Progress 10/01/08 to 09/30/11
Outputs
OUTPUTS: Neutral detergent fiber (NDF) has been characterized the same way for about 40 years, with few modifications. Data existed that suggested NDF could be redescribed into multiple fractions based on rate of digestion and the size of the fraction. Some of the fractions are related to cross-linking of carbohydrate and lignin due to water, heat and light effects. Several long-term in vitro digestion studies using rumen fluid, buffer and forage samples (0.5g) were conducted to evaluate the rate and extent of NDF digestibility from 0 to 240 hours. All of the NDF residues were corrected for ash contamination. The major finding of the work was the identification of the dynamic nature of the indigestible neutral detergent fiber fraction (iNDF). In the work of Chandler and Van Soest, the value of the indigestible fraction was thought to be related to a constant factor, 2.4 * lignin/NDF and that was how it was implemented in our nutrition model. We determined that only one feed or forage approached that value as a near constant and that was alfalfa. For all other forages, we learned that the iNDF was dynamic and varied by forage, forage maturity and the agronomic conditions the forage was grown in (heat, light, and water stress). The outcome is that iNDF ranges from 2 to 8 times the lignin content and is variable by growing season and cutting. To determine this value, an in vitro NDF digestibility needs to be conducted for 240 hours. Although that seems prohibitive, commercial laboratories are conducting the appropriate assay in adequate numbers to then develop NIR equations to predict the outcome. This will allow the method to become a routine input in the model and for ration evaluation. This means that over time laboratories could abandon the lignin assay since the only purpose in most nutrition models was to use it to predict indigestibility. Also, a model was developed to predict the rate of digestion of three separate digestible fractions of neutral detergent fiber and also to estimate the the size of the fractions. The model was developed in Vensim (Ventana Systems) and uses an Excel interface. The model relies on at least four inputs, NDF digestion at 0, 30, 120 and 240 hr in vitro digestion. The model uses a goal seeking approach and fits the disappearance of NDF and calculates three fractions and the associated rates of disappearance for the fast, the slow and the undigested fraction. For example, overall rates of digestion of corn silage range from 2% to 7% whereas using the multiple pool system, rates of the fast pool can range from 5 to 14% and comprise from 40 to 70% of the total NDF, and the slow fraction can comprise 10 to 40% of the NDF with a disappearance rate of 0.8 to 1.4%. These differences in fraction sizes and rates have implications for feeding behavior of the NDF and understanding these differences will help nutritionist make better forage allocation decisions. PARTICIPANTS: The primary person contributing to the work on this project was Emiliano Raffrenato, a Ph.D. student working in forage digestibility and neutral detergent fiber (NDF) digestion with me. Dr. Raffrenato conducted much work to understand the extent of NDF digestion and determined that samples needed to be fermented to at least 240 hours to understand the extent of digestion. Other methods were re-visited by Dr. Raffrenato, for example the lignin assay the the filtration steps associated with adequate recovery needed updating and a manuscript was published describing this work. Further, Emilinao worked on a mathematical model that describes the rate of digestion of NDF of three separate fractions of NDF and also the size of the respective pools. So he was able to redefine how we view NDF and provided the basis and tools for future users to understand how to better calculate and allocate forages to the appropriate groups of cattle. TARGET AUDIENCES: The target audience for this work are anyone that feeds dairy cattle in systematic manner. This includes nutritionists and dairy producers. The work was very method driven, so it's actual application is just starting and commercial laboratories are starting to develop data sets using the approach developed from this work. We expect many dairy producers in the Northeastern U.S. will begin to evaluate their feeding systems based on this data. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The outcome of this work was the recognition that the digestible neutral detergent fiber of any forage was not directly related to the lignin content or the relationship between lignin and neutral detergent fiber, but to the agronomic conditions the plant is grown under, such as light, heat and water availability or stress. We now know that as the plant experiences differences in agronomic conditions, this relationship changes significantly, especially in grass based forages, and is very dynamic with an observed range of 2 to 8. This has significant implications for how nutritionists formulate diets for cattle and how much a particular forage a cow will consume. This also has implications for plant breeders that are attempting to differentiate genetic from agronomic or phenotypic differences in digestibility. At this time plant breeders use a static value measurement to evaluate forages. An in vitro NDF digestibility of 30 hr or 48 hr is used to compare forage digestibility. This new approach provides more complete data by providing differences in the extent of digestion (240 hr NDF digestibility) and also by partitioning the NDF into the various fractions that more closely represent the dry matter intake potential of forages. The model is currently being used by a large commercial forage laboratory in Maryland and also in research projects being conducted by corn breeding and forage companies. The corn breeder is learning that the agronomic effects of heat, light and water are not consistent among hybrids and that has implications for hybrid selection by region. Application of this will allow producers to make better corn silage hybrid selections to fit the growing conditions of their region. Further, the model will eventually be used in the Cornell Net Carbohydrate and Protein System, and will help nutritionists better develop diets for dairy and beef cows that contain greater levels of forage, thus reducing purchased feed costs. For example, this approach should allow producers to increase forage utilization in diets by at least 10-15% which means moving herds from 50 to 56% forage or from 60 to 67% forage depending on their starting point. Increasing forage by these levels would reduce feed costs by over $0.20 per cow per day at current feed prices.
