Ben-Asher, A., Extension Service, Ministry of Agriculture, Tel Aviv 61-070, Israel
Ilan, D., Extension Service, Ministry of Agriculture, Tel Aviv 61-070, Israel
Levy, M., Extension Service, Ministry of Agriculture, Tel Aviv 61-070, Israel
Holzer, Z., Agricultural Research Organization, Nve-Ya'ar Experiment Station, PO Haifa 31-999, Israel

The effect of monensin supplementation on suckling male dairy calves was studied on a commercial farm. Twenty-eight calves were given monensin supplements from the age of 1 week and compared with a similar group not given monensin. During a 52-day suckling period, the supplemented calves gained 0·12 faster, with little difference in the conversion ratio of metabolizable energy into live weight. During the subsequent 42 days, there was no difference in daily gain, but the supplemented animals were 0·064 more efficient in the conversion of metabolizable energy into live weight. © 1982, British Society of Animal Science. All rights reserved.