Biological position of viruses: Viruses lack a cytoplasmic membrane and they do not have the basic component of a cell. They can only replicate inside the host cell. Outside the host cell, they are non-living.
The yearling program was, however, more variable with a maximum profit of $356 per head compared with $206 for calf fed, and a maximum loss of $171 per head compared with $152 for the calf fed program.
The discounted present value of the. $403 total is $351, which is the opportu-. nity cost of an open heifer. That value il-. lustrates the importance of getting first-. calf heifers rebred, Hughes says. When a heifer doesnât rebreed, the. cost of keeping her for a year must be ab-. sorbed by the females that do raise a calf,