AbstractSixteen Holstein and Brown Swiss cows in late lactation were used to compare the digestibility of a complete ration containing 15-percent ground sugarcane bagasse and 85-percent concentrates to that of a control ration involving whole sugarcane silage and a standard concentrates mixture. The average amounts of dry matter consumed daily were 11.31, 2.18, and 6.26 kg. for the complete ration, the silage, and the standard concentrates, respectively. The chromic oxide indicator method with 7 days for fecal samples collection was used. The respective mean apparent digestibility coefficients determined for the complete and control rations were as follows: organic matter, 74.3 and 69.6; crude protein, 71.3 and 55.1; dry matter, 71.9 and 68.3; nitrogen-free extract, 80.7 and 76.6; ether extract, 70.0 and 67.3; crude fiber, 36.6 and 47.7; and total digestible nutrients, 72.2 and 69.2. The mean differences were highly significant (P < .01) for the first two components, significant (P < .05) for the second two components, but not significant for the final three components. With data from the control ration, on which individual cows consumed varying proportions of silage-to-concentrates, linear regression coefficients, highly significant (P < .01) for TDN and significant (P < .05) for crude protein, were obtained employing digestibility as the dependent variable and the proportion of forage dry matter to total dry matter consumed as the independent variable. When adjusted to the basis of 15-percent forage dry matter in the total dry matter consumed, the control ration yielded a mean crude protein digestibility of 69.8 percent and a mean TDN content of 73.4 percent, very similar to the corresponding figures for the complete ration. Thus, at least in crude protein and TDN, the two rations can be considered equally digestible at a common forage-to-concentrates ratio.
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