Colostrum-deprived calves (n = 34) were fed various amounts of colostrum, colostrum substitute, or milk replacer to establish a range in titer of passively acquired viral neutralizing antibody in serum. The calves were then challenge exposed intranasally with a virulent, noncytopathic bovine viral diarrhea virus (BVDV-890). After viral challenge exposure, calves were monitored for fever, leukopenia, thrombocytopenia, and diarrhea. In addition, viral isolation and viral titration were performed on specimens of nasal secretions, buffy coat cells, and serum obtained from the calves. Fever and systemic spread of virus were detected in calves that had viral neutralizing titer of 256 or lower. Calves that had viral neutralizing titer lower than 16 developed severe clinical disease manifested by fever, leukopenia, thrombocytopenia, and diarrhea. Seventy and duration of signs of disease decreased as titers of passively acquired viral neutralizing antibody increased. These results indicate that low to intermediate titers of passively acquired viral neutralizing antibody were not sufficient to fully protect calves from virulent bovine viral diarrhea virus.

Reference values for hematologic variables change with increasing age in cattle. Therefore, the purpose of the study reported here was to describe the peritoneal fluid constitutents of clinically normal young calves, and to compare cellular concentration and distribution in blood and peritoneal fluid of young calves with those of adult cattle. Eight healthy 8-week-old male Holstein calves and 8 healthy 3- to 8-year-old Holstein cows were studied. Peritoneal fluid was collected from calves along the ventral midline, 4-cm cranial to the umbilicus. Abdominocentesis was performed in the region of the lower right flank in adult cattle. Correlation analysis, using the Pearson's correlation coefficient, and regression analysis were performed for blood and peritoneal fluid data from calves. Data from calves were compared with those of cows, using Wilcoxon's rank sum test. A P value < 0.05 was considered significant for all tests. Calves had significantly lower blood eosinophil count (P < 0.003) and plasma protein concentration (P < 0.001) than did cows. Calves had significantly higher peritoneal fluid nucleated cell (P < 0.05) and mononuclear cell (P < 0.05) counts, but lower peritoneal fluid eosinophil cell count (P < 0.003) than did cows. For calves, nulceated cell and lyhocyte cell counts in the blood had a high, positive correlation with those of peritoneal fluid. However, the prediction equation for nucleated cell count accounted for a modest proportion of variability. A prediction equation for peritoneal fluid lymphocyte cell count was established. On the basis of results of this study, reference ranges established for peritoneal fluid constituents of clinically normal adult cattle may not be appropriate for interpretation of peritoneal fluid analysis of calves.

Owing to technical and ethical limitations, a substantial part of the knowledge about the pathophysiologic mechanism of the human diaphragm has been obtained from studies in which phrenic nerve activation was usually carried out by direct surgical exposure of the nerves in the neck of deeply anesthetized, mechanically ventilated animals. Novel information has been gleaned from such studies, but the restrictive conditions under which it was collected preclude reliable extrapolation. We, therefore, addressed the question of whether accurate electrophysiologic evaluation of the phrenic nerve-diaphragm pathway can be performed in intact, nonanesthetized calves. Transjugular phrenic activation was well tolerated, safe, specific, and able to achieve constant symmetric and supramaximal phrenic stimulations during prolonged periods. Eighteen noninvasive cutaneous and esophageal reception circuits were tested for their ability to record the diaphragmatic evoked potential. In addition, they were compared for specificity and reproducibility of the recorded potentials during prolonged periods of tidal or stimulated respiration. The best diaphragmatic potential was recorded from surface electrodes attached to the skin of the ninth and tenth intercostal spaces, using a xyphoidian reference. We describe a method that allows easy, long-term, and reliable electrophysiologic evaluation of the phrenic nerve-diaphragm pathway in intact, conscious calves. It is hoped that such a model will produce relevant novel information regarding pathophysiology of the diaphragm.

