Winter Grazing: Annual Forages Improve Lamb Growth and Health Parameters

Dr. Brady Campbell, Assistant Professor, State Small Ruminant Extension Specialist

Fall is for harvest. Whether directly involved in production agriculture or a consumer of its products, most associate this time of year with combines harvesting soybeans and corn in the field or farm stands filled with pumpkins and apple cider. However, for livestock producers and especially those raising ruminants, harvest looks a bit different. This time period is the final push for grazing corn fodder/stubble, stockpiled forages, or annuals planted in the late summer before environmental conditions force producers off of pasture and into the barn or drylot to feed grain and hay. For those that planned ahead, well done! Each of these options provide high quality feedstuffs that are self harvested by the animal, resulting in a cheaper feed source. For those that weren’t able to sacrifice the land or weren’t prepared for planting, no worries, there is always next year.

Some of you may be thinking, what forages would provide enough nutritional quality to get me through the year? For those that were able

to attend the 2021 Ohio Sheep Day or read the event recap a few weeks ago, a series of spring, summer, and winter annual forages were planted and on display to demonstrate the growth potential and nutritional parameters available for grazing livestock this fall and winter. I’m sure that others are also hesitant about how long forage quality will last as colder temperatures begin to set in and if animal maintenance and growth can be sustained throughout the fall and winter months on forage alone. As a part of my recently completed Ph.D., these were questions that I proposed as we investigated the sustainability of grass-fed lamb in the eastern United States. The results from our first published manuscript help address some of these comments and is summarized below.

For this experiment, a total of 54 September-born Dorset and Suffolk x Dorset crossbred lambs were grazed for a total of 56 days from November 5th to December 31 in 2019 at the Eastern Agricultural Research Station in Belle Valley, Ohio. Lambs were placed in one of three forage treatment groups: control (stockpiled pasture – primarily tall fescue), oats (bin run/feed grade), and purple top turnips (just like those that you would plant in your garden) mixed with cereal rye. The cereal rye was added to the mixture as pure swards of brassicas are low in fiber. However, due to dry condition during planting, the cereal rye failed to germinate resulting in a pure sward of turnips.

(Figure 1. Average daily precipitation and temperature summary)

In terms of lamb growth, lambs grazing turnips had the greatest weight at the conclusion of the 56 day grazing period (66 lbs.) when compared with lambs grazing oat and stockpiled pasture (55 lbs. and 57 lbs., respectively). As a result, lambs grazing turnips had the greatest average daily gain (ADG) over the course of the 56 day grazing period gaining 0.24 lbs./day whereas lambs grazing stockpiled pasture and oats had the lowest ADG of 0.07 and 0.03 lbs./day, respectively. Reduced growth rates for lambs grazing on oat pastures was unexpected as the literature supports that small grain forages are generally rich in protein and energy. Our data evaluating quality parameters supports this notion as crude protein (CP) values at the beginning of the experiment for oats was 22% whereas turnips were 15%. By the end of the grazing period, these values flip flopped with oats having a CP of 15% and turnips at 21%. Moreover, in mapping out the the average daily temperature report, the data highlighted in Figure 1 shows that there were three instances in which the temperature dipped below -2°C (28°F). This value is significant as oats will experience winter kill and rapid deterioration of forage quality in temperatures less than 28°F. Interestingly, brassicas such as turnips, are more cold tolerant and are able to withstand temperatures up to -6°C (21°F). According to Figure 1, daily average temperatures did not drop below -5.5°C (22°F) and therefore had little affect on the overall quality of the turnips.

For lamb health, the parameters of FAMACHA© eye score, packed cell volume (PCV), fecal egg count (FEC), and total plasma protein were collected. There were no differences in lamb FAMACHA© eye score, packed cell volume (PCV), and total plasma protein. There was a difference in lamb FEC as lambs grazing oats had a lesser parasite burden at the conclusion of the grazing period when compared with lambs grazing turnips and stockpiled pasture. However, these data must be interpreted cautiously. Per study design, the grazing period was during the winter months when parasite burdens are known to be reduced. Data from this experiment report that FEC were never greater than 102 eggs/gram (EPG) of feces – a value in which is almost considered undetectable. Furthermore, due to the deterioration in forage quality in oat pastures, lambs grazing oats had a greater amount of refusal as much of the fibrous stalks remained in the pasture when compared with lambs grazing stockpiled pasture and turnips. THis is primarily attributed to fiber value of oats increasing from 23% to 41% for acid detergent fiber (ADF) and from 43% to 60% for neutral detergent fiber (NDF).

Overall, this paper supports that fall-born lambs can be maintained and grown on annual forages during the months of November and December in Ohio. Additionally, grazing during the winter months greatly reduces parasite burdens in areas known to have a high parasite burden. However, environmental conditions may limit the use of this strategy depending upon geographical location and intended market of the animals being fed. In temperatures above freezing, annual forages serve as a viable alternative in grazing systems. Further research is needed in order to understand the benefits of grazing annual forages in the fall and winter with the mature ewe flock.


Campbell, B.J., Gelley, C.H., McCutcheon, J.S., Fluharty, F.L., Parker, A.J. 2021. A comparison of annual forages and stockpiled pasture on the growth and health parameters of grazing fall-born lambs. Small Rum. Res. 196: 106335.