An international team based in New Zealand and the US examined the milk generated by grass-fed cattle raised in conventional and organic dairy production systems.
The team examined the chemical composition of the products produced in the two systems.
They wanted to see whether there would be any difference in the components of the milk, explained Don Otter, coordinator in the dairy processing program at the Center for Dairy Research at the University of Wisconsin-Madison.
For cows raised in a conventional system using pasture it was anticipated they would produce milk with similar components to that from cows in an organic system. And the team found that milk generated by the different systems was comparable in nature.
- CLA and VA are increased in conventional milk from cows fed pasture.
- Oligosaccharide composition is variable between organic and conventionally produced milk.
- Protein and milk volatile composition are independent from farming system.
Consumers have demonstrated the willingness to pay premium prices for dairy products generated in those feeding and production systems.
“The organics still claim a premium, but whether they should is a good question to ask,” said Otter. “Some consumers clutch on to the idea there might be something inherently different with the [organic] milk, but in this instance, that’s not right.”
“There are a fraction of people who say the [organic produced] milk has to be better for you, but I don’t think that can be born out,” he said. “But I think a lot of people go into the organics for other reasons like sustainability.”
In past studies in the US, researchers found more conjugated linoleic acid (CLA) fatty acids in milk generated through an organic feeding system, he said. However, that difference comes from the additional pasture feeding that cows in an organic system have.
There are some different methods involved in conventional dairy production and organic management, even when cattle in both systems are fed on pasture, said Otter.
“There are different techniques that organic farmers use, like only putting cows in a pasture for a short period of time so they only eat the top bit – and the conventional [system] lets them really clean the pasture out, [so] maybe under that conventional method you are getting different aspect of the grass or different microbes from the soil,” he said. “But every farm is different.”
In the study, 403 cows on either conventional or organic diets were tracked for a milking season, the researchers said. Both sets of paired farms used in the study included one organic farm and one conventional farm located in close physical proximity.
Milk samples were taken twice weekly during the period for one set of farms, both organic and conventional. Samples were collected weekly on the second set of organic and conventional farms.
Milk was analyzed for difference in free oligosaccharides, fatty acids, major casein and whey proteins and milk fat volatile compounds.
“We looked at the fatty acids and we saw some minor changes, but statistically it was not that significant,” said Otter. “If we had a 10-year study you’d see the ups and downs.”
The fatty acid fluctuations were altered by breed and fertilizer use, said the researchers in the paper. Some oligosaccharides also differed between farming systems, but not all were influenced by production type.
“We looked at the individual proteins,” he said. “We didn’t expect to see major changes in the proteins and that was born out.”
Additionally, many of the variables between the cows on organic feed and conventional pasture were accounted for in the study, he said. “The cows came from the same breeding stock, the farms were next to each other so the soils were the same, the weather was the same [and] the management was the same,” he added.
“What you find with milk is you don’t need a big changes in the diet to change small components in the milk as well,” he said. “But if that effects the overall quality, I don’t think so.”
Currently the team is examining the data generated from metabolic profiling found in the two different feeding systems, said Otter. “The metabolite profiling will probably find small differences – don’t think we’ll see major differences,” he added.
There also has been some consideration given to attempting to replicate the study in another country, he said. However, it would be a challenge to account for variables in areas where production styles are very different.
However, it also would be of interest to complete a meta-analysis on milk generated from multiple different feed types, said Otter. “Depending on what you feed the cow you get different fatty acids, as to what is the best or optimal feed who knows?” he added.
Source: Food Chemistry
Title: Pasture feeding conventional cows removes differences between organic and conventionally produced milk
Authors: B Schwendel, T Wester, P Morel, B Fong, M Tavendale, C Deadman, N Shadbolt, D Otter