- grazing immature cool-season grasses in early spring (high in K+ and low in Mg2+ and Na+) - absorption of Mg in the rumen relies on exchange of K/Na (Mg cannot be released from bones like Ca

Beef 3 - Nicole Flashcards by Tesse Lind

name some nutritional disorders of beef cattle

frothy bloat
hypomagnesemia (grass tetany)
Nutritional Muscular Dystrophy
Nitrate Poisoning

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what causes frothy bloat?

formation of stable foam in the ruman preventing eructation - caused by a diet of highly soluble protein in legumes

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is frothy bloat an emergency

yes!

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how to prevent frothy bloat

provide bloat-safe forages (less saponins), interseed forage with grass, put surfactant oils in drinking water (2g/100kg BW)

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hypomagnesemia cause

grazing immature cool-season grasses in early spring (high in K+ and low in Mg2+ and Na+)
absorption of Mg in the rumen relies on exchange of K/Na (Mg cannot be released from bones like Ca

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the pump that absorbs Mg is only activated if

there’s a hypokalemia - which in grass tetany is not the case, so no Mg is absorbed

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grass tetany affects younger/mature animals more frequntly

mature animals - lactating cows

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legumes contain more/less Mg than grasses

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is grass tetany an emergency disease

yes - mg is essential in enzyme activation and a regulator of synaptic transmission in muscles

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clincal signs of hypomagnesemia

hyperexcitability, convulsion, recumbency with very stiff extremeties

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hypomegnesemia prevention

dietary Mg supplementation in early spring - molasses magnesium free choice licks (min 5% Mg)
- interseed with legumes
- delay spring grazing (unfeasible in some situations)
- proper soil fertility management (Mg limestone in areas of low/medium Mg)

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Nitrate poisoning - cause

increased nitrate in stressed crops (plant normally converts nitrate NO3- to nitrite NO2- to nitrogen) but if stressed, the plant does not convert NO3- to NO2-

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examples of things that could stress plants out

late frost, drought, hail, extended cloudy period,

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is nitrate poisoning an emergency disease / why?

yes! the rumen converts NO3 to NO2 to NH4+ (ammonium)
excess Nitrate - NO3 to NO2 faster than NO2 to NH4+

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clinical signs of nitrate poisoning

acute tissue hypoxia and hypotension
rapid, weak heartbeat
low body temperature
muscular tremors, weakness, ataxia
cyanotic mucous membranes
dyspnea, tachpnea
brown blood

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prevention - nitrate poisoning

graduation adaptation to stressed crops
silage of stressed crops reduces nitrate content (hay can be more dangerous)

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nutritional muscular dystrophy - other name

white muscle disease

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white muscle disease is caused by

selenium/Vit E deficiency

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Nutritional muscular dystrophy affects rapidly growing calves born from dams that are

in Sel/Vit E deficient areas
- high levels of dietary sulphur and iron can decrease Se absorption

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Sel/Vit E are

antioxidants - at low levels, no sufficient protection against physiological lipoperoxidation leading to hyaline degeneration (connective tissue) and calcification of muscle fibres

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selenium reqt for growing cattle

0.1 mg/kg DM (limit 5 mg/kg)

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vit E requirement for growing cattle

25-35 mg IU/kg DM

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prevention of white muscle disease

dietary or injectable supplementation to pregnant cows (mid gestation to 1st month of lactation)

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nutritional muscular dystrophy clinical signs

stiffness, weakness, recumbency, dysphagia

pathological findings: pale discolouration of affected muscle

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goal for finishing phase -

efficient growth and weight gain

Diet of finishing phase

grain based - by end, 90% concentrate -TMR -least cost diets that support maximum growth rate without detrimental effects

weanling calves & yearling weights

450-600 lbs, 900 lbs

beef target weight

1400 lbs (635 kg)

goal for ADG

HIGH! 1.6 to 2.0 kg/day

time of weaned calves & yearlings at the finishing phase

Calves: 180-280 days Yearlings: 100-180 days

goal for carcass composition

28-29% body fat BCS 8 AAA- high quality grade with marbling

examples of feedstuffs used for energy

barley, corn, beet pulp, citrus pulp

examples of feedstuffs for protein

canola/soybean meal, cottonseed hulls, distillers grain (cotton + distillers cheaper)

