title: [Estimation of marker passage in the digestive tract of dairy cows by different models: influence of stage of lactation, amount of intake and diet composition].
abstract: 12 dairy cows were used to examine the influence of stage of lactation, amount of intake and diet composition on digesta passage from the reticulorumen. Cows were fed on mixed diets, containing on average 34% concentrate and 66% roughage (dry matter basis). The roughage portion consisted of maize silage and either extensively or intensively produced grass silage in the ratio of 40:60 (% as fed). Titanium(IV)-oxide (TiO2) was used as a marker and faecal marker concentrations were determined for 120 h after oral dosing. Samples were taken in four periods-ante partum (1 period) and in the first half of lactation (3 periods)-, each period representing a certain physiological state. Cows were fed according to milk yield with mean dry matter intakes of 12.0, 16.8, 22.6 and 21.2 kg in periods 1 to 4. Passage parameters were estimated by a model with gamma time-dependency (G4G1), by an exponential model and by a model calculating total tract mean retention time as mean value of all points on the marker-excretion curve. Results showed an obvious acceleration of marker passage from the reticulorumen from ante partum to post partum. Total tract mean retention time calculated as mean values of all points on the marker excretion-curves were in good agreement with total tract mean retention times calculated with G4G1. Passage rates from the reticulorumen showed poor agreement between G4G1 and the exponential model. Effects of period and diet past partum were observed for rate of passage from and mean retention time in the fast compartment only, both estimated by G4G1. TiO2 appears to be a suitable marker to estimate passage rates. Values for passage rates were in the range of those reported for concentrate particles by others.
authors.affiliation: Institut für Tierernährung und Stoffwechselphysiologie, Christian-Albrechts-Universität, Kiel, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Rothfuss
authors.forename: K H
authors.initials: KH
authors.lastname: Südekum
authors.forename: M
authors.initials: M
authors.lastname: Stangassinger
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D004068:Digestive System Physiological Phenomena; D004435:Eating / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D007774:Lactation / Q000502:physiology*; D008954:Models, Biological; D006109:Poaceae; D011336:Probability; D013997:Time Factors; D014025:Titanium / Q000032:analysis* / Q000378:metabolism
chemical_list: D015415:Biomarkers; C009495:titanium dioxide; D014025:Titanium