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.

Pre-weaning plane of nutrition and Mannheimia haemolytica dose influence inflammatory responses to a bovine herpesvirus-1 and Mannheimia haemolytica challenge in post-weaning Holstein calves.

The objectives of this study were to determine whether plane of nutrition (PON) of milk replacer previously provided to calves, and dosage level of Mannheimia haemolytica (MH), influenced inflammatory responses to a combined viral-bacterial respiratory challenge. Holstein calves (1 d of age; n = 30) were assigned to treatments in a 2 × 3 factorial with pre-weaning PON and MH dose as main effects (n = 5 per treatment). Calves were fed either a low (LPN; n = 15) or a high PON (HPN; n = 15) from birth through weaning. Calves fed LPN were fed 436 g of dry matter (DM) per day of milk replacer until weaning, and HPN calves were fed 797 g of DM per day of milk replacer from d 1 to 10 and 1,080 g of DM per day from d 11 until weaning. Calf starter and water were offered ad libitum. Calves were step-down weaned beginning at d 54 and moved into an enclosed barn at d 70. Indwelling rectal temperature (RT) recording devices and jugular catheters were inserted at d 80. Calves were challenged with 1.5 × 108 plaque-forming units (pfu) per mL of bovine herpesvirus-1 (BHV-1) in each nostril at d 81 and with either 106, 107, or 108 cfu of MH at d 84. Blood samples were collected at varying intervals relative to BHV-1 and MH challenges. Four LPN calves either died or were euthanized soon after the 144-h observation period, whereas all HPN calves survived the entire observation period. As dosage of MH administered increased, acute and systemic inflammatory responses increased. Higher doses of MH resulted in increased leukocyte, neutrophil, and haptoglobin concentrations in infected calves. Data from the current study suggest that the highest dose, 108 cfu, triggered weaned calves' acute disease response, whereas the lower doses, 106 and 107 cfu, caused more moderate inflammation and disease. The effects of PON on inflammation responses to the disease challenge indicated that calves previously fed the LPN diet had more severe pathophysiological responses. Calves fed LPN showed higher peripheral neutrophil and leukocyte counts and serum haptoglobin concentrations following the BHV-1 challenge. Additionally, following the MH challenge, LPN calves had higher peripheral neutrophil counts, neutrophil-to-lymphocyte ratios, and serum tumor necrosis factor-α concentrations. These data demonstrate that higher doses of MH increase the acute inflammatory response and prolong inflammation, and that calves previously fed LPN responded more severely to the combined viral-bacterial respiratory challenge.

Influence of Saccharomyces cerevisiae fermentation products, SmartCare in milk replacer and Original XPC in calf starter, on the performance and health of preweaned Holstein calves challenged with Salmonella enterica serotype Typhimurium.

This study was designed to investigate the effects of supplementing SmartCare (SC; Diamond V, Cedar Rapids, IA) in milk replacer and Original XPC (XPC; Diamond V) in calf starter on performance and health of preweaned calves following an oral challenge with Salmonella enterica. The study was performed in two 35-d periods with 30 Holstein bull calves (2 ± 1 d of age) per period. In each period, calves were blocked by location in the barn and randomly assigned to treatments that included control, base milk replacer and calf starter with no added Saccharomyces cerevisiae fermentation products; SC, milk replacer with 1 g of SC/calf per day and base calf starter; and SC+XPC, milk replacer with 1 g of SC/calf per day and calf starter with 0.5% XPC on a dry matter basis. Calves were fed 350 g of milk replacer solids at 14% dry matter twice daily at 0700 and 1700 h. Calf starter and water were offered ad libitum and intakes were recorded daily. Calves were challenged with 108 cfu of sulfamethazine-resistant Salmonella enterica serotype Typhimurium orally on d 14 of the study. Fecal Salmonella shedding was determined on d 14 to 21 (daily), 24, 28, and 35 using selective media. Blood samples were collected on d 0, 7, 14, 16, 18, 21, 24, 28, and 35 and analyzed for hematology; plasma were analyzed for haptoglobin concentrations. All data were reported as CON, SC, and SC+XPC, respectively. Calf starter intake was increased from d 22 to 35 among SC+XPC calves and from d 29 to 35 among SC calves. The SC+XPC calves had a lower neutrophil-to-lymphocyte ratio (0.81, 0.83, and 0.69 ± 0.051) throughout the study. The SC+XPC calves also had lower hematocrits (35.1, 35.3, and 33.4 ± 0.54%) and hemoglobin concentrations (10.8, 10.6, and 10.1 ± 0.16 mg/dL) throughout the study. We found a tendency for calves fed SC and SC+XPC to have more solid fecal scores during the week after the challenge. We observed no treatment or treatment × time differences on plasma haptoglobin concentrations (63, 48, and 60 ± 0.5 µg/mL). No treatment differences were observed in the fecal shedding of the Salmonella; however, we noted a tendency for a treatment difference in the percentage of calves positive for Salmonella present in the ileal tissue at d 21 after the challenge (25, 50, and 60%). Supplementing preweaned Holstein calves with both SC in milk replacer and XPC in calf starter improved starter intake and improved fecal consistency immediately after a mild Salmonella enterica challenge, but more data are needed to further understand how these yeast fermentation products influence the immune responses to Salmonella enterica.

