Small changes can pay big dividends in water use on dairy farms, both financially and in preserving water quality and supply. Determining where to make those changes often takes careful monitoring and investigation.
That was one of the messages delivered during the Southwestern Ontario Dairy Symposium earlier this year by Agriculture and Agri-Food Canada researcher Andrew VanderZaag.
Why it matters: Dairy leaders are pursuing a strategy of promoting the environmental sustainability of Canadian-produced dairy, and providing a good-news story about the sector’s water use is a crucial part of that strategy.
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VanderZaag has been studying water use on dairy farms in Ontario, B.C. and Quebec since 2016.
VanderZaag began his presentation by arguing that achieving water efficiency differs from pursuing a decreased carbon footprint, because the water supply is fundamentally local. Areas of the country more prone to drought don’t necessarily face water supply or quality challenges because of limited demand and a sparse population.
Here in southern Ontario, meanwhile, we may have the Great Lakes and the waterways feeding them in close vicinity, and we receive ample rainfall. However, given the vast population and the density of water users of all types, there’s still the potential for water demand to outstrip the supply.
Canada has lots of fresh water, he stressed. Nationally, we use about one per cent of the water recharge. But in southern Ontario, it’s much higher at more than 40 per cent — with thermal power generation by far the most significant contributor to this, but agriculture also plays a role.
VanderZaag’s research has mainly focused on “direct” water use by dairy farms, but he acknowledges a significant impact from “indirect” use.
For example, for farms in jurisdictions where thermal power generation is common, the total water balance tipped significantly if indirect water use is considered.
Purchased feed is another potentially significant contributor to indirect water use on dairy farms. If feed comes from farms using irrigation, dairy producers concerned about their operation’s water balance could consider looking for another supplier.
Regarding direct water use, VanderZaag has seen several good examples of minor changes to achieve significant decreases. One eastern Ontario farm was using approximately six litres of water per day for each litre of milk produced and had recently increased the milking herd to approximately 400. The farm hadn’t yet upgraded the holding tank receiving water for ultimate diversion to drinking purposes from the pre-bulk tank plate cooler. During the morning milking, the tank overflowed when the cows drank less, and water was lost to the liquid manure.
Increasing the capacity of the holding tank saved over 10,000 litres of water per day, and the farm’s estimated annual water use fell from 33 million to 29 million litres.
Overall in Ontario agriculture, irrigation — which has been making its way into Ontario’s dairy sector as producers strive to maximize crop yields — tops the list for direct water use at 53 per cent.
Water use attributed to greenhouse operations accounts for 13 per cent, leaving livestock farms with approximately 30 per cent of the province’s agriculture water use.
According to internationally recognized standards for measuring the water efficiency of food products, “using” water means either consuming it and taking it out of the watershed — including in the milk — or decreasing its quality within the watershed.
One unique key point of livestock water use is much of it is consumed compared to other agricultural operations.
An average of 67 per cent of water dairy cows use is for drinking; the rest is in the feed. One-quarter goes to the milk, but the majority goes into the manure — 44 per cent in the feces and 14 per cent in the urine. The rest consumed by the cows enters the atmosphere through respiration and transpiration.
The paradox faced in livestock, particularly dairy, is that heat and humidity adversely affect production, yet water consumption increases in those conditions. A farm striving to maximize its milk production per litre of water used can see a significant drop in that parameter if heat and humidity rise in the barn.
Managing the in-barn environment can play a considerable role, VanderZaag said, adding it pays to track temperature humidity index (THI) units in dairy housing and manage ventilation accordingly. His research shows mechanical systems generally perform better than natural systems for bringing cooler night air into the barn overnight.
Excess protein and salt in the ration can push up water consumption, so it’s important to ensure cattle get their optimum amounts.
Water use tends to be more significant in the summer, running at 23 per cent more on average than in winter for herds housed indoors year-long. It rises to 33 per cent more than winter for cattle housed outdoors during the pasturing season.
For water not consumed by the cows, almost all is utilized to clean the milking area and the milking system with minimal amounts for other general cleaning and, if present, misting mechanisms for cooling the cows.
VanderZaag says misters are a good idea, even if they use water, because their cooling effects decrease water consumption.
Untended leaks in the water system can be significant if they’re in an out-ofthe-way location or draining directly into the liquid manure infrastructure. “Have a procedure for checking on everything,” VanderZaag said.
It’s also common for different people cleaning the system to use different amounts of water. He advises determining the most water-efficient method and creating a “standard operating procedure” that all personnel should follow.
Even if environmental sustainability isn’t a top priority for a dairy farm, he suggested maximizing water use efficiency should be a priority. There are costs to using too much water, ranging from water system maintenance to water treatment products to liquid manure storage capacity issues and the machinery used to handle that manure.
