Evaluation of Holstein cows with different tongue‑rolling frequencies:stress immunity,rumen environment and general behavioural activity

Background The tongue-rolling behaviour of cows is regarded as an outward sign of stressed animals in a low welfare status.The primary aim of this observational study was to evaluate the association between the frequency of tongue-rolling behaviour and its physiological function.The secondary aim was to explore the relationship between general activities and the frequency of tongue-rolling behaviour of cows.A total of 126 scan sampling behavioural observations were collected over 7 d on 348 Holstein cows with the same lactation stage in the same barn.The tongue-rolling frequency was defined as the number of tongue-rolling observations as a percentage to the total observations per individual cow.According to their tongue-rolling frequency,the cows were grouped into the CON(no tongue-rolling),LT(frequency 1%),MT(frequency 5%),and HT(frequency 10%)groups.Six cows from each group were randomly selected for sampling.Serum samples,rumen fluid,milk yield,and background infor-mation were collected.The general behaviour data during 72 continuous hours of dairy cows,including eating time,rumination time,food time(eating time+rumination time),and lying time,were recorded by the collar sensor.Results Cortisol(P=0.012),γ-hydroxybutyric acid(P=0.008),epinephrine(P=0.030),and dopamine(P=0.047)levels were significantly higher in tongue-rolling groups than in the CON group.Cortisol levels and tongue-rolling frequency had a moderate positive correlation(linearly r=0.363).With the increase in tongue-rolling frequency,the rumen pH decreased first and then increased(P=0.013),comparing to the CON group.HT cows had significantly less food time than CON cows(P=0.035).The frequency of tongue-rolling had a moderate negative relationship with rumination time(r=-0.384)and food time(r=-0.492).Conclusions The tongue-rolling behaviour is considered as a passive coping mechanism,as the stress response in cows with high tongue-rolling frequency increased.Food intake and rumination activities were all closely related to the occurrence of tongue-rolling behaviour.

USING NUTRITIONAL STRATEGIES TO MITIGATE RUMINAL METHANE EMISSIONS FROM RUMINANTS

Within the agricultural sector,animal production contributes to 14.5%of global anthropogenic greenhouse gas emissions and produces around 37%of global CH_(4) emissions,mainly due to ruminal fermentation in ruminants.Over 90%of CH_(4) is synthesized by methanogens in the rumen during carbohydrate fermentation.According to different substrates,methanogenesis pathways can be divided into four categories:(1)hydrogenotrophic pathway;(2)acetoclastic pathway;(3)methyl dismutation pathway;and(4)methylreducing pathway.Based on the principle of biochemical reactions in the methanogenesis pathways,this paper reviews the latest publications on CH_(4) decreases in ruminants and described three nutritional strategies in terms of dietary nutrient manipulation(feeding management,feed composition,forage quality and lipids),microbial manipulation(ionophore,defaunation,methanogen inhibitors and probiotics),and chemical manipulation(nitrate,organic acids,plant secondary metabolites and phlorotannins,or halides in seaweeds).For each mitigation strategy,the review discusses effectiveness for decreasing CH_(4) emissions,application prescription,and feed safety based on results from in vitro and in vivo studies.This review summarizes different nutritional strategies to mitigate CH_(4) emissions and proposed comprehensive approaches for future feeding interventions and applications in the livestock industry.

Effects of dietary inclusion with rapeseed cake containing high glucosinolates on nitrogen metabolism and urine nitrous oxide emissions in steers

Two consecutive trials were conducted to investigate the effects of glucosinolates(GLS)in rapeseed cake(RSC)on nitrogen(N)metabolism and urine nitrous oxide(N_(2)O)emissions in steers.In trial 1,8 steers and 4 levels of RSC,i.e.0,2.7%,5.4%and 8.0%dry matter(DM)(0,6.0,12.1,18.1 mmol GLS/g DM)were allocated in a replicated 4×4 Latin square.In trial 2,the static incubation technique was used for measuring the N_(2)O emissions of the urine samples collected from trial 1.The results of trial 1 indicated that dietary inclusion of RSC decreased the digested N and increased the fecal N excretion(P<0.01),whereas it did not affect the urinary N excretion,total N excretion and N retention(P>0.10).Dietary inclusion of RSC decreased the urinary excretion of urea while it increased allantoin,total purine derivatives,the predicted rumen microbial N flow and thiocyanate(SCN)(P<0.05).Dietary inclusion of RSC did not affect the plasma triiodothyronine and thyroxine while it down-regulated the plasma relative concentrations of 4-aminohippuric acid,3a,7a-dihydroxycoprostanic acid,phosphatidylserine(14:0/16:0),6b-hydroxyprogesterone,pyrrhoxanthinol,tatridin B,mandelonitrile rutinoside,taraxacoside(P<0.05),and up-regulated hypoglycin B,neuromedin N(1-4),dhurrin,5-deoxykievitone(P<0.01).The results of trial 2 indicated that dietary RSC increased the steer urine N_(2)OeN fluxes,the ratio of N_(2)OeN to N application and the estimated steer urine N_(2)OeN emissions(P<0.01).A close correlation was found between the estimated steer urine N_(2)OeN emissions and the output of urinary SCN(P<0.001).In conclusion,dietary RSC increased the fecal N excretion,whereas it did not affect the urinary N excretion and the N retention rate in steers.Dietary RSC increased rather than decreased the urine N_(2)OeN emissions even though it decreased the urinary excretion of urea.The SCN excreted in urine could be the major factor in increasing the urine N_(2)OeN emissions.Whether other metabolites excreted into urine from RSC have an impact on the urine N_(2)OeN emissions in steers needs to be investigated in the future.

