Use of protected methionine (Mepron M 85) in cattle

The ruminal stability of Mepron M 85 and the effect of supplementation with Mepron M 85 on fi ee methionine level of blood were studied in rumen-fistu lated cows and rumen- and duodenum-fistulated growing bulls. In five rumen- fistulated cows in situ 69.5% and 64.6% of the methionine content of Mepron M 85 was found after ruminal incubation of 16 h and 24 h, respectively. Da ily rations of the rumen fistulated cows were supplemented with 15.0 g DL-m ethionine and 17.7 g Mepron M 85, which increased the free methionine level of blood fi om 13.64 mu mol/L to 15.35 and 20.46 mu mol/L, respectively, t hree hours after feeding. In the four rumen- and duodenum-fistulated growin g bulls, supplementation with 15.0 g DL-methionine and 17.7 g Mepron M 85 i ncreased the total methionine getting into the duodenum during 24 h from 14 .99 g to 16.84 and 20.84 g, respectively. The influence of Mepron M 85 on m ilk production was studied in 35 pairs of Hungarian Fleckvieh x Holstein-Fr iesian cows. The animals were coupled on the basis of the number of finishe d lactations, milk production in the previous lactation, and the date of ca lving. Daily supplementation of 18.0 g Mepron M 85 increased daily milk pro duction significantly (p < 0.05), by 1.24 litres. Milk fat content also inc reased significantly (from 3.10% to 3.19%, p < 0.05) in the experimental gr oup. The supplementation did not influence milk protein content.