Relationship between body condition score and ultrasound measurement of backfat thickness in multiparous Holstein dairy cows at different production phases.

Background: The validity of the body condition score (BCS) for evaluating subcutaneous fat has been questioned because of its subjectivity. With the advent of ultrasonography, backfat thickness (BFT) can be objectively measured and used to assess the energy status of dairy cows in conjunction with BCS.
Objective: Determine the relationship between BCS and ultrasound measurements of BFT throughout the lactation cycle.
Methods: Cows (n = 1123) were selected randomly and classified according to their lactation stage into four different groups. BCS was determined using a 5-point scale and BFT measurements were obtained using a 5-MHz linear transducer.
Results: The correlation coefficient (r) for the relationship between BCS and BFT varied according to the stage of lactation. There was a high correlation (r = 0.96-0.98) and relationship (r(2) = 0.92-0.96) between BCS and BFT. The highest correlation was found at BFT values of 10-35 mm and BCS of 2-4.5 units.
Conclusion: BCS is a practical tool for evaluating body condition; furthermore, it may be as valid as BFT for the estimation of subcutaneous fat in Holstein dairy cows over time.
(© 2013 The Authors. Australian Veterinary Journal © 2013 Australian Veterinary Association.)