Milk Ejection in Cows Mechanically Stimulated During Late Lactation

Abstract

Twelve Holstein cows in late lactation were divided into 3 groups by previous milk production. The average time in lactation for all cows was 223 days. Cows were subjected to 4 treatments of teat stimulation: no stimulation, manual stimulation for 60 s, positive pressure pulsation (during first 60 s after teat cup application) and fast pulsation for the first 60 s after teat cup application. Each treatment lasted for 1 wk. On the last 3 days of each treatment, flow rate curves were recorded twice daily. Milk yield, milking time and milk flow dynamics were determined from these curves. Absolute peak and average milk flow rate exhibited by cows subjected to manual stimulation were only 3 and 10% higher than those of unstimulated cows. Manually stimulated cows required 30 s less machine-on time than unstimulated cows. This was less than sufficient to offset the 60 s stimulation routine. The total time required to stimulate and milk each cow, i.e., the procedure time, was longer for manually stimulated cows than for unstimulated cows but not different from that for stimulation by fast pulsation. Milk flow patterns for cows stimulated by positive pressure pulsation and for unstimulated cows were similar. Flow patterns for cows given manual stimulation, when corrected for procedure time, were similar to those of cows given fast pulsation stimulation. Milk, fat and protein yields were not different across treatments.