Dietary strategies to modulate performance, health, and immune responses in Holstein calve

A series of in vitro experiments were conducted to examine the effect of exogenous conjugated linoleic acid (CLA) and peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist, rosiglitazone, on lipopolysaccharide (LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) production in cultured bovine blood, and to identify the signaling pathway through which LPS and PPAR-gamma interact to alter TNF-alpha biosynthesis in vitro. Additionally three in vivo experiments were conducted in Holstein calves. The first experiment was an observational prospective cohort study conducted with 1,247 calves from 7 dairy farms to determine the effects of passive immunity at 48 h of life on performance, morbidity and mortality risk, survival time and rearing costs in preweaned Holstein calves. The second and third experiment tested the effects of feeding pomegranate extract and Saccharomyces cerevisiae fermentation products (SFP), respectively, on performance, health, and immunocompetence of Holstein calves during the preweaning period.;Co-incubation with trans-10, cis-12 CLA isomer or rosiglitazone decreased LPS-induced TNF-alpha production. Rosiglitazone-induced TNF-attenuation was reversed when blood was treated with both rosiglitazone and GW9662, a selective PPAR-gamma antagonist. Addition of rosiglitazone to the culture medium tended to reduce nuclear factor kappa Bp65 concentration in nuclear and cytosolic extracts isolated from cultured PBMC.;Calves classified as having adequate passive transfer (APT; serum IgG ≥ 1.0 g/dL) had greater total DM intake and feed conversion ratio during the preweaning period. Daily grain intake and body weight were greater in APT calves during the first 30 d of age. Calves with APT had reduced risk to develop morbidity, pneumonia, and multiple diseases, and had less number of disease events per calf. Calves with failure of passive transfer (FPT) had 3.6 times greater hazard of dying in the first 75 d of age. Rearing costs and income per calf were greater for calves with APT than those with FPT. The probability of death within the first 75 d of age decreased as IgG concentration in serum increased. Increase in STP reduced the probability of death, but values above 7.0 g/dL increased the probability of death. Serum IgG as percent of STP was the best predictor of probability of death than STP and IgG concentration.;Feeding 15 mg of gallic acid equivalent/kg of body weight or subtherapeutic doses of antibiotics (200 mg oxytetracycline and 200 mg neomycin/d) to preweaned calves did not benefit performance, health, and immune and antioxidant response.;Supplementing dairy calves with SFP added to milk up to 4 g/d in the first 2 months of age did not affect performance. Calves fed SFP had an increased proportion of neutrophils with capacity for oxidative burst, but this effect did not influence measures of health based on daily fecal, nasal, ocular, cough and attitude scores, and rectal temperature.