Receptors for opsonins, such as complement component C3b (CR1) and immunoglobulins, Fc receptors, interact with adhesion glycoproteins in mediating immune functions. Defects in expression of the adhesion glycoproteins CD11/CD18 results in severely hampered in vitro and in vivo adherence-related functions of leukocytes. Little is known regarding the effect of leukocyte adhesion deficiency (LAD) on ligand binding and receptor expression. We investigated the binding and expression of CR1 and Fc receptors by bovine neutrophils isolated from dairy calves suffering from LAD, compared with clinically normal (hereafter referred to as normal) age-matched calves. Neutrophils were also assayed for endogenously bound IgG and IgM and for exogenous binding of C3b, IgG1, IgG2, IgM, and aggregated IgG (aIgG), using flow cytometry. Luminol-enhanced chemiluminescence (CL) production in response to IgG2 opsonized zymosan was studied, and specific inhibition of CL was used to determine the specificity of IgG2 binding. Activation of protein kinase C with phorbol myristate acetate was used to determine the effect of cellular activation on expression of CR1. A greater percentage of neutrophils from normal calves bound C3b than did neutrophils from LAD-affected calves. Receptor expression was similar. Activation with phorbol myristate acetate resulted in increased expression of CR1 on neutrophils from normal and LAD-affected calves, but expression was almost twofold greater on neutrophils from normal calves. There was no difference between LAD-affected and normal calves in percentage of neutrophils that bound endogenous IgG and IgM. A greater percentage of neutrophils from normal calves bound exogenous IgM than did neutrophils from LAD-affected calves. Receptor expression for aIgG was greater on neutrophils from LAD-affected calves than on those from normal calves. Luminol-enhanced CL of neutrophils in response to IgG2 opsonized zymosan was not different between LAD-affected and normal calves. Results indicate increased binding and expression of Fc receptors for aIgG and decreased binding and expression for C3b and IgM on neutrophils from calves with LAD. Leukocyte adhesion deficiency may be compounded by added defects in the expression and binding of receptors for opsonins, such as C3b and IgM.

Objective--To evaluate the nematocidal effectiveness of the ivermectin sustained-release bolus throughout its 135-day delivery period. Design--Twenty-four naturally infected calves were randomly allocated to 1 of 3 equivalent experimental groups: group-T1 calves were untreated controls, group-T2 calves each received a sustained-release bolus on trial day 0 and group-T3 calves were rendered nematode-free and used at 35-day intervals during the study as tracers. One contaminated pasture was used for all principal calves for the 135-day grazing interval of the study. Calves of groups T1 and T2 were also artificially administered mixed infective nematode larvae at intervals during the grazing period, after which, all calves were confined to concrete for 21 days prior to necropsy. Animals--All calves were approximately 6 months old on trial day 0, weighed from 136 to 216 kg, and were of mixed breeding and sex. Procedure--At intervals during the study, feces from all calves were analyzed for nematode egg counts, and all calves were weighed and examined for bolus retention (T2 calves only). For nematode recovery, all calves were necropsied 21 to 22 days after removal from the contaminated pasture. Results--Parasitic populations of Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Bunostomum, and Oesophagostomum spp were significantly reduced in cattle treated with the ivermectin sustained-release bolus. Conclusion--The nematocidal activity of the ivermectin sustained-release bolus proved highly effective, with > 98% efficacy for all nematode species present.

A surgical technique was developed for implanting a flexible polyurethane cannula in a lateral ventricle in the brain of calves. Initially, measurements were made on 25 calves at necropsy to develop equations for calculating coordinates for cannula placement. The distance (cm) caudal, in the sagittal plane, from the coronal suture line to the center of a hole to be drilled in the parietal bone of the skull was: 0.73 + (0.00925 X body weight [kg]). The distance (cm) lateral from the midline to the center of the hole to be drilled was: 0.018 + (0.6464 X distance caudal). The depth (cm) from the surface of the skull to the dorsal surface of the lateral ventricle was: 2.29 + (0.0159 X body weight [kg]). Surgery was subsequently performed on 17 calves. A 5-mm-diameter hole was drilled through the skull with a hand trephine at coordinates derived from the aforementioned regression equations. A polyurethane cannula (total length, 30 cm; 1 mm ID; 2 mm OD) covering a stainless-steel 20-gauge blunt-tipped needle (stylet) was lowered through the brain and into a lateral ventricle at an angle of 20.5 degrees relative to the frontal bones of the skull. The blunt-tipped needle was then removed, and CSF was allowed to drip from the cannula to verify placement. One stainless-steel screw was inserted 0.6 cm medial, and another was inserted 0.6 cm caudal to the hole in the skull. The area around the cannula, bone screws, and hole in the skull was covered with dental acrylic (approx 2 cm in diameter) to stabilize the cannula. With minimal restraint of calves, injection of substances into and withdrawal of CSF from a lateral ventricle of the brain were possible in most calves for at least 6 weeks after surgery was performed.

A virologic survey was conducted on calves with diarrhea associated with bovine rotavirus (BRV) on a closed dairy farm. The BRV was detected from 32 of 219 (14.6%) fecal specimens repeatedly collected from 56 calves born during the years 1992-1993, regardless of whether they had diarrhea. Most of the 32 strains were isolated from fecal specimens obtained from 2-to 6-week-old calves. After electrophoresis of doublestranded viral RNA from the 32 strains, genomic RNA migration patterns were similar to those of the predominant BRV strains isolated at the same farm during the years 1990-1991. All representative strains were identified as G serotype 6 (G6) and P type 5 (P5) by results of the virus-neutralization test and polymerase chain reaction procedure. Thus, BRV had no change in genomic RNA electropherotypes and serologic antigenicities in a closed dairy herd over a period of several years.

