4 August 2000


Falling fertility, reducing

silage yields, milk protein

production and grazing

management were among the

topics discussed at a

Moorepark open day, held at

its Solohead Farm, Co

Tipperary. Jessica Buss reports

REDUCING the number of replacements needed in a block calving herd with declining national fertility means achieving a high six-week in-calf rate.

"Calving rate is declining year on year and eventually it could reach 30% as in the US," said Teagascs John Mee at the open day attended by 5000 visitors.

"There is an economic cost to this: Keeping 10% extra heifers reduces margin by 0.9p a litre," he said.

Falling cow fertility is most likely a result of increasing milk yields, said Teagasc researcher Frank Buckley. But the range in performance seen in early results from a study on 72 Irish dairy herds, indicate that there is scope for management to improve and compensate (see table).

"A fertility index is required for all dairy sires." Then selection of sires could be based on production and their progenys ability to get in calf.

A Teagasc study revealed differences in milk yield, condition score and pregnancy rate between sires daughter groups.

Milk yield and liveweight were both negatively correlated with pregnancy rate, but condition score was positively correlated with pregnancy rate. Both liveweight and condition score may be important traits in indirect selection for improved reproductive performance.

Range in performance

But there are large ranges in fertility performance, so reproduction management is important for high merit animals, said Mr Buckley.

Submission rate in the first three weeks of the service period was one example of performance differing widely between herds. While the top herd achieved a 96% submission rate, the worst was just 33%. The target for submission rate should be 80%, but even the average was below that.

Wide variations in results were also evident in pregnancy rate to first service and infertile rate.

But producers can take action to minimise these costs by focussing on the six-week in-calf rate at the beginning of the breeding season, said Mr Mee. This will also mean replacement heifers can be born within a 42-day period.

"Put more cows to the bull early in the service season, then you will have a better chance of getting them in calf within six weeks," he advised.

"Even when conception rates cant be increased, this will provide more opportunity to get them in calf as its a combination of conception rate and submission rate."

He believes producers should set a target submission rate of 90% in six weeks. "Watch cows for heat over a three week period before starting serving, use tail paint and examine those not bulling seven to 10 days before serving begins. It may also help to induce heat in later calvers."

Retrain for AI

Producers using DIY AI should also consider retraining, as it is proven to increase conception rates by 5-10%. It is important that producers inseminating small numbers of cows or those turning the bull in so they dont know their conception rates go for retraining, he said.

But even when conception rates at scanning 30 days after service look good, he advises caution with results. A study has shown that 5-10% of these pregnancies can be lost through late embryo mortality. &#42

Fertility study results

Average Range

Milk yield (litres) 5642 4796-7139

Fat (%) 3.84 3.58-4.05

Protein 3.33 3.17-3.5

Pregnancy to first service (%) 48 26-73

Submission rate (%) 70 33-96

Services/conception 2.1 1.3-2.8

Infertile rate (%) 14 0-34

Getting more cows in calf in the first six weeks of serving should be a prority, says John Mee: Cows at Solohead Farm, Co Tipperary, have tail

paint applied to improve submission rates.

See more