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Washington State University Dairy News

June 2015 WSU Dairy Newsletter

Cool Temperatures and Large Particle Solids Affect Ammonia Emissions from Land Applied Dairy Manure

We have been studying the factors affecting the emission of ammonia from dairy manure for the past eight years. The major factors that affect ammonia emission at the time of application appear to be: the ambient temperature, manure treatment (anaerobic digestion of manure), large particle solids, and incorporation.

During the summers of 2010, 2011 and 2012 we conducted twenty-two manure application studies looking at the effect that various types of dairy manure had on ammonia emissions when applied to grass which was to be harvested as silage. In particular, we wanted to understand the impact that anaerobic digestion and large particle manure solids had on ammonia emissions. Figure 1 shows the typical pattern of ammonia concentration throughout the day of manure application.

Graph showing NH3 emissions by time of day following application.
Figure 1. Typical NH3 measurement on day of manure application.

Due to the cooler climate of the Pacific Northwest, it is common to apply manure at ambient temperatures below 60 degrees Fahrenheit. We found the that 60 degrees Fahrenheit was a critical temperature as we were not able to observe ammonia emissions on the day of manure application when it was cooler than 60 degrees.

We know from studies with anaerobic digestion (AD) of dairy manure that the amount of ammoniacal nitrogen can be greater in AD manure. This is due to the conversion of organic-nitrogen to ammonia-nitrogen by microbes in the anaerobic digester. This observation led us to assume that AD manure would lose more ammonia when land applied, when compared to non-AD (or raw manure). What we found in 2010 was that since AD manure had the large particle solids removed prior to storage, the AD manure actually had less ammonia emitted after land application than non-AD manure with large particle solids (see Figure 2). The reduced NH3 losses from liquid manure without large particle solids was due to the promotion of manure infiltration into the soil, consequently reducing the manure exposure time on the ground surface.

In 2011, we added an additional manure type, non-AD with large particle solids removed. When this manure type was compared to AD manure, and non-AD manure with solids, it was clear the effect that manure solids have on increasing ammonia emissions. Our data suggest that the ammonia emission were reduced by ~40% (see figure 2) when large particle solids had been removed.

Bar graph showing ~40% increase in ammonia emissions when large particle solids are not removed from manure.
Figure 2. Average ammonia concentrations for manure treatments, ADWOS = anaerobically digested manure without large particle solids, NADWOS = non-AD manure without large particle solids, and NADWS = non-AD manure with large particle solids.

Complete data published in Sun, F., J. H. Harrison, P. Ndegwa, and K. Johnson. 2014. Effect of manure treatment on ammonia and greenhouse gas emissions following surface application. Water, Air, and Soil Pollution. DOI 10.1007/s11270-014-1923-z

Joe Harrison, Livestock Nutrient Management Specialist, WSU Puyallup,

Amber’s Top Ten Tips: Understanding Heat Stress

Heat stress is bad news for dairy cows. We often hear about abnormal heat waves that roll through regions leaving behind millions of dollars of damage, but what about the losses incurred during a typical summer? Across the U.S., the economic losses attributed to heat stress are approximately $100 per cow per year. With summer knocking at our door, have you considered how hot weather impacts the cows on your dairy?

Interesting facts about heat stress in dairy cows:

  1. Temperature-humidity Index (THI)

    THI is commonly used to gauge the severity of heat stress dairy cows experience under specific environmental conditions (ambient temperature and relative humidity). THI ≥ 72 is categorized as heat stress; however, recent research has indicated that the heat stress threshold should be lowered to a THI of 68.

    THI = ambient temperature – [0.55 – (0.55 * relative humidity/100)] * (ambient temperature – 58.8)

    Ambient temperature is recorded in Fahrenheit and relative humidity is recorded as a percentage.

  2. Core Body Temperature

    As THI increases and, subsequently, core body temperatures increase, cows spend more time standing rather than lying down. Cows with rectal body temperatures ≥ 102.2°F (measured in the afternoon) are at risk for decreases in milk production and fertility.

  3. Water Intake

    Cows will consume 35 – 50% more water during heat stress conditions. Ensure cows have access to an adequate supply of clean, fresh water.

  4. Feed Intake

    Heat stress causes decreases in feed intake during the daytime, decreases in feed efficiency, and decreases in nutrient absorption. Nighttime “slug feeding” may lead to higher incidences of acidosis.

  5. Milk Composition

    Cow exposure to environmental heat stress has been linked to higher milk somatic cell counts and bacterial counts, with lower milk fat and protein percentages.

