Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Animal and Veterinary Sciences

Committee Member

Dr. Nathan M. Long

Committee Member

Dr. Susan K. Duckett

Committee Member

Dr. John G. Andrae

Committee Member

Dr. Clint R. Krehbiel

Abstract

The objective of this study was to determine if supplementation of a rumen undegradable unsaturated fatty acid (FA) source would improve marbling in early-weaned steers. All steers (Angus, n = 23 and Angus × Hereford, n = 24) were weaned at 150 ± 5 d of age. Steers were blocked by BW and breed then randomly assigned to either control (CON; 1.5 kg of corn gluten feed (CGF), n = 23) or a rumen undegradable fat isocaloric supplementation (RUF; 200 g of Megalac-R in 1.06 kg of CGF, n = 24) for 110 d (fed 5 d/wk). All steers had ad libitum access to pastures throughout treatment. Steer BW and blood samples were collected at 0, 55, and 110 d of supplementation, and real-time carcass ultrasound measurements were collected at d 110. Following treatment, steers were transported to Oklahoma State University for finishing and subsequent harvesting at a commercial plant. All data were analyzed using PROC MIXED procedure of SAS either as a repeated measures or ANOVA, depending on response variables. There were no significant changes in BW from beginning of treatment to harvest due to treatment. Ultrasound data showed that RUF steers tended to have more intramuscular fat (P = 0.08) than CON steers at d 110. Serum FA concentration showed a treatment × day interaction (P < 0.02) on 16:0, 18:0, 18:1 c-9, 18:2, 20:4, and total FA. These specific FA concentrations increased throughout treatment in CON steers, but there was a greater increase in the concentration of RUF steers. Serum triglyceride and cholesterol concentrations were increased (P < 0.01) on d 55 and 110 in RUF steers compared to CON steers. Serum leptin concentration in RUF steers was greater (P < 0.01) than CON steers at d 110. Marbling scores of the RUF carcasses tended (P = 0.09) to be higher than CON carcasses. There was a tendency (P = 0.09) for increased percent total lipids in RUF steaks compared to CON steaks. There was also a tendency (P = 0.06) for RUF steers to have an increased percentage of 20 - 30 um adipocytes in their intramuscular depots compared to CON steers. The results of this study indicate that supplementation of rumen undegradable unsaturated FA may positively impact marbling deposition in early-weaned steers.

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