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Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/23/2004 Publication Date: 11/15/2004 Citation: Soder, K.J. 2004. Influence of rumen inoculum source on in vitro dry matter digestibility of pasture. Professional Animal Scientist. 21:45-49. Interpretive Summary: Measuring the digestibility of feeds is important in determining their nutritional value. However, factors associated with the source of rumen fluid used to digest the feed samples, such as individual differences among cows or the diet of a donor cow, have been shown to affect the digestibility of different feeds. Additionally, very little is known concerning the effects of digesting samples of pasture plants in rumen fluid from a cow fed a pasture diet versus rumen fluid from a cow fed hays, silages, and concentrates. In this study, the effect of source of rumen fluid inoculum on digestibility of pasture plants was measured using two sources of rumen fluid inoculum (pasture-fed versus stored feed-fed) from different donor cows. The results indicate that digestibility was significantly affected by both rumen fluid inoculum source and by individual donor cow. These results emphasize the importance of using a donor cow that is consuming a diet similar to the feed being tested. Feed ingredients of the diet of the donor cow, as well as chemical composition, should be described when reporting results of in vitro dry matter digestibility studies. Technical Abstract: The objectives of this study were to determine if the IVDMD was affected by rumen fluid donor source (pasture vs. total mixed ration diet) and to determine if IVDMD was affected for source of inoculum from five individual cows. Four pasture treatments varying in level of pasture species diversity were digested using the traditional Tilley and Terry method. Source of inoculum affected in vitro DM digestibility; compared with the pastured donor cow diets, samples digested in rumen fluid from the total mixed ration donor cow diet resulted in lower digestibility values in two of four pasture diets, and tended to be lower in the remaining two pasture diets. In vitro dry matter digestibility was also affected by individual cow used as source of rumen inoculum; samples digested in rumen fluid from the one pastured cow had higher in vitro dry matter digestibility values than all other treatments, and in all cases, samples digested in rumen fluid from each of the individual pastured cows tended to be higher than samples digested in rumen fluid from the cow fed the TMR. These results emphasize the importance of using a donor cow that is consuming a diet similar to that being tested. Extra caution should be taken when interpreting the in vitro dry matter digestibility results obtained on pasture samples from outside labs, especially if the donor cow diet is unknown. Feed ingredients of the diet of the donor cow, as well as chemical composition, should be described when reporting in vitro dry matter digestibility. |
