Smut Grass Grazing

August, 2019
 Aaron Stam, UF/IFAS Extension Seminole Tribe of Florida, Brighton

Grazing smut grass may not be ideal for every ranch in the state of Florida, but for some ranchers, smut grass has become valuable forage. The Seminole Tribe of Florida has many ranches where smut grass has taken over as the dominant plant in pastures. In these pastures numerous attempts were made to eradicate the smut grass, but ultimately the smut grass returned. After witnessing large calves weaned on a primarily smut grass diet, we decided to take a further look into smut grass.

The first thing we did was to list out our options for reducing or removing smut grass. There were five basic strategies identified for dealing with smut grass. Herbicide, roller/choppers, burning, mowing and intensively grazing were the strategies we saw were most effective. Our initial inclination was to set up some field trials revolving around grazing practices, as those would be the easiest to implement without a large budget. We began a field trial on the Big Cypress reservation that looked at two pastures. Each pasture would have a control group where no fertilizer was applied. Each pasture would also have a section where a complete, slow release dry fertilizer was applied, and a third section where only liquid nitrogen was applied. We set out multiple exclusion cages on each of the sections and measured 14, 21, 28 and 42 day old growth of the smut grass. Our results were as follows:  Pasture 1’s liquid Nitrogen only section averaged 13.8 percent crude protein (CP), and a total digestible nutrients (TDN) of 54.4 percent. The dry fertilizer (20-0-10) had a CP average of 14.5 percent and a TDN of 57.3 percent. The control section of pasture #1, averaged CP at 11.9 percent and a TDN of 56 percent.

The same steps were followed on a second pasture. The results were liquid N only averaged 18.1 percent CP and TDN of 56.3percent. The dry fertilizer (20-0-10) had a CP of 17.8 percent and TDN of 58.4 percent. The control section had a CP of 14.4 percent and TDN of 57.5 percent.

We were somewhat surprised by the extremely high protein and TDN levels in the smut grass and decided to begin a field trial that would look at the capacity of smut grass as forage. Knowing smut grass grows quickly, we decided to increase the stocking rate of the pasture to 2 cows per acre in hopes of capitalizing on competitive rotational grazing. That is, cows when placed in a pasture where there is heavier grazing pressure will be less selective of what they eat, while increasing the amount of forage consumed.

 The Seminole Tribe of Florida Inc. allowed 39 of their heifers to be placed onto a 20 acre paddock, now known as Pasture X. Pasture X was almost entirely covered with smut grass. Our estimates were the pasture was 80-100 percent covered in smut grass. This paddock was cross fenced into four sections. Each section was approximately five acres. These heifers were rotated from paddock to paddock every seven days. Each time they were rotated, they were rotated into 21 day old smut grass, as we had mowed each paddock 21 days prior to initial grazing. The heifer body condition scores were averaged at 3.9 as they were turned into Pasture X in September of 2017. The cattle were pregnancy checked on 5/21/18. At this point there were the 39 original heifers, plus one that had jumped the fence and joined the pasture X herd. Of those 40, two year old heifers, 37 of them were confirmed bred. Their average body condition score (BCS) was 5.5-6.0. Of the three not bred, 2 were called immature reproductive tracts by the vet, the third had stage two Ovarian Follicular Dysplasia. All three of the open heifers had a BCS of 5.5.

The first calf was born October 11, 2018. 78 percent of the calves were on the ground in the first 32 days (by November 14th). In total there were 35 calves born, 1 heifer died giving birth (calf died too) and two calves were born sickly and died on the ground. There was no unexplained death loss in the herd.  The calves were weaned early, February 20 as cow’s BCS were between 3.5-4.0.

The same cattle stayed in Pasture X over the next year. 2 Super American bulls were utilized for the 2019 breeding season. The breeding season was 90 days.  The cattle were pregnancy checked on 6/5/2019 and had a conception rate of 95 percent. This concluded Pasture X’s first field trial on Completive Rotational Grazing and smut grass grazing.

I would be happy to share more detailed economic data with anyone interested, but here are some of the dollar values associated with Pasture X’s first field trial. (Veterinary expense, mowing, fertilization, feed, molasses and minerals, day work labor and administrative.)

2018 total heifer costs- $13,363.54, bull costs- $3049.72, total cost $17,850.67, total cost per head $469.75.

2018 total $ per weaned calf- $510.02, total expense per exposed female $457.71. Total pounds of beef raised per acre 357.3.

2019 Costs per cow- $15,621.10, bull costs- $2152.62, Total cost- $18211.28, total cost per head $479.24. Total cost per exposed female-$$479.24

In cooperation with the Seminole Tribe we have started the second field trial of Pasture X and competitive rotational grazing on smut grass. Currently there are 78, approximately 550 pound heifers being developed on the 20 acre parcel. The 78 heifers are following the same 7 day rotational strategy and are moved into one of the five acre paddocks every seven day. Currently, the smut grass is producing enough forage for all 78 head. The heifers will be weighed at 90 or 120 days to check their average daily gain on smut grass.

Final thoughts- The competitive rotational grazing has greatly reduced the amount of smut grass in the pastures. The stocking rate of 2 animals per acre for 2018 and current rate of 3.9 animals per acre has allowed for much of the smut grass to be eaten, and has allowed air, sunlight and water to grasses that had been shaded out by the smut grass canopy. We have seen bahia, common Bermuda, and white clover making a comeback into Pasture X.

 

If you have any questions about this article, please contact Aaron Stam at astam@ufl.edu.

 

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