Abstract
Intensive farming systems represent a stressful environment for pigs and negatively influence neuroendocrine functions, behavior, and performance. Outdoor farming is an alternative option, which is thought to imply several beneficial effects for the animal. Dietary essential oils are known to be an innovative strategy to improve pig health and performance, and oregano essential oil (ORE) possesses beneficial effects due to its antimicrobial, anti-fungal, and antioxidant properties. We tested the effect of dietary ORE on peripheral blood mononuclear cells (PBMCs) in 36 growing pigs, either reared under indoor or outdoor conditions. Quantitative real-time PCR (RT-qPCR) assay was used to evaluate the effect of diet (control vs. ORE) and the time of sampling (T1−120 days vs. T2−190 days) on the expression of inflammatory and immune-related genes (TNF, IL1β, IL8, IL18, IL10, IL1RN, STAT3, HSP90, ICAM-1, and NFKB1). Under outdoor condition, the majority of transcripts were upregulated (p < 0.05), assuming a general inflammatory status (TNF, HSP90, NFKB1, IL1β, and STAT3). However, an interaction between diet and the farming system was observed: HSP90, NFKB1, and STAT3 were downregulated (p < 0.05) in the outdoor reared pigs when fed the ORE diet. Our study showed that bioactive compounds of ORE exert their activity, especially when the animals are exposed to stressful stimuli. Dietary ORE can be an acceptable strategy to help pigs tolerate the stress related to the harsh, outdoor, rearing conditions.
Highlights
The increase in demand of meat production has led to a worldwide increase in intensive farming systems, which usually represent a stressful environment for the animals [1]
Animals were balanced for live weight (LW) and litter and blocked into four groups according to a 2 × 2 factorial design: two rearing systems, (a) Outdoor (OUT): ∼280 m2/pig in outdoor pens provided with huts for shelter and (b) Indoor (IN): 2 m2/pig in a building with natural ventilation and wheat straw for bedding), and two dietary treatments
To evaluate the most stable genes to be used for normalization purposes, six potential Reference Genes (RGs) (ACTB, B2M, GAPDH, hypoxanthine ribosyltransferase (HPRT), ribosomal protein L4 (RPL4), and SDHA) were tested in 48 samples, randomly chosen at each time point (T0, T1, T2), at the farming system (IN, OUT), and at diet treatment (CTRL, ORE)
Summary
The increase in demand of meat production has led to a worldwide increase in intensive farming systems, which usually represent a stressful environment for the animals [1]. The outdoor farming system is generally considered a better strategy to improve animal welfare and health compared to the intensive indoor farming, even though beneficial and stressful stimuli in both rearing systems can influence performance [2, 6,7,8,9,10,11]. With increased space being available and the more natural environment in outdoor farming representing advantages to improve pig welfare [12, 13], the harsh environmental conditions can negatively influence the performance of the animals [6, 7, 14, 15]. Lymphocyte proliferation and natural killer cell activity can be impaired by acute exposure to thermal stress [19,20,21] and, in addition to the environmental stressor, exercise exacerbates the reaction of the immune system and activates pro-inflammatory and antiinflammatory pathways, depending on the intensity and duration of stress [22, 23]
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