Effects of starch concentration of close-up diets on rumen pH and plasma metabolite responses of dairy cows to grain challenges after calving

• Published in: Journal of dairy science 2020-12, Vol.103 (12), p.11461-11471
• Main Authors: Shi, W., Haisan, J., Inabu, Y., Sugino, T., Oba, M.
• Format: Article
• Language: English
• Subjects: Animals; Body Weight; calving transition; Cattle - metabolism; Diet - veterinary; dietary starch; Edible Grain - metabolism; Energy Metabolism - physiology; Female; grain challenge; Hordeum - metabolism; Hydrogen-Ion Concentration; Insulin - blood; Lactation - physiology; Parity; Parturition - metabolism; Pregnancy; Rumen - chemistry; Rumen - metabolism; rumen pH; Starch - administration & dosage; Triticum - metabolism
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2020-18768

The objective of this study was to evaluate the effects of starch concentration of close-up diets on plasma concentrations of energy metabolites and rumen pH of dairy cows after calving. Eighteen multiparous Holstein dairy cows (mean parity = 2.78; mean body weight = 708 kg; mean body condition score = 3.08) fitted with ruminal cannulas were assigned to treatment balanced for parity, body condition score, and expected calving date. Cows were enrolled in the study at d 28 ± 3 before the expected calving date and fed either a low-starch (LS; 14.0% starch) or high-starch (HS; 26.1% starch) diet until parturition. All cows were fed a common diet after calving (25.1% starch). A grain challenge was performed on d 7 ± 2 and 21 ± 2 after calving by dosing 6.35 kg (dry matter basis) of finely ground barley and wheat grain (1:1) into the rumen via cannula. Feeding the HS diet before calving increased the duration (369 vs. 49 min/d) and area of pH below 5.8 (85.1 vs. 5.2 pH × min/d) during d −10 to −8. In addition, even though all cows were fed a common diet after calving, HS cows tended to have longer duration (177 vs. 76 min/6 h) and greater area of pH below 5.8 (67.8 vs. 20.3 pH × min/6 h) during a grain challenge on d 7. Plasma concentration of insulin tended to be greater in cows fed the HS diet (1.40 vs. 1.09 ng/mL), whereas plasma free fatty acid concentration was not different between treatments during the grain challenge on d 7. During the grain challenge on d 21, neither rumen pH nor blood metabolites were different between the HS and LS cows. These findings suggested that feeding an HS diet during the close-up period does not mitigate rumen pH depression but may exacerbate it after calving compared with feeding an LS diet.