Plane of nutrition influences the performance, innate leukocyte responses, and resistance to an oral Salmonella enterica serotype Typhimurium challenge in Jersey calves.

Two experiments investigated how plane of nutrition influences performance, leukocyte responses, and resistance to an oral Salmonella enterica serotype Typhimurium challenge. In experiment 1, 46 (2±1 d of age) calves were randomly assigned to 2 diets: a low (LPN; n=23) and high plane of nutrition (HPN; n=23). The LPN calves were fed 409 g/d of dry matter (DM) of a 20% crude protein and 20% fat milk replacer, whereas HPN calves were fed 610 and 735 g/d of DM of a 28% crude protein and 25% fat milk replacer during wk 1 and 2 to 6, respectively. In experiment 2, 20 bull calves (LPN; n=11 and HPN; n=9) were orally challenged on d 80 with 1.5×10(7) cfu of Salmonella Typhimurium (ATCC #14028). The HPN calves had a greater incidence (87.5 vs. 45.5%) and duration of days with high fecal scores (5.5 vs. 3.5 d). The LPN calves had greater neutrophil surface expression of L-selectin on d 7, 21, and 42. Following the Salmonella Typhimurium challenge, calf starter DM intake was greater among the HPN calves. The percentage of neutrophils producing an oxidative burst was also greater among HPN calves on d 1 to 5 after the challenge. Similarly, the intensity of the oxidative burst tended to be greater among the HPN calves on d 2 and 3 postchallenge. The secretion of tumor necrosis factor-α from whole-blood cultures stimulated with lipopolysaccharide tended to be greater on d 1 and was greater on d 5 and 6 among HPN calves. The median ranks of haptoglobin concentrations were greater and plasma zinc concentrations tended to be decreased among LPN calves. These data indicate that feeding a HPN to Jersey calves improved average daily gain and feed efficiency, but increased the incidence of high fecal scores during the first few weeks of life; however, the HPN Jersey calves may be more resistant to Salmonella Typhimurium after weaning.

Associations between endotoxin-induced metabolic changes and temperament in Brahman bulls.

The influence of temperament on the alteration of metabolic parameters in response to a lipopolysaccharide(LPS) challenge was investigated. Brahman bulls were selected based on temperament score. Bulls (10 months; 211±5kg BW; n = 6, 8 and 7 for Calm, Intermediate and Temperamental groups, respectively) were fitted with indwelling jugular catheters to evaluate peripheral blood concentrations of glucose, blood urea nitrogen (BUN),non-esterified fatty acids (NEFA), insulin, epinephrine and cortisol before and after LPS administration (0.5 µg/kg BW LPS). Feed intake was also recorded. Intermediate bulls consumed more feed than the Temperamental bulls during the challenge (p = 0.046). Pre-LPS glucose (p = 0.401) and BUN (p = 0.222) did not differ among the temperament groups. However, pre-LPS insulin (p = 0.023) was lower, whereas pre-LPS NEFA (p < 0.001),cortisol (p < 0.001) and epinephrine (p < 0.001) were greater in Temperamental than in Calm and Intermediate bulls. Post-LPS glucose was increased in Calm and Intermediate bulls but not in Temperamental bulls(p < 0.001). Insulin concentrations post-LPS were greater in Calm than in Intermediate and Temperamental bulls (p < 0.001). Concentrations of NEFA post-LPS were greater in Temperamental than in Calm and Intermediate bulls (p < 0.001). Serum BUN concentration increased post-LPS, with values being greater in Calm and Intermediate than in Temperamental bulls (p = 0.012). Collectively, these data demonstrate that animal temperament is related to the metabolic responses of Brahman bulls following a provocative endotoxin challenge.Specifically, Temperamental bulls may preferentially utilize an alternate energy source (i.e. NEFA) to a greater degree than do bulls of Calm and Intermediate temperaments. The use of circulating NEFA from lipolysis may reduce the negative metabolic consequences of an immune response by allowing for a prompt answer to increasing energy demands required during immunological challenge, compared with the time required for glycogenolysis and gluconeogenesis.

