Evaluation of Magnetic Grain Feeder for Lactating Dairy Cows

A grain feeder activated by magnet to provide supplemental grain to high producing cows without physical separation of cows was tested with Holstein cows in early lactation. In trial 1 (30 wk), 20 cows were assigned alternately at calving to either a control group of 10 cows which received grain in the parlor at 1 kg per 3 kg milk or a magnet group of 10 cows which was offered 4.5 kg of grain in the parlor plus access to the magnetic feeder 1 h per cow per day until milk production dropped below 18 kg daily. Corn silage was fed free choice and hay fed at approximately 3.0 kg per head daily to both groups. Cows with magnets consumed more grain (9.1 kg from the feeder) and more total dry matter daily and produced 3.5 kg more milk per day with a lower fat test than control cows. When previous lactations were considered, milk yield was 1.5 kg greater by the magnet group. In trial 2 (25 wk), 20 Holstein cows were assigned randomly to a total mixed ration of corn silage and grain (60:40 ratio) plus 2.2 kg hay per cow or to a magnet group fed corn silage free choice, 2.2 kg hay per cow daily, and the entire grain ration from the magnet activated feeder. Cows with magnets consumed more grain and less total dry matter daily and produced a similar amount of milk with a lower fat test than control cows. Number of meals per cow daily was