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Finding alternatives to zinc oxide is a pressing issue for the pig production sector. We studied the impact of the bioactive components degradation of oregano essential oil (OEO) and purple garlic powder (PGP) during storage in silos, their effect on the morphometry of the jejunum and ileum and the cecal microbiota as intestinal health indicators in piglets during the post-weaning period. We also monitored antimicrobial resistance in the commensal indicator E. coli. Histological parameters and intestinal microbiota were measured in 140 piglets weaned at 21 days of age. Seven dietary treatments were used: a negative control group (basal diet), a positive control group with ZnO (3000 mg/kg of food), two groups with OEO at 0.4% and 1.2%, respectively, two groups with PGP 0.4% and 2%, respectively, and a group with OEO with 1.2% combined with PGP with 2%. Each group of piglets received the treatment for seven weeks, from weaning, before samples were taken. Antibiotic resistance profiles were measured in 81 E. coli strains. On this occasion, only the control groups, ZnO, OEO 1.2%, PGP 2% and OEO 1.2% + PGP 2% were used, and the samples were obtained from the cecal content. A progressive loss of the bioactive components of OEO and PGP was observed during the 34 days of storage ( p < 0.05). PGP 2%, OEO 1.2% and their combination showed results similar to ZnO ( p > 0.05), or superior in the study of intestinal morphometry and the values of E. coli and Lactobacillus. All categories showed high levels of resistance. Only the strains isolated from the OEO 1.2% group did not show resistance to colistin and presented the lowest resistance values. In general, high doses of the additives studied showed the best results, obtaining levels like or higher than those offered by ZnO.

Antimicrobial resistance (AMR) is a global threat for human and animal health. Few studies have been carried out in laying hens. We evaluated the antimicrobial susceptibility of commensal Campylobacter jejuni , Escherichia coli , and Enterococcus faecalis isolates in Spanish laying hens in 2018. The Minimum Inhibitory Concentration (MIC) was used to identify any AMR of the studied isolates by means of a broth microdilution method. C. jejuni was highly resistant to the B category antimicrobials, and 52% of the isolates were susceptible to all the antimicrobials tested. E. coli showed medium and high percentages of resistance to the B and A antibiotic categories, respectively, and 33.33% of the isolates were susceptible to all antimicrobials. The E. faecalis resistance to A category antimicrobials was variable, and 4.62% of the isolates were susceptible to all antimicrobials. In our work, novel data on AMR in laying hen commensal isolates in Spain is provided, and the AMR levels differ from those reported for poultry in the EU. A high resistance to key drugs for human medicine was found, representing a public health risk.

The effects of two different concentrations of micro capsuled oregano essential oil (OEO) and purple garlic powder on biomarkers of oxidative status, stress, and inflammation, as well as on average daily gain (ADG) and feed conversion ratio (FCR), were evaluated in piglets during the postweaning period. The trial was carried out with 300 crossbred pigs of 21 days of age fed with different concentrations of OEO and purple garlic powder and ZnO. Saliva and serum samples were taken to evaluate a panel of biomarkers of oxidative status, stress, and inflammation. OEO and garlic powder at 0.4% did not produce significant changes in C-reactive protein (CRP) and cortisol and yielded higher levels of the antioxidant biomarker CUPRAC in serum than higher doses ( p < 0.01); they yielded a better ADG than the control and ZnO diets. OEO and garlic powder at higher concentrations than 0.4% showed higher concentrations of CRP ( p < 0.05). Overall, doses of OEO and garlic powder at 0.4% did not lead to inflammation, stress, or negative changes in oxidative biomarkers in piglets during the postweaning period and gave better productive performance than the control and ZnO diets. High doses of OEO and garlic powder were ineffective and could negatively affect the animals. Therefore, our results highlight the importance of the dose used when OEO or garlic are supplemented to piglets.