Buckeye Dairy News: VOLUME 27: ISSUE 1

Jason Hartschuh, Assistant Professor, OSU Extension Field Specialist, Dairy Management and Precision Livestock, Ohio State University

Corn hybrid selection is critical to maximizing your cow's production. When selecting hybrids, we usually consider factors like digestibility, energy, crude protein, milk per ton, and milk per acre. Foliar corn disease susceptibility is a critical factor to consider as it can affect both grain and forage quality, requiring a multi-prong approach to managing feed quality. Stalk and ear rots can be even more detrimental as they produce mycotoxins. Deoxynivalenol (DON), also known as Vomitoxin, can cause significant feed quality challenges in both silage and grain. The same fungus that produces DON can produce Zearalenone (ZEA), an estrogen mimicking mycotoxin that can also create many challenges for dairy cows.  

Foliar Disease

Foliar diseases can reduce yields but cause fewer grain quality issues unless they kill the corn plant prematurely, lowering test weight. However, foliar disease can cause feed quality issues in silage. Tar Spot is the most concerning as it is an aggressive disease that can kill corn plants rapidly, leading to silage moisture that is too low for proper fermentation. Even when a foliar disease does not kill the corn plant, it can lower the digestibility of the corn silage, decreasing the energy and milk per ton. When a corn plant is infected with a foliar disease, its natural response to fight off the disease, which includes hardening the cell walls around the infection so that the disease does not spread further along with the death of plant tissue in the infected area. As the cell walls around the disease area thickens, they become less digestible and so does the dead plant tissue in the diseased area, lowering the quality of your silage. Under severe disease pressure, we have seen highly digestible brown midrib (BMR) corn hybrids become less digestible than a non-BMR silage-type hybrid. 

Management of corn diseases starts with hybrid selection; however, for emerging diseases such as Tar Spot, there may not be resistance ratings available in the seed catalogs. Selecting hybrids that have good disease resistance for Gray Leaf Spot and Northern Corn Leaf Blight is your first step so that those diseases are managed through plant genetics.  Then discuss with your seed salesman what they are experiencing for Tar Spot resistance. Layering genetic resistance with fungicide applications when disease is present can maintain forage quality. When using a fungicide for foliar disease control, be sure to select one that controls the diseases you have presently. Information on fungicide efficacy for foliar disease can be found here: https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-corn-diseases.   

Gibberella Ear and Stalk Rot

The fungus Fusarium Gaminearum can infect the corn stalk by causing stalk rot, which includes rot in the stalk, cob, and grain. In both locations (ear and stalk), the mycotoxins can be produced with major concerns coming from DON and ZEA. With your support from the Ohio Corn Marketing Board and Ohio Dairy Research Fund, OSU Extension and OSU Plant Pathology have been researching a systems-based approach to DON management. This systems-based approach includes hybrid resistance screening of both corn grain and corn silage, hybrid infection reaction characterization, fungicide application method screening, weather modeling to predict disease levels, and post-harvest cleaning of corn grain.

Our first hybrid screening project for DON was done in 2023 with only corn grain, but in 2024, we conducted a screening of both grain and silage hybrids. We will continue this program in 2025. The grain screening results can be used to help with hybrid selection for both grain and silage, but corn silage can have DON toxins from both the grain and the stalk. There is no correlation between high amounts of DON in the stalk and high quantities of DON in the grain and ear. The plant resistance traits for these two areas of disease infection are probably different so there is a chance that a corn hybrid with partial resistance to DON development in the ear may not have resistance to DON development from stalk rot.

In 2024, we lost half of our silage screening plots to due to flooding after planting at the research station. This led to us only having results from the Enogen plots, which were grown in a different area of the farm to maintain the stewardship guidelines. Weather conditions for disease development in 2024 were not favorable, so across all screening trials, DON levels were low. The results from the Enogen hybrids are in Figure 1 below. Hybrids with a different letter at the top of the bar had statistically different DON levels. These plots had higher DON levels than most corn silage in the State this year. The plots were inoculated with fungal spores to cause ear rot and DON during pollination. These hybrids ranged from 0.06 to 1.46 ppm DON. Of the 11 hybrids submitted, 3 of them averaged greater than 1 ppm and 7 averaged less than 0.5 ppm. Under high disease pressure such as inoculation, no hybrid is 100% resistant. When using results from these screening trials, consider that hybrids with higher DON levels are susceptible while low hybrids are partially resistant. Under favorable weather conditions for disease development, some of the low hybrids may have been higher.  One strategy to evaluate the hybrids that you grow is to test every hybrid every year. If using silage bags, test each hybrid at feed out; for bunkers and silos, sample hybrids as they are put in. DON levels can change during the first 30 to 60 days fermentation. The goal for high-producing dairy cows is to keep the complete ration below 1 ppm DON.

