Fibrous and Nonfibrous Carbohydrate Supplementation to Ruminants Grazing Forage from Small Grain Crops

Animal performance, N balance, and forage digestibility effects of fibrous (beet pulp) and nonfibrous (corn) carbohydrate supplementation to ruminants grazing small-grain forages was studied. Similar supplements were used in 3 studies: no supplement (NS), cracked corn (CN), and beet pulp (BP) at 0.5% BW. The effect of supplementation on ADG of yearling heifers (n = 48, BW = 267 ± 22 kg) grazing triticale (CP = 20 ± 1.2%) or wheat (CP = 27 ± 8.1%) was investigated in Exp. 1. Diet digestion and N metabolism by lambs (n = 12, BW = 36 ± 3.7 kg) consuming fresh triticale forage were studied in Exp. 2. The effect of supplementation on IVDMD of triticale forage was investigated in Exp. 3. In Exp. 1, neither supplement (P = 0.76) nor crop grazed (P = 0.64) affected ADG of heifers. In Exp. 2, BP improved N retention (g/d; P = 0.03), NDF, and ADF digestion (P = 0.01) when compared with NS and CN. Treatment BP improved DM digestion compared with NS (P = 0.05) and tended to improve DM digestion compared with CN. In Exp. 3, rumen pH was lower in BP and CN as compared with NS (P < 0.01), and IVDMD was lower (P < 0.01) in treatment CN as compared with NS and BP. Fibrous carbohydrate supplementation to ruminants grazing triticale forage improved rumen bioavailability of nutrients. Correspondingly, supplementation with high carbohydrate showed no benefits in terms of N retention, ADF, or NDF digestion and decreased IVDMD. Neither supplement affected animal performance when animals on high-quality small-grain forage were experiencing compensatory gain.