Observations of the first service non-return rates of the hypoglycaemic, concentrate-fed dairy herds.

Fourteen dairy herds which had been subjected to the Compton Metabolic Profile test on a total of 29 occasions were selected from the records of the institute for Research on Animal Diseases, United Kingdom, because they had a wide range of mean blood-glucose concentrations. Two herds had to be rejected from the study because of inadequate breeding records, leaving 12 herds (26 profile tests) to be included. The first service non-return rate of each herd was calculated from the breeding records of 10 cows mated closest to the date of each profile test. These rates were positively related to the mean blood-glucose concentrations of the lactating cows (P less than 0.01).