Dairy Crossbreeds - The Rare Breed

Crossbreeding, once unheard of in dairy circles, is becoming a more popular concept in an industry now dominated by purebred herds of Holsteins, Jerseys, Ayrshires and other milking breeds. Commonplace elsewhere in agriculture, from corn to pork, crossbreeding seeks to take advantage of the phenomenon known as hybrid vigour.

Hybrid vigour, also known a heterosis, is a measure of the differences between a crossbred and the averages of its purebred parents. If a difference is not positive enough to be greater than the best of the purebreds, crossbreeding may not be beneficial. Sometimes, though, overall economic merit or a combination of traits may be the justification for crossbreeding rather than one trait.

In dairying, most interest has been in trying to capitalize on heterosis to improve fertility and longevity rather than on milk production. Indeed, no breed outproduces Holsteins, which make up 92 per cent of our dairy cow population. No breed has milk component levels higher than those of Jerseys. There have been concerns, however, about increased levels of cull rates, fertility, inbreeding, and health and fitness traits in traditional dairy breeds.

Reports based on U.S. dairy herd improvement data in recent years have indicated a serious decline in dairy herd fertility. Canadian data don't seem to bear this out, at least not to such a serious extent. A recent paper published by Brian Van Doormaal, Canadian Dairy Network (CDN) general manager, showed the average 56-day non-return rate in Canadian dairy herds is 67 per cent, a small decline from 68 per cent previously.

He found a large difference in the non-return rate between heifers and first and later lactation cows. As well there was a large seasonal difference. The lowest was in winter when the most breedings take place. Recording and analysis of breeding data through milk recording, including confirmed pregnancies, would give a much more accurate estimate of the true situation.

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All pure breeds are by definition inbred to some extent. This distinguishes one breed's features from those of others. The level of inbreeding within the major dairy breeds has been increasing over the years, about 0.1 to 0.24 per cent per year depending on breed. According to reports published by CDN, Canada's major dairy breeds have an inbreeding level of 4.5 to 5.5 per cent.

Increased inbreeding in a population tends to concentrate undesirable recessive genes. That depresses performance accordingly. As two breeds become more and more inbred, the heterosis benefit from crossing members of each in a crossbreeding program becomes greater.

Yet little crossbreeding research has been done. Cost is a big reason and research trials can take 20 to 25 years to complete. Studies that have been completed do point to improvements in fitness traits, reproduction and lifetime profit. However, field data from herds actually practising crossbreeding are too sketchy to let us make solid conclusions or recommendations.

One study conducted at five research stations by Agriculture Canada, mostly using Holstein-Ayrshire crosses, confirmed several crossbred groups were equal to but not superior to Holstein in milk yield. This result was similar to those of earlier U.S. studies. They found crossbred strains were superior for lifetime performance and had a higher reproductive rate, or more calves born. Although heterosis was 16 to 20 per cent for most productive traits, actual performance did not exceed the level of purebred Holsteins.

Another study recently compared field data on the profitability of pure Holstein and Jersey breeds along with two and three-breed rotational crosses in New Zealand. Holstein-Jersey crossbreds make up 18 per cent of the national dairy herd there. Results showed crossbreeding among two or more breeds must be evaluated on a number of traits, mainly related to viability, and reproductive and productive performance. The Holstein-Jersey cross had the highest profitability per hectare.

New Zealand's genetic evaluation system allows comparison of cows on the basis of productive worth for fat, protein, milk and bodyweight. Fat, protein and herd-survival have positive values, and milk yield and body-weight have negative values. In the study, a high value for butterfat favoured the Jersey breed. A lower butterfat value favoured Holsteins.

Work done at the U .S. Department of Agriculture (USDA), comparing the merit of crossbred and purebred dairy cattle, found some evidence of positive heterosis values, reported Dr. Paul Van Raden at the 2001 Dairy Science meetings. General values were 3.4 per cent for milk yield, 4.4 per cent for fat yield, 4.1 per cent for protein yield, 0.7 per cent for somatic cell score, 1.2 per cent for productive life and 3.0 per cent for mature size.

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Numbers were based on November 2000 USDA genetic evaluations. There were records from only 16,810 crossbred cows compared to nearly three million dairy purebreds.

Since some of the greatest benefits of introducing crossbreeding may be in fertility and fitness traits, we need to do genetic evaluation in these areas. Programs such as DairyCOMP save some of these data but they haven't been brought into our genetic evaluation system.

