Farmers in the US have begun implanting dairy cows with fertilised embryos of beef cattle, so they produce calves bred for beef rather than milk production. The idea is to make dairy farming more profitable.
Cattle have been bred for either milk or beef production. Beef breeds typically put on more muscle faster for less food than dairy cattle do, and the meat quality is better.听This makes beef calves far more valuable than male dairy calves, which are often disposed of immediately after birth.
Select Sires in Minnesota has trialled the implantation of beef cattle embryos and is now commercialising the technique. 鈥淚t鈥檚 in its infant stages,鈥� says Chris Sigurdson of Select Sires, but the company hopes the practice will become routine. 鈥淭hat鈥檚 the vision.鈥�
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If it does catch on,听it would also help reduce the industry鈥檚 substantial greenhouse gas emissions, says Alison Van Eenennaam at the University of California, Davis. 鈥淚t really alters the sustainability metric.鈥�
Dairy cows must keep having calves to maintain milk production. Female dairy calves can be used to replace ageing cows but male dairy calves aren鈥檛 nearly as valuable as breeds created specifically for beef production. Some farmers , despite efforts to end this practice, because it often costs more to raise them than they can be sold for.
In the UK, some of the male dairy calves that are sold are exported to Europe, where there is more demand for veal. This is opposed by welfare organisations because of the long journeys involved.
The number of male dairy calves being killed has been reduced by the growing use of reproductive technologies. Many dairy cows are now inseminated with semen from dairy bulls听sorted to remove sperm with a Y chromosome. This means the resulting offspring are nearly all female.
But if every calf were female, there would be too many. So, around half the time, dairy cows are instead inseminated with semen from beef bulls. The resulting cross-breed dairy-beef calves are more valuable for meat production than male dairy calves.
In the US, this is standard practice on large dairy farms and it is taking off in many other countries too. The problem is, demand for the cross-breed calves is falling in the US. 鈥淭heir value is declining sharply,鈥� says Sigurdson.
If beef embryos are implanted instead of just using beef semen, female dairy cows can produce pure beef offspring that are worth even more than the hybrids, more than making up for the higher costs of implanting embryos.
Cattle are responsible for around 10 per cent of all greenhouse emissions. Having a female cow that produces milk plus a cross-breed or pure beef calf in a year is much more efficient than feeding a dairy cow plus a beef cow for a year to get one beef calf, says Van Eenennaam. Dairy cows also produce less methane because they are fed richer foods, she says.
鈥淭hat鈥檚 a bigger impact in terms of emissions than anything that鈥檚 going to happen with genome editing,鈥� she says.
Phil Brooke from Compassion in World Farming says the organisation supports the use of sexed semen because it improves welfare 鈥� by reducing the number of unwanted males 鈥� as well as production. 鈥淚t ticks all the boxes,鈥� he says.
However, Brooke says the organisation is opposed to embryo transfer as it is a more invasive procedure than insemination and the larger size of pure beef calves could increase the risk of cows having difficulties during birth. Van Eenennaam says the procedures are equally invasive.
