20.500.12556/DKUM-86225 Variabilnost vsebnosti sečnine v mleku krav molznic glede na pasmo, zaporedno laktacijo, stadij laktacije in sezono diplomsko delo Variability of Urea Content in Dairy Cow Milk According to Breed, Parity, Stage of Lactation and Season Koncentracija sečnine v mleku krav molznic posredno nakazuje na oskrbo krav z beljakovinami. Največji vpliv na koncentracijo sečnine v mleku ima prehrana krav molznic oziroma krmni obrok živali, a so za pravilno interpretacijo podatka o vsebnosti sečnine v mleku pomembni tudi drugi dejavniki. V raziskavi smo preučevali vpliv pasme, zaporedne laktacije, stadija laktacije in sezone ter njihovih interakcij na vsebnost sečnine v mleku krav molznic. Izhodiščni podatkovni set je vseboval preko 450.000 kontrol prireje mleka za krave različnih pasem iz preko 700 različnih rej KGZS zavoda Ptuj za obdobje treh let. Ker so bili podatki številčno neuravnoteženi glede na preučevane dejavnike, smo za obdelavo podatkov naključno izbrali manjši set podatkov (n=7970), ki je bil uravnotežen glede na pasmo, zaporedno laktacijo in stadij laktacije. Rezultati so pokazali, da so vsi preučevani dejavniki, razen zaporedna laktacija, imeli značilen vpliv na koncentracijo sečnine v mleku. Interakcije pa so bile, z izjemo ene (pasma × sezona) neznačilne. Pri pasmi je bila koncentracija sečnine v mleku bistveno višja pri kombiniranih pasmah kot mlečnih. Koncentracija sečnine se je na začetku stadija laktacije postopoma dvigovala do sredine laktacije, nato pa začela postopoma upadati. Pri sezoni smo zabeležili najnižjo koncentracijo pozimi, najvišjo pa poleti. Dvojna interakcija med sezono in pasmo, je pokazala, da je črno bela pasma imela poleti in jeseni nižje vrednosti sečnine v mleku kot druge pasme. V raziskavi, se je izkazalo, da imajo sezona in nekateri z živaljo povezani dejavniki nezanemarljiv vpliv na sečnino, kar kaže na to, da je pomembno, da jih pri upravljanju in krmljenju krav molznic upoštevamo. In dairy cow, milk urea content indirectly indicates what is happening in protein metabolism. Animal nutrition has the greatest influence on milk urea content, but other factors are also important for the correct interpretation of milk urea content data. In the present study, the effect of breed, parity, lactation stage and season and their interactions on milk urea content in dairy cows were studied. The original data set comprised over 450000 milk recording data for cows of different breeds from over 700 different farms of KGZS Institute Ptuj for a period of three years. Because the data were unbalanced with respect to the factors studied, we randomly selected a smaller data set (n=7970) for data processing, that was balanced according to breed, parity, and stage of lactation. The results showed a significant effect of all factors studied, except parity, on milk urea content. Interactions among factors were not significant, with one exception breed × season. For breed, urea content in milk was significantly higher in dual purpose breeds than in dairy breed. The urea concentration gradually increased from the beginning to the middle of the lactation period and then gradually decreased. As for the season, the lowest concentration was in winter and the highest in summer. The double interaction between season and breed showed lower milk content in summer and autumn in milk of Holstein breed compared to other breeds. It was demonstrated that the season and the animal-related factors have a non-negligible influence on milk urea. Therefore, it is important to take them into account in the management and feeding of dairy cows. krave molznice sečnina sezona dejavniki povezani z živaljo dairy cows milk urea season animal-related factors true true false M. Kramberger Slovenski jezik Angleški jezik Diplomsko delo/naloga 2023-10-26 08:09:13 2023-11-14 16:26:18 2023-11-15 03:07:42 0000-00-00 00:00:00 2023 0 Maribor 0 Maribor 1 spletni vir (1 datoteka PDF (VI, 24, [2] str.)) 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 636.2.082.32:637.1:612.664:547.495.2(043.2)=163.6 172147203 VS_Kramberger_Marusa_2023.pdf VS_Kramberger_Marusa_2023.pdf 1 5273CD2A9FAC45322C0BD1A75F9F1A82 55babeb404871d8ff59de6e951fce1e6a3adc458c926e19b2a8998036fe402c5 dd28f509-7fc8-11ee-b512-00155d000105 https://dk.um.si/Dokument.php?lang=slv&id=174043 Fakulteta za kmetijstvo in biosistemske vede 0 0 0