13 February 1998

FEED AND FERTILITY…

Careful feeding

management can help

safeguard the fertility of

high-yielding, spring calving

cows. Jessica Buss reports

TO MINIMISE the negative effect of turnout on fertility, one 9400-litre herd will restrict grazing times for non-pregnant cows this spring.

To supplement their low grass intakes these fresh calvers at John Rounds 175-cow herd, Elmoreback Farm, Gloucester, will be fed a mixed ration of maize and grass silage and concentrates.

"Last year cows milked well off grass and although fertility was not as bad as the previous spring, it was not as good as in winter," explains Mr Round. These high yielders must achieve good dry matter intakes of the correct ration spec in the breeding season to ensure they get in calf.

"Cows can produce 30 litres at grass, but it cannot support 45-litre cows, and we have some cows peaking at 60 litres."

January calvers, served after turnout last year, needed 2.38 services a cow, February calvers 2.5 a cow, and March and April calvers 2 a cow. Those calving in May were easier to get in-calf, requiring only 1.8 services a cow, explains Mr Rounds ADAS nutrition consultant Pete Kelly.

Mr Round aims to keep the calving interval below 390 days. He is not concerned about letting cows slip up to a month because of the herds all-year-round calving pattern and high average yield. Actual calving interval for the last year is 377 days.

"Before we started complete diet feeding, fertility was worse. Although complete diet feeding initially improved yield slightly, the improvement in fertility was more dramatic."

To improve fertility this spring and help maintain lactations, Mr Round plans to change the way he groups cows. The high yielding group last year included cows up to 200 days calved, but now it will only include cows not in-calf, up to about 100 days calved.

These fresher cows will be fed a ration of maize silage and concentrates. Fresh grass will be restricted to 4-5kg of dry matter to maximise intake of the mixed ration. High quality forage with good intake characteristics is vital, he adds.

"On the winter diet the best cows eat 32kg DM – 70kg fresh weight. It is impossible for cows to eat that much fresh grass – it would need intakes of over 200kg fresh weight."

In-calf cows will graze grass and, because concentrates cannot be fed in the parlour, they will receive a buffer feed of forage and concentrates. Many of these in-calf cows will still produce over 30 litres and are typically dried-off giving 23-30 litres.

To maximise intakes in summer, cows are housed in hot weather. High yielding cows eat little when standing in the sun and show few signs of bulling, explains Mr Round. In these circumstances, cows come in at mid-day or only graze at night, when its cooler.

The high yielders spring and summer diet will include sugar beet pulp to add fibre, and low protein maize silage with little or no grass silage, to lower the crude protein of the diet, and so balance the high protein grass.

Mr Kelly adds that while there is little scientific evidence to support the negative effect of excess rumen degradable protein on fertility, there is circumstantial evidence. Checking the protein content of fresh grass once a week will ensure protein levels are kept low enough, advises Mr Kelly.

"We want a diet below 20% crude protein at grass to ensure good fertility. Mid-April grass can be 28-30% crude protein, so on a diet of grazed grass high yielding cows will receive too much protein." Cows of average yields would cope with the excess protein better, because they can afford to use energy for it, and their fertility is less likely to suffer.

&#42 Monitoring results

Mr Round monitors fertility using breeding wall charts, which give a visual picture of cow services quickly, and he uses NMR Herdwatch to calculate conception rates.

Mr Kelly says that submission rates – cows served within the desired period after calving – are often low when cows are at grass because of poor heat detection.

The farms Herdwatch figures show that heats are observed well with the days to first service similar to winter but conception rates are low. Cows are observed as they are walked in from the fields twice a day and checked at night.

Mr Kelly says that where heat observation is poor, producers should consider using a beef bull for two months, when black-and-white heifers are not needed.

But Mr Round breeds all cows pure so that he can gain from the genetics in the herd which currently averages £42 PIN, with calving heifers now averaging £70 PIN. Excess heifers are sold. &#42

SPRING FERTILITY

&#8226 Avoid sudden ration changes.

&#8226 Ensure high yielders eat adequate DM.

&#8226 Feed correct level of crude protein in rations.

Dry cow management

Dry cow management has also helped improve fertility in the last year, with services a cow now reduced to 1.82 over 12 months compared with 2.02 a cow a year ago.

John Rounds ADAS nutrition consultant Pete Kelly says the herd now has a management programme for dry cows which has reduced difficult calvings, milk fever incidence and helped cows reach peak yield more quickly after calving.

Dry cows stay inside or on bare pasture and are fed a ration which includes straw, maize silage, grass silage and 2kg of concentrate for the last two to three weeks before calving.

Glos producer John Round (left) and ADAS consultant Peter Kelly will restrict access to grass to ensure good fertility of high yielders this spring.