^abcdHybrids with different superscripts differ.

The corn grain hybrid screening project had 80 hybrids submitted in 2023 and 90 hybrids submitted in 2024. DON levels in 2023 were much higher than in 2024. Of the 80 hybrids submitted for evaluation, 24 of them had DON levels greater than 5 ppm in at least 1 of the 3 locations and 28 hybrids averaged less than 2 ppm across the 3 locations. The DON levels were much lower in 2024, with the 2 locations we have completed the data analysis only averaging 0.4 ppm DON across all 90 hybrids. The range however was from no DON detected to 3.7 ppm. Grain hybrid DON screening data can be found at: go.osu.edu/vomitoxin

Hybrid selection is an important first step to producing feed that has low levels of DON and other mycotoxins. The second step to consider is a fungicide application; however, only Proline and Miravis Neo currently have labels for the control of Gibberella Ear Rot. Using fungicide for Gibberella Ear Rot management requires perfect timing. The fungicide must be applied while the silks are wet and must reach the silks during application. Once the silks turn brown and dry, the fungicide doesn’t move into the ear where the fungus is hiding. A fungicide can only lower the DON levels but cannot lower a susceptible hybrid to 0 ppm DON when weather conditions favor disease development. Through an integrated pest management approach, DON can be controlled so that you have clean corn silage.

Jason Hartschuh, Assistant Professor, OSU Extension Field Specialist, Dairy Management and Precision Livestock, Ohio State University

On January 17^th, USDA published the Final Federal Order Rules amending the uniform pricing formulas in all 11 Federal milk marketing orders (FMMO). The full final rules can be found at: https://www.ams.usda.gov/rules-regulations/moa/dairy/hearings/national-fmmo-pricing-hearing. These rules will go into effect on June 1, 2025 for all of the following changes except for the changes to the skim milk composition factors. The changes to the skim milk composition factors will be implemented on December 1, 2025. The changes will apply to all milk marketed after these dates and will be reflected in both the advanced pricing released before the milk is marketed and the class and component prices announced after the close of the month.

Final rules announced and passed by all 11 FMMO’s and considerations for milk price

• Updating the skim milk composition factors to 3.3% true protein, 6.0% other solids, and 9.3% nonfat solids (not implemented until December 1, 2025)
  • This change brings skim milk prices more in line with what is being produced in the industry as genetics and cow nutrition programs have changed. The modern cow is producing a more nutrient-dense product. This change will be reflected in the calculated skim milk class prices. It will also raise the Class I price in all orders, resulting in a slight increase to the pool value.  The most impact will be for producers in the 3 skim-fat Federal orders where producers are paid for set protein and other solids levels, along with the fat they produce and are not compensated for any increase in milk protein or other solids.

• Removing the 500 lb barrel cheddar cheese price from the Dairy Product Mandatory Reporting Program survey.
  • This change will adjust how cheese price is calculated by only using the 40 lb block cheddar cheese price in the monthly calculation. Over the past 5 years, the cheddar block-barrel spread has been large as these commodities move independently of each other. If only block price had been used for the last 5 years, it would have increased Class III milk price by $0.47/cwt.

• Updating the Class III and IV manufacturing allowances to $0.2519 for cheese, $0.2272 for butter, $0.2393 for nonfat dry milk, and $0.2668 for dry whey, all on a per pound basis, and updating the milk fat recovery factor to 91%.
  • This change may feel counter-productive to dairy producers as it will lower pay price, but it is an important step in the reform process to ensure processor long-term sustainability. While processors of commodity dairy products may have the benefit of knowing what they will make per pound of product processed, the only way they have been able to maintain profits as input costs like electricity or labor increased was to become more efficient. In some instances, this has led to decreased investments in processing plants and decreased producer premiums offered for high-quality milk.    

