Production responses in early lactation to additions of soybean meal to diets containing predominantly corn silage

Responses in yield of milk and intake of dry matter to increased concentrations of dietary crude protein by cows in early lactation were modeled from published data. The data base was 625 Holstein cows in second or later lactation fed diets primarily composed of corn grain and a combination of corn silage and alfalfa. Dietary crude protein as a percent of dry matter ranged from 9.5 to 20.2% and was varied with soybean meal. Exponential models were developed to predict changes in milk yield and dry matter intake per unit change in dietary crude protein. The consequence of changes in concentration of dietary crude protein on performance can be predicted with the models. The dose-response relationships can be used with relevant price information to estimate the concentration of crude protein that maximizes returns over feed costs. Profitability is improved by adjusting concentration of dietary crude protein for changes in the price of soybean meal. Present feeding standards could be enhanced by incorporation of information on dose-response and economics.