weight-0.75 · d-1 for low- and high-LA groups, respectively) and ALA (0.15 and 1.5 g · kg body weight-0.75 · d-1 for low- and high-ALA groups, respectively) for 4 wk. Between days 12 and 18, general behavior in the home pen was observed and pigs were subjected to an open field and novel object test. At 11 wk of age, brain fatty acid composition was analyzed. Results: Compared with high LA intake, low LA intake increased the time spent on exploration, particularly nosing in the home pen (P <0.05) and the open field (P <0.05), and tended to reduce the time spent lying with eyes open in the home pen (P = 0.09). Time spent lying with eyes open also tended to be affected by LA × ALA interaction (P = 0.08). A high-LA/high-ALA intake (ratio of 2; P <0.05) and a low-LA/high-ALA intake (ratio of 1; P = 0.06) decreased the latency to approach the novel object compared with a low-LA/low-ALA intake (ratio of 9). DHA in the frontal cortex was positively correlated with exploratory behaviors in the home pen (rs = 0.56, P <0.01), whereas AA was negatively correlated with time spent lying with eyes closed (rs = –0.48, P <0.01). Conclusions: Low LA intake and a low dietary LA:ALA ratio increased exploration and decreased anxiety-related behaviors in pigs. It is suggested that changes in brain DHA and AA induced by dietary LA and ALA intake mediate these behavioral changes.