• Returning the base Clase I skim milk price formula to the higher-of the advanced Class III or IV skim milk prices for the month. In addition, the adoption of a Class I extended shelf life (ESL) adjustment for all ESL products will equal the average-of-mover plus a 24-month rolling average adjuster with a 12-month lag.
  • Over the last several years, the spread between Class III and IV milk prices has been large for multiple months. In 2020, there was a point when the Class III-IV spread was greater than $8.00/cwt; any time the class spread is over $1.50/cwt, this change will increase Class I milk price. In 2024 for over half of the year, this change would have resulted in a higher Class I milk price, putting more money in the pool and raising the statistically uniform price. This change will also help with depooling as there should be minimal times when Class I milk price falls below Class III or IV prices for over a month. This should only occur when there is a rapid change during the month from when the Class I milk price is calculated the month prior during the advanced price calculation, and when the Class III and IV prices are calculated after the end of the month. This may, however, change your risk protection strategy when using Dairy Revenue Protection or the futures and options market as you will no longer know as closely how much of your milk check will be based on the underlying Class III or IV milk prices. Choosing the higher contract between these two to hedge the portion of your milk represented by Class I prices is probably the most reliable strategy. Keep in mind that if your milk is pooled on the Federal order, the price you receive is a blend between all four classes of milk based on the processing utilization that month in the order. In most months, this change will bring more value to the FMMO 33 Pool.       
• Updating the Class I differential values to reflect the increased cost of servicing the Class I market.
  • Class I location differentials are fixed values that increase the regulated fluid milk price in a county based on the need for fluid milk and the distance milk needs to travel to consumers in that county. This location differential only applies to Class I fluid milk. The location differential is for the county where the milk is processed, not the county it is produced in. In Ohio, this location differential increase was between $1.30 and 2.30/cwt for Class I milk, but across all of FMMO 33, the increase ranged from $1.10 to 2.30/cwt. This increase will bring slightly more money into the pool from Class I milk with about a third of milk in FMMO being utilized for Class I. It will also help cover the hauling cost of moving milk into major fluid milk deficit areas, such as the southeast, hopefully bringing enough milk into these regions so that consumers always have access to fluid milk and decrease milk dumping.

In the end, the FMMO reform will have variable changes to the farm gate milk price, depending on each FMMO. In FMMO 33, Mideast, if these changes had been in place from January 2019 to December of 2023, the Statistically Uniform Price average at actual fat test would have increased $0.50/cwt.  These changes may impact how you use market-based tools in the future to manage risk between Class III and IV. It should assist at least some processors in investing in processing plants to allow for increased capacity as national milk production grows and the possibility for more competition between processors. While these recommendations were back-tested to determine their consequence, only time can tell us how these changes will play out in the markets and affect producers' bottom line. An increase in milk price often leads to an increase in production. Higher milk prices can also lead to higher dairy product prices on the store shelves and decreased consumption, all factors that cannot be accounted for in back-testing.  

Elizabeth Plunkett, Graduate Research Associate, Department of Animal Sciences, The Ohio State University

Disease presents a significant threat to animal productivity, leading to billions of dollars in annual losses. As a producer, you do everything in your power to mitigate disease risks in your operation, but unfortunately, disease is opportunistic and will strike when least expected. While disease can be challenging to mitigate, it is often easy to spot by observing cow behavior and productivity. The signs that we initially observe and associate with disease are the consequences of physiological adjustments that are a part of the host’s response to an abnormality. At first glance, these responses might seem counterproductive. For example, why would a cow go off feed at a time when her metabolic requirements increase exponentially? However, the physiological adjustments present at the onset of disease are a set of highly organized and calculated survival mechanisms that have been evolutionarily favored for centuries. Understanding the biological rationale behind these responses reveals how they collectively contribute to the cow’s initial defense against pathogens.

Reduced Feed Intake:

Interleukin-1 (IL-1) is a cytokine that plays a crucial role in regulating the immune response. When IL-1 is released, it triggers a decrease in appetite. Although it might appear unfavorable when sick cows stop eating, it is actually a protective mechanism. Listed below are several plausible reasons why this is a beneficial response during sickness, and for more information into this perplexing phenomenon, I encourage you to read Brown and Bradford (2021), which reviews these mechanisms in greater detail.

