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Perinatal flavour learning through the maternal diet is known to enhance flavour preference and acceptance of flavoured food in many species, yet still little is known about the mechanism underlying perinatal flavour learning. Previously it was found positive effects of perinatal flavour learning on food intake, growth and behaviour of piglets postweaning, but no increased preference for the flavour. This suggests that flavour learning in pigs works through a reduction of weaning stress by the presence of the familiar flavour. The aim of this study was to investigate whether perinatal flavour learning reduces stress at weaning, and whether the effect is stronger when the familiar flavour is present in the food. The experiment was set up in a 2 x 2 factorial design including postweaning pen treatments, with preweaning treatment (Flavour or Control) and postweaning treatment (flavour in Food or flavor in Air) as factors. The experiment was conducted in two successive batches. A total of 24 multiparous sows and their offspring were used. Sows were assigned to the Flavour (n=12) or Control (n= 12) treatment group and received anise flavoured or control food, respectively, between days 98 and 115 of gestation, and from day 2 after giving birth until weaning the piglets on day 25. Sows in the flavor group received a daily dose of 350 mg transanethol, given in two daily portions of 175 mg (dissolved into 20 ml soy oil). Control sows received two daily portions of 20 ml soy oil. Only eight pigs per litter were used, of which four piglets were assigned to the Food treatment (flavour in food), and four to the Air treatment (flavour in air), resulting in 12 Flavour-Air pens, 12 Flavour-Food pens, 12 Control-Air pens and 12 Control-Food pens.
Preweaning and postweaning treatments did not affect food intake, preference or growth in the first two weeks postweaning but flavour treatment reduced the latency to eat (24 vs. 35 hours, P = 0.02) and within-pen variation in growth (SD within-pen: 0.7 vs. 1.2 kg, P < 0.001). Salivary cortisol levels tended to be lower four and seven hours postweaning for Flavour piglets compared to Control piglets (4 hours: 2.5 vs. 3.0 ng/ml, P = 0.05; 7 hours: 3.1 vs. 3.4 ng/ml, P = 0.08). Flavour piglets played more and showed less damaging behaviours than Control piglets, indicating that the familiar flavour reduced stress around weaning. Few interaction effects were found between preweaning and postweaning treatment, and no effects of postweaning treatment.
The conclusion is that in the newly weaned pig, perinatal flavour learning results in a reduction of stress when the familiar flavour is present, regardless of providing the flavour in the food or in the air.
M Oostindjer, JE Bolhuis, K Simon, H van den Brand, B Kemp. Perinatal flavor learning and adaptation to being weaned: all pigs needs is smell. 2011. PLoS ONE, 6(10):e25318. doi:10.1371/journal.pone.0025318.
