12 June 1998

Fertility worse in large herds, reveals NMR

DAIRY cow fertility and cell count results are worse in large herds and those which have expanded rapidly, according to NMR data.

As herd size increases so does yield a cow, but services a conception are progressively poorer (table 1). Herds of over 200 cows serve cows 1.89 times a conception, compared with herds below 50 cows using 1.54 services a conception.

Cell counts are highest for herds with fewer than 50 cows, at 174,000/ml, are lowest at 156,000 cells/ml for 101 to 150-cow herds and increase to 170,000/ml in herds with over 200 cows.

Larger herds appear to serve cows earlier and, therefore, achieve a similar average for days to first service and calving interval as smaller herds. But this points to less accurate fertility management, including poorer heat detection and use of records, in large herds where there may be more cows a man, says NMR.

Rapid expansion results in higher cell counts and services a conception (table 2). The increase in services from 1.77 to 2.06 a conception could be costing £10.50 a cow in semen for herds adding over 100 cows in the year, adds NMR.

Table 2: Service and cell

counts for increasing cow

numbers over 12 months

Extra Cells/ml Serves a

cows conception

100+ 195 2.06

70+ 169 1.94

60+ 170 1.91

50+ 164 1.87

40+ 164 1.83

30+ 170 1.79