Evaluating the impact of milk sample-based pregnancy test procedures on milk production and daily time budgets of dairy cows

Prolonged restraint of dairy cows during pregnancy diagnosis in headlocks can elicit stress responses, potentially compromising animal welfare and productivity. Sample-based pregnancy testing (SBPT) utilizing milk samples obtained at the milking parlor eliminates the necessity for prolonged headlock restraint. The objective of this study was to evaluate the effects of implementing SBPT procedures in commercial dairy farms by assessing milk production and daily time budgets of cows compared with traditional pregnancy testing methods. An experiment was conducted at a USDA-certified organic dairy farm using a repeated crossover design with treatment (TRT: SBPT) and control (CON: transrectal ultrasound) groups in 3 pens over 6 periods. Cows in the TRT group were subjected to IDEXX milk SBPT in the milking parlor, whereas those in the CON group underwent transrectal ultrasound in headlocks for pregnancy diagnosis by a trained veterinarian. Daily milk yield from individual cows was recorded by inline milk meters, and lying behaviors and step counts were recorded using leg-based accelerometers. On the day of the pregnancy test, TRT cows exhibited a 0.45 kg higher milk yield compared with CON cows. Milk yield increased by 1.13 kg on the day after testing and by 0.53 kg per day weekly average in TRT cows. The TRT cows displayed higher daily step counts and lying bout frequencies, but shorter lying bout durations on testing days, although total lying time did not differ significantly between groups. These results suggest that SBPT procedures may facilitate reduced restraint time, leading to improved milk production and altered daily time budgets, thereby potentially reducing prolonged headlock-induced stress for a short term.