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Feedlot calves
Iowa Beef Center, Iowa State University
June 2016   Volume 6, Issue 12
In this issue
Managing Heat Stress in Feedlot Cattle
By Dan Loy, Iowa Beef Center director, and Grant Dewell, ISU Extension beef veterinarian

During a heat stress incident in southwest Iowa on July 11 and 12, 1995, an estimated 3,500-4,000 cattle died of heat stress. A deadly combination of temperatures exceeding 100 degrees, 50% relative humidity and no wind or cloud cover centered over the region. In the Midwest, deadly combinations such as this one are usually short lived but can occur any time from June to August.

Dr. Terry Mader, retired beef specialist at the University of Nebraska, has noted that an incident similar to the one described has occurred somewhere in the central and northern plains states each year from 2009 to 2013. To prevent cattle losses during such heat events, feedlots should implement one or more mitigation strategies.

Shade. After the 1995 incident, ISU beef specialists Darrell Busby and Dan Loy surveyed feedlot managers in the area about which heat stress factors and management practices, and shade was the most effective prevention method. In fact, where cattle were provided access to shade from a building or constructed shed death loss was no different than normal conditions. It is suggested to provide at least 20 square feet of shade when building structures for feedlot cattle.

Water and sprinkling. In the survey, producers also indicated that sprinkling or spraying water on the cattle was effective. Cattle cool by evaporative cooling so intermittent sprinkling is one method. Cattle will also walk in and out of continuous sprinkling. South Dakota State University has evaluated methods of wetting the feedlot surface in the evening to reduce the lot surface temperature.

Signs of heat stress.  As cattle accumulate heat during the day they will show multiple signs of heat stress. Initially cattle will increase respirations as they try to cool themselves by panting. As the heat load increases, cattle will become restless and begin to drool. Even though, at this stage, cattle are spending energy trying to cool themselves they are in danger. With additional increases in the heat load cattle will begin to breathe through their mouth, which is an indication that a heat mitigation strategy should be implemented if it has not been initiated proactively. The last indication is that cattle will protrude their tongue as a last attempt to increase cooling. These cattle are at risk of dying and even if they survive, may take time to recover. Care should be taken to not increase other stresses when trying to cool these cattle.

Feed and water consumption. Expect feed consumption to decrease during periods of heat stress by as much as 20%-40%. In these circumstances, cattle tend to eat more of their feed in the evening so many feedlot managers will adjust feed deliveries to account for this. Water consumption can increase significantly during periods of heat stress so be sure to provide adequate water and drinking space for each animal. Individual animals can consume as much as 15-20 gallons per day during these periods, so be sure to provide at least 1-2 linear inches of drinking space per animal. This may need to be increased to 3 linear inches during severe heat events to provide proper access to water. 
Cover crops provide grazing opportunities
By Erika Lundy, ISU Extension beef program specialist, and Rebecca Vittetoe, ISU Extension field agronomist

Cover crops have become quite popular in recent years, not only from a soil conservation and water quality perspective, but also due to their potential to be an additional forage source for livestock producers.

To better understand how cover crops can be used as a potential forage source, Iowa State University Extension and Outreach started a grazing cover crop project the fall of 2015 at the McNay Research Farm near Chariton and the Allee Research Farm near Newell.

The focus of the project is to evaluate cattle performance and potential grazing days on a cereal rye cover crop, and to assess the impact grazing has on the soil health aspects that cover crops provide, such as helping to reduce compaction and build organic matter.

Prior to planting the rye cover crop last fall, baseline soil measurements were taken including bulk density and soil moisture. The same soil measurements were taken again this spring prior to grazing and then after the rye cover crop had been grazed. The bulk density measurements taken from one of the grazed fields are summarized in Table 1 and soil moisture measurements in Table 2.

Rye drilled behind soybean harvest the last week of October and first week of November at the McNay Farm yielded approximately 2 tons (DM) whereas rye aerial seeded into standing corn at Allee Farm yielded less than 1 ton (DM).

Preliminary results of grazing cover crop
Due to excessive moisture this year, cattle turnout was delayed, and grazing days only equated to a two to three week period. Although performance is hard to determine on such a short window, preliminary average daily gain (ADG) is evaluated to approximately 1.00 lb/hd/day while grazing. Initial nutrient analysis of the rye suggests that cattle grazing a lush, green cover crop need to have access to dry forage such as hay because physically they cannot eat enough fresh forage to meet their nutrient requirements.

Yearling heifers graze at ISU McNay Farm.Part of this project was to evaluate what one may expect with soil compaction from grazing. Soil types in a field as well as soil moisture conditions when grazing the cover crops can be linked to what one may expect for soil compaction.

One method that can be used to determine soil compaction is by measuring soil bulk density, which is a reflection of soil porosity. Compacted soils have higher bulk densities, and less soil porosity, that restrict water infiltration and plant root growth. Soil texture also affects bulk density. More information on soil bulk density can be found in the NRCS publication "Soil Quality Indicators: Bulk Density."

The preliminary results from the McNay Research farm show that cereal rye cover crop reduced bulk density and soil compaction, but bulk density increased after grazing the rye cover crop. Prior to grazing the rye cover crop and during grazing, the soil moisture content was at or above field capacity (40%).  The increase in soil compaction after grazing the rye cover crop is not surprising, given the wet soil conditions of the poorly drained soils at the McNay Research Farm. These conditions are very conducive to soil compaction during grazing.

