Buckeye Dairy News: VOLUME 24: ISSUE 4

Dr. Luciana da Costa, Department of Veterinary Preventive Medicine, The Ohio State University

Although it can happen year-round, cases of summer mastitis as the name implies increases from June to August, as the combination of wet weather and warmer temperatures encourage fly activity. It can affect beef and dairy cattle (heifers and dry cows as well). Below we briefly discuss the cause, the signs, and prevention measures for this important disease.

Cause

The primary causal organism is the bacteria Trueperella pyogenes (previously classified as Corynebacterium, Actinomyces and Arcanobacterium) in combination (or not) with other organisms (Streptococcus spp, Fusobacterium spp) to cause infection. Important to consider in the pathogenicity of disease are factors intrinsic to Trueperella pyogenes, such as the presence of virulence factors related to tissue damage (pyolisin) and others associated with mucosal adherence and colonization (neuraminidases, fimbriae, and collagen-binding protein). Additionally, Hydrotaea irritans, an insect closely related to the housefly is commonly considered to be the primary vector for the bacteria to cause summer mastitis in cattle. However, not only the presence of flies can cause the disease, but damage to the teat, trauma and irritation of the udder are also important risk factors.

Signs and Symptoms

Summer mastitis is a severe form of mastitis, causing udder damage with cows presenting high temperature and toxemia. Infected quarters become swollen, hard to touch, and not uncommonly lost. When stripping the infected quarter, the content can present a malodorous smell, and curds/traces of blood may appear as the damage to tissue progresses. Other symptoms can include irritability (as large numbers of flies often group around the udder, causing cows to kick frequently), high somatic cell count, reduction in milk yield, and a tendency toward increased culling risk since the recovery rate is low, even when treatment starts at an early stage. Still, some farmers decide to accept a loss in milk yield and sacrifice the infected quarter to save the cow – imperative in those cases is an early start on treatment and careful evaluation to preserve animal well-being. Better yet is to invest in preventive measures to reduce the chance of cows becoming sick.

Prevention Measures and Treatment

Not different from other diseases, prevention is the ideal strategy as much as possible. The main topics that should be considered to prevent or ultimately treat those affected cows include:

1. Fly control is the first line of defense against summer mastitis. In a non-organic system, a pour-on suspension applied early in the grazing season before eggs and larvae start to develop will prevent the fly population from being out of control. Several synthetic pour-on products, such as permethrin and deltamethrin, are available to control flies. Those products that are to be applied along the back of the animal usually will give protection for 4 weeks, but in times when the incidence of summer mastitis is high, they should be considered more frequently. Be aware of withdrawal time that varies among products (meat from 3 to 14 days and milk from 0 to 6 hours). Organic farms cannot apply these products and should rely on other strategies, such as fly traps, grazing management, teat stripping, and isolation of the animal (details below).

2. Grazing Conditions. Reduce larval habitats attractive to flies by removing overgrown vegetation and tall weeds which can provide cover for flies. Also, keep the area dry by eliminating standing water. Avoid cows to be near areas where likely there will be high numbers of active flies, such as soggy pastures and fields next to dense woods where flies can shelter.

3. Teat Damage. Monitoring fly numbers surrounding the udder is advised as a great number of flies will increase the likelihood of infection. Animals with any teat damage should be housed if possible.

4. Isolation of infected animals varies in accordance to the evaluation of condition or teat damage and the number of flies present in the environment. Affected animals should be isolated for better monitoring.

5. Stripping of the udder should be undertaken as often as practical but could present a challenge due to the painful and edematous teat/gland. Be careful when doing this as kicking is common due to discomfort. When stripping, please use a container (not stripping on the floor) to avoid the risk of spreading infection. More details on stripping can be found in English Stripping to control mastitis - what are the facts behind it_Final_English.pdf (osu.edu) or Spanish Stripping to control mastitis - what are the facts behind it_SPANISH_Final.pdf (osu.edu).

6. Consult your veterinarian that will consider various drugs, including parenteral antibiotic injections and/or intramammary antibiotics as well as non-steroidal anti-inflammatory drugs to reduce fever, swelling, and pain.

Jamie Hampton, Extension Educator, Agriculture and Natural Resources, Auglaize County, Ohio State University Extension

The wheat has been harvested and the fields are now ready for a different purpose. Some farmers will leave them fallow for the winter, others will plant double crop soybeans, but forages for winter grazing are an option. 

