Pig farmers are permitted to house sows in farrowing crates for four weeks to protect piglets from being crushed by their mother and stop sows fighting with each other.

OPINION: Animal rights activists turned their attention to the pig industry to highlight the use of farrowing crates.

I guess there was no bobby calf footage yet available for them.

The footage, which showed a sow in a farrowing crate is standard practice among indoor pig breeding farms and let's be clear: the pig farmer in question has done nothing illegal.

Under the rules, farmers are allowed to use the crates for four weeks while the sow feeds her piglets until they are weaned.

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Last year, the National Animal Welfare Advisory Committee (NAWAC) reviewed the crates and found that it was the best system available.

There are good reasons for this. A sow can weigh up to 300 kilograms, which is more than enough weight to accidently kill her piglets if they are underfoot either by stepping on them or crushing them and the farrowing crate prevents this from happening.

It also prevents fighting between sows for food and competition space, which often occurs when they are grouped together and also helps the farmer spot and isolate sick animals.

Groups like Safe want them banned, but consider what that would mean for the pig industry.

About 30 per cent of the industry farms their pigs outdoors so 70 per cent of the industry would have to change their system. Many would be unable to do so because their land is unsuitable for farming pigs or they cannot afford the infrastructure changes.

Pig numbers are estimated to be 254,600, down from 287,000 in 2014 and a 5 per cent drop on 2015 numbers, according to Statistics New Zealand. They would fall even further if crates were banned.

What would happen is a decline of New Zealand grown pork available in supermarkets. The products that make it to the shelf will be expensive and out of reach for most consumers. They have to be expensive to reflect the higher costs involved in growing these animals.

The floodgates would also open on cheap imported pork products to make up for the shortfall. They will come from countries that won't have the same welfare standards New Zealand pig farmers have to abide by and would undercut our farmers still able to provide products on shelves.

The footage is also a wake-up call for the dairy industry with calving well underway. If activists are watching pig farmers, you can be damn sure they are watching dairy farmers as well.

Most dairy farmers have stepped up and improved their calf welfare systems after the revelations of abuse a few years ago.

A Ministry for Primary Industries report released earlier this year showed that the calf mortality rate, between farm and processing, had halved from 0.25 per cent (one in every 400 calves) in 2015 to 0.12 per cent (one in every 800) last year.

New Zealand was also ranked first equal, out of 50 countries, for animal welfare regulations by the global charity World Animal Protection.

Despite these impressive statistics, there is still potential for a public relations disaster for the industry if abuse is caught on camera.

Calving is a tough, stressful time involving long hours in what has been a very wet winter and it is not over yet.

The solution is simple, don't give them anything to hang you with. Follow the rules and make sure any staff know the rules and make sure your farm has met the new industry standards around calf welfare. And keep posting images and videos on social media platforms of calves in pens.

These images go around the world and help counter the anti-farming propaganda put out by groups such as Safe and FarmWatch.