Pharmacokinetic and pharmacodynamic variables of flunixin were studied in calves after IV administration of the drug at a dose rate of 2.2 mg/kg of body weight. The anti-inflammatory properties of flunixin were investigated, using a model of acute inflammation; this involved surgically implanting tissue cages at subcutaneous sites and stimulating the tissue cage granulation tissue by intracavitary injection of carrageenan. The actions of flunixin on exudate concentrations of several substances related to the inflammatory process, including proteases (metalloprotease [active and total] and cysteine and serine proteases), enzymes (lactate dehydrogenase, acid phosphatase, and beta-glucuronidase [beta-glu]), eicosanoid (prostaglandin E2 [PGE2], leukotriene B4, and serum thromboxane B2 [TXB2]) concentrations, and bradykinin (BK)-induced edema, were investigated. Flunixin had a long elimination half-life--6.87 +/- 0.49 hours--and volume of distribution was 2.11 +/- 0.37 L/kg, indicating extensive distribution of the drug in the body. Body clearance was 0.20 +/- 0.03 L/kg/h. Flunixin exerted inhibitory effects on serum TXB2 and exudate PGE2 concentrations, B-glu activity, and BK-induced swelling. Other enzymes and inflammatory mediators were not significantly affected. Pharmacokinetic/pharmacodynamic modeling of the data revealed similar mean concentration producing 50% of the maximal effect values for inhibition of exudate PGE2 and beta-glu and of BK-induced swelling (0.070 +/- 0.006, 0.064 +/- 0.040, and 0.061 +/- 0.030 microgram/ml), respectively). A lower concentration producing 50% of the maximal effect value was obtained for inhibition of serum TXB2 concentration (0.023 +/- 0.004 microgram/ml). Differences also were observed in equilibration half-life for these actions, suggesting the existence of 3 distribution compartments correlating with 3 sites of action--a central compartment and shallow and deep peripheral compartments. Pharmacokinetic/pharmacodynamic modeling proved to be a useful analytical method, providing a quantitative description of in vivo drug pharmacodynamics and indicating possible mechanisms of action.

Four colostrum-deprived calves each were immunized passively with antisera to whole Pasteurella haemolytica, leukotoxin-containing supernatants of P haemolytica, P haemolytica lipopolysaccharide, or newborn calf serum. Calves were challenge exposed intrabronchially with 5 X 10(9) P haemolytica, and 24 hours later, the resulting lesions were evaluated. The greatest protection against challenge exposure was provided by the antiserum to whole P haemolytica (lesion score = 6.3), whereas newborn calf serum provided the least protection (lesion score = 28.3). Calves that received antiserum to P haemolytica supernatants were moderately protected (lesion score = 16.3), and the antiserum to lipopolysaccharide provided minimal protection (lesion score = 21.8). Antibodies that were unique to whole P haemolytica antiserum and produced dense bands on immunoblots were detected to antigens at 66, 50, and 30 kd. Antibodies in the supernatant preparation that produced prominent bands reacted to antigens between 100 and 90 kd. Collectively, antibodies to these antigens may be responsible for enhancing resistance to experimentally induced pneumonic pasteurellosis. Antibodies to antigens in P haemolytica lipopolysaccharide provided little to no protection.

We quantified the effect of passive immune status on pre- and postweaning health and growth performance of calves raised in a beef production environment. Blood samples were collected at postpartum hour 24 from 263 crossbred calves for determination of plasma protein (PP) and serum IgG concentrations. Serum IgG concentration was classified as adequate (> 1,600 mg/dl), marginal (800 to 1,600 mg/dl), or inadequate (< 800 mg/dl). Plasma protein concentration was classified as adequate (greater than or equal to 4.8 g/dl) or inadequate (< 4.8 g/dl). Morbidity and mortality events in the study population were monitored from birth to weaning, and after weaning throughout the feeding period. The lowest concentrations of serum IgG and PP were observed among calves that experienced morbidity or mortality prior to weaning. Calves that experienced morbidity in the feedlot had lower 24-hour PP values, but had IgG concentration similar to that in calves that were not observed to be ill during the feeding period. Calves classified as having inadequate IgG concentration were at greater risk of preweaning mortality (odds ratio [OR] = 5.4), neonatal morbidity (OR = 6.4), and preweaning morbidity (OR = 3.2), compared with calves classified as having adequate IgG concentration at 24 hours. Calves classified as having inadequate PP concentration at 24 hours had a greater risk of morbidity (OR = 3.0) and respiratory tract morbidity (OR = 3.1) while in the feedlot, compared with calves classified as having adequate PP concentration. The effects of 24-hour passive immune status on calf growth were indirect through effects on morbidity outcomes. Morbidity during the first 28 days of life was associated with a 16-kg lower expected weaning weight. Respiratory morbidity in the feedlot resulted in a 0.04-kg lower expected mean daily gain. Thus, passive immune status at postpartum hour 24 was an important determinant of health before and after weaning, and was indirectly associated with calf growth during the same periods.