Most producers look to extending the grazing season to help reduce the need for storage of feed.  Extending the grazing season can be accomplished by seeding into a harvested wheat field.  While grazing cover crops does reduce the need for winter storage, there are other benefits to acknowledge.  Grazing cover crops provides the opportunity for a significant savings in feeding costs, improved soil health, and grazing offers higher nutrient values when compared to harvested and stored forages.

While corn silage and alfalfa are the most common selections for stored forage, the list of choices for grazing is extensive, including crops such as cereal grains, oats, annual ryegrass, peas, vetch, Sudan grass, brassicas, and clovers. The crop that is selected will depend on planting date and end goal. When grazing cover crops, most producers are looking to get the most out of the crop and tend to plant a multispecies mix to provide the best nutrition for their cattle. 

Annual or Italian ryegrass can be planted in late summer to produce a high-quality forage in late fall to early winter. Sudan grass, sorghum x Sudan grass hybrids, pearl millet, and forage sorghum grow rapidly in summer and produce acceptable yields. The brown midrib trait in sorghum has been shown to produce a forage as good as corn silage with less starch.

Oats and spring triticale can produce a harvestable yield by mid-October when planted in late summer. By November, this crop could be in the boot stage. Oats will not die until temperatures dip to the mid-20’s for several hours, and other grasses can survive even longer before they go dormant. This allows for late fall and early winter grazing.

Annual legume crops offer high nutritional values as a grazed crop but only in the first harvest because they do not regrow. Companion planting with legumes encourages better development of the grass crop.  Field peas or soybeans added to oats and spring triticale can increase crude protein 3 to 4 percentage points when planted together. Some other annual legumes to consider would be Alyce clover and lablab (bean plant).

When including brassicas, there are a few things that need to be considered.  Brassicas have very high nutrient concentrations and should be considered a concentrated feed. Research has shown some brassicas to be 18% or more crude protein and have levels of total digestible nutrients equal to or greater than 70%. Brassicas should not be more than 75% of the animal’s diet. Brassicas are not as palatable as some other forages, so it is recommended to introduce them slowly so that the animal will acclimate to the taste of the forage or use an intensive grazing strategy.

There are some management practices to keep in mind when planning for extended grazing. The cover crops that are planted should be of high-quality seed because they are providing a crop that will be harvested, just not mechanically. Consider plant disease issues; for example, you do not want to plant brassicas in the same field for more than two consecutive years because this will lead to disease buildup. When choosing your crops, consider drought resistance and if they cause health issues in your livestock. When planning to graze your summer seeded cover crops, be sure to check for any regulations concerning government programs.  For example, if you participate in the H2Ohio program, you must have a grazing management plan to go along with your nutrient management plan. You can do this with your Soil and Water Conservation Board.

Double cropping annual forages offers many opportunities to produce and utilize supplemental forage within cropping systems. It increases the efficiency of land use while protecting the soil, which would otherwise sit idle and without cover for an extended period (Mark Sulc, Ohio State University).

Resources cited:

https://hayandforage.com/article-2152-are-greens-good-for-you-.html

https://dairy.osu.edu/sites/dairy/files/imce/DIBS/DIBS31-16_Short_Season_Forages_to_Fill_Supply_Gaps_for_Dairy_Farms.pdf

https://ocj.com/2019/06/emergency-forages-for-planting-early-to-mid-summer/

Jason Hartschuh, Extension Educator, Agriculture and Natural Resources, Crawford County, Ohio State University Extension

Corn planting this year happened over a two-month time frame, making pollination very spread out this year. Currently, the earlier planted corn is from full pollination to just beginning brown silk, while later planted corn is still vegetative. The ideal time to scout corn for fungal disease and for fungicide application is from tassel through pollination. Most fields we have scouted this year show low disease pressure.

When fungal disease is present in corn silage at harvest, research shows a fungicide application at VT-R1 to control these fungal diseases reduced fiber concentration and improved nutritional value compared to the untreated control. Corn treated with fungicide had improved fermentation and more consistent dry matter values. When disease was severe, dry matter yield was also improved. When fungal disease infects corn, one of its natural responses to stop the spread of the disease is to increase lignin around the infected area which reduces digestibility.

