| Heat Stress(HS)causes significant economic losses to livestock production and is one of the main causes of oxidative stress and damage to the intestinal tract of livestock.The use of antioxidants to alleviate this stress is the preferred option.Hydrogen-rich water(HRW)is a drinkable functional water with anti-oxidative stress effects due to its highly reducing hydrogen content,but it has a long duration of action when given alone.Research into the use of HRW in combination with other substances to increase effectiveness and shorten the duration of action is beginning to attract attention.Tea Polyphenols(TP)is a natural antioxidant extracted from tea leaves,which is highly effective in scavenging harmful and excess free radicals in the body and has various biological activities such as antioxidant,antibacterial and anti-inflammatory.Therefore,the use of HRW in combination with TP may improve heat stress relief.In order to test this hypothesis,this paper firstly constructs a mice model of heat stress,and then investigates the effect of HRW combined with TP on its antioxidant activity in vitro,and selects a combined method of HRW drinking combined with TP intraperitoneal injection,and uses this method in the established mouse model of heat stress.This study will provide a theoretical basis for the further development and application of HRW combined with TP.The main findings of the study are as follows:Experiment 1 Heat Stress modellingA total of 24 SPF class ICR mice were used in the experiment and were divided into a control group and a heat stress group.Each group had 3 replicates of 4 mice each.They were housed for 3 d for acclimatisation and 28 d for the formal trial.To study the effects of heat stress on growth performance,body temperature,organ indices,antioxidant indices,HSP70 levels in mice and jejunal pathology.The results showed that the ADG and ADFI of mice in the HS group were significantly lower compared to those in the CT group(P < 0.05);a significant increase in ADWI and body temperature(P < 0.05);significant decrease in liver indices(P < 0.05)and non-significant differences in kidney,heart and spleen indices(P > 0.05)in mice.The levels of SOD,CAT and GSH-Px in plasma,jejunum and liver tissues were significantly decreased(P < 0.05)and the levels of MDA and HSP70 were significantly increased(P < 0.05);Histopathological sections of the jejunum showed that the arrangement of the villi was significantly disturbed,shortened and thickened,and the VH and V/C ratios were significantly reduced(P < 0.05).The method was successful in establishing a heat stress model in mice.Experiment 2 HRW combined with TP in vitro antioxidant studyTo address the issue of the combined method of HRW and TP,this experiment was conducted to determine the radical scavenging rate of DPPH,hydroxyl radical scavenging ability,reducing ability and ABTS scavenging ability to investigate the in vitro antioxidant properties of HRW-conjugated tea polyphenols.There are three groups: the HRW group,the TP group and the combination of HRW and TP(HRW +TP,TP dissolved in HRW).The results showed that the in vitro antioxidant capacity was comparable: TP > HRW + TP > HRW,suggesting that further testing would be best in heat-stressed mice given the two separately.Experiment 3 HRW combined with TP to alleviate intestinal damage in heat-stressed miceTo address the question of whether HRW combined with TP would alleviate oxidative stress injury in heat-stressed mice,a total of 60 SPF-rated ICR mice were used in this chapter of the experiment and randomly divided into CT,HS,HRW,TP and HRW + TP groups.Each group had 3 replicates of 4 mice each.They were housed for 3 d for acclimatisation and 28 d for the formal trial.The heat stress model was established by referring to experiment 1.The effects of HRW combined with TP on growth performance,body temperature,antioxidant index,mouse HSP70 level,jejunal pathology and intestinal flora of heat-stressed mice were investigated.The results showed that the ADG and ADFI of the HRW + TP group were significantly higher than those of the HS and HRW groups(P < 0.05)and not significantly different from those of the TP group(P > 0.05),and the ADWI was significantly lower than those of the HS and HRW groups(P < 0.05)and not significantly different from those of the TP group(P > 0.05);the body temperature of mice increased significantly after heat stress(P < 0.05).Comparison of the effect of heat stress relief:HRW + TP > TP > HRW.In addition,the levels of SOD,CAT and GSH-Px were significantly higher(P < 0.05),MDA levels were significantly lower(P < 0.05)and HSP70 levels were significantly lower(P < 0.05)in plasma,jejunum and liver tissues of mice treated with HRW + TP,TP and HRW after heat stress compared to the HS group.Among the treatment groups,the level of antioxidant enzyme expression in the HRW + TP group was significantly higher than that in the TP and HRW groups(P <0.05),and its MDA level was significantly lower than that in the TP and HRW groups(P < 0.05).Histopathological sections of the jejunum also showed a significant increase in the villi ratio in the HRW + TP group compared to the rest of the groups(P< 0.05),which could better alleviate the significant disorganization,shortening and thickening of the jejunal villi in the mice.A study of the structure of HRW combined with TP on the intestinal flora of heat-stressed mice using 16 S r DNA high-throughput sequencing revealed that:HRW combined with TP significantly increased the species richness and diversity of the intestinal flora reduced by heat stress.In particular,the beneficial phyla Firmicutes,Bacteroidota and Actinobacterioda,and the beneficial genera Lachnospiraceae＿NK4A136＿group and Lactobacillus were significantly increased in abundance.The abundance of beneficial genera such as Lactobacillus and the abundance of harmful phylum Desulfovibrio and harmful genera Desulfovibrio and Enterorhabdus were reduced.It has beneficial effects on the structure and function of the intestinal flora of heat-stressed mice.In conclusion,HRW combined with TP can effectively promote the growth performance of heat stress model mice,alleviate the oxidative damage to serum,liver and jejunal tissues caused by heat stress,reduce the level of heat shock protein 70 in the body,improve the structure of intestinal microflora,and have a better protective effect on intestinal damage in heat stressed mice. |
