Combinations of oestrus detection, ovarian palpation and milk progesterone assays were used to monitor pre-service reproductive status of cows in two dairy herds over two successive years. Non-cyclical cows were identified as having no luteal tissue in their ovaries on two occasions 10 days apart. Absence of luteal tissue was determined by the presence of basal mild progesterone initially followed either by a repeat of this result or by failure to palpate a corpus luteum per rectum. In the period 32 to 56 days post partum the number of non-cyclical cows on farm A years 1 and 2 was eight out of 31 (25 . 5 per cent), and 10 out of 62 (16 . 1 per cent) and on farm B years 1 and 2 was 10 out of 68 (14 . 7 per cent) and 11 out of 85 (12 . 9 per cent) respectively. The farm A herd was high yielding, (average lactation 6380 litres), whereas the farm B herd was of average yield (4717 litres). In both herds 60 day milk yield was not related to cyclical status of pre-service cows. There was however a trend toward a greater proportion of young cows being non-cyclical. With the exception of a prolonged calving to conception interval for farm A in year 1, whether a pre-service cow was cyclical or not had no effect on when the cow was first served or on when the animal conceived. The routine incorporation of pre-service monitoring to herd fertility control programmers may however be of value in recognising the incidence of non-cyclical cows and giving an early indication of oestrus detection efficiency.
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