deserve wider recognition

NUTRITION INTERVIEW

Sector has increased output while decreasing negative externalities for 30 years now. Time to tell this story. Sustainability gains in dairy nutrition deserve wider recognition

Nobody in the animal protein value chain can afford to ignore the growing consumer concern with sustainability. This point is inarguable.

However, it is also true that the consumer doesn’t actually know much about how animals are raised and fed.

In the case of US dairy nutrition, this has created a somewhat frustrating state of affairs. Years, or in some cases decades of meaningful and measurable progress on the sustainability of dairy feed has gone underappreciated by consumers and other stakeholders.

In a presentation to the Cornell Nutrition Conference last autumn, Professor Larry Chase of Cornell University’s Department of Animal Science attempted to rectify the situation and draw attention to the different metrics on which the sector has improved. As he went on to explain to Feedinfo in a recent interview, whether we’re talking about how much milk cows are producing per unit of feed, what is going into their feed, or what is coming out the other end as nitrogen or phosphorus emissions, the US dairy industry has improved remarkably upon the sustainability of its feeding practices, and continues to do so.

PRODUCTIVITY: DOING ASTONISHINGLY MORE WITH LESS

In some ways, it is almost understandable how the point about improved productivity has gone overlooked; it has been an exceptionally long-lived revolution. “If you look at the trend in the US, we’ve been going up 200 to 300 pounds of milk per cow per year for the last thirty years,” Professor Chase points out. In other words, this is not a recent change, but more like a background increase which has gone on for nearly a generation. “We’re on a continual path upward,” he notes. “Everybody wonders where the end is, but I don’t see a bend in the line yet.”

Still, it is impressive nonetheless. In his CNC presentation, Professor Chase quoted researchers including Capper and Cady (2019) showing that US Energy Corrected Milk (ECM) per cow increased by 22% in the decade from 2007 to 2017, meaning that with only a slight increase in the total number of dairy cows (up 2.1% over that same period), the herd was able produce 25% more milk. Each metric ton of milk, therefore, required less feed (17% less), less land (21% less), and less fresh water (30% less); meanwhile, emissions of nitrogen, phosphorus, and greenhouse gasses per unit of milk were down 17, 14, and 19% respectively.

“We’ve had continual improvement in understanding better the protein and the carbohydrates in rations, and the interactions. And then the amino acid balancing comes in also. Those are the three keys, in addition to forage quality… improvements in forage genetics and digestibility of the forages,” asserts Professor Chase.

NITROGEN AND PHOSPHORUS IMPROVEMENTS

It is also important to understand that the remarkable sustainability improvements seen in recent years are not just a function of improved productivity. In other words, it’s not all about making more milk. Professor Chase also highlights research carried out in dairy herds in New York (Higgs et. al. 2012, Van Amburgh et al., 2019) where dietary reformulations such as dietary crude protein reduction lowered daily manure nitrogen output (and also, happily, increased income over purchased feed costs).

Of course, studies showing that a more sustainable industry is possible are not, in themselves, proof of positive change; what truly matters is whether those changes are being incorporated on the ground. “I think if we look at the trend in the industry, the industry is feeding lower phosphorus, lower protein, then they did,” Professor Chase opines. “Obviously not all farms always buy into these things. But I’d say, when I look at rations on progressive farms, they’ve all made those types of shifts…[those farms] interested in incorporating new concepts, new technology, improving their livelihoods and profitability…”

The impact of these types of changes can be quantified with a concept known as whole farm mass nutrient balance (WFMB). Put simply, this is a measure of how much of a nutrient like nitrogen or phosphorus is being imported onto a farm, generally in the form of feed or fertiliser, versus how much is being exported, in the form of milk. According to a 2017 paper by Cela et al. quoted by Professor Chase, a study of 91 dairy herds in the Upper Susquehanna over the 9 years to 2013 found that WFMB for nitrogen decreased by 50% while that of phosphorus dropped 51%. “Decreases in feed nitrogen and phosphorus imports to the farm were a primary factor for the change in WFMB,” he asserts. In other words, these declines were not mainly from the increase in milk production, but were from more effectively and responsibly using inputs like feed to maximise the impact of the nitrogen and phosphorus it contains.

BYPRODUCTS AND HUMAN-INEDIBLE FEEDSTUFFS IN DAIRY RATIONS

Moreover, there is another misconception about the feeding of dairy cows that is harming the consumer perception of the industry: the idea that cows are consuming massive amounts of calories that could be feeding people instead.

However, this misses the very important point that cattle are able to digest fibres and extract nutrients from forages which are nutritionally useless for non-ruminant animals, including humans. There are a variety of ways that the exact impact of this can be calculated, but according to Professor Chase, the upshot is that between 75 to 85% (and sometimes more) of a dairy ration is

NUTRITION INTERVIEW

If you look at the trend in the US, we’ve been going up 200 to 300 pounds of milk per cow per year for the last thirty years.

inedible to humans. Meanwhile, each cow is turning that ration of mainly inedible fibre into hundreds of pounds of milk per day, milk which can feed humans. “I think it’s an important message to get out to people, that [for dairy cows] a lot of the feed they use is not human-edible. A lot of people don’t realise that.”

What’s more: when it comes to the use of coproducts in the feed, dairy cows are not only turning useless fibre into useful milk; they are helping to avoid the negative environmental impacts of disposing of those coproducts in another way. “Utilising co-product feeds in rations decreases the need to landfill or incinerate these feeds,” asserted Professor Chase’s CNC submission. “It was estimated that 137 million tons of co-products were available in an annual basis in the U.S. (Knapp, 2015). Less carbon dioxide was released if co-products were used in diets than if they were incinerated (Van Amburgh et al., 2019).” And again, this is not a niche practice with a limited impact; the use of coproducts from grain milling, ethanol production, beer brewing, or the rendering industry is quite well-established generally making up double-digitpercentages of the feed. Professor Chase’s own work in 2019 found coproducts made up 26% of total dietary dry matter in 46 high-producing dairy herds, while the Ven Amburgh et. al. 2019 study found they made up around 31%, with a range of between 9% and 57%.

NUANCE WANTED

Of course, it is difficult to generalise about sustainability. Every choice will depend on the circumstances, on the context; just as it can be environmentally problematic to swap out locally-raised veal for avocados shipped by air, so too can some of the sustainability strategies for dairy have unintended consequences.

Professor Chase, therefore, recommends that any sustainability action plan be based in a deep understanding not only of animal nutrition, but also of the land resources, crops, manure management, and economics. “The whole farm model gives us a chance to integrate the feed needs of the animal along with best [practices] taking advantage of the soil types and the cropping programs. Sometimes we might make a ration change — let’s say we want to feed more corn sileage — but if the land can’t produce more corn sileage, then it’s not a good match,” Professor Chase explains.

Or in other words, as he told the CNC, “Developing forage-based diets without considering the capability of the land resources and cropping system to supply the needed forage quantities and qualities is a problem.”

However, the real concern is not that the industry might begin to see these nutritional changes as silver bullets or one-size-fits-all solutions. Instead, Professor Chase is more concerned by the fact that the very significant progress on sustainability that the industry has achieved is going unnoticed by a society which claims to be concerned by these issues.

As he puts it: “We’ve made progress, but I think the average person doesn’t realise that.”

Works cited in this story available here. By Shannon Behary, senior editor