  6. Cooling Strategies

    Natural ventilation, fans, sprinklers/misters, shade access (esp. open lot dairies), and cooling pads all offer heat stress abatement for dairy cows; however, each dairy needs to assess which strategy will work best for each facility. Adjustments to feeding schedules, ration formulations, and stocking densities may also assist with heat stress abatement.

  7. Milk Production

    Depending on the severity of heat stress conditions, cows will decrease their milk production by 10 – 50%.

  8. Reproduction

    Conception rates during heat stress can plummet by almost 20%. For example, a dairy with a typical conception rate of 31% fell to a conception rate of only 12% during hot weather.

  9. Health

    Higher incidences of mastitis, respiratory problems, retained placentas, and higher respiration rates have been diagnosed in cows under heat stress conditions.

  10. Gestation

    Calves exposed to heat stress during the last 45 days of gestation have lower birth weights, lower weaning weights, and depressed immune systems.

Table showing onset of heat stress symptoms at various combinations of temperature and humidity.
Source: Zimbleman and Collier.

V.S. is No B.S.!

On May 29, Dr. Keith Roehr presented a webinar about the 2014 Vesicular Stomatitis (VS) outbreak in Colorado. Dr. Roehr is the Colorado State Veterinarian. He reported that between July 4, 2014 and Jan. 29, 2015, his office made 556 investigations and ultimately quarantined 370 premises that tested positive for VS. The late onset of Colorado’s winter in 2014-15 was blamed for such an extended outbreak duration.

What is VS?

VS is a contagious viral disease of all hoofed animals—particularly equines, swine and cattle; sheep, goats and camelids are affected less often. The virus occasionally spreads to humans and causes a flu-like disease and blisters in rare instances. It is believed to enter a herd via insect vectors (black flies, midges, sand flies, etc.) and then spread primarily through additional insect activity within the herd. Little transmission is believed due to direct livestock contact, animal movement, and mechanical means, such as contaminated equipment and facilities.

Signs of Illness

Cow showing erosions and sloughing of tissue on the lips and tongue.
Photo by Dr. Jeanne Rankin (from
Affected animals have erosions and sloughing of tissue on the lips, tongue (see photo), teats, prepuce, between the toes, and on hoof coronary bands. Blisters and vesicles occur on these areas early in the course of disease but are often missed by human caretakers. Other signs include fever, poor appetite, lethargy, weight loss, drooling, scabbed lesions, and lameness if feet are involved.

Why is VS Important?

VS is present in the U.S. and occasional disease outbreaks occur. Also, although VS is very contagious and can cause many cases of illness on premises, animals rarely die from it. Nevertheless, the disease is particularly important for several reasons:

  • The signs of VS are similar to three foreign animal diseases not present in the U.S.: foot and mouth disease, swine vesicular disease, and vesicular exanthema of swine. It is essential to differentiate VS from these other diseases quickly so the entry of one of these exotic diseases can be identified and dealt with promptly.
  • VS is infectious—outbreaks in the U.S. restrict some international trade until the outbreak is contained.
  • Its similarity to important foreign animal diseases make VS a reportable disease in the U.S.
  • Animals afflicted with VS are in pain, stop eating, lose weight and produce less milk. A widespread outbreak could cause significant animal suffering and economic losses. Dr. Roehr shared that economic losses of dairy farms involved in the Colorado outbreak were over $1M on some farms when decreased production, increased labor, reduced livestock marketing options, diagnosis and treatment costs were considered.

Control Measures

A vaccine for VS is not available in the U.S., so control of biting insects is the major component of VS control and prevention:

  1. Reduce exposure to flies by reducing pasture time.
  2. Eliminate stagnant water or keep livestock away from wet areas where insects of concern are more common.
  3. Use effective approved insect repellents.

To reduce mechanical transmission of the virus, equipment and tools should not be shared between farms. During outbreaks, healthy animals should be monitored closely for early signs of illness (fevers and vesicles) so they can be isolated from other animals quickly.

State and/or federal veterinarians are responsible for making the diagnostic determination in cases of VS. They issue quarantine orders, stopping animal movement to and from affected premises. They also advise owners about disinfection measures and isolation of affected animals to protect unaffected animals on the premise.


VS outbreaks are a reminder for livestock owners to develop, fine tune, or brush the dust off farm biosecurity plans. Livestock owners will be the first line of defense in the event of the entry of a foreign animal disease into the U.S. Early detection is our best hope for containing economically-important diseases such and foot and mouth disease. Monitor your animals regularly for signs of illness and call your veterinarian immediately if you see vesicles, blisters, erosions, or the other signs previously mentioned. Let’s hope it is “only” VS or something more innocuous.

