Table 2.
A comparison of TST strategies whereby 10, 25 and 50% of calves were treated at 8 and 16 weeks either at random or according to lowest average daily bodyweight gain (ADG, kg/d), highest faecal egg count (FEC, eggs/g) or highest plasma pepsinogen (IUT/I). Values provided represent the percentage reduction in anthelmintic use relative to a population of calves treated strategically at 3, 8 and 13 weeks post-turnout. Additionally, the number of treatments shared between groups treated according to ADG, FEC or pepsinogen are provided. Within each treatment group a record was made of the number of individuals that had been treated at the first assessment that were also treated at the second assessment. The expectation of each occurring at random is provided as a comparison.
| Determinant criteria | Percentage of herd treated |
|||
|---|---|---|---|---|
| 10% | 25% | 50% | ||
| % reduction in anthelmintic usea | – | 93% | 83% | 67% |
| % of shared treatments between determinant criteria | Random | 10.0% | 25.0% | 50.0% |
| ADG-FEC | 20.0% | 32.0% | 55.6% | |
| ADG -Pepsinogen | 4.0% | 16.4% | 42.2% | |
| FEC-Pepsinogen | 7.0% | 27.6% | 48.6% | |
| % of first treated group to be selected for second dose | Random | 10.0% | 25.0% | 50.0% |
| ADG | 84.0% | 87.2% | 90.0% | |
| FEC | 26.0% | 39.2% | 70.0% | |
| Pepsinogen | 2.0% | 18.4% | 40.4% | |
Comparative to strategically treated calves (3, 8 and 13 weeks).