The rumen effects of changing diet throughout the season
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The Rumen & effects of changing diet throughout the season

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The Rumen & effects of changing diet throughout the season


RumanMicrobe The large microbe is a type of protist. The creature that looks like a tadpole attached to the side of the protist is a fungal spore. The smaller, rod-shaped beasts lining the underside of the protist are bacteria.

Let’s do a little Big Bang Physics

  • ∆ T core = + Rd +Cd+Cv–Ev+ Hp = 0

  • ∆ T core = Body core Temperature

  • Rd = Radiation (when 2 surfaces of different temperatures)

  • Cd = Conduction (opposite of insulation)

  • Cv = Convection (special case of conduction, fluid or wind over a surface)

  • Ev = Evaporation (heat loss only, cooling when water evaporates off)

  • ...............humidity can affect

  • Hp = Heat Production (A chemical process)

  • The cost to maintain 0-zero is the cost of production

Radiation (The flow of heat of 2 non touching objects)

Radiation (The flow of heat of 2 non touching objects)

Insulation (3 layers)

  • Itotal = T + Ex + A

  • I = Insulation

  • T = Tissue (skin, fat, blood flow/vasodilation & vasoconstriction)

  • Ex = External (Hair, Fleece, Feathers, Fur)

  • Highly variable….season, weather

  • A = Air (Air between hair, fleece, feather, fur)

  • Rough versus smooth makes a difference (Brahman vs Scotch Highland)

  • Rain can remove rapidly

Did you know?

  • That sweat dripping off your hat or elbows doesn’t help much

  • It is the evaporation ( of sweat that cools you down (convection)



PantingGood panters move a lot of air without much energy

  • Good Panters

  • Dog =Short rapid

  • Chicken = Flutter

  • Not so good panters

  • Cattle lose 3 times more heat by sweating than lungs

  • Sheep “ 1/8 “ “ “ “ “ “ “

How ruminants use energy

  • Viserca organs-

  • Liver, GI tract, Heart, Kidney comprise 6% of BW

  • But use 50% of energy

  • Muscle41% of BW but only 23% of energy









Cold stress

Heat Stress









Termoneutral Zone

Temoneutral Zone

Did you know?

  • How do young lambs and calve survive the cold?

  • 1. Shelter (out of the wind, south-east/southern exposure)

  • 2. They have brown fat (1-3 weeks) that makes more energy (heat) than shivering

  • does not apply to pigs and chickens

  • A hot ration is cool (due to Heat Increment….heat of fermentation)

Effective Temperature


Wind Speed-10 0102030

Calm-10 0102030

5-16 -6 31323

15-25-15 -5 414

30-46-36-26 -16-6

*Maintenance Requirements increase .7% for each degree

of cold stress.


Environmental Effects on Feed Intake

Dry, minimum


Cool night



Deep mud

Hot night

Cow (foregut / pregastric fermenter)

Digestion of Forage by Bacteria

Digestible Cellulose and Hemicellulose

T=0 hrs

Digestible Material is Gone

Fungal invasion

T=6 hrs

Undigested Material: Mostly Lignin and Cellulose

T=20 hrs

Source: Akin, et al. 1993

Effects of ambient temperature on digestibility in ruminants

  • Average decrease in digestibility per ˚C decrease is equal to .18% [NRC, 1981]

  • Occurs in both ruminant and nonruminant animal species

Slide from Gordon Carsten

What is going on here?

  • Intake increases as it gets colder

  • Thyroxine levels increase which increases motility and constricts rumen areas

  • Rate of passage and digestibility

  • Intake decreases at it get hotter

  • Thyroxine levels decrease and decreases gut motility & feed in gut more time

  • Rate of passage and digestibility

Stage of Forage Maturity vs. Stocker Gains




Mandan was where Lewis and Clark spent their first winter!

3-year Ohio Study (28 grazing cells)

Now lets look at the Forage and TemperatureWithin Season

The effect of temperature on the cell wall content (CWC) of grasses of the same maturity (adapted from Van Soest, 1981).

