There is a need to standardize the NDF procedure. Procedures have varied because of the use of different amylases in attempts to remove starch interference. The original Bacillus subtilis enzyme Type IIIA (XIA) no longer is available and has been replaced by a less effective enzyme. For fiber work, a new enzyme has received AOAC approval and is rapidly displacing other amylases in analytical work. This enzyme is available from Sigma (Number A3306; Sigma Chemical Co., St. Louis, MO). The original publications for NDF and ADF (43, 53) and the Agricultural Handbook 379 (14) are obsolete and of historical interest only. Up to date procedures should be followed. Triethylene glycol has replaced 2-ethoxyethanol because of reported toxicity. Considerable development in regard to fiber methods has occurred over the past 5 yr because of a redefinition of dietary fiber for man and monogastric animals that includes lignin and all polysaccharides resistant to mammalian digestive enzymes. In addition to NDF, new improved methods for total dietary fiber and nonstarch polysaccharides including pectin and beta-glucans now are available. The latter are also of interest in rumen fermentation. Unlike starch, their fermentations are like that of cellulose but faster and yield no lactic acid. Physical and biological properties of carbohydrate fractions are more important than their intrinsic composition.

Two giant pandas were used to assess the utilization of bamboo as a feedstuff. Three 1-week-long digestion trials were conducted during which feed intake and fecal output were recorded. Passage of digesta was measured from both fluid and particulate markers administered at feeding. Results indicate that the giant panda, although highly specialized for the consumption of bamboo, is a very inefficient digester of bamboo. The pandas consumed up to 6% of body weight in dry matter per day, with bamboo dry matter digestibility averaging less than 20%. Apparent digestion coefficients for the structural carbohydrates of bamboo (27% for hemicellulose and 8% for cellulose) indicate that, unlike most herbivores, pandas do not rely heavily on the microbial degradation of plant material to fulfill their nutritional requirements. Additionally, the passage of digesta through the gastrointestinal tract of the panda was extremely rapid, with complete clearance of markers in less than 12 hours. The giant panda seems to have specialized to a feed source high in plant fiber without extensive modification of the digestive tract by selectivity in feeding, effective mastication, ingestion of large quantities, digestion of cellular contents rather than cell walls and rapid fecal excretion of the undigested residue.

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Protons have long been recognized as low LET radiation in radiotherapy. However, a detailed account of LET (linear energy transfer) and RBE (relative biological effectiveness) changes with incident beam energy and depth in tissue is still unresolved. This issue is particularly important for treatment planning, where the physical dose prescription is calculated from a RBE using cobalt as the reference radiation. Any significant RBE changes with energy or depth will be important to incorporate in treatment planning. In this paper we present microdosimetry spectra for the proton beam at various energies and depths and compare the results to cell survival studies performed at Loma Linda. An empirically determined biological weighting function that depends on lineal energy is used to correlate the microdosimetry spectra with cell survival data. We conclude that the variations in measured RBE with beam energy and depth are small until the distal edge of the beam is reached. On the distal edge, protons achieve stopping powers as high as 100 keV/micron, which is reflected in the lineal energy spectra taken there. Lineal energy spectra 5 cm beyond the distal edge of the Bragg peak also show a high LET component but at a dose rate 600 times smaller than observed inside the proton field.