Effects of Conditioning Motor Speed and Diet Form on growth performance of 12-21 kg nursery pigs

Abstract Text: A total of 180 nursery pigs (PIC 327 × 1050; initially 12.6 kg) were used in an 18-d study to determine the effects of conditioning parameters and feed form on pig performance. Diets, either pelleted or mash form, were conditioned by slowing or speeding conditioner rotations per minute (rpm), where higher rpm equates to faster conditioning. All diet formulations were similar. Treatments included: 1) negative control mash diet; 2) positive control pelleted diet conditioned at 60 rpm; 3) pelleted diet conditioned at 30 rpm and reground; 4) pelleted diet conditioned at 60 rpm and reground, and 5) pelleted diet conditioned at 90 rpm and reground.  The differing rpm values among treatments represent the time in the conditioner during processing. Pigs were weaned and fed a common acclimation diet for 21 d prior to the start of the experiment.  Average daily gain and G/F did not differ (P>0.12) between treatments overall, but ADFI was decreased (P=0.03) for pigs fed the pelleted, positive control diet compared to all other diets.  Although no overall treatment effects were significant for ADG or G/F, the experiment was designed more specifically to evaluate treatment differences using preplanned comparisons. When considering preplanned contrasts, we observed that pigs fed mash diets tended to have greater (P=0.10) ADG compared to those fed pelleted and reground diets, suggesting that processing may have had a negative influence on feed utilization, which is a hypothesis that is further supported because pigs fed mash diets tended to have greater (P=0.06) ADG compared to those fed diets that were heat processed, regardless of regrinding. Considering these results, it was not surprising that pigs fed mash diets had greater (P=0.05) ADG and ADFI (P=0.01) than those fed pelleted diets.  When directly comparing diets conditioned at 60 rpm, fed either as whole pellets or reground to mash consistency, pigs fed pelleted diets had improved (P=0.01) G/F due to lower ADFI (P=0.004) but similar ADG (P=0.60). This unexpected negative impact of pelleting on ADG may be due to a negative influence of heat treatment on palatability. The expected improvement in G/F from pelleting (6.8%) was observed, but lost when diets were reground to near original mash particle size. This may indicate that diet form (high quality pellets vs. mash) impacts G/F more than degree of starch gelatinization or other intrinsic factors associated with conditioning ingredients.

Keywords: gelatinization, pelleting, starch