Dry matter and neutral detergent fiber degradation kinetics of roughages in relation to carbohydrate and protein fractions

Nineteen forages were evaluated for their carbohydrate and nitrogen fractions as per Cornell net carbohydrate and protein system (CNCPS), and used as predictors of the in sacco DM and NDF degradability at different intervals in rumen. Total carbohydrate (CHO) among the forages was highest in wheat straw (86.61%) and lowest in berseem (26.51%) whereas the non structural CHO (NSC) was highest in guar fodder (46.07%) and lowest in buffel grass (1.9%). The soluble sugar (CA) fraction of total CHO ranged from 0.81% in wheat straw to 60.73% in fenugreek and starch and pectin (CB₁ fraction) from 4.91% in sehima to 21.55% in maize. Digestible cell wall carbohydrate fraction (CB₂) averaged 47.58% with highest being in sehima (66.45%) and heteropogon grass (64.68%) and lowest in fenugreek (14.02%). The indigestible carbohydrate fraction (CC) was highest in sorghum stover (33.17%) and buffel grass (33.01%) and lowest in sorgum (5.68%) and oats fodder (2.28%). The quickly soluble protein fraction (PA) was highest in bermuda grass (37.88%) and lowest in wheat straw (6.25%) whereas quickly degradable fraction (PB₁) was highest in heteropogon (30.77%) and lowest in wheat straw (2.5%). The PB₂ (most albumins and glutelins) fraction ranged from 22.51 (heteropogon) to 77.68% (cowpea). The cell wall protein (PB₃) was lowest in guar fodder (1.61%) and highest in crysopogon (37.93%). The indigestible protein fraction (PC) was lowest in cowpea (1.25%) and highest in paddy straw (49.31%). It was concluded that DM disappearance rate at 24, 32 and 96 hrs and NDF disappearance rate at 48 and 96 hrs could be very well predicted from the CA, CB₁, and CB₂ fractions, whereas with protein fractions no significant relationship was found. The relationship could be presented in following equation; DMD₂₄ =-45.37 + 1.25 CA + 2.71 CB¹ + 0.72 CB².