Inadequate Diet Mixing Greatly Reduces Nursery Pig Performance

Pig growth performance may be improved when producers take the time to thoroughly mix feed, according to recent Kansas State University (KSU) research results.

Adequate feed mixing is especially important when low inclusion rate ingredients like crystalline amino acids or other microingredients are used. Researchers note that calculating the differences in average daily gain (ADG) between the treatment groups over a 50-day nursery period suggests pigs consuming thoroughly mixed feed may weigh in at 7 to 15 lb. heavier while eating 4 to 8 lb. less feed than pigs eating a poorly mixed ration.

While the importance of thoroughly mixing diets is often emphasized, little research data is available to quantify the impact of adequate mixing on pig growth performance.

A 28-day trial was conducted to evaluate the effects of mixing time on growth performance of 180 weanling pigs. Six pigs were allotted per pen, with six pens per treatment. Pigs averaged 13.8 lb. and 21 days of age at the beginning of the experiment.

Experimental treatments consisted of mixing a diet for 0, 30, 50, 120 or 330 seconds in a horizontal ribbon mixer. Diets were fed in two phases — Day 0 to 14 and Day 14 to 28 — with diets in both phases containing high levels of synthetic amino acids. Diets in Phase 1 also contained 3.75% fish meal, 15% dried whey and 2,500 parts per million (ppm) zinc from zinc oxide.

Eight samples were collected from the mixer at the completion of respective mixing times. Each 50-lb. bag was labeled and sampled to determine the degree of mixing that occurred as feed was conveyed from the mixer to the bagger.

Degree of mixing is measured by the coefficient of variation (CV). To measure CV, eight to 10 individual samples of a batch of feed are collected and analyzed for salt content. The variation among the analyzed content of the samples is expressed as a percentage of the mean. Therefore, a low CV means more uniformly mixed feed, whereas a high CV indicates poorly mixed feed.

Growth performance was linearly improved in both phases by thoroughly mixing feed. Increasing mix time from Days 0 to 28 increased ADG and gain:feed ratios.

Researchers: Crystal Groesbeck, Robert Goodband, Mike Tokach, Steve Dritz, DVM; Jim Nelssen, Joel DeRouchey and Casey Neill, Kansas State University, Manhattan, KS. Contact Groesbeck at (785) 532-1277.

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