Effect of dose of Brucella abortus strain 19 in yearling heifers on the relative risk of developing brucellosis from challenge exposure with strain 2308

Yearling heifers were given SC injections of 10(8) (n = 40), 10(9) (n = 44), or 10(10) (n = 44) colony-forming units of Brucella abortus strain 19 (S19). The proportion of heifers with positive serologic test results at 1 month following vaccination increased as the dose of S19 increased. These proportions decreased with time, and all heifers had negative card, rivanol, and complement fixation test results within 4 months. Positive ELISA results persisted beyond 4 months in all three S19 dose groups; however, all heifers were ELISA-negative within 9 months after vaccination. Comparable lymphocyte transformation activity was stimulated by S19 dose of 10(9) or 10(10) and approximately half of the heifers in both groups had a positive stimulation index at 9 months. Immunity of the pregnant heifers was challenged 9 months after vaccination with 10(7) B abortus strain 2308 as follows: diluent controls (n = 69); 10(8) B abortus S19 (n = 40); 10(9) B abortus S19 (n = 39); and 10(10) B abortus S19 (n = 39). Tissue specimens from heifers were obtained at parturition and necropsy for culturing of B abortus. The proportion of heifers that developed brucellosis, ie, had positive culture results, increased as gestation days at challenge exposure increased. The effect of gestational age was controlled in the analysis using logistic regression. The relative risk of brucellosis was reduced to 0.38, 0.15, and 0.06 for B abortus S19 doses of 10(8), 10(9), and 10(10), respectively, compared with diluent controls at 1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of field strain exposure with new cases of brucellosis in six beef herds vaccinated with strain 19

Three hundred sixty cattle at risk in 6 beef herds known to include cows infected with Brucella abortus field strains were vaccinated with 3 x 10(9) colony-forming units of strain 19. Field strain exposure after vaccination was estimated by the number of cows with brucellosis that calved or aborted in the herd. As the number of exposures increased, the number of cows developing brucellosis increased, and 19 exposures in the 6 herds resulted in 9 new cases. The ratio of exposures to new cases varied from 1.0 to 2.0 in the 4 herds with new cases, whereas 2 herds with 1 and 3 exposures, respectively, did not have new cases of brucellosis. The correlation coefficient between the number of exposures and the number of new cases was 0.85, and the coefficient of determination suggested that 73% of the variation in new cases could be explained by the number of exposures in strain 19-vaccinated herds.     

Relationship of fetal age at conjunctival exposure of pregnant heifers and Brucella abortus isolation

Pregnant heifers were exposed by a conjunctival inoculation with 1 X 10(7) colony-forming units of Brucella abortus strain 2308. At parturition, milk and uterine samples from dams plus samples from dead calves were cultured bacteriologically for Brucella. The logistic regression probability of B abortus isolation increased from 0.22 to 0.90, as fetal age at exposure of heifers increased from 60 to 150 gestation days. Strain 2308 was recovered at parturition from 14 (64%) of 22, 17 (71%) of 24, and all 28 (100%) heifers that were at gestation days less than 127, 127 to 157, and greater than 157, respectively, at time of exposure. The number of infected heifers and the number of samples positive for B abortus were significantly increased as fetal age at exposure of heifers increased from gestation days less than 127 to greater than 157 (chi 2 greater than 10, P less than 0.005).     

Value of serologic reactions at 2 months following strain 19 vaccination of cattle herds with brucellosis

Non-reactor cows in a dairy herd and six beef herds quarantined because of brucellosis were vaccinated with Brucella abortus Strain 19 and tested by rivanol and complement-fixation (CF) tests. Cows with rivanol 100 and CF 80 test titers at 2 months post-vaccination (p.v.) were defined as test positives. In the dairy herd, 46 test positives were diagnosed as follows: 17 (37%) had field strain infection; 1 (2%) had a Strain 19 infection; an additional 18 (39%) were brucellosis reactors at 4 months p.v.; 10 (22%) had declining or negative serologic tests at 4 months p.v. In the beef herds, 58 test positives were diagnosed as follows: 19 (33%) had field strain infection; 5 (9%) had Strain 19 infection; an additional 21 (36%) were brucellosis reactors at 6 months p.v.; 13 (22%) had declining or negative serologic tests at 6 months p.v.

