Effects of grain processing and dietary lipid source on performance, carcass characteristics, plasma fatty acids, and sensory properties of steaks from finishing cattle.

An experiment was conducted to evaluate the effects of grain processing and lipid addition to finishing diets on cattle performance, carcass characteristics, and meat quality. Eighty Hereford x Angus steers (384 kg +/- 17 kg of BW) were fed diets containing steam-flaked corn (SFC) or dry-rolled corn (DRC) with and without the addition of tallow (SFC/Fat and DRC/Fat) or steam-flaked corn with ground flaxseed (SFC/Flax). Ribeye steaks from steers fed SFC, SFC/Fat, or SFC/ Flax were used to evaluate the effects of fat source on meat quality. Cattle fed SFC and SFC/Fat tended to have greater ADG, G:F, HCW, and USDA yield grade, compared with those fed DRC and DRC/Fat (P < 0.10). Steaks from steers fed SFC/Flax developed a detectable off-flavor (P < 0.05) compared with steaks from steers fed SFC and SFC/Fat, and steaks from steers fed SFC retained desirable color longer than those from steers fed SFC/Flax (P < 0.05). Feeding SFC/Flax increased deposition of alpha-linolenic acid in muscle tissue compared with feeding SFC or SFC/Fat (P < 0.01). Dietary treatment did not cause differences in tenderness, juiciness, or flavor intensity. Ground flaxseed can replace tallow in finishing diets without loss in performance, but flax may affect flavor and color stability of beef. Feeding flaxseed can effectively alter composition of carcass tissues to yield beef that is high in n-3 fatty acids.

Effect of Maillard reaction products on ruminal and fecal acid-resistant E. coli, total coliforms, VFA profiles, and pH in steers.

Six ruminally cannulated Angus-cross steers (362 kg) were used in a replicated 3 x 3 Latin square design to determine effects of supplementing Maillard reaction products (MRP) on acid-resistant E. coli and coliform populations. Steers were fed roughage-based diets supplemented (DM basis) with either 10% soybean meal (SBM), 10% nonenzymatically browned SBM (NESBM), or 10% SBM top-dressed with 45 g of a lysine-dextrose Maillard reaction product (LD-MRP). Equal weights of dextrose, lysine hydrochloride, and deionized water were refluxed to produce the LD-MRP. The NESBM was manufactured by treating SBM with invertase enzyme, followed by heating to induce nonenzymatic browning. Steers were allowed slightly less than ad libitum access to diets fed twice daily and were adapted to their respective treatments within 10 d. On d 11, ruminal and fecal samples were collected at 0, 2, 4, 6, 8, and 12 h after feeding from each of the steers and transported to the laboratory for microbial analysis. Ruminal samples and feces were analyzed for pH and VFA, and both ruminal fluid and feces were tested for acid-resistant E. coli and total coliforms by incubating samples in tryptic soy broth adjusted to pH 2, 4, and 7. Ruminal pH and total VFA concentrations did not differ among treatments. The molar proportion of ruminal acetate was higher (P < 0.05) for steers receiving NESBM than for steers receiving SBM and LD-MRP. At pH 4, steers that received NESBM had lower (P < 0.05) ruminal populations of E. coli and total coliforms than steers that received SBM. No differences were observed for ruminal E. coli and total coliforms at pH 2 and 7. Fecal pH was lower (P < 0.05) for steers fed NESBM than for steers fed SBM or LD-MRP. Molar proportions of fecal acetate were lower (P < 0.05) and proportions of butyrate and isovalerate were higher (P < 0.05) for steers fed NESBM compared with steers fed SBM. Fecal E. coli at pH 4 was lower (P < 0.05) for steers fed NESBM than for steers fed LD-MRP. Fecal E. coli and total coliforms at pH 2 and 7 did not differ among treatments. Dietary MRP had limited effectiveness at decreasing acid-resistant coliforms in the rumen and feces of cattle. Acid resistance in coliforms may depend on protein availability.

Combinations of alfalfa hay and wet corn gluten feed in limit-fed growing diets for beef cattle.

