This review article summarizes the efficacy, feasibility and potential mechanisms of the application of essential oils as antibiotic alternatives in swine production. Although there are numerous studies demonstrating that essential oils have several properties, such as antimicrobial, antioxidative and anti-inflammatory effects, feed palatability enhancement and improvement in gut growth and health, there is still a need of further investigations to elucidate the mechanisms underlying their functions. In the past, the results has been inconsistent in both laboratory and field studies because of the varied product compositions, dosages, purities and growing stages and conditions of animals. The minimal inhibitory concentration (MIC) of essential oils needed for killing enteric pathogens may not ensure the optimal feed intake and the essential oils inclusion cost may be too high in swine production. With the lipophilic and volatile nature of essential oils, there is a challenge in effective delivery of essential oils within pig gut and this challenge can partially be resolved by microencapsulation and nanotechnology. The effects of essential oils on inflammation, oxidative stress, microbiome, gut chemosensing and bacterial quorum sensing (QS) have led to better production performance of animals fed essential oils in a number of studies. It has been demonstrated that essential oils have good potential as antibiotic alternatives in feeds for swine production. The combination of different essential oils and other compounds (synergistic effect) such as organic acids seems to be a promising approach to improve the efficacy and safety of essential oils in applications. High-throughput systems technologies have been developed recently, which will allow us to dissect the mechanisms underlying the functions of essential oils and facilitate the use of essential oils in swine production.
Campylobacter jejuni is an important zoonotic foodborne pathogen causing acute gastroenteritis in humans. Chickens are often colonized at very high numbers by C. jejuni, up to 109 CFU per gram of caecal content, with no detrimental effects on their health. Farm control strategies are being developed to lower the C. jejuni contamination of chicken food products in an effort to reduce human campylobacteriosis incidence. It is believed that intestinal microbiome composition may affect gut colonization by such undesirable bacteria but, although the chicken microbiome is being increasingly characterized, information is lacking on the factors affecting its modulation, especially by foodborne pathogens. This study monitored the effects of C. jejuni chicken caecal colonization on the chicken microbiome in healthy chickens. It also evaluated the capacity of a feed additive to affect caecal bacterial populations and to lower C. jejuni colonization. From day-0, chickens received or not a microencapsulated feed additive and were inoculated or not with C. jejuni at 14 days of age. Fresh caecal content was harvested at 35 days of age. The caecal microbiome was characterized by real time quantitative PCR and Ion Torrent sequencing. We observed that the feed additive lowered C. jejuni caecal count by 0.7 log (p<0.05). Alpha-diversity of the caecal microbiome was not affected by C. jejuni colonization or by the feed additive. C. jejuni colonization modified the caecal beta-diversity while the feed additive did not. We observed that C. jejuni colonization was associated with an increase of Bifidobacterium and affected Clostridia and Mollicutes relative abundances. The feed additive was associated with a lower Streptococcus relative abundance. The caecal microbiome remained relatively unchanged despite high C. jejuni colonization. The feed additive was efficient in lowering C. jejuni colonization while not disturbing the caecal microbiome.
This study was conducted to investigate the effect of dietary protease supplementation on the growth performance, nutrient digestibility, intestinal morphology, digestive enzymes and gene expression in weaned piglets. A total of 300 weaned piglets (21 days of age Duroc × Large White × Landrace; initial BW = 6.27 ± 0.45 kg) were randomly divided into 5 groups. The 5 diets were: 1) positive control diet (PC), 2) negative control diet (NC), and 3) protease supplementations, which were 100, 200, and 300 mg per kg NC diet. Results indicated that final BW, ADG, ADFI, crude protein digestibility, enzyme activities of stomach pepsin, pancreatic amylase and trypsin, plasma total protein, and intestinal villus height were higher for the PC diet and the supplementations of 200 and 300 mg protease per kg NC diet than for the NC diet (P < 0.05). Supplementations of 200 and 300 mg protease per kg NC diet significantly increased the ratio of villus height to crypt depth (VH:CD) of duodenum, jejunum and ileum compared with NC diet (P < 0.05). Feed to gain ratio, diarrhea index, blood urea nitrogen, and diamine oxidase were lower for the PC diet and supplementations of 200 and 300 mg protease per kg NC diet than for the NC diet (P < 0.05). Piglets fed the PC diet had a higher peptide transporter 1 (PepT1) mRNA abundance in duodenum than piglets fed the NC diet (P < 0.05), and supplementations of 100, 200 and 300 mg protease per kg NC diet increased the PepT1 mRNA abundance in duodenum (P < 0.05) comparing with the NC diet. Piglets fed the PC diet had a higher b0,+AT mRNA abundance in jejunum than piglets fed the NC diet (P < 0.05), and supplementations of 200 and 300 mg protease per kg NC diet increased the b0,+AT mRNA abundance in jejunum and ileum comparing with the NC diet (P < 0.05). In summary, dietary protease supplementation increases growth performance in weaned piglets, which may contribute to the improvement of intestinal development, protein digestibility, nutrient transport efficiency, and health status of piglets when fed low digestible protein sources.
