The intense nature of pig production has increased the animals’ exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals’ coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.

Subclinical chronic inflammation (SCI) is associated with impaired animal growth. Previous work has demonstrated that olive-derived plant bioactives exhibit anti-inflammatory properties that could possibly counteract the growth-depressing effects of SCI. To test this hypothesis and define the underlying mechanism, we conducted a 30-day study in which piglets fed an olive-oil bioactive extract (OBE) and their control counterparts (C+) were injected repeatedly during the last 10 days of the study with increasing doses of Escherichia coli lipopolysaccharides (LPS) to induce SCI. A third group of piglets remained untreated throughout the study and served as a negative control (C-). In C+ pigs, SCI increased the circulating concentration of interleukin 1 beta (p < 0.001) and decreased feed ingestion (p < 0.05) and weight gain (p < 0.05). These responses were not observed in OBE animals. Although intestinal inflammation and colonic microbial ecology was not altered by treatments, OBE enhanced ileal mRNA abundance of tight and adherens junctional proteins (p < 0.05) and plasma recovery of mannitol (p < 0.05) compared with C+ and C-. In line with these findings, OBE improved transepithelial electrical resistance (p < 0.01) in TNF-α-challenged Caco-2/TC-7 cells, and repressed the production of inflammatory cytokines (p < 0.05) in LPS-stimulated macrophages. In summary, this work demonstrates that OBE attenuates the suppressing effect of SCI on animal growth through a mechanism that appears to involve improvements in intestinal integrity unrelated to alterations in gut microbial ecology and function.

A 10-week growth trial was conducted to investigate the effects of a phytogenic feed additive (PFA) containing olive by-products and green tea extracts supplemented to a reduced fishmeal/high soybean meal diet on the growth performance, hepatic antioxidant capacity, lipid metabolism, and liver health of largemouth bass (Micropterus salmoides). Three experimental diets were tested: (1) a control high fishmeal (40%) and low soybean meal (15.57%) diet (named HFM), (2) a reduced fishmeal (30%) and high soybean meal (30.97%) diet (named HSB), and (3) a HSB diet supplemented with the PFA at 500 mg/kg (named HSB+P). Each diet was assigned to four replicate tanks, each containing 30 largemouth bass (initial body weight, IBW = 48.33 ± 0.01 g). The results showed that increasing the soybean meal content in the diet did not negatively affect growth performance, whereas supplementation with PFA significantly increased weight gain and specific growth rate of largemouth bass compared to both HFM and HSB groups. Reducing fishmeal and increasing soybean meal in the diet caused oxidative stress with a higher content of ROS in the liver. However, the hepatic antioxidant capacity was enhanced, with reduced ROS and increased GSH-Px levels in the HSB+P group. Moreover, the decrease of plasma TG, LDL-C, and LDL-C/TC, and downregulation of lipogenesis and cholesterol synthesis gene expression in liver, indicated that supplementation with the PFA improved fish lipid metabolism. Protein retention efficiency was also significantly increased in largemouth bass fed the diet with PFA supplementation, which regulated (enhanced) AKT-mTOR phosphorylation. These results clearly indicated that a PFA containing olive by-product and green tea extracts can positively improve growth performance, protein retention efficiency, antioxidant capacity, and lipid metabolism of largemouth bass fed a reduced fishmeal/high soybean meal diet.

This study aimed to investigate the effects of supplementing broiler chicken diets with an encapsulated product based on capsicum and other spice (black pepper and ginger) extracts on growth performance, nutrient digestibility, digestive enzyme activity and antioxidant response. To this end, 480 1-day-old male chicks were randomly assigned to two experimental treatments (12 pens/treatment; 20 birds/pen). Dietary treatments included a basal diet with no additives (CONTROL) and a basal diet supplemented with 250 ppm of the spice additive (SPICY; Lucta S.A., Spain). Supplementation of SPICY increased body weight (p < 0.05) compared with CONTROL at 7 d of age and improved (p < 0.01) ADG from 0 to 7 d of age. The apparent ileal digestibility of dry matter, gross energy and crude protein was higher (p < 0.05) in birds fed the SPICY diet compared with the CONTROL diet. Birds fed SPICY showed lower (p < 0.05) plasma catalase (CAT) activity, and the hepatic gene expression of CAT and Nrf2 was down-regulated (p < 0.05) compared with the CONTROL. In conclusion, the inclusion of 250 ppm of SPICY in broiler diets improved growth performance at 7 d of age and positively affected nutrient digestibility and antioxidant response.

