This Is AuburnElectronic Theses and Dissertations

Improving Forage Systems Viability for Beef Cow-Calf Pairs in the Southeast US




Mason, Katie

Type of Degree

PhD Dissertation


Animal Sciences


Improvement of grazing and nutritional management strategies in warm-season perennial forage systems in the Southeast US can lead to more efficient and sustainable cattle operations. Extending the grazing season, improving forage nutritive value, and reducing labor and feed costs during the winter months are two ways to achieve this goal. Alfalfa (Medicago sativa L.) can be interseeded into bermudagrass [[Cynodon dactylon (L.) Pers.].] to increase forage mass and quality and extend the grazing season. A 2-yr study was conducted in Shorter, AL to evaluate effects of harvest intensity and harvest frequency of alfalfa-bermudagrass mixtures on dry matter (DM) forage mass, nutritive value, canopy cover, botanical composition, and alfalfa persistence. Harvest height treatments included 5-, 10-, and 15-cm and harvest frequency treatments included 2-, 4-, and 6-wk intervals. Four blocks of 9 plots (1.5 × 4.5 m) were arranged in a randomized complete block design. In Yr 1, plots were harvested at assigned harvest intervals beginning Jun 11 and ending Sep 4, 2018, and in Yr 2 from Jun 4 to Oct 10, 2019. Seasonal forage mass was greatest at the 5-cm harvest height, intermediate at 10 cm, and least at 15 cm (P < 0.0001). Four and 6-wk harvest frequencies resulted in greater DM forage mass than 2 wk (P = 0.0113). Crude protein concentration was maximized at the 4-wk clipping interval (P = 0.0003). As harvest height increased, in vitro true dry matter digestibility (IVTDMD) increased (P < 0.0001). Alfalfa persistence was maximized at 5- and 10-cm clipping heights and 4- and 6-wk harvest intervals, which correlated with greater plant densities within those treatments. Results indicate that harvesting alfalfa-bermudagrass mixtures at a 10-cm height and 4-wk interval provided optimal forage mass and quality, while ensuring persistence of alfalfa. A forage mass estimation equation was developed using canopy height and stand variability measurements. However, a large amount of variation was observed in the dataset depending on alfalfa contribution levels, resulting in inaccurate forage mass predictions. In another 2-yr study, reduced-labor winter nutrition management systems were evaluated in Shorter, AL. Reduced-labor feeding systems may lower input costs during winter months in the Southeast US, when feed costs are typically high. Diet treatments included (i) rotational grazing of winter-annual mixture of oat (Avena sativa L.), ryegrass (Lolium multiflorum Lam.), and crimson clover (Trifolium incarnatum L.;RG); (ii) free-choice whole cottonseed + bermudagrass hay (FC); and (iii) 50:50 soyhull/corn gluten feed pellets fed every other day at 1% body weight (BW) + bermudagrass hay (RF). Objectives of this study were to evaluate the effects of diet on cow and calf performance under reduced-labor feeding systems. Three commercial cow-calf pairs were placed into 2-ha pens, with 3 pens per treatment, in a completely randomized design. Cattle on RG were rotated every 14 d. Greater percentages of CP and IVTDMD were observed in the RG system (P < 0.0001 and P < 0.0001, respectively) than other diets. Cow BW and average daily gain (ADG) were greater (P < 0.0001 and P = 0.0014) for RG than FC and RF, and calf ADG was not different among treatments (P = 0.0706). All systems provided viable reduced-labor options compared with daily feeding without negatively impacting animal performance.