“Opportunities and Challenges in Determining Forage Digestibility Values” by Ralph Ward is available for viewing. This was an invited presentation at a symposium at the recent ADSA meeting in Montreal on forage digestibility estimates.
This presentation reviews issues related to NDF digestibility analysis and challenges that the industry faces in using and moving forward with invitro technology. Comparisons of data across several commercial laboratories are reviewed as well as studies that CVAS performed related to the best time point to use for sample evaluation and the impact of various conditions on NDF digestibility results. An abstract for the presentation is provided below.
Questions related to the presentation may be directed to Ralph at rward@foragelab.com. Information from this presentation may be quoted by permission only.
Opportunities and Challenges in Determining Forage Digestibility Values
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Ralph Ward, Cumberland Valley Analytical Services
In the last ten years, the use of NDF digestibility (NDFD) has evolved from strictly a research evaluation to a common commercially available value provided by forage laboratories. Cumberland Valley Analytical Services (CVAS) recorded requests for NDF digestibility values in excess of 820 in 2000; 13,200 in 2004; and 39,500 in 2008. Despite the wide acceptance and use of NDF digestibility values, there remain significant questions as to the appropriate use of this information for forage evaluation and nutritional modeling systems. There are no standard procedures for NDF digestibility and most systems reference a procedure by Tilley and Terry from 1963. Values generated by laboratories vary widely, and later time points have been advocated for consistency but do little more than define an asymptotic value. Reported NDFD values and associated estimates of rate are only relevant within procedures, and even then have questionable relationship to animal models. NDF digestibility values generated by a system will be dependent on drying method, grinder type and grind size, inoculum source, buffer, and type of containment system. NDF digestibility systems that generate relevant values will 1) exhibit consistency over time, 2) will generate repeatability within run, 3) will be sensitive to define differences between forages, 4) and will be robust across commercial laboratory settings. These objectives are critical to a laboratory providing information of value and are necessary points to be understood by users of this information. NDF digestibility system function at CVAS across runs, within run, and across species will be shown. Internal NDF digestibility quality control samples for 06/01/2008 through 12/30/2008 were: 12 hour NDFD = 24.5%, SD = 1.98, n = 112; 24 hour NDFD = 48.6%, SD = 1.45, n = 340; 30 hour NDFD = 52.6%, SD = 1.64, n = 1018. Associated nutritional relationships with NDF digestibility will be developed.