The researchers, from China and New Zealand, found that roughages used on dairy farms in Northern China consumed more water than that of the concentrates used.
The rigorous assessment of water footprint (WF) is a vital sustainability indicator in the agriculture and food sectors for governments, policy makers and water users, they said.
“The largest contributions to the WF of the collective feedlot systems in this study were from the water use for production of Chinese wildrye hay, alfalfa hay, maize grain and whole maize silage due to the greater water consumption and feeding quantity of those feeds. The average WF of roughages used was 1.43 times that of concentrates in this study.”
The results of the study, published in the Journal of Cleaner Production, show how changing feed components and origin can reduce water consumption in livestock sectors in China, argued the authors.
In recent years, to meet the increased demand of milk production in China (Huang et al., 2014), dairy farm systems have been changed from traditional systems to collective and intensive systems (Bai et al., 2013).
As a result of this development, the average cow numbers on a farm have increased from two or three to a few hundred or thousand, said the team.
“This makes it likely that [the] WF of milk would subsequently also have changed because of the difference in water consumption between the feeding systems and management practices.
“Feed cost is one of the major factors influencing feed selection, whereas consumptive water use for producing the feed is generally not taken into account. With the change in management practices, more feed is being brought in from other parts of China or imported from aboard. The owners of dairy farms now have the opportunity to choose between different feed products (Bai et al., 2013).
"With the increase in the degree of dairy farm industrialization over the years, the separation between livestock production and water consumption is increasingly evident (Thornton, 2010). In the context of water scarcity, reducing the amount of water consumption is important.”
The researchers argued that a rigorous assessment of the component of the WF of milk that is due to feed production might provide the data to develop strategies to decrease the use of high water-consumptive feed and increase low water consumptive feed use in Chinese dairy farming systems.
The team investigated and compared WF of milk production for 14 dairy farm systems, located in the Hebei province, where 13.2% of dairy cows in China are located (CRSY, 2015).
In this province, dairy cows are generally raised using collective feedlot systems.
Regarding the WF, the whole life cycle of raw milk production was taken into account from raw material of inputs to products leaving the farm-gate.
They said the cattle data in all dairy farms and the feed data related to milk production for each farm was collected from an on-farm survey in 2016 and also based on records kept by the farm managers.
Different feeding regimes were used for the different cattle groups. The average lactation period and dry period for cows were 290 days and 75 days per year, respectively, explained the researchers.
The feeds analyzed were purchased from different regions and brought into the farms. Maize grain and concentrates were mainly purchased from northeast China and local grain factories, respectively. Whole maize silage and yellow maize silage were either grown on-farm or purchased from local farmers who grew the crops. Soybean meal, beet pellet, Chinese wildrye hay, cotton-seed and alfalfa hay were purchased from local oil extraction companies located in Inner Mongolia, Northeast China, and Xinjiang or imported from the US, reported the authors.
They saw that the average WF for milk was 882 L kg−1 fat-and-protein-corrected milk (FPCM), ranging from 639 to 1307 L kg−1 FPCM, indicating a considerable difference in water consumption among the surveyed farms.
The collected data from the 14 farms showed that the roughages and concentrates accounted for 70.4 and 29.6% of total feed inputs, respectively, said the research team.
Whole maize silage, as the main roughage (representing average 53.1% DM intake), was the main feed for the feedlot dairy farm system in Hebei, followed by maize grain (average 19.1%), Chinese wildrye hay (average 10.0%), alfalfa hay (average 5.7%), cotton-seed (average 5.3%) and soybean meal (average 4.6%).
Oat hay, yellow maize silage and beet pellet were only used in a few farms.
The average WF of roughages (including whole maize silage, Chinese wildrye hay, alfalfa hay and oat hay) was 41.9% higher than the average WF of concentrates (including maize grain, soybean meal, cotton-seed and beet pellet). Large differences in WF among the feed crops existed, implying that consumptive water use for producing milk would be affected by different feed rations in a dairy farm system, found the researchers.
There are great potentials for individual farms to reduce the WF in milk production by optimizing the feed types and compositions, said the team. The variation in the feeds imported to the farm affected milk productivity and feed conversion efficiency, eventually influenced the WF of milk, added the researchers.
Using whole maize silage instead of Chinese wildrye hay could greatly reduce the total WF of milk production, they noted.
“The results from this study suggest that there are several ways to reduce the WF of milk production for the collective feedlot systems in China. Potential solutions include using high water use efficiency feeds and forages, importing more concentrates and roughages from low water scarcity regions and improving the FCE and productivity of cows with balanced feed ratios.
“If the water consumption for feed production is taken into account by farmers (such as via full costing for water use), they may choose feed with a lower water footprint to reduce consumptive water use for milk production.”
With the increase in water shortage problems in China, related policies, practices and management should encourage farmers to reduce the water use in the livestock sector, said the researchers.
Analysis shows that modern dairy systems have substantially reduced their environmental impacts due to reductions in resource use, waste output and greenhouse gas emissions (Capper et al., 2009). Improvement in management could further reduce the use of key resources such as water in dairy systems in China, said the team.
“However, it is also important that improved management practices should not cause other environmental trade-offs, e.g. importing more feeds from overseas may increase other environmental emissions including greenhouse gases (e.g. Wang et al., 2016).”
Source: Journal of Cleaner Production
Online ahead of print: https://doi.org/10.1016/j.jclepro.2018.02.165
Title: Components of feed affecting water footprint of feedlot dairy farm systems in Northern China
Authors: Y Lu, S Payen, S Ledgard, J Luo L Ma, X Zhang