Publications
- Raffrenato, E. and M. E. Van Amburgh. 2011. Technical Note: Improved methodology for analyses of acid detergent fiber and acid detergent lignin. J. Dairy Science. 94:3613-3617.
- Raffrenato, E. C.N. Nicholson, and M. E. Van Amburgh. 2011. A mathematical approach to predict the size and rate of digestion of a fast and slow pool and the indigestible NDF. J. Dairy Sci. 94:E suppl. 1:455. (abstr.)
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: The data generated from this work has been discussed at several meetings in the United States, Europe, South Africa and Australia. Our findings on neutral detergent digestibility (NDF) and the heterogenous behavior of NDF have significant implications for how fiberous feeds are utilized, especially in high performance systems wanting to include a high level of forage. At this time a description of our findings has been shared with nutritionists, dairy producers and academics at several meetings in the Northeast and U.S. A field usable model has been developed that will allow all commercial feed analyses laboratories to calculated the rate and potential extent of NDF digestibility along with describe the size of the pools of NDF that exist in the forage or feed. This will allow anyone submitting a sample for analyses to utilize this information and this will make our findings a routine part of the chemical characterization of forages in the U.S. In addition, this model will be incorporated into our Cornell Net Carbohydrate and Protein System Nutrition Model that is used around the world and this will provide a broad platform for implementation of this data. PARTICIPANTS: The primary individual working on the project was Emiliano Raffrenato. Emiliano is working on his Ph.D. degree and is focused on forage and fiber digestibility, feed chemistry and model development. He will be finishing his degree and publishing several papers from this work over the next year. The PI spends a significant amount of time working on this project and we have partnered with several scientists at the Miner Institute in Chazy, NY to help conduct some of the more basic chemistry involved in our understanding of linkages between lignin and cellulose and hemi-cellulose in the plant. TARGET AUDIENCES: Our target audience is nutritionists and academics involved in the animal nutrition fields. Our data along with the model should help them understand our findings and learn how to implement them in an efficient and effective manner. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
What we found is that agronomic factors that affect forage digestibility can do it independent of the chemical composition of the plant through cross-linking between lignin and cellulose. This greatly affects digestibility independent of the lignin content of the plant and further, we determined that we can partition the NDF into three pools that will vary in size based on the plant genetics and conditions under which is was grown. Thus, the pool size is dynamic and the greater the amount of NDF in the fastest digesting pool, the greater the dry matter intake capacity of the animal. Integrating this information into a model has allowed us to further predict the feeding behavior of a particular forage within a herd. We have known for years that NDF limited feed intake in ruminants, but did not have a good model to account for all of the variation. This model is not completed yet, but the ability to predict rates and pool sizes in a more dynamic manner is our most significant finding and has the potential to impact how we feed and manage forages in a significant way.
Publications
- E. Raffrenato, R. Fievisohn, K. W. Cotanch, R. J. Grant, L. E. Chase, and M. E. Van Amburgh. 2010. Effect of lignin linkages with other plant cell wall components on in vitro and in vivo NDF digestibility of forages and potential energy yield. 3rd EAAP Inter. Symp. Energy and Protein Metab. and Nutr. (Abstr.) Parma, Italy
- Raffrenato, E. , P.J. Van Soest and M. E. Van Amburgh. 2010. Development of a mathematical model to obtain rate of digestion and prediction of indigestible NDF and dry matter intake from NDF, IVNDFD and ADL. ADSA Modelers Meeting. Can. J. Anim. Sci. (Abstr.)
- Raffrenato, E. and M. E. Van Amburgh. 2010. Refinement of the Estimation of NDF Pool Size and Implications for Intake. Proc. Cornell Nutr. Conf. (350 participants)
- Raffrenato, E., P. J. Van Soest, and M. E. Van Amburgh. 2009. An evaluation of the factors affecting the rate and extent of NDF digestion and a mathematical procedure for defining rates of digestion. EAAP Meeting, Barcelona, Spain. (Abstr.)
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: The data generated to date has been shared in scientific abstracts presented at the American Dairy Science Association, the European Association of Animal Production, and a program in South Africa concerned with low input agriculture. In addition a paper was presented at the Cornell Nutrition Conference in Syracuse, NY. PARTICIPANTS: Emiliano Raffrenato is the doctoral student working directly on the project. Other support is coming from Miner Institute in Chazy, NY. Kurt Cotanch and Robert Fievisohn provided some technical support for analyses of lignin linkages to carbohydrates and Rick Grant is a member of Emiliano's committee and provided some of the financial support for this work. Larry Chase from Cornell Animal Science is also a partner on this study and provided additional resources through a lactating cow experiment we could use to evaluate in vivo relationships among lignin linkages and NDF. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This is the first year of the project, but in this year we have made significant progress in updating methods for fiber evaluation. To date the findings have resulted in the updates of two methods, how we measure lignin in forages and how we measure neutral detergent fiber digestibility.
Publications
- Raffrenato, E. R., M. E. Van Amburgh, and P.J. Van Soest. 2008. Measures of acid detergent lignin recovery and evaluations of the 2.4 time lignin factor for estimating indigestible NDF. J. Dairy Sci. 91:TH57. (Abstr.)
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