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Not only has gentics and nutrition played a major role in maximizing milk production, but farm management, labor, and facilities all play a role as well. Jaylor's Ruminant Nutritionist, Janet Kleinschmidt, discusses how.
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The Rumen & the (TMR)
Wagon Part I
The Rumen & the (TMR) Wagon
“Feeding Strategies that optimize rumen function also maximize milk
production and milk component percentages and yield.”
Due to the genetic superiority of our modern-day dairy cow, it has been a race to see how much feed we can get into these
animals to allow their genetic make-up to do what it is supposed to do to transform
nutrients into milk and components.
The Rumen & the (TMR) Wagon
Not only has genetics and nutrition played a major role in maximizing milk production,
but farm management practices, labor, and facilities play a role as well.
About The Rumen
The rumen accounts for approximately 25% of the total body weight, we are managing a
very large fermentation system that has its own ecosystem, efficiencies and
processes. The rumen can hold approximately 200 litres of
material and fluid.An estimated 150 billion microorganisms per
teaspoon (bacteria, protozoa, fungi)
are present in its contents.
About The Rumen
This type of environment is maintained at a temperature range of 38 to 42’ C.
The rumen through its strong musculature allows mixing and churning of digesta,
typically 1-2 ruminations/minute.
The movement of the rumen mixes the contents, promoting turnover and
accessibility of the coarser forage particles for regurgitation, cud chewing, size reduction, and microbial digestion.
About The Rumen
Fine forage particles, dense concentrate particles, and materials which have become
hydrated tend to congregate near the bottom.
Particles tend to move out from the rumen as they are reduced in size through cud
chewing and microbial action.
The microbes also pass from the rumen for possible digestion in the lower
gastrointestinal tract.
About The Rumen
Long-hay diets produce
contents with a large, less dense, floating
layer beneath the gas dome with relatively
liquid contents and suspended
fiber beneath.
The floating
mat is composed of the more recently
ingested forage.
About The Rumen
The function of the rumen as a fermentation vat and the presence of certain bacteria
promote the development of gases.
These gases are found inthe upper part of the rumen with carbon
dioxide and methane making up thelargest portion.
The proportion of these gases is dependent rumen ecology and fermentation balance.
About The Rumen
Table 1. Typical composition of rumen gases.
COMPONENT AVERAGE %
Hydrogen 0.2
Oxygen 0.5
Nitrogen 7.0
Methane 26.8
Carbon dioxide 65.5Source: Sniffen, C. J. and H. H. Herdt. TheVeterinary Clinics of North America: Food AnimalPractice, Vol 7, No 2. Philadelphia, Pa.
About The Rumen
The objective of feeding dairy cattle
nutritionally balanced diets is to provide
a rumen environment that maximizes
microbial production and growth.
When designing rations for ruminants, the
needs of both the animal and the rumen
microorganisms must be considered.
About The Rumen
The microbial population in therumen consists of bacteria, protozoa, andfungi. The majority of the concentration
is as bacteria.
The methane-producing bacteria area special class of microorganisms
responsible for regulating the overallfermentation in the rumen.
About The Rumen
The protozoa are generally found in the rumen when
diets of high digestibility are fed.
Protozoa actively ingest bacteriaas a source of protein; they also appearto be a stabilizing factor for fermentation
end products and contribute to fiber digestion.
Although their benefit to ruminant animals is still not well defined.
About The Rumen
The anaerobic fungi are the mostrecently recognized group of rumen
microbes.
When animals are fed a highforage diet, rumen fungi may contributeup to 8 percent of the microbial mass.
While it is still unclear whether thesefungi are functionally significant they do
appear to have a role in fibre digestion.
About The Rumen
The rumen provides a site where the
rumen microorganisms can digest
carbohydrates, proteins, and fiber.
Through this digestion process, energy or
volatile fatty acids (VFA’s) and microbial
protein that can be utilized by the animal
are produced (Figure 1).
