Effects of different growing diets on performance, carcass characteristics, insulin sensitivity, and accretion of intramuscular and subcutaneous adipose tissue of feedlot cattle

• Published in: Journal of animal science Vol. 87; no. 4; pp. 1540 - 1547
• Main Authors: Vasconcelos, J.T, Sawyer, J.E, Tedeschi, L.O, McCollum, F.T, Greene, L.W
• Format: Journal Article
• Language: English
• Published: Champaign, IL American Society of Animal Science 01-04-2009; Am Soc Animal Sci; Oxford University Press
• Subjects: adipose tissue; Adipose Tissue - diagnostic imaging; Adipose Tissue - growth & development; Animal Feed; Animal productions; Animals; beef cattle; Biological and medical sciences; blood chemistry; blood glucose; Body Composition - physiology; body weight; carcass characteristics; Cattle; Cattle - growth & development; Cattle - metabolism; cattle feeding; Diet; Diet - veterinary; energy intake; Factory farming; feedlots; finishing; food animals; Food industries; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; glucose tolerance; Glucose Tolerance Test - veterinary; insulin; Insulin - metabolism; insulin resistance; intramuscular fat; kinetics; Male; marbling; Meat; Meat and meat product industries; Muscular system; Random Allocation; subcutaneous fat; Subcutaneous Fat - diagnostic imaging; Subcutaneous Fat - growth & development; Terrestrial animal productions; Ultrasonography; Vertebrates; Farming animal; Adipose tissue; marbling; Meat product; Insulin; Carcass; insulin sensitivity; Vertebrata; Sensitivity; Mammalia; growing diet; Diet; Beef cattle; Livestock; Artiodactyla; Performance; Subcutaneous tissue; Ungulata; Feedlot
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2008-0934

Forty-eight individually fed crossbred steers (British and British x Continental; BW = 296 ± 16.7 kg) were used to evaluate effects of different growing diets on changes in accretion of intramuscular (IMF) and subcutaneous (SCF) adipose tissues, insulin sensitivity, and carcass traits. Dietary treatments were AL-LC (a low-corn diet fed to allow cattle ad libitum access to feed), AL-HC (a high-corn diet fed to allow cattle ad libitum access to feed), LF-HC (a limit fed high-corn diet with the energy intake equal to that provided by AL-LC), and AL-IC (a diet with approximately the midpoint daily energy intake between AL-LC and AL-HC). Steers received treatments until d 56, after which all groups were fed AL-HC until d 140. Real-time ultrasound and BW measurements were taken every 28 d, and 3 glucose tolerance tests (GTT) were conducted on d 0, 28, and 56 of the growing period to assess insulin sensitivity. Based on ultrasound IMF and SCF readings during the growing phase, AL-HC and AL-IC increased accretion of IMF (P = 0.01), and AL-LC and LF-HC diets resulted in less accretion of SCF (P < 0.01) compared with other treatments. During the finishing period, accretion of IMF (P = 0.13) and SCF (P = 0.81) did not differ among treatments, which diluted differences in overall (d 0 to 140) accretion of IMF (P = 0.28) and SCF (P = 0.52), such that final real-time ultrasound measures of IMF and SCF did not differ (P greater-than-or-equal 0.36) among treatments. Actual carcass marbling scores, however, were greater for the AL-HC and AL-IC treatments (P = 0.02), and 12th-rib fat thickness tended (P = 0.08) to be greater for AL-HC and AL-IC groups. Based on incremental area under the curve and area over the curve as indicators of insulin release and glucose uptake, respectively, no differences (P greater-than-or-equal 0.10) in insulin sensitivity were observed among treatments. Our results suggest that high-corn diets increase growing phase accretion of IMF and SCF; however, these differences were not related to differences in glucose and insulin kinetics.