Comparison of Annual Forages for Grazing Lambs on Previously-Cropped Ground
The annual lease on 17 acres of marginal cropland, most recently planted to corn (9 acres) and soybeans (8 acres) was obtained in December 2012. Oats were planted (with no-till drill) on April 5, 2013 on the 17 acres. Fencing supplies were purchased in April and May, 2013.
Starting weights were taken on May 22, 2013. 48 lactating ewes weighed an average of 140 lbs. each. 85 lambs, still nursing on those ewes, averaged 49 lbs each. The average age of the lambs was 77 days or 11 weeks, so most were old enough to wean at this point in time; the decision was made to not wean the lambs and to let the ewes and lambs graze together because of the anticipated rapid growth of the oats once grazing began, the short time to utilize the oats before maturity, and the resulting need for more animal units per acre. In addition, 19 yearling ewes, not raising lambs, averaging 131 lbs. each were included in the grazing group. The total beginning weight of the animals being grazed was 13,408 lbs. The animals grazed amounted to a total of 21.9 animal units, using the conversion factor of 5 adults or 10 lambs per AU.
On May 25, 2013, this group of lambs and adult sheep (85 lambs, 67 adults) began grazing 9 acres of oats. Electric fencing was used to strip graze the sheep on these 9 acres, with the animals moved to fresh ground every 1 to 3 days. Forage clippings were taken at three different points to estimate total forage dry matter available; on May 24 (the day before grazing began) a sample of three clippings estimated total DM at 1,667 lbs/acre, indicating an average increase of 35 lbs DM/acre/day since planting on April 5. On June 3, a sample of three clippings showed 2,200 lbs DM per acre, an increase of 53 lbs/acre/day since May 24. On June 21, a final sample of three clippings from the 9 acre field showed 9,133 lbs DM/acre, an increase of 385 lbs/acre/day since June 3. Obviously DM production increased rapidly as the oats neared maturity (see Figure 1 – DM produced per day.jpg); however, the samples selected for clipping on June 21 may not have been representative of the entire field and may have overestimated total DM availability. By comparison, the 8 acre field, which was cut for hay on June 23 produced a total of 42,735 lbs of baled hay, or 5,342 lbs of harvested forage per acre.
The sheep were grazed on the 9 acre field for a total of 35 days, until June 29. Parasitism was monitored but no deworming was required. The 85 lambs gained an average of 16.3 lbs. or 38.4% of their starting body weight (0.43 lbs/day). The 48 lactating ewes lost an average of 4.4 lbs, 2.8% of starting body weight, or -.11 lbs/day. The 19 yearling ewes gained an average of 4.8 lbs, 3.7% of their body weight, or .13 lbs/day. The economic value of the lambs’ weight gain relative to establishment costs for the forage are discussed in the objectives/performance targets section.
Because not enough animal units were available to harvest all of the oats through grazing before the grain reached maturity, the 8-acre field was cut for oat hay on June 23. A total of 37 bales of hay, averaging 1,155 lbs. each were harvested, for total forage production of 42,735 lbs, or 5,342 lbs per acre. This hay was stored and used as livestock feed on the farm the following winter. The economics of harvesting the hay versus harvesting the forage via grazing lambs are discussed in the objectives/performance targets section.
After the hay was harvested on June 26 and grazing was completed on June 29, light tillage with disk and field cultivator was performed to prepare the oats stubble for establishment of summer annual forages. When the investigator attempted to order forage seed, both Pearl Millet and BMR sorghum were sold out for the three Missouri seed dealers contacted. Since the investigator had already tried grazing sorghum-sudangrass hybrids with sheep, with limited success, the decision was made to plant all 17 acres to teff grass (rather than 9 ac to teff, 4 ac to BMR sorghum, and 4 ac to Pearl Millet as originally planned). Teff grass seed was obtained and teff grass was planted on July 1, using a Brillion seeder/packer.
Unfortunately, this is where success with the grazing of annual forages project came to an end. After a wet April, a moderate May, and a slightly dry June, we entered a summer drought for July and August. No measureable precipitation was recorded on the farm in July or August. The oats had taken up most of the available soil moisture and tillage in preparation for seeding the teff grass (which requires a firm, well-worked seedbed) had depleted remaining moisture from the topsoil. There simply was not adequate moisture to germinate the teff grass. By mid- to late-August, the 17 acres consisted of some annual weeds (mostly pigweed) and scattered tufts of teff grass (uploaded PowerPoint presentation contains photos). Lambs were turned into the field in late August and early September, but grazing was very limited and mostly consisted of the animals nipping the leaves off of the pigweed. No weight data were recorded.
In mid-September, the investigator decided to do light tillage and seed winter wheat and crimson clover (on part of the acreage) to take advantage of anticipated fall rains and have winter annual cover for grazing/finishing lambs. The seeding was fertilized with 50 lbs/acre of N (urea) to encourage early fall growth for grazing. Unfortunately, the dry weather continued into the fall. Wheat germination was only moderate, and there was not sufficient growth before dormancy set in and snow cover took over. A colder-than-normal winter limited growth and no winter grazing was obtained off of the field at all. Significant growth did not occur until late March/early April of the following year and at that point the decision was made to let the wheat mature and harvest it for grain so that the field could be seeded back to perennial forages.
