Assessment of the mammary gland elasticity in dairy cows by using a single day once-daily milking
Résumé
In the current uncertain and fluctuating context, identifying adaptable cows is of key importance to secure dairy systems. Adaptable dairy cows could be defined by the elasticity of their mammary gland through its ability to both tolerate disruption and to return to its original state. However, little is known about how to identify those individuals. This study aimed to determine whether a single day ODM challenge could be used to quantify mammary gland elasticity and to explore individual responses profiles, factors of influence and repeatability of these responses. The trial used 292 Holstein-Friesian cows and consisted of 3 successive periods: 1 wk control of twice-daily milking (TDM), one day of ODM, followed by 2 wk of TDM. Cows were split into 10 groups over 5 milk years. The number of observations per cows varied from 1 to 9, with no more than 3 ODM challenges per lactation. Single day ODM generated an average loss of 6.3 kg/d (-21.3%) and an average recovery of 4.8 kg/d was observed when resuming twice-daily milking (TDM). Variability in responses was high among cows (CV=62% and 98% for milk losses and recovery). Clustering lead to the identification of 4 profiles of response, corresponding to different potentials of mammary elasticity. The 4 clusters obtained were well characterized by stage of lactation and potential milk yield level. Repeatability ranged between 33% for milk yield recovery (kg/d) and 57% for milk yield loss (%), suggesting a genetic determinism of the mammary elasticity to single ODM challenge.