About The RumenFigure 1. Feed, nutrient flow from the rumen, and milk
components.Feed Crude Sugar, Fermentable Fat
Protein starch fiber
UIP DIP Microbial growth and fermentation
Microbial protein
Nutrients Amino Propionic Acetic, Fattyacids (glucose) butyric acids
Milk
Components
Milk Protein Milk Lactose Milk Fat
Rumen pH
The whole rumen function/maximum feed intake/milk yield and components issue
comes down to a two-letter word…
pHThere is a “comfort zone” in which everything
runs healthy and most efficiently. Above or below this comfort zone, inefficiencies
begin to occur.
Rumen pH
Fiber digesting bacteria growth is favored when rumen pH is between 6. 0 and 6.8
while starch digesting bacteria growth is favored by a pH from 5.5 to 6.0.
The high producing cow must maintain a pH near 6.0 for optimal growth of both bacteria
populations, resulting in a favorable VFA pattern and yield.
Several factors impact changes in rumen pH :
1. The type of diet can shift pH, with high forage rations favoring a pH over 6.
Forages stimulate higher rates of saliva secretion and saliva contains bicarbonate
which buffers the rumen and increases acetate production.
Forage carbohydrates (primarily cellulose and hemicellulose) are not degraded as rapidly
by the rumen microbes as are carbohydrates in concentrates (primarily
starch and sugar).
Several factors impact changes in rumen pH :
2. Physical form of feeds (ground, pelleted or chopped) will change the size of the feed particle.
If forage particle size is too short, a forage mat in the rumen cannot be maintained, fiber digestion is decreased and rumen pH is
lowered. Saliva production is also reduced due to less cud chewing time.
Cows will typically spend over 500 minutes of chewing time per day; 50 % of the cows should be chewing their cuds when resting.
Several factors impact changes in rumen pH :
3. If concentrates are ground too fine, starch is exposed to microbial digestion and there is increased degradation: rumen pH drops and propionic acid production increases resulting in a drop in BF% and a rise in MP%.
Steam rolling, pelleting or grinding will change starch structure which can be beneficial (increases rumen microbial growth) or negative (increases the risk of rumen acidosis).
Several factors impact changes in rumen pH :
4. Wet rations can reduce rumen pH due to less saliva production to wet the feed for swallowing. If the wet feed is silage, less chewing is needed to reduce particle size, lowering rumination time. Silage can have a pH below 4, increasing acid load.
5. Adding unsaturated fats and oils (e.g. vegetable) can reduce rumen pH and shift VFA patterns. Oils can reduce fiber digestibility, decrease rumen pH, be toxic to fiber digesting bacteria and/or coat fiber particles, reducing fiber digestion.
Several factors impact changes in rumen pH :
6. The method of feeding will change the rumen environment.
TMR’s stabilize rumen pH, synchronize degradable protein and fermentable
carbohydrate availability, increase dry matter intake and minimize feed selection.
If concentrates are fed separately, limit the amount to 2-3 kg DM per meal, avoid high
levels of starch-containing grains and evaluate the effect of feed processing.
Rumen pH Effects
To summarize this point, the focus of rumen pH as a monitor of healthy rumen function is as important as balancing diets simply for maximum dry matter intake or maximum
milk yield. It is suggested, especially during an era of
particularly high grain prices, that we allow the genetic superiority of our modern-day
dairy cows to drive maximum milk production while the nutritionists and dairy producer focus on maximum rumen health
and rumen efficiency.
Dry Matter Intake & Rumen Function
The main objective in feeding management is to increase the dry matter intake (DMI) of the cows; with this increase should come
higher levels of milk production, milk components and herd fertility.
In order for this to happen, close attention to energy, ration digestibility, rumen fill,
palatability, temperature, body weight of the animal, feeding conditions, environment,
ventilation, frequency of feeding, and water intake and quality are necessary.
Dry Matter Intake & Rumen Function
Achieving optimum DMI through nutrition and feeding management involves:
1. Producing the highest quality forages possible2. Dry and transition cow nutrition and management3. Monitoring body condition (BCS)4. Bunk management to maximize dry matter intake5. Proper protein, energy, vitamin and mineral
nutrition6. Ensuring herd hoof health (Cows who cannot walk do not
eat, are more prone to reproductive and metabolic disorders and are likely to be prematurely culled from the herd).
