How to maintain cows fertility and raise yields

1 February 2002

How to maintain cows fertility and raise yields

By Jessica Buss

IT is possible for herds yielding more than 9000 litres to achieve a calving interval of less than 385 days without a high culling rate. But it needs a dedicated approach.

Mark Glover, of the Kebir House Vet Group, North Yorks, told delegates how client Howard Pattison used milk progesterone testing and computerised records to maintain fertility results.

Mr Glover has concerns about the merits of extended lactations, so advocates a target calving interval of 375 days and a failure to conceive culling rate of less than 5%.

"Mr Pattison shows fertility doesnt have to go out of the window as milk yield rises." Yields in his 160-cow herd have risen from 8145 litres to 9315 litres between 1996 and 2001, but calving interval has remained at about 380 days.

This is coupled with a total culling rate of about 15% and failure to conceive culls at about 5%.

These results are achieved through taking milk samples and testing them for progesterone level using an on-farm test kit. The test requires no special equipment and the result is a visible colour change.

Routine sampling takes place on four days each week, with cows from 20 days calved sampled once a week for three weeks. Two high results and a low one indicate the cow is cycling normally.

Further samples are taken on alternate days from 15 days after the low result. A subsequent low result indicates the animal is either in heat or approaching heat, allowing targeted heat detection or blind insemination after 24 hours.

Alternate day testing resumes 15 days later when a low result indicates a return to service. After six high results the cow is pregnant. This is confirmed by manual pregnancy diagnosis at a minimum of 35 days post-service, he said.

Using progesterone testing successfully was also dependent on good record keeping, so action lists produced by a computerised recording program could be put to good use.

Despite the benefits, few producers are prepared to do the number of tests Mr Pattison does. But even taking a single milk sample for progesterone testing at 19-20 days post-service will identify about three-quarters of non-pregnant cows.

"A negative pregnancy diagnosis at this stage allows heat observations to be targeted," said Mr Glover.

Taking two milk progesterone samples at 19 and 24 days post-service will increase the detection rate of non-pregnant cows. Producers taking a sample on service day can identify the 9% of cows typically served at the wrong time. &#42

&#8226 Useful tool.

&#8226 Improve fertility results.

&#8226 Help keep culls low.

A delicate approach to cow fertility can maintain results as yields rise, according to Mark Glover.