Effect of Alkali Treatment on Intake and Digestion of Barley Straw by Beef Steers

Abstract
Barley straw was treated with sodium hydroxide .(4 kg NaOH/100 kg straw) by ensiling chopped straw mixed with NaOH solution or by pelleting ground straw mixed with NaOH solution. Treated straw was compared with chopped straw, with chopped straw mixed with water and ensiled, and with ground pelleted straw. Each straw preparation was fed ad libitum to rumen fistulated Angus steers and was fed at restricted levels (3.6 kg straw dry matter/day) to nonfistulated steers during three 4-week periods. A supplement of 90 parts soybean meal and 10 parts minerals and vitamins was fed at 1 kg/day. Apparent in vivo digestibilities of dry matter, organic matter and neutral-detergent fiber in the untreated, chopped straw preparations were 55, 57 and 62%, respectively. Digestibility of these components was reduced by 8 to 10 units (P<.01) by grinding and pelleting straw. Alkali treatment of either the chopped or pelleted straw increased digestibility of these components by 10 units compared to the respective nonalkali treated straw. Potential digestibility of straw dry matter in the rumen, estimated by using dacron bags over 72 hr, was increased by alkali treatment from 49 to 84% (P<.01) in chopped straw preparations and from 59 to 73% (P<.05) in pelleted straw preparations. However, the rate constant, a measure of the rapidity of digestion of the potentially digestible fraction, was within the range of .044 to .052 for all straw preparations. The similarity among digestion rate constants indicates that the percentage of potentially digestible dry matter that was digested at a given time was the same among treatments even though potentially digestible dry matter was increased by alkali treatment. Results of in vitro fermentations were similar to those with dacron bags. Intake of straw digestible organic matter was increased from 2 to 3 kg/day (P<.05) by grinding and pelleting or by alkali treatment of straw. The total volume of rumen ingesta did not vary among diets; however, the rumen retention time of undigested particles was reduced 9 hr by either grinding and pelleting or by alkali treatment and 10 hr by a combination of both treatments compared to chopped straw. We concluded that intake of these diets was limited primarily by ruminoreticular fill. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.

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