A comparison of the direct and residual response of dairy cows to once or twice-daily milking, in late lactation

Two experiments were undertaken to examine the direct and residual responses of late lactation (mean of 232 days calved) autumn calving dairy cows (Experiment 1), and late lactation (mean of 240 days calved) spring calving dairy cows (Experiment 2), to once-daily milking. Experiments 1 and 2 involved 50 and 44 Holstein–Friesian dairy cows respectively. In each of the two experiments, cows were milked either once daily (ODM) or twice daily (TDM), during the late lactation period (mean of 79 and 66 days in Experiments 1 and 2 respectively). Cows in Experiment 1 were managed within a grazing system, and were offered 3.0 kg of concentrate/day, while cows in Experiment 2 were housed, and offered grass silage supplemented with 6.0 kg concentrate/day. Forty-one cows from Experiment 1, and 32 cows from Experiment 2, completed the first eight weeks of the subsequent lactation on a twice-daily milking regime. Food intakes were not measured in Experiment 1, while treatment had no significant effect on dry matter intake in Experiment 2 (P > 0.05). In each of Experiments 1 and 2, total milk output was increased with twice-daily milking (P ≤ 0.05), while milk fat (P ≤ 0.01) and protein (P < 0.001) concentrations increased with once-daily milking. Somatic cell counts were higher with animals milked once daily in Experiment 1 (P < 0.001), while not being significantly affected by milking frequency in Experiment 2 (P > 0.05). Milking frequency had no significant effect on cow live weight or on cow condition score at the point of drying off in either Experiment (P > 0.05). Milking time per cow during morning milking was unaffected by treatment in either experiment, while total daily milking time per cow (morning and evening combined) was significantly longer with the TDM treatment (P < 0.001). In Experiment 1, milk flow rates during the morning milking were higher with animals on the ODM treatment, compared to those on TDM treatment (P < 0.001), while being unaffected by treatment in Experiment 2 (P > 0.05). Neither daily milk yield, milk fat content, milk protein content, or somatic cell count during the subsequent lactation, were affected by previous lactation milking frequency in either of Experiments 1 or 2 (P > 0.05).