Energy balance of individual cows can be estimated in real-time on farm using frequent liveweight measures even in the absence of body condition score

Existing methods for estimating individual dairy cow energy balance typically either need information on feed intake, that is, the traditional input–output method, or frequent measurements of BW and body condition score (BCS), that is, the body reserve changes method (EB_body). The EB_body method holds the advantage of not requiring measurements of feed intake, which are difficult to obtain in practice. The present study aimed first to investigate whether the EB_body method can be simplified by basing EB_body on BW measurements alone, that is, removing the need for BCS measurements, and second to adapt the EB_body method for real-time use, thus turning it into a true on-farm tool. Data came from 77 cows (primiparous or multiparous, Danish Holstein, Red or Jersey) that took part in an experiment subjecting them to a planned change in concentrate intake during milking. BW was measured automatically during each milking and real-time smoothed using asymmetric double-exponential weighting and corrected for the weight of milk produced, gutfill and the growing conceptus. BCS assessed visually with 2-week intervals was also smoothed. EB_body was calculated from BW changes only, and in conjunction with BCS changes. A comparison of the increase in empty body weight (EBW) estimated from EB_body with EBW measured over the first 240 days in milk (DIM) for the mature cows showed that EB_body was robust to changes in the BCS coefficients, allowing functions for standard body protein change relative to DIM to be developed for breeds and parities. These standard body protein change functions allow EB_body to be estimated from frequent BW measurements alone, that is, in the absence of BCS measurements. Differences in EB_body levels before and after changes in concentrate intake were calculated to test the real-time functionality of the EB_body method. Results showed that significant EB_body increases could be detected 10 days after a 0.2 kg/day increase in concentrate intake. In conclusion, a real-time method for deriving EB_body from frequent BW measures either alone or in conjunction with BCS measures has been developed. This extends the applicability of the EB_body method, because real-time measures can be used for decision support and early intervention.