Influence of dietary zinc and dexamethasone on immune responses and resistance to Pastuerella hemolytica challenge in growing lambs

Effect of dietary boron on immune function in growing beef steers

Thirty-six Angus and Angus x Simmental cross steers (initial BW 269.5 +/- 22.3 kg) were used to determine the effects of dietary boron (B) on performance and immune function. Steers were fed on one of the three dietary treatments: (i) control (no supplemental B; 7.2 mg B/kg DM), (ii) 5 mg supplemental B/kg DM and (iii) 50 mg supplemental B/kg DM, from sodium borate for 78 days. Supplementation of dietary B had no effect on body weight (BW) gain, feed intake or gain:feed during the study. Jugular blood samples were collected prior to feeding on days 28, 63 and 77 for plasma-B analysis. Supplementation of dietary B increased (p < 0.001) plasma B-concentration in a dose-responsive manner. Furthermore, plasma B-concentration was correlated (p < 0.001; R(2) = 0. 95) to daily B-intake (mg B/day). Jugular blood was also collected, from an equal number of steers from each treatment, on day 42 or 44 for determination of in vitro production of interferon-gamma and tumour necrosis factor-alpha from isolated monocytes and assessment of lymphocyte proliferation. Dietary B did not affect T- or B-lymphocyte proliferation or in vitro cytokine production from monocytes. On day 49 of the study, the humoral immune response was assessed by i.m. injection of a 25% pig red blood cell (PRBC) solution for determination of anti-PRBC IgG and IgM titre responses. Boron-supplemented steers had greater (p = 0.035) anti-PRBC IgG titres than controls on day 7 but not on day 14 or 21 post-injection. Anti-PRBC IgM titres did not differ throughout the sampling period. Results from this study indicate that supplemental B had minimal effects on immune function and did not affect performance of growing steers.

Micronutrients and immune function in cattle

Complex inter-relationships exist between certain micronutrients, immune function and disease resistance in cattle. Several micronutrients have been shown to influence immune responses. The relationship between deficiencies of some micronutrients and disease resistance is less clear. A number of studies have indicated that Cr supplementation may improve cell-mediated and humoral immune response as well as resistance to respiratory infections in stressed cattle. With respiratory-disease challenge models Cr generally does not affect disease resistance. Deficiencies of Cu, Se, vitamin E and Co in cattle reduce the ability of isolated neutrophils to kill yeast and/or bacteria. Cu deficiency reduces antibody production, but cell-mediated immunity is generally not altered. However, Cu deficiency appears to reduce production of interferon and tumour necrosis factor by mononuclear cells. Numerous studies have linked low vitamin E and/or Se status to increased susceptibility of dairy cows to intramammary infections. In contrast to findings in laboratory animals, marginal Zn deficiency does not appear to impair antibody production or lymphocyte responsiveness to mitogen stimulation in ruminants. Co deficiency has been associated with reduced resistance to parasitic infections. It is well documented that vitamin A-deficient animals are more susceptible to various types of infections. beta-Carotene, possibly via its antioxidant properties, may affect immune function and disease resistance independent of its role as a precursor of vitamin A.

Effects of dietary copper and molybdenum on copper status, cytokine production, and humoral immune response of calves

Twenty-four male Holstein calves were used to determine the effects of dietary Cu and Mo on performance, Cu status, and immune function of calves. Calves were fed a milk replacer that was deficient in Cu for 8 wk and then were randomly assigned after weaning to one of four treatments: 1) control (no supplemental Cu or Mo), 2) 10 mg of Cu (from CuSO4)/kg of dry matter (DM) (Cu diet), 3) 5 mg of Mo (from Na2MoO4)/kg of DM (Mo diet), or 4) 5 mg of Cu (from CuSO4) and 5 mg of Mo (from Na2MoO4)/kg of DM (Cu + Mo diet). The basal diet was a semipurified diet that contained approximately 1.1 mg of Cu and 1.1 mg of Mo/kg of DM. Calves fed the Cu and Mo diets gained weight more efficiently than those fed the control and Cu + Mo diets during the 112-d study. By d 84 of the study, calves fed the Cu diet had higher plasma Cu concentrations and plasma ceruloplasmin activities than did calves fed the other three diets and had higher liver Cu concentrations on d 136. Plasma and liver Cu concentrations did not differ among calves fed the control, Mo, and Cu + Mo diets. At d 112, activity of Cu-Zn superoxide dismutase was lower in calves fed the Mo diet than in calves fed the Cu diet. Serum total antibodies to porcine erythrocytes (primary response) were lower in calves fed the Mo diet than in calves fed the Cu diet at 7, 14, and 21 d postinoculation. Production of tumor necrosis factor and interleukin-1 by isolated peripheral blood monocytes was not significantly affected by treatment. Although no differences were apparent in plasma or liver Cu concentrations among calves fed the control, Mo, and Cu + Mo diets, calves fed the Mo diet had a more severe Cu deficiency based on depressed humoral immune response and superoxide dismutase activity.

Zinc oxide and amino acids as sources of dietary zinc for calves: effects on uptake and immunity

Calf starter diets were formulated to contain 60 ppm of Zn, 150 or 300 ppm of Zn in the form of Zn-Met and Zn-Lys, or 300 ppm of Zn in the form of ZnO to compare relative bioavailability and effects on immunity. Holstein heifer calves were weaned at wk 5 and fed experimental starter diets from wk 6 to 12. Feed intake, body weight, Zn concentrations in liver and serum fractions, and mineral concentrations in serum were measured to determine the effects of treatment. In addition, peripheral blood lymphocyte blastogenesis, interleukin-2 production, cytotoxic activity, and the ability of blood neutrophils to phagocytose and kill bacteria were assessed at wk 0, 2, 4, and 6 of the trial. Feed intakes and body weight gains were similar among calves. Concentrations of Zn in serum were elevated in calves fed 300 ppm of Zn as Zn-Met and Zn-Lys but not in calves fed ZnO. Concentrations of Zn in liver were significantly elevated by 300 ppm of Zn in the form of Zn-Met and Zn-Lys (360 micrograms/g) but not by the other Zn treatments or by the control (245 micrograms/g). No treatment had an effect on the concentrations of Lys and Met in serum; however, concentrations of Lys did decrease in serum as the age of the calves increased. There was no significant treatment effect on mitogen-induced lymphocyte blastogenesis, interleukin-2 production, lymphocyte cytotoxicity, or phagocytic and intracellular killing ability of blood neutrophils. These data indicated greater absorption and retention of Zn when administered in the form of Zn-Met and Zn-Lys than that when ZnO was administered to young calves. However, there was no advantage to the immune function of extra dietary Zn.