Date of Graduation

12-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Ken Coffey

Committee Member

Shane Gadberry

Second Committee Member

Charles Rosenkrans

Third Committee Member

Wayne Coblentz

Fourth Committee Member

Donald Johnson

Fifth Committee Member

Dirk Philipp

Keywords

Animal Productivity, Animal Nutrition, Forage Quality, Plant-Animal-Soil Relationship, Production, Responses, Ruminant

Abstract

In experiment 1, 80 steers (197.0 kg initial body weight; BW for fall, 116.9 kg for spring), were stocked at 2.45 and 4.1 calves/ha in fall and spring, respectively in 16 tall fescue pastures [fall ergovaline (EV) = 1,475 ppb and spring EV = 1,173 ppb] under 2 treatments, mineral (MIN) (n = 8) and cumulative management (CM) (n = 8). Forage allowance did not differ (P = 0.76) between CM and MIN during fall but differed during spring (P ≤ 0.05, 2.55 vs. 3.22 kg DM/kg BW, for MIN and CM, respectively). For fall, average daily gain (ADG) resulted in 0.41 × EV for MIN and 1.05 × EV for CM. For spring, ADG resulted in 0.80 × EV for MIN and 0.94 EV for CM resulting in an increase of ADG for CM as the level of EV increased. In experiment 2, steers (n = 3) were fitted with a device (Icetag; IceRobotics) strapped to left metatarsus that measured motion activity while on varying levels of EV toxicity. Initial lying bouts for CM were 18.4 but decreased by 0.9 bouts for every 1,000 ppb EV increase. Period 2 resulted in standing time for MIN calves of 858.01 min/day (14.3 h/d) whereas CM calves spent 792.01 min/day (13.2 h/d) standing and CM calves took 20% more steps daily than MIN calves. For every 1,000 ppb increase in EV, steps decreased by 275. In experiment 3, calves (n = 4) grazed long sward regrowth (LSR) or short sward regrowth (SSR) tall fescue and alfalfa paddocks for forage quality, visual observations, rumen volatile fatty acids and diet selectivity measurements. No differences in these behavior measurements were observed for either forage (P < 0.05). Within fescue paddocks, ruminal ammonia, total volatile fatty acids (VFA), acetate, and the branch-chain VFA were greater from SSR vs. LSR (P < 0.05), but these differences were not observed (P ≥ 0.11) on alfalfa paddocks. In summary, the effect of combined management strategies offers potential to cope with toxicity in tall fescue pastures. Grazing activities of cattle grazing tall fescue or alfalfa may influence intake, but further research is needed to determine these behavioral modifications when differences in sward height are small.

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