Arieli, A., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Mabjeesh, S.J., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Shabi, Z., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Bruckental, I., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Aharoni, Y., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Zamwel, S., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Tagari, H., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Mabjeesh, S.J., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Shabi, Z., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Bruckental, I., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Aharoni, Y., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Zamwel, S., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
Tagari, H., Department of Animal Science, Fac. Agric., Food Environ. Qual. S., Hebrew University of Jerusalem, Rehovot 76100, Israel
This study analyzed the relationships among the effective degradabilities of organic matter (OM) in feedstuffs, which were assessed separately by an in situ method and a direct in vivo measurement of the rumen degradation of OM in the diets of Holstein dairy cows. For this comparison, 80 individual data points were used from studies of dairy cows that were in midlactation and that had been cannulated in the rumen and abomasum. In vivo evaluation of the true degradability of OM in the rumen was based on rare earth digesta markers. Purine N served as a microbial marker. Feed samples were incubated in the rumens of dairy cows for 3, 6, 9, 12, 24, 48, and 72 h, and effective rumen degradation was calculated from the percentage of residual OM for rumen outflow rates of 4, 6, and 8%/h. Evaluations of rumen degradability of OM by the in situ method were correlated with actual in vivo measurements of rumen degradability of OM (r2 = 0.31, 0.34, and 0.37; SE of the estimate = 4.1, 4.0, and 3.9%, respectively). We concluded that the in situ method is a useful tool for providing reliable estimates of rumen degradability of OM in dairy cows.
