The kill is the trade's word for the slaughter count, and it is the supply side of every beef price you see. Production is the kill times the carcass weight, so when the kill runs light against last year there is simply less beef to sell, whatever demand is doing. The number gets quoted constantly, which makes it worth knowing where it comes from.
Counted at the plant
Every federally inspected packing plant operates with Food Safety and Inspection Service personnel present, and their reports are the raw material of the count. USDA publishes same-day estimates of daily livestock slaughter built on that inspection data, with running comparisons to the prior week and to the year ago pace, plus estimated weekly totals alongside them.
Estimated first, actual later
The same-day figures are estimates and they get trued up. The actual federally inspected slaughter for a week publishes once complete counts are in, and USDA's National Agricultural Statistics Service rolls federally inspected data into its monthly Livestock Slaughter releases. Practically, the freshest kill numbers are provisional and the settled ones arrive on a lag: the weekly actual series Meat Read tracks publishes roughly two weeks behind the week it covers.
Reading it like a buyer
Two habits keep the number honest. Compare year over year rather than week over week, because the kill has a weekly rhythm and a holiday calendar, so a Saturday kill or a short week distorts raw comparisons. And read it next to carcass weights: heavier cattle can offset a lighter head count, so tonnage can hold even while the kill falls. The weekly Meat Read cites both together for exactly that reason.