[The effect of a monensin-containing bolus on the live weight increase and characteristics of rumen fermentation of growing cattle]. / Untersuchungen zum Einfluss eines monensinhaltigen Bolus auf die Lebendmassezunahme und Kennzahlen der Pansenfermentation wachsender Rinder.

Eight feeding experiments (4 on pasture and indoors each) with 401 growing cattle were carried out in order to measure the influence of a monensin device on daily weight gain. The monensin device effected on the average 7 g (1.4%) and 37 g (4.3%) higher daily weight gain on pasture and indoors resp. (P greater than 0.05). The weight gain of animals varied between 92.5 and 112.5% compared with the unsupplemented groups. The monensin device caused a higher weight gain of easier cattle than of heavier ones (greater than 300 kg body weight). The device has had no significant effect on figures of rumen fermentation. Probably the monensin level delivered from the device (100 +/- 50 mg per animal and day) is to low for heavier cattle.

[Investigations concerning the use of the rumen fermentation regulator monensin in feeding fattening bulls]. / Untersuchungen zum Einsatz des Pansenfermoregulators "Monensin" in der Mastbullenfütterung.

In two digestion experiments with wethers and seven feeding experiments with 198 fattening bulls with rations rich in (greater than 55% of the dry matter intake from roughage), the influence of the antibiotic monensin on the digestibility of the ration, on rumen-physiologic characteristic values and on fattening and slaughtering results was investigated. The digestibility of the organic matter and the crude nutrients was not significantly influenced by the use of monensin (20 mg/kg dry matter). The administration of 200 mg monensin per fattening bull and day resulted in an increase of the molar concentration of propionate in the rumen fluid by 9.7 mol%, the concentration of acetate and butyrate decreased by 7.3 resp. 2.8 mol %. On an average of the seven experiments the intake of dry matter was diminished by 5.1% through the use of monensin, the live weight increase remained almost unaffected (3.0% additional increase), feed and energy requirement per kg live weight were improved by 7.9%. The fattening results do not always correspond in the various experiments. The results of the dressing of the carcass, the composition of the carcass and the quality of the meat remained unaffected by the administration of monensin.