2021 was the first-year tar spot was found in Ohio. While it is not a new disease to the mid-west, it is to Ohio. Even while working with multiple universities across the Midwest, we only have limited knowledge on its management and effects on corn silage. Currently, there are no confirmed outbreaks of tar spot in Ohio this year, but a few samples that look like tar spot have been submitted to the lab for diagnosis. Previous years have shown us that later planted corn may be at the greatest risk to losses from tar spot. One of the greatest risks to corn silage is from severe infection causing premature plant death. Tar spot reduces silage moisture, digestibility, and energy which can also lead to poor fermentation with lower silage moisture and plant sugars. Scouting for tar spot is critical and should be done weekly from tassel through R3.  Lesions will be small, black, raised spots appearing on both sides of the leaves, along with leaf sheaths and husks. Spots may be on green or brown dying tissue. Spots on green tissue may have tan or brown halos. If tar spot is found in fields, a fungicide application can help slow disease spread, but be cautious of the preharvest interval of the fungicide used with some being as long as 30 days and others as short as 7 days. With silage harvesting beginning around R4 growth stage, 50% milk line, the decision to use fungicide should be closely monitored. Another option is to make sure your harvesters are ready if the corn dies prematurely so that silage moisture is at least correct with tar spot killing plants in less than two weeks under ideal conditions.

Other leaf diseases, such as gray leaf spot, northern corn leaf blight, common rust, and southern rust can also decrease digestibility and fermentation, just not as rapidly as tar spot. Gray leaf spot has gray to tan lesions developing between the veins and are distinctly rectangular with smooth, linear margins along the leaf veins. Lesions are slow to develop, needing 14 to 21 days and begin in the lower leaves. Northern corn leaf blight lesions typically have a tan color and are elliptical or cigar shaped with smooth rounded ends. Common rust is what we usually have in Ohio, but on occasion, southern rust may be present. Common rust is rarely of economic concern, but the development of southern rust can have economic yield impacts. The colors are different between the two; common rust is brownish to a cinnamon-brown while southern rust has a reddish orange appearance. Southern rust mostly develops on the top of the leaf and may be on the stems and husks, while common rust is on both sides of the leaves and generally only on the leaves. The last difference is in shape and distribution. Common rust pustules are large and oval to elongated with a scatted appearance over the leaf. Southern rust is small, circular, and evenly distributed over the leaf. Identifying the diseases present in your corn field can help you choose the best fungicide when they are needed.

Each disease has slightly different environmental conditions that they thrive in, but these conditions can overlap or happen within days of each other. Gray leaf spot is favored by warm temperatures between 70 and 90°F and high relative humidity. Northern corn leaf blight also favors wet conditions but prefers cooler weather of 64 to 80°F. Tar spot is a cool weather disease favoring temperatures from 59 to 70°F during humid conditions of 85% relative humidity or more, keeping leaves wet for greater than 7 hours. Another cool weather disease is common rust, with optimal disease conditions being temperatures of 61 to 77°F and 6 hours of leaf wetness.  Southern rust is more of a late season disease, preferring the warmer temperatures of 77 to 88°F.

Maybe the biggest concern for dairy producers is mycotoxin contamination of corn silage and high moisture corn with many nutritionists encouraging levels below 1 ppm in corn utilized in the lactating cow ration. Fungicides may have the ability to reduce mycotoxin levels and improve silage digestibility.

Deoxynivalenol (DON) is one of the primary vomitoxins in Ohio corn. It is caused by the fungus Fusarium graminearum and causes both Gibberella stalk rot and Gibberella ear rot, making it of concern for both the grain and forage quality. One study under low Gibberella disease pressure, revealed that in all cases but one, an application of fungicide at R1 reduced DON levels by at least 50%. The trial was then expanded the second year, which was a high disease pressure year with DON levels as high as 17.9 ppm in one hybrid and 30.3 ppm in the other hybrid. Again, fungicide had little effect on these two brown midrib (BMR) hybrids yield or forage quality, but a few products did consistently lower DON levels.  A 2021 corn silage trial in Ohio showed a vomitoxin reduction from 3.1 ppm in the control to 0.5 ppm with Miravis Neo application. The products that consistently lowered DON levels contained a triazole as one of their active ingredients, with prothioconazole being the most common.  Three products that researchers across the country are seeing lower DON levels with when disease is present are Proline, Delaro, and Miravis Neo. The ideal application window from multiple studies has been R1, which is from the point when silks emerge until they become dry about 10 days later. This application is primary for Gibberlla ear rot, which infects the ears during pollination. This does create some logistical issues with application, requiring high clearance sprayers with drops for best results then over the top booms followed by an aerial application.