A recording of Dr. Roehr’s webinar is available from Iowa State University Extension and Outreach. He discusses dairy cattle involvement in depth.

For Additional Information

LIVESTOCK OWNERS: If you ever notice a vesicle, blister, ulcer or erosion on an animal’s mouth, teats, prepuce or feet, contact a veterinarian at once. Odds are this is not a foreign animal disease, but if it is, every hour of diagnostic and containment delay means an exponential increase in the cost of the outbreak, in both economic impact and animal suffering.

March 2015 WSU Dairy Newsletter

Amber’s Top Ten Tips: Assessing Dairy Cow Behavior

Cow comfort” and “animal welfare” are two phrases receiving an increased amount of attention from dairy producers across the nation. Have you heard these phrases recently? Do you know what they mean? How do you measure cow comfort? As you consider these questions, let’s start at the beginning: animal behavior. I spent the last seven years working on animal behavior in lizards, horses, goats, and cattle. For the purpose of this article, I will focus on dairy cow behavior. I encourage you to attempt to identify the following ten cow behaviors on your dairy and consider how changes in some of these behaviors may help you identify issues in the herd:

  1. Feeding

    Decreases in the amount of time a cow spends at the feed bunk may indicate metritis, ketosis, or, locomotion disorders.

  2. Isolation

    Isolation behavior (or seclusion from the rest of the herd) may occur prior to calving.

  3. Social

    Cows develop a social hierarchy within a herd. Cows ranked lower in social hierarchy are displaced at the feed bunk more often than cows ranked higher in the social hierarchy.

  4. Estrous

    Restlessness, chin resting on other cows, standing heat, and increases in walking are all behavioral tools used to detect estrus in cows.

  5. Maternal

    Following calving, cows lick their calves to stimulate calf activity and dry the calf’s coat. Cows may also display a flehmen response (elevation of head combined with retraction of the upper lip) towards the calf and amniotic fluids.

  6. Lying

    During the six hours prior to calving, cows will increase their number of lying bouts, but will decrease their overall time spent lying.

  7. Drinking

    Water consumption increases during heat stress conditions, but cows will decrease their time spent drinking prior to calving.

  8. Standing

    One week prior to calving and during the day of calving, cows diagnosed with ketosis increase the amount of time they spend standing.

  9. Stereotypic (repetitive behaviors that hove no obvious function)

    Increases in number of tongue-rolling occurrences within a herd may be associated with restrictive feeding.

  10. Agonistic

    As feeding space at the bunk decreases, the number of aggressive displacements at the bunk increases.

Revisiting Subacute Ruminal Acidosis (SARA)

Subacute Ruminal Acidosis (SARA) is a consequence of our selection for high-producing dairy cattle. To reach their genetic potential for production, these animals need a nutrient dense, high energy diet. Their daily dry matter intake (DMI) is greater than previous average dairy cattle DMI levels. These highly-productive animals are therefore ingesting large quantities of fermentable carbohydrates, which can overwhelm the rumen’s ability to absorb volatile fatty acids (VFAs) and regulate acidity (pH).

Although the definition of SARA can vary, multiple researchers define it as a rumen pH below 5.5 for at least three hours a day. SARA is not rare; one study reported an incidence rate of 26% of mid-lactation and 19% of early lactation cows. It is most common between calving and 150 days of lactation, especially around 90 days as DMI increases with peak milk production. It significantly reduces milk production and components, either directly or indirectly increases culling rates, and can kill cows. Annual industry costs have previously been estimated at $500M to $1B.

Risk Factors for SARA

  • Feeding high dietary levels of rapidly-fermentable carbohydrates (grains, molasses, etc.)
  • Feeding ration by components vs. as a total mixed ration (TMR)
  • Offering few large meals or irregular meals
  • Poorly-mixed TMR
  • Over-mixed TMR
  • Lack of effective fiber in TMR
  • Excessive fiber particle length, resulting in TMR sorting and grain overconsumption
  • Lack of adequate bunk space so not all animals have access to all TMR components
  • Lack of comfortable and sufficient stalls to encourage rumination

Diagnosing SARA

Microscopic image of healthy papillae.
Photo 1. Rumen papillae. These healthy papillae are numerous, long, normal color, and not stunted. They provide the surface area needed for fast absorption of VFAs so rumen pH does not drop excessively. With acute or chronic acidosis, the papillae will be blunted, blackened, missing, or eroded, and VFAs cannot be absorbed effectively. Source:

All cattle should be monitored closely for signs of SARA up until about day 150 of lactation, when decreasing feed intake reduces their risk. Signs of the condition are vague and subtle, but can include reduced milk production, reduced feed intake, weight loss, lack of cud chewing, milk fat depression, and/or foamy or otherwise abnormal diarrhea that may include intestinal tissue casts. However, some of the most important consequences of SARA may not occur for many weeks. Laminitis (founder) is a common occurrence, and rumenitis from SARA can seed the body with bacteria and result in sole abscesses, sole ulcers, liver abscesses, and even lung abscesses that erode into lung blood vessels and cause the cow to bleed to death.

