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- Title
Duration of high-concentrate diet prior to forage finishing II: Effects on glucose and insulin levels under challenge, and gene expression of beef steers.
- Authors
Koch, B. M.; Britt, J. L.; Koch, L. E.; Bridges, W. C.; Long, N. M.; Duckett, S. K.
- Abstract
Twelve Angus-influenced steers (227 ± 10.1 kg) were used to evaluate the effect of duration of exposure to a high-concentrate-based diet after weaning prior to forage finishing on plasma insulin and glucose levels under challenge and lipogenic gene expression. 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, and 120 d on high concentrate (120D)--followed by finishing to 485 kg on pasture. The high-concentrate diet consisted of cracked corn, corn gluten feed, chopped hay, and mineral supplement, whereas high-quality pasture included winter annuals (ryegrass and oats), alfalfa, and nontoxic fescue. Weights and blood samples were collected at 21-d intervals. Muscle biopsies taken from the right longissimus dorsi (LM) when steers started the feeding period and at their respective days on treatment. Intravenous glucose tolerance tests (IVGTT) were performed at 40-d intervals until 160 d. At 24 h postmortem, carcass characteristics and a rib section (11th-12th rib) from the left side was collected for proximate analysis. There was an interaction between treatment and time for plasma glucose concentration (P = 0.03), whereas there was no interaction and no difference across treatments for plasma insulin concentration (P > 0.20). There was no difference across treatments for initial glucose concentration during IVGTT (P = 0.86) whereas adjusted area under the curve for glucose concentration linearly decreased as treatment increased (P = 0.022), with CNT and 120D being significantly different at 120 d (P = 0.008). There was no difference across treatments for initial insulin concentration during IVGTT (P = 0.46), however, 120D had a greater initial insulin concentration than CNT at 120 d (P = 0.024). Adjusted area under the curve for insulin was not different across treatments (P < 0.40). Gene expression of acetyl CoA carboxylase, stearoyl CoA desaturase, and glucose transporter 4 were not different (P > 0.21) between CNT and 120D at 120 d. Fatty acid synthase mRNA expression increased 3.2-fold (P < 0.05) for 120D compared with CNT and the ΔCT values for FASN correlated (-0.80; P < 0.017) to the quantity of de novo lipogenesis products within the LM at the time of harvest. The consumption of a high-concentrate-based diet immediately after weaning may alter insulin and glucose dynamics and lipogenic gene expression of cattle finished in a pasture-based system.
- Subjects
FORAGE; INSULIN; GENE expression; CATTLE
- Publication
Journal of Animal Science, 2017, Vol 95, p173
- ISSN
0021-8812
- Publication type
Abstract
- DOI
10.2527/asasann.2017.350