BackgroundAccurate screening of new alternative antimicrobial compounds is essential for their use to control pathogens in swine production due to the replacement of antibiotics and zinc oxide. Most in vitro studies have separately reported the antimicrobial activity of organic acids and essential oils (EOs) using diverse methods for susceptibility testing. In addition, in vitro outcomes can help in the selection of the suitable antimicrobial compound and effective combinations of these compounds in the control of pathogens of interest in pork production. Therefore, the aim of this study is to determinate the antibacterial activity of six organic acids and six EOs against Escherichia coli, Salmonella spp. and Clostridium perfringens isolates, some of them multi-resistant to antibiotics, from swine origin. The synergistic effects between the products with higher activity for each bacteria were also calculated.ResultsAll products tested showed activity against at least one bacterial species, except for black pepper EO. The results showed that formic acid with the shortest chain length was the most effective against E. coli and Salmonella spp., while the sodium salt of coconut fatty acid distillates with long chain acids was the most effective against C. perfringens. The susceptibility of isolates tested to EOs was similar, a result that demonstrates a similar activity of these products against phylogenetically unrelated pathogens. In addition, an additive effect was shown for carvacrol-oregano EO for E. coli, formic acid-carvacrol and formic acid-thymol for Salmonella spp. and carvacrol-cinamaldehyde for C. perfringens.ConclusionsThe susceptibility of isolates to EOs was similar, a result that demonstrates a similar activity of these products against phylogenetically unrelated pathogens in contrast to organic acids. In addition, an additive effect was shown for several combinations of these compounds.

Despite the limited use of antibiotics as growth promoters (AGPs) in a number of countries, many others find a useful tool in them. However, many producers in the later regions are transitioning to AGP-free production for commercial reasons. The aim of this trial was to determine whether a blend of essential oils (EO), like oregano or clove, could reach similar production/health parameters compared to an AGP treatment used in broiler production. A total of 1,200 one-day-old chicks were distributed in 2 treatments within 12 floor pens (n = 6). The treatments were: T1-basal feed + AGP (Enramycin 10ppm); T2-basal feed + EO (1kg/t). The trial lasted 35d and performance parameters were recorded weekly. On day 21 and 35, one bird per pen was euthanized for intestinal and carcass analysis. Data were analyzed by one-way ANOVA using the GLM procedure of SAS 9.0. There were no significant differences in the performance parameters at 35d. A trend was observed of higher BW (P = 0.062) at 28d for EO birds (1,708g) compared to AGP birds (1,671g), which relates to another trend (P = 0.071) of increased daily gain from 21-28d (685g and 653g for EO and AGP treatments respectively). A relevant finding was a significantly (P = 0.034) higher mortality in AGP birds from 0-28d (4.83%) compared to EO birds (3.00%). In the post-mortem analysis no differences were observed in intestinal segments in relative and total length. However, animals from T2 showed a trend (P = 0.077) to have heavier gizzards at 21d, which could indicate an effect of EO on their development, while T1 animals had a significantly heavier cecum at 35d (P = 0.026). No relevant findings were observed in carcass weights and yield. These results suggest that this EO blend could be a valid alternative to AGPs, although further trials under commercial conditions should be carried out to confirm its potential.

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The aim of this trial was to evaluate the effect of prenatal and postnatal inclusion of a combination of essential oils (EO) on performance parameters and diarrheas after 2 weeks post-weaning. The trial followed a 2x3 factorial design; 2 sow diets: basal or with EO at 375 g/t x 3 piglet diets: basal diet, medicated with 200 ppm of colistin or treated with 375 g/t of EO. A total of 168 weaned piglets were randomly distributed in the 6 groups: 3 from basal sows (CC, CA and CT) and 3 from EO sows (TC, TA and TT), being the animals from the TT treatment the ones imprinted. The incidence of diarrhea was recorded twice a day and calculated using the percentage of animals with diarrhea over the total period of observations carried out. The animals were weighed at 14 days post-weaning. Average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR) were calculated. Data were analyzed by two-way ANOVA using GLM procedure of SAS. Animals from the TT group had significantly lower incidence of diarrheas from 0 to 14 days post weaning. Diarrhea was recorded on 4.7b% of the observations (TT group), being significantly lower (P ≤ 0.001) than the animals from CC (10.8a%), CA (13.7a%), CT (10.7a%), TC (14.4a%) and TA (12.9a%). Performance parameters indicated that there were non-significant differences in BW, ADFI, ADG with numerically lower FCR (kg/kg) 1.14 in TT group (CC 1.23, CA 1.33, CT 1.27, TC 1.22, TA 1.23). Despite the non-significant differences in performance parameters, in this study the effect of imprinting with essential oils reduced diarrhea incidence.

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