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Guidance for veterinary practitioners, government animal health staff and dairy herd advisers on the Dairy Score.
Yes. An individual adult animal’s Score is derived from the herd’s base Score (which is determined by the lowest Score animal on its property of origin) when the individual was less than 12 months of age; plus any applicable calf credits.
The underpinning principle is that cattle 12 months and older keep their Score for life because the risk of adult cattle becomig infected is low. However, in some situations their Score may change as further information on their assurance becomes available. For example, in a previously Non‐Assessed herd, the Score for individual cattle may change if the herd is tested; because testing reveals additional information on the risk of BJD in the herd.
For example, where a NA herd has a Check Test with negative results, the Score for cattle within the herd is increased from Score 0 to Score 7.
During the transition period, some herds that test in the Control and Residual zones could theoretically revert to a lower Score (from Score 3 to Score 2) if there is subsequently found to be a high prevalence of infection in the herd.
Thus, in the literal sense, the Score for individual cattle (from a NA herd) is not strictly for life but until further assurance is demonstrated.
The base Score of the herd is the score of the lowest Score animal (ie. highest risk) in the herd.
In this situation, the presence of blood test positive cattle indicates that the herd may be infected and would be classed as Suspect (Score 1) until further testing is undertaken. A follow‐up confirmatory test, using either faecal culture or slaughter and histopathological examination, should be performed to clarify the true disease status of the herd. If Mycobacterium paratuberculosis is cultured or identified at post‐mortem from one or more animals, the herd may then be classified as Infected. The herd would then have a base Score of 1 until further approved control measures that reduce the risk are implemented.
If a herd is found to be infected and implements a State approved control program, the Score will be determined by the number of reactors found at the initial whole herd test (see Table 1 below).
For herds enrolled in the South Australian Dairy ManaJD program, please consult the State’s BJD coordinator in regard to the Score allocation during the initial whole herd testing phase.
Table 1 Guide to assigning a Dairy Score for individual animals in a herd by the proportion of blood test positive cattle found at an initial or subsequent whole herd test of cattle either two years and older or four years and older.
Check Testing needs to be repeated within 24 months to maintain the base Score for a herd at Score 7.
A Check Test is a test of 50 animals in the herd, biased to increase the probability of detecting infection. Animals should be selected so as to increase the herd level sensitivity of the Check Test by maximising the probability of fnding an infected animal. This is achieved by sampling those animals most likely to be infected and most likely to react to the test. This includes: animals in poor condition, older animals, and introduced animals.