Pregnancy is a period characterized by an increase in metabolic demand owing to changes in female physiology and the requirements for growing fetus. The changes that take place in various body systems during pregnancy result in an increased oxygen demand and changes in energy substrate utilization by dam, especially in the feto- placental unit. Pregnancy, though a physiological state, is a stressful condition that favors the oxidative stress and results in an imbalance between pro-oxidant and antioxidant systems of the body leading to potential damage. Metabolic demands associated with late gestation, parturition, and initiation of lactation has been supposed to increase the production of reactive oxygen species (RGS).

The current study was undertaken to elucidate the dynamics of different biological health and metabolic markers in crossbred cows at different stages of pregnancy and non-pregnant stage. The study was carried out on 40 (age range between 4 and 11 years) clinically healthy crossbred cows (Sahiwal + Holstein-Friesian). The animals were divided into four groups; first trimester, second trimester and third trimester of pregnancy, and non-pregnant, with 10 cows in each group. The results revealed that serum total oxidants, ceruloplasmin oxidase and tri- iodothyronine_ concentrations were higher (P<0.05) during third trimester of pregnancy compared to non-pregnant crossbred cows. Serum arylesterase concentration was lower (P<0.05) during second and third trimesters of pregnancy compared to non-pregnant stage. The concentration of serum total homocysteine was higher (P<0.05) during third trimester compared to first and second trimesters of pregnancy. The concentrations of serum total antioxidants, paraoxonase, total thyroxine, aspartate aminotransferase and alanine aminotransferase were not different during pregnancy and non-pregnant stage in crossbred cows.

In conclusion, the biological health markers specially total oxidant status, aryl esterase, ceruloplasmin oxidase, total homocysteine and tri-iodothyronine of pregnant crossbred cows can provide useful information about the progression of pregnancy and can also be used as management tool for the improvement of the health status during pregnancy.