Author ORCID Identifier:

https://orcid.org/0009-0007-5308-6871

Date of Graduation

7-2026

Document Type

Thesis

Degree Name

Master of Science in Animal Science (MS)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Coffey, Kenneth

Committee Member

Nieman, Christine

Second Committee Member

Kegley, Elizabeth

Third Committee Member

Popp, Michael

Keywords

Arkansas; Forage Systems; Ruminant Nutrition; Sheep; Stocker Cattle

Abstract

Stocker cattle producers in the southeastern part of the U.S. heavily depend on traditional forages such as bermudagrass [Cynodon dactylon] pastures during the warm season for grazing. Summer annual forages offer stocker cattle operations a valuable alternative source of forage. These forages have high yield potential and can help extend the grazing season. This is particularly beneficial during the summer months when traditional forage sources may be limited. Warm-season annual grasses may experience a decrease in crude protein concentrations during late summer and early fall. As a result, it may be necessary to find alternative sources of crude protein or consider intercropping with a legume species. This is important to ensure that livestock receive the necessary nutrition throughout the growing season. The first objective was to improve forage nutritive value and animal performance by intercropping sorghum × sudangrass and sorghum × sudangrass and cowpea into killed mixed bermudagrass pastures during 2021 and 2022. Crossbred steers were utilized (n = 72; 305 ± 2.8 kg initial BW) in 2021 and (n =72; 273 ± 2.9 kg initial BW) in 2022. Treatments were common bermudagrass (BG), sorghum × sudangrass (SS), and sorghum × sudangrass mixed with cowpeas (SSCW). Each of the 9 pastures was 2.27 ha. Each pasture was subdivided into four paddocks equal in area for rotational grazing. Sorghum × sudangrass pre-grazing biomass was greater (P < 0.01) than both BG and SSCW in both years and had greater (P < 0.01) yields in 2022. Bermudagrass NDF concentrations were greater (P < 0.01) than SS but did not differ from SSCW and were greater (P < 0.01) in 2021 than in 2022. There was a tendency for 2022 CP concentrations to be greater (P < 0.078) than in 2021. Steers in 2021 had greater (P < 0.01) initial and average BW compared to steers in 2022. Steers tended to have greater (P < 0.083) ADG in 2022 than steers in 2021. Sorghum-sudangrass in 2022 produced greater (P < 0.01) ADG than BG in 2021 but did not differ among other species in both 2021 and 2022. Gain per hectare in 2022 was greater (P < 0.01) than those in 2021. Bermudagrass had a greater (P < 0.01) number of grazing days than both SS and SSCW, and average grazing days were greater (P < 0.01) in 2022 than in 2021. Sorghum × sudangrass and SSCW stocking rate (SR) and average BW among pastures were greater (P < 0.01) than BG but did not differ from each other and pastures in 2021 had greater (P < 0.01) SR and average BW than those in 2022. Sorghum × sudangrass had greater (P < 0.01) forage allowance (FA) than both SSCW and BG, and FA was greater (P < 0.01) in 2022 than in 2021. Tall fescue [Schedonorus arundinaceus (Shreb.)], infected with the endophyte Neotyphodium coenophialum, is known to produce ergot alkaloids. These alkaloids are natural compounds that can have detrimental effects on livestock that graze on the contaminated grass. The isoflavones in red clover extract could potentially help with symptoms of fescue toxicosis by vasodilation of arteries allowing increased blood flow to the animal. The second objective of this thesis was to improve health and digestion by lambs offered endophyte-infected tall fescue seed by the addition of red clover extract into the diet to help vasodilate arteries by the isoflavones. Non-toxic tall fescue (E-) or toxic endophyte-infected (E+) tall fescue seed was obtained and mixed as part of the diet in a tumble mixer. Wether and non-pregnant ewe lambs (n = 30 ± 0.97 kg initial BW) of predominately Dorper breeding were housed in individual 1 × 1.5 m pens with metal grate flooring within an enclosed building with 14-h of light and 10-h of darkness daily and the temperature was maintained 26 to 29 °C. Lambs were removed from pens for 3-h for an exercise period after a 14-day feed adaptation period. During the exercise period, pens were cleaned thoroughly before the 7-day total collection period. Following period 1, lambs were removed from their pens and placed on bermudagrass and crabgrass mixed pastures for 30 days to allow the toxicity to subside. Period two utilized two lambs from the first period and the remainder were from a new group. During periods 1 and 3, all lambs were offered a common diet of bermudagrass hay along with endophyte free tall fescue seed (E-0) for a 14-d adaptation period followed by 5 d of total fecal and urine collection and periods 2 and 4 consisted of a 14-d adaption period followed by 7-d of total fecal and urine collection. During periods 2 and 4, diets consisted of four treatments: E- with no RCE (E-0), or E+ with no RCE (E+0), 3.3 g/kg RCE (E+33), 6.7 g/kg RCE (E+67), or 10.0 g/kg RCE (E+100) of the diet DM. A treatment × time interaction was found for dry matter (DM), OM, NDF, and ADF intake, E-0 being greater (P < 0.01) than all other treatments when expressed as both (g/day) and per unit of BW (g/kg BW). Dry matter digestibility (DMD, g/kg DMI), OM digestibility (OMD, g/kg OMI), NDF digestibility (NDFD, g/kg NDFI), ADF digestibility (ADFD, g/kg ADFI), and hemicellulose digestibility (HEMID, g/kg Hemi Intake) did not differ (P ≥ 0.14) among treatments. A treatment × time interaction was found for digestible DMI (DDMI) and OMI (DOMI) with E-0 being greater (P < 0.01) than all other treatments. Serum prolactin concentrations were greater (P < 0.01) from lambs offered E-0 versus all other treatments. A treatment × time interaction was found for N intake, apparent N absorption (g/day) and N retained (g/day) with E-0 being greater (P < 0.01) than all other treatments. Rectal temperature and UUN did not differ (P > 0.10) among treatments.

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