Ruminal nutrient degradation of concentrates and their protein and carbohydrate fractions of the cornell net carbohydrate and protein system | Ruminaler Nährstoffabbau von Kraftfutter-mitteln und deren Protein- und Kohlen- Hydrat-fraktionen nach dem Cornell NET carbohydrate and protein system

In the present investigation representative samples of the most important concentrates used in Austria were taken from the concentrate industry, in agricultural research institutes as well as from farms (n = 85). The feedstuffs were devided into 7 groups: 1. Cereals (barley, wheat, oats, rye, triticale, maize, CCM, high moisture corn, sorghum) 2. By-products (wheat feed flour, wheat bran, pressed beet pulp, dried beet pulp, soybean hulls) 3. Roots and tubers (fodder beet, potato, manioc) 4. Legume and oil seeds (faba beans, peas, soybean, rapeseed, sunflower seed) 5. Oil seed meals extracted (soybean meal 44 and 50 and protected, rapeseed meal, rapeseed meal protected, sunflower meal) 6. Oil seed meals (rapeseed meal, sunflower meal, pumpkin kernel meal, palm kernel meal) 7. By-products of alcohol and starch industry (brewer's ensiled grains, brewer's dried grains, wheat distiller's dried grains, maize distiller's dried grains, maize gluten feed, maize gluten meal) Additionally to Weende crude nutrients and Van Soest cell wall constituents the in situ degradability was investigated using 4 rumen fistulated steers, based on the exponential model of Orskov & McDonald (1979). Further, the protein and carbohydrate fractions according to the Cornell Net Carbohydrate and Protein System (CNCPS, Sniffen et al. 1992) were analysed, too. The feedstuffs and groups of feedstuffs significantly and typically differed in their content of the 5 protein fractions (A, B1, B2, B3, C; range of immediately soluble in the rumen to undegradable by rumen microbes). The 5 protein fractions were 22, 6, 49, 16 and 7 % of total N on an average. The content of fraction A is especially high with ensiled concen- trates (CCM, brewer's ensiled grains), in fresh roots and tubers (fodder beet, potato) as well as with legume seeds. On the other hand there are higher proportions of fractions B3 und C (slowly degradable and undegradable in the rumen) in dried products (brewer's dried grains, distiller's dried grains, dried beet pulp, maize), in 'protected' protein concentrates as well as in rapeseed products. Approximately half of total protein is of medium degradability (B2), there are however significant differences between the feedstuffs (impact of drying and species). The processing of feedstuffs (protection of protein, drying) results in a shift towards fractions of lower degradability. This corresponds well with the degradability data determined with the in situ nylon bag technique. The cereals are characterized by a high degradability rate (29 %/h), besides of maize and sorghum (7 and 6 %/h). The degradability rate of legume and oil seeds is some-what lower (13 %/h), the feedstuffs of lowest degradability rate being extracted oil seed meals (8 %/h) and dried by-products of the alcohol industry (6 %/h). Both procedures applied in the present investigation, the CNCPS and the in situ nylon bag technique, proved to be suitable methods to describe the nutrient supply for rumen microbes.