Ruminant Nutrition News - 10/29/96
Using high NPN protein (Urea) based supplements on range cows may actually cause weight loss.
There are researchers in the northwest who have found the use of free choice presentation of liquid feed supplements to range cows can cause the decrease of weight gains or even weight loss. This is because cows on pastures supplying marginal or low energy have to use body energy to convert the free nitrogen to protein.
Liquid forms of supplementation are particularly troublesome in these cases. Variability of consumption and the use of high NPN sources of protein in liquid feeds are probably contributing factors.
These studies confirm a study I conducted on 47,000 cows in the Northwest during the winter of 1992. Those cows receiving their supplemental protein in 2/3 natural form and with energy supplied by high quality starches, fats and the inclusion of ionophores showed much less weight loss and calf mortality than the cows receiving either liquid supplements, molasses tubs, or mineral. The cows receiving no supplement at all had fewer calf mortality and calf scours than the cows receiving supplemental protein in the form of NPN at 78% of the protein source.
Below is the graph of that study.