Rumen pH can be measured in several animals in a group to determine the presence of SARA. Samples should be taken between 6 to 10 hours after the first TMR feeding of the day. Samples taken via stomach tube are often inaccurate, depending on where the sample was taken. A veterinarian can take an accurate sample directly from the rumen. If more than 25% of rumens sampled have a pH < 5.5, SARA is lurking in the group.

Self-correcting Mechanisms

Ruminant saliva contains natural buffers, including bicarbonate. A diet containing sufficient effective fiber stimulates rumination, which increases saliva production and self-buffering of rumen pH. Another self-regulating mechanism is feed intake: as rumen pH decreases and the concentration of osmotically-active particles in the rumen increases, appetite is suppressed—this prevents additional intake of highly-fermentable fiber and gives the rumen time to re-balance pH.

Populations of rumen microbes are highly variable and are determined by pH, feed substrates available, and other factors. Microbes need time to adapt from high fiber dry cow rations to high concentrate lactating rations. A lead time of 3 to 5 weeks is needed to prepare rumens for lactating diets. This will ensure the right microbes are present to digest feeds and regulate the rate of production and consumption of rumen acids (VFAs and lactic acid). Grain feeding results in the production of butyric and propionic VFAs, which stimulates lengthening of rumen papillae. Long and healthy papillae are able to absorb VFAs quickly and moderate rumen pH (photo 1).

Effects of Rumenitis

If the rumen lining is repeatedly exposed to low pH levels (<5.5), it can become inflamed, eroded, ulcerated, scarred, and hyperpigmented; rumen papillae are stunted and lost. The result is reduced absorption of VFAs from the rumen, which further drops pH. This condition is probably painful and reduces feed intake as well. Rumen inflammation causes production of certain proteins and other markers characteristic of inflammatory processes, and their presence is sometimes used to diagnose SARA

Importance of Regular Meals

Irregular feeding schedules, lack of adequate bunk space, prolonged pre-milking or vet check holding times, and other factors that keep cows away from feed can set the stage for SARA. Here’s why: without the continued intake of a high-concentrate ration, rumen pH rises. This can kill certain types of rumen bacteria, particularly those that use lactic acid and help keep pH from falling too low. With less of these bacteria available, the animal is less able to moderate rumen pH when it takes in feed again. Animals that have not had access to the feed bunk for a while often eat an unusually large meal when feed is made available, which also contributes to falling rumen pH.

Low rumen pH decreases the variety of rumen microbes, causing a less stable rumen pH and reducing the animal’s capacity to regulate pH. Below a pH of 5.5, lactate-producing bacteria proliferate and reduce pH even more.

Causes of SARA

  • Insufficient rumen buffering (inadequate effective fiber, DCAD, and/or natural buffers)
  • Excessive highly-fermentable carbohydrates in diet
  • Lack of rumen’s adaptation to a high-concentrate diet

Reducing the Risk of SARA

High roughage/low concentrate rations can eliminate SARA, but they won’t support maximum milk production. Rations should be fine-tuned and not supply more highly-fermentable carbohydrates than needed; contain adequate effective fiber; include buffers such as sodium bicarbonate and the recommended dietary anion-cation difference (DCAD); be re-formulated as needed to adjust for changing dry matter content of different batches of feedstuffs; and possibly include probiotics including yeast and bacteria that use lactic acid.

Corn silage is a known risk factor for SARA. It has variable digestibility and moisture and insufficient long fiber to promote rumination and buffering. It may need to be mixed with additional fiber in the form of dry hay to meet recommended effective fiber and dry matter content in the TMR.

Bunk management is critical to minimizing SARA. Ensure adequate space so all animals have access to the complete TMR, not the dregs that remain from sorting. Check the TMR throughout the day to monitor the degree of sorting that occurs and correct chopping or mixing as needed. Check to be sure the ration formulated on paper is the ration delivered to and eaten by cows. Keep feed in bunks—if bunks are empty, cows that want to eat will have nothing and their rumen pH will not be stable; SARA can ensue.


