Level of Available Forage and Supplemental Protein and Energy for Cows Grazing Winter Range

A winter grazing trial at the SDSU Range and Livestock Research Station near Cottonwood was conducted to determine if the response to feeding a high starch supplement is dependent on the amount of protein fed and the amount of forage available. During December and January 126 Simmental-Angus crossbred cows grazing two pastures with differing amounts of available forage were fed four supplemental treatments that provided the following amounts of crude protein (Ib) and metabolizable energy (Mcal) per cow daily: 1) .72 and 3.92, 2) .72 and 10.64, 3) 1.44 and 7.78, and 4) 1.44 and 10.91. Cows grazing the high available forage pasture gained 41 Ib more than those grazing the low forage pasture. lncreasing the amount of supplemental protein from .72 to 1.44 1b per cow daily increased cow gains. lncreasing the amount of supplemental energy did not improve cow weight gains when the level of supplemental protein was .72 1b per cow daily. When the amount of protein was doubled, increasing the amount of supplemental energy increased gains by 21 Ib. There was a tendency for a greater response to the higher protein, higher energy supplement for cows grazing the pasture with less forage available.