Lecture 22: Beef Nutrition 2

environmentla effects on nutrient needs for beef cattle:

effective temp:

• based on air temp, moistore, and air speed

• can affect energy needs of cattle

key point: cold stress increases energy requirements beyond maintenance

wind chill and beef cattle

lower critical temperature (LCT)

depends on hair coat, moisture, eind

energy increases 1% per degree below LCT (dry)

energy increases 2% per degree below LCT (wet)

key point: cold, wet conditions dramatically increase energy needs in beef cattle - want cows to be at BCS of 5-6 going into winter

estimated lower critical temps for beef cattle

environmental adjustments (NRC)

NRC factors to account for: BCS

amount of body fat = insulation

heat production from feed

• forages = more heat production

• grains = more energy production —> increases heat production on poor quality forage diets

key point: diet type influences ability to cope with cold stress

body condition scoring for beef cattle

beef cows 1-9 scale

focus on palpation and visual fat deposition pints

target BCS —> 5-7 at breeding and calving

red angus BCS 6

BCS and cow performance

BCS reflects fat reserves

BCS affects:

• time to first estrus —> shorter interval to first heat with a higher BCS

• colostrum quality —> higher with higher cow BCS

• calf immunity —> higher IgG levels for calves born to cows with higher BCS

key point: BCS is better indicator than BW in ruminants (chnges in gut fill)

BCS charts in beef cattle

what is the ideal BCS for beef cow at calving?

5-7

low or high BCS =

decreased preg rate

• BCS should be between 5 and 7

heifers target BCS:

6

after calving, ideal to group cows based on:

BCS

• can feed according tp how much condition is needed

  

feeding heifers, weaned calves, stocker calves, and finishing cattle

how do we manage nutrition across production stages?

heifer development

target 65% BW at breeding (mature)

target 85% BW at calving (mature)

puberty target: 14-15 months

BW is most important factor affecting puberty

heifer example

mature size = 1100 lbs

target: 715 lbs at breeding (1100 x .65)

target: 935 lbs at calving (1100 x .85)

heifer nutrition basics:

key points:

avoid overfeeding energy

around 11% CP

NEg based on ADG target

preconditioning of weaned calves

process to reduce stress and improve health before feedlot entry

strategy to reduce health issues in the feedlot, improve growth post weaning, and enhance overall profit

preconditioning components

health and welfar:

• castration

• dehorning

• deworming

vaccination

• two sets od respiratory (MLV) and clostridial vaccines

bunk training

• feed and using water troughs

30-45 days low-stress weaning prior to shipping (use fence line weaning)

value-added calf

preconditoined

individual ID

source/age verified

proper injection practices

• should be front of shoulder to decrease muscle site blemishes

typical return = >$30/calf

energy needs for stockers

when is supplementation needed

• ADG>0.5 lbs/d

• with low quality hay

• winter or late summer

grain supplementation ranges

• 1-2.5 lbs/d/animal

energy needs for stockers

stocker = mostly pasture, occasional supplementation

backgrounding —> dry lot —> hay and grain mix

what should the level of CP be in the overall diet of growing stocker cattle?

12-16 percent

protein needs for stockers

forage CP

• >8% to maintain rumen microbes

• <8% likely results in CP deficiency

diet target = 12-16% CP

• supports adequate growth

UIP often needed - ensure that some essential AA reach animal

supplementing urea

• do not use with high forage diets (forage digested too slwoly relative to energy content for urea to be utilized)

• can use with high energy diets

key point: protein often limits growth on low-quality forage

CP for stockers

feedlot diet overview:

enter around 700-800 lbs BW

high grain diet risks

• risk of acidosis

• laminitis

• liver abscesses

nutrient composition

CP = 9-14%

(first diet could be higher CP —> then step down CP in final diet)

mineral needs

• supplement Ca (grain low in Ca)

transition to feedlot diet

goal: adapt rumen micorbes

• adapt to new substrate: forage (cellulose, hemicellulose) —> grain (starch)

• needs to occur over 3-4 weels

maintain intake!!

prevent acidosis

• slow diet adjustments

diet adaptation strategy

start: 60% forage/40% concentrate

end: 90% concentrate

key point: gradual transition prevents rumen upset

feedbunk management

consistency is key

• feed is fresh and delivered on time

monitor intake

feed ad libitum, but minimize waste

• want a little feed left to ensure that cattle are eating all they can!

nutritional diseases list

mineral issues:

grass tetany —> Mg deficiency

K increases in forages and can interfere with Mg absorption, Mg low in spring

urinary calculi —> grain high in P (upset Ca:P ratio)

nitrate toxicity

nitrate —> nitrite in rumen —> absorbed and forms methemoglobin (inhibits O2 transport)

pasture fertilization —> plants accumulate nitrates

weeds

mycotoxin toxicity

corn feeds, corn silage

• calves most sensitive, decreased DMI and growth

sulfur toxicity

sulfer-associated polioencepholomalacia

rumen disorders:

acidosis (usually acute) lactic acid accumulation

bloat —> frothy or free gas

sulfur toxicity

sources: disteller’s grains

risk: high variability in sulfur content

disease: sulfer-associated polioenchalomalacia

requirement vs toxic levels in sulfer-associated polioencephalomalacia

required: 0.18-0.24%

considered toxic: 0.4-0.5%

mechanism of sulfer-associated polioencephalomalacia

high dietary sulfur —> increases metabolic demand for thiamine —> results in secondary thiamine deficiency

time course for sulfer-associated polioencephalomalacia

1-4 weeks

growth promotants

hormonal implants

• estrogenic —> estradiol, progesterone, zerenol

• androgenic —> testosterone, trenbolone acetate

• use at any stage of growth or finishing

• increase ADG by 15-20%

MGA (melengesterol acetate)

• progesterone analog

• suppresses estrus in heifers (decrease DMI)

beta-agonists

• Optaflexx/ractopamine repartitioning agent (more muscle deposition)

coccidiostats

• young cattle/feedlot cattle to control naturally occuring coccidiosis

• improve aDG and feed efficiency

ionophotes

shift rumen fermentation

type of abx not used in humans

• modify rumen microbes

• decrease acetate and methane, increase proprionate

direct metabolism towards deposition of muscle instead of fat

benefits of ionophores

increase feed efficiency

decrease acidosis

summary of beef nutrition 2

• environment and BCS strongly influence requirements

• nutrition varies by production stage

• feedlot transitions must be gradual

• many diseases are nutritoin-related and preventable