Studies with a bivalent infectious bronchitis killed virus vaccine.

Haemagglutination inhibition and virus neutralisation antibody responses of chickens given different vaccination programmes were compared. This was followed by a further experiment in which variously vaccinated laying hens were challenged at 30 weeks of age with two strains of infectious bronchitis virus of the "variant" Dutch D207 serotype. Chickens were given primary vaccinations to different strains of infectious bronchitis live virus during rearing and then injected at 16 weeks of age with inactivated oil adjuvanted virus vaccines prepared from either M41, GV101 or both viruses combined (bivalent vaccine). Antibody titres to M41 infectious bronchitis virus were high, and to D207 serotype low. in birds given Mass type vaccines only. In birds given an initial 'priming' with Mass type live vaccine and then 'boosted' with bivalent killed vaccine, high haemagglutination inhibition and virus neutralisation antibody levels against both the M41 and D207 serotypes of infectious bronchitis virus were stimulated. In another experiment, the ability of laying hens vaccinated according to this programme, to withstand challenge with two strains of virulent infectious bronchitis virus of the D207 serotype, was tested. Protection of egg production in vaccinated hens was found to be good and in all groups correlated with the individual hen haemagglutination inhibition titre at the time of challenge. The significance of these results with regard to the use of killed virus vaccines in laying hens and to the necessity to develop live virus vaccines from 'variant' strains of infectious bronchitis virus is discussed.

Infectious bronchitis in laying hens: the relationship between haemagglutination inhibition antibody levels and resistance to experimental challenge.

In three separate and unrelated experiments, in which vaccinated hens were challenged with virulent infectious bronchitis virus, the ability of individual hens to maintain egg production was related to their serum haemagglutination inhibition antibody titre at the time of challenge. It was found that, regardless of the vaccination programme used, the ability of laying hens to withstand infectious bronchitis virus challenge, as measured by the effect upon their egg production, is directly related to individual antibody titre at the time of challenge. In all three experiments, birds with antibody titres of >/=8 Iog2 (n = 82) did not show a significant reduction in egg production after challenge while those with titres within the range 5-7 log(2) inclusive (n = 126), over a period of 3 or 4 weeks after challenge, showed a significant reduction in their rate of egg lay, viz: 0.38, 0.33 and 0.47 eggs per hen per week, respectively and those with titres <4 log(2) (n = 101) showed, over the same time period, a reduction of 1.0, 0.45 and 1.16 eggs per hen per week, respectively. The ability of different vaccination programmes to stimulate uniformly high antibody responses to infectious bronchitis virus, and hence good overall protection of egg production was compared. It is concluded that the programme of choice is first to vaccinate the birds with a highly attenuated strain of live infectious bronchitis vaccine during rearing (H120), followed by the injection of a potent killed oil emulsion adjuvant vaccine at point-of-lay. The ability of the less attenuated H52 strain of live infectious bronchitis vaccine to interfere with response to killed vaccine was demonstrated in two of the three experiments. In both cases this interference was accompanied by an increased susceptibility of the hens to the effect of infectious bronchitis virus challenge on egg production.

Impaired response to killed Newcastle disease vaccine in chicken possessing circulating antibody to chicken anaemia agent.

Broiler breeder hens from the same hatch were reared as two separate flocks, one in the field and one in experimental accommodation. Both received the same vaccination programme using the same batches of vaccines. One flock showed serological evidence of infection with chicken anaemia agent starting at 8 weeks, the other starting at 22 weeks old. Newcastle disease mean antibody titres 4 weeks after killed vaccine injected at 18 or 19 weeks old were 4.6 logs lower in the flock showing chicken anaemia agent antibody from 8 weeks old than in the flock seroconverting at 22 weeks. Three other field flocks showing poor responses to killed Newcastle disease vaccines were examined and found to be chicken anaemia agent positive when vaccinated: a further three flocks showing good Newcastle disease antibody responses were shown to be chicken anaemia agent-antibody negative. No difference in response to infectious bronchitis or infectious bursal disease killed vaccines was demonstrable between the two trial flocks. The significance of chicken anaemia agent as a potential immunosuppressive agent for chickens is discussed with special reference to the control of Newcastle disease in laying and breeding hens.

Infectious bronchitis in laying hens: interference with response to emulsion vaccine by attenuated live vaccine.

