Bottle raising males is hazardous

Sometimes our best intentions can lead to disastrous consequences.

This is the case when male orphans are bottle fed by people. With spring finally here, many farm animals and wildlife are giving birth.

Unfortunately, some are bound to be orphans.

“I want people to know of the dangers posed by bottle-raised males,” says Dr. Joe Stookey, an animal behaviourist at the University of Saskatchewan’s Western College of Veterinary Medicine.

Large male mammals are generally given the respect they deserve, but bottle-raised males are substantially more dangerous than those that are raised by their mothers.

“Bottle-raised males are simply ‘programmed,’ due to their hand rearing, to one day threaten their human rivals,” Stookey says.

This programming happens through a process called imprinting, whereby animals form strong, early attachments to their mothers.

Imprinting is crucial to species identity. For males, it directs mate choice when they reach sexual maturity.

“Males that have been imprinted onto another species tend to court the surrogate species that raised them,” Stookey says.

So if ram lambs are raised on nanny goats, they will try to mate with goats rather than ewes.

For human surrogates, this is where things can get dangerous. Humans are at risk of this misdirected attraction once hand-raised male orphans of any species reach sexual maturity.

In addition, these males will perceive other humans as competition, leading to aggression. Either situation could have deadly results for people, especially if the orphans are large animals.

Captive breeding programs for endangered species such as whooping cranes have found creative ways to skirt this imprinting problem.

Hatchlings are never allowed access to people and are fed with bird puppets.

The danger posed by dairy bulls is often attributed to their genetics.

However, their reputation for sometimes lethal aggression is likely caused by how they are raised rather than their genetic composition.

“Most dairy bulls are hand reared in isolation, which contributes to their behaviour towards humans when they become adults,” says Stookey.

He points to seminal research by Dr. Ed Price from the University of California at Davis, which tested the assumption that dairy bulls were inherently dangerous.

Price and colleagues hand-fed Hereford bull calves and kept them isolated, just as dairy bulls are typically raised. He found that Hereford bulls were just as dangerous when they reached maturity as dairy bulls are when raised this way. In contrast, the group-raised bulls were less aggressive toward people.

“If you must raise bulls, either raise them in groups or adopt them onto surrogate cows to rear until weaning and avoid imprinting them onto humans,” says Stookey.

Surrogate females provide the right imprinting and have the added benefit of the correct milk composition.

You can also reduce the time commitment because bottle feeding is typically necessary every few hours.

Finding a surrogate female can be challenging, but some people find them through social media and online marketplaces.

Researchers have recently discovered a way to induce lactation in mares and cows with a combination of hormone medications. Once lactating, these females can often successfully adopt the orphans.

The advantage of inducing lactation is that it avoids the biosecurity issues that come with introducing new animals and saves time, money and energy in acquiring a nurse female.

If there is no intention to breed orphan males, they should be promptly castrated, ideally before they mature.

Stookey knows first hand about the dangers of hand-raised orphans: “A few years ago, a dairy producer near my hometown was killed by their dairy bull. I wanted to help spread the word about the risk.”

Dr. Jamie Rothenburger is a veterinary pathology resident at the Western College of Veterinary Medicine, University of Saskatchewan. Twitter: @DrJamieR_Vet


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