Effects of tannic acid (Bypro®) on growth performance, carcass characteristics, apparent toal tract digestibility, fecal nitrogen volitization, and meat lipid oxidation of stears fed steam-flaked corn based finishing diets
Effects of a tannic acid blend (ByPro®, Silva Team) added to steam-flaked corn (SFC) fishing diets on beef cattle growth performance, carcass characteristics, nutrient apparent digestibility, fecal nitrogen volatilization and meat lipid oxidation were evaluated. Steers (n = 144, initial BW = 349 ± 25 kg) were assigned to 1 of 3 treatments in a RCBD (12 pens/treatment; 4 steers/pen) and fed ad libitum, once daily for approximately 150 d. Treatments were designed as following: control (CON- no ByPro®), and ByPro® fed at 30 or 60 g of DM/steer daily (30-ByPro® and 60-ByPro®, respectively). Finishing diets based on SFC also contained wet corn gluten feed, alfalfa hay, cottonseed hulls, yellow grease, tannic acid ByPro® premix or cottonseed meal, urea, limestone, and a vitamin and mineral supplement. Initial BW was based on a non-shrunk limit-fed (1.8% of BW for 10 d) weight. Final BW, ADG, and G:F were based on HCW using current study average of dressing percent (62.14%) and corrected for a 4% shrink. Digestibility evaluation was performed on day 92-96 with acid insoluble ash used as internal maker to estimate fecal output. Air-dry surface fecal samples were collected 7-10 d after cattle shipment to harvesting facility, and N:P ratio used to estimated N volatilization (% N intake). Choice strip loins from two harvest groups were obtained. At 21 days of aging steaks were cut, overwrapped packaged, placed in a retail display case where instrument color data was taken. A second steak was also cut, frozen in liquid nitrogen and later evaluated for antioxidant activity in the meat. Data were analyzed using the GLIMMIX procedure of SAS with block (n = 12) as a random effect. Pre-planned contrasts were used to check for linear and quadratic effects of ByPro® inclusion. Data from evaluations of meat quality traits were analyzed using a linear mixed model (PROC MIXED) of SAS. Harvest group was utilized as random variable while carcass QG was incorporated as a covariate. Intake quadratically increased (P = 0.05) from d 0 to 35 with ByPro® inclusion. Intake from d 0 to 105 (P = 0.07) and d 0 to end tended (P = 0.06) to increase linearly, with DMI by steers consuming 60-ByPro® being 3.7% greater than CON. ByPro® inclusion did not affect overall (d 0 to end) carcass-adjusted ADG (P = 0.65) or G:F (P = 0.17), averaging 1.62; 1.66; and 1.64 kg/d, and 0.163; 0.163; and 0.159 kg gain/kg DMI, for CON, 30-ByPro®, and 60-ByPro®, respectively. Carcass characteristics including, HCW (388 kg; P = 0.52), fat thickness (1.47 cm; P = 0.32), longissimus muscle area (94 cm2; P = 0.57), quality grade (88% upper-choice; P = 0.44), yield grade (3; P = 0.29), and liver score (15%; P = 0.13) were not affected by dietary inclusion of ByPro®. Inclusion of ByPro® tended to linearly influence intake of DM (P = 0.07) and OM (P = 0.08) during the digestion phase, while starch, CP, and NDF intake were not influenced (P >0.10). Apparent digestibility of starch decreased linearly (P = 0.03) with ByPro® inclusion (1 percentage unit), while CP tended to decrease linearly (P= 0.09) and OM tended to decrease quadratically (P= 0.09) with inclusion of ByPro®. No differences were observed in fecal nitrogen volatilization as % of intake, g/steer/day, or kg/steer during the finishing phase. An increase (P = 0.002) in metmyoglobin in strip loin steaks was observed as inclusion of ByPro® increased. Only subtle differences were observed for L*, a*, b*, hue angle, saturation, discoloration ratio or deoxymyoglobin were observed among treatments between display days, with the exception of L* values (P = 018). There was an interaction (P < 0.01, SEM = 3.40) between all treatments and retail display day when analyzing oxymyoglobin. All values regardless of treatment declined as display progressed. However, on day 5 control and 30-ByPro® treatments had lower proportions of oxymyoglobin than steaks from 60-ByPro®. No differences were observed when pH and thiobarbituric acid reactive substances were analyzed. Tannic acid (ByPro®) seemed to have more influence on feed intake during the first half of the feeding period when added to beef cattle finishing diets. ByPro® decreased starch, CP, and OM digestion but increased DMI and OMI. ByPro® had no impact on fecal nitrogen volatilization. ByPro® inclusion seemed to have no ability to increase retail meat antioxidant activity but did not negatively affect meat quality.