When poultry is under oxidative stress, the complex regulatory mechanism of the body will be activated, and the energy required for growth will be used to resist the oxidative damage caused by the body, resulting in the decline of the growth performance of the poultry, and even death in severe cases (Taleb et al. 2018). In production, antioxidant substances are often added to poultry diet or drinking water to prevent oxidative stress (Han and Song 2021). In scientific research, in order to study oxidative stress related experiments, hormones, fatty acids, Diquat, bacterial lipopolysaccharides, etc. are usually used to build oxidative stress models (Reckelhoff et al. 2019). Diquat-induced oxidative stress disrupts the body's oxidative defenses, causes liver and small intestine damage, triggers acute inflammation, and inhibits nutrient absorption, resulting in decreased animal growth performance (Chen et al. 2020). Research on the effects of diquat-induced oxidative stress on livestock growth performance has focused on piglets (Azad et al. 2021; Cao et al. 2018; Doan et al. 2020). In this research, the intraperitoneal administration with diquat reduced ADG change rate during 8 ~ 21d in Lohmann chicks. Chen et al (2020) have found that the intraperitoneal administration with diquat reduced ADG and BW change rate during the 24-h post-challenge in broiler chicks, this is consistent with the results of this study. The present study also showed that intraperitoneal injection of diquat decreased the SOD, GST and GSH-Px activities of the plasma and liver, and increased the MDA concentration of the plasma and liver in the chicks. These results indicated that the oxidative stress model induce by diquat injection was successful. which is consistent with our previous studies (Wang et al. 2022). Some studies have pointed out that the most likely reason for the decline in growth performance is that diquat-induced oxidative stress generates ROS, which leads to lipid peroxidation, increases the permeability of cell biofilms, affects the function of biofilms, and leads to mucosal damage and infection in the digestive tract (Cao et al. 2019; Doan et al. 2020). When the digestion and absorption function of animals is reduced, the functional cells related to digestion and absorption will die rapidly, and the animals will experience symptoms such as vomiting, diarrhea, and anorexia, which will eventually lead to a decrease in feed intake and daily gain, and an increase in feed-to-weight ratio (Sun et al. 2021).
GSE contains proanthocyanidins, grape polyphenols, bioflavonoids and other biologically active substances, which have various effects such as scavenging free radicals, anti-oxidation, anti-aging, antibacterial and anti-inflammatory, and enhancing immunity (Parandoosh et al. 2020). OPE contains high levels of flavonols and its derivatives, which are a class of flavonoid bioactive substances that can scavenge free radicals, sterilize and reduce inflammation (Masood et al. 2021). The most important bioactive substances in ROE are terpenes, phenols and acids, which have strong anti-tumor, anti-viral, antibacterial, and antioxidant effects (Pourbabaki et al. 2020). During the period without Diquat injection, compared with the blank group, the addition of grape seed extract to the chick's diet significantly improved the growth performance of chicks, which may be the main reason why grape seed extract improves the growth performance of oxidatively stressed chicks. During the period with Diquat injection, compared with the NC group, the addition of onion peel extract and rosemary extract to the chick's diet significantly improved the growth performance of chicks. However, the growth performance of chicks did not differ among the NC, OPE and ROE groups prior to diquat challenge, and this may be owing to the normal physiological status of chicks and the healthy feeding environment in this study.
Blood is an important part of the circulatory system and participates in every metabolic activity in the body (Grüneboom et al. 2019). The normal metabolic activities of the body are closely related to the routine blood indicators, which are extremely important to maintain the normal internal and external environment of the body (Congleton et al. 2006). Therefore, the number and morphological distribution of blood cells in the blood index are important basis for judging the health of the body (Simide et al. 2016). In our previous study, intraperitoneal injection of diquat at a dose of 10 mg/kg body weight significantly increased the blood PDW concentration, the levels of red and white blood cells also increased, but not significantly. This suggests that injection of diquat causes oxidative stress in chickens, resulting in infection and inflammatory responses in chicks. The PDW in the blood of the GSE and OPE groups were lower than that of the NC group, indicating that GSE and OPE can rapidly prevent the increase of PDW after Diquat caused infection and inflammation, and help the body fight infection and inflammation (Grüneboom et al. 2019). In this experiment, we found that the RBC, HGB, HCT index values in the blood of the PC group were lower than those of the other groups (injected with diquat). Studies have proven that under conditions of acute oxidative stress caused by diquat, animals had enhanced respiration, increased basal metabolic levels, and increased oxygen consumption, resulting in elevated RBC, HGB, and HCT (El-Deen et al. 1992). The HGB in the blood of the GSH group was significantly higher than that of the PC group. GSE, OPE and ROE could increase the oxygen-carrying capacity of the blood, provide more oxygen for respiration, relieve the hypoxia symptoms caused by Diquat, and help the chickens return to normal as soon as possible.
