A study conducted at Cornell by the D.E. Bauman research group revealed that dairy cows that receive Recombinant Bovine Somatotropin (rbST) have a higher milk efficiency, which in turn lowers their carbon footprints. RbST is an FDA approved artificial growth hormone that allows cows to more efficiently use nutrients so that fewer cows are required to produce the same amount of milk.
“On an individual cow basis we get eight percent less manure, less feed, less land, less water [when supplemented with rbST]. We get less methane, nitrogen and phosphorus coming out of the cow,” said Judith Capper, animal science, the lead author of the study. “The cows give an extra 10 ounces of milk.”
According to Capper, the study found that if rbST was used on a population of 1 million cows, the carbon footprint would be equivalent to taking 400,000 cars off the road or planting 300 million trees.
The study was divided into three parts, the first two of which examined the effect of rbST on an individual cow and on a population of one million cows. The last part of the study modeled the environmental impact of conventional dairy systems, conventional dairy systems with rbST, and organic dairy systems in relation to population growth by the year 2040.
“If you use rbST, we needed about eight percent less land, feed, and we had a carbon footprint come down by seven percent,” said Capper. “To produce the same amount of milk from organic farming we needed more land and more cows, and therefore we have a higher environmental impact both in terms of the carbon footprint but also acidification and eutrophication which are about water quality.”
According to Capper, one in three cows is within a conventional herd in which the farmer buys rbST. However, this does not necessarily mean that all of the cows in the herd are receiving the hormone. Also, rbST use is not permitted in organic dairy farming.
“RbST has been approved now for 15 years so the time was right now to get a good look at it from an environmental standpoint,” said Prof. Dale Bauman, animal science, corresponding author of the study.
Bauman explained the rationale for the study being threefold. First of all, previous studies had only considered one or two variables such as only the effect on methane and nitrogen production, so this study would consider all of the variables more extensively. Also, the authors wanted the study to have a stronger scientific base. As a result, they used the National Research Council National Academy of Science report on the nutritional requirements of dairy cattle to base all their calculations off of.
Lastly, Bauman said that the group made sure everything they did was referenced in scientific literature and there were no assumptions, so all of the calculations could be reproduced and there was a firm base in science.
To assuage the fears of people who hear the word “hormone” and are afraid of the effects of rbST, Prof. David Barbano, food science, said, “This is not a steroid hormone. It’s a protein. Insulin is a protein. Growth hormone is the same way. It has no oral activity. It’s not transferred to the milk anyway, but even if you ate the rbST you’d digest it just like you’d do any other protein.”
According to Bauman, there is in fact no difference between milk produced by cows treated with rbST and not treated with rbST. There is no test that can be done on milk to tell which production system was used to produce the milk.
The study, entitled “The Environmental Impact of Recombinant Bovine Somatotropin (rbST) use in Dairy Production,” was published in the Proceedings of the National Academy of Science in July.