If first-test day is after day 75, the record is made unofficial since accurate estimates of early lactation production are impossible from a single day's yield so late in lactation. If the previous sample day was prior to 40 days in milk, test-interval yield needs to be adjusted for changes in daily production that occur around peak lactation. Recall that she was a first-lactation cow originally tested at 20 days after calving with 45 pounds of milk. The correct factor for milk from table 2 is 1.02. The factors in table 2 are always 1.00 or greater, meaning average daily yield for test intervals initiated prior to 40 days in milk is expected to be larger than the average of the two test days involved.
More adjustment is made when the previous sample day is early in lactation.
The factors also increase as days in the interval increase, especially if the interval begins early in lactation. Two different situations exist for the last test-interval. In the first situation, the cow milks beyond 305 days with a test after the 305th day of lactation. In the second situation, the last test-day weight available on a cow occurs before day 305 of lactation. This equation uses the last two available tests to determine the decline in yield each day.