Comparison of the effects of rectal examination on heart rate and eye temperature in cattle of different parity.

Heifers exhibit the greatest physiological stress during rectal examination, warranting improved habituation and handling protocols.

This prospective observational study investigated the physiological stress responses to rectal examination in 70 clinically healthy Holstein cows stratified by parity: heifers (n=15), first parity (n=15), second parity (n=15), and third or later parity (n=25). Stress was assessed via heart rate (HR) using auscultation and ocular surface temperatures (central cornea, medial canthus, lacrimal sac) via infrared thermography (IRT) across 12 time points spanning baseline, procedural stages, and 120-minute recovery. Heifers and first-parity cows required significantly longer examination durations compared to higher-parity animals (p<0.001), suggesting reduced compliance. Heifers demonstrated significantly elevated HR and ocular temperatures at the cornea and lacrimal sac during and following examination (p<0.01), indicating heightened sympathetic activation. Medial canthus temperatures showed minimal variation across groups. Linear mixed-effects models confirmed significant effects of both time and parity on physiological parameters. Notably, behavioral scores did not differ significantly between groups, underscoring the value of physiological over behavioral indicators for stress assessment. Key limitations include differential restraint and handling experience between heifers and multiparous cows, absence of cortisol measurements and HR variability indices, and lack of a restrained non-palpated control group, preventing full differentiation between restraint-induced and palpation-induced stress. The authors recommend improved habituation protocols and modified handling strategies for younger, lower-parity animals to optimize both animal welfare and procedural efficiency during routine reproductive examinations.

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