Browsing by Author "Steven P. Washburn, Committee Chair"

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    Continuous Culture Fermentation of Wild-Type Endophyte-Infected, Endophyte-Free, and Non-Toxic Endophyte-Infected (MaxQ[TM]) Tall Fescue Supplemented at Four Energy Levels
    (2003-11-24) Vibart, Ronaldo Eduardo; Steven P. Washburn, Committee Chair
    Eight dual-flow continuous culture vessels (700 ml) were used to compare in vitro effects of wild-type, endophyte-infected (E+), endophyte-free (E-), and non-toxic, endophyte-infected (EN) (MaxQ™) Jessup tall fescue on ruminal fermentation in a grazing simulation at four levels of concentrate supplementation (ground corn). For each of the fescues (E+, E-, and EN), forage to concentrate ratios of 100:0, 85:15, 70:30, and 55:45 were used for a total of 12 experimental diets in a randomized incomplete block design with two replicates. Vegetative grasses were used with compositions as follows: E+ (12.3 % CP, 59.9 % NDF, 29.2 % ADF); E- (13.4 % CP, 60.7 % NDF, 29.4 % ADF); and EN (10.4 % CP, 63.2 % NDF, 31.4 % ADF). Ruminal cultures were adapted for 48 h before experimental diets were fed and then gradually adjusted to the final diets. Each culture vessel was offered a total of 15 g of DM per day including four equal portions of grass (fed at 0300, 0900, 1500, and 2100 h); and two equal portions of corn (fed at 0900 and 2100 h). Ruminal fluid passage rate was set at 6.25% per h. Headspace gas and liquid samples were analyzed for methane (CH4), ruminal culture pH, volatile fatty acids (VFA), and ammonia N (NH3 N) production to assess the ruminal environment from the pasture-based diets. Forages had no effect on molar proportion or total VFA production (58.8 mmoles/d). Methane production (24.7 mmoles/d) and ruminal culture pH (6.11) also remained unaffected by forages. Ammonia N output (g/d) varied by grass: EN had lower (P < 0.05) values compared to those of E+ and E-. Increasing the level of grain linearly decreased (P < 0.05) ruminal culture pH, ammonia N, acetate production, and the acetate to propionate ratio, whereas propionate and butyrate production increased (P < 0.1) with higher grain supplementation. Overall, ruminal fermentation was minimally altered by the presence or absence of the endophyte. However, forage by grain interactions for methane and ammonia N production were reported. The grain-induced culture pH drop for the highest level of grain (45%) changed the methane production pattern for all three grasses. At that supplementation level, EN was the most energetically efficient forage.
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    Effects of Milk Feeding Period and Anthelmintic Treatment on Fecal Egg Counts and Growth in Pastured Dairy Steers
    (2005-07-27) Thompson, Bianca Merrick; Brinton A. Hopkins, Committee Member; Steven P. Washburn, Committee Chair; Jean Marie Luginbuhl, Committee Member
    A 2 x 2 factorial trial with 2 phases was conducted to evaluate the effects of weaning age (6 wk vs 12 wk) and anthelmintic treatment (non vs dewormed) on average daily weight gain (ADG) in 36 Holstein and Jersey X Holstein crossbred steers born in fall (Oct - Nov) and winter (Dec — Feb) 2003 — 2004. Steers were blocked into 4 treatment groups by birth weight and breed. Calves of similar age were managed together in pastures regardless of treatment and group-fed 3.8 to 7.6 L of whole milk/d until weaning. Phase 1 extended from birth until July 15, 2004. Phase 2 started on July 15 and ended on Nov 18, 2004. Dewormed calves received 1 mL ivermectin pour-on formulation/ 10 kg body weight (BW) at 12 and 20 wk of age, and again on July 15 and Sept 23. Fecal samples and BW (birth to Nov 18, 2004) were taken from each calf at 4-wk intervals. Fecal egg counts (FEC), BW, and ADG (during Phase 1, Phase 2, and Phases 1 & 2 combined) were compared among deworm, wean age, % Holstein, birth season, and their interactions. Parasite eggs were not detected until April and were lower in dewormed calves after July and Sept treatments. Fall-born calves usually had lower FEC than winter-born calves. Gains during Phase 1 were higher for fall-born calves. In Phase 2, dewormed calves actually had faster ADG than non-dewormed calves. Gain across Phase 1 and Phase 2 were higher in fall-born calves and tended to be higher in calves weaned at 6 wk. Gains and BW generally were higher with increasing % Holstein. Although steers that were not dewormed had higher FEC and differing ADG during parts of the trial, their overall performance was similar to those that received 4 doses of ivermectin.