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Evaluation of in vitro fermentation methodology to characterize the aNDFom degradation of intensively managed pasture samples.

M. Dineen

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06-23-2020

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Abstract:

T140
Evaluation of in vitro fermentation methodology to characterize the aNDFom degradation of intensively managed pasture samples.
M. Dineen*1,2, B. McCarthy2, M. E. Van Amburgh1. 1Department of Animal Science, Cornell University Ithaca, NY, 2Teagasc, Animal and Grassland Research and Innovation Centre Moorepark, Fermoy, Co. Cork, Ireland.

Numerous animal studies have shown that when forages of higher in vitro digestibility but similar NDF concentration are fed, significant increases in DMI and milk production can be achieved. In vitro NDF digestibility methods, utilizing multiple fermentation time points (30, 120 and 240 h) combined with composite decay models, have been developed to more accurately predict such outcomes. However, this methodology has not yet been fully applied to pasture-based systems. Thus, our objective was to evaluate the in vitro methodology described by Raffrenato et al. (2018, 2019) to characterize the aNDFom degradation of intensively managed pasture (IMP) samples. Forty-six samples categorized by spring, summer, autumn and drought conditions (n = 8, 22, 8, and 8, respectively) were fermented for 12, 30, 120, and 240 h, with residues subsequently analyzed for aNDFom using a 1.5-�m-pore-size glass microfiber filter. Data were analyzed in SAS, using PROC TTEST to determine differences between paired means, PROC CORR to derive Pearson correlation coefficients, and PROC GLM to analyze the effect of sample category. Results indicated that over 90% of the potentially digestible aNDFom was digested before 30 h of fermentation and that a 12-h time point combined with 30, 120, and 240 h, is likely to better describe the aNDFom degradation curve of IMP. In addition, mean undigested aNDFom at 240 h (% of NDF) was affected by IMP category (P < 0.01), whereby spring and summer were lowest (9.8% and 11.1%, respectively), autumn intermediate (15.5%), and drought highest (20.0%). The extent of in vitro aNDFom digestion was not reached before 240 h; however, a strong Pearson correlation coefficient between 120- and 240-h time points (0.98) indicated the potential to predict undigested aNDFom from the 120-h time point for this data set. Our results suggest that the in vitro methodology evaluated, combined with a 12-h time point, can be utilized to characterize the aNDFom degradation of IMP.

Keywords: pasture, neutral detergent fiber, digestibility.

Biography: Mike was raised on a pasture-based dairy farm in County Cork, Ireland. In 2014 he received his BS in Animal Science from University College Dublin. He also holds a Master of Philosophy from Queens University Belfast. In April of 2017, Mike became a ruminant nutrition scientist with Teagasc Moorepark. Currently a 5th year PhD student in the lab of Michael Van Amburgh, Mike focuses on describing nutrient supply and animal requirements in pasture-based systems along with evaluation and development of the CNCPS.