Abstracts Category : Other

Intake capacity of the Icelandic dairy cow. Effect of animal factors, concentrate ratio and feeding method

by Dgg Gunadttir Lilja

Accurate prediction of dry matter intake (DMI) is crucial to formulate a feed ration that maximizes feed efficiency. The model predicting the DMI of the Icelandic dairy cow in the co-Nordic feed evaluation system NorFor needed an update to be able to predict the DMI more accurately. The aims of this study were to collect new data on the DMI of the Icelandic dairy cow in late lactation, and under feeding situations that are common today, to facilitate improvements on the prediction equation of the Icelandic dairy cow. Two studies were conducted, one observational study with the objective to obtain new data on the DMI in late lactation (Study 1) and one experimental study to compare the DMI related to different feeding strategies (Study 2). Study 2 included three treatments, a total mixed ration with a 55% concentrate ratio (TMR55) and a 45% concentrate ratio (TMR45), and separate feeding aiming at a 45% concentrate ratio (SF45). Primiparous cows fed TMR had significantly higher DMI than those fed SF45 (p<0.05), while there was no significant difference in the DMI between treatments for multiparous cows (p>0.1). Both primiparous and multiparous cows in the TMR treatments had significantly higher yield of ECM than cows fed SF45 (p<0.001). New coefficients were fitted to the Norfor equation predicting intake capacity (IC) using the data obtained in Study 1 and Study 2. The new coefficients decreased the prediction error (RMSPE) of the DMI by 0.15 and 0.24 kg DM/d for primiparous and multiparous cows respectively and increased the R2 compared to the current coefficients. The suggested coefficients for the multiparous cows increase the accuracy of the DMI prediction compared to the current coefficients. The suggested coefficients for primiparous cows, however, increased the line bias substantially which suggests that the model structure is inadequate. Data from these studies and earlier studies of the DMI of the Icelandic dairy cow should be used together to fit new coefficients to the IC prediction equation.; Grundvallaratrii hagkvmrar furtlanagerar er a geta tla t tilteknu fri ea furblndu. rf var a afla aukinna gagna um tgetu slensku mjlkurkrinnar til a geta endurbtt splkingar fyrir t sem eru notaar furtlanager samnorrna furmatskerfinu NorFor. Markmi essa verkefnis var annars vegar a safna ggnum seinni hluta mjaltaskeis (rannskn 1) og hins vegar a afla gagna um t vi mismunandi frunarastur sem algengar eru dag slenskum kabum (rannskn 2). Rannskn 2 byggi rem frunarmeferum, heilfrun me annars vegar 55% og hins vegar 45% kjarnfurhlutfalli (TMR55 og TMR45) og askildri frun sem miai a 45% kjarnfurhlutfalli (SF45). Heildart fyrsta klfs kvgna heilfri var marktkt meira en eirra sem voru askildri frun (p<0,05) en ekki var marktkur munur ti milli mefera hj eldri km (p>0,1). Nyt ka sem fengu heilfur var marktkt meiri en ka sem voru askildri frun (p<0,001). etta tti vi um bi fyrsta klfs kr og eldri