Pullet chicks were reared in isolation; all except a control group were variously vaccinated against infectious bronchitis. Individual haemagglutination inhibition (HI) antibody responses were measured from 1 day to 38 weeks old when all birds were challenged with virulent infectious bronchitis virus, and egg production recorded for a further 5 week period. In the controls HI titres remained low until challenge: this caused a loss of 15.1 eggs/hen. In birds injected with oil emulsion killed vaccine (OEV) at 3 and 16 weeks old, the serological response was uniformly high but on challenge the loss in egg production was 2.9 eggs/bird. Birds given H120 live vaccine at 3 weeks and H52 live vaccine at 15 weeks old had a low (23%) individual rate of serological response to the latter, and egg production after challenge was 3.63 eggs/hen less than before. In birds given H120 live vaccine at 3 weeks and emulsion killed vaccine at 16 weeks old, 100% serological response to the latter occurred and egg production was unaffected by challenge. A further group also received H120 and H52 live vaccines at 3 and 15 weeks old respectively: however, they were then subdivided into four groups and injected with emulsion vaccine at either 17, 19, 21 or 23 weeks old. Their response to H52 vaccine was variable. The proportion of birds in each sub-group responding serologically to subsequent vaccination with OEV was 45, 65, 73 and 92% respectively. After challenge egg production in these four sub-groups was reduced by 1.92, 1.15, 0.94 and 1.55 eggs/bird respectively. It is concluded that response to oil emulsion infectious bronchitis vaccine can be impaired if it is used within 8 weeks of H52 live vaccine. Best results are achieved where birds are given a primary dose of H120 live vaccine at 3 weeks old followed by emulsion vaccine 12-16 weeks later. Use of the less attenuated H52 strain of live vaccine before emulsion killed vaccine is contra-indicated.

Immunization of pigs against the boar taint steroid androstenone.

Tissue concentrations of androstenone were measured in untreated control pigs and pigs immunized against 5 alpha-androst-16-en-3-one. Results confirmed that active immunization of male pigs against androstenone is unlikely to prevent the problem of "boar taint" in the carcass meat.

Induction of parturition in cows using betamethasone.

To avoid dystocia and calf mortality two groups of cows were induced to calve six or seven days prematurely. Group I consisted of none Hereford cross Friesian two-and-a-half-year-old recipient cows carrying Continental beef breed fetuses. Group 2 consisted of 10 four-year-old Continental beef breed cows carrying pure or crossbred fetuses of the same breeds. On day 280 of gestation a long-acting betamethasone formulation was injected into all 19 animals, followed five or six days later with an injection of short-acting betamethasone (15 animals) or prostaglandin F2alpha (one animal). Three cows calved before their second injection. Fourteen of the 15 animals given the short-acting betamethasone calved 26 to 70 hours later; the remaining animal was given prostaglandin at 72 hours and calved 36 hours later. The cow that received prostaglandin F2alpha instead of short-acting betamethasone calved after 11 hours. None of the calves in group I was born dead but three died within 36 hours. One calf was born dead in group 2. Cervical dilatation and slackening of pelvic ligaments were satisfactory in all animals. Although calf birthweights were between 39 and 60.5 kg, only two instances of dystocia were encountered. Thirteen of the 19 cows voided their fetal membranes within 12 hours of calving. Only two retained them for more than four days. All cows except two in group I showed good udder development and had a plentiful supply of colostrum at calving.

Protection of laying hens against infectious bronchitis with inactivated emulsion vaccines.

Commercially-reared laying chickens were challenged at 31 weeks of age with a virulent infectious bronchitis (IB) virus. They showed a sharp drop in egg production, despite having been vaccinated at four and eight weeks old with live attenuated IB vaccines to a recommended schedule. In contrast, similar birds that had been further immunised at point-of-lay with inactivated oil emulsion IB vaccine, or with a combined IB/Newcastle disease (ND) emulsion vaccine, showed no detectable fall in egg production after the same challenge. Unvaccinated susceptible specific pathogen-free birds challenged at the same time stopped laying almost completely. In the birds revaccinated with emulsion vaccine, measurement of haemagglutination inhibition antibody levels to IB showed their geometric mean titres to be raised from less than 5 log2 at the time of vaccination to over 10 log2 four weeks later. Their antibody levels did not rise further followining the IB challenge whereas in the birds that had not been revaccinated antibody rises to nearly 10 log2 were detected after the same challenge. For pullets vaccinated earlier with live IB vaccine, revaccination with inactivated IB or IB/ND oil emulsion vaccine at point-of-lay provides a safe and effective way of protecting their egg production against IB infection.

Apparatus for pasteurising teat cup liners between cows in a herringbone parlour.

