Abstract
Relations between the digestibility measured by the total fecal collection method (TCD) and that measured by the index method using chromic oxide as a marker (IDD) were investigated in calves given milk-replacers by different procedures and having different incidences and per-sistences of diarrhoea. Twelve healthy Holstein male calves purchased at 1 week of age were divided into three groups of four calves each, and two groups were offered a milk-replacer containing tallow as an energy source by nipple-pail (group TN) and by open-bucket (group TB). The remainder group, SN, was given a milk-replacer containing soybean oil by nipple-pail. Compositions of the two milk-replacers were quite identical irrespective of fat sources, and both contained Cr2O3 at a level of 0.2%. Neither additional feeds nor water were available during 2-week experimental period up to 3 weeks of age. The apparent digestibilities of the constituents of the milk-replacers were measured by the total collection of feces excreted in the last 4 days of experiment and also by the index method using a part of the collected feces. In the results, the incidence and persistence of diarrhoea were highest in group SN, lowest in group TN, and intermediate in group TB. The mean fecal dry matter (DM) was significantly lower in group SN than in group TN (P<0.05). Individual variations of TCD values for all constituents (DM, crude protein, crude fat and total reducing sugars) were very limited within each group, and the mean TCD value for crude fat was significantly lower in group TB than in the other groups (P<0.05). As to IDD values, however, individual variations were larger particularly in group TB, and no significance of the difference in mean values was detected for all constituents. Correlation coe fficient (r) values between TCD and IDD were relatively low but significant except for DM when they were determined with all twelve calves used in the experiment. When r values were determined with eight calves in groups TN and SN, given different milk-replacers by nipple, correlations between TCD and IDD were highly significant for all constituents (P<0.01) irrespective of the considerable difference in persistence of diarrhoea between individual calves. However, when r values were determined with eight calves in groups TN and TB, given the same milk-replacer but by different procedures, correlations were not significant for any of the constituents irrespective of the relatively lower incidence of diarrhoea. These results suggest that the index method using Cr2O3 as a marker is highly reliable for the determination of digestibilities in sucking calves receiving milk-replacers by nipple-pail, but the reliability is reduced by increased individual variations when milk-replacers are given by bucket.
