Response to adrenocorticotropic hormone or corticotrophin-releasing hormone and vasopressin in lactating cows fed an immunomodulatory supplement under thermoneutral or acute heat stress conditions.

Adrenal responsiveness was tested in nonpregnant, lactating Holstein dairy cows fed diets supplemented with OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ), an immune modulator, and in nonsupplemented control (CON) cows following bolus infusions of a combination of corticotropin-releasing hormone (CRH; 0.3 µg/kg of BW) and arginine vasopressin (VP; 1.0 µg/kg of BW) or ACTH (0.1 IU/kg of BW) in 2 environments: thermoneutral [TN; temperature-humidity index (THI) <60] for 24 h/d and heat stress (HS; THI >68 for 17 h/d). Cows (506) were initially fed OG (n = 254) or CON (n = 252) diets for 44 d before selection of a subgroup of cows (n = 12; 6 OG, 6 CON) for the study. The 2 subgroups were balanced for parity, milk yield, and days in milk. All cows were transported to and housed in 2 environmentally controlled rooms at the University of Arizona Agricultural Research Complex (Tucson). Cows were given 3 d to acclimate to the rooms and then underwent 12 d of TN conditions and then 8 d of HS conditions for a total of 24 d on experiment. Cows were infused with CRH-VP on d 9 of TN and on d 1 of HS and with ACTH on d 10 of TN and on d 2 of HS. Hormone infusions took place at 1000 h (0 h) on each infusion day. Blood samples, taken in 30-min intervals, were first collected at 0800 h (-2 h) and were drawn until 1800 h (8 h). Before infusion, serum progesterone was elevated in OG cows compared with CON cows. Infusion of releasing factors (CRH-VP or ACTH) caused increases in serum cortisol and progesterone, but cortisol release was greater in CON cows than in OG cows during HS, whereas progesterone did not differ between the 2 treatments. Serum ACTH increased following infusion of releasing factors, but this increase was greater following CRH-VP infusion than ACTH infusion. Serum bovine corticosteroid-binding globulin also increased following infusion of releasing factors in both treatment groups, but this increase was greater during HS in cows fed OG. The free cortisol index (FCI) increased following CRH-VP and ACTH and was higher in HS than in TN for both OG and CON cows. However, the FCI response was blunted in OG cows compared with CON cows during HS. Heat stress enhanced the adrenal response to releasing factors. Additionally, the adrenal cortisol and FCI response to releasing factors was reduced during acute heat stress in cows fed OG. Collectively, these data suggest that OG supplementation reduced the adrenal responsiveness to factors regulating cortisol secretion during acute HS.

Age-related changes in porcine corticosteroid-binding globulin (pCBG) as determined by an enzyme-linked immunosorbent assay.

The objectives of this study were to develop an assay for the direct measure of porcine corticosteroid-binding globulin (pCBG) and to confirm age-related changes in plasma pCBG concentration. Isolation and purification of pCBG from plasma was performed by affinity chromatography and HPLC-DEAE anion exchange techniques. Analysis by SDS-PAGE revealed two polypeptides (54 and 59 kDa) having similar amino acid homology (>50%) to previously reported sequences of seven mammalian species for the first 33 amino acids. Porcine CBG (20 ng/well) was immobilized to microtiter plates and standards or samples added along with rabbit antiserum developed against the purified pCBG. Goat anti-rabbit IgG-alkaline phosphatase conjugate was added followed by p-NPP substrate. The resultant color development was read at 405 nm. Intra- and interassay coefficients of variation (n=26) of a pooled sample were 10 and 15%, respectively. Age-related changes (P<0.001) in plasma pCBG concentration (n=203) from day 3 through 168 of age confirmed that, in the pig, changes seen in the percent distribution of cortisol among protein bound and free forms around day 28 of age are associated with an increase in CBG concentration.

Characterization of bovine conceptus proteins produced during the peri- and postattachment periods of early pregnancy.

Bovine conceptuses removed from the uterus during the peri- and postattachment periods of placentation (Days 17-24 and 26-38, respectively) were cultured in a modified minimum essential medium in the presence of L-[3H]leucine to characterize in vitro synthesis of proteins released into the medium. Patterns of protein production were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by fluorography of dried gels. Four groups of low molecular weight acidic proteins (LMWAP) were observed to be synthesized during the peri- and postattachment periods. The number and relative concentrations of these changed with development. One group (A) consisted of three major and two or more minor isoelectric species (pI approximately equal to 5.8-6.8); these were the major synthesized proteins observed from Days 17-22. The major polypeptides of Group A were present at all time points examined through Day 38 and, in several preparations, appeared as doublets (Mr approximately equal to 22,000 and 24,000) through Day 29 but not thereafter. Group A polypeptides from Day 19 and 36 conceptus cultures were demonstrated by immunoblot analysis to cross-react with antiserum produced against ovine trophoblast protein-1 (oTP-1). A second group of proteins (A1) and a single protein (B) in the 20,000-24,000 Mr range were observed between Days 17 and 22. These were acidic relative to Group A and were not detected after Day 22. A fourth group (C) of LMWAP (Mr approximately equal to 14,000-18,000) was first observed around Day 21 and appeared to increase relative to Group A through Day 29. One protein from this group, C3, was the predominant LMWAP at Day 38.(ABSTRACT TRUNCATED AT 250 WORDS)