ANSC 318 1st Edition Lecture 15 Outline of Last Lecture I. Hay Losses, Strategies to Reduce Field and Storage Losses, and Silages. Outline of Current Lecture II. Grass Tetanya. Condition and Clinical Signsb. Causesc. Magnesium Availabilityd. Animals at Riske. Preventative Managementf. TreatmentIII. Pulmonary Emphysemiaa. Conditionsb. Causec. Treatment/PreventionIV. Dallisgrass Poisoning or Bermuda Tremorsa. Conditionb. Causesc. Treatmentd. PreventionV. Nitrate Toxicitya. General Backgroundb. Clinical Signsc. Physiology of Nitrate Toxicityd. Treatmente. PreventionVI. Prussic Acid Poisoninga. Conditionb. Causec. Clinical Signsd. Preventione. Treatmentf. General RuleVII. Kleingrass ToxicityVIII.IX. Fescue ToxicityThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Clinical Signsb. PreventionCurrent Lecture Grass Tetany•happens winter wheat low in Magnesium (Mg) ***•aka: wheat pasture poisoning and hypomagnesemiaConditions/Clinical Signs:-animal staggers, twitches, falls down and is unable to get up-low muscle Mg level cause loss of muscle control-animals die from muscle convulsions – cow can die within hours of observed clinicalsigns if now treated right away ***Clinical Signs:-uneasiness, nervousness, muscle twitching, excitable – belligerent, in-coordination,alert but recumbent cow, increased rectal temperature, convulsions, severe casesmay die, but mild will surviveCauses:-lack of Mg being absorbed from forage, hence, a Mg deficiency-low blood Mg levels will cause Mg to be pulled from muscle tissues because bone Mg isa not readily available source for the animal to use ***-to prevent Mg deficiencies, dietary supplementation of Mg is needed **Magnesium Availability:•Mg may not be fully available from forages•Factors that inhibit Mg absorption:-low Ca and Mg levels in forages-high K levels-high protein levels-high levels of other organic compounds-grazing fall and winter grain pastures which are undergoing periods of rapid growth willmost likely lead to increased cases of grass tetanyAnimals at Risk:•Cattle are most prone to grass tetany1. Pregnant cows (last trimester)2. lactating beef cows (first 2 months of lactation)3. older cows are more susceptible than younger beef cowsPreventative Management:1. acid/sandy soil (East TX)  apply limestone to the soil2. do not apply limestone to high alkaline soils ***3. graze older dry cows or stocker calves if pastures tend to cause grass tetany•feed Mg Oxide (2 oz/cow/day)-Mg Oxide is not palatable and is expensive-not recommended in liquid form, tastes terrible and cattle will not eat it-mixing Mg into range cubes is recommended-high Mg mineral blocks aren’t guaranteed to prevent grass tetany since cows may notconsume enough of the supplementTreatment:-if diagnosed soon, inject Ca-P-Mg-gluconate solution into jugular veinPulmonary Emphysemia:•aka: Fog Fever or Lungers•found in BermudagrassConditions:-severe lung involvement from sensitivity/allergic reaction-lungs fill with air, not fluid ***-lungs expend, but don’t contract, causes gasping, contracted rapture can occur-older cows = more susceptible; brahman cows = less susceptible-cows die from lack of oxygen or quickly getting excitedCauses:•Rumen microbes convert tryptophan to 3-methylindole-cows (calves are immune) get it from grazing immature lush pastures up to 5-14 days ofage or regrowth after cutting-takes time for reaction to set up – usually 1-2 weeks after cattle are put on pasture-can be caused by other grassesTreatment/Prevention:1. slowly remove cattle from pasture: too fast and they will get excited and will not beable to breath2. let pasture mature for 2 weeks before grazing3. inject atropine and antihistamine to improve lung function: antibiotics will helpsecondary infection – remove from pasture before treating4. rumensin (200 mg/hd/day) may help to prevent pulmonary emphysemia-not common in horsesDallisgrass Poisoning or Bermuda Tremors•happens when dallisgrass is infected with ergot or from bermudagrassCondition:-cattle get hyper-excited when scared/spooked; appear normal but stumble/fall whenchased-usually do not dieCauses:-Dallisgrass Poisoning: caused by ergot on the seed head of mature Dallisgrass; seed hasbeen replaced by fungus-Bermudagrass Tremors: caused by fungus associated with tremorgenic mycotoxin;cattle typically develop tremors while grazing tall bermudagrass pastures-keep bermudagrass shortTreatment:-supportive care with feed and water-slowly remove cattle from bermudagrass pasture-will recover when they get off the pasture-antibiotics may help recoverPrevention:-shred mature dallisgrass to get seed heads off (8” high)-keep Bermudagrass grazed down, never let it get high-bermudagrass  if severe, burn the field ***-do not use bermudagrass for hay in case of toxicity-bermudagrass can’t be shredded since it is not only in the seed headNitrate ToxicityGeneral Background:•nitrate (NO3-) concentrations are often elevated in forage; seldom in concentrates•factors causing nitrate elevations:-drought, frost damage, shading, herbicide treatment, high nitrate in the soil, fertilizing•can be found in any sorghum•nitrates metabolized in the GIT by anaerobic microbes and are reduced to ammoniaNO3  NO2  (N2O5, NO2, NO)  NH2OH  NH3Nitrate  nitrite  nitrogen oxides  hydrozylamine  ammonia •nitrite oxidizes hemoglobin (Fe++) to methemoglobin (Fe+++) which can’t carry O2•fetus is susceptible to methemoglobin leading to death/abortion•doesn’t affect horses or pigsClinical Signs:•.5-4 hours post ingestion-colic pain, diarrhea, dyspnea, muscular tremors, staggering gait, cyanosis (not movingO2), abortion, head back death without struggle, blood = chocolate brownPhysiology:•plant nitrate  nitrite in rumen•some nitrite can be converted to ammonia which is used to synthesize microbial protein•nitrite much more toxic to animal than nitrate•forages with elevated nitrate levels will not affect horses/pigs because they lack microbial fermentationTreatment:-Methylene blu 8.8 mg/kg IV **-administer EXTREMELY SLOWLY **Prevention:•have nitrate levels analyzed•0.0 – 1% NO3 is safe to feed•1 – 1.5% NO3 can be fed if limited to ½ total DMI/day-feed 1 lb/head/day of feed for every .1% you are over 1%•>1.5% NO3 is not safePrevention:-type and quantity of diet fed