Feeding behavior changes of cattle during introduction of monensin with roughage or concentrate diets.

To assess the nature of the aversion frequently shown by cattle for feed containing Rumensin, cattle were prepared with rumen cannulas and adapted to either a 93% ground alfalfa hay diet (n=12) or an 85% concentrate diet (n=12) They were assigned to one of three treatments for 6 hr/day for 7 days: 1) Basal feed and continuous intraruminal injection of a total of 50 ml alcohol (Control); 2) 250 mg monensin sodium as Rumensin/4 kg feed and continuous intraruminal injection of a total of 50 ml alcohol (Rumensin); or, 3) Basal feed and continuous intraruminal injection of a total of 250 mg monensin sodium in 50 ml alcohol (Monensin). All groups were offered basal feed the following 18 hours. Cattle fed Rumensin in the concentrate diet showed reduced intake within the first .5 hr of the first day (1.36 vs .13 kg, P<.05), while cattle fed Rumensin in the alfalfa diet ate as much feed as controls the first day but decreased intake the second to seventh days. On the first of five recovery days, cattle previously fed Rumensin ate the same amount as control cattle with both alfalfa and concentrate diets. Cattle fed Rumensin in both diets for 7 days, even after a 5-day recovery period, showed an immediate and marked aversion when offered feed containing Rumensin. Cattle injected with monensin ate less concentrate but not roughage diet during the 6-hr t reatment period. Cattle continuously injected with monensin sodium showed an