Evaluation of Protein Utilization in Low and High Protein Forage Sources and the Economic Value of Supplementing Field Peas (pisum sativum) to Growing Cattle Grazing Crested Wheatgrass Pastures

Field peas are widely grown in the panhandle of Nebraska; however, markets quickly become saturated. A two year experiment was conducted comparing field peas to dry distillers grains with solubles (DDGS) as a protein supplement. The objective was to establish a price producers could pay for field peas relative to DDGS. There was a significant difference in ADG due to type of supplement (P = 0.02). Field pea supplemented heifers had 10% lower ADG compared to DDGS supplemented heifers. Economically, this means if DDGS is priced at or $124.58/ 909 kg DM a producer could pay $2.89/ 27 kg, for field peas. Variable sources of grazed forages are used in cattle backgrounding systems, but in most systems metabolizable protein (MP) is limiting and rumen undegradable protein (RUP) supplement can meet this deficiency. The first objective was to determine if RUP is limiting and the second objective was to determine if highly digestible forages with rapid passage rate allow some rumen degradable protein (RDP) to bypass the rumen. A pooled analysis of growing cattle grazing forages demonstrated that average daily gain (ADG) increased with increased RUP supplement received, with the exception of animals grazing forages that were 17% crude protein (CP) or greater. A metabolism study evaluating high and low quality forages showed lower intakes and digestibility values for the lower quality forages. Rapid liquid passage rates suggest some degradable protein could be leaving the rumen before degradation. Numerous digestibility markers were used to evaluate markers in forage based diets. Advisor: Andrea K. Watso