Since the majority of the test-positive cattle were diagnosed as either infected with B. abortus or brucellosis reactors, segregation of these cattle should reduce field strain exposure for the remaining cattle in the herd and therefore reduce the number of new cases of brucellosis.     

Relationship of strain 19 calfhood vaccination in beef herds and brucellosis reactor rates, duration of quarantine, and number of herd tests

Initial and cumulative reactor rates for strain 19 vaccinates and nonvaccinates were significantly (P less than 0.001) lower for beef herds containing variable proportions of vaccinates, compared with reactor rates in nonvaccinated herds. In addition, significant (P less than 0.005) reduction in cumulative incidence was observed in nonvaccinated and strain 19-vaccinated cattle as the proportion of vaccinates within the herd increased from 1 to 19%, 20 to 39%, 40 to 59%, and 60 to 100%. Duration of quarantine and number of herd tests were not reduced in herds with strain 19-vaccinated cattle. In herds released from quarantine, duration of quarantine and number of tests were positively correlated to proportion of the herd vaccinated. In nonvaccinated herds released from quarantine, effect of herd size was documented by strong positive (P = 0.042) correlation with duration of quarantine and slightly weaker correlation (P = 0.095) with number of tests.     

Effect of methotrexate exposure at late gestation on development of telencephalon in rat fetal brain

Pregnant rats were treated with 30 mg/kg of methotrexate (MTX) on gestation day (GD) 16, and fetal brainswere examined time-dependently. On GD 20, the appearance of the telencephalon in the MTX group was differentfrom that in the control group, and the major axis of the telencephalon of the MTX group was shortened,compared to that of the control group. In the sagittal section of the telencephalon in the MTX group on GD 20,histopathological findings of deformation and narrowing of the cerebral ventricle, the disturbance of thearrangement of the marginal cell layer of subventricular zone (SVZ) and thickening of telencephalic wall,cortical plate and ventricular zone (VZ)/SVZ were possibly attributable to neuronal migration disorders byMTX. Through all the experimental period, few pyknotic cells or TUNEL-positive cells were observed in theVZ/SVZ of the telencephalic wall and striatum in the control group. On the other hand, in the VZ/SVZ of thetelencephalic wall and striatum in the MTX group, pyknotic cells or TUNEL-positive cells were observed on GD17, and they increased significantly on GD18 and then decreased to the control levels from GD 19 onward. Thephospho-Histone H3-positive rate decreased remarkedly in the VZ/SVZ of the telencephalic wall and striatum ofthe MTX group on GDs 17 and 18, compared to the control group, but they recovered on and after GD 19. Theseresults suggested that there was a high possibility that development of the telencephalon in this periodrequired strong folic acid.     

Negative feedback control of luteinizing hormone secretion in prepubertal beef heifers at 60 and 200 days of age

Prepubertal beef heifers at 60 and 200 d of age, born in the fall or spring, were assigned randomly to one of three treatment groups: (1) intact = 1; (2) bilateral ovariectomy (OVX); or (3) OVX plus estradiol-17 beta(E2) administered in silastic implants (OVX + E2). Luteinizing hormone (LH) was measured in serum samples collected at 20-min intervals for 4 h from heifers on -1, +7, +21, +35 and +49 d after OVX. Luteinizing hormone concentrations increased in the serum by 7 d after OVX in heifers at both 60 and 200 d of age (P less than .001; time X treatment). Prior to OVX, the LH patterns were characterized by low levels and infrequent episodic pulses. By 49 d after OVX, the mean LH concentrations increased and the pattern changed to one of rhythmic LH pulses with a periodicity of 1 h (P less than .001; time X treatment). Estradiol-treated OVX heifers did not exhibit a postovariectomy rise in serum LH concentrations. Serum E2 concentration 49 d after OVX in OVX heifers was threefold greater than in 1 or OVX heifers, thus demonstrating that E2 exerted negative feedback on pituitary LH secretion in prepubertal heifers. There was no measurable difference in serum E2 concentrations between I and OVX heifers; however, the contrast in the concentration and pattern of serum LH between the two groups was dramatic and suggested gonadal factors in addition to E2 are involved in controlling LH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of brucellosis in Kuwait by vaccination of cattle,sheep and goats withBrucella abortus strain 19 orBrucella melitensis strain Rev. 1