Feed restriction and fasting experienced during commercial production negatively affect unweaned calves' behavior and health status. Transportation and stays at assembly centers are the main factors generating these disorders. For this study, 20 unweaned Angus-Holstein bull calves [44.1 ± 2.04 kg of body weight (BW) and 14.7 ± 0.63 d of age (± standard error)] were used to evaluate the effects of feed restriction and fasting on performance, energy status [serum concentration of glucose, β-hydroxybutyrate (BHB), and nonesterified fatty acids], and gastrointestinal permeability [serum concentration of citrulline, chromium (Cr)-EDTA, lactulose, and d-mannitol]. Calves were randomly assigned to 1 of 4 treatments that simulated the feed restrictions of an assembly center situation on one hand, and the fasting hours during transportation on the other. Treatments were as follows. Control (CT): from d -4 to -1, calves were fed 2.5 L of milk replacer (MR) twice daily; concentrate and straw were offered ad libitum. Mild (MD): calves were fed only MR (d -4 to -1) as described for CT, and on d -1 calves were subjected to a 9-h feed withdrawal. Moderate (MO): calves were fed only MR (d -4 to -1) as described for CT and on d -1 subjected to a 19-h feed withdrawal. Severe (SV): calves were fed only 2.5 L of a rehydrating solution twice daily (d -4 to -1) and on d -1 subjected to a 19-h feed withdrawal. From d 0 to d 42 (weaning) all calves were fed the same feeding program (MR, concentrate, and straw ad libitum). Results showed that BW was greater for the CT treatment compared with the others from d 0 to d 7, whereas BW of SV was lesser compared with the others from d -1 to d 7. No differences among treatments were observed at weaning. At d 2 concentrate intakes of MD, MO, and SV were lesser compared with CT. By d 4, concentrate intake of SV was similar to that for CT and greater than MD and MO. Similarly to BW, no differences in concentrate intake among treatments were observed at weaning on d 42 of the study. At d -1 for SV and d 0 in all restricted calves, serum glucose concentration was lesser compared with CT. At d -1 and 0, nonesterified fatty acids and BHB serum concentrations were greater in the SV calves compared with the other treatments. By d 2, serum concentrations of nonesterified fatty acids, BHB, and glucose were restored to CT levels. At d -1 serum citrulline concentration was lesser in SV and greater in MD calves. The CT calves had lower serum concentrations of Cr-EDTA (d -1 and d 0), lactulose (d 0), and d-mannitol (d 0) compared with the other restricted calves. Results showed that degree of dietary restriction, type of liquid diet (MR or rehydrating solution), and fasting hours (9 vs. 19 h) affected calves' BW, concentrate intake, and serum concentration of markers indicative of energy status and gastrointestinal permeability.

Olives are a rich source of compounds with antioxidant and anti-inflammatory activities. This study was designed to investigate whether a standardized olive cake extract was able to alleviate oxidative stress, inflammation and intestinal villus damage in a model of lipopolysaccharide (LPS)-challenged piglets. Thirty weaned piglets (6.9 ± 0.9 kg) were assigned to five groups using a randomized complete block design. Piglets were fed a basal diet before intraperitoneal (i.p.) injection of physiological saline (C); fed a basal diet alone (CL) or fed a basal diet plus an olive cake extract (OL), antibiotics (AL), or olive cake extract plus antibiotics (OAL) before i.p. injection of LPS. The feeding period lasted for 2 weeks. Piglets were euthanized 4 h after the LPS injection. Systemic oxidative and inflammatory status and intestinal morphology were evaluated. LPS challenge significantly lowered the serum levels of GSH-Px, SOD and ALB and increased the serum concentration of MDA, NO, LDH, ALT, AST, TNF-α, IL-6, DAO and D-xylose (P < 0.05), as extracted from the comparison of piglets in the C and CL groups. Intestinal morphology was altered in the duodenum and ileum, displaying that the CL group had significantly lower villus height (VH), higher crypt depth (CD) and lower VH/CD compared with the control group (P < 0.05). Moreover, feed supplementation was able to partially mitigate the negative effects of LPS challenge in all groups (OL, AL, and OAL), as evidenced by the significantly increased serum levels of GSH-Px, SOD, ALB and IL-10 and decreased concentration of MDA, NO, LDH, ALT, AST, TNF-α, IL-6, DAO and D-xylose, compared with the CL group (P < 0.05). Alterations in intestinal morphology were also prevented and the OL, AL, and OAL groups had significantly lower CD and higher VH/CD compared with the CL group (P < 0.05), both in the ileum and duodenum. Furthermore, the positive effect in the relative abundance of intestinal Lactobacillus and Clostridium at the genus level was also observed for the OL group compared to the CL group. In summary, dietary supplementation with an olive cake extract stabilized the physiological condition of piglets subjected to an acute LPS challenge by reducing oxidative stress and the inflammatory status, improving intestinal morphology and increasing the abundance of beneficial intestinal bacteria. This trial was registered at Zhejiang University (http://www.lac.zju.edu.cn) as No. ZJU20170529.