title: Rumen epithelial adaptation to ruminal acidosis in lactating cattle involves the coordinated expression of insulin-like growth factor-binding proteins and a cholesterolgenic enzyme.
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.
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Steele
authors.forename: L
authors.initials: L
authors.lastname: Dionissopoulos
authors.forename: O
authors.initials: O
authors.lastname: AlZahal
authors.forename: J
authors.initials: J
authors.lastname: Doelman
authors.forename: B W
authors.initials: BW
authors.lastname: McBride
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000032:analysis / Q000097:blood; D000138:Acidosis / Q000503:physiopathology / Q000662:veterinary*; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000096:biosynthesis*; D004032:Diet / Q000662:veterinary; D004848:Epithelium / Q000502:physiology; D005232:Fatty Acids, Volatile / Q000032:analysis; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D018969:Insulin-Like Growth Factor Binding Proteins / Q000096:biosynthesis / Q000502:physiology*; D007774:Lactation / Q000502:physiology; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D012417:Rumen / Q000737:chemistry / Q000502:physiology*
chemical_list: D005232:Fatty Acids, Volatile; D018969:Insulin-Like Growth Factor Binding Proteins; D002784:Cholesterol; D020155:3-Hydroxybutyric Acid