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Evaluation of eastern gamagrass using the beef N.R.C. model

by Meredith, Alisa Kaye

Abstract (Summary)
Currently there are no model inputs for eastern gamagrass [Tripsacum dactyloides

(L.) L] for use in the National Research Council's (NRC) beef cattle model. This study

was conducted to determine model inputs for two eastern gamagrass varieties for use

with the forage database of the NRC model. Cattle producers in the Midwestern US will

be able to evaluate eastern gamagrass in a forage system and estimate net energy for

maintenance (NEm), metabolizable protein (MP), and degradable intake protein (DIP)

balance for various production scenarios. Eastern gamagrass varieties 'Iuka' and 'Pete'

were arranged in a split-plot randomized complete block experiment with four

replications. Varieties were whole plots with harvest maturities as split plots. Plant

tissue was harvested from both varieties at four maturities: vegetative/early elongation,

anthesis, seed shattering and dormancy. Various compositional attributes were

determined on forage samples to enable the determination of model inputs for predicting

energy and protein balances. A slight difference between varieties was found for crude

protein concentration (p<0.05). Differences (p<0.05) due to maturity were found for all

analyses used in the model, corroborating the decline in nutritive value of eastern

gamagrass with advancing maturity. Neutral detergent fiber (NDF) ranged from 593 g

kg-1 at the vegetative/early elongation stage of maturity to 731 g kg-1 at dormancy.

Assumed animal and environmental inputs were used for beef cattle at two stages: nonlactating

160 d prepartum and 60 d peak lactation. Energy and protein balance were

estimated using level I of the model. The vegetative/early elongation stage of

development supplied the greatest amount of MP. Digestible intake protein declined as

plant tissue matured. All but the vegetative/early elongation stage of maturity were

limited in DIP for cows in both stages of production. Soybean meal was used as a protein

supplement in amounts ranging from 0.8 kg to 1.4 kg to meet nutritional demands of

cattle grazing eastern gamagrass at anthesis, seed shattering and dormancy. In the

simulations conducted, eastern gamagrass would be an acceptable forage source for beef

cattle provided that appropriate protein supplementation was given when the forage was

at more advanced stages of maturity.

Bibliographical Information:

Advisor:

School:Kansas State University

School Location:USA - Kansas

Source Type:Master's Thesis

Keywords:nrc beef model eastern gamagrass tripsacum dactyloides nutrient requirements for cattle agriculture agronomy 0285 animal culture and nutrition 0475

ISBN:

Date of Publication:01/01/2008

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