One of the grant objectives was to document dry matter (DM) production and animal units (AU) or Animal Unit Months (AUMs) provided from various annual forages. Careful measurements were used to document DM production for oats and utilization of dry matter by grazing sheep. The estimated DM production per day at various points in the oats’ production cycle was documented in the Summary section. DM available was estimated based on forage height prior to turn-in to a new section of forage and DM remaining was estimated based on forage height and trampled forage when the animals moved on to the next paddock or strip. The difference between these figures was recorded as an estimate of DM intake by the grazing animals. Based on these measures, it is estimated that the animals consumed 21,864 lbs. DM during the 35-day grazing period, or 2,429 lb/ac. If we take the lbs of hay harvested off of the adjoining field as an estimate of total DM production during the oats growing period (5,342 lbs DM/ac), this indicates a forage utilization rate by the grazing sheep of approximately 45%. The estimated DM intake of 21,864 lbs. during the 35-day grazing period would indicate that the sheep were taking in about 4.4% of their body weight in DM per day; this is higher than would be expected, and may be a function of under-estimating the remaining residue when the animals were removed from a grazed area, thus over-estimating intake.
The oats during their grazing period provided 25.55 Animal Unit Months (AUMs) of grazing, or 2.84 AUM/acre. This calculation is based on a 35-day grazing period (1.17 months) in which 21.9 AUs grazed on 9 acres of forage.
Unfortunately, DM production of teff grass and winter wheat could not be evaluated because of minimal emergence or available stand for measurement or grazing.
Another objective of the grant was to document the economic returns of grazing annual forages on marginal cropland versus raising annual row-crops on those acres.
Sufficient data were gathered on lamb weight gain versus the cost of forage establishment for oats to make this comparison. Since part of the oats were harvested as hay, the implied revenue from hay production is also calculated and compared to that from grazing lambs. Even though teff grass establishment was not successful due to lack of rainfall, the investigator made some assumptions about how much grazing and how much lamb weight gain might have been obtained from grazing the teff grass under more normal growing conditions. The comparison table has been uploaded (see Economics of gain from forages – Sheet 1.pdf).
In short, lambs gained a total of 1,382 lbs on oats during a 35-day grazing period (their mothers, also grazing with them, lost a small amount of weight, not unexpected and something they will easily regain after the lambs are weaned). Valuing this gain at $1.50 per lb, that amounts to $2,073, or $230.33 in gross revenue per acre. Expenses per acre, including cash rent and forage establishment costs, were $194.84, leaving a marginal net return of $35.49/acre. For the oats that were harvested as hay, the net is a loss of $10.59/acre after mowing, raking, and baling costs are considered. These returns alone do not compare to available per acre returns from corn or soybean production in recent years; however, the oats provided better early ground cover and minimized erosion from heavy April and May rains.
Moreover, in a typical year, there was adequate remaining time to establish a summer annual forage and capture the benefits of additional lamb weight gain grazing these forages. In this particular project, those additional gains were not realized because unusually dry summer conditions prevented establishment of the summer annual, teff grass. For purposes of comparison, the investigator assumes that in a “normal” year, at least a 35-day grazing period on the teff, with similar average daily gains of 0.43 lbs/day would have been obtainable (i.e. grazing from mid-August to mid-September). This would have generated another $230.33 in revenue per acre. Since cash rent has already been charged to the grazing of oats, teff grass establishment costs are the only marginal costs, leaving $158.71 in net marginal revenue from grazing teff grass with lambs. When added to the net revenue from grazing oats, the overall net revenue from grazing lambs on two annual forage crops comes to $194.20 per acre.
Oats were successfully established and grazed. Dry matter production was measured and recorded. Lamb weight gain was monitored and recorded, and the net marginal revenue of lamb weight gain relative to the marginal cost of forage establishment was evaluated.
Teff grass was planted but was not available for grazing due to lack of rainfall. Winter wheat was planted but not available for grazing due to lack of rainfall.
Research findings were presented at the Missouri Livestock Symposium on December 7, 2013 and disseminated via outreach to other audiences as identified in the Impacts and Contributions/Outcomes section.
Impacts and Contributions/Outcomes
This project demonstrated that annual cover crops (in this case, oats) can be used successfully and economically as a nutrient source for grazing livestock (lambs). The project also showed that utilization of annual forage crops has risks and is highly weather-dependent and time-sensitive. Even though 2013 was not a severe drought year to the extent of 2012, the timing of rainfall did not favor the use of summer annuals. Spring forage growth had depleted soil moisture and not enough summer moisture was available to germinate the teff grass and provide a true test of the suitability of this relatively new (to the Midwest) forage for grazing of growing livestock.
Results of this project were presented to other farmers at the Missouri Livestock Symposium in Kirksville, Missouri on December 7, 2013. Results were also shared with 36 students enrolled in the Ethical Issues in Sustainable Agriculture class at Truman State University during the Fall 2013 semester. The investigator answered a number of questions from other producers who saw the sheep being strip-grazed from the state highway that is adjacent to the property.
The student employed as a research assistant on the project (Lizzie Evers) gained a wide array of experience in sheep handling and management, FAMACHA method of evaluating symptoms of parasitism, electric fencing systems, forage identification, measurement, and management, and a variety of other skills.
The investigator gained additional experience in measuring and monitoring forage dry matter production and utilization by livestock, through the assistance and instruction of NRCS Grasslands Conservationist Tim Clapp.
2108 US Hwy 63
Macon, MO 63552
Office Phone: 6603852616