Looking at the bulk density results and the soil texture of the field (silt loam or silty clay loam), the bulk density results  still fall in the range bulk densities considered as ideal  for plant growth according to the NRCS's general relationships with soil texture and bulk densities, which would be less than 1.40 g/cm3.

Management tips for grazing cover crops
  • Ways to manage soil compaction due to grazing cover crops include removing livestock if soil conditions are too wet or by utilizing rotational or strip grazing.
  • With grazing cover crops or using them for forage, it is important to consider herbicide restrictions, and how that may or may not limit the ability to graze or use cover crops as a forage source.
Table 1. Bulk density measurements.
Soil Depth (in) Bulk Density (g/cm3) % reduction (before grazing) % increase
Baseline Rye, no grazing After-grazing
0-6 1.34 1.26 1.35 - 6.5% +6.8%
0-12 1.37 1.25 1.36 -9.0% +8.2%
Table 2. Field average soil moisture measurements.
Date March 30 April 22 May 5
% Soil Moisture 40.0% 45.8% 48.4%
This preliminary year has been a learning curve for all involved in this project. Funding will be sought to continue this project for the next three years to help learn more and provide research-based information to help producers make management decisions on grazing cover crops and the sustainability of this integrated crop-livestock system.
Iowa Beef Center Director column
Farming as a system
By Dan Loy, IBC director

According to many accounts crop production is currently a breakeven enterprise for many grain producers. While feedlot cattle margins have been quite volatile recently, over the long term they also tend to be a breakeven on the average according to many economists. To be highly successful in either enterprise producers must be more efficient, have lower costs of production and/or be better marketers.

For farming operations with both cattle and crop enterprises, taking advantage of the synergies that can occur between these can be a major efficiency itself. We call this farming as a system. Systems thinking is not new in beef production. Holistic management in ranching by looking at the land, labor, forage and cattle together as a system is a popular approach to ranch management.

The synergies inherent in a well-managed cattle-crop farming system can provide efficiencies and cost reduction. They can also buffer the risk associated with the price cycles of grain and cattle.

One example of the integration of cattle and crops is the use of corn silage. Corn silage was the king of cattle feeds in the late 1970’s. Most cattle feeders fed it. Farms and feeding operations were smaller and corn silage maximized beef production per acre. The predominant ration of the time was corn silage, 1% of the animal’s bodyweight in corn and a protein supplement. This allowed a typical steer to gain 2.5 pounds per day with feed conversions of 8-9 pounds of dry matter per pound of gain. The system allowed one turn of high quality beef to be fed each year.

Read all of this column on the IBC website.
Midwest Region Angus Advisor (Angus Journal)
Maximizing the Value of Estrous Synchronization

By Patrick Gunn, ISU Extension cow-calf specialist

Although the focal point of most breeding season strategies is to determine which bulls will be added or subtracted from the line-up, it is equally as important to evaluate the method by which these genetics will be introducing in to the cow herd. 
Given the current yearly costs of the breeding herd hovering around $800/head in the Midwest and the sustained volatility of commodity markets, it is imperative that producers strive to implement genetics that allow for greater production with fewer inputs.

One potential way to increase production and minimize input is through the use of artificial insemination (A.I.) when used in conjunction with estrous synchronization.

In a study published in the Journal of Animal Science in 2012, it was reported that cows submitted to a timed-A.I. estrous synchronization protocol had a return on investment that netted $49 more per cow exposed than cows which were only exposed via natural service.

Read all of this column
Educational Opportunities

A new publication from Iowa Beef Center, Growth Promotant Implants for Cattle - IBC 113, has guidance for beef producers on how to develop an appropriate strategy for using growth promoting implants and find the right implants for that strategy. The publication also contains a table of currently available implants categorized by potency and active ingredient, and info on which animal class (suckling, stocker or feedlot) is approved for each individual brand of implant.

The Silage for Beef Cattle Conference is set for June 17 at the UNL Eastern Nebraska Research and Extension Center near Mead, NE. It's sponsored by University of Nebraska--Lincoln, Iowa Beef Center/Iowa State University and Lallemand Animal Nutrition. Register to watch the live streaming if you're unable to attend in person.

Sericea Lespedeza is becoming a more prevalent weed in southern Iowa, and controlling this weed is becoming a bigger issue for producers. IBC and ISUEO are hosting two sessions of a June 21 weed and brush field day focusing on this weed at the McNay Research Farm.

Learn about crops following cover crops and the latest on handling area weed pressures at the June 22 weed and brush management field day near Corning. No cost for the event, which includes a free ribeye steak sandwich meal.

Veterinary Feed Directive Q&A

Why do I need a VFD when I used to be able to use these medications on my own?
In response to concerns about antibacterial resistance impacting human health, the FDA is restricting the usage of medically important antibiotics in livestock feed. These restrictions include the removal of production claims (i.e., increase rate of gain or feed efficiency) and over-the-counter (OTC) availability.
What about Ionophores and anti-coccidials?
Ionophore antibiotics such as monensin (Rumensin™) and lasalocoid (Bovatec™), bambermycins (Gain-Pro™), and bacitracin are not “medically important for humans” so these antibiotics are not affected by the changes in the FDA policy. Anti-coccidials (Deccox™ or Corid™) and dewormers are not antibiotics so they are not affected by the new regulations.
VFD goes into effect January 1, 2017

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