Impact of feeding increasing crude glycerine levels on growth performance, glycerine kinase gene expression, nutrient digestibility and litter quality in broiler chickens

A study was conducted to determine the effects of dietary crude glycerine (CG) on growth performance, gene expression of glycerine kinase (GK), nutrient digestibility, and litter quality in broiler chickens. A total of 400 one-day old broiler chickens were randomly assigned to 4 diets containing 0, 70, 140, or 210g CG/kg with 5 replicate pens and 20 broiler chickens per pen. Diets were formulated by substituting CG for corn, on an equal apparent metabolizable energy (AMEn) basis, with similar crude protein and amino acid contents. Feed and water intake, weight gain, excreta moisture, litter score, and mortality were recorded weekly. The total tract apparent digestibility (TTAD) of nutrients and energy was determined at d 28, and GK expression was determined in liver homogenates at d 42. The overall feed intake and BW gain were affected quadratically (P<0.001), with broiler chickens fed the diet with 70gCG/kg diet showing the greater values, whereas feed conversion ratio and water intake increased linearly (P<0.05 and 0.001, respectively) with increasing dietary CG. The linear increase (P<0.01) in excreta moisture resulted in a linear reduction (P<0.001) of litter quality with the increment of CG. At d 28, the TTAD of dry matter, organic matter, and nitrogen free extract were not affected; however, the dietary AMEn content tended to decrease (P=0.07) when CG increased to 210g/kg diet. Relative GK mRNA increased for CG inclusion up to 140g/kg diet and reached a plateau thereafter, indicating a limiting capacity for dietary CG activation. In conclusion, dietary inclusion of CG up to 70g/kg may have beneficial effects on growth performance of broiler chickens. Dietary inclusion up to 140gCG/kg may be efficiently utilized, whereas greater inclusion (>140gCG/kg) may impair growth of broiler chickens, reduce litter quality, and increase mortality.