Effects of Pelleting Conditioner Retention Time on Nursery Pig Growth Performance

Diet form had a greater effect on feed conversion than conditioner retention time, according to this new study from Kansas State University.
calendar icon 14 April 2015
clock icon 4 minute read

A total of 180 nursery pigs (PIC 327 × 1050; initially 12.6kg) were used in an 18-day study to determine the effects of pellet mill conditioning parameters and feed form on pig performance, reports C.K. Jones of Kansas State University in Journal of Animal Science.

All diets were similar, the researchers explain, and different feed processing parameters were used to create experimental treatments.

Factors considered were:

  • conditioning time (15, 30 or 60 seconds) and
  • feed form (mash or pelleted).

To remove the confounding factor of feed form, pelleted samples were reground to a similar particle size as the mash diet.

Treatments included:

  1. mash diet without thermal processing (negative control)
  2. pelleted diet conditioned for 30 seconds (positive control)
  3. pelleted diet conditioned for 15 seconds and reground
  4. pelleted diet conditioned for 30 seconds and reground, and
  5. pelleted diet conditioned for 60 seconds and reground.

Pigs were weaned and fed a common acclimation diet for 21 days before the start of the experiment.

Growth and feed disappearance were then measured for 18 days. All diets had similar levels of percentage total starch but thermally processed diets had a 1.67 to 1.87-fold increase in percentage gelatinised starch compared to the mash diet.

Average daily gain and gain:feed ratio did not differ between treatments overall, but pigs fed the positive control pelleted diet had decreased average daily feed intake (P<0.05) compared to pigs fed all other diets.

Pre-planned contrasts revealed that pigs fed mash diets tended to have greater average daily gain (P<0.10) than those fed pelleted and re-ground diets. This suggests that processing may have had a negative influence on feed utilisation, which is further supported by the finding that pigs fed mash diets tended to have greater average daily gain (P<0.10) than those fed diets that were thermally processed, regardless of regrinding.

Considering these results, it was not surprising that pigs fed mash diets had greater average daily gain and average daily feed intake (P<0.05) than those fed pelleted diets.

When directly comparing diets conditioned at 60rpm, fed either as whole pellets or reground to mash consistency, pigs fed pelleted diets had improved gain:feed ratio (P<0.05) due to lower average daily feed intake (P<0.05) but similar average daily gain.

The expected improvement in gain:feed ratio from pelleting (6.8 per cent) was observed but lost when diets were reground to near original mash particle size.

Jones and co-authors commented this may indicate that diet form from the actual pelleting process impacts gain:feed ratio more than conditioner retention time.


Lewis L.L., C.R. Stark, A.C. Fahrenholz, M.A.D. Goncalves, J.M. DeRouchey and C.K. Jones. 2015. Effects of pelleting conditioner retention time on nursery pig growth performance. Journal of Animal Science. 93:1098-1102.

Further Reading

You can view the full report (fee payable) by clicking here.

April 2015

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