An experiment examining the effects of feed processing parameters on the performance of nursery pigs was presented at the Swine Industry by L.L. Lewis of Kansas State University and co-authors there and at North Carolina State University.

They used a total of 180 nursery pigs (PIC 327 × 1050; initially 27.8 lb) in an 18-day study.

All diets were the same corn, dried distillers grains with solubles (DDGS) and soybean meal-based formulation with different processing parameters used to create the experimental treatments. Treatments included:

1. negative control mash diet
2. positive control pelleted diet conditioned at 60rpm
3. pelleted diet conditioned at 30rpm and reground
4. pelleted diet conditioned at 60rpm and reground, and
5. pelleted diet conditioned at 90rpm and reground.

The different rpm values among treatments represent the time in the conditioner during processing. The lower the rpm value, the longer time feed was in the conditioner.

Pigs were weaned and fed a common acclimatisation diet for 21 days prior to the start of the experiment.

Average daily gain and feed:gain ratio did not differ (P>0.12) between treatments overall but average daily feed intake decreased (P=0.03) for pigs fed the pelleted, positive control diet compared with all other diets.

Although no overall treatment effects were significant for average daily gain or feed:gain ratio, the experiment was designed more specifically to evaluate treatment differences using pre-planned comparisons.

When considering pre-planned contrasts, the researchers observed that pigs fed mash diets tended to have greater (P=0.10) average daily gain than those fed pelleted and re-ground diets, suggesting that processing may have had a negative influence on feed utilisation, a hypothesis that is further supported because pigs fed mash diets tended to have greater (P=0.06) average daily gain than those fed diets that were heat-processed, regardless of re-grinding.

Considering these results, it was not surprising that pigs fed mash diets had greater (P=0.05) average daily gain and average daily feed intake (P=0.01) 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 (P=0.01) feed:gain ratio due to lower average daily feed intake (P=0.004) but similar average daily gain (P=0.60).

This unexpected negative impact of pelleting on average daily gain may be due to a negative influence of heat treatment on palatability.

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

Lewis and co-authors concluded this result may indicate that diet form (high-quality pellets versus mash) affects feed:gain ratio more than degree of starch gelatinisation or other intrinsic factors associated with conditioning ingredients.

Reference

Lewis L.L., C.K. Jones, A.C. Fahrenholz, M.A.D. Goncalves, C.R. Stark and J.M. DeRouchey 2013. Feed processing parameters and their effects on nursery pig growth performance. Proceedings of 2013 Kansas Swine Day, p90-94.

March 2014