The effects of early weaning on innate immune responses of Holstein calves.

The objectives of this study were to compare innate immune responses of calves weaned early (EW; n=23; weaned at 23.7 ± 2.3 d of age) with those of conventionally weaned calves (CW; n=22; weaned at 44.7 ± 2.3 d of age). All calves were fed 3.8L of colostrum within 12h of birth and were subsequently fed milk replacer twice daily. The weaning process began by withdrawal of the afternoon milk-replacer feeding. Milk was fully withdrawn, and the calf was considered completely weaned when it consumed 900 g of calf starter as-fed for 2 consecutive days. Blood samples were collected from all calves at 24, 27, 31, 45, 48, 52, and 66 ± 2.3 d of age. Early weaned calves took a variable amount of time to completely wean from milk replacer; therefore, data were also analyzed by comparing calves grouped by latency to completely weaned (fast=1 to 5 d; intermediate=6 to 8 d; slow=15 to 17 d). Slow-EW calves weighed less than either the fast- or intermediate-EW calves before initiating weaning. At 27 d of age, circulating neutrophils were greater among EW calves than CW calves. Moreover, fast-EW calves had lower neutrophil:mononuclear cell ratios at 45 d of age than other EW calves. Slow-EW calves had lower TNF-α concentrations from whole blood stimulated with endotoxin at 27 and 31 d of age compared with fast- and intermediate-EW calves. All EW calves had decreased neutrophil L-selectin at d 27 and increased neutrophil L-selectin at 31 d of age. At 31 d of age, neutrophil ß(2)-integrin was the greatest among the fast-EW calves. All EW calves had decreased neutrophil oxidative burst at 27 and 31 d of age. Three days after CW calves were weaned they had higher neutrophils, hematocrit percentages, and circulating cortisol than EW calves. In addition, 3 d after CW calves were weaned they had decreased neutrophil oxidative burst responses to Escherichia coli. Weaning, irrespective of age, suppressed many innate immune responses. In addition, early weaning transiently suppressed L-selectin expression on neutrophils; however, the immunological significance in the context of the resistance to disease is unknown because EW calves likely had greater protection from passively derived immunoglobulins when they were weaned. Finally, calves with lower BW around 24 d of age may not be suitable for early weaning programs as evident in the suppressed secretion of TNF-α from whole blood cultures during the week following the initiation of weaning.

Effects of changing milk replacer feedings from twice to once daily on Holstein calf innate immune responses before and after weaning.

The objectives of this study were to determine the effects of switching Holstein calves to once-daily feeding during the fourth week of life (24 ± 2.3 d of age; once-fed n=22; twice-fed n=22) on innate immune responses, and to evaluate whether carry-over effects occurred when the calves were weaned during the seventh week of life. Peripheral blood samples were taken immediately before the change in feeding strategy (24 d of age) and at 27, 31, 45, 48, 52, and 66 d of age and were analyzed for circulating cortisol, haptoglobin, total leukocyte counts, neutrophil:mononuclear cells, and hematocrit percentage. Heparinized whole blood was also stimulated with lipopolysaccharide (LPS) for 24h and the concentration of tumor necrosis factor-α (TNF-α) in the supernatant was analyzed. Neutrophil L-selectin and ß(2)-integrin expression were analyzed by flow cytometry. Simultaneous neutrophil phagocytic and oxidative burst responses to a heat-killed Escherichia coli were quantified by dual-color flow-cytometry. Treatment (once-daily or twice daily feeding) had no effect on pre- or postweaning performance. Once-fed calves tended to have more circulating neutrophils at 27 d of age, greater expression of L-selectin on neutrophils at 31 and 45 d of age, and greater intensity of phagocytosis at 45 d of age. Once-fed calves secreted less TNF-α in LPS-stimulated whole blood cultures at 45 d of age compared with twice-fed calves and this tended to persist through the immediate postweaning period. None of the other immune parameters differed after weaning between the preweaning feeding strategies. Consolidating calf milk replacer into one feeding during the fourth week of life was likely a mild and acute stressor, as evidenced by transient neutrophilia in the absence of suppressed functional capacities of neutrophils. Future research should address the mechanism and immunological significance of the persistent decreased TNF-α response in once-fed calves.

Prion protein N1 cleavage peptides stimulate microglial interaction with surrounding cells.

