Brandon Koch, Ph.D., Beef Nutritionist

August 10^th, 2020, for many farmers across the corn-belt will be a flashbulb memory. Straight line wind gusts that at points, rivaled that of a category 3 hurricane, marred a path of 770 miles in distance from South Dakota to western Ohio. Early estimates suggest nearly 40 million acres of farmland was impacted. Over 1/3 of that, 14 million, is in Iowa where damage was so significant in parts that it could be observed via satellites in space. As the extent of the damage becomes clearer, and the response of insurance claims, and equipment capability, the picture may be clearing up as to available options to regain value from derecho damaged crops.

In the days following the storm, many hoped that plants that were not laid flat and stalks that were not broken or cracked, would recover. Others began to seek out “pick-up” heads with the hope of still garnering mature corn from the fields this fall. Others with usage options were able to harvest early silage from the downed, or angled, corn. Provided proper bunker management is utilized, the lower test silage will provide ample value out of a poor situation. That being said – for those whom were still waiting for crop insurance answers, or simply don’t have the storage space or animal numbers to utilize that significant acreage of damaged corn, the fields are still full of whole plant corn that was ended early somewhere along the late R3, R4, or early R5 reproductive stage of corn (milk stage, dough stage, and dent stage, respectively).

With that said, the future of mechanical harvest of immature corn crop stands to be ineffective, inefficient, and likely provide a poor outcome for a positive return on investment given the current corn board price. Many have started to question options to utilize the crop as it stands in the field, including harvest by cattle grazing the residue. The easiest route to utilize the damaged corn plant would be harvesting it, either already as silage, or in the near future pending moisture conditions as high-grain baled corn. However, with the idea that these options are past us, or difficult and unpractical, the focus of this article will be on using cattle as a method to regain value out of immature, damaged corn crops.

Little to no literature exists on grazing whole corn plants at maturity or this far down the reproductive path. The vast majority of corn residue grazing data is conducted on mechanically harvested fields leaving little to no corn remaining in the field, or, on poorly or late harvested corn where mature, whole ears, are dropped to the ground. An accurate assessment of grain in the field can be performed by counting the total number of ears in three 30 inch rows for 100 feet. Dividing this number by two gives an approximate number of bushels per acre provided that the late harvest or poor performing combine is uniform across the field. With the whole field damaged by the derecho event on the 10th day of August, the majority of damaged corn is likely in the late milk to early dent stage.

DEVELOPING YOUR GRAZING PLAN

In order to adapt known data to this event, the first thing to do as a cattleman considering grazing cattle on whole corn plants is to gather as much information that you can utilize to make your grazing decisions. Before collecting any data however, consider the location of the field. The importance of monitoring cows daily to ensure cattle health and safety cannot be said enough. Once field that are within a manageable working area to monitor cattle, work with your Kent Nutrition Group representative/nutritionist and determine the dry matter (DM) content of the field. This can quickly be assessed by chopping or grinding a whole plant, similar to testing for silage harvest, and then drying a weighed sample to identify the DM content. While samples can be sent off for analysis, the quickest route to a crude DM that can be utilized in grazing planning is to utilize a kitchen scale, and a microwave or air fryer to dry down the sample. Both can be done in less than 45 minutes. Secondly, determine the rough reproductive age of the corn. Mature corn has a starch value of roughly 64% starch by dry weight. Corn in mid-dent stage has roughly 5 percentage points less starch at 58.7%. Kernels still in the early milk stage may only have 47% starch. Thus the corn in the field may have a starch value relative to mature corn grain of 8 to 26% less. These values will help us accurately understand the energy of the feed that will be utilized, so that we properly prepare the cattle, and their rumens, to this new feedstuff.

Making a few assumptions, you can calculate the level of grain cattle need to be prepared for. If a field is estimated to produce 200 bushels per acre, then on an ideal year, that field will produce 11,200 lbs of corn grain, or approximately 9,520 lbs of DM corn grain, per acre at 85% DM. If we assume that corn reached early dent stage by damage and final plant death, then we can make two additional assumptions: 1) a 10% reduction in corn weight, and a 5% reduction in starch content. This would mean that corn grain available would be roughly 8,568 lbs DM per acre, with a 5% reduction in starch content equating to overall a reduction in rapidly fermentable corn grain DM by approximately 17%. Thus, on a 200 bushel/acre corn field, to total available derecho damaged corn may equate to 7883 lbs of dry, mature corn per acre. The last factor to consider when considering the feedstuff available is grazing availability, and grazing efficiency. The whole plant may still be in the field, whereas only portions will still be palatable and available for consumption by grazing animals. Generally speaking as the plant dries down through September and into October, 80% of the corn will be available for grazing, with an efficiency of 90%.