Summary In Kuwait, approximately 12,000 diary cows were vaccinated with a reduced dose of 3×10⁹ Brucella abortus strain 19 and approximately 350,000 sexually mature sheep and goats with a reduced dose of 10⁷B.melitensis strain Rev. 1. Using the criteria of prevaccinal and postvaccinal incidences of antibodies, abortions, and human cases of brucellosis, the programme was very successful. Widespread vaccination of adult animals is the most effective method of controlling brucellosis among cattle, sheep and goats in many countries.

---

Resumen En Kuwait, se vacunaron aproximadament 12,000 vacas lecheras con una dosis reducida de 3×10⁹ organismos deBrucella abortus cepa 19 y approximadament 350,000 ovejas y cabras sexualmente maduras fueron vacunadas con una dosis reducida de 10⁷ organismos deB. melitensis opa Rev. 1. Utilizando los criterios prevacunales de incidencia de anticuerpos, abortos, y casos humanos de brucelosis, el programa fuvo gran exito. Ef método mas efectivo de control de la brucelosis bovina, ovina y caprina an numerosas paises es la amplia utilización de vacuna en animales adultos.

---

Résumé Au Kuwait, environ 12,000 vaches laitiěres ont été vaccinées avec une dose réduite de souche 19Brucella abortus (3×10⁹) et environ 350,000 moutons et chevres qui étaient matures sexuellement, one été vaccinés avec une dose réduite de soucheB. melitensis Rev. 1 (10⁷). Basé sur la présence d'anticorps, sur le nombre d'avortements et de cas de brucellose chez les humains avant et aprés vaccination, le programme a été un succěs. La méthode la plus effective pour contr?ler la brucellose chez les bovins, les ovins et les caprins dans beaucoup de pays et de vacciner sans exception tous les animaux adultes.

     

Influence of growth rate and exposure to bulls on age at puberty in beef heifers

Two experiments were conducted to test the following hypotheses: 1) exposure of beef heifers to sterile bulls increases the proportion of heifers attaining puberty by 14 mo of age and 2) rate of growth interacts with bull exposure to influence age at puberty in beef heifers. In Exp. I, heifers were assigned to one of two treatments: 1) heifers were exposed to bulls (BE; approximately 70-d period of exposure) or 2) heifers were isolated from bulls (NE) and served as controls. In Exp. II, heifers were assigned to either BE or NE treatments (175-d period of exposure to bulls) and were fed to gain at a moderate (MG; .6 kg/d) or high (HG; .8 kg/d) growth rate. Blood samples were collected twice weekly to determine concentrations of progesterone indicative of onset of corpus luteum function and puberty. In Exp. I a greater (P less than .05) proportion of heifers receiving the BE treatment than of heifers receiving the NE treatment initiated corpus luteum function by 14 mo of age. In Exp. II, there was a bull exposure x growth rate interaction (P less than .05). The effect of bull exposure was greater within the HG groups than within the MG groups. However, heifers fed to attain a moderate or high growth rate and exposed to bulls attained puberty at younger ages than heifers not exposed to bulls and fed to attain a moderate or high growth rate. Mean ages at puberty were 375, 422, 428, and 449 (pooled SEM = 8.6) d for heifers in the BE-HG, BE-MG, NE-HG, and NE-MG groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serologic and bacteriologic test results after adult vaccination with strain 19 in three dairy herds infected with brucellosis.

