Changes in bovine leukemia virus serological status and lymphocyte count between dry-off and early lactation in Michigan dairy cows

Dairy Cows Experimentally Infected With Bovine Leukemia Virus Showed an Increased Milk Production in Lactation Numbers 3–4: A 4-Year Longitudinal Study

Bovine leukemia virus (BLV) is widespread in global cattle populations, but the effects of its infection on milk quantity and quality have not been clearly elucidated in animal models. In this study, 30 healthy first-lactation cows were selected from ≈2,988 cows in a BLV-free farm with the same criteria of parity, age, lactation number, as well as milk yield, SCS, and composition (fat, protein, and lactose). Subsequently, these cows were randomly assigned to the intervention (n = 15) or control (n = 15) group, and reared in different cowsheds. Cows in the intervention group were inoculated with 1 × phosphate-buffered solution (PBS) resuspended in peripheral blood mononuclear cells (PBMC) from a BLV-positive cow, while the controls were inoculated with the inactivated PBMC from the same individual. From June 2016 to July 2021, milk weight (kg) was automatically recorded by milk sensors, and milk SCS and composition were originated from monthly performed dairy herd improvement (DHI) testing. Fluorescence resonance energy transfer (FRET)–qPCR and ELISA showed that cows in the intervention group were successfully infected with BLV, while cows in the control group were free of BLV for the entire period. At 45 days post-inoculation (DPI), the numbers of whole blood cells (WBCs) (P = 0.010), lymphocytes (LYMs) (P = 0.002), and monocytes (MNCs) (P = 0.001) and the expression levels of IFN-γ (P = 0.013), IL-10 (P = 0.031), and IL-12p70 (P = 0.008) increased significantly in the BLV infected cows compared to the non-infected. In lactation numbers 2–4, the intervention group had significantly higher overall milk yield (P < 0.001), fat (P = 0.031), and protein (P = 0.050) than the control group, while milk SCS (P = 0.038) and lactose (P = 0.036) decreased significantly. Further analysis indicated that BLV infection was associated with increased milk yield at each lactation stage in lactation numbers 3–4 (P = 0.021 or P < 0.001), but not with SCS and milk composition. Together, this 4-year longitudinal study revealed that artificial inoculation of BLV increased the milk yield in cows in this BLV challenge model.

The effectiveness of the use of Aminoseleferon-B with immunodeficiency in highly productive cows under conditions of technogenic environmental load

Highly productive animals, which are characterized by a more intense metabolism and regulation of the neurohumoral system, are more sensitive to a pool of adverse environmental conditions and can often be accompanied by metabolic disorders, a decrease in the immunobiological status of the macroorganism, reproductive function disorders and the development of pathological processes of various etiology and localization. The studies were carried out in the conditions of a large dairy complex in the Voronezh region located 25 km from a chemical plant for the production of mineral fertilizers: ammonia, ammonium nitrate, nitric acid. Its total emissions to the environment are 5316.5 tons per year, including 4480.3 tons of gases. Studies have been carried out to study the effectiveness of the use of Аminoseleferon-B to correct the immune status of highly productive cows in an immunodeficient state, under conditions of technogenic environmental stress. It was established that Аminoseleferon-B contributed to the activation of humoral and cellular links of nonspecific immunity, the reduction of birth and postpartum pathology, the increase in the effectiveness of treatment, and the improvement of reproductive function.