Some Sources of Error in Weighing Steers Off Grass

Abstract

One hundred and eighty head of yearling and two-year-old steers were used over a period of 15 months to study the variations that occur in the amount of fill contained by steers running on pasture. The weight changes between a base weight taken under uniform conditions and subsequent weights taken under controlled conditions constituted the items of study. Under the conditions of the experiment it was found that the availability of water was a more important source of fill variation than the availability of pasture grass. There was an indication that under some conditions the differences in amount of fill among the animals tend to be lessened by shrinking. Animals in different pastures exhibited different amounts of fill when gathered during the afternoon. Using full weights under such conditions would tend to reduce the repeatability of experiments. Steers weighing from eight hundred to a thousand lb. lost about one lb. every ten minutes during the first three to four hours of shrinking whether they were held in a dry lot or were being quietly driven. Animals on pasture early in the morning appeared to lose fill faster than it was replaced. These findings emphasize the necessity for using standardized procedures in weighing cattle. It is suggested that all lots of cattle should have water equally available at all times. Shrinking cattle for a period of 10 to 15 hours before taking the weights that are to be used in the final evaluation of treatments effects may increase experimental efficiency. If several lots are involved, they should be weighed as rapidly as possible to prevent excessive loss of fill by those being weighed last.