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Chemical Composition and Nutritive Value of Poplar Bark^1,2,

University of Minnesota, St. Paul⁴

Abstract

Composition studies showed that poplar bark obtained from a commercial peeling operation contained, on a dry matter basis, 2.2% crude protein, 53.7% crude fiber, 73% cell wall constituents, 59.1% acid detergent fiber and 13.9% permanganate lignin. Phosphorus, potassium and sodium contents of poplar bark were low, but calcium and zinc levels were high in relation to ruminant requirements.

Laboratory silo fermentation studies showed that addition of barley, an Aspergillus oryzae fermentation product or a combination of barley and Aspergillus oryzae fermentation product was not necessary for proper fermentation to take place. Also, moisture contents of 25 to 50% were adequate for proper fermentation.

In the sheep digestion trial, the digestion coefficients for organic matter, crude protein, total carbohydrate, cell contents and energy were greater for rations containing 13% barley and 87% ground poplar bark than for rations containing only poplar bark. TDN and digestible energy contents were also significantly increased when the ration contained 13% barley. These improvements in digestibility and digestible energy contents were due to contributions from barley and not to an influence of barley on the poplar bark. The addition of an Aspergillus oryzae fermentation product did not significantly influence the digestibility of nutrients. The TDN of poplar bark was found to be 36.7% on a dry matter basis.

In the growth trial, sheep fed poplar bark ad libitum and 0.23 kg. of soybean meal daily lost weight. When 0.34 kg. oats and 0.13 kg. soybean meal were fed in addition to ensiled poplar bark, the sheep had an average daily gain of 0.034 kg. during the last 34 days of this 48-day trial.

These data show that poplar bark contains small amounts of available energy in comparison to common feedstuffs. Other by-product feeds, poor quality hay or straw may be better sources of energy during emergency periods than poplar bark.

¹ Paper No. 6830 of the Scientific Journal Series of the Minnesota Agricultural Experiment Station.

² Data taken from a thesis submitted by the senior author to the Graduate School in partial fulfillment of requirements for the degree of Master of Science.

³ N.I.H. Trainee in Nutrition; supported in part by N.I.H. Training Grant GMO 1041 from National Institute of General Medical Sciences.

⁴ Department of Animal Science.