Milk culture data and serologic test results were evaluated after adult vaccination with Brucella abortus strain 19 in cattle of 3 large California dairy herds infected with brucellosis. Strain-19 organisms were isolated by culture of milk from 1.9% of the vaccinated cows. Isolation of field strain of B abortus varied directly with magnitude of complement-fixation (CF) and rivanol titers. At time of milk culture, 74% of cows from which field strain was isolated had CF titer greater than or equal to 160, compared with 58% of cows from which strain 19 was isolated. Cows with CF titer greater than or equal to 160 at 2 months or greater than or equal to 80 to 4 months after adult vaccination were more likely to be correctly classified as reactors (on the basis of subsequent milk culture results and/or persistently high serologic titer) than were cows with lower CF titer at these times. Cows from which B abortus strain 19 was isolated from milk were more likely to maintain persistent serologic titer than were cows from which neither strain of B abortus was isolated.     

Changes in urinary and plasma oestrone sulphate concentrations after induction of foetal death in mares at 45 days of gestation

Foetal death was induced in 10 Standardbred mares at day 45 of gestation by injecting 20 to 45 ml of hypertonic (24% W/V) saline into the conceptus at surgery. Ten mares underwent sham treatment and acted as controls. Blood and urine samples were collected every other day between days 30 and 45 post ovulation and at 0, 3 and 6 h relative to the infusion of saline in the treated mares, or sham treatment in control mares. Blood and urine samples were then collected daily between days 46 and 55 post ovulation. Urine oestrone sulphate (E1S) concentrations, measured by radioimmunoassay, increased between day 34 and day 36 of gestation in treated and control groups. In mares in which foetal death was induced, urine E1S concentrations declined post-operatively and were significantly (p less than .05) lower than controls by day 50. In plasma, E1S concentrations showed a major increase between days 36 and 40 in both groups. This was followed by a rapid decline after treatment in saline-injected mares, so that by day 48 plasma E1S concentrations in treated mares were significantly (P less than .05) lower than the controls. The results show that urinary and plasma E1S concentrations rise rapidly during early pregnancy, and are associated with a viable foetus after day 45 of pregnancy.     

Effects of stage of gestation and breed on bovine responses to vaccination with Brucella abortus strain 19.

Eighty-eight cattle were injected SC with 2.5 x 10(8) viable cells of Brucella abortus strain 19. All but 1 heifer became seropositive on the basis of the results of 7 brucellosis tests, and the proportion positive decreased with time. The proportion of cattle that were seropositive during a 20- to 67-week period after vaccination was as follows, in decreasing order: hemolysis-in-gel, 59%; buffered-acid plate antigen, 39%; ELISA, 16%; card, 10%; rivanol, 8%; cold complement-fixation, 7%; and automated complement-fixation, 5%. Using the serologic classification in Uniform Methods and Rules for brucellosis eradication, 7 cattle tested brucellosis-positive (2 suspects and 5 reactors). None of the 27 nonpregnant heifers tested positive. Of 18 heifers that were 84 to 135 days in gestation when vaccinated, 6 (33%) tested positive for brucellosis, compared with 0 of 13 and 1 (3%) of 30 heifers that were 11 to 78 and 145 to 253 days in gestation at vaccination, respectively (X2 = 12.07; 2 df; P less than 0.01). Neither breed (Angus, Hereford, Jersey, and Brahman) nor calf survival was related to brucellosis-positive results. Postpartum milk samples from 61 heifers and 24 tissues from 2 reactor cattle were culture-negative for B abortus.     

Immune response to Neospora caninum in naturally infected heifers and heifers vaccinated with inactivated antigen during the second trimester of gestation

