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- Title
Duration of high-concentrate diet prior to forage finishing I: Effects on animal performance, glucose/insulin levels, carcass traits, and tissue fatty acid composition of beef steers.
- Authors
Koch, B. M.; Britt, J. L.; Koch, L. E.; Bridges, W. C.; Long, N. M.; Duckett, S. K.
- Abstract
Thirty-two Angus-influenced steers (255 ± 15.1 kg) were used to evaluate the effect of duration of exposure to a high-concentrate-based diet after weaning prior to forage finishing on performance, plasma insulin and glucose levels, carcass characteristics, and tissue fatty acid composition. Steers were randomly assigned to 1 of 4 feeding treatments: 0 d on high concentrate (CNT), 40 d on high concentrate, 80 d on high concentrate (80D), and 120 d on high concentrate (120D) followed by finishing on pasture to 485 kg. The high-concentrate diet consisted of cracked corn, corn gluten feed, chopped hay, and mineral supplement; high-quality pasture included winter annuals (ryegrass and oats), alfalfa, and nontoxic tall fescue. Weight and blood samples were collected at 21-d intervals. At 24 h postmortem, carcass characteristics and a rib section (11th-12th rib) from the left side was collected for proximal analysis and a section of subcutaneous adipose tissue collected for histology cell sizing. Due to harvesting steers at equal final BW, there was no difference for total gain or total ADG (P > 0.19); however, HCW and dressing percentage linearly increased (P < 0.031) with time on concentrate. There was no difference across treatments for rib eye area or yield grade (P > 0.11), but 12th-rib fat thickness and KPH fat quadratically and linearly increased (P < 0.015), respectively. Marbling score and total lipid of the longissimus dorsi (LM) linearly increased with time on concentrates (P < 0.001). This increase in lipid within the LM resulted in a linear decrease with increased time on concentrate for moisture (P < 0.001). Crude protein content of the LM quadratically differed (P = 0.001) and was the greatest in steers from 80D whereas 120D had the least. Within the LM, there was no difference across treatments for SFA or MUFA (P > 0.27) whereas n-6 PUFA quadratically differed (P = 0.002), being the greatest at 80D, and n-3 PUFA linearly decreased as time on concentrates increased (P < 0.001). These changes in n-6 PUFA and n-3 PUFA resulted in a linear increase of the n-6:n-3 PUFA ratio as time on concentrate increased (P < 0.001). There was no difference across treatments for plasma glucose concentration (P > 0.64), whereas there was an interaction between treatment and time for plasma insulin concentration (P = 0.012), with a quadratic difference across treatments, with the greatest levels occurring in the CNT and 120D treatments. The consumption of a high-concentrate-based diet immediately after weaning increases dressing percentage, carcass weight, and marbling deposition in cattle subsequently finished on forages.
- Subjects
FORAGE; INSULIN; BEEF cattle
- Publication
Journal of Animal Science, 2017, Vol 95, p172
- ISSN
0021-8812
- Publication type
Abstract
- DOI
10.2527/asasann.2017.349