EFFECT OF ENERGY SUPPLEMENTATION OF AMMONIATED BARLEY STRAW ON PERFORMANCE OF CULL BEEF-COWS

Feed value and performance of ruminants fed small grain straws are imp roved when these crop residues are chemically treated with anhydrous a mmonia. Pelleted beet [Beta vulgaris (L.) subsp. vulgaris] pulp (high- fiber) and barley (Hordeum vulgare L.) grain (high-starch) energy supp lementation of ammoniated straw diets may have differing effects on dr y matter (DM) intake, DM digestibility, and animal performance. Thin c ull beef cows (Bos taurus) (n = 96; average weight = 831 lb +/- 21; av erage condition score = 3.8 +/- 0.2, scale 1 to 9) were allowed ad lib itum access to untreated or ammoniated barley straw with or without en ergy supplementation for a 60 d feeding period. Cows were blocked by w eight and randomly allotted to pens (6 cows/pen, 4 pens/treatment) and one of the following treatments: (i) untreated barley straw (BS), (ii ) ammoniated barley straw (AS), (iii) AS and 4.5 lb rolled barley grai n (BAR), and (iv) AS and 5.7 lb pelleted beet pulp with molasses (BEET ). Energy supplements in BAR and BEET were formulated to provide 6.2 M cal of ME/cow each day. All cows were fed 4.3 lb of alfalfa (Medicago sativa L.) hay each day. Cows fed AS had increased (P < 0.05) diet DM intake, diet DM digestibility, digestible DM intake, condition score g ain, final rib fat, and final percentage body fat compared with those fed BS. These same variables and diet DM intake and cow average daily gain were also increased (P < 0.05) for cows fed BAR compared to BEET. Barley grain or pelleted beet pulp with molasses for cows fed AS were equally effective in terms of supplemental feed value and resulting a nimal performance. Barley grain fed at the rate of 4.5 lb/cow each day was not detrimental to diet DM digestibility. The high-fiber content and/or the additional 1.2 lb DM of beet pulp/cow each day, however, ap pears to substitute for forage intake since ammoniated straw DM intake was reduced by 2.0 lb/cow each day compared with cows fed barley grai n.