examples of feedstuffs for fibre

barley/corn silage barley/alfalfa haylage hay

examples of additives

ionophores, buffers, growth promoting compounds

growth promoting compounds - synthetic hormones

MGA - melgenestrol acetate (oral progesterone to suppress estrus in heifers) TBA - trenbolone acetate (implants)

growth promoting compounds - antimicrobials

ionophores - selecting rumen microbiota

growth promoting compounds - B adrenergic agonists

ractopamine/zilpaterol - feed efficiency promoter

grain processing - why

for digestibility - want rumen microbes to have access to the interior of the kernel

dry rolling - grain processing

crush kernels through alternating rollers, which can generate fine particles (bad)

temper rolling - grain processing

kernels are soaked in water for up to 24h before rolling - increased moisture content to soften the endosperm (hull) -more consistent particle size

3 stages of feedlot life

receiving - step up phase - finishing

receiving diet - what is it

starting cattle on feed and teaching them to eat from a bunk - takes 2-3 weeks - make water easy to find and consume - place unwrapped haylage close to water

receiving diet - 1st days give _________ then transition to ___________

hay, then introduce a grower diet with hay on top during 1st week (silage/haylage, grains, supplements)

step up diet

sequentially increase concentrate to a final ratio (10:90) of concentrate:fiber

step up diets include a step down in

silage/haylage protein levels decrease and energy levels increase

if we don't adapt the rumen correctly to concentrates what happens

grain overload disorders - ruminal acidosis & rumenitis, liver abscesses, and bloat

feedlot cattle fed high-grain diets luminal pH

6.2-6.5

what is a cow with ruminal acidosis rumen's pH?

5.2-5.6

should rumen pH have a cyclical pattern on high concentrate diets

yes - highest at feeding & declines to the lowest point 5-10h later

does a cow experiencing acidosis during the 1st day of grain adaptation experience a cyclical rumen pH

no - pH drops rapidly on day 1 and might not increase the next morning, with a very low feed intake the next day

ruminal acidosis - decreased ruminal motility and rumination leads to

increased VFA --> chemical receptors in rumen epithelium sense it --> water influx from bloodstream across the rumen wall because of increased osmolarity of ruminal content --> VFAs stimulate the growth of ruminal epithelium --> parakeratosis --> rumenitis --> translocation of bacteria

liver abscesses are secondary to

rumenitis (rumenitis-liver abscess complex)

do liver abscesses cause clinical signs

no - but they cause decreased intake, ADG, feed efficiency, and carcass dressing percentage

can you score liver abscesses

yes, from 0 (no abscesses), A- : 1-2 small abscesses, A: 1-2 large abscesses or several small ones, A+: multiple large abscesses with adhesions

liver abscesses are often poly microbial: name some

fusobacterium necrophorum, trueperella pyogenes

F. necrophorum is an inhabitant of rumen - it ____________ in number in high grain diets

increases, because it uses lactate and colonizes the rumen wall

F. necrophorum enters the bloodstream by

crossing damaged ruminal epithelial barrier

how to control liver abscesses

in feed antimicrobials to suppress the growth of F. necrophorum in the rumen, which decreases prevalence but does not eliminate it - requires prescription and cannot be used for growth promotion

antimicrobials used to control liver abscesses

macrolides - category II antimicrobial Tylosin is MOST common

dose of tylosin in feed

11 mg/kg in the complete diet (DM basis) - 60-90 mg/animal/day - no withdrawal time

do vaccines work to control liver abscesses

do probiotics and essential oils work to control liver abscesses

feedlot bloat is an excessive production of

bacterial mucopolysaccharides

prevention of feedlot bloat

diet adaptation - gradual changes & check grain processing bulk management (right particle size) additives - ionophores, buffers

feed bunk management - the most important daily task in a feedlot. Goal:

keep animals eating a consistent amount of feed to avoid fluctuations in rumen pH and minimize digestive disorders

feedlot vet should check if:

animals are fed on time (same time every day) feed is properly mixed feed intake is intermittent Ask: how much is offered, and how much is left over?

feeding options:

1. ad libitum (free choice) 3-5% leftover 2. slick bunk - small amount of feed remains, feed intake is regulated but not reduced, which reduces sorting, avoiding feed wastage