Ruminal pH and digestibility profiles during the transition period of the dairy cow
2002
Nocek, J.E. | Acan, Pas | Ueda, T. | Shinzato, I. | Sato, H. | Fujieda, T. | Suzuki, H.
Three ruminally cannulated cows calving within 10 d of each other were fitted with indwelling ruminal pH probes 3 wk prior to expected calving dates. They were used to evaluate diurnal variation in ruminal pH pre- and postpartum and to determine the influence of daily high and low pH levels on ruminal digestion of feedstuffs. Each probe was connected to a data logger, and hourly measurements were made from 3 wk prepartum through 7 wk postpartum. Cows pre- and postpartum were fed a total mixed ration (TMR) once daily. In situ digestion of corn silage, haylage, and corn meal DM was determined for 6 h prior to feeding (high pH) and then starting at 3 h and continuing through 9 h after feeding (low pH) for one week prior to expected calving date and for 1 and 3 wk postpartum. Weekly mean low pH was greater for cows during the prepartum period than during the postpartum period. There was a negative relationship between mean weekly low pH and time. Area under the curve for pH <6 and 5.5 increased from −3 to 7 wk postpartum. In situ digestion of corn silage and haycrop silage was not affected by time pre- or postpartum or by ruminal pH. Corn meal digestion at 6 h was higher at wk 1 prepartum than at wk 1 and 3 postpartum. Corn meal digestion was depressed by lower rather than higher ruminal pH. This study illustrates that there is a linear depression in ruminal pH starting 3 wk prepartum through 7 wk postpartum, suggesting that dairy cattle have a greater propensity for acidosis postpartum as intake increases. In addition, periods of low pH depressed digestibility of corn meal but not hay crop or corn silage, which suggests that energy availability may be lower.
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