Microglia act as the protective immune cell of the brain. By surveying the tissue to identify and rectify problems, they function to maintain the health of brain cells. The prion protein N-terminal cleavage fragment, N1, has demonstrated neuroprotective activities in vitro and in vivo. This study aimed to elucidate whether N1 could modulate microglial function and, if so, determine the consequences for the surrounding tissue. Using a mixed neuronal lineage and microglia co-culture system, we showed that N1 stimulation changed overall morphology and metabolism, suggesting enhanced cellular viability. Furthermore, N1 induced an increase in Cxcl10 secretion in the co-cultures. Recombinant Cxcl10, administered exogenously, mediated the changes in the mixed neuronal lineage culture morphology and metabolism in the absence of microglia, but no effect of Cxcl10 was observed on microglia cultured on their own. Direct cell-to-cell contact was required for N1 to influence microglia in the co-cultures, and this was linked with restructuring of microglial membrane composition to include a higher GM1 content at interaction sites with surrounding cells. Our findings show that N1 can play a regulatory role in microglial function in the context of an inter-connected network of cells by changing both cellular interaction sites and cytokine secretion.

Supplementation of a Lactobacillus acidophilus fermentation product can attenuate the acute phase response following a lipopolysaccharide challenge in weaned pigs.

Lactobacillus acidophilus fermentation products have been used to improve the performance of nursery pigs. However, research on the influence of this supplement on health is lacking. This study was designed to determine if feeding a Lactobacillus acidophilus fermentation product to weaned pigs would reduce stress and acute phase responses (APR) following a lipopolysaccharide (LPS) challenge. Pigs (n=30; 6.4±0.1 kg) were individually housed in stainless steel pens with ad libitum access to feed and water. Pigs were weighed upon arrival, assigned to one of three groups (n=10/treatment), and fed for 18 days: (1) Control, fed a non-medicated starter diet; (2) Control diet with the inclusion of a Lactobacillus acidophilus fermentation product at 1 kg/metric ton (SGX1) and (3) Control diet with the inclusion of a Lactobacillus acidophilus fermentation product at 2 kg/metric ton (SGX2). On day 7 pigs were anesthetized for insertion of an i.p. temperature device, and similarly on day 14 for insertion of a jugular catheter. Pigs were challenged i.v. with LPS (25 µg/kg BW) on day 15. Blood samples were collected at 0.5 h (serum) and 1 h (complete blood cell counts) intervals from -2 to 8 h and at 24 h relative to LPS administration at 0 h. Pigs and feeders were weighed on days 7, 14 and 18. The supplemented pigs had increased BW and average daily gain before the challenge. In response to LPS, there was a greater increase in i.p. temperature in Control pigs compared with supplemented pigs. In addition, cortisol was reduced in SGX2 pigs while cortisol was elevated in SGX1 pigs at several time points post-challenge. White blood cells, neutrophils and lymphocytes were decreased in SGX1 and SGX2 compared with Control pigs. Furthermore, the pro-inflammatory cytokine response varied by treatment and dose of treatment. Specifically, serum TNF-α was greatest in SGX2, intermediate in Control, and least in SGX1 pigs, while the magnitude and temporal pattern of IFN-γ in SGX2 pigs was delayed and reduced. In contrast, IL-6 concentrations were reduced in both SGX treatment groups compared with Control pigs. These data demonstrate that different supplementation feed inclusion rates produced differential responses, and that feeding SynGenX to weaned pigs attenuated the APR to an LPS challenge.

Evaluation of immune system function in neonatal pigs born vaginally or by Cesarean section.

Full term crossbred sows were selected to study the interaction of the immune system, hypothalamus-pituitary-adrenal axis, and growth in pigs born by Cesarean section (c-section; n=4 sows) or vaginal birth (n=4 sows). Gestation length and birth weight did not differ between vaginal birth and c-section pigs (P=0.34 and 0.62, respectively). Blood and tissue samples were collected from 44 pigs at birth. Forty-five pigs were weaned at 13 d. On d 14, pigs received an i.p. injection of lipopolysaccaride (LPS; 150 microg/kg) or saline at min 0, and blood samples were collected at -20, -10, 0, 5, 10, 20, 40, 60, 90, and 120 min. Vaginal birth pigs had 21% greater average daily gain than c-section pigs on d 14 (P<0.01). Basal serum concentrations of adrenocorticotrophin (ACTH) and cortisol were greater in c-section than vaginal birth pigs at birth (P<0.01) but were not different at 14 d (P=0.99 and 0.80, respectively). LPS increased serum concentrations of ACTH, cortisol, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha; P<0.01) but the response was not different between c-section and vaginal birth (P>0.22). Basal serum concentrations of TNF-alpha tended to be greater in c-section vs vaginal birth pigs at 14 d (P=0.0967); however, basal serum concentrations of IFN-gamma tended to be lower in c-section pigs vs vaginal birth pigs at 14 d (P=0.0787). Expression of interleukin (IL)-6, IL-6 receptor, IL-1beta, and TNF-alpha mRNA did not differ between vaginal birth and c-section pigs but changed in an age and tissue dependent manner. Thus, reduced growth rate of c-section pigs is associated with altered immune system function.

