Evaluation of glycerol , a biodiesel coproduct , in grow-finish pig diets to support growth and improve pork quality

Since 1999 the biodiesel industry has increased exponentially. As a result, the production of crude glycerol, the co-product of biodiesel, has also increased. Two-hundred sixteen crossbred pigs (body weight = 69 + 3.9 lb) were used to determine the effects of long-term (LT) and short-term (ST) feeding of glycerol on growth performance, carcass traits, and pork quality of grow-finish pigs. Pigs were blocked by initial body weight, and pens within blocks were assigned randomly to 1 of 3 dietary treatments in a 4-phase feeding program (24 pens; 9 pigs/pen). Dietary treatments were: Control – a corn-soybean meal based diet (CON); Longterm – CON + 8% glycerol fed throughout the entire experiment (LT); and Short-term – pigs were fed CON for the first 6 weeks followed by CON + 8% glycerol fed during the last 8 weeks of the experiment (ST). Pigs fed LT had higher (P < 0.05) ADG while pigs fed ST tended (P = 0.07) to grow faster than CON. Average daily feed intake was greater (P < 0.05) for pigs assigned to LT compared to CON, while ST-fed pigs had similar ADFI to CON. Gain:feed ratio (G:F) was greater (P < 0.05) for pigs fed ST compared to LT, but both were similar to CON fed pigs. Average daily water disappearance (ADWD) tended to be greater (P = 0.06) for LT-fed pigs compared to CON-fed pigs while ST were similar to both LT and CON-fed pigs. Hot carcass weight (HCW) was greater (P < 0.05) for LT-fed pigs compared to CON, while ST-fed pigs had HCW similar to both LT and CON-fed pigs. Dressing percentage of CON-fed pigs was similar to both LT and ST-fed pigs, but in LT-fed pigs it was higher (P < 0.05) than for ST-fed pigs. Tenth rib BF and loin eye area were not affected by dietary treatment, but there was a trend (P = 0.08) for LT-fed pigs to have lower fat-free lean percentage than CON fed pigs. Short-term glycerol feeding increased (P < 0.05) belly firmness compared to CON, and tended (P = 0.09) to increase belly firmness compared to LT-fed pigs. Dietary treatment had no effect on pork quality of loins based on our taste panel assessment. Grow-finish pigs fed diets containing 8% crude glycerol achieved growth performance similar to pigs fed a typical corn-soybean meal diet. Effects of crude glycerol on carcass traits appear to be limited to improvements in belly firmness with short-term feeding of glycerol.