14 June 1996

Low inputs + grass = cash – from high merit cows

Over 4000 dairy farmers visited Irelands Moorepark Dairy Research Centre to find out how high merit cows perform under different feed regimes. Sue Rider reports.

HIGH genetic merit cows can perform well on low input, grass-based diets. This was the central message at an open day last week at Irish advisory service Teagascs Moorepark Dairy Research Centre, Fermoy, County Cork.

Work at its Curtins Farm is comparing the performance of spring-calving high and medium genetic merit cows on different feeding systems (see panel opposite).

The trial, now in its second year, recognises that as the genetic merit of dairy cows increases so does their drive to produce milk and intake.

"When this extra feed requirement can be supplied from grazed grass it is possible to increase income a cow by 2.2-4.4p/litre of quota," said head of dairy husbandry, Kevin OFarrell.

But he acknowledged that level of improved efficiency would only be achieved if there were no detrimental effects on animal health, reproduction or cow longevity.

Fertility performance was the same for both genotypes in year one. But in the second year it was harder to get the high merit cows in calf, said researcher Sylvia Snijders. "Six weeks into this breeding season we have recorded no difference in the number of cows served in the first three weeks and calving to first service was no different," she said. But the non-return rate in the first three weeks for the high merit cows was 46% compared with 65% for the mediums (see table below).

Ms Snijders suggested the reduced fertility performance could be because high merit cows showed more silent heats – perhaps reflecting their lower condition score immediately post-calving. At this stage high merit cows lost an extra 20kg of bodyweight.

Average daily liveweight gain from mid-April to mid-December was similar for both genotypes (0.44 v 0.47kg a day). Body condition score changes were not as large for the high merit cows (+0.28 v +0.42) as for the medium. The high merit heifers put more of their bodyweight gain into frame.

Mastitis incidence was similar for the two groups of heifers in 1995 and somatic sell counts were consistently under 100,000/ml in both groups. But, at 37%, mastitis incidence was high for these first lactation animals and researchers said that highlighted a need for more effective mastitis control measures for replacement stock.

Lameness incidence, at 26%, was also high for a first lactation herd. It was attributed to poor housing.


Fertility performance 96

HighMedium

meritmerit

% cows served in

first three weeks8785

Calving to first service7173

Non-return rate in

first three weeks (%)6546

TRIAL FINDINGS

&#8226 Early results show that high merit animals can perform well in lower input production systems and should improve farm profit.

&#8226 Difference in milk production between the two genetic levels is similar to that which can be predicted from their genetic index.

&#8226 High merit animals produced more milk a cow (945kg) of lower fat (-0.31%) and slightly lower protein (-0.09%). Lower protein of high merit cows is a reflection of difference in genetic index for two groups (-0.1%) in favour of medium merit cows. Fat and protein yield was 17% higher, mainly due to the higher milk yield.

&#8226 High genetic merit cows perform equally as well on grass-based or high concentrate systems. Average response to the increased concentrates was 0.67kg of milk/kg of extra concentrates.

&#8226 The higher index heifers had a 5% higher grass intake for similar grazing management compared to their medium contemporaries. That gives them a 12% grass feed efficiency advantage.

&#8226 There was no significant difference between the two genotypes in terms of health and reproduction in the first year. Second year it was harder to get high genetic merit cows in calf – 46% non-return for the first three weeks against 65% for medium merit cows.

&#8226 Management during the trial was high, especially for grazing.

&#8226 There was little advantage to the more flexible system of grazing management in 1995. The drought in 1995 presented particular problems for the evaluation of this strategy.


Table 2: Comparisons of genetic levels across three feeding systems 1996*

High conc systemHigh grass intakeMoorepark feeding

MediumHighMediumHighMediumHigh

meritmeritmeritmeritmeritmerit

Milk (kg a cow)3,0773,3482,8243,0622,8213,208

Fat (%)3.763.763.913.953.993.59

Protein (%)3.303.273.353.303.293.28

Concentrate

(kg a cow)676676620620620620

Condition score2.92.53.22.53.12.5

Feed Grass + 3kg a cow a dayGrass onlyGrass only

Tot intake (kg DM a day)18-1916-1716-17

Stocking rate (/acre)0.45all available0.46

*Cumulative figures to June 1996.

FEED SYSTEMS

Three different systems were examined with each genetic level. System A (low input grass-based – standard Moorepark system) has a cow stocking rate of 3/ha (1.2/acre), an input of 350kg/ha of nitrogen (280 units/acre) and a planned 500kg of concentrates. Dr Dillon admits this would not be typical of all production systems but is the one recommended by Moorepark.

In System B (high concentrates) stocking rate and N input were similar to system A, but concentrate use was planned at 1t a cow.

In System C N and concentrate levels similar to A, but aim was to allocate unrestricted high quality grass and silage to the cows.

High merit cows eat 5% more grass than their medium merit contemporaries. They also have higher bite rates. Inset: Achieving high performance off high merit cows at pasture depends on securing high intakes of grass.