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Evaluating kraft pulp mill fiber wastes as feedstuffs for beef cattle Bilawchuk, Maureen


Pulp mill fiber wastes (PFW) are cellulosic byproducts from the processing of pulp. PFWs from two pulp mills, Prince George (PG) and Kamloops (K), were examined in a series of experiments to determine their suitability as ruminant feedstuffs. Initially, PFW, a high moisture substrate, was ensiled with a combination of barley (c. 16%-27%), hay (c.15%-26%), whey (c. 1.8%-3%) and urea (c. 0.8%-3%). Ensiling was shown to be an effective storage and preservation technique based on the chemical composition of the silages. In the first animal trial, 20% ensiled PFW was fed to sheep. Based on intake, acid detergent fiber (ADF) content and ADF digestibility, animals were predicted to perform best on PFW silages ensiled with barley (c. 29%), whey (c. 5%) and urea (c. 1.5%). The respective dry matter digestibility (SDMD), neutral detergent fiber digestibility (SNDFD) and acid detergent fiber digestibility (SADFD) coefficients of the PFW silages ranged from 42.01-71.89%, 69.71-118.11%, and 69.45-103.41%. In the second trial, on a dry matter basis 0-10% whey, barley (c. 21%) and urea (c. 1%) was ensiled with PG PFW. Hay based rations containing 20-23% ensiled PFWs were fed to sheep. No significant difference in silage dry matter or fiber digestibility was measured. However, the digestibilities tended to be highest, intake greatest and fermentation better with the 2.7% level of whey. The SDMD and SADFS coefficients for the 2.7% whey silage were respectively 82.09% and 97.74%. In the third experiment, 45% ensiled PFW was fed to four 65-87 day dairy heifers. The PG barley-whey-urea PFW silage-hay ration was acceptable and readily consumed. There was minimal sorting by heifers of PFW from the rations. In the final arriirial trial, 22.2% and 44.4% ensiled PFWs combined with alfalfa/grass hay, barley, canola and a vitamin-mineral premix were fed to 45 Hereford-cross steers. Over the 63 day feeding period, the average daily gain (ADG) of the test animals ranged from 1.5-1.9 kg. The ADG of the barley/hay control and 22% ensiled PG PFW fed groups were significantly higher than the ADG of 44% ensiled PFW and the K PFW fed groups. No significant differences in voluntary intake or feed conversion were detected between treatments. However, the PFWs fed were found to contain macro- and trace minerals, resin acids, chlorinated guaiacols and di-benzofurans. Beef steers which were fed rations containing 44.4% PFW did not exhibit any clinical symptoms of toxicity or illness over the 63-day period feeding period, nor were any detectable residues found in liver tissues biopsied from these animals. When water soluble and organic soluble extracts of the two PFWs were tested with in the Ames-Salmonella test, no mutagenicity was detected. The high digestibilities, intakes, average daily gains and feed conversions suggest that both the PFWs examined are cheap, high energy sources for beef cattle. Regardless, the presence of potentially mutagenic and toxic compounds identified in the PFWs prohibits its use as a feedstuff. Until these chemical contaminants are eliminated, or until the biological significance of such compounds is determined, the use of PFW as a cattle feed can not be recommended.

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