Abstract
In response to farmer complaints about unfair penalties, for the presence of inhibitory substances in early lactation following the use of dry-cow antibiotic therapy, a two-part study was carried out to try and establish why these unexplained grades occur.
A survey of instructions supplied with each of 13 registered dry-cow products suggested that the directions for drug use were in some cases inappropriate for long-acting antibiotics.
A residue release study was conducted at the beginning of lactation following antibiotic therapy at various times during the dry period. The results showed, for the three dry-cow preparations studied, that treatment during the dry period, especially within six weeks of calving, could lead to detectable residues in milk from treated quarters.