Effect of feeding two different forms of supplemental methionine on the lactation performance and health status of dairy cows

The objective of this experiment was to assess the effect of a newly developed form of methionine – isopropylester 2-hydroxy-4 (methylthio) butanoic acid, called MetaSmart on the lactation performance, in particular the production of milk protein, and on the physiological status of dairy cows. At the same time, the efficiency of this supplement was compared with ruminally protected form of methionine, Smartamine M. The experiment of 3x3 Latin square design was conducted with a total of 30 high-yielding dairy cows, divided into three well balanced groups. Each period lasted four weeks – three weeks of the preliminary period and one week of experimental period during which the samples of milk, blood and rumen fluid were collected. A total mixed ration (TMR) based on maize silage, lucerne silage, lucerne hay, brewer’s grains and concentrate mixture was offered ad libitum four times a day. The experimental diets contained MetaSmart (42.5 g/d), and Smartamine M (19 g/d), respectively. The control diet was supplemented with soybean meal to achieve the same concentration of crude protein. The highest average daily milk yields (31.34 kg) and simultaneously the highest production of milk protein and milk fat were found for the diet with MetaSmart. Inclusion of both Smartamine M and MetaSmart in the diet increased milk protein content by 0.11% (3.45%) and 0.07% (3.41%), respectively, in comparison with the control group. But, no significant differences (P > 0.05) were found for milk production, and within the values of basic parameters of rumen fluid and blood plasma. However, the concentrations of methionine in blood plasma were about 7.36 and 0.17 μmol/l higher for diets with Smartamine M and with MetaSmart, respectively, than for the control group. The inclusion of both Smartamine M and MetaSmart in the diet can increase milk production and improve the methionine status of dairy cows.