Research Progress Report 416
June, 1973

Substitution of Forage Protein for Oilmeal Protein
in Rations for Lactating Dairy Cattle

C. H. Noller, D. L. Hill, H. M. Saturnino, B. W. Crowl and C. L. Rhykerd
Departments of Animal Sciences and Agronomy

SUMMARY
Two experiments with lactating dairy cows compared forage protein to oilmeal protein for milk production. In Experiment I, a corn-soybean silage with 38% soybean forage reduced the protein need in the grain mixture from 22.0 to 17. 5% with no effect on milk production.
In Experiment II, protein in alfalfa silage replaced all of the oilmeal protein with no effect on milk production. Protein in the grain mixture was reduced from 21.2% with corn silage as the sole forage to 8.9% with alfalfa (22.9% crude protein) as the sole forage. Alfalfa, as the sole forage, supplied 72% of the ration protein. With corn silage as the sole forage, 54% of the ration protein was supplied by soybean meal. In both experiments, the protein in forage replaced protein in soybean meal with little or no effect on milk production.

INTRODUCTION
Within certain limits, the needs and physiological requirements of animals are not expressed in terms of pounds of feed; rather feeds should be considered on the basis of their nutrient content. Protein is
one of the more expensive nutrients in a dairy ration. Consequently, effective use should be made of existing protein sources and searches made for more economical sources.
For years it has been recognized that dairy cattle can utilize forages readily, and that legume forages and immature grasses or grasses fertilized with nitrogen are relatively high in protein. When oilmeals and other sources of protein normally used in dairy rations become expensive, consideration should be given to partially or complete-ly replacing protein in sources such as soybean meal with forage protein.
The purpose of this report is to present information comparing the ability of forage protein to substitute for protein from oil-meals in rations for lactating dairy cows.

PROCEDURES
Experiment I compared corn-soybean silage protein as a substitute for soybean meal protein in rations for lactating dairy cows. Corn-soybean silage was harvested from a field in which corn and soybeans had been planted in alternate rows. The mixture contained approximately 38% soybean forage with a protein content of 10. 6% on a dry basis.

Agricultural Experiment Station, PURDUE UNIVERSITY, West Lafayette, Indiana