In a herringbone milking parlour, teat cup liners were deliberately contaminated in turn with Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Sterp uberis. Contamination was achieved by filling the liners with milk that contained 10(6) test organisms per ml. After the clusters had been back-flushed with water at 85 degrees C for five seconds, normal swabbing methods failed to recover any contaminating organisms from the teat liners in 56 tests out of 64. After 10 seconds back-flushing no recoveries were made in the same number of tests. The apparatus developed to effect this back-flushing for a particular herringbone parlour is described, with details of its routine use during milking. For a 100-cow herd, the running cost of such equipment using a five-second back-flush is estimated at no more than 4 pounds per week and, in its present form, would not add more than 10 seconds to the total milking time for each cow. Improvements in design of the apparatus, and in milking techniques arising from the routine use of the device, are also considered.

Day-old vaccination of maternally immune turkeys against Newcastle disease.

Maternally immune day-old turkey poults were vaccinated against Newcastle Disease with La Sota live vaccine and, concurrently, with emulsion killed vaccine. After an initial fall in maternal antibody the haemagglutination inhibition (HAI) geometric mean titre (GMT) of these birds rose to log2(6) and persisted at that level for eight months. Re-vaccination of some birds at 10 weeks with the emulsion vaccine caused GMTs to rise to log2(11). Six months later these levels were at log2(7). Further emulsion vaccination at 28 weeks produced a good anamnestic effect, the titre rising to log2(12). The authors discuss the possible advantages of this programme of vaccination as a routine for the immunisation of both fattening and breeding birds.

Criteria for producing high quality animals for research.

The criteria for the breeding or purchase of high quality research animals in general, and of dogs, cats, monkeys, rats, mice, guinea pigs, and rabbits were discussed. The reasons for using high quality animals are: economic, accuracy and reproducibility of results, no effects due to the presence of pathogens, and reduction of human health hazards.

The effect of Marek's disease vaccination on the immunisation of day-old chicks against Newcastle disease, using B1 and oil emulsion vaccine.

Concurrent vaccination of one-day-old chicks with 2 x 10(5) 50% embryo infectious doses of live B1 Newcastle disease virus and 0.25 ml killed oil emulsion Newcastle disease vaccine produced satisfactory levels of circulating haemagglutination inhibiting antibody although the recipient chicks possessed titres of maternally derived antibody as high as 10 log(2). This effect was also seen when the chicks were given turkey herpesvirus for immunisation against Marek's disease. The satisfactory Newcastle disease antibody levels achieved by the vaccination programme did not fall below 5 log(2) during the first 20 weeks of the birds' 40 week life span. Re-vaccination with live B1 vaccine at 17-days-old did not boost antibody levels, but re-vaccination with oil emulsion vaccine at 9 weeks-old produced a rise from 7 log(2) to 11 log(2). These findings are considered to be significant in establishing and maintaining immunity to Newcastle disease for both broilers and laying hens, particularly in areas where the disease is endemic.

Immunisation of maternally immune turkey poults against Newcastle disease.

Turkey poults possessing maternally-derived antibody to Newcastle disease respond poorly, in terms of haemagglutination inhibiting (HAI) antibody response, to vaccination within the first 4 weeks of life. This unsatisfactory effect occurs both with live La Sota vaccine administered by intraocular/intranasal instillation or with killed oil emulsion adjuvant vaccine given by intramuscular injection. Re-vaccination of these birds with killed emulsion vaccine at 4 or 6-weeks-old indicates that they have become sensitised by either method of primary vaccination and results in the establishment within 4 weeks of high (8-9 log(2)) and prolonged HAI antibody levels. Further vaccination at 29-weeks-old raises the levels from 5 log(2) to 10-11 log(2).

Newcastle disease antibody levels in chickens after vaccination with oil emulsion adjuvant killed vaccine.

Chicks vaccinated with live Hitchner B1 Newcastle disease vaccine at 17 days old and subsequently re-vaccinated with an oil emulsion killed Newcastle disease vaccine at either 38 or 52 days old showed high and persistent HAI antibody levels for at least eight months. Re-vaccination of these birds at 17 weeks old caused a further rise in antibody level to log212 which, even at 38 weeks, had dropped only to log210. Chicken primarily vaccinated with oil emulsion killed vaccine at six weeks old developed HAI antibody levels after four to five weeks of log29 which re-vaccination four weeks later increased to log211. Chicken given killed aluminium hydroxide adjuvant Newcastle disease vaccine were serologically HAI negative 13 weeks after vaccination while those given the oil emulsion vaccine still showed an antibody level of log28. Groups of birds inoculated with oil emulsion vaccine and then, at 20 weeks old, challenged with virulent Newcastle disease showed a 100 per cent survival rate. The particular merits of oil emulsion killed Newcastle disease vaccine for laying and breeding birds are discussed.