Score using indicators of reticulo-rumen pH kinetics to characterize subacute ruminal acidosis
Abstract
The development of novel farm management technologies are promising strategies to improve welfare, efficiency, and productivity toward sustainable agriculture. The non-invasive and continuous recording of physiological parameters thanks to the use of biosensors, coupled to the development of dedicated data processing, make possible to precisely monitor the kinetics of specific parameters to assess rumen environment and other physiological traits. The objective of this study was to validate a set of novel indicators of reticulo-rumen (RR) pH kinetic that can better define the pattern of RR pH during a SARA challenge. Two different experimental SARA challenge studies (3-period switchover design including a high starch diet: HSD>30% starch and <30% NDF) were conducted with 10 animals equipped individually with a RR sensor allowing a pH measurement every 10 min. Commonly used pH indicators of SARA (daily average, time spent under RR pH<6.0, area under the curve and daily amplitude) were calculated as well as descriptors modelling the pH curve. Unexpectedly, daily pH mean was not able to predict accurately the change of diet when cows were fed a HSD whereas performance and health indicators were altered confirming the susceptibility of the animals to the SARA challenge. However, indicators derived from pH kinetic significantly responded to when cows were fed a HSD compared to a low starch diet. For instance, the number of pH drops was significantly lower during the SARA challenge compared to a low starch diet (3.05 vs 4.71 drops/day, respectively for study 1 and 2.84 vs 3.27 drops/day respectively for study 2, P<0.01). Finally, a significant higher SARA score combining multiple daily pH indicators was able to identify when the animals were fed a HSD (3.8 vs 0.24 for study 1 and 12 vs 5.7 for study 2). Pre and post SARA challenge periods were comparable for these parameters, suggesting a good correlation with animal biology. These new indicators derived from RR pH kinetic carry additional information on pH variation; this makes them good candidates as descriptors of ruminal status.