Effect of automatic milking systems on milk yield in a hot environment.

A comparative study was performed to evaluate differences in milk yield between an automatic milking system (AMS) and a conventional herringbone milking parlor system. Two herds of Italian-Friesian cows were reared in the same barn, located in the Po Valley in northern Italy. Twenty-five primiparous cows and 10 multiparous cows were milked with an AMS, while at the same time 29 primiparous and 9 multiparous were milked twice daily in a milking parlor on the other side of the barn. A selection gate allowed cows to access the AMS only if the interval from last milking was >5 h. Multiparous cows in the AMS yielded more milk than multiparous cows in the milking parlor (34.2 +/- 0.7 vs. 29.4 +/- 0.6 kg/d). There was no difference in milk yield between primiparous cows in the AMS and in the milking parlor (28.9 +/- 0.4 vs. 28.8 +/- 0.3 kg/d). Milking frequency in the AMS was significantly higher in primiparous (2.8 +/- 0.03) than in multiparous cows (2.5 +/- 0.04). The hot season negatively affected milk yield; the milk yield reduction was higher for cows milked with the AMS (-4.5 +/- 0.6 kg/d) than in the milking parlor (-3.0 +/- 0.8 kg/d). In the AMS, milking frequency decreased during the hot season in primiparous cows (-0.3 +/- 0.1). We concluded that a positive AMS effect on milk yield is possible, but that steps must be taken to alleviate the discomfort involved with attracting cows to the AMS.