Dietary essential oil volatiles are transferred to milk and amniotic fluid in sows

Maternal food cues during pregnancy and lactation have been demonstrated in several mammalian species, including pigs, to impact offspring food preferences later in life (Hepper et al. 2012). However, the evidence that dietary volatile compounds are transferred, and to what extent, into maternal fluids in pigs remains elusive. We hypothesise that the efficiency of transfer of dietary compounds into maternal fluids will be specific to each compound and related to their chemical nature. This study aimed to trace and quantify dietary essential oil (EO) compounds in milk and amniotic fluid in sows.

A total of 38 multiparous Large White sows were selected at 104 days gestation. The experiment was divided in two trials: Trial 1 (T1) aimed to assess the kinetics of the potential transfer of two EO compounds (geraniol and anethole) as a proof-of-concept; and Trial 2 (T2) studied the transfer of eight different EO (oregano, thyme, clove, cinnamon, lemon myrtle, lemon ironbark, peppermint gum and nerolina). In T1, six sows per treatment were fed a normal gestation or lactation diet supplemented with one morning dose consisting of 450 ppm of each EO (EO1.1), or the same total amount of each EO but administered in two meals with 225 ppm of each compound (EO1.2). Control group (C1) received non-supplemented feed. Amniotic fluid samples were collected by squeezing the placental tissue. Milk/colostrum was collected on 1 d and 5 d lactation hourly for 6 h immediately following the morning meal. In T2, eight EO were added in equal amounts to feed to a final dose 1 kg/ton (EO2) and compared to a non-supplemented control group (C2). Sows were induced to farrow in order to be able to collect fresh amniotic fluid samples. Colostrum was collected on d 1 lactation, 1 h after the morning meal. All samples were stored at −20°C and analysed by GC-MS. The statistical analysis included t-test and ANOVA (Minitab 16, Minitab Inc., State College, PA, USA).

Results for the T1 showed a significant increase of geraniol and anethole in colostrum (P = 0.02 and P = 0.036 respectively). However, no significant differences (P > 0.5) could be measured in amniotic fluid. Results for T2 are shown in Table 1. All dietary EO were significantly transferred to amniotic fluid and colostrum, except for lemon myrtle. The results also showed significant differences (P = 0.001) in the rate of transfer of the different EO, thyme being the most efficiently transferred to colostrum and clove the most efficient in amniotic fluid. Overall, there was a higher (P < 0.05) transference to amniotic fluid than colostrum for all the EO except peppermint gum, cinnamon and oregano.

Table 1.  Trial 2 results on transfer of dietary EO to amniotic fluid and colostrum in sows comparing the control (C) and the EO treated (EO) groups

In conclusion, our data proves that all dietary EO tested, except lemon myrtle, were transferred to maternal fluids in sows, but in a different rate and quantity. The results confirmed that dietary volatile compounds might be present in colostrum and amniotic fluid of sows and therefore foetuses and newborn piglets could potentially experience perinatal conditioning, hence improving weaning, welfare and performance.