Sorting steals the peNDF

The nutritionist balanced peNDF on paper. The mixer ran its minutes. Then cows sorted: grain and fines first, long forage left in ridges. What left the wagon is not what left the bunk in the cow. Sorting steals physically effective fiber from the diet she actually ate.

Particle-size tools (Penn State shaker and cousins) compare fresh TMR to refusals. When the refusal is heavier in long particles than the as-fed mix, cows have been eating a finer, more fermentable ration than formulated. Chewing time drops, the mat thins, and starch hits faster — the same family of risk as overmixing and empty-bunk starch events.

Dry, fluffy long hay that floats out of a wet TMR, overprocessed forage that still leaves “sticks,” slug feeding after empty bunks, and poor push-ups all invite selection. Watch the bunk face as feed disappears — clean uniform disappearance, or a lace of long stems. Dominance can shape who gets first pick, but the visual that matters is the bunk face and the refusal map, not a rigid two-hour clock.

Shake as-fed and refusal samples on the same schedule for a few days. Fix delivery before you rewrite peNDF targets — mix uniformity, moisture, sequence, and push-up timing are the first levers.