Milk urea concentration (MUC) is considered to be a good indicator of urinary nitrogen excretion in lactating dairy cows. Over the period of seven years (2005-2012) the proportion of samples with the MUC bellow the recommended value (15 mg/100 ml) varied between 20 and 30% with no trend of decrease or increase. A drop of about 8% (from 15% to 7%) in number of samples with MUC above the recommended value (30 mg/100 ml) was recognized in the last seven years. According to the results of 735,632 records obtained between the years 2009 and 2012 the highest MUC can be found during the summer months (from June to August; averages from 20.4 to 20.7 mg/100 ml) and the lowest during the winter months (from November to February; averages from 17.7 to 18.0 mg/100 ml). The highest average MUC (31 mg/100 ml) was observed in summer samples from cows that were grazed or given diets containing fresh grass. In milk samples from cows fed with basal diets of hay (exclusively) higher MUC were observed (22.2 mg/100 ml) than from cows feeding a combination of hay and grass silage (19.2 mg/100 ml), a combination of maize and grass silage (19.4 mg/100 ml) or a combination of maize silage, grass silage and hay (17.4 mg/100 ml). The lowest MUC was observed in basal diets comprised of maize silage and hay (13.9 mg/100 ml). Introduction of routine MUC determinations resulted in a decline of milk samples percentage above the upper recommended limit. It indicates that MUC determinations can reduce the nitrogen footprint from milk production.
F.01 Acquisition of new practical knowledge, information and skills
COBISS.SI-ID: 4171368Sodium monensin is an ionophore antibiotic, used in many countries as feed additive in cattle breeding, however not in EU countries. The ionophore monensin affects bacterial energy metabolism and subsequently changes ruminal fermentation which results in increased feed efficiency [1]. In EU the use of monensin as feed additive in cattle breeding and many other antibiotics used as feed additives was banned in 2006 [2] due to the concerns related to spreading of antibiotic resistances and possible transfer of these from animals to humans. Since the exact mechanism of bacterial resistance to monensin is not understood and the ideas about the lateral transfer of the monensin resistance among gut bacteria lack evidence, we started to investigate possible resistance mechanism in bacteria from the genus Prevotella, which represent important bacterial population inhabiting the rumen as well as other gastrointestinal niches of animals and man and are capable of adaptation to monensin present in high concentrations [3]. Our aim was to compare phenotypic, metabolic and genetic traits of wild type strains of Prevotella bryantii and Prevotella ruminicola, and their monensin adapted descendants. Since the monensin affects bacterial membranes and fermentation, gas chromatography was used to investigate membrane long-chain fatty acid profiles and volatile fatty acids, the main fermentation products. To explore the possible genetic basis of the acquired monensin resistance genomic sequencing of the wild types and adapted strains was performed and sequences compared. Potential of the emerging cross resistances to other antibiotics was examined too, screening more than 20 different antibiotics.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 3240840Greenhouse gas emissions and options for mitigation were presented.
B.04 Guest lecture
COBISS.SI-ID: 4387944