  • Plaizier, J.C., D.O. Krause, G.N. Gozho, & B.W. McBride. 2008. Subacute ruminal acidosis in dairy cows: The physiological causes, incidence and consequences. The Veterinary Journal, 176(1), 21–31. doi:10.1016/j.tvjl.2007.12.016
  • Krause, K.M., & G.R. Oetzel. 2006. Understanding and preventing subacute ruminal acidosis in dairy herds: A review. Animal Feed Science and Technology, 126(3–4), 215–236. doi:10.1016/j.anifeedsci.2005.08.004
  • Enemark, J.M.D. The monitoring, prevention and treatment of sub-acute ruminal acidosis (SARA): A review. 2008. The Veterinary Journal, 176(1), 32–43. doi:10.1016/j.tvjl.2007.12.021

Winter Kill on Grass Fields in Western Washington

Did you notice winter kill on grass fields over the later 2014 – early 2015 time period? If so, the answer may be related to lack of dormancy going into winter period.

Nutrient management is important all times of the year in forage production systems. However, the fall (September) period is the beginning of the annual calendar cycle of adapted grasses, including ryegrass. The grass plant will generate new roots and new growing points in the fall period only to shed those roots during the winter. If grasses are not allowed to transition into a dormancy state in the late fall, such as late October to mid-November, and grass growth remains active then the probability of winterkill increases.

Nutrients such as N in early fall may contribute to continued active fall growth, delaying fall dormancy. So, if we start with a low stubble harvest height in the final cutting, compound the plant mechanism of lower grass sugars and active grass growth from higher soil N availability, then add one below normal, very cold Arctic blast, we have the perfect storm for winterkill. This happened to many grass producers in 1988 resulting in thousands of westside acres of perennial grasses dead. This perfect storm was repeated in the fall and early winter of 2014. As our crops are emerging from winter dormancy and into spring greenup, the results of that perfect storm are clear.

Perennial and annual ryegrasses store the highest amount of sugars in the stem and basal (crown) tissue of any cool-season grasses grown in the PNW. We expect the range of these fructosan sugars to range above 20% to nearly 30%. Fructosan sugars can be thought of as the anti-freeze in these highly productive and high quality westside grasses. Even though the sugar may differ among grass crops, the net result is similar, increased winterhardiness and rapid regrowth after harvesting. Unlike alfalfa and other legumes where the sugar (starch in this case) is stored in the crown and tap root, cool-season grasses store sugars in the basal 3 to 4 inches of the stubble.

Grazing or cutting with machines to close to the ground will remove essential sugars for growth and survival. This is not just in the final fall harvest but all cuttings over the growing season. What sets up the critical fall grass establishment period is the summer. Measure sugar concentrations in the summer and you’ll find them lower than at any time of the growing season. In the fall, sugar levels should be at their highest, not lowest. Another important characteristic in grass management is the inverse interrelationship between nitrogen (Crude Protein) and sugar concentrations. As CP increases sugar concentrations decrease. Decreasing stored sugars reduce winterhardiness in tame cool-season grasses, such as ryegrass. Nutrient management is important all times of the year in forage production systems.

Thus, we never recommend either harvesting or grazing cool-season grasses less than three-inches. For timothy and a couple other grasses, never less than four inches. Thus, lower summer cutting heights reduce sugars proceeding into September, not a prime situation when the plants essentially establish productive potential at this time for the following year. Secondly, to increase September and fall sugar storage in the stubble and in the above ground growth, the plants must conserve sugars to transition into a state of winter dormancy.

On the westside this dormancy level does not need to be as severe or deep as Minnesota and the upper mid-west for winter survival, but westside grass winter dormancy is important. Third, nutrient applications of manure or fertilizer N may prolong fall growth, reduce sugar concentrations and inhibit winter dormancy. Timing of transition is dependent upon fall temperatures, soil temperatures, fall rains, soil moisture status, grass genetics and health of the plant.

Fall is not a time when producers can slack off on their grass management, actually the opposite is true. Fall is when you need to do the best possible job to reduce winterkill injury and enhance rapid, early spring growth.

Finally, as grasses emerge in the spring, they are often lower in sugars than when they entered winter dormancy. Avoid early turnout on to pastures until atl east six to eight inches of growth have been attained. Reduction of stands can occur in summer, when grasses are shedding roots when plants do not have enough sugars for high respiration rates in summer heat then placing the plant in a less than productive state entering the critical fall period.