Diselementosis as a risk factor of embryo loss in lactating cows

Abstract

The aim of this research was to reveal the impact of bioelemental status of dairy cows on intrauterine growth restriction and embryo death at early gestation stages. The research included 22 Holstein cows with average annual dairy productivity of 6400-7600 kg. All animals were subjected to transrectal ultrasonography to determine corpus luteum and pregnancy status, and their blood was sampled for biochemical analyses on the 19th-22nd, 28th-32nd, and 38th-45th days of gestation. Zinc, copper, manganese, and selenium blood contents were determined by atomic absorption spectrophotometry. Serum levels of calcium, phosphorus, and magnesium were determined with an automatic biochemistry analyzer. Protein-bound iodine was determined spectrophotometrically. Analysis of results was realized based on the character of embryo development: physiological formation (Group I, n = 9), growth restriction (Group II, n = 8), and death (Group III, n = 5). Serum concentrations of Ca, P, and Mg were 2.76-2.84 mmol/L, 1.77-1.92 mmol/L, and 1.13-1.36 mmol/L in range; blood contents of Zn, Cu, Mn, and Se were 40.8-52.7 µmol/L, 15.9-18.7 µmol/L, 2.50-3.43 µmol/L, and 1.23-1.41 µmol/L in range; and protein-bound iodine was 0.32-0.36 µmol/L in Group I. Serum concentration of the studied trace elements was lower in Groups II and III in comparison with Group I. Cows of Group II demonstrated the following indices: calcium content, 2.72-2.79 mmol/L; phosphorus content, 1.79-1.97 mmol/L; magnesium, 0.98-1.09 mmol/L; zinc, 33.8-36.8 µmol/L; copper, 13.9-15.3 µmol/L; manganese, 2.50-2.89 µmol/L; selenium, 1.04-1.11 µmol/L; protein-bound iodine, 0.29-0.37 µmol/L. The difference according to the level of serum Ca reached 4.2%, P 6.8%, and Mg 23.5% (P < 0.01), while according to blood concentration Zn was 30.2% (P < 0.001), Cu 21.6%, Mn 15.2%, Se 26.2% (P < 0.05), and protein-bound iodine 21.3% (P < 0.01). Cows of Group III demonstrated the following indices: calcium content, 2.48-2.56 mmol/L; phosphorus content, 1.74-1.93 mmol/L; magnesium, 0.99-1.02 mmol/L; zinc, 31.2-34.0 µmol/L; copper, 12.2-15.4 µmol/L; manganese, 2.24-3.06 µmol/L; selenium, 1.00-1.03 µmol/L; protein-bound iodine, 0.24-0.30 µmol/L. The differences in comparison with cows of Group I reached 11.4% (P < 0.05), 9.4%, 27.2% (P < 0.001), 35.5% (P < 0.001), 20.6% (P < 0.05), 15.2% (P < 0.05), 29.1% (P < 0.05), and 33.3% (P < 0.001), respectively. Disorders of trace elements in cows are one of the main reasons for intrauterine growth restriction and embryo death. Primarily it is connected with magnesium, zinc, copper, selenium, and iodine deficits that have direct or indirect effects on growth, generation, and differentiation of the cells of the developing embryo. Lactating cows with a high level of milk production demonstrate high risk of diselementosis and consequently embryopathy development. Correction of diselementosis in lactating cows should be considered as one of the ways for solving the problem of their fertility.