Effects of Chronic Heat and Cold Stressors on Plasma Immunoglobulin and Mitogen-Induced Blastogenesis in Calves

Abstract

Fifty-six Holstein calves were used to investigate effects of heat and cold stressors on mitogen-induced blastogenesis of isolated peripheral blood mononuclear cells and immunoglobulins G1 and M in blood plasma. Calves were exposed to constant hot (35 degrees C), constant cold (-5 degrees C), or thermoneutral (23 degrees C) ambient conditions in environmentally-controlled chambers. Immune responses were measured soon after introduction into environmental chambers (3 days) and after various degrees of adaptation (7 and 14 days). Mortality was greater among heat- and cold-exposed calves than among thermoneutral calves. Neither heat nor cold exposure had a direct effect on blastogenesis of peripheral blood mononuclear cells by phytohemagglutinin or concanavalin A. Plasma from heat- and cold-exposed calves then was incorporated into the culture medium at a final concentration of 5% and tested in a mitogenesis assay on peripheral blood mononuclear cells from a single healthy donor. Plasma from heat-exposed calves consistently enhanced tritiated thymidine incorporation into normal peripheral blood mononuclear cells by phytohemagglutinin and concanavalin A as compared to plasma from cold-exposed calves. After heat exposure for 3 to 14 days, immunoglobulin G1 averaged 27% less in heat-exposed calves than in calves that were held at thermoneutrality, but M was unaffected. Cold exposure did not have a consistent effect on G1 or M. These data demonstrate that chronic heat and cold stressors affect calves by altering both antibody- and cell-mediated immunity.

The effect of Zeranol implantation on thermoregulatory, hematological and physiological responses to heat stress in weaned lambs

“…The eosinophile percentage of heat-stressed calves was reduced to half of the control level, although this trend was not statistically significant (K ELLEY et al, 1982). In another study, steers implanted with Zeranol and exposed to a cold stress exhibited such a decrease, which shows that implantation did not counteract the effect of stress on their hematological values (K EL i.EY et al, 1981).…”

The role of shelterbelts in protecting livestock: A review

“…In dairy cows it has been shown to reduce migration of leucocytes to the udder in response to chemotactic stimuli (Elvinger et al 1992). In the month-old calf it reduced plasma lgGi levels by 25% and increased the circulating levels of a factor which potentiates mitogenesis in monocytes (Kelley et al 1982). The latter effect did not occur in a comparable study in lambs (Minton & Blecha 1990), but heat stress has been shown to suppress T-cell-mediated immune responses in sheep, and this effect did not appear to be mediated by adrenocorticosteroids (Niwano et al 1990).…”

Moderate summer heat stress does not modify immunological parameters of Holstein dairy cows

“…Working with calves, Kelley et al (1982a) concluded that heat stress is responsible for alterations of the immune response and that the heat-stress-induced changes in immune events depend on the type of immune response and the length of time that calves are exposed to the stressor. In another study, also undertaken with calves, the same authors (Kelley et al 1982b) found that heat stress had no direct effects on the proliferation of mitogen-stimulated peripheral blood mononuclear cells (PBMC). Furthermore, two in vitro studies demonstrated that exposure of bovine lymphocytes to short and severe heat shock reduced their responsiveness to mitogens or decreased the number of viable cells (Elvinger et al 1991;Kamwanja et al 1994).…”