The objective of this study was to compare the immune response to Neospora caninum in naturally infected heifers and heifers inoculated with a killed whole N. caninum tachyzoite preparation during the second trimester of gestation. Nine Holstein heifers were used in this study; three naturally infected heifers were born from seropositive dams, and six seronegative heifers were born from seronegative dams. Four seronegative heifers were subcutaneously vaccinated with a killed whole N. caninum tachyzoite preparation at weeks 13, 15 and 17 of gestation. A killed whole N. caninum tachyzoite preparation containing 45 mg of protein/5 ml dose was formulated with 70% of mineral oil adjuvant (13% consisting of Arlacel C, 85% Marcol 52 and 2% Tween-80). Similarly, two seronegative heifers (negative controls) were inoculated with mock-infected bovine monocytes in oil adjuvant. Humoral immune responses were tested by using an indirect fluorescent antibody test (IFAT) and an indirect enzyme-linked immunosorbent assay (ELISA) for detecting isotype specific antibodies. Cellular immune responses were assessed by lymphocyte proliferation test (LPT) and IFN-gamma production. N. caninum-specific antibody responses increased in immunized cattle by week 15 of gestation (mean reciprocal antibody titers 450+/-252), peaked at week 23 (mean 16,000+/-6400). Maximum antibody response in naturally infected heifers was observed at week 19 of gestation (mean: 3467+/-2810). Mean serum IFAT titers were significantly higher in immunized heifers compared with those in naturally infected heifers from weeks 17 to 25 (P < 0.05). Analysis of isotype specific antibodies in naturally infected heifers revealed a predominant IgG1 response in one heifer and a predominant IgG2 response in the other two. Similar titers of IgG1 and IgG2 occurred in immunized heifers. Control heifers remained seronegative throughout the study by IFAT and ELISA. Significant antigen-specific proliferation responses were only detected in naturally infected heifers in week 19 of gestation. Peripheral mononuclear blood cells (PMBC) from immunized animals produced IFN-gamma in similar concentrations to those of infected animals (P > 0.05). No abortion was seen in any experimental group; however, one calf from a vaccinated heifer died due to dystocia. All calves from vaccinated and control heifers were seronegative by IFAT at 6 months of age; in contrast, calves born from naturally infected heifers remained seropositive with titers > or = 200. Killed vaccine induced similar immune responses to those found in chronically, naturally infected cattle which did not abort; however, different immune pathways may be followed in vaccinated and natural infected heifers with differences in degree of protective immunity.     

Gonadotropin-releasing hormone-induced luteinizing hormone release in heifers: effect of nutrition during gestation

The effects of nutrition during the last two trimesters of gestation on GnRH-induced LH release were assessed in crossbred heifers. Heifers (n = 58) were allotted at 90 d gestation to one of three levels of an experimental diet fed at 1, 1.5 or 2% of BW to attain maternal BW loss, BW maintenance or BW gain, respectively, at parturition. Twenty-two heifers were injected (i.m.) once with 100 micrograms GnRH between d 14 and 1 before parturition, and 32 heifers were injected (i.m.) once with 100 micrograms GnRH between d 8 and 21 after parturition. Jugular blood samples were collected before and at 30-min intervals after GnRH for 4 h. Least squares means for BW change differed (P less than .01) among BW loss (-17.6%), BW maintenance (-6.0%) and BW gain (7.0%) heifers. Basal plasma LH concentration was not influenced by nutritional treatment and was similar before and after parturition for all groups. However, in response to GnRH, peak plasma LH concentration was greater (P less than .10) for prepartum than for postpartum heifers. Mean LH peak amplitude in prepartum heifers was approximately twofold greater (P less than .10) in the BW loss and maintenance groups compared with the BW gain group. Prepartum LH release was related inversely (r = -.64) to change in heifer BW and increased (P less than .01) as BW loss increased during gestation. After parturition, mean LH peak amplitude and area under the response curve averaged 50% less (P less than .10) in the BW loss and maintenance groups than in the BW gain group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutrition and the development of replacement heifers

Does the system work? After having been on a controlled heifer replacement program for 3 to 5 years, the entire herd will develop a short calving season resulting in more weaned calf weight per cow exposed to breeding. Wiltbank has reported on the advantage of feeding heifers for a selected target weight at breeding. Two groups of Brahman-cross heifers were fed to weigh 600 or 700 lbs at the beginning of the breeding season. They were pastured and fed similarly from breeding through weaning their first calves. The heifers that weighted 700 lb at breeding weaned 86 lb more calf per heifer exposed. They bred earlier and more became pregnant. The return above feed costs after 2 years breeding was $52 greater for the heavier heifers. Obviously, the benefits continue through subsequent calvings, emphasizing the importance of managing the replacement heifers for 3 years, through their second breeding and calving.