Document Type
Thesis - University Access Only
Award Date
2009
Degree Name
Doctor of Philosophy (PhD)
Department / School
Animal Science
Abstract
The objective of this research was to determine if management of dietary protein and energy in feedlot diets would influence adipose deposition and marbling. Two studies were conducted: 1) Timed protein restrictions in feedlot diets to alter adipose deposition with the goal to increase marbling in beef carcasses; 2) Determining if altering feeding program could improve marbling, flavor, and tenderness in beef. For study 1, ninety-six Angus-cross and 96 Limousin-cross steers were used in two separate feeding periods. Within each breed type, the steers were assigned to twelve pens, eight head per pen with three pens randomly assigned to one of four treatments. Treatments utilized two dietary crude protein levels (CP), Low (11.7 % ± 0.5) and High (15.5 % ± 0.6), delivered during two feeding phases, Initial and Final Phase. The change from Initial Phase (IP) to Final Phase (FP) occurred when the steers reached 56 % and 54 % of their total weight gain for Angus-cross and Limousin-cross, respectively. The four treatments were as follows: 1) Low IP, Low FP (Lo-Lo); 2) Low IP, High FP (Lo-Hi); 3) High IP, Low FP (Hi-Lo); and 4) High IP, High FP (Hi-Hi). Steers receiving the High CP during the IP had higher average daily gains (ADG) and dry matter intakes (P < 0.05) than the steers receiving Low CP. However, over the entire feeding period only dry matter intake was higher for the Hi-Hi steers (P < 0.05) compared to all other treatments. There was no difference between treatments for marbling score (P > 0.05). Steers from the Hi-Hi treatment had higher adjusted fat thickness, more kidney, pelvic and heart fat (KPH), a higher yield grade (YG), and a lower marbling to adjusted fat thickness ratio than the other treatments (P < 0.05). Steers receiving high protein at any time point during the trial had higher (P< 0.05) plasma urea nitrogen concentrations compared to steers receiving low protein. There were no differences amongst treatments for plasma glucose, insulin, ghrelin or leptin (P > 0.05). Limousin-cross steers had higher ghrelin concentrations (P < 0.05) at the end of the FP compared to the Angus-cross. In study 2, Angus steers (n = 80) were divided into four pens. The pens were randomly assigned to one of four treatments: 1) high energy diet/ no implant; 2) moderate energy diet/ no implant; 3) high energy diet/ implant; and 4) moderate energy diet/ implant. Steers that received a moderate energy (ME) diet had lower (P < 0.05) ADG than the steers on a high energy diet (HE), thus requiring more days on feed to reach similar backfat thickness (250 versus 160 d). The extended finishing period resulted in heavier end weights (P < 0.05) for the ME steers compared to the HE steers. The ME diet generated heavier carcass weights, higher KPH, and higher numerical YG (P < 0.05) than the HE diet. All other carcass characteristics were similar (P > 0.05). In conclusion, timed protein restrictions did not alter marbling; however, the steers fed the greatest amount of CP over the total period deposited proportionally the most fat into subcutaneous and internal depots relative to intramuscular depots. Feeding a ME diet to feedlot steers extended the days on feed resulting in heavier carcass weights with no influence on marbling.
Library of Congress Subject Headings
Beef cattle -- Feeding and feeds
Beef -- Quality
Adipose tissues
Format
application/pdf
Number of Pages
150
Publisher
South Dakota State University
Recommended Citation
Machado, Tanner Joseph, "Dietary Management to Influence Adipose Deposition and Beef Palatability in Finishing Steers" (2009). Electronic Theses and Dissertations. 1594.
https://openprairie.sdstate.edu/etd2/1594