Progress report for ONC20-076
Forage cover crop utilization has gained popularity across the Midwest because of the conservation and soil health benefits. Additionally, these forages are a high quality feed resource that enables beef producers to increase condition of animals before winter or opportunity for high rates of gain. Improving grazing efficiency and decreasing waste can significantly impact the economic viability of a forage cover crop grazing scenario. However, producers struggle to find an effective grazing strategy optimizing the economic return of fall-grazed forage cover crops. This project will evaluate the effects of stocking density on grazing efficiency and body condition score (BCS) of cattle fall-grazing cover crops in a continuous grazing system and a strip-grazing system. Cattle in the continuous system will have access to graze the entire field. Cattle in the strip-graze system will be moved to a fresh paddock every 3 to 4 days. The project will be replicated across 5 different cooperator sites in Nebraska with forage biomass and quality measured before and after grazing.
- Demonstrate establishment practices in a cropping system for fall grazing forage cover crops and techniques to increase harvest efficiency.
- Collect and evaluate forage and animal performance data on replicated, partnering producer sites to measure the impact of stocking density on fall grazed forage cover crops.
- Educate producers, industry, and peers about optimal establishment and utilization of forage cover crops with field days, cooperating producer demonstration sites, social and traditional media outreach, professional publications and presentations.
Producers are recommended to plant a brassica/small grain mixture. Ideally the following seeding rate would be used: 50 lb. oats, 3 lb. rapeseed (or 4 lb. turnip or 5 lb. radish)
Prior to grazing, place 3 exclosures on the continuous graze/control. Placement should be at random while avoiding field edges and areas that are unrepresentative of the site as a whole (overly wet areas, near water, exceptionally poor soils). This can be done by dividing the field into quadrants and assigning the cages to a quadrant at random.
Each exclosure will consist of 2 t-posts and 2 cattle panel halves bent to 90 degrees. To cut the panels in half, bolt cutters work best. Find the middle segment and cut as close to a vertical bar as you can. Then cut the excess off the other side trying to avoid long, sharp edges.
Drive one t-post into the ground and use the cattle panel as a guide for where the second should go. Try not to step in the area between the posts too much to avoid trampling. Once both posts are in, align the panels so that the ends meet at the t-post. Wire both ends of the panel to the posts with a top and bottom wire. Cattle like to rub on these, so make sure they are secure. ID each exclosure in some way that will not be easily eaten or rubbed off by cattle. A cattle tag and wire is effective.
Work with producers to keep a log of precipitation from planting date until the end of grazing. Temperatures should be fine to extrapolate from the nearest MESONET station.
To give producers flexibility, we are not going to set a specific goal for grazing date. However, noting animal condition and plant maturity stage/height at turn out will be important. It is also good to keep record of any other treatment that has been applied to the crop and take notes (irrigation, fertilization, etc.).
Target grazing will have animals on treatments for 45 days or longer. As the continuous grazed treatment will most likely require animals to be removed first, set area and number of head for this treatment first to best reach the 45 day goal. Once the continuous treatment is set, stocking rate can be determined and used to set number of head and area of the strip grazing treatment. Each location will be treated as a replication, so matching stocking rate across locations is not necessary, as long as the initial target stocking rate at a location is the same. Previous studies have seen 100 to 150 lb/day disappearance.
For the strip grazing treatment, set up an initial strip that will provide animals with 1 week worth of forage to allow animals room and time to acclimate to the new conditions. After this initial strip, allotments will move to the 3-5 day forage goal. Producers can adjust strip size as needed to meet this goal. Ideally, stubble heights of 2-3 inches can be used to gage animal utilization and adjust strip size. For summer annuals, 12 inches of stubble height may be a more realistic goal.
Producers will be asked to place a wooden stake out to mark each grazing allotment on the strip side as they move in order to help us more accurately assess stocking density and locate previously sampled sites for post-grazing biomass collection. At the end of the grazing period, strips will be measured to provide an accurate area of each grazing allotment.
Biomass Production Sampling:
Before planned turn-out, take 3 samples for biomass production of the strip and continuous grazing treatments at random across the entirety of each treatment. These samples will be sorted by functional group (small grains, brassica, legume, etc.) and a green weight taken. Non planted species will be their own functional group (weeds). Each sample will be an area consisting of 3 drill rows and the corresponding 3 inter-row spaces for width and 3 feet in length. When doing the first sample, measure the row width and record so total sample area can be determined.
All plants will be cut off at ground level, except brassica species that may be grown for their root mass (turnips and radish). For these, the plant will be pulled and whatever comes up will be the sample. The root mass and top will then be separated. The samples will be placed in brown paper bags and labeled with date, functional group, treatment, and sample ID number.
After harvest, a green weight of each functional group will be done. Tare the sample bag and record the sample to the nearest gram. Samples will then be packed in their paper bags and boxed, overnight shipping to Lincoln to get a dry weight.
Biomass samples will be taken at 5 times over the course of the grazing season. The first clipping can be taken as soon as animals are in the 3-5 day move schedule for the strip grazing treatment. Each time will consist of 3 pre-grazed clips from the rotational group, 3 post-grazing clippings along the previously sampled transect in the rotational group, and 3 random clippings in the continuous grazing treatment.
After the pre-grazing sampling, samples in the strip treatment can be taken at random within a grazing strip. Continuous treatment samples will be taken at random in that treatment area, taking care not to sample an area that has already been clipped.