Diquat is widely considered as an effective chemical agent for inducing oxidative stress, which of the major target organ is the liver (Mao et al. 2014). In our previous study, intraperitoneal injection of diquat at a dose of 10 mg/kg body weight significantly increased the plasma ALT and AST activities. ALT and AST were mainly distributed in the liver cells. The concentrations of ALT and AST in serum reflect the degree of liver damage, and the higher the concentrations of ALT and AST, the more serious the liver damage (Qiao et al. 2020). When the phospholipid bilayer on the biomembrane in the liver cells is lipidated, the glycoprotein is damaged, the permeability of the biomembrane is enhanced, and the cells are apoptotic, causing the ALT and AST in the liver to enter the blood, and the ALT and AST in the blood increase (Jia et al. 2020). The present study showed that, compared with the PC group, the serum ALT and AST concentrations of the NC group were significantly increased. Under the condition of Diquat-induced oxidative stress, the NC group chickens developed oxidative stress symptoms of liver damage, which is consistent with the findings of Strange et al. The concentrations of TP, ALB and GLB in serum also reflect the protein synthesis function of the liver and the nutritional status of the body (Guo et al. 2022). This study showed that the concentrations of TP, ALB, and GLB in serum were lower in the NC group than in the PC group, and Diquat induced oxidative stress to damage liver function. Studies have shown that GSE, OPE and ROE have an improving effect on liver function (Çetin et al. 2008; Elhassaneen et al. 2014; Singletary et al. 1996), it is consistent with the results in this experiment.
When livestock and poultry undergo oxidative stress, the ROS produced in the animal exceeds the scavenging ability of the antioxidant enzyme system and non-enzymatic system in the body, and the antioxidant capacity of livestock and poultry will decrease (Taleb et al. 2018). The most direct reflection is that the concentration of antioxidant enzymes decreases, including SOD, GSH-Px, GST and other enzymes (Manafi et al. 2014). In this experimental study, antioxidant capacity of chicks decreased after Diquat injection. The injection of Diquat in chicks will induce a large amount of ROS produced by the body, breaking the balance of the normal antioxidant system (Taleb et al. 2018). Research showed that in the oxidative stress model of broiler chickens induced by cortisone, the content of MDA in serum, liver and muscle tissue was significantly increased, while SOD and GSH-Px were significantly reduced, which was similar to the results of this experiment (Chen et al. 2020). In animals under oxidative stress, unsaturated fatty acids are oxidized into lipid peroxides, which are finally decomposed to form MDA (Radwan et al. 2014). Therefore, the content of MDA in the body directly reflects the degree of lipid peroxidation in the body, as well as the degree of oxidative damage (Han et al. 2021). In this experiment, the MDA content in serum and liver of NC group was significantly higher than that of PC group. Some scholars believe that the increase and decrease of antioxidant enzymes are the protective mechanism of the antioxidant enzyme system (Radwan et al. 2008). In a healthy state, antioxidant enzymes are maintained at a relatively constant, balanced, and low concentration level (Ognik et al. 2016). In the early stage of oxidative stress, the antioxidant enzyme system and non-enzymatic system in the body remove free radicals in the body and restore the body to normal (Doan et al. 2020). When the free radicals in the body exceed the scavenging ability of the antioxidant enzyme system and the non-enzyme system, the level of antioxidant enzymes in the body will be reduced, and the body will be in a state of oxidative stress (Reckelhoff et al. 2019). Many plant extracts and plant products have been shown to have significant antioxidant activity. It is well known the plant extract constituents could influence the differences in the antioxidant ability of plant extracts (Radwan et al. 2008). In this experiment, the antioxidant activity and free radical scavenging properties of each plant extract were different, among which GSE had the best antioxidant activity. Studies have shown that dried grape seeds (ORAC values 108130 µm TE/100 g) and rosemary (ORAC values 165280 µm TE/100 g) have higher antioxidant capacity in vitro, and dried onion (ORAC values 4289 µm TE/100 g) had lower antioxidant capacity (Brewer et al. 2011; Celano et al. 2021). The antioxidant capacity of these plant extracts in animals can also be found in the literature (Han and Song 2021; Manafi et al. 2014; Sogut and Seydim 2018), but none of the papers have compared the antioxidant capacity of these three in vivo simultaneously.
In conclusion, the acquired results in this study suggested that dietary supplementation with grape seed extract, onion peel extract or rosemary extract can improve growth performance, antioxidant status in plasma and liver, and liver function of Lohmann chicks subjected to diquat-induced oxidative stress. Additionally, based on the results of this study, under normal or oxidative stress conditions, adding grape seed extract to the diet can better improve the growth performance and antioxidant capacity of chicks compared with the OPE and ROE groups.