  • High ambient temperatures bring about rapid rate of maturity of forages

  • and a rise in cell wall content (CWC)

High ambient temperatures bring about rapid rate of maturity of forages and a rise in cell wall content (CWC) and a decrease digestibility of the cell wall (DCW)

Light Intensity

  • High light intensity increases the content of water-soluble carbohydrates

  • whereas, high temperature decreases water-soluble carbohydrates

  • When there is heavy cloud cover, such as occurs in the United States during

  • summer or in tropical areas during the rainy season, both temperature and light

  • contribute to high Cell Wall Content, which results in lower Digestibility and lowered

  • intake by grazing ruminants

Matching Animal Needs to Pasture Quality



Cool season grasses




1200 lb cow* nursing calf or


500 lb steer gaining 2.5 lb/d


Avg. lactating cow



Dry, pregnant cows




Late Veg.


E. bloom

Full bloom

Hard seed

* Superior milking cow

Matching Animal Needs to Pasture Quality

Crude Protein


Cool season grasses



1000 lb cow* nursing calf or

500 lb steer gaining 2.5 lb/d


Dry, pregnant cows




Late Veg.


E. bloom

Full bloom

Hard seed

* Superior milking cow

Lbs. Of CornADGGain IncreaseF/G

01.32--- ---

General comments of adding grain to forage-based diets

In rapidly growing forages, more than 20% of nitrogen in form of NPN

Under these circumstances, limited grain could increase nitrogen utilization

Above .25% BW, expect reduced efficiency

(ie. < 1.5 lb. grain on 600 lb. cattle)

Horn and McCollum (1987) have suggested that an energy supplement level that would

minimally affect forage intake would be 0.7% of animal body weight. However, level of grain supplementation can vary with forage quality

Otimum .2-.5% of body weight?

Grain supplementation to steers grazing fescueKentucky ResearchKentu

Digestible Fibers

Kentucky study:


Initial weight648629

Supp. Intake/Day 7 7

ADG 1.4 1.8

Studies with readily degradable fiber sources as energy supplements for grazing and

forage-fed ruminants have yielded different responses than research with grains.

Soybean hulls result in only a small decrease in forage intake.

Optimum Rate? 4 pounds?

Grain versus Digestible Fiber Supplementation

Since bacteria provide 55% to 80% of the animal’s protein, forages result in less microbial protein per lb. of dry matter consumed than grain diets.

  • Without supplementation, a cow can consume 18 pounds of dry matter from a low-quality forage source.

    18 Forage intake without supplementation

    x 1.25 Increase in forage intake with adequate protein

    22.5 Total forage intake with supplementation

    0.40 TDN content of the forage

    x 1.15 Increase in digestibility with adequate protein 0.46 TDN content of forage with supplementation

Protein Supplementation

  • Limited amounts (approximately 1-2 lbs) of high protein supplements (> 30% CP) can be utilized

  • with low-quality forages. Protein supplementation may increase digestibility and increase forage

  • intake.

  • Total pasture crude protein levels may become deficient for stocker cattle my mid-July. Stocker cattle may able to meet their crude protein requirement till mid-August if they are allowed to selectively graze high quality plants.

  • Therefore, cattle grazing late summer pasture may benefit from protein supplementation.

  • Supplement containing high levels of protein (>30%) can be fed at a rate of 0.8-1 lb per day or 2.5 lbs fed 3 times per week. If protein supplements contain nonprotein nitrogen, should be fed daily.

Metabolizable Protein




energy (TDN)


DIP (ammonia)


Frequency of feeding

  • When feeding protein supplement can feed 3 times a week with little effect on performance

  • Grains and digestible fibers – every day

Time of feeding

  • The time of day will effect affect the amount of forage that the cattle will consume

  • Cattle have intensive grazing peaks at dawn and dusk, with most grazing occurring in daylight hours

  • Feeding supplements in the middle of the day may be less disruptive on normal grazing activity and will cause cattle to eat more forage than if supplements are fed early in the morning

When ruminants get cold

  • Energy requirement goes up

  • Protein Requirements essentially say the same

3-year study NDSU, 2004-2006

Evaluating Manure

  • Great Forage - Between pancake batter and pumpkin pie filling

  • Low Quality Forage -  Wedding cake (dry and stacked in layers)

Water System Requirements


Questions ???

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