0
Two experiments were conducted for the present study (Exp 1 and Exp 2). In Exp 1, 6 experimental treatments based on corn-soybean meal-based were formulated to contain 0, 3, 6, 9, 12 and 15% crude glycerol. All diets were steam conditioned to 65.5ºC and pellet. Pellet mill electrical consumption, production rate (Tm/h), hot-pellet temperature, motor load, feeder rate, conditioning rate and pellet durability were measured. In Exp 2, a total of 182 nursery pigs were used in a 26 days growth trial. Pigs were randomly allotted into one of the 7 dietary treatments with 5 pigs/pen and 5 pens/treatment. Experimental diets included a control without soya oil or crude glycerol addition, the control diet with 3 or 6% of soya oil inclusion, the control diet with 3 or 6% of crude glycerol addition and the control diet with 6 or 12% of a 50:50 soya oil/crude glycerol blend. From day 14 to 21 an indigestible marker (Cr2O3) was added at 0.5% to all treatment diets. Animals were weighed and feed disappearance was determined to determine ADG, ADFI and G:F. Concentration of Cr and GE in the faeces and diet were determined to calculate apparent digestibility of DM, N and GE.
Increasing crude glycerol increased pellet durability indexes up to 9% with no further benefit thereafter (P<0.01). The addition of crude glycerol decreased (P<0.01) production rate (1.20 vs 1.00 Tm/h) and improved production efficiency (8.41 vs 6.72 KWh/Tm), lowered (P<0.01) pelleting and delta temperature, amperage and motor load and improved (P<0.01) pellet durability compared with soya oil and the soya oil/crude glycerol blend treatments. Increasing crude glycerol in pig diets linearly ADG (P=0.03). Nitrogen digestibility tended (P=0.07) to decrease in pigs fed crude glycerol compared with those fed the soya oil treatments. Apparent digestibility of GE tended (P=0.08) to be greater in the pigs fed soya oil compared with pigs fed the soya oil/crude glycerol blends.
It is concluded that the addition of crude glycerol to a corn-soybean meal diet before pelleting may enhance the overall pelleting process by improving total production efficiency and pellet quality without negative effects on growth performance.
C. N. Groesbeck, L. J. McKinney, J. M. DeRouchey, M. D. Tokach, R. D. Goodband, S. S. Dritz, J. L. Nelssen, A.W. Duttlinger, A. C. Fahrenholz and K. C. Behnke. Journal of Animal Science 2008, 86: 2228-2236.
