Pathophysiological aspects of embryonic mortality in dairy cows

Early embryonic mortality and its high frequency in lactating cows are among the causes for a decrease of animal performance, reproduction, and the effectiveness of modern dairy cattle industry as a whole. The aim of this research was to reveal pathogenic significance of maternal endocrine, metabolic and immune risk factors for occurrence of this pathology. The surveys involved black-motley cows with average annual productivity of 6.4-7.6 ths. kg. Pregnancy and embryonic mortality were diagnosed on days 19 to 23, 28 to 32, and 38 to 45after artificial insemination by transrectal ultrasound examination with the use of an ultrasonic scanner Easi-Scan-3 (Great Britain). Venous blood samples were collected during the same periods. Blood progesterone, estradiol-17β, testosterone, proteins, common immunoglobulins, circulating immune complexes, urea, creatinine, cholesterol, glucose, vitamins E and C, total calcium, inorganic phosphorus, protein-bound iodine, magnesium, zinc, copper, manganese, selenium, middle molecular peptides, malonic dialdehyde, alkaline phosphatase activity, alanine aminotransferase, asparate aminotransferase, gamma-glutamyl transferase, catalase, bactericidal and lysozyme activity of blood serum, morphological blood composition were assessed with the use of a biochemical analyzer Hitahi-902 (Japan), а spectrophotometer UV 1700 (Japan), an atomic adsorptive spectrometer Perkin Elmer-703 (USA), а hematology analyzer ABX Micros60 (France), and spectrum analyzer Uniplan (Russia). The blood parameters were tested in 18 animals, 9 ones with physiological embryo formation (control) and 9 ones with embryo death. It was found out that embryonic death is firstly associated with an endocrine insufficiency of sex glands of the mother cows, as reflected by blood progesterone and estradiol-17β level which at various stages of gestation was lower by 12.0-43.3 % and 45.0-85.5 %, respectively, when compared to the animals of control group. Under embryonic death, the mother cows' metabolic profile was characterized by an increase in blood concentration of protein (by 3.2-5.4 %), urea (by 9.8-23.6 %), creatinine (by 10.1-13.5 %), cholesterol (by 10.9-17,1 %), middle molecular peptides (by 6.1-34.7 %). Blood alkaline phosphatase activity was higher by 12.8-36.2 %, alanine aminotransferase - by 3.6-13.2 %, asparate aminotransferase - by 13.8-30.8 %, gamma-glutamyltransferase - by 45.4-77.5 %, and endogenous intoxication index increased by 13.0-40.0 % that was a reflection of liver and kidney insufficiency, cholestasis syndrome manifestation and endogenous intoxication. The pathology was related to the deficiency of essential bioelements, increased lipid peroxidation (LPO), decreased function of antioxidant protection (AOP) system, accumulation of LPO toxic products and oxidative stress development. Under embryo death, blood zinc concentration was 9.7-27.2 % less, copper concentration - 17.6-23.3 % less, manganese - 10.8-15.2 % less, selenium - 16.3-29.1 % less, protein-bound iodine amount - 7.3-33.4 % less, magnesium - 9.7-27.4 % less, glutathione peroxidase activity - 25.8-31.2 % lower, catalase - 26.5-51.2 % lower, vitamin E - 26.3-31.6 % lower, and vitamin C - 25.1-57.1 % lower, as compared to the control animals. The changes in immune status of mother cows with embryonic mortality manifested themselves by an increase in the number of blood leukocytes, their neutrophilic and eosinophilic forms, monocytes, by a decrease in phagocytic activity, the number of lymphocytes, immunoglobulins, bactericidal activity and lysozyme activity in blood serum, and also by vaginal dysbiosis. The conclusion is that diselementosis, oxidative stress and endogenous intoxication, endocrine and immune insufficiency are determinant pathophysiological factors in multiple-factor etiology of early embryonic mortality.