It is well known that essential oil thymol exhibits antibacterial activity. The 13 protective effects of thymol on pig intestine during inflammation is yet to be investigated. In this 14 study, an in vitro lipopolysaccharide (LPS)-induced inflammation model using IPEC-J2 cells was 15 established. Cells were pre-treated with thymol for 1 h and then exposed to LPS for various assays. 16 Interleukin 8 (IL-8) secretion, the mRNA abundance of cytokines, reactive oxygen species (ROS), 17 nutrient transporters, and tight junction proteins was measured. The results showed that LPS 18 stimulation increased IL-8 secretion, ROS production, and tumor necrosis factor alpha (TNF-α) 19 mRNA abundance (P < 0.05), but the mRNA abundance of sodium-dependent glucose transporter 20 1 (SGLT1), excitatory amino acid transporter 1 (EAAC1) and H + /peptide cotransporter 1 (PepT1) 21 were decreased (P < 0.05). Thymol blocked ROS production (P < 0.05) and tended to decrease the 22 production of LPS-induced IL-8 secretion (P = 0.0766). The mRNA abundance of IL-8 and TNF-α 23 was reduced by thymol pre-treatment (P < 0.05), but thymol did not improve the gene expression 24 of nutrient transporters (P > 0.05). The transepithelial electrical resistance (TEER) was reduced 25 and cell permeability increased by LPS treatment (P < 0.05), but these effects were attenuated by 26 thymol (P < 0.05). Moreover, thymol increased zonula occludens-1 (ZO-1) and actin staining in 27 the cells. However, the mRNA abundance of ZO-1 and occludin-3 was not affected by either LPS 28 or thymol treatments. These results indicated that thymol enhances barrier function and reduce 29 ROS production and pro-inflammatory cytokine gene expression in the epithelial cells during 30 inflammation. The regulation of barrier function by thymol and LPS may be at post-transcriptional 31 or post-translational levels.32 Intestinal epithelial cells (IECs) are continuously lined monolayer cells, which play important 36 roles in the animal's physical defense. Normally, IECs function as the first line of defense against 37 the invasion of pathogenic agents in the external environment of gut lumen. 1 The maintenance of 38 the barrier function of IECs contributes to the gut homeostasis and health of animals. Gut disorder 39 and dysfunction might be harmful to the growth performance of food-producing animals, and may 40 induce gut diseases such as inflammatory bowel diseases and diarrhea, possibly due to complex 41 interactions among immunologic, genetic, microbial and environmental factors. 2 For instance, 42 diarrhea is a common gut disorders, which causes almost 5% mortality per year in weaned piglets. 3 43 Therefore, it is necessary to prevent gut disorder and diseases by maintaining proper barrier 44 function of IECs in animals. 45 In addition to the physical barrier, IECs also function as an extrinsic barrier. Under certain 46 circumstances, IECs secrete signaling molecules like mucins, cytokines, and chemokines to 47 prevent the invasion of harmful microorganisms in the gu...
The objective was to study the effects of microencapsulated organic acids (OA) and essential oils (EO) on growth performance, immune system, gut barrier function, nutrient digestion and absorption, and abundance of enterotoxigenic Escherichia coli F4 (ETEC F4) in the weaned piglets challenged with ETEC F4. Twenty-four ETEC F4 susceptible weaned piglets were randomly distributed to four treatments including (1) sham-challenged control (SSC; piglets fed a control diet and challenged with phosphate-buffered saline (PBS)); (2) challenged control (CC; piglets fed a control diet and challenged with ETEC F4); (3) antibiotic growth promoters (AGP; CC + 55 mg·kg-1 of Aureomycin); and (4) microencapsulated OA and EO [P(OA+EO); (CC + 2 g·kg-1 of microencapsulated OA and EO]. The ETEC F4 infection significantly induced diarrhea at 8, 28, 34, and 40 hours post-inoculation (hpi) (P < 0.05) in the CC piglets. At 28 days post-inoculation (dpi), piglets fed P(OA+EO) had a lower (P < 0.05) diarrhea score compared to those fed CC, but the P(OA+EO) piglets had a lower (P < 0.05) diarrhea score compared to those fed the AGP diets at 40 dpi. The ETEC F4 infection tended to increase in vivo gut permeability measured by the oral gavaging fluorescein isothiocyanate-dextran 70 kDa (FITC-D70) assay in the CC piglets compared to the SCC piglets (P = 0.09). The AGP piglets had higher FITC-D70 flux than P(OA+EO) piglets (P < 0.05). The ETEC F4 infection decreased mid-jejunal VH in the CC piglets compared to the SCC piglets (P < 0.05). The P(OA+EO) piglets had higher (P < 0.05) VH in the mid-jejunum than the CC piglets. The relative mRNA abundance of SGLT1 and B0AT1 was reduced (P < 0.05) by ETEC F4 inoculation when compared to the SCC piglets. The AGP piglets had a greater relative mRNA abundance of B0AT1 than the CC piglets (P < 0.05). The ETEC F4 inoculation increased the protein abundance of OCLN (P < 0.05), and the AGP piglets had the lowest relative protein abundance of OCLN among the challenged groups (P < 0.05). The supplementation of microencapsulated OA and EO enhanced intestinal morphology and showed anti-diarrhea effects at a one-time point in weaned piglets challenged with ETEC F4. Even if more future studies can be required for further validation, this study brings evidence that microencapsulated OA and EO combination can be useful within the tools to be implemented in strategies for alternatives to antibiotics in swine production.
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