Some have the custom not to eat meat… during the week [of 9 Av, until after 9 Av]; some add from rosh chodesh until the fast; some add from 17 Tamuz.
Rama holds of the middle view. He adds:
We hide the slaughtering knife from rosh chodesh, since we don't slaughter (except for a mitzva, as for a sick person, the sabbath, a mila, or the like).
Nowadays, obviously, we don't need to slaughter animals right before eating them. Moreover, many non-Jews buy kosher meat. The above-implied reason for not slaughtering during the nine days is pretty much gone.
- What is the current common practice? Are kosher slaughterhouses open during the nine days? during the week of 9 Av?
- Are there any pos'kim that explicitly permit or ban slaughtering at this time of year in light of modern technology, infrastructure, and/or demand?