1. When cows consume less feed they divert less energy towards digestion, which is an energetically costly process. Creating less energy usage allows for more energy to go towards fighting the infection and fueling vital organs.
2. The pathogen may be present in the feed so limiting intake helps reduce overall pathogen load. Additionally, if the pathogen is in the feed, reducing intake would allow the gastrointestinal tract time to heal and prepare for future intake.
3. Cows may simply lack the motivation to eat. If feeding requires them to walk a great distance or fight for their food, they may not feel up to the challenge when they are sick. It may be more energetically costly for them to approach a feed bunk rather than staying put to conserve energy.
4. Looking at this from an evolutionary perspective, limiting feed intake during sickness is a prey instinct. Historically, cows are grazing animals; therefore, during times of sickness, it is unwise to put themselves in such a vulnerable position when they can’t promptly respond.
5. Eating less helps reduce iron intake which is an important mechanism to ‘starve’ the invading bacteria. Some bacteria require iron for proliferation and growth; therefore, limiting intake helps reduce nutrient availability for the invading pathogen.

Decrease in Plasma Iron Concentration:

Iron is an essential mineral for some bacteria as they need it to grow and proliferate. During bacterial infections in cattle, we see a reduction in iron concentrations. This reduction is not due to increased excretion but rather the redistribution of iron throughout the body. For example, during mastitis, transferrin concentrations in milk will increase as transferrin will work to bind free iron to keep bacteria from acquiring it and utilizing it to multiply. The release of IL-1 also causes iron concentrations to decrease. Additionally, the reduction in iron concentration acts synergistically with fever to hinder bacterial growth in the early stages of disease. While they both work to suppress bacterial growth, one is not dependent upon the other and one can occur while the other does not.

Fever:

Fever is a temporary increase in the body temperature set point, not to be confused with hyperthermia which is an increase in body temperature without an adjustment made to set point. Fever is controlled by IL-1, and it helps make the body less welcoming to infections as some bacteria and viruses can’t survive at higher temperatures. Immune cells also have enhanced performance during fever, primarily due to the actions of IL-1, but also due to the heat fever creates. To reach and hold this new higher temperature, the body must make several changes. It does this by reducing heat loss and/or generating more heat. For example, sick animals often curl up in an attempt to reduce their surface area and limit heat loss. Additionally, blood flow will shift to internal organs, leaving the extremities to feel cold to the touch (e.g., cows’ ears feed cold). Another way the body reduces heat loss is called piloerection, which is when hair follicles stand up. While the body does everything it can to retain heat, sometimes this is not enough. If it can’t hold the heat, the body will increase heat production by speeding up metabolism, which is energetically costly. Fever can increase overall metabolism by 30-50%, creating more stress on the cow if this response is prolonged.

Depression and Lethargy:

Just like when we are sick and all we want to do is stay in bed, cows behave in similar patterns. There are multiple benefits of depression and lethargy during disease. Cows may curl up and move less as a strategy to conserve body heat and minimize the use of nutrients for non-essential functions. IL-1 also plays a role in inducing sleepiness, as it is involved in promoting rest and reducing activity in response to illness. This is why an activity monitoring system can help us detect illness in cows because they will be moving less to conserve energy. This depressive state helps the cow conserve energy for essential functions, allowing her to focus on launching her defense.

These physiological adjustments that occur during disease work with one another to provide an initial defense mechanism against invading pathogens. These responses work together to protect the host, but they neither the same purpose nor do they depend upon one another. Even cows subjected to the same pathogen will have variations in these responses and may present with different clinical signs. Making the approach to resolve the issue is difficult and case-dependent. While these mechanisms are biologically normal, their prolonged presence can create just as much damage as the invading pathogen. Leading furthermore to the question, we continue to ask ourselves: When do we treat and when do we let these processes run their course?

Stay tuned for the next article which will answer this question and many more!

Disclaimer: This article is intended to explain and inform readers about some common physiological responses observed in ill lactating cows. It does not constitute veterinary advice or recommendations for treating animals. For specific concerns and treatment plans, please consult a licensed veterinarian.

Sources:

1. Brown, W.E., and B.J. Bradford. 2021. Invited review: Mechanisms of hypophagia during disease. Journal of Dairy Science 104:9418–9436. doi:10.3168/jds.2021-20217.
2. Hart, B.L. 1988. Biological basis of the behavior of sick animals. Neuroscience and Biobehavioral Reviews 12:123–137. doi:10.1016/S0149-7634(88)80004-6.