Potentials of using dietary plant secondary metabolites to mitigate nitrous oxide emissions from excreta of cattle:Impacts,mechanisms and perspectives

Nitrous oxide(N_(2)O)is a potent greenhouse gas as well as the key component depleting the ozone sphere of the earth.Cattle have high feed and water intakes and excrete large amounts of urine and feces.N_(2)O can be produced from cattle excreta during storage and use as fertilizer.Mitigating the N_(2)O emissions from cattle excreta during production is important for protecting the environment and the sustainable development of the cattle industry.Feeding cattle with low-protein diets increases N utilization rates,decreases N excretion and consequently reduces N_(2)O emissions.However,this approach cannot be applied in the long term because of its negative impact on animal performance.Recent studies showed that dietary inclusion of some plant secondary metabolites such as tannins,anthocyanins,glucosinolates and aucubin could manipulate the N excretion and the urinary components and consequently regulate N_(2)O emissions from cattle excreta.This review summarized the recent developments in the effects of dietary tannins,anthocyanins and glucosinolates on the metabolism of cattle and the N_(2)O emissions from cattle excreta and concluded that dietary inclusion of tannins or anthocyanins could considerably reduce N_(2)O emissions from cattle excreta.

Decreasing ruminal methane production through enhancing the sulfate reduction pathway

Methane(CH4)production from ruminants accounts for 16%of the global greenhouse gas emissions and represents 2%to 12%of feed energy.Mitigating CH_(4) production from ruminants is of great importance for sustainable development of the ruminant industry.H_(2) is the primary substrate for CH_(4) production in the processes of ruminal methanogenesis.Sulfate reducing bacteria are able to compete with methanogens for H_(2) in the rumen,and consequently inhibit the methanogenesis.Enhancing the ruminal sulfate reducing pathway is an important approach to mitigate CH_(4) emissions in ruminants.The review summarized the effects of sulfate and elemental S on ruminal methanogenesis,and clarified the related mechanisms through the impacts of sulfate and elemental S on major ruminal sulfate reducing bacteria.Enhancing the activities of the major ruminal sulfate reducing bacteria including Desulfovibrio,Desulfohalobium and Sulfolobus through dietary sulfate addition,elemental S and dried distillers grains with solubles can effectively decrease the ruminal CH_(4) emissions.Suitable levels of dietary addition with different S sources for reducing the ruminal CH_(4) production,as well as maintaining the performance and health of ruminants,need to be investigated in the future.

Adding polyethylene glycol to steer ration containing sorghum tannins increases crude protein digestibility and shifts nitrogen excretion from feces to urine

The objectives of the experiment were to study the effects of adding polyethylene glycol(PEG)to steer ration containing high sorghum tannins on rumen fermentation,nutrient digestion,nitrogen(N)balance and plasma biochemical parameters.Eight growing steers at 16 months of age were allotted to a replicated 4×4 Latin square design with 4 treatments and 4 periods(19 d each).Polyethylene glycol at 0,1.75,3.50 and 7.00 g/kg dry matter(DM)were added to a basal ration containing 27.82%DM of sorghum grain(total tannins 3.3 g/kg DM)as the treatments.The results indicated that adding PEG quadratically increased the ruminal pH(P=0.049),tended to linearly increase the ruminal concentration of total volatile fatty acids(P=0.070),increased the molar proportion of acetate(P=0.016),linearly decreased the molar proportion of butyrate(P=0.015),and tended to increase the molar proportion of iso-valerate(P=0.061)and the ruminal concentration of ammonia N(P=0.092).Adding PEG tended to quadratically decrease the relative abundance of methanogenic archaea(P=0.082),linearly decreased the relative abundance of Fibrobacter succinogenes(P=0.008)and decreased the relative abundance of Butyrivibrio fibrisolvens(P=0.048)at 7.00 g/kg DM.Dietary addition with PEG increased the crude protein(CP)digestibility(P<0.001)and tended to increase the neutral detergent fiber digestibility(P=0.066)in a linear manner.Adding PEG to basal ration also increased the plasma globulin concentration(P=0.029)and tended to linearly increase the plasma total protein concentration(P=0.069).Adding PEG linearly decreased the fecal N excretion(P<0.001)and the fecal N-to-total N excretion ratio(P=0.004)and increased the urinary N-to-total N excretion ratio(P=0.004)and urinary urea excretion(P=0.010)without affecting the urinary N and total N excretions(P>0.05).It was concluded that adding PEG effectively improved the CP digestibility of the ration containing high sorghum tannins but increased the urinary urea excretion without improving the N retention and N retention rate in steers.