OPPORTUNITIES THERE FOR CROSS-BRED ADVANTAGES

3 October 1997




OPPORTUNITIES THERE FOR CROSS-BRED ADVANTAGES

Cross-breeding could

improve dairying returns by

20% – more than the

return to be gained from

cross-breeding pigs. So why

is the technique not more

widely used for commercial

dairy production? John King

of Advanced Breeders

has the story

INCREASING use of Holstein genetics on Friesians has produced more milk in the first crosses and subsequent crossing has produced steady yield improvements. Some hybrid vigour – or heterosis – is demonstrated in the first cross, perhaps amounting to a gain of 2% or 3% in yield. Add to this a much larger breed difference in yield and the outcome has been a large boost to dairy performance.

Hybrid vigour is measured by performance of the first cross compared with the average of the parental breeds. But research to date has not been on the scale necessary to give precise answers as to the benefits of hybrid vigour.

Two most useful and recent experiments have come from Denmark and Canada. An attempt can be made to summarise these and earlier experiments.

Performance of first

crosses

Advantages have been found in:

&#8226 Yield of milk, fat and protein (a gain of usually 5% or better).

&#8226 Calf survival not usually well documented but very large in some experiments.

&#8226 Growth rate during the rearing stage.

&#8226 Reproduction – not always a large gain for heifers but calving intervals are usually improved.

&#8226 Herd life – surprisingly the most consistent feature of different cross-breeding experiments and amounts to an average of half a lactation or longer.

Hybrid vigour is not found in embryonic survival, resistance to mastitis or milk composition.

Most of the gains in individual characteristics are small but, when combined into a total economic assessment based on expected returns, the advantage amounted to about 20% in the Canadian experiment and 21% in Denmark.

The size of this gain is quite startling and in percentage terms probably rather more than the benefits found from cross-breeding pigs. Why then is crossbreeding in dairy cattle not more widely used for commercial production? The answer is simply that the reproductive rate of cattle can only sustain a proportion of first cross cows in the herd. So what can be done?

Criss-crossing and three-breed crosses

Genetic theory suggests that although most hybrid vigour is to be expected in the first cross, part of that gain will be retained in later crosses. It is possible to devise schemes in which two breeds are used in sequence on the first cross to provide replacements – criss-crossing – or, what might be better, three breeds in turn.

Experimental results on how advanced crosses actually perform are not clear. While in Canada there were no significant declines in performance compared with the first cross, in Denmark the losses were such as to wipe out the gains. The safest policy, therefore, seems to be to stick with the first cross.

A cross-breeding opportunity

Production of some cross-bred dairy cows can still be done while maintaining herd size. Traditionally many beef cross heifers have been sold from dairy to suckler herds but with BSE many suckler herds will now be breeding their own replacements.

An alternative enterprise might, therefore, for the dairy producer, be the production of specific first cross dairy heifers for sale to those dairy herds in the practice of buying in their replacements. Those breeds that can be used on heifers would fit in well.

A number of breeds are available which may prove suitable :

&#8226 The Jersey

Crosses of the Jersey bull on Holstein/Friesian cows (Jersians) were produced in Britain by ABRO many years ago and a few more recently by the West of Scotland College. They were shown to be excellent, robust dairy cows with a long herd life. When tried on a field scale they failed to gain popularity because the Jersey cross bull calves failed to make the grade for veal calves. Today the main obstacle would be the increase in fat percentage to be expected which would upset many quota allowances. For those few producing their own icecream, the Jersian would seem an excellent choice but for others some careful quota calculations are necessary.

&#8226 The Scandinavian Red Breeds

The Finnish Ayrshire, the Swedish Red and White and the Norwegian all offer attractions. While the average yields of these breeds will probably not equal those of the Holstein, the attention paid to disease resistance and reproduction in their selection plus the advantages of hybrid vigour will produce an attractive cross-bred cow. All three breeds have tested bulls suitable for use on heifers but the Swedish Red and White and the Norwegian perhaps have an advantage in that unwanted bull calves can be sent to the calf processing scheme and should realise an extra £21 compared with Holstein/Friesian calves.

&#8226 The Brown Swiss

Although many farmers have tried out Brown Swiss crosses, no summary is yet available to indicate how well they have performed.

Long-term prospects

The long-term answer to providing enough cross-bred replacements depends upon further advances in reproductive technology.

When cloning becomes a practical reality, there is every chance that the "Dollies" of the dairy cow world will be specific breed crosses. Perhaps rather nearer on the time-scale, the sorting of semen into predominantly X-bearing sperm would reduce the number of matings necessary to supply the needed numbers of cross-bred animals. Until that time, keeping a proportion of cross-breds in the herd would improve its longevity. &#42

Cross-breds can improve dairying returns by 20% – are you tempted?


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