TREATMENT AND STANDARDIZATION OF FIBEROUS BY-PRODUCTS FOR FINISHING BEEF CATTLE
Gentry, Wesley Wayne
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Cereal grain production and the wet and dry milling industries have yielded a plentiful supply of fibrous by-products for use in livestock production. These by-products can be treated both chemically and physically to alter their digestibility, and effects on animal performance and rumination behavior. Three experiments were conducted to evaluate the treatment of fibrous by-products in steam-flaked corn (SFC)-based diets on in situ digestibility, animal metabolism, animal performance, carcass characteristics, and rumination behavior. Experiment 1 utilized three ruminally cannulated steers (621 ± 3.6 kg of BW) to evaluate in situ digestibility of calcium hydroxide (CH) treated corn stalks and sorghum wet distillers grains plus solubles (SWDGS). Treatments included: untreated SWDGS (S), CH treated SWDGS (2.67 % DM basis; S-CH), untreated corn stalks (C), and CH treated corn stalks (C-CH). All treatments were placed at once in the ventral rumen space three ruminally cannulated steers and incubated in the rumen for 0, 6, 12, 24, 36, and 48 h. Effective ruminal degradability (ERD) of DM was greater (P < 0.01) for C-CH than C, with no difference (P = 0.38) between S and S-CH. No differences (P = 0.27) were observed for ERD of OM between S and S-CH. However, S was greater (P = 0.04) than S-CH for ERD of NDF. Experiment 2 utilized six ruminally cannulated steers (444 ± 4.0 kg of BW) in a 3 × 3 replicated Latin Square design to evaluate the effects of treating 30% SWDGS in finishing diets. Treatment diets were SFC-based and included: 30% corn wet distillers grains plus solubles (CDG), 30% SWDGS (SDG), and 30% CH treated SWDGS (2.67 DM basis; SDG-CH). Periods included 17 d of diet adaptation and 4 d of subsequent fecal and rumen fluid collection. No differences were observed for DM intake (P = 0.47) or apparent total tract digestibility of DM, OM, ADF, starch, or nitrogen (P ≥ 0.15) for steers consuming CDG, SDG, or SDG-CH. However, steers consuming SDG-CH tended (P = 0.07) to have a greater apparent total tract digestibility of NDF. Steers consuming CDG had the greatest (P < 0.01) total ruminal VFA concentration, followed by steers consuming SDG-CH, with steers consuming SDG having the lowest. Experiment 3 utilized fifty-one individually fed steers (initial BW = 385 ± 3.6 kg) to evaluate the effects of corn stalk (CS) particle size and inclusion rate in SFC-based finishing diets on animal performance and rumination behavior. Corn stalks were passed through a tub grinder equipped with a 7.62 cm screen once (LG-CS), or twice (SG-CS) to achieve different particles sizes. Dietary treatments included: 30% wet corn gluten feed (WCGF) and 5% SG-CS (5SG), 30% WCGF and 5% LG-CS (5LG), and 25% WCGF with 10% SG-CS (10SG). The Penn State Particle Separator was used to separate ingredients and treatment diets, and to estimate physically effective NDF (peNDF). Steers were outfitted with continuous rumination and activity monitoring collars on d 70. Long grind corn stalks contained more (P < 0.01) peNDF than SG-CS, and the 10SG diet contained more (P = 0.03) peNDF than the 5LG and 5SG diets. Dry matter intake was greatest (P = 0.03) for steers consuming 5LG, and least for steers consuming 10SG with cattle consuming 5SG being intermediate. Carcass-adjusted ADG and G:F was greatest (P ≤ 0.03) for steers consuming 5LG and 5SG compared to 10SG. Hot carcass weight tended (P = 0.10) to be greatest for steers consuming 5LG, and least for steers consuming 10SG with 5SG being intermediate. Dressing percent was greater (P = 0.01) for steers consuming 5LG and 5SG than 10SG. Minutes of rumination per day were greatest (P = 0.01) for steers consuming 10SG, followed by 5LG, and lowest for 5SG. Treating SWDGS with CH showed improvement compared to untreated SWDGS in finishing diets. Increasing particle size of roughage may be a means to decrease roughage inclusion rate while maintaining rumination and performance.