Impact of using an electrified crowding gate on milk yield and milk flow

Abstract Text: Many dairy enterprises use automatic crowding gates in the waiting area of the milking parlor to assist and expedite the entrance of cows into the parlor. Some of theses systems include electrified gates. We hypothesized that the use of an electrified crowding gate may impose an alert response in the cows, which in turn may negatively affect milk let down and production. One hundred and fifty dairy cows (71 primiparous; 79 multiparous, DIM = 225±109 d) were split in two groups and milked in a 32-stall rotary parlor using a crowding gate that was either unelectrified (NEG) or electrified (EG). The experiment followed a 2x2 Latin square design with two periods of 9 d each. The waiting area was 200 m²and equipped with rubber flooring. The crowding gate was 13-m long. Cows were milked at 0600 and 1800 h. At each milking, milk production, milk fat content, milk protein content, average milk flow, maximum milk flow, and time to peak milk flow were recorded on an individual basis. The first 4 d of each period were discarded, and data from the last 5 d were averaged by cow and analyzed using a 2-level mixed-effects model that accounted for the random effect of cow and period, and the fixed effects of type of crowding gate, parity, their 2-way interaction and days in milk as a covariate. Time elapsed between the initiation of milking and peak milk flow (1.61±0.05 min) did not differ (P = 0.67) between treatments. However, peak milk flow tended to be greater (P = 0.10) in NEG (5.8±0.16 kg/min) than in EG (5.6±0.16 kg/min) cows. Similarly, average milk flow tended to be greater (P = 0.06) in NEG (3.00±0.07 kg/min) than in EG (2.96±0.07 kg/min) cows. Milk yield was greater (P < 0.01) when cows were milked with NEG (14.0±0.25 kg/milking) than when milked with EG (13.6±0.25 kg/milking). Treatment had no effect on milk protein (P = 0.33) or fat (P = 0.77) contents. It is concluded that using an electrified crowding gate may compromise milk flow and results in decreases in milk yield. 

Keywords:  let down, stress, parlor