This has not been a problem because grain in the corn silage is hard and considerable corn is excreted in feces. Both rations are within the guidelines for ration fat and for rumen nitrogen balance. Amino acid balance and expected milk are in Table 6 . Overall, amino acid supplies are within the guidelines. Meeting target milk will require mobilization of body energy.
Rations provide metabolizable methionine and lysine for milk above target levels.
Isoleucine would limit target milk but we have not been able to conclusively demonstrate that this occurs. References Ferguson, J.D. 1996. Penn Annual Veterinary Conf. Univ. of Pennsylvania, Kennett Square. Fox, D.G., C.J. Sniffen, J.D. O'Connor, J.B. Russell and P.J. Van Soest.