Short communication: Assessment of disbudding pain in dairy calves using nonlinear measures of heart rate variability

Abstract

The purpose of this study was to evaluate whether pain-related stress caused by disbudding could be detected using nonlinear measures of heart rate variability (HRV). Twenty-five female Holstein calves (4-7 wk of age) were randomly assigned to 1 of 3 treatments:(1) sham disbud (SHAM; n = 9), (2) disbud with lidocaine-meloxicam pain mitigation (MED; n = 8), or (3) disbud without pain mitigation (NoMED; n = 8). Heart rate variability (sample entropy, percentage determinism, percentage recurrence, or mean length of diagonal lines in a recurrence plot) was recorded on d −1, 0, 1, 3, and 5 relative to the experimental procedure, with disbudding taking place on d 0. The short-term detrended fluctuation analysis scaling exponent was greater in MED calves than in SHAM calves, indicating a greater stress response to the disbudding procedure regardless of pain mitigation. These results indicate that calves in the MED group may have experienced pain-related stress as a result of the disbudding procedure. The remaining nonlinear HRV measures did not differ by treatment. Future research on this topic should address additional potential confounding factors, such as the effect of pain-mitigating drugs on autonomic function or the influence of the autonomic nervous system on wound healing, that may prohibit HRV measurement as an indicator of disbudding pain severity.

Methods for Pain Assessment in Calves and Their Use for the Evaluation of Pain during Different Procedures—A Review

“…In calves, measurement of heart rate (HR) is done by auscultation in restrained animals [ 28 ], or by use of a girth heart rate recorder and data loggers [ 35 ]. Heart rate variability (HRV), or changes of the time interval between heartbeats, can be used to evaluate the activity of the sympathetic nervous system as part of the autonomic nervous system [ 111 , 116 ], and the autonomic nervous signs associated with stress in cattle [ 117 ], representing changes in the balance between sympathetic and parasympathetic branches of the autonomic nervous system [ 118 ]. Changes in the sympathetic and vagal balance occur due to psychological and environmental stressors, but also related to diseases [ 116 ].…”

“…HRV is assessed by use of a fitting heart rate monitor fixated with a belt to the clipped skin behind the left foreleg of the animal, which records nonlinear measures [ 111 , 117 , 119 ]. The simplest way to measure HRV is by time domain measures.…”

“…Sequences of IBIs are converted into geometrical forms; afterwards, assessment of HRV can be extracted from these forms [ 116 ]. These measures can be quantified using available software [ 117 ].…”

“…Research showed that HR is significantly increased in animals experiencing pain, such as castration [ 35 , 111 ] or disbudding [ 117 ]; HRV changes following a painful event [ 111 ]. According to these studies, the measurement of heart rate can be used to assess if calves are in a painful state, especially an acute one [ 111 ].…”

“…Bearing in mind that not only pain but also stress and other factors result in changes of HRV [ 111 , 116 , 117 ], it is advisable to evaluate HR and HRV in combination with other methods for pain assessment, such as cortisol, SP, IRT, or behavior [ 35 , 65 , 111 , 115 ].…”