Two experiments were conducted to evaluate the effects of alfalfa hay (AH) and wet corn gluten feed (WCGF) combinations on ADG and gain efficiency of cattle limit-fed growing diets. In Exp. 1, crossbred beef steers (n = 220; initial BW = 262 kg) were limit-fed diets consisting of steam-flaked corn and 40% WCGF (DM basis) with 0, 10, or 20% ground AH (0AH, 10AH, and 20AH, respectively). A fourth diet containing 20% ground AH and steam-flaked corn served as a control. All diets were fed once daily at 1.8% of BW (DM basis). Growing period ADG, gain efficiency, and dietary NE calculated from performance data decreased linearly (P < 0.01) with addition of AH to diets containing WCGF. Rate of DMI increased linearly (P < 0.05) with AH addition to diets containing WCGF. Following the growing period, steers were finished on a common diet offered ad libitum. Gain efficiencies during the finishing period were higher (P < 0.05) for steers fed the 20AH diet than for steers fed the control diet. In Exp. 2, crossbred beef heifers (n = 339; initial BW = 277 kg) were limit-fed diets containing steam-flaked corn with 10, 20, or 30% ground AH and 0, 40, or 68% WCGF in a 3 x 3 factorial arrangement, fed once daily at 1.6% of BW (DM basis). An AH x WCGF interaction occurred (P < 0.05) for growing period ADG and gain efficiency. Increasing AH or WCGF decreased cattle ADG, gain efficiency, and dietary NE with the exception of heifers fed 30AH/40WCGF, which had ADG that did not differ (P > 0.10) from that of heifers fed 20AH/0WCGF or 30AH/0WCGF, and which had greater gain efficiencies (P < 0.05) than heifers fed 30AH/0WCGF. Rate of DMI increased linearly (P < 0.01) with increasing AH and decreased linearly (P < 0.01) with increasing WCGF. Heifers were finished on diets containing 33% WCGF with 0 or 0.5% added urea (DM basis) offered ad libitum. Increasing WCGF in growing diets tended (linear, P < 0.10) to increase finishing ADG and gain efficiency, whereas increasing AH decreased (linear, P < 0.05) kidney, pelvic, and heart fat, and the percentage of carcasses grading USDA Prime. Urea tended to increase ADG (P < 0.10), but decreased (P < 0.04) the percentage of carcasses grading USDA Choice. Results suggest that the value of WCGF relative to steam-flaked corn in limit-fed growing diets might be improved in diets containing 30% AH relative to diets containing 10 or 20% AH.

Evaluation of finishing performance, carcass characteristics, acid-resistant E. coli and total coliforms from steers fed combinations of wet corn gluten feed and steam-flaked corn.

Crossbred beef steers (n = 615) were used in a 152-d experiment to compare steam-flaked corn (SFC) diets containing 0, 30, or 60% wet corn gluten feed (WCGF). On d 114 to 118, ruminal and fecal samples were collected from 180 steers and analyzed for pH, VFA, and total and acid-resistant Escherichia coli and coliforms. Acid resistance of E. coli and coliform populations was determined by exposure of the samples for 1 h in pH 2, 4, and 7 citric acid/sodium phosphate buffers. Increasing levels of WCGF linearly decreased total ruminal VFA (P = 0.01) and total fecal VFA (P = 0.06), but linearly increased ruminal and fecal acetate:propionate (P < 0.01) ratio and ruminal and fecal pH (P < 0.05). Feeding increasing WCGF levels resulted in a quadratic response (P < 0.05) with respect to numbers of ruminal E. coli and total coliform populations resistant to pH 4 exposure. Steers fed 30% WCGF had higher (0.7 log units) ruminal E. coli and total coliforms after exposure at pH 4 compared to steers fed 0 or 60% WCGF. Populations of E. coli and total coliforms at pH 2 and 7 were similar for all dietary treatments. Dietary WCGF linearly increased DMI (P = 0.07) and liver abscesses (P = 0.03) and linearly decreased dietary NEg (P = 0.02). Average daily gain and feed efficiencies were greatest when steers were offered 30% WCGF (quadratic, P < 0.05). Dietary manipulations that reduce acid concentrations may not correspond to changes in acid resistance of E. coli and total coliform populations detected in the gastrointestinal tracts of cattle. Moderate levels of WCGF complement SFC finishing diets.