CONSIDERING THE ANIMALS THAT WILL BE GRAZING

The next consideration is the animals which will harvest the crop. The maturity and growth curve, as well as production goal of that animal will dictate nutritional requirements and how the damaged, immature corn will fit within that nutritional plan. Considering that a mature cow can consume 10 lbs of corn grain, a fall calving cow may use 15 lbs of corn grain to provide roughly 75% of her energy requirements, while a feedlot calf on a finishing ration may consume upwards of 20 lbs of corn grain daily, with growing calves, stocker calves, and back grounding calves consuming decreasing amounts in the realm of 10 lbs, 7 lbs, and 5 lbs per head, per day respectively.

It is well understood that cattle do not restrict their intake willfully. As such, grazing cattle on these fields will require strip grazing as the most ideal method of controlling intake to a safe level and rate. Therefore, if we turn out mature cows or growing calves that are prepared to consume 10 lbs of corn daily, or 8.5 lbs of corn grain DM, then with our assumption of 80% ear availability and 90% grazing efficiency will result in 1 acre providing enough corn in 1 day for 568 head. On a per head basis, this would equate to 77 square feet, or, in a 30 inch row field, approximately 15.5 feet of 3 rows on a daily basis.

OTHER CONSIDERATIONS

A key consideration not to be ignored is the preparation of the rumen to be able to utilize ± 75% of their daily energy from corn grain – particularly those that have been on pasture and not seen corn supplementation in months, if ever. Typically, a rapid transition to a high grain diet program can be done by starting cattle on 1 - 2 lbs of corn daily, and increase in 2 lb increments every three days until reaching the desired intake in the damaged field grazing plan. This means that animals desired to consume 10 lbs of grain in the field will take approximately two weeks to prepare before turnout. This gap between increasing corn gives you time to monitor digestive health and adapt your preparation based on the animals’ acceptance of the diet change. Another consideration is to turn cattle out onto the pasture when they are already full, so as to not encourage over-grazing during the first exposure to a high energy feedstuff.

Also remember that if multiple fields are to be utilized, that corn content of the field will decrease at a faster rate than the forage available. As such, cattle must be quickly moved to the next field without allowing them to continue to graze the corn residue so as not to permit the rumen microflora to return to a cellulosic, or a primarily forage based, dynamic. If cattle are left with rapidly diminishing grain availability, the adaptation phase will need to be performed again. As previously mentioned, checking cattle on these fields daily will aid in monitoring grain availability and cattle health. Often, it is more ideal to keep cattle on the same field for the entirety of the grazing duration to prevent this shift in grain availability from happening, while utilizing the available acres. However, when splitting herd sizes, remember that the space needed per animal daily is small. With the need for water (well or hauled to tank), additional protein (EnergiLass® protein tub(s)), mineral (Framework 365 Mineral® in mineral feeder(s)) and forage availability (bale feeder(s)) to compensate for the nutrients not provided by the immature corn, consider the location of these items and where it will create a loafing spot in the field. If groups and daily acreage is small, consider disking a small section to start these items in and provide ample space for cattle. Ideally, cattle receive roughly 300 square feet per animal in a dry lot feedlot – far more than the daily 77 - 140 square feet allowed daily by intake of grower and finisher cattle, respectively.

An alternative to the slow, but successful diet transition program, would be to treat cattle with a lactate utilizing bacteria called Megasphaera elsdeni (Mega eTM). A technology first introduced 10 years ago, Lactipro (MS Biotec; Wamego, KS) can be given to cattle with little to no exposure to grain and immediately be provided with high energy diet. Mega e was isolated from the rumen of cattle and identified as a strong lactate utilizer. Dosing cattle with this microbe results in a microbial population that can utilize the lactate produced from grazing 10 lbs of immature corn daily, rather than the lactate building up and resulting in ruminal acidosis, bloat, and possibly death. Recently released products from MS Biotech include 12 month refrigerator stable products from time of manufacture that can be delivered as a drench (LactiproNXT) or as an intraruminal capsule (LactiproFLX) for easy use in preparing your cattle to successfully harvest derecho damaged corn.

Another tool to consider is anything that makes strip grazing and the fencing required, easier. Strip grazing will require significant fencing wire, as well as a solar or electric source to power your fence charger. It is advisable to always use two fences when grazing fields with significant corn content to limit grain consumption in the case of a cow breaking through the first fence. Additionally, the cattle can begin to graze the next strip while you roll and reset the fence for the next day’s grazing. A tool to consider that makes this easier is a “tumble wheel”. Essentially a 6 spoke star that allows the hot wire to pass through the center, and then allows the producer to roll the set of wheels the required feet to create the next strip. They replace the need for driving and pulling fence posts across the field with significant benefits of reduced labor and back aches. As with all technology, consideration should be given to the return on investment and the fitment to your operation.

As with any nutritional plan – consider your options, your cattle, and your goals, and contact your local Kent Nutrition Group representative with any questions or needed help in preparing for this, or any other event with your animals’ nutritional needs.