We need to identify crossbred cows by breed composition in our milk recording system and retain that identification for two generations. The database retains parentage identification regardless of breed. This is the only way we can evaluate the results of crossbred matings, or even know how many of the various cross- bred cows there are. Many cows are not coded as crossbreds since they don't receive breed class averages or enter into any herd averages-crossbred dairy cows have no standard age, breed or lactation adjustments. We don't have enough identified crossbreds in the system to generate any sort of standard factors.

We do have systems in place to help select sires for purebred breeding. We need to generate more information if we want to make intelligent choices about crossbred dairy cattle too.

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Crossbreeding Poses Some Risk

A concern in choosing breeds for a crossbreeding program is that those with smaller numbers may be unable to keep up with genetic progress of more popular breeds. As well, if crossbreeding gained popularity, it would take active females out of the breeding population and slow genetic gain.

Marketing offspring from a crossbreeding program may be a concern too. Canadian dairy cattle have enjoyed tremendous export markets, mostly to the U.S. Buyers generally tend to discriminate against crosses to avoid the unknown variability. Some dairy producers, however, do want crossbreds.

The direction of a breeding program comes down to knowing your market and whether the direction is profitable.

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Crossbreeding 101: Heres How It Works

The goals of a crossbreeding program can be twofold. First, capitalize on traits that can be improved through heterosis and then select breeds with the strengths needed to make those improvements. First let's understand some of the terminology:

• F1. The first generation offspring as a result of crossbreeding. The Fl contains 50 per cent of the genes of the two parental breeds and expresses 100 per cent of the heterosis. Ideally the whole herd should be made up of Fls but such a herd can't produce its own replace-ments.

• F2. The second generation made up of intermating Fls. For example, if a Holstein-Jersey sire is bred to Holstein-Jersey cows, the characteristics that range all the way from pure Holstein to pure Jersey. This is too much variation for most herd breeding programs.

• Rotational Crossing. Some form of rotational crossbreeding is usually used to take advantage of heterosis but also have relatively consistent results. A two-breed rotation where the offspring are bred back successively to one of the parent breeds maintains 67 per cent of the heterosis expressed as F1s. A third breed could be introduced to make a three-way rotational cross that maintains 86 per cent of the possible heterosis. As well, a fourth breed can be included.

A three- or four-way cross could have a downside. If the additional breed or breeds are of lower merit than the first two breeds, you might give up more value than you gain. In theory, the three and four-way crosses should be the best performers. However, few trials have been able to distinguish a large difference in merit between two-way and three-way crosses.

Reproductive traits and factors affecting length of productive life appear to be improved regardless of the specific crossing program employed. Heterosis is also a factor in maintaining the yield traits in crossbred F1s and F2s to remain competitive with the higher yielding purebreds. As in purebred selection, the most common advice is to set goals for your herd. When choosing genetic material to add to it -usually sires-select the highest merit bulls available from the breed you select.

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Choosing Among Breeds to Produce Best Crosses

Ontario Holstein breeder Howard Cornwell of Oxford County has tried some crossbreeding using Brown Swiss sires on Holstein cows. This cross has given better herd life due to better breeding success, and better feet and legs, he believes. This is retained in the second generation when the F1s are back-crossed to Holstein.

The Brown Swiss has a similar body size and production level to the Holstein, and tends to retain body condition better than Holsteins, even in the F1 and F2 generations. The ability to retain higher body condition scores has been shown to have a genetic link to cow fertility.

Dr..Jack McAllister, who headed Agriculture Canada's crossbreeding trial, would consider a two-breed rotational cross, either Jersey-Holstein or Brown Swiss-Holstein, or a three-way rotational cross of the three breeds. Most people would start with a Holstein base.

Now a dairy extension specialist at the University of Kentucky, he suggests Canadians consider Holstein-Ayrshire. He points out the high quality of Canadian Ayrshires and the fact that the Agriculture Canada study showed a positive maternal effect due to the Ayrshire line.

The French breeds Montbeliarde and Normande have been used in some U .S. programs. There are large populations of both these breeds in France, and they are recorded and have a progeny proving program. The Montbeliarde is favoured for cheese production due to the high proportion of protein in its milk. The Normande is considered dual purpose, heavier and not as tall as the Montbeliarde. It gives less milk with higher components.

Ontario DHI Progress Report, 2001

INRA, France

This article first appeared in the October 2002 Ruminations column of the Ontario Milk Producer

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