SUMMARY
The distribution of 12 Class I ovine lymphocyte antigens (OLA) was examined in 4 flocks of sheep vaccinated against and/or challenged with Bacteroides nodosus, the transmitting agent of footrot.
In a flock of 47 Corriedales in New Zealand, which had been specially bred for resistance to footrot, a higher frequency (70.2%) of OLA type SY6 was found compared with 42.9% in 49 unselected Corriedale sheep (P = 0.001) The serum antibody response of 12 selected Corriedale ewes was compared with that of 12 unselected ewes of the same age after vaccination with a multivalent footrot vaccine and the selected ewes had significantly (P = 0.01) higher agglutinin titres than the unselected ewes, 7 weeks after vaccination.
In 3 trials involving 108, 120 and 135 Australian Merinos in Victoria, SYlb was associated with a reduction in the number of feet affected with severe footrot (P = 0.05, P = 0.01, P = 0.02) and in 2 of the trials there was a relationship between SY6 and high vaccinal agglutinin titres. This SY6 effect was evident in the first trial 31 days after primary vaccination (P = 0.05) and again 20 days later after secondary vaccination (P = 0.01). In the second trial, when the sheep were vaccinated 49 days after challenge, an association was again found between SY6 and high agglutinin titres (P = 0.05) after primary but not after secondary vaccination.
Exposure of 157 vaccinated Merino rams to B. nodosus during a footrot outbreak in New South Wales also showed an association between low infection and SY6 and SYlb.
Field challenge of 130 Merino wethers in another independent trial again showed significant associations between low footscore and SYlb at 4 weeks (P = 0.05), 7 months (P = 0.02) and 12 months (P = 0.05) after challenge.
The results suggest that lymphocyte antigen type is a significant factor in the susceptibility or resistance of sheep to footrot and the evidence reported here implies that SY6 is associated with high responsiveness to vaccination and SYlb with resistance to footrot.
Offspring of 4 Poll Dorset rams differing in eye muscle depth estimated breeding values (EBVs) were studied to determine sire, sex, and nutritional influences on cellular characteristics in the longissimus lumborum muscle. At 12 weeks of age, 62 lambs were individually fed a concentrate diet with or without protected nutrients ad libitum for 120 days while 39 lambs were grazed on improved pasture. Sire influenced the percentages of type 2A and 2B/2X myofibres, but not myofibre number or size. Progeny of the highest eye muscle depth EBV ram had less type 2A and more 2B/2X myofibres than the lowest ranking sire. At equivalent carcass weight, amount of RNA and protein in the longissimus muscle was influenced by sire, consistent with differences in eye muscle depth EBVs. Sex had little effect on muscle cellular characteristics, whereas lambs fed pasture had less type 1 myofibres than those fed concentrates and had less muscle RNA and a higher ratio of protein to RNA. The findings demonstrate differences in m. longissimus lumborum cellular characteristics in offspring of sires differing in muscle EBVs. The extent to which these differences relate to the Carwell muscle hypertrophy gene remains to be determined.
Successful protection against lumpy jaw disease in a colony of captive wallabies (Macropus eugenii) was induced by vaccination with a commercial ovine footrot vaccine. No mortalities attributable to lumpy jaw were observed in 69 vaccinated animals while six of 42 unvaccinated control wallabies died of the disease. Vaccinated animals exhibited significant increases in antibody titres to Bacteroides nodosus after the first and second doses of vaccine. Titres were measured by an enzyme-linked immunosorbent assay.
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