Performance of Finishing Steers on Corn Silage or Forage Sorghum Silage with Corn Oil Supplementation1
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2010 American Registry of Professional Animal Scientists. Thirty-two crossbred Angus steers (initial BW 524.9 63.3 kg; age 24 mo) were fed a free-choice TMR consisting of 55% corn silage or low-grain sorghum silage and 45% concentrate mix [88.1% ground corn, 10% soybean meal, 1.9% mineral-Rumensin-vitamin premix (Rumensin, Elanco Animal Health, Indianapolis, IN)] on a DM basis, without and with corn oil (7% of DMI). A low-grain forage sorghum silage was compared with a high-grain corn silage. Steers were ranked by BW, randomly assigned to dietary treatments in a 2 2 factorial arrangement, and individually fed with Calan gates (American Calan Inc., Northwood, NH) for 78 d. Steers were implanted with Component TE-IS (trenbolone acetate, estradiol, tylosin tartrate, Ivy Animal Health, Shawnee Mission, KS) on d 1, and initial and final BW were means of 2 consecutive daily unshrunk BW. Steers were slaughtered and USDA QG were determined in a commercial abattoir at the conclusion of the experiment. Rib sections and subcutaneous fat samples were retained for fatty acid analysis. Steer 78-d ADG exhibited a silage treatment interaction (P < 0.05) in which the addition of corn oil depressed ADG for steers fed corn silage but increased ADG for steers fed sorghum silage. Steer DMI was higher for sorghum silage diets than corn silage diets (25.99 vs. 22.10 kg; P < 0.05); however, DMI was not affected (P > 0.10) by corn oil supplementation. Despite increased DMI for steers receiving the sorghum silage treatments, 78-d ADG was higher (P < 0.05) for steers receiving the corn silage treatments (ADG: sorghum silage = 1.41 kg vs. corn silage = 1.75 kg). Corn oil supplementation had no effect (P > 0.10) on concentrations of the conjugated linoleic acid isomer cis-9, trans-11 in longissimus dorsi or subcutaneous fat samples. Steers fed corn oil had greater (P < 0.05) concentrations of the conjugated linoleic acid isomer trans-10, cis-12 in subcutaneous tissue. Carcass traits were unaffected (P > 0.10) by treatments, except for QG (12 = US Choice-), which was greater for sorghum silage than corn silage. Corn oil supplementation had no effect (P > 0.10) on the YG, QG, or hot carcass weight of steers. Corn oil supplementation had no effect on steer performance or on conjugated linoleic acid isomer concentrations.