For post-grazing clipping, the same area will be clipped (3 rows by 3 feet) and the remaining forage sorted by functional group. These samples will be taken at random in the same strip as the pre-grazed sample was taken, the only stipulation being to avoid clipping areas where a previous sample has been taken. Any new growth, unless completely unusable (covered in mud, under a cowpie) can be sorted into the appropriate functional group.
The final sampling will need to be in the last strip grazing allotment to capture final production. When this pre-grazing clip occurs, the grazing exclosures can be clipped and sampled for total production as well.
Once grazing has been concluded, a final clipping of 3 post-grazed random samples in the continuous and 3 post-graze transect samples in the rotation can occur.
Quality sampling will occur 3 times alongside the production samples at the pre-graze date, mid-grazing, and late grazing periods. For these samples, each functional group will be clipped at random to fill a gallon Ziplock bag and frozen. Bags should be labeled with functional group and sample date. For the strip grazing, this will come from the ungrazed portion of pasture. For the continuous grazing, this will be at random in the pasture as a whole.
An additional set of samples will be taken at the pre-graze clipping and sent to Ward Labs for analysis. This will be wet lab and tested for protein, ADF, and TDN.
Upon completion of the project, all frozen sample bags can be overnight shipped to Lincoln. Ship in a cooler container on ice to keep samples frozen and prevent degradation. Analysis will be run at UNL Animal Science Department.
Project implementation and data collection were the majority of efforts in 2020 and 2021. The beginning of the project consisted of setting up consistent protocols for implementing and sampling procedures across sites. With planting and grazing occurring in the fall and early winter, the only other actions able to be taken were data collection. Preliminary data showed less forage loss due to trampling and increased utilization evidenced by increased head days per acre for the strip-grazing treatments. Continuous grazing is apt to produce more gain per animal if grazing for less than 90 days due to the opportunity for diet selectivity; however, strip grazing does achieve more calf gain per acre than continuous grazing and lowers the cost of gain, even with the additional labor. Analysis of final statewide results along with outreach and education efforts stemming from our findings will occur in 2022.
Summary of results from site in East Central NE
A mixture of oats and rapeseed was planted at a rate of 50 lbs/ac and 3 lbs/ac, respectively, in early August. Crossbred steers (n = 84; initial BW = 524 lbs; SD = 37 lbs) were limit fed for 5 days prior to being weighed and assigned to one of two grazing treatments: 1)Continuous grazing (CONT) or 2)Strip grazing with new strips allocated twice weekly (STRIP). Steers were stocked at a rate of approximately 1 steer per acre in 6 paddocks, with 3 paddocks for STRIP and 3 for CONT. Each paddock was 15.5 acres with 14 hd per paddock. Grazing began on November 12, 2020 and ceased after 83 days of grazing on February 3, 2021. Electric fence was moved in each of the strip grazing paddocks on Monday and Thursday of every week to allow access to a new strip. Backgrazing was permitted. Forage samples were collected monthly to measure yield and nutritive value by randomly clipping samples throughout each paddock to ground level. Initial forage yield (4,356 lb/ac) and nutritive value did not differ between CONT and STRIP but rapeseed was greater in digestibility (80.1 % digestible organic matter) and crude protein (15.8 CP) than oats (70.5 digestible organic matter and 8.4% CP). Forage nutritive value decreased slightly throughout winter. A lower disappearance (44.8 lb/hd/d vs 63.1 lb/hd/d) and a greater head days per acre (140 vs. 75 hd days/ac) for STRIP compared to CONT suggest an increase in forage utilization. A greater average daily was observed for CONT with 1.67 lb/d for STRIP and 1.98 lb/d for CONT. Steers that grazed continuously had access to the entire 15.5-acre paddock, which presented an opportunity for diet selection. Steers likely selected the more nutritious plants (rapeseed) and plant parts (leaves) which resulted in a greater rate of gain. However, strip grazing resulted in a greater gain per acre (232 lb/ac for STRIP vs. 148 lb/ac for CONT), likely due to decreased diet selectivity and increased forage utilization. Despite labor costs associated with moving electric fence twice weekly, STRIP had a $0.12/lb lower cost of gain. Based on these results continuous grazing for <90 days is optimal if the goal is to achieve a high average daily gain in a relatively short amount of time. Strip grazing is optimal if the goal is to achieve greater forage utilization while still attaining moderate to high calf gain.
Educational & Outreach Activities
Consultation with cooperating producers on project planning and implementation occurred in 2020 and 2021. Preliminary results were presented at several meetings including the American Forage and Grassland Council, Nebraska Cattlemen's College, Nebraska Sustainable Agriculture Society Conference, and Driftless Region Beef Conference reaching 130 participants. Final statewide results are currently being analyzed, and education and outreach efforts are being planned for 2022.
Increased utilization of simple cropping systems in the Midwestern United States has led to concerns regarding
the long term sustainability, with problems of soil erosion, nitrogen leaching, increased runoff, and overall lower
soil health. Diversifying these systems with forage cover crops addresses these issues by providing longer
periods of active plant growth, increased biodiversity, soil cover, and positive soil and nutritive effects.
However, adding annual forage cover crops burdens the producer with increased costs of establishment and
labor. With high nutrient potential, producers overcome these barriers by utilizing these forage cover crops as a
high quality feed source for cattle. Research on grazing systems has produced mixed results regarding grazing
efficiency. A better understanding of how stocking density and grazing method affects grazing efficiency will
support sustainability and land stewardship, while providing economic viability to the producer. This increases
the opportunity for young family members to return to operations and maintain a valued rural lifestyle.