Total Mixed Ration

What is Total Mixed Ration?

A Total Mixed Ration (TMR) is a feeding system that combines all ration ingredients — forages, concentrates, protein supplements, minerals, vitamins, and additives — into a single, uniformly mixed feed. The goal is to prevent cows from sorting (selecting preferred components) and ensure every bite provides a nutritionally balanced diet.

A well-formulated TMR is based on the cow's nutritional requirements at her current stage of lactation, body condition, and production level. The ration is balanced using computer software (e.g., PMMP, WinFeed) that optimizes for nutrient requirements, ingredient costs, and ingredient availability.

TMR mixing requires proper equipment — a horizontal or vertical mixer wagon that chops long forage to appropriate particle size and blends all ingredients uniformly. Mixing time is typically 3–5 minutes after all ingredients are added. Over-mixing (>8 minutes) causes particle size reduction and separation.

TMR management includes: consistent delivery time (within 30 minutes daily), feed push-up 6–8 times daily, adequate bunk space (30 inches/cow), removing refused feed, and maintaining mixer calibration. Poor TMR management leads to sorting, uneven nutrition, and reduced performance.

The Penn State Particle Separator

The Penn State Particle Separator is the standard tool for assessing TMR particle size. It's a three-sieve device that separates feed into four particle size fractions: >19 mm (long particles), 8–19 mm (medium), 1.18–8 mm (short), and <1.18 mm (fines). Target distribution for a lactating cow TMR: top sieve 2–8%, middle sieve 30–50%, bottom sieve 10–20%, pan 30–40%. If the top sieve >10%, cows will sort out long particles. If the pan >50%, the ration is too fine and effective fiber is insufficient, increasing acidosis risk. Check particle size at least weekly — it changes with forage maturity, chop length, and mixing time.

TMR vs Component Feeding

Component feeding (separate feeding of forage and concentrate) allows cows to select what they prefer, which often means over-eating grain and under-eating forage. This leads to: ruminal acidosis (from slug feeding grain), reduced fiber digestion, milk fat depression, and uneven nutrition across the herd. TMR feeding eliminates sorting by blending everything uniformly. Research consistently shows TMR improves DMI by 5–10%, increases milk production by 2–5 lbs/day, improves milk fat test by 0.1–0.3 percentage points, and reduces feed waste by 5–8% compared to component feeding. The economic benefit for a 200-cow herd is $30,000–$60,000/year.

Common TMR Mistakes

(1) Over-mixing — mixing longer than 8 minutes chops particles too fine, reducing effective fiber and increasing sorting. (2) Inconsistent delivery time — feeding more than 30 minutes off-schedule reduces DMI by 2–3 lbs/day. (3) Not pushing up feed — cows sort feed as they eat; without push-up, the most palatable components get pushed to the edges and the least palatable remain in the bunk. (4) Ignoring refusals — refused feed should be 2–4% of offered feed; more indicates over-feeding, less indicates under-feeding or sorting. (5) Not calibrating the mixer — inaccurate weighing leads to nutrient imbalances that are expensive to correct.