(Reported to Senate from the Committee on Agriculture, Nutrition and Forestry with amendment, S. Rept. 96-400) Amends the Agricultural Act of 1949 to extend until September 30, 1981, the requirement that the price of milk be supported at not less than 80 percent of the parity price therefor. Extends until September 30, 1981, the requirement that the Secretary of Agriculture adjust the support price of milk at the beginning of each semiannual period after the beginning of the marketing year to reflect any substantial change in the parity index during such semiannual period.