Effect of lasalocid on fall-calving beef cows

Forty-two fall-calving crossbred cows were equally allotted to six pens of seven cow-calf pairs each. Two treatments (0 and 200 mg lasalocid/head/day) with three replications were used to determine the effects of lasalocid on fall-calving beef cows. The cows were fed grass hay, haylage and pasture ad libitum. The cow-calf pairs were weighed every 28 days during the 196-day trial. Milk yield was determined three times using the weigh-suckle-weigh technique and the milk was analyzed for fat and protein. Average days open from parturition to conception was also determined for the cows. There was no difference between treatment for cow weight and body condition (scale 0-9) change. The cows lost an average of 9.5 kg throughout the trial. A slight tendency towards increased milk production was observed in the lasalocid-treated cows, but this was not significant. There were no significant differences between treatments or time for percent milk fat and protein. Calf gain was not affected by treatment with average daily gain being 0.77 kg per day for both lasalocid and control calves. Average days open was also not affected by the use of lasalocid. However, there was a numerical advantage of five days in favor of the lasalocid-fed cows. It is possible that the lasalocid cows may have eaten less, thus making them more efficient; but this was not measured. No detrimental effects were observed on lactation, weight change or reproductive performance with the use of lasalocid