Variability in susceptibility to acidosis among high producing mid-lactation dairy cows is associated with rumen pH, fermentation, feed intake, sorting activity, and milk fat percentage

• Published in: Animal feed science and technology 2017-06, Vol.228, p.72-82
• Main Authors: Nasrollahi, S.M., Zali, A., Ghorbani, G.R., Moradi Shahrbabak, M., Heydari Soltan Abadi, M.
• Format: Article
• Language: English
• Subjects: Behavior; Intake; Milk production; Subacute ruminal acidosis; VFA
• ISSN: 0377-8401; 1873-2216
• DOI: 10.1016/j.anifeedsci.2017.03.007

•A substantial variation observed in acidosis susceptibility among mid-lactation dairy cows.•Tolerant cows may be characterized by greater dry matter intake and milk fat percentage.•Decreasing sorting behavior was detected for tolerant cows.•The proportion of isovalerate in the rumen was lower in tolerant cows. The objectives of the current study were to evaluate the variation in susceptibility to subacute ruminal acidosis (SARA) among high producing, mid-lactation Holstein dairy cows fed a high-grain diet and to characterize animals that are rumen pH-tolerant to high-concentrate diets. Lactating dairy cows (n=78, days in milk=103±26.5; body weight=630±76.8kg) were fed a high-concentrate diet consisting of 35% forage and 65% concentrate. Cows were adapted for 14 d and then were sampled for 10 d. Rumen pH was measured by rumenocentesis for all cows at approximately 4h after the morning feeding, and reticuloruminal pH was measured for 14 cows via indwelling sensors. Although all cows were fed the same diet, rumenocentesis pH and minimum reticuloruminal pH values ranged from 5.05 to 6.98 and 4.78–6.08, respectively, and the acidosis index ranged from 0 to 28 pH×min/kg of dry matter intake (DMI). Cows were classified according to rumenocentesis pH as tolerant (pH≥6.0; n=26), marginal (5.8≤pH