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chromic oxide, alkaline, hydrogen peroxide lignin, intake


A digestion trial involving 8 mature cows fed mature prairie hay ad libitum was conducted to determine the validity of controlled release chromic oxide (Cr) and alkaline hydrogen peroxide lignin (APL) as markers for prediction of forage intake by the fecal output (F0)/indigestibility ratio technique. Seven days after oral administration of Cr boluses, total FO was collected daily, weighed and sampled. Rectal fecal grab samples were collected at 10:00 a.m. each day and at 4-hour intervals on day 4 of collections. Mean fecal Cr output based on total fecal collections was 1,662 mg Cr/day compared to a manufacturer's suggested value of 1,505 mg Cr/day. Based on forage and fecal APL levels, mean fecal APL recovery was 95.9%. Increasing the number of days that grab samples were composited raised R2 values between actual FO and dry matter digestibility (DMD) and those predicted using fecal Cr and APL concentration (R = .56, .70, .77, .79 and .82; .27, .55, -61, .67 and .70 for 1- to 5-day composites for FO and DMD, respectively). With samples composited over the entire 5-day collection period, predicted FO, (DMD) and dry matter intake (DMI) were similar (paired t-test) to actual values. Fecal grab samples and total fecal collection samples, composited over 5 days, provided a similar relationship (R = .71) between actual and predicted DMI. Fecal Cr and APL concentrations were not affected by sampling time of day. Results from this study indicate that grab samples collected once daily and composited over 5 consecutive days can be used to predict FO when controlled release chromic oxide boluses are used. While accuracy of DMD estimations was not as high as that of FO, APL was nearly 100% recoverable and resulted in reliable predictions of DMD and DMI.

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South Dakota State University


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