MILK UREA AS A PARAMETER OF DAIRY COW FEEDING

U tijeku ljetne sezone 2003. na mliječnoj farmi govedarskog praktikuma Srednje gospodarske škole u Križevcima, ispitali smo utjecaj hranidbe krava na sastav mlijeka. Posebno smo ispitali utjecaj opskrbljenosti proteinima i energijom na koncentraciju uree u mlijeku. Urea u mlijeku je primjenjiv indikator opskrbljenosti organizma hranjivim tvarima. Mliječne krave, predmet istraživanja u tom razdoblju imale su izrazite oscilacije u hranidbi, čime je došlo do čestih promjena opskrbe proteinima odnosno energijom. Ispitivani parametar, urea u mlijeku pokazala je adekvatno hranidbi, vrlo niske rezultate (5,38 mg/dcl) u prvoj fazi hranidbe, da bi se balansiranjem obroka pri kraju kontroliranog razdoblja, podigla na22,45 i 32,08 odnosno 30,15 mg/dcl. Povećanje koncentracije uree u mlijeku pratilo je i povećanje postotka mliječne masti sa 4,29 na 4,75% i proteina sa 4,29 na 4,75%.The influence of feeding on milk composition was investigated at the dairy farm of the cattle practicum of the Secondary Agricultural School at Križevci during the summer period of 2003. Special emphasis was laid on the influence of protein and energy levels on urea concentration in milk. Milk urea is an applicable indicator of the availability of nutrients in the organism. Feeding dairy cows, as trial subjects, varied considerably in the studied period, which caused frequent changes in protein and energy levels. Milk urea, as the tested parameter, rendered, depending on feeding, very low results (5.38 mg/dcl) in the first feeding phase, which were then increased by ration balancing to 22.45 and 32.08 and 30.15 mg/dcl by the end of the monitored period. The increase of urea concentration in milk was accompanied by an increase of the milk fat content from 4.29 to 4.75% and protein content from 4.29 to 4.75