Milk Progesterone Determination as Applied to the Confirmation of Oestrus, the Detection of Cycling and as an Aid to Veterinarian and Biotechnical Measures in Cows

Abstract

SUMMARY The progress in the application of progesterone determination in milk-fat as a service to farmers, veterinarians and breeding stations concerned with fertility in cattle is described. Errors in oestrus observations (in problem herds an average 22%) are indicated by progesterone concentrations > 30 ng/ml milk-fat in samples taken on the day of artificial insemination (AI) (day 0). A substantial improvement is the double sampling regime where progesterone levels are evaluated on days 0 and 5 (or 6). An ovulatory oestrus with a chance of conception is expressed by progesterone levels 30 ng/ml milk-fat on day 5 (or 6), whereas progesterone levels below 30 ng/ml in both samples indicate acyclic or cystic ovaries; thus within one week after AI veterinary aid may be requested. For screening the ‘return’ or ‘non-return’ results (sample taken between days 20 and 22 after AI) the questionable range could be reduced, the discriminatory level being 90 ng progesterone/ml milk-fat. By monitoring the progesterone profiles post partum the individual variation in the onset of cyclic functions could be demonstrated. The progesterone-in-milk assay may help to differentiate between environmental and biological causes responsible for fertility problems. For example the elimination of management factors (false oestrus detection, missed oestrus) may largely improve the importance of breeding parameters (calving interval etc.). As an aid for veterinarians, progesterone determinations are not valuable for the classification of cysts, although the success of treatment may be followed up conveniently by laboratory diagnosis. In sophisticated biotechnical procedures such as embryo transfer the milk progesterone assay may be applied for selecting donor cows and for monitoring the success of superovulation.