16 January 1998

Spuds boost

milk quality

Manipulating milk quality

through feeding requires

care to ensure cows and

profits remain healthy.

Jessica Buss reports

FEEDING potatoes is helping one Somerset producer achieve his aim of high milk protein and low fat this winter from October to December calved cows.

Simon Darley who manages the 170-cow herd at John Bartletts Manor Farm, Odcombe, Yeovil, sells milk to Unigate and is still paid for constituents. This makes ensuring he maximises milk price is essential for maintaining profitability, so rations are carefully calculated.

However, Mr Darleys Axient nutrition consultant, Diana Allen, warns that any diet alterations to manipulate milk quality must be costed out and the response checked to ensure it is worthwhile. It can easily cost more than it gains.

Despite having adequate stocks of maize and grass silage, Mr Darley has bought potatoes to increase the starch fed and milk protein.

This has helped maintain milk protein at above 3.4% from the herd which averages 6878 litres, with 3422 litres from forage.

Mrs Allen says that although cereals could be an option to increase starch fed, inadequate storage rules these out.

The farm has storage for only one concentrate, a 28% crude protein blend forward contracted for six months at less than £120/t from Agriblend.

The blend contains 12% wheat, and is fed to high yielders at 5kg a cow in a total mixed ration with 10kg grainbeet (80% brewers grains and 20% sugar beet pulp) and 1.5kg of Regumaize, a molasses-based feed high in protein. The forage is half maize and half grass silage on a dry matter basis with 10kg of potatoes. No concentrate is fed in the parlour.

When cows were first housed good silage quality (12.5ME) indicated high yielders would only need 3.5kg of blend to yield 33 litres. However performance was not as good as expected.

A sample of the complete diet was sent for analysis and calibration of the feeder weigher checked. When both proved adequate, it was decided that the energy cows were gaining from silage was lower than its analysis, so concentrates were increased.

Potatoes were also introduced to replace some forage because the maize silage starch content was lower than hoped, says Mr Darley.

"Increasing milk protein can be expensive because it needs a high energy density ration, but this year Mr Darley made high energy grass silage, increasing ration energy density at low cost," says Mrs Allen.

"Silage was cut two weeks earlier than usual to ensure regrowth before the summer drought. Before cutting, fresh grass was analysed to check nitrate levels and ensure spring fertiliser had been used up. Grass was cut on Apr 30, wilted for two days and clamped, rolled with two tractors and sheeted in a day," explains Mr Darley.

Another option for increasing milk protein is to feed more protein, adds Mrs Allen. However, the 18% protein ration fed at Manor Farm is sufficient. "Increasing protein fed above 20% is not advised because it increases risk of laminitis, metabolic disease, infertility, and it increases costs."

Feeding digestible undegradable protein in the dry period can also increase milk protein. Mr Darley feeds dry cow rolls and reverse ratio minerals from three weeks before calving to supplement straw. Then 10 days before calving, cows receive some of the milking cow ration diluted with straw. Cows must also be at condition score 3.5 before drying off, he says.

Milk fat at Manor Farm is below last year, allowing more efficient use of quota. In November, fat was 4.34% and December 4.2%, compared with 4.47% and 4.21%, respectively, last year.

According to Mrs Allen, milk fat is lower because of the high quality silage. Although brewers grain have been shown to lower fat when fed at 15kg a cow, Manor Farm only feeds 8kg of brewers grains, and the sugar beet pulp included with it counteracts any effect on fat.

"It is difficult to alter fat% when only one blend can be stored as there are some feeds which could be added in small amounts to the ration to lower fat, particularly high oil products." However limited storage means this is not an option at Manor Farm.

The product P1034, which includes oils and palm kernel, gives a predictable fat response and strategic use at the end of the quota year can pay in terms of quota saving, she says.

She adds that Mr Darley could increase the oil content of his ration – currently 3.5% – as up to 6% oil can be fed safely in a mixed ration, and it can be cheap. But be wary of cheap compounds that are high in energy because of added oils, warned Mrs Allen.

Too much oil coats the fibre and prevents rumen bugs from digesting fibre effectively. Oil can also be toxic to rumen bugs, warns Mrs Allen.

In previous years at Manor Farm a higher proportion of maize silage – 75% of the forage – was fed, reducing fat%, but the cost of protein concentrate has increased making balancing maize expensive.

Feeding more concentrate and less forage can also increase milk fat, but she believes that approach is uneconomic.

Rapidly degradable starch such as maize meal also reduces fat, but care is needed to avoid acidosis. Naked oats could also be used to reduce fat, but little is available for animal feed.

Roadshows to profit

Dairy producers considering their future have the opportunity to attend one of six Axient/FW roadshows around England and Wales. The roadshows – Profitable Dairying – which way forward? will be held between Jan 19 and Jan 28. For locations and further details see Livestock, Jan 9, p45.

INCREASING PROTEIN

&#8226 Feed more starch.

&#8226 Make high quality forage.

&#8226 High energy density rations.

&#8226 Dry cow management.

REDUCING MILK FAT

&#8226 High quality forage.

&#8226 Brewers grains at a high rate.

&#8226 Increase oil content of diet.

&#8226 Source naked oats.

This years ration has kept milk protein above 3.4%, says Simon Darley.