Comparative aspects of the endotoxin- and cytokine-induced endocrine cascade influencing neuroendocrine control of growth and reproduction in farm animals.

Disease in animals is a well-known inhibitor of growth and reproduction. Earlier studies were initiated to determine the effects of endotoxin on pituitary hormone secretion. These studies found that in sheep, growth hormone (GH) concentration was elevated, whereas insulin-like growth factor-I (IGF-I) was inhibited, as was luteinizing hormone (LH). Examination of the site of action of endotoxin in sheep determined that somatotropes expressed the endotoxin receptor (CD14) and that both endotoxin and interleukin-I beta activated GH secretion directly from the pituitary. In the face of elevated GH, there is a reduction of IGF-I in all species examined. As GH cannot activate IGF-I release during disease, there appears to be a downregulation of GH signalling at the liver, perhaps related to altered nitration of Janus kinase (JAK). In contrast to GH downregulation, LH release is inhibited at the level of the hypothalamus. New insights have been gained in determining the mechanisms by which disease perturbs growth and reproduction, particularly with regard to nitration of critical control pathways, with this perhaps serving as a novel mechanism central to lipopolysaccharide suppression of all signalling pathways. This pathway-based analysis is critical to the developing novel strategies to reverse the detrimental effect of disease on animal production.

Citrus products decrease growth of E. coli O157:H7 and Salmonella typhimurium in pure culture and in fermentation with mixed ruminal microorganisms in vitro.

Orange peel and orange pulp are by-products that are included in feedlot and dairy cattle diets because of their low cost and high nutritional quality. The antimicrobial activity of citrus oils has been reported previously. The present study was carried out to determine whether these citrus by-products exert antimicrobial effects on Escherichia coli O157:H7 and Salmonella Typhimurium populations that are found in cattle gastrointestinal tracts. The growth of pure cultures (n = 3) of E. coli O157:H7 and Salmonella Typhimurium were reduced (p < 0.05) by addition of 2% (w/v) orange pulp and orange peel. Ruminal fluid was collected from cattle (n = 2) and E. coli O157:H7 or Salmonella Typhimurium were added. The addition of orange pulp and peel to in vitro mixed ruminal microorganism fermentations (n = 3) demonstrated that both orange pulp and peel reduced E. coli O157:H7 and Salmonella Typhimurium populations at least 2 log(10) in mixed ruminal fluid fermentations. Addition of orange pulp reduced (p < 0.05) E. coli O157:H7 populations from 10(5) to 10(2) colony-forming units (CFU)/mL and Salmonella Typhimurium populations (p < 0.05) from 10(4) to 10(2) CFU/mL. These results indicate that orange pulp and/or peel included in ruminant diets could decrease ruminal populations of foodborne pathogenic bacteria. Further research is needed to determine whether the antimicrobial activity of orange products against E. coli O157:H7 or Salmonella Typhimurium is expressed in the lower gastrointestinal tract.

High-yield production of a human therapeutic protein in tobacco chloroplasts.

Transgenic plants have become attractive systems for production of human therapeutic proteins because of the reduced risk of mammalian viral contaminants, the ability to do large scale-up at low cost, and the low maintenance requirements. Here we report a feasibility study for production of a human therapeutic protein through transplastomic transformation technology, which has the additional advantage of increased biological containment by apparent elimination of the transmission of transgenes through pollen. We show that chloroplasts can express a secretory protein, human somatotropin, in a soluble, biologically active, disulfide-bonded form. High concentrations of recombinant protein accumulation are observed (>7% total soluble protein), more than 300-fold higher than a similar gene expressed using a nuclear transgenic approach. The plastid-expressed somatotropin is nearly devoid of complex post-translational modifications, effectively increasing the amount of usable recombinant protein. We also describe approaches to obtain a somatotropin with a non-methionine N terminus, similar to the native human protein. The results indicate that chloroplasts are a highly efficient vehicle for the potential production of pharmaceutical proteins in plants.

Phosphorus supply influences heathland responses to atmospheric nitrogen deposition.

On an upland moor dominated by pioneer Calluna vulgaris and with an understorey of mosses and lichens, experimental plots were treated with factorial combinations of nitrogen (N) at +0 and +20kg Nha(-1)yr(-1), and phosphorus (P) at +0 and +5kg Pha(-1)yr(-1). Over the 4-year duration of the experiment, the cover of the Calluna canopy increased in density over time as part of normal phenological development. Moss cover increased initially in response to N addition but then remained static; increases in cover in response to P addition became stronger over time, eventually causing reductions in the cover of the dominant Calluna canopy. Lichen cover virtually disappeared within 4 years in plots receiving +20kg Nha(-1)yr(-1) and also in separate plots receiving +10kg Nha(-1)yr(-1), but this effect was reversed by the addition of P.

Visual documentation of ovine pituitary gland development with magnetic resonance imaging following zeranol treatment.

The objective of the current study was to determine whether magnetic resonance imaging (MRI) could be successfully utilized to document the effect of an oestrogenic anabolic agent on pituitary gland growth. The experimental animals consisted of two 1/2 sibling Suffolk wethers (castrated rams), which received either no implant (control, n = 1) or a 24 mg zeranol implant at day 0 and day 42 (zeranol; n = 1). Animals were anaesthetized with propofol and supported with oxygen during the MRI procedure. A mobile MRI unit with a 0.5 tesla (T), superconducting magnet was used to obtain 3 mm thick, non-contrast enhanced, T1-weighted (TR 500-600, TE25) sagittal, transverse and dorsal images of the pituitary gland. Sagittal images were recorded only when the mesencephalic aqueduct and infundibulum were distinctly visible in the same image. Pituitary glands were imaged at 14-day intervals for 70 days to determine if and when the anabolic effects of zeranol on pituitary gland growth could be visualized using MRI techniques. Three separate measurements of the pituitary gland dimensions made with the on-screen cursor were averaged to calculate pituitary gland dimensions and volume. A computer-assisted image analysis system and laser film images were used to determine pituitary gland area. Increases in pituitary gland volume for control and zeranol-treated animals were evident within 14 days, and by the end of the 70-day study, the increase in pituitary volume for the zeranol-treated animal was three times greater than that of the control animal. Overall, our results indicate that MRI technology can be successfully used to document the development of the pituitary gland in vivo. Application of knowledge gained from this novel approach to study the growth, development and function of endocrine glands over time, and within the same animal, will enhance human and animal endocrine diagnostic procedures.

Use of a novel oleaginous microorganism as a potential source of lipids for weanling pigs.

Weanling pigs are at risk of succumbing to illness due to an immature immune system and insufficient supply of available energy at the time of weaning. This study was aimed at determining whether oleaginous bacteria could serve as a source of lipids to weanling pigs. Weanling pigs were provided a daily dose of 1×109 colony fomring unit (CFU) = kg-1 of the novel oleaginous Enterobacter cloacae strain JD6301 or JD8715 (which is a variant form of JD6301 capable of producing extracellular triglycerides) via oral gavage for 5 d. Serum was collected every 6 h and intestinal samples were collected at 6 d. Providing pigs with JD6301 or JD8715 significantly increased serum concentrations of triglycerides and non-esterified fatty acids (NEFA) within 72 h. Additionally, the JD6301 and JD8715 strains were able to survive within the gastrointestinal tract throughout the duration of the study. These results suggest that providing Enterobacter cloacae can increase the serum lipids in the pigs, thus potentially providing an additional source of energy to animals during times of stress. This could potentially help improve the metabolic response of animals during times of stress.

Exposure to lipopolysaccharide in utero alters the postnatal metabolic response in heifers.

This study was designed to determine the effect of prenatal lipopolysaccharide (LPS) exposure on the postnatal metabolic response to an LPS challenge in beef heifers. Pregnant, crossbred cows ( = 50) were assigned to a prenatal immune stimulation (PIS; = 25; administered 0.1 µg/kg BW LPS subcutaneously 233 ± 15d of gestation) or saline treatment group (Control; = 25). Birth and weaning BW of calves were collected. There was not (> 0.05) a treatment × gender interaction for birth weight or 205-d adjusted weaning BW. Treatment did not affect (> 0.05) birth BW, but steers and heifers of PIS cows had greater ( < 0.02) 205-d adjusted weaning BW than offspring from Control cows. From the 2 prenatal treatment groups, heifer calves ( = 12 PIS, 11 Control) were identified at weaning (238 ± 15 d of age) to subsequently receive an LPS challenge. On d 0, heifers were fitted with indwelling jugular catheters and were moved into individual pens. On d 1, heifers (fed at 0600 h) were challenged i.v. with LPS (0.5 µg/kg BW) at 0 h (1000 h). Blood samples were collected at 30-min intervals from -2 to 8 h and again at 24 h relative to the LPS challenge. There was a treatment × time interaction ( < 0.01) for cortisol; PIS heifers had greater cortisol from 4 to 6.5 h post-LPS challenge ( < 0.001). There was a treatment × time interaction ( = 0.04) for serum glucose such that glucose was greater ( = 0.01) in PIS than Control heifers at 0.5 h, but was greater in Control than PIS heifers at 2, 4.5, and 7 h post-LPS challenge. This resulted in overall time ( < 0.01) and treatment ( < 0.01) effects such that Control heifers had greater glucose concentrations than PIS heifers. There was a tendency ( = 0.10) for a treatment × time interaction for serum NEFA, such that NEFA was greater in Control than PIS heifers at -2, -1.5, and 7 h relative to the LPS challenge ( ≤ 0.02). Also, there were time ( < 0.01) and treatment effects ( < 0.01) for NEFA with Control heifers having greater NEFA than PIS heifers. Serum BUN was affected by a treatment × time interaction ( < 0.01). Concentrations of BUN were greater in PIS heifers from -1.5 to -1 h, 1 to 2 h, at 4 h, and from 5 to 24 h relative to the LPS challenge. These results demonstrate postnatal growth and the metabolic responses of weaned beef calves can be significantly altered with a single exposure to LPS in utero.

Effects of dexamethasone treatment and respiratory vaccination on rectal temperature, complete blood count, and functional capacities of neutrophils in beef steers.

The objective of this research was to examine the effects of dexamethasone (DEX) treatment on various aspects of immunity following administration of a multivalent respiratory vaccine, using a model intended to mimic acute versus chronic stress. Angus × Hereford steers ( = 32; 209 ± 8 kg) were stratified by BW and randomly assigned to 1 of 3 treatments: 1) acute stress (ACU), in which 0.5 mg/kg BW DEX was intravenously administered at 1000 h only on d 0; 2) chronic stress (CHR), in which 0.5 mg/kg BW DEX was intravenously administered at 1000 h on d -3 to 0; or 3) control (CON), in which no DEX was administered. Steers were fitted with indwelling jugular catheters and rectal temperature (RT) recording devices on d -4 relative to vaccination and placed in individual stanchions in an environmentally controlled facility. Blood samples were collected and serum was isolated at -74, -50, and -26 h; at 0.5-h intervals from -4 to 6 h; and at 12, 24, 36, 48, and 72 h relative to multivalent respiratory vaccination at 1200 h on d 0. Additional blood samples were used to analyze complete blood cell count (CBC) and functional capacities of neutrophils. There was a treatment × time interaction ( < 0.01) for RT such that DEX treatment in CHR and ACU steers decreased RT on d -3 and 0, respectively. A treatment × time interaction ( < 0.01) was observed for total white blood cells (WBC), neutrophils, lymphocytes, and monocytes. Specifically, DEX increased WBC and neutrophils in CHR and ACU steers ( < 0.001) yet decreased lymphocytes in CHR steers ( = 0.02) compared with CON steers. Neutrophil concentration increased rapidly, within 2 h of the DEX infusion, in ACU steers. Monocytes transiently increased ( < 0.001) in response to DEX treatment in CHR and ACU steers. In contrast, eosinophils were greater ( < 0.01) in CON steers than in ACU and CHR steers. A treatment × time interaction ( = 0.004) was observed for interferon-γ, with CON cattle exhibiting greater concentrations than the ACU and CHR cattle at 5 h after vaccination, through d 3. Treatment also influenced ( ≤ 0.001) the expression of L-selectin on the surface of neutrophils. The percentage of neutrophils engaging in phagocytosis and the oxidative burst were suppressed ( ≤ 0.001) among only the CHR steers, whereas the intensity of the oxidative burst was suppressed ( ≤ 0.001) for both ACU and CHR steers. These data suggest that our model induced acute and chronic immunosuppression and defined the acute response to a multivalent vaccine in CON steers.

Serum blood metabolite response and evaluation of select organ weight, histology, and cardiac morphology of beef heifers exposed to a dual corticotropin-releasing hormone and vasopressin challenge following supplementation of zilpaterol hydrochloride.

The objectives of this study were 1) to determine if supplementation of zilpaterol hydrochloride (ZH) altered select organ weights, histology, and cardiac anatomical features at harvest and 2) to determine if administration of a corticotropin-releasing hormone (CRH) and vasopressin (VP) challenge following 20 d of ZH supplementation altered the blood chemistry profile in cattle. Crossbred heifers ( = 20; 556 ± 7 kg BW) were randomized into 2 treatment groups: 1) control (CON), without ZH, and 2) zilpaterol (ZIL; ZH at 8.33 mg/kg [DM basis] for 20 d). On d 20 of supplementation, heifers were fitted with indwelling jugular catheters. On d 24, starting at 0800 h and continuing until 1600 h, blood samples were collected at 60-min intervals. At 1000 h, heifers received an i.v. bolus of CRH (0.3 µg/kg BW) and VP (1.0 µg/kg BW) to activate the stress axis. Serum was separated and stored at -80°C until analyzed for a large-animal chemistry panel. Following the CRH/VP challenge, heifers were harvested on d 25, 26, and 27 (5, 6, and 7 d after ZH supplementation); BW, HCW, select organ weights, and histology were measured, and a total heart necropsy was performed. A treatment effect ( ≤ 0.02) was observed for Ca, K, creatinine, alkaline phosphatase, and sorbitol dehydrogenase. Zilpaterol-fed heifers had decreased ( ≤ 0.02) concentrations of Ca and K and increased concentrations ( 0.01) of creatinine ( = 0.02) during the CRH/VP challenge when compared to control heifers. Control heifers had greater ( ≤ 0.05) alkaline phosphatase and sorbitol dehydrogenase concentrations when compared with ZIL heifers. A treatment × time interaction ( = 0.02) was observed for P; concentrations were similar between treatments from -2 to 6 h postchallenge, and 7 h postchallenge CON heifers had decreased P. Liver ( = 0.06) and kidney ( = 0.08) weights as a percentage of BW tended ( ≤ 0.08) to be reduced in ZIL heifers. Gross liver weights tended ( = 0.08) to be lower in ZIL heifers. Other organ (heart, lung, adrenals) to BW ratios remained similar ( ≥ 0.41). These data suggest that there are some variations observed between treatments in terms of response to ZH supplementation and the CRH/VP challenge; however, in the environmental conditions of this study, limited variation in blood metabolic responses and organ weights suggests that the supplementation of ZH did not detrimentally alter the physiology of cattle.

Evaluation of the influence of prenatal transportation stress on GnRH-stimulated luteinizing hormone and testosterone secretion in sexually mature Brahman bulls.

This study examined the relationship of prenatal transportation stress (PNS) with exogenous GnRH-induced LH and testosterone secretion in sexually mature Brahman bulls. Brahman cows (n = 96; 48 were stressed by transportation at 5 stages of gestation and 48 were controls) produced a calf crop of 85 calves. All bulls (n = 46) from this calf crop were electroejaculated every 2 wk beginning at a scrotal circumference of 24 cm until sexual maturity (SM; i.e., 500 million sperm/ejaculate). The initial 11 control and 12 PNS bulls to reach SM were selected for the experiment. Within 7-21 d after reaching SM, bulls were fitted with jugular cannulas, from which blood samples were collected at 15-min intervals for 6 h prior to exogenous GnRH administration (10 ng/kg BW; i.v.) and for 6 h after GnRH. Serum concentrations of LH, testosterone, and cortisol were determined by RIA. Age and body weight did not differ ( > 0.1) between PNS and control bulls at the time of the experiment. All bulls responded similarly to exogenous GnRH, indicating no influence of PNS on LH or testosterone response to GnRH. More ( < 0.01) PNS (9 of 11) than control (3 of 12) bulls exhibited an endogenous pre-GnRH LH pulse, and more ( = 0.02) PNS (9 of 11) than control bulls (4 of 12) exhibited a pre-GnRH testosterone response to LH. The average concentration of testosterone during the 60 min (time -60, -45, -30, -15, and 0 min relative to GnRH) immediately preceding GnRH, tended to be greater ( = 0.07) in PNS (1.46 ± 0.30 ng/mL) than control (0.68 ± 0.28 ng/mL) bulls. During that time span serum cortisol was lower ( < 0.01) in PNS (4.00 ± 0.91 ng/mL) than control (7.8 ± 0.87 ng/mL) bulls. A treatment by time interaction ( = 0.03) affected testosterone concentrations from time -240 to 360 min relative to GnRH. Results from this study indicate that PNS did not affect pituitary responsiveness to GnRH or testicular responsiveness to GnRH-induced LH secretion.