Blood metabolites and haematological indices of pregnant beef cows fed rumen-protected methionine

The effect of rumen-protected DL-methionine on some blood biochemical and haematological values of cows in approximately the last 102 days of pregnancy was examined. Twenty-six cows in the third stage of gestation were divided into two groups of equal number, a control (C) and an experimental group (E). Cows were fed meadow hay, maize grain silage and a 500 g fodder mixture (35% CP). In addition to the fodder mixture, cows in group E received 15 g rumen-protected DL-methionine per animal daily (Mepron (R) M85). Blood samples were collected on approximately days 102: 68 34 and 1 prior to parturition. Plasma glucose concentrations of cows in group E were significantly decreased over a long part of the trial period (68 and 34 days prior to parturition) (P=0.046 and P=0.0175, respectively). Plasma urea concentration in group C was decreased close to statistical significance (P=0.053) on the 681 day prior to parturition. No significant differences were found in plasma concentrations of total protein, albumin, triacylglycerols, total cholesterol and creatinine between the two groups during the trial. The activity of alanine aminotransferase in animals of group E was lower, close to statistical significance (P=0.052) 34 days prior to parturition. No significant differences were found in plasma of asparate aminotransferase, gamma-glutamyltransferase and alkaline phosphatase levels between groups during experimental feeding. Cows in group E had a lower red blood cell count on the 68th and 34th days prior to parturition (P=0.316 and P=0.153, respectively). On the 68th day before calving the lower number of leukocytes was close to statistical significance (P=0.0785), with highly significant neutropenia in absolute (P < 0.001) and relative (P=0.039) terms, and a decreased neutrophyles/lymphocytes ratio (P < 0.001). The results indicate that rumen-protected methionine could have an anti-stress effect on cows during late gestation in winter stable feeding and holding conditions.