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Animal Science Departmental Report 2004-2005 Return to Dairy Cattle articles
Varying
Endophyte Status and Energy Supplementation of Fresh Tall Fescue in Continuous
Culture R. E. Vibart, S. P. Washburn, V. Fellner, M. H. Poore, J.
T. Green, Jr.1 and C. Brownie2 1Department of Crop Science, and 2Department
of Statistics, North Carolina State University Abstract 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, Table 1), 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, Tables 2 and 3).
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.
Methane
production (24.7 mmoles/d) and ruminal culture pH (6.11) 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- (Table 4). Forages had no effect on molar proportion or total VFA
production (58.8 mmoles/d, Table 5).
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 (Table 6 and 7). 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.
Key
words: continuous culture, endophyte, tall fescue, grain
supplementation.
Abbreviation key: E+ = endophyte-infected
tall fescue, E- = endophyte-free
tall fescue, EN = non-toxic,
non-ergot alkaloid-producing, endophyte-infected tall fescue.
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