Continuous Culture Fermentation of Wild-Type Endophyte-Infected, Endophyte-Free, and Non-Toxic Endophyte-Infected (MaxQ[TM]) Tall Fescue Supplemented at Four Energy Levels

No Thumbnail Available

Date

2003-11-24

Journal Title

Series/Report No.

Journal ISSN

Volume Title

Publisher

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), 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.

Description

Keywords

tall fescue, continuous culture, Endophyte status

Citation

Degree

MS

Discipline

Animal Science

Collections