All [animals] born from the first of Tishrei until the twenty-ninth of Elul combine [for maaser]. Five [that were born] before Rosh Hashanah and five [that were born] after Rosh Hashanah do not combine; five before the designated day and five after the designated day do combine. If so, with regard to what is it stated [that] there are three designated dates for the maaser of animals? That until the designated day arrives, one may sell or slaughter; [but] once the designated day arrives, he may no longer slaughter; however, if he did slaughter, he is exempt.