Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10977173 | Journal of Dairy Science | 2012 | 10 Pages |
Abstract
The objective of this study was to characterize the mRNA expression of metabolic and proliferative genes in the rumen epithelium during ruminal acidosis. To meet our objectives, 16 rumen-fistulated, lactating Holstein dairy cattle (618 ± 35 kg of body weight, 221 ± 32 d in milk) were used in a randomized complete block design. All cattle were fed a high-forage diet (HF; 88.9% of dry matter) for 5 wk before the experiment. After the baseline week (wk 0), half of the cattle were randomly assigned and transitioned to a high-concentrate diet (HC; 62.2% of dry matter) which was fed for 3 wk (wk 1, 2, and 3). For the last 48 h of each week, continuous ruminal pH, short-chain fatty acids, and plasma β-hydroxybutyrate were assessed, followed by a rumen papillae biopsy. Milk production was higher in HC cattle compared with HF during wk 1, 2, and 3 (17.4 ± 0.5 vs. 23.4 ± 0.9 kg/d, respectively); however, the mean ruminal pH was decreased (5.75 ± 0.03 vs. 6.30 ± 0.02). The HC cattle spent more time below pH 5.6 (594 ± 54 vs. 3 ± 3 min/d) and displayed greater concentrations of ruminal butyrate (15.8 ± 0.9 vs. 10.2 ± 0.4 mmol) and plasma β-hydroxybutyrate (1,036 ± 63 vs. 778 ± 20 μM) compared with the HF cattle. The mRNA expression of genes involved in ketogenesis (HMGCS2 and PPARA) and short-chain fatty acid transport (MCT1) was unchanged by treatment. However, a downregulation in HMGCS1 (0.72 ± 0.09), one of the cholesterol biosynthesis genes, was observed in HC cattle during wk 1 of the grain challenge. In addition, the relative mRNA expression value of insulin-like growth factor-binding protein 3 was lower (0.78 ± 0.06), whereas insulin-like growth factor-binding protein 5 was higher (1.79 ± 0.15) in HC compared with HF cattle. These results suggest that grain-induced ruminal acidosis alters the mRNA expression of IGF-binding proteins and a cholesterolgenic enzyme in the rumen epithelium of lactating dairy cattle.
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Authors
M.A. Steele, L. Dionissopoulos, O. AlZahal, J. Doelman, B.W. McBride,