Dry matter intake, in vivo nutrient digestibility and concentration of minerals in the blood and urine of steers fed rice straw treated with wood ash extract

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Studies to evaluate the effects of feeding rice straw treated with wood ash extract (WAE) on dry matter (DM) intake, in vivo nutrient digestibility and mineral concentrations in the blood and urine were conducted using 12 Boran steers. The steers were randomly assigned to three treatments consisting of untreated, urea treated and WAE treated rice straws in a completely randomised design to estimate the voluntary DM intake. All animals were supplemented with 2 kg of concentrate. An in vivo digestibility trial was performed and pH and mineral contents determined in the urine and blood samples. The average voluntary DM intakes were 5.56, 5.92 and 5.81 kg/day for untreated, urea and ash treated rice straws, respectively, and the mean differences were not significant. Values for DM and organic matter (OM) digestibility of ash treated rice straw (0.633 and 0.684) were higher (P<0.01) than those of urea treated (0.579 and 0.643) and untreated (0.559 and 0.617) straws. Neutral detergent fibre (NDF) digestibility of WAE (0.726) and urea (0.689) treated straws were higher (P<0.05) than untreated (0.606) straw. Calcium concentrations in the blood plasma of steers fed WAE treated (94.8 mg/l) and untreated (99.3 mg/l) straws were lower than those fed on urea treated rice straw (104.9 mg/l). Values of urinary excretion of calcium by the steers fed on WAE (1.88 mg/l) and urea (1.74 mg/l) treated straws were lower (P<0.05) than those fed on untreated (5.93 mg/l) straw. Magnesium concentration in the blood and urine of steers fed on WAE treated rice straw (20.5 and 104.7 mg/l) were lower (P<0.05) than in those fed on untreated (28.7 and 660 mg/l) and urea treated (29.6 and 628 mg/l) rice straw. The blood sodium level was not influenced by the treatments, though the urinary excretion of sodium was lower (P<0.05) for steers fed on WAE treated (620 mg/l) than those fed on urea treated (1689 mg/l) and untreated (1049 mg/l) straws. It is concluded that wood ash extract is effective in improving the nutritive value of low quality roughage and short time feeding of WAE treated straw has no detrimental effect on the mineral concentration in the urine and blood of the animals.