Measuring individual carbon dioxide production can be a promising tool in distinguishing feed efficiency of dairy cows
This is the main conclusion of a study carried out by researchers of Wageningen University & Research, Animal Breeding and Genomics (WUR-ABG). The study was presented by István Fodor at the 45th ICAR Annual Conference held in Montréal, Quebec, Canada, between May 30th and June 3rd 2022.
In order to confirm the the utility of residual carbon dioxide (RCO₂) as
a proxy for feed efficiency, researchers assessed the relationship between RCO₂
and Residual Feed Intake (RFI) in mid-lactation on a dairy farm. The concept of
RCO₂ is similar to the index of RFI, and used as a proxy (either alone or in
combination with other easily available parameters), it could potentially
enable ranking cows based on feed efficiency. Although the concept of RCO₂ was
originally developed using data from respiration chambers, the approach could
be used on farms as well by using sensors with highly repeatable carbon dioxide
measurements (e.g. GreenFeed).
Benefits of large-scale feed efficiency
Global demand for milk and dairy products is expected to increase over the coming decade. Improved feed efficiency of dairy cows has large potential to reduce the environmental impact of this growth in several ways. Not only can the land requirements of feed production be decreased, but selection for improved feed efficiency can significantly decrease methane emissions of dairy cattle. In addition, feed efficient cows produce less manure, which means that the amount of methane and nitrous oxide released into the atmosphere is reduced. Farmers also benefit from improved feed efficiency through reduced feed costs, which represent more than fifty percent of the total costs of milk production.
Residual carbon dioxide: a promising proxy
By analyzing the data collected during a series of experiments carried out at the Dairy Campus of Wageningen University & Research (WUR), the researchers were able to distinguish between feed efficient and inefficient cows, which confirms the utility of residual carbon dioxide as a proxy for feed efficiency on dairy farms. For future use in practice, however, care should be taken when evaluating RCO₂, given that the cows’ energy balance influences RCO₂. For example, cows in negative energy balance use body fat reserves to synthesize milk fat, which process does not generate carbon dioxide. Consequently, these cows can be erroneously considered efficient. A possible solution might be to perform carbon dioxide measurements in mid-lactation, when the probability of such misclassification is low, or to keep track of the energy balance of the animals, for example by routinely recording changes in their body condition or milk composition.
This study was supported by the TKA Agri and Food project LWV19143 and the partners Melkveefonds and Connecterra.