Alterations of endotoxin distribution across different biofluids and relevant inflammatory responses by supplementing L-theanine in dairy cows during heat stress

The present trial was performed to reveal the regulatory effects of L-theanine on the levels of lipopolysaccharide(LPS)endotoxin within different biofluids,as well as relevant inflammatory responses of dairy cattle under heat stress conditions.Thirty lactating Chinese Holstein dairy cattle(189±47 d in milk,and 2±1 parities)were allocated in a completely randomized design to each of 3 dietary treatments:the control(CON,0 g/d per cow L-theanine),the low L-theanine dosage treatment(LL,16 g/d per cow L-theanine),and the high L-theanine dosage treatment(HL,32 g/d per cow L-theanine).This trial consisted of 38 d(7 d for adaption and 31 d for data and sample collection),and sample collection for rumen liquid,blood plasma or serum,and milk were conducted on the d 27 and 38,respectively.Dairy cattle were constantly exposed to environmental heat stress during this experiment according to the recorded temperature-humidity index(THI).In the LL treatment,LPS concentration in rumen liquid was higher(P<0.05),whilst LPS densities in plasma and milk were lower(P<0.05)than those of the CON.Supplementing L-theanine at 2 dosages both significantly lowered(P<0.05)the level of interleukin(IL)-1βin the serum.Results of the present study suggested that L-theanine could be a promising additive in reducing the detrimental effects of heat stress on dairy cows,and L-theanine supplementation at 16 g/d per cow is preferred because it reduced the LPS translocation into the peripheral blood and LPS accumulation in the milk,as well as mitigated LPS-induced inflammatory reactions in dairy cows during heat stress.Further studies are necessitated to investigate the underlying mechanisms of L-theanine in LPS alteration and inflammation alleviation.

Alterations in nutrient digestibility and performance of heat-stressed dairy cows by dietary L-theanine supplementation

The purpose of this study was to investigate the effects of dietary L-theanine supplementation on apparent nutrient digestibility,milk yield,milk composition,and blood biochemical indices of dairy cows under heat stress.Thirty Chinese Holstein cows(19.84±2.42 kg milk/d,192.36±40.77 d in milk and2±0.93 parities)were divided into 3 groups of 10 animals each.The control group was fed a basal total mixed ration(TMR)diet,while treatment 1(LTA16)and treatment 2(LTA32)groups were fed a basal TMR diet supplemented with L-theanine at 16 and 32 g/cow per day,respectively.The results showed that feeding the dairy cows with LTA16 treatment decreased(P<0.05)their rectal temperature,whereas feeding with LTA32 treatment decreased(P<0.05)their rumen fluid ammonia nitrogen content.In comparison to the control group,the supplementation of L-theanine had no significant effect(P>0.05)on the dry matter intake,nutrient digestibility,total volatile fatty acid(TVFA)concentration and molar proportion of volatile fatty acid,milk yield,milk composition,feed efficiency and antioxidant capacity of the dairy cows.The triglyceride(TG)content of the LTA32 group was significantly greater(P=0.014)than that of the control group.With the increase in L-theanine dosage,the serum cholesterol(CHOL)content significantly increased(P=0.013).The serum albumin(ALB;P=0.067),low-density lipoprotein cholesterol(LDL-C;P=0.053),and high-density lipoprotein cholesterol(HDL-C;P=0.067)contents showed an upward trend as L-theanine dosage increased.Ultimately,the results of this study show that supplementing dairy cow diet with L-theanine could decrease dairy cow rectal temperature,affect